Journal articles on the topic 'Peri-pubertal and pubertal heifers'
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Meyer, Grace E., Kylie P. Ewing, Lucas T. Neira, Joshua C. McCann, and Daniel W. Shike. "PSI-7 Evaluating the Relationship of Puberty Status at 10 Months of Age with Heifer Characteristics." Journal of Animal Science 100, Supplement_2 (April 12, 2022): 198–99. http://dx.doi.org/10.1093/jas/skac064.335.
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Abstract The objective was to evaluate the relationship of heifer puberty status at 10 months of age with body weight (BW), hair shedding score (HSS), and dam age. Puberty status was assessed at 10 months of age on 177 fall-born, Simmental × Angus heifers (birth date 9/26/2020 ± 18.7 d) using fabric heat patches (Estrotect; Hermitage, Tennessee) for 22 d. Patches were scored as 0, 50, or 100% activated with heifers scored 50 or 100% considered pubertal. Heifers with missing patches (n = 10) were excluded from the analysis. Heifers grazed endophyte-infected tall fescue pastures from 6 to 12 months of age. Heifers were assigned HSS at 10, 11, and 12 months of age. A HSS of 1 indicates a slick summer coat and a 5 is a full winter coat. The MIXED procedure of SAS 9.4 was used to analyze data. Heifers classified as pubertal at 10 months of age had greater (P = 0.01) birth BW than prepubertal heifers (33.1 kg vs. 30.8 kg, respectively). Heifers that were pubertal at 10 months of age also had greater (P ≤ 0.05) BW at 6, 8, 10, and 12 months of age than prepubertal heifers. Additionally, pubertal heifers had greater (P = 0.01) ADG from 6 to 12 months of age while grazing. Pubertal heifers tended (P = 0.10) to have a lesser, more desirable HSS at 10 months of age and had a lesser (P < 0.01) HSS at 11 and 12 months of age compared with prepubertal heifers. Dam age was not different (P = 0.60) between heifer puberty status at 10 months of age. In conclusion, pubertal heifers were heavier at birth, heavier from 6 to 12 months, and had more desirable HSS compared with prepubertal heifers at 10 months of age.
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King, B. D., R. N. Kirkwood, R. D. H. Cohen, G. A. Bo, C. Lulai, and R. J. Mapletoft. "Effect of zeranol implants on age at onset of puberty, fertility and embryo fetal mortality in beef heifers." Canadian Journal of Animal Science 75, no. 2 (June 1, 1995): 225–30. http://dx.doi.org/10.4141/cjas95-033.
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Thirty-three cross-bred beef heifer calves were implanted with zeranol (36 mg) at birth, 100 and 300 d of age and 40 heifer calves remained as untreated controls. Heifers were examined rectally by diagnostic ultrasonography every 14 d from 10 to 14 mo of age and then, every 21 d until the end of test (100 d after exposure to bulls). The presence of a CL, diameter of the largest follicle, total number of follicles ≥ 3 mm, diameter of the right uterine horn and age at puberty were recorded. At 15 mo heifers were exposed to bulls for 63 d. Mean (± SEM) age at onset of puberty in zeranol-implanted heifers (420 ± 8.9 d) was greater than control heifers (362 ± 6.2 d; P < 0.05). The diameter of the largest follicle was smaller (P < 0.05) in pre-pubertal zeranol-implanted heiferes than in pre-pubertal control heifers between 10 and 14 mo of age and at puberty. Within the zeranol-implanted heifers, the diameter of the largest follicle was smaller in pre-pubertal (P < 0.05) than pubertal heifers until 14 mo of age. The uterine diameter of zeranol-implaned heifers was smaller (P < 0.05) than that of control heifers during all examinations prior to breeding. Pubertal heifers had a larger (P < 0.05) uterine diameter than pre-pubertal heifers. Pregnancy rate after the first 21-d period of the breeding season and at the end of test was higher (P < 0.001) for control than for zeranol-implanted heifers (82.5 and 100%, respectively and 24 and 42.5%, respectively). Pregnancy loss in zeranol-implanted heifers was 37.5% compared with 0% for control heifers (P < 0.001). Heifers that became pregnant during the first 21 d of the breeding season had reached puberty earlier (396.9 ± 12.5 and 358.7 ± 6.4 d of age for zeranol-implanted and control heifers, respectively) than heifers not conceiving in the first 21 d (472.8 ± 10.8 d and 380.0 ± 17.7 d for zeranol-implanted and control heifers, respectively; P < 0.05). Heifers that became pregnant during the first 21 d of the breeding season had a larger (P < 0.001) uterine diameter (18.17 ± 0.21 mm) than non-pregnant heifers (16.28 ± 0.36 mm). Within the zeranol-implanted group, pregnant heifers had a larger (P < 0.05) uterine diameter (17.75 ± 0.05 mm) than non-pregnant heifers (15.78 ± 0.38 mm). Heifers that were not pregnant at the end of test began cycling later and had a numerically smaller uterine diameter than pregnant heifers (430 ± 17.5 d vs. 374.7 ± 6.2 d; and 15.1 ± 0.6 mm vs. 17.3 ± 0.24 mm, respectively), however these differences were not significant (P > 0.05). It was concluded that zeranol implants from birth delay the onset of puberty and decrease uterine horn diameter. Futhermore, the lower pregnancy rate in zeranol-implanted heiferes 100 d after exposure to bulls was caused by failure to cycle early in life, and in those that were cycling, failure to conceive and abortions between 25 and 45 d of gestation. Key words: Zeranol, bovine, puberty, fertility, uterine diameter, ultrasonography
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Ault-Seay, Taylor B., Kiernan Brandt, Madison T. Henniger, Daniel Mathew, Sarah Moorey, F. Neal Schrick, Ky G. Pohler, et al. "32 Bacterial Communities in the Uterus and Rumen of Beef Heifers Throughout Development with Protein Supplementation." Journal of Animal Science 100, Supplement_1 (March 8, 2022): 19. http://dx.doi.org/10.1093/jas/skac028.036.
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Abstract Protein supplementation to replacement heifers is utilized to reach targeted body weights, which may affect the animal’s gut and reproductive microbiomes and potentially impact breeding outcomes. The objective of the study was to evaluate the effects of protein supplementation on the ruminal and uterine bacterial communities of developing heifers. Thirty-nine pre-pubertal commercial Angus heifers were blocked by body weight (BW) and randomly assigned to one of three supplementation groups: 10% crude protein (CP), 20% CP, or 40% CP. Supplements were provided four times weekly for 140d. Blood and BW were taken every 14d to monitor development. Every 56d, uterine flushes and rumen content were collected for bacterial identification. Uterine flushes were collected via 20 mL sterile saline flushed through a Foley catheter, and rumen content by esophageal tubing. Bacterial DNA was extracted and amplified targeting the V1-V3 region of the 16S rRNA gene. Microbiome analyses were performed in R 4.1 with dada2 and phyloseq packages. Statistical analyses were performed in R and SAS 9.4. The GLIMMIX procedure was used including fixed effects of protein, month, and pubertal status. Random effects included BW, interaction of BW and protein, and heifer within the interaction, with repeated measures of month. Alpha diversity differed by month in the rumen, and by month and pubertal status in the uterus (P < 0.05). Bray Curtis analyses indicated clustering by month and pubertal status (P < 0.001) in the uterus, and by month in the rumen (P < 0.001). Multiple uterine and ruminal bacteria abundances differed over time and by protein supplementation and pubertal status (P < 0.05). The impact of pubertal status and month of development may indicate maturation of the uterine bacterial communities through development. Protein supplementation affecting the uterine bacterial communities may provide opportunity to manipulate the uterine microbiome, potentially affecting future reproductive success.
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Palmer, Elizabeth, Marcelo Vedovatto, Juliana Ranches, Rhaiza Oliveira, John Arthington, Joao Vendramini, and Philipe Moriel. "55 Effects of concentrate supplementation frequency and amount on growth and reproductive performance of Brangus heifers." Journal of Animal Science 98, Supplement_2 (November 1, 2020): 58–59. http://dx.doi.org/10.1093/jas/skz397.133.
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Abstract A 2-yr study evaluated the impacts of supplementation frequency and amount on growth and puberty attainment of Brangus heifers. On d 0 of each year, 64 Brangus heifers were stratified by BW and age (244 ± 4 kg; 311 ± 18 d) and assigned to 1 of 16 bahiagrass pastures (4 heifers/pasture). Treatments were randomly assigned to pasture (4 pastures/treatment) in a 2 × 2 factorial design and consisted of heifers offered a soybean hulls-based supplement DM at 1.25% or 1.75% of BW delivered either daily (7X) or 3 times weekly (3X; Monday, Wednesday, and Friday). On d 56, heifers were inserted with a CIDR device for 14 d, followed by administration of PGF2α and a timed-AI+GnRH protocol on d 89. Heifers were exposed to bulls from d 89 to 167. Data were analyzed using the SAS GLIMMIX procedure. No rate × frequency interactions were detected (P ≥ 0.20). Overall ADG was greater for 7X vs. 3X heifers (P = 0.007). Daily supplementation increased (P ≤ 0.03) the percentage of pubertal heifers prior to CIDR insertion and at AI compared to 3X supplementation; however, percentage of pregnant heifers did not differ (P = 0.70). Supplementation at 1.25% vs. 1.75% enhanced the overall ADG (P = 0.02) but did not impact (P = 0.18) the percentage of pubertal heifers before CIDR insertion. After the puberty induction protocol, heifers supplemented at 1.75% of BW achieved greater puberty attainment at time of AI (P = 0.05) and final pregnancy rates (P = 0.02) than heifers supplemented at 1.25% of BW. When a puberty induction protocol was included, the percentage of pregnant Brangus heifers were not affected by supplementation frequency (daily vs. 3 times weekly) but enhanced when the supplement dry matter amount was offered at 1.75 vs. 1.25% of body weight.
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Baggio, Marcelo, José Paulo P. R. Barroso, Leticia Carolina Bortolanza Soares, Josiane F. Lages, Joel G. Oliveira Junior, Mariana Jeronymo, Natasha B. Petrenko, Evandro Maia M. Ferreira, and Alexandre Vaz Pires. "PSV-B-18 Effect of Puberty Induction on Embryonic Loss in Precocious Nellore Heifers." Journal of Animal Science 100, Supplement_3 (September 21, 2022): 345–46. http://dx.doi.org/10.1093/jas/skac247.632.
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Abstract This study aimed to determine if heifers induced to puberty had damage in reproductive performance compared with heifers that reach puberty naturally. Nellore heifers (n = 210) were weaned at 8 ± 0.7 mo of age were assigned to 42 feedlot pens according to BW (184 ± 1 kg). The diet was compounded by Tifton-85 haylage (18% CP; 55% TDN) ad libitum and supplement (4g/kg of BW; 25% CP; 60% TDN). Puberty and growth were assessed weekly. At 14 mo of age, 46 heifers reached puberty naturally (precocious heifers; PH) and 164 non-pubertal heifers were submitted to puberty induction with progesterone (P4) insert for 10 days and estradiol cypionate (0.5 mg) at P4 removal (puberty induction; PI). After fourteen days, all heifers were submitted to TAI. Heifers were considered pregnant at 20 days (P20) after AI when CL had blood flow < 25% of area (Power-Doppler). Pregnancy rate was also determined at 30 (P30) and 60 (P60) days after AI by embryo detection. Early (P20 – P30) and late (P30 – P60) embryonic loss were determined. Reproductive data were analyzed by GLIMMIX, and BW was analyzed using repeated measures over time (MIXED; SAS 9.3). The PH was heavier than PI from 8 to 16 mo of age, which BW was 296 and 285 ± 3 kg at 14 mo of age, respectively. At beginning of TAI, 88% of PI heifers had a CL. Pregnancy rate was similar (P > 0.05) between treatments, in which pregnancy rate at 20, 30 or 60 days after AI was 65, 47 and 43% for PH and 61, 53 and 48% for PI, respectively. Early (26 vs 14%) and late (9 vs 9%) embryonic loss were similar (P > 0.05) in PH and PI, respectively. In summary, natural or induced pubertal heifers had similar reproductive performance.
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Tahir, Muhammad S., Loan T. Nguyen, Benjamin L. Schulz, Gry A. Boe-Hansen, Milton G. Thomas, Stephen S. Moore, Li Yieng Lau, and Marina R. S. Fortes. "Proteomics Recapitulates Ovarian Proteins Relevant to Puberty and Fertility in Brahman Heifers (Bos indicus L.)." Genes 10, no. 11 (November 12, 2019): 923. http://dx.doi.org/10.3390/genes10110923.
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High fertility and early puberty in Bos indicus heifers are desirable and genetically correlated traits in beef production. The hypothalamus–pituitary–ovarian (HPO) axis synthesizes steroid hormones, which contribute to the shift from the pre-pubertal state into the post-pubertal state and influence subsequent fertility. Understanding variations in abundance of proteins that govern steroid synthesis and ovarian signaling pathways remains crucial to understanding puberty and fertility. We used whole ovaries of six pre-pubertal and six post-pubertal Brahman heifers to conduct differential abundance analyses of protein profiles between the two physiological states. Extracted proteins were digested into peptides followed by identification and quantification with massspectrometry (MS) by sequential window acquisition of all instances of theoretical fragment ion mass spectrometry (SWATH-MS). MS and statistical analysis identified 566 significantly differentially abundant (DA) proteins (adjusted p < 0.05), which were then analyzed for gene ontology and pathway enrichment. Our data indicated an up-regulation of steroidogenic proteins contributing to progesterone synthesis at luteal phase post-puberty. Proteins related to progesterone signaling, TGF-β, retinoic acid, extracellular matrix, cytoskeleton, and pleiotrophin signaling were DA in this study. The DA proteins probably relate to the formation and function of the corpus luteum, which is only present after ovulation, post-puberty. Some DA proteins might also be related to granulosa cells signaling, which regulates oocyte maturation or arrest in ovaries prior to ovulation. Ten DA proteins were coded by genes previously associated with reproductive traits according to the animal quantitative trait loci (QTL) database. In conclusion, the DA proteins and their pathways were related to ovarian activity in Bos indicus cattle. The genes that code for these proteins may explain some known QTLs and could be targeted in future genetic studies.
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Cushman, Robert A., Alexandria Snider, and Matthew S. Crouse. "281 Can We Developmentally Program the Epigenome to Improve Traits Relevant to Production in Cattle?" Journal of Animal Science 99, Supplement_1 (May 1, 2021): 20. http://dx.doi.org/10.1093/jas/skab054.035.
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Abstract While sequence variation can be informative to associate regions of the genome with specific traits and improve genetic selection, the epigenome may provide a more powerful tool to manage cattle. Identifying practices that are producer friendly and effectively control epigenetic function within animals is crucial to translating developmental programming to a production setting. Initial studies of developmental programming investigated how environmental or nutritional stresses during fetal and peri-natal development impacted performance of animals later in life. These studies demonstrated changes in methylation, alterations in transcript abundance, and negative impacts on physiology, but they also suggested that we may be able to beneficially impact the epigenome and developmentally program animals to excel in their niche in the production system. Maternal nutritional status during the third trimester influenced date of conception of female progeny in several studies but failed to do so in other studies. Transcriptomic analyses provided evidence that nutritional treatments alter mRNA abundance in brain, liver, muscle, and ovary, but does not conclusively demonstrate that this is due to functional changes in the epigenome. If developmental programming is to be applied in production systems, responses must be consistent and beneficial. Reducing nutrient intake in heifers during peri-pubertal development increased number of primordial follicles in the ovaries and reproductive longevity. While nutritional programming of the ovarian reserve in peri-pubertal heifers appears to occur consistently across locations and studies, it does not ensure that subsequent environmental stressors will not induce changes in the ovarian reserve that will negate beneficial effects. These studies demonstrate that it is possible to developmentally program the epigenome in cattle in ways that will improve production traits; however, there remains a need for studies to improve the consistency of response and to determine best practices that fit into production systems. USDA is an equal opportunity provider and employer.
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Sirard, Marc Andre A. "163 DNA Methylation Across Generation in Bovine." Journal of Animal Science 99, Supplement_3 (October 8, 2021): 86–87. http://dx.doi.org/10.1093/jas/skab235.155.
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Abstract Scientists are starting to realize that some effects from the animal environment may affect their progeny’s phenotype. These epidemiological evidences of early life programming are very well described in humans and rodents but less documented in bovines, especially in relation to the peri-conceptual period. In fact, as other species the bovine gametes may carry non-genetic information that will impact the survival, the fitness and the phenotype of the embryo-fetus-offspring. Using a peri-pubertal age model we have compared the semen of bulls that we obtained at different ages just after puberty for whole genome DNA methylation, miRNA content and open DNA access regions to identify mechanistic relation to gene expression and DNA methylation in embryos created with the same bulls compared to themselves and mated by IVF to the same heifer several times. A similar experiment was also done with pre-peri and post puber heifers using the same adult bull for repetitive IVF. The overall results indicate that the same pathways are affected in embryos from immature parents. The targeted processes are overwhelmingly associated with cellular metabolism involving mitochondria function and the mTOR pathways amongst others. A very similar conclusion was also observed with embryos obtained from adult mothers under negative energy balance and the resulting calves obtained by surrogate gestations using blood DNA methylation to assess the intergenerational legacy. These results support a metabolic programming across generation associated with an energy deficient status of the parent.
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Vincent, Isobel C., R. Hill, and H. Ll Williams. "Rapeseed meal in the diet of pubertal heifers during early pregnancy." Animal Science 47, no. 1 (August 1988): 39–44. http://dx.doi.org/10.1017/s0003356100037028.
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AbstractThe response of Hereford × Friesian heifers to large intakes of two types of high glucosinolate rapeseed meal were studied during two 5-month periods in consecutive years. In year 1, six heifers were given a compound concentrate food containing 250 g/kg extracted rapeseed meal and six control animals were given concentrate containing 210 g/kg soya-bean meal. In year 2, a further six heifers were given concentrate containing 320 g/kg expeller rapeseed meal and six control animals were given the same soya-bean meal compound concentrate. The crude protein (CP): metabolizable energy (ME) ratio of all diets was 14·3 g CP per MJ ME. Barley straw was the only roughage offered.There were no differences between groups in ovarian activity assessed from plasma progesterone concentrations, nor in behavioural activity around oestrus. The heifers were slaughtered 6 weeks after artificial insemination. Pregnancy rate was proportionally 0·58 (7/12) in the rape-fed and 0·67 (8/12) in the control heifers (P > 0·05). Foetuses from heifers given rapeseed meal were slightly smaller than those from control heifers; the difference was significant in year 2 (P < 0·05).Thyroid glands of heifers given rapeseed meal showed histological evidence of goitrogenicity but weights of the glands did not reflect this. Plasma thyroxine values were depressed in heifers given rapeseed meal (year 1, P < 0·001; year 2, P < 0·05). Plasma thiocyanate was elevated in rapeseed meal heifers in both years (P < 0·001) compared with values for control animals.
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Prajapati, Gorakh, and N. Laxmi. "Plasma Nesfatin-1 and Leptin in pubertal and non-pubertal Murrah buffalo heifers (Bubalus bubalis)." Journal of Advanced Veterinary and Animal Research 2, no. 4 (2015): 396. http://dx.doi.org/10.5455/javar.2015.b107.
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Purup, S., M. Vestergaard, M. S. Weber, K. Plaut, R. M. Akers, and K. Sejrsen. "Local regulation of pubertal mammary growth in heifers." Journal of Animal Science 78, suppl_3 (2000): 36. http://dx.doi.org/10.2527/2000.78suppl_336x.
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Seneda, M. M., F. Morotti, A. F. Zangirolamo, N. C. da Silva, T. K. Sanches, W. Blaschi, and T. R. R. Barreiros. "Antral follicle population in prepubertal and pubertal heifers." Reproduction, Fertility and Development 31, no. 1 (2019): 10. http://dx.doi.org/10.1071/rd18344.
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The antral follicle count (AFC) is an important tool in the selection of bovine females destined for biotechnology. However, little is known about AFC in prepubertal and pubertal heifers. Some challenges inherent to the physiology of young females must be considered to achieve efficient rates with different procedures, such as ovum pick-up and IVF. This paper covers some important topics about ovarian physiology related to the population of antral follicles and reproductive efficiency in young female cattle.
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Ko, Byung-Hoon, Dong-Gun Park, and Won-Jae Lee. "Postoperative Observation of Spaying with the Silicon Ring on the Ovaries in Heifers: A Retrospective Study in 28 Cases." Veterinary Sciences 9, no. 11 (November 21, 2022): 643. http://dx.doi.org/10.3390/vetsci9110643.
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Although spaying prepubertal heifers has routinely been conducted to control cattle herd and improve meat quality, understandings of the postoperative changes following new spaying methods with the silicon ring on the ovaries via colpotomy remain limited. Therefore, as a retrospective study, 28 cases of spayed heifers were reviewed for postoperative changes after employing this method, with inclusion criteria including complete medical records for clinical observation, ultrasonography, measuring reproductive hormones, and tracking slaughter records. No mortality and heat signs at the pubertal age postoperatively occurred in spayed animals. On ultrasonography during rectal examination, the ovaries were enlarged without any folliculogenesis from one week, while massive ovarian edema appeared from two weeks, and ovaries were no longer palpable at four weeks post-surgery. In hormones, whereas estrogen and progesterone levels did not change from prepubertal to pubertal age in spayed animals, luteinizing hormone levels progressively increased during this period and reached a higher level at pubertal period than unspayed controls. Although carcass weight and yield were similar between groups upon slaughter at pubertal age, the spayed animals presented higher carcass quality (marbling degree) than that of controls. These results may contribute to develop herd management strategies, including control of estrus in cattle.
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Moriel, Philipe, Bruno Ieda Cappellozza, Matheus B. Piccolo, Reinaldo F. Cooke, Miguel F. Miranda, Luis F. D. Batista, Rafael S. Carvalho, et al. "Pre- and post-weaning injections of bovine somatotropin to optimize puberty achievement of Bos indicus beef heifers1." Translational Animal Science 3, no. 1 (November 19, 2018): 443–55. http://dx.doi.org/10.1093/tas/txy125.
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Abstract The present study evaluated the growth and puberty attainment of Bos indicus heifers administered recombinant bovine somatotropin (bST) or saline injections during preweaning and/or postweaning. On day 0, 177 suckling Nellore heifers were stratified by initial age and body weight (BW) (80 ± 10 d; 97 ± 16 kg), and randomly assigned, in a 2 × 2 factorial design (n = 44 to 45 heifers/treatment), to receive s.c. injections of saline (5 mL 0.9% NaCl) or sometribove zinc (Posilac; Elanco, Greenfield, IN; 6.14 mg/kg of BW0.75) on days 0 and 10 (PRE) and/or days 167 and 177 (POS). All heifers were managed as a single group in Brachiaria decumbens pastures from day 0 until 24 d postweaning (day 191), and then provided a corn silage–based TMR from days 191 to 380 to achieve 65% to 70% of mature BW at the end of the study (day 380). Heifer full BW was collected on days 0, 10, 167, 177, and monthly from days 191 to 380. Transrectal ultrasonography of ovaries was performed on days 1 and 10 of each month from days 229 to 380 to assess the percentage of pubertal heifers. Liver biopsies and blood samples from jugular vein were collected on days 0, 10, 167, 177, and 380. Additional blood samples were collected monthly from days 259 to 380 (n = 10 to 15 heifers/treatment). No interactions among day of the study, PRE, and POS injections of saline or bST were detected (P ≥ 0.11). Preweaning bST injections increased heifer average daily gain (ADG) from days 0 to 10 and plasma IGF-1 on day 10 (P ≤ 0.03), did not affect ADG from days 0 to 177, plasma IGF-1 from days 259 to 380, and any liver gene mRNA expression (P ≥ 0.19), but tended to decrease ADG from days 191 to 380 (P = 0.07) and percentage of pubertal heifers on days 349 (P = 0.07), 359 (P = 0.002), and 380 (P = 0.0001) compared with saline injections. Postweaning bST injections increased plasma IGF-1 on day 177 and overall liver mRNA expression of GHR-1A (P ≤ 0.05), decreased plasma IGF-1 from days 259 to 380 (P = 0.03), tended to decrease liver mRNA expression of GHR-1B on day 177 (P = 0.08), but did not affect ADG from days 167 to 177 and 191 to 380, and puberty attainment from days 229 to 380 (P ≥ 0.12) compared with saline injections. Thus, preweaning and postweaning injections of bST successfully increased heifer plasma IGF-1 concentrations 10 d after first injection. Postweaning injections of bST had no impact on puberty attainment, whereas preweaning bST injections of bST impaired puberty attainment of Nellore beef heifers.
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CHOUDHARY, SANJAY, M. L. KAMBOJ, NITIN RAHEJA, NISHANT KUMAR, MAYAMITTA SAINI, and S. S. LATHWAL. "Influence of bull biostimulation on age at puberty and reproductive performance of Sahiwal heifers." Indian Journal of Animal Sciences 90, no. 1 (February 18, 2020): 28–34. http://dx.doi.org/10.56093/ijans.v90i1.98172.
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Present study was undertaken to compare the effect of biostimulation by exposing the heifers to fenceline bull contact and fenceline + direct contact on age at puberty and reproductive performance of Sahiwal heifers. Pre-pubertal heifers (24) were allotted to 3 groups (8 animals each), i.e. non-bull exposed (NBE), fenceline bull exposed (FBE) and FBE + direct bull exposed (DBE) on the basis of age and body weight. In NBE group, heifers were not exposed to bull; in FBE group, heifers were exposed to the bull through a fenceline contact (24 h) and in FBE+DBE group, heifers were housed in a fenceline contact (24 h) with bull along with direct contact for 6 h through another bull in the heifer shed. Heifers were considered to have attained puberty if progesterone concentration was >1 ng/ml. The mean age and body weight at puberty in FBE (19.33±0.36 months and 226.20±6.35 kg) and FBE+DBE (19.11±0.58 months and 224.19±4.54 kg) heifers were almost similar but significantly lower than NBE heifers (24.13±0.16 months and 262.50±8.50 kg). The average age at first service and first calving was similar in FBE (20.41±0.45 and 30.20±0.73 months) and FBE+DBE (20.78±0.36 and 29.90±0.44 months) heifers but significantly lower than NBE heifers (25.15±0.14 and 34.29±0.53 months). We conclude that biostimulation of heifers by fenceline contact with the bull is as effective as FBE + 6 h of daily direct bull contact in hastening the age at puberty and improving reproductive performance.
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Carson, A. F., A. R. G. Wylie, J. D. G. McEvoy, M. McCoy, and L. E. R. Dawson. "The effects of plane of nutrition and diet type on metabolic hormone concentrations, growth and milk production in high genetic merit dairy herd replacements." Animal Science 70, no. 2 (April 2000): 349–62. http://dx.doi.org/10.1017/s1357729800054813.
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AbstractSeventy high genetic merit Holstein heifers were used in two experiments to investigate (1) the effects of plane of nutrition and diet type during the pre-pubertal period and (2) the effects of plane of nutrition during the post-pubertal period on metabolic hormone concentrations, growth and milk production. In experiment 1, treatment 1 and 2 heifers were given food to achieve a live-weight gain of 0·70 and 0·95 kg/day from 3 to 10 months of age on a grass silage based diet, while treatment 3 heifers were given food to achieve 0·95 kg/day on a barley straw/concentrate diet. During the pre-pubertal period, heifers reared on treatment 1 had significantly higher growth hormone(GH) concentrations (ng/ml per 1 h) than heifers reared on treatment 2 (P < 0·01) and had significantly lower insulin concentrations than heifers reared on treatment 3 (P < 0·01). Heifers reared on treatment 1 had significantly lower insulin-like growth factor 1 (IGF-1) concentrations than those reared on treatment 3 (P < 0·01). At 10 months of age heifers reared on treatment 1 were of lower condition score (P < 0·01) than those on treatment 2 and had a smaller heart girth diameter (P < 0·01) than those on treatments 2 and 3. During the first lactation, milk yield and composition produced by the heifers was not significantly affected by treatment. In experiment 2, treatment A heifers were given, from 14 to 24 months of age, a low plane of nutrition to allow a live-weight gain of 0·65 kg/day on a grass silage and grass based diet during the winter and summer periods respectively. Treatment B heifers were kept on a high plane of nutrition to allow a live-weight gain of 0·90 kg/day on the same forage along with concentrate supplementation. During the rearing period, GH and IGF-1 concentrations were not significantly affected by treatment. Treatment A heifers weighed less before calving (P < 0·05), had a lower condition score (P < 0·01), and had a smaller heart girth diameter (P < 0·01) than those on treatment B. During the first 10 weeks of lactation, heifers on treatment A had a higher silage dry matter intake and lost less weight (P < 0·05) than those on treatment B, however, by 20 weeks of lactation these effects had disappeared. Milk yield and composition during the first lactation were not significantly affected by treatment. Overall, the findings of experiments 1 and 2 did not show any beneficial effects of higher weights at first calving in high genetic merit Holsteins and therefore indicate that accelerated growth in the pre- or post-pubertal period may not be required.
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Carson, A. F., F. J. Gordon, A. R. G. Wylie, and J. E. McEvoy. "The effects of plane of nutrition and diet type on lactogenic hormone levels, growth and milk production in high genetic merit dairy heifers." Proceedings of the British Society of Animal Science 1998 (1998): 198. http://dx.doi.org/10.1017/s1752756200598500.
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To develop appropriate rearing regimes for high genetic merit dairy heifers, information is required on the effect of growth rates and diet type within the various stages of die animal’s life on performance. The aims of this study were to investigate (1) the effects of plane of nutrition and diet type during the pre-pubertal period on lactogenic hormone levels and (2) the effects of plane of nutrition during die post-pubertal period on lactogenic hormone levels, growth and milk production.
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Carson, A. F., F. J. Gordon, A. R. G. Wylie, and J. E. McEvoy. "The effects of plane of nutrition and diet type on lactogenic hormone levels, growth and milk production in high genetic merit dairy heifers." Proceedings of the British Society of Animal Science 1998 (1998): 198. http://dx.doi.org/10.1017/s0308229600034115.
Full textAbstract:
To develop appropriate rearing regimes for high genetic merit dairy heifers, information is required on the effect of growth rates and diet type within the various stages of die animal’s life on performance. The aims of this study were to investigate (1) the effects of plane of nutrition and diet type during the pre-pubertal period on lactogenic hormone levels and (2) the effects of plane of nutrition during die post-pubertal period on lactogenic hormone levels, growth and milk production.
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Mäntysaari, Päivi. "Predicting body weight from body measurements of pre-pubertal Ayrshire heifers." Agricultural and Food Science 5, no. 1 (January 1, 1996): 17–23. http://dx.doi.org/10.23986/afsci.72727.
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The relationship between heart girth, wither height, body length and body weight in 3- to 9.5-month-old pre-pubertal Finnish Ayrshire heifers gaining 600-650 g/d was analysed (experiment I). Regression analysis showed that heart girth was the trait most highly correlated to body weight (R2 = 0.969). Including body length or wither height as a second term in the regression, increased R2 values only slightly. When the relationship between heart girth and body weight was used to predict the body weight of heifers reared at two feeding levels (experiment II), the precision of prediction was affected by the plane of nutrition. Actual body weight for a given heart girth was slightly higher on the high than on the low feeding level. It is, nevertheless, concluded that the equations presented in the paper can be used to estimate accurately the body weight of pre-pubertal (95-140-cm heart girth) Ayrshire heifers gaining 550-700 g/d.
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Morris, C. A., R. L. Baker, and N. G. Cullen. "Genetic correlations between pubertal traits in bulls and heifers." Livestock Production Science 31, no. 3-4 (June 1992): 221–34. http://dx.doi.org/10.1016/0301-6226(92)90019-z.
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Landry, David A., Lia Rossi-Perazza, Simon Lafontaine, and Marc-André Sirard. "Expression of atresia biomarkers in granulosa cells after ovarian stimulation in heifers." Reproduction 156, no. 3 (September 2018): 239–48. http://dx.doi.org/10.1530/rep-18-0186.
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The use of younger gamete donors in dairy cattle genetic selection programs significantly accelerates genetic gains by decreasing the interval between generations. Ovarian stimulation (OS) and the practice of follicle-stimulating hormone (FSH) withdrawal, also known as coasting, are intensively used in pre-pubertal heifers without detrimental effects on subsequent reproductive performance but generally with lower embryo yields. However, recent data from embryo transfer programs showed similar embryo yields in younger and sexually mature animals but with a significant difference in the coasting period. The aim of the present study was to identify a set of granulosa cell biomarkers capable of distinguishing optimal follicle differentiation from late differentiation and atresia in order to assess the differences in coasting dynamics between pre- and post-pubertal donors. We integrated transcriptomic data sets from a public depository and used vote counting meta-analysis in order to elucidate the molecular changes occurring in granulosa cells during late follicle differentiation and atresia. The meta-analysis revealed the gene expression associated with follicle demise, and most importantly, identified potential biomarkers of that status in bovine granulosa cells. The comparison of the expression of six biomarkers between pre- and post-pubertal donors revealed that younger donors had more signs of atresia after the same period of coasting. We found different follicular dynamics following coasting in younger donors. It is possible that younger donors are less capable to sustain follicular survival most likely due to insufficient luteinizing hormone signaling. In summary, the pre-pubertal status influences follicular dynamics and reduces the oocyte developmental competence curve following OS and FSH withdrawal in heifers.
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EJ, Cuadra. "Effects of Injecting GnRH 48 Hours after PGF2α on the Dynamic Follicular and Luteal Endocrine Cells in Post - Pubertal Holstein Heifers." Open Access Journal of Veterinary Science & Research 4, no. 3 (2019): 1–5. http://dx.doi.org/10.23880/oajvsr-16000186.
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Eighteen cycling Holstein heifers were allotted at random by weight and body condition score to one of two treatments to evaluate the effects of GnRH on luteal response when injected 48 hours (h) after the first injection in a 10 day interval between two i njections of PGF2α . Heifers in the control group (n=9) received an injection of saline 48 h after the first injection of PGF2α; however, heifers in the μg) 48treatmenthafter group n=9) received an injection of GnRH (100 the first injection of PGF2α. Heife rs were checked for estrus 3 times daily for 60 minutes each time. Blood samples were collected for analysis of progesterone on d ays 0 (first injection of PGF2α), 2 (48 h after the fi rst injection), 10 ( at the second injection of PGF2) and at day 17 (7 days a fte r the second injection of PGF2α ). Plasma samples were analyzed fo r concentration of progesterone via radioimmunoassay to evaluate luteal cell function. Concentrations of progesterone did not differ between the control heifers and treatment animals at any day of the study. However, heifers treated with GnRH showed a significant decline in concentration of progesterone from day 0 to day 2 in a luteal response to the injection; nevertheless, concentrations of progesterone increased significantly from day 2 t o day 10. Thus, this data demonstrated that injecting GnRH 48 h after PGF2α either speeds up formation of new corpus luteum or prevents full regression of the corpus luteum present prior to the first injection of PGF2α.
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Fortes, M. R. S., S. A. Lehnert, S. Bolormaa, C. Reich, G. Fordyce, N. J. Corbet, V. Whan, R. J. Hawken, and A. Reverter. "Finding genes for economically important traits: Brahman cattle puberty." Animal Production Science 52, no. 3 (2012): 143. http://dx.doi.org/10.1071/an11165.
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Age at puberty is an important component of reproductive performance in beef cattle production systems. Brahman cattle are typically late-pubertal relative to Bos taurus cattle and so it is of economic relevance to select for early age at puberty. To assist selection and elucidate the genes underlying puberty, we performed a genome-wide association study (GWAS) using the BovineSNP50 chip (~54 000 polymorphisms) in Brahman bulls (n = 1105) and heifers (n = 843) and where the heifers were previously analysed in a different study. In a new attempt to generate unbiased estimates of single-nucleotide polymorphism (SNP) effects and proportion of variance explained by each SNP, the available data were halved on the basis of year and month of birth into a calibration and validation set. The traits that defined age at puberty were, in heifers, the age at which the first corpus luteum was detected (AGECL, h2 = 0.56 ± 0.11) and in bulls, the age at a scrotal circumference of 26 cm (AGE26, h2 = 0.78 ± 0.10). At puberty, heifers were on average older (751 ± 142 days) than bulls (555 ± 101 days), but AGECL and AGE26 were genetically correlated (r = 0.20 ± 0.10). There were 134 SNPs associated with AGECL and 146 SNPs associated with AGE26 (P < 0.0001). From these SNPs, 32 (~22%) were associated (P < 0.0001) with both traits. These top 32 SNPs were all located on Chromosome BTA 14, between 21.95 Mb and 28.4 Mb. These results suggest that the genes located in that region of BTA 14 play a role in pubertal development in Brahman cattle. There are many annotated genes underlying this region of BTA 14 and these are the subject of current research. Further, we identified a region on Chromosome X where markers were associated (P < 1.00E–8) with AGE26, but not with AGECL. Information about specific genes and markers add value to our understanding of puberty and potentially contribute to genomic selection. Therefore, identifying these genes contributing to genetic variation in AGECL and AGE26 can assist with the selection for early onset of puberty.
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Kramarenko, Alexander S., Halyna I. Kalynycnenko, Ruslan L. Susol, Nataliia S. Papakina, and Sergei S. Kramarenko. "Principal Component Analysis of Body Weight Traits and Subsequent Milk Production in Red Steppe Breed Heifers." Proceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences. 76, no. 2 (April 1, 2022): 307–13. http://dx.doi.org/10.2478/prolas-2022-0044.
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Abstract The main goal of this study was to determine the effects of body weight traits during the rearing period on subsequent milk production of primiparous dairy cows using Principal Component Analysis. Data on lactation performance records of 109 Red Steppe dairy cow progeny of six bulls maintained at the State Enterprise “Pedigree Reproducers” Stepove”” (Mykolayiv region, Ukraine), during 2001–2014, were utilised for the present study. Heifer body weight at birth, 3, 6, 9, 12, 15, and 18 months of age was measured. Records of 305-day milk yield (kg), milk fat percentage (%), milk fat yield (kg), monthly milk yield (kg) and milk fat percentage (%) in the 1st-lactation dairy cows were also available. Principal Components Analysis (PCA) was conducted on the live weights for each heifer between birth and 18 months of age. The first three principal components (PC1-PC3) explained 79.7% of the total variance. Principal component 1 (PC1) showed significant relationship to body weight of heifers at 9, 12, and 15 months of age (post-pubertal period). Body weight at 3 and 6 months of age (pre-pubertal period) had higher scores on the second principal component (PC2). Principal component 3 (PC3) showed significant relationship to body weight of calves at birth. Only groups of heifers with high scores on PC1 and PC2 had significant effect on subsequent milk performance (with the exception of milk fat percentage). Thus, the use of a multivariate technique (Principal Component Analysis) allowed to determine two age intervals of heifers during the rearing period (pre- and postpubertal periods), which were significantly related to subsequent milk production.
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Oliveira Junior, Jair Sábio de, George Moreira da Silva, Elizângela Mirian Moreira, Vanessa Rachele Ribeiro Nunes, Fábio Morotti, Evelyn Rabelo Andrade, Marcelo Marcondes Seneda, and Luiz Francisco Machado Pfeifer. "Low versus high antral follicle count on the fertility of timed AI Nelore heifers." Brazilian Journal of Veterinary Research and Animal Science 59 (December 6, 2022): e190164. http://dx.doi.org/10.11606/issn.1678-4456.bjvras.2022.190164.
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This study aimed to determine the effect of antral follicle count (AFC), and pubertal status on the fertility of beef heifers. In this study, 230 Nelore heifers, 20±2 months of age, were subjected to an estradiol progesterone-based timed artificial insemination (TAI) program. On Day 0 of the TAI protocol, the heifers were examined by transrectal ultrasound to record videos of the ovaries. Later, in the darkroom of the laboratory of images, the videos were analyzed for AFC (≥ 3 mm) of each ovary. Females who failed the first TAI were resynchronized with the same hormonal protocol. The pregnancy status was evaluated by ultrasonography 30 days after each FTAI. The general mean of the AFC was 22.0 follicles. Thus, the heifers were divided into 2 groups according to AFC: Low AFC (˂ 22 follicles, n = 114), and High AFC (≥ 22 follicles, n = 116). No differences (P > 0.05) in the pregnancy per AI (P/AI) were observed between the Low and High AFC groups, and between pubertal and prepubertal categories. The P/AI was not different between heifers that displayed or did not estrus (P = 0.2). However, considering the estrus response of each AFC group, High AFC heifers that displayed estrus had greater P/AI (P = 0.01) than High AFC heifers that did not display estrus. In summary, AFC and pubertalstatus did not affect the fertility of Nelore heifers. In contrast, the P/AI of heifers that did not display estrus was lower than heifers observed in estrus only in the High AFC group.
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Severino-Lendechy, Víctor Hugo, Felipe Montiel-Palacios, and Ponciano Pérez-Hernández. "Age and weight at puberty in tropical dairy criollo heifers with and without supplementary feeding." Ecosistemas y Recursos Agropecuarios 4, no. 12 (September 2, 2017): 555. http://dx.doi.org/10.19136/era.a4n12.1195.
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The e ect of supplementary feeding on age and weight at puberty was evaluated in 79 pre-pubertal Tropical Dairy Criollo (TDC) heifers of 8 and 10 months of age, distributed in four treatments: T1 and T2) 8 month old heifers with and without supplementary feeding (WSF, n= 20) and (NSF, n= 20), respectively; T3 and T4) 10 month old heifers (WSF, n= 20) and (NSF, n= 19). Average age and weight at puberty in T2 and T4 was 20.4 ± 0.5 months and 287.2 ± 5.9 kg compared with 17.5 ± 0.6 months and 296.8 ± 7.8 kg in T1 and T3 (p < 0.05). The number, follicular diameter (mm) and concentration of progesterone (ng mL−1) in blood was higher (p < 0.05) in T1 and T3 compared to T2 and T4. Supplementary feeding decreases the age at puberty, increases weight gain, improves follicular development and increases blood progesterone concentration in TDC females.
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Chase, C. C., R. A. Cushman, A. K. McNeel, O. L. Amundson, G. A. Perry, S. C. Tenley, J. R. Wood, A. S. Cupp, J. L. Vallet, and J. R. Miles. "181 IN VITRO FERTILIZATION (IVF) USING SEMI-DEFINED CULTURE CONDITIONS FROM LOW OR HIGH ANTRAL FOLLICLE COUNT PUBERTAL BEEF HEIFERS." Reproduction, Fertility and Development 28, no. 2 (2016): 221. http://dx.doi.org/10.1071/rdv28n2ab181.
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To compare the in vitro fertilization (IVF) and production (IVP) of embryos from low and high antral follicle count (AFC) heifers, AFC were determined on 106 heifers using transrectal ultrasonography. Ten heifers with the lowest AFC (avg. 13.2) and 10 heifers with the highest AFC (avg. 27.4) with evidence of oestrous cyclicity were synchronised with 2 injections of prostaglandin F2α (PGF2α); half were harvested on Days 5 to 6 and half on Days 15 to 16 of the oestrous cycle. The IVF procedures included protocols for semi-defined media and were as described (IVP Protocol, P. J. Hansen’s Laboratory, University of Florida, Gainesville, FL, USA). Cumulus-oocyte complexes (COC) from follicles less than 8 mm in diameter were cultured in maturation medium (5% CO2; 38.5°C) for 24 h. Matured COC were fertilised using thawed frozen semen from a crossbred bull that was purified using Percoll gradient separation procedures. Motile spermatozoa were added to COC in fertilization medium at a final concentration of 1 × 106 spermatozoa per mL. About 24 h later, presumptive zygotes were placed in microdrops of development medium under oil, and cultured (5% CO2, 5% O2, balance N2, 38.5°C). On Days 3 and 8 after fertilization, cleavage and blastocyst development rates, respectively, were assessed. Data were analysed using the mixed procedure of SAS (SAS Institute, Cary, NC, USA) and the model included the effects of collection day, group (high or low AFC), and their interaction. More COC (P < 0.0005) were collected from high than low AFC heifers (30.3 v. 9.3 ± 3.12 per heifer). Both the number and percentage of COC that cleaved had an interaction between collection day and group (P < 0.03). The interaction appeared to be due to low cleavage and development rates on 1 of 4 collection days (appeared not related to day of oestrous cycle). Although high compared to low AFC heifers had more COC that cleaved (18.7 v. 4.4 ± 1.84 per heifer), the percentage of cleaved COC did not differ (59.2 v. 49.8 ± 3.36%). There were no significant differences between high and low AFC heifers in the number of blastocysts (3.1 v. 0.6 ± 1.21 per heifer) or in the percentage of COC that developed to blastocysts (8.8 v. 5.2 ± 3.60%). In previous replicates (years), we reported that high AFC heifers had more COC collected, more COC that cleaved, and more COC that developed to blastocysts than low AFC heifers. In contrast, in this study numbers of COC that developed to blastocysts did not significantly differ between high and low AFC heifers. Additionally, the percentage of COC that cleaved, and that developed to blastocyst have been similar between high and low AFC heifers. Therefore, high compared to low AFC heifers may produce more IVP embryos; however, AFC does not appear to affect the competence of an oocyte to develop and mature to the blastocyst stage.
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Cupp, Andrea S., Sarah Nafziger, Mohamed Abedal-Majed, Sarah Tenley, Mariah Hart, Alexandria Snider, Jeff Bergman, et al. "206 Attainment and maintenance of pubertal cyclicity may predict high A4 cows with reduced fertility." Journal of Animal Science 97, Supplement_2 (July 2019): 118–19. http://dx.doi.org/10.1093/jas/skz122.210.
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Abstract The UNL physiology herd has a population of cows that secrete excess androstenedione (A4) in follicular fluid. These High A4 cows are less fertile, have irregular cycles, are often anovulatory, and have similar characteristics to women with Polycystic Ovary Syndrome (PCOS). Ovarian cortex cultures of High A4 cows secrete more A4 than controls. High A4 cows reached puberty 45 d earlier than control cows. Thus, we hypothesized that heifers reaching puberty earlier were predisposed to become High A4 cows. To test this hypothesis, we collected blood plasma from weaning to breeding (2012–2017) in 611 heifers. A custom SAS program was developed using progesterone >1ng/ml to identify four distinct puberty groups: 1) Early Puberty- 317.0 ± 3.6 days of age (doa) with continued cyclicity (n = 143); 2) Typical Puberty- 378.4 ± 2.1 doa with continued cyclicity (n = 279); 3) Start-Stop Puberty- 265.3 ± 4.1 doa with discontinued cyclicity (n = 91); and 4) Non-Cycling- no P4≥1ng/ml (n = 98). The pattern of Sex Hormone Binding Globulin (SHBG) was increased prior to puberty in Early and Typical and reduced in Start-Stop and Non-Cycling heifers. Early heifers (4.9) had greater prebreeding reproductive tract scores, followed by Typical (4.7), Start-Stop (4.5), and Non-Cycling (4.0) heifers. At breeding, all heifers that showed estrus in response to PGF2a were artificially inseminated. Typical (78.9%), Early (79.5%) and Start-Stop heifers (50.3%) had a greater response compared to Non-Cycling heifers (12.6%). All heifers were exposed to bulls, and overall pregnancy rate was not different. However, a greater percentage of Typical (57.9%), Early (51.0%), and Start-Stop (45.2%) heifers calved in the first 21 d of the calving season compared to Non-Cycling (20.9%). Start-Stop (3.0ng/ml) and Non-Cycling (4.2ng/ml) heifers had increased A4 in ovarian cortex culture media compared to Typical (0.062ng/ml) or Early (0.091ng/ml) puberty heifers. Greater A4 produced by ovarian cortex of Start-Stop and Non-Cycling heifers, irregular cycles and reduced calves in the first 21 d indicates these females may be predisposed to becoming High A4 cows with decreased fertility.
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Romano, MA, VH Barnabe, JP Kastelic, CA de Oliveira, and RM Romano. "Follicular Dynamics in Heifers during Pre-pubertal and Pubertal Period Kept under Two Levels of Dietary Energy Intake." Reproduction in Domestic Animals 42, no. 6 (December 2007): 616–22. http://dx.doi.org/10.1111/j.1439-0531.2006.00832.x.
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Sørensen, M. T., K. Sejrsen, and J. Foldager. "Estimation of Pubertal Mammary Development in Heifers by Computed Tomography." Journal of Dairy Science 70, no. 2 (February 1987): 265–70. http://dx.doi.org/10.3168/jds.s0022-0302(87)80006-1.
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Nguyen, L. T., A. Reverter-Gomez, A. Canovas, B. Venus, A. Islas-Trejo, S. A. Lehnert, J. F. Medrano, S. S. Moore, and M. R. Fortes. "P1012 Liver transcriptome from pre versus post-pubertal Brahman heifers." Journal of Animal Science 94, suppl_4 (September 1, 2016): 20–21. http://dx.doi.org/10.1093/ansci/94.supplement4.20.
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Copping, K. J., M. D. Ruiz-Diaz, C. S. Rutland, N. P. Mongan, M. J. Callaghan, I. C. McMillen, R. J. Rodgers, and V. E. A. Perry. "Peri-conception and first trimester diet modifies reproductive development in bulls." Reproduction, Fertility and Development 30, no. 5 (2018): 703. http://dx.doi.org/10.1071/rd17102.
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Nutritional perturbation during gestation alters male reproductive development in rodents and sheep. In cattle both the developmental trajectory of the feto–placental unit and its response to dietary perturbations is dissimilar to that of these species. This study examined the effects of dietary protein perturbation during the peri-conception and first trimester periods upon reproductive development in bulls. Nulliparous heifers (n = 360) were individually fed a high- or low-protein diet (HPeri and LPeri) from 60 days before conception. From 24 until 98 days post conception, half of each treatment group changed to the alternative post-conception high- or low-protein diet (HPost and LPost) yielding four treatment groups in a 2 × 2 factorial design. A subset of male fetuses (n = 25) was excised at 98 days post conception and fetal testis development was assessed. Reproductive development of singleton male progeny (n = 40) was assessed until slaughter at 598 days of age, when adult testicular cytology was evaluated. Low peri-conception diet delayed reproductive development: sperm quality was lowered during pubertal development with a concomitant delay in reaching puberty. These effects were subsequent to lower FSH concentrations at 330 and 438 days of age. In the fetus, the low peri-conception diet increased the proportion of seminiferous tubules and decreased blood vessel area in the testis, whereas low first trimester diet increased blood vessel number in the adult testis. We conclude that maternal dietary protein perturbation during conception and early gestation may alter male testis development and delay puberty in bulls.
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Bonavera, J. J., D. J. Tortonese, J. M. Doray, and F. Petraglia. "Endocrine response to superovulatory treatment in pre-pubertal beef heifers: its lack of ability to induce puberty." Animal Science 46, no. 2 (April 1988): 163–67. http://dx.doi.org/10.1017/s0003356100042215.
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AbstractThis study was carried out to investigate: (1) changes in plasma oestradiol-17β and progesterone concentrations in six pre-pubertal beef heifers, 9 months old, subjected to a superovulatory treatment, consisting of a single dose of PMSG followed 120 h later by a single injection of human chorionic gonadotrophin (HCG); and (2) the ability of this treatment to trigger cyclic gonadal activity. After PMSG administration, oestradiol-17β levels increased from 11·8 (s.d. 10·78) to 92·9 (s.d. 38·15) ng/1 just before HCG injection. The oestradiol-17β increase during the superovulatory treatment and numbe r of ovulations were correlated (r = 0·83; P < 0·05). After HCG injection, progesterone concentrations rose significantly reaching values which in some cases were higher than 60 [μg/1. The progesterone peak on days 9 and 10 post HCG was strongly correlated with the number of corpora lutea (r = 0·95; P < 0·01 and r = 0·92; P < 0·01, respectively). Progesterone determinations were performed for a period of 90 days after HCG administration. No evidence was found for the induction of permanent cyclic ovarian activity since all heifers returned, after the induced luteal phase, to their pre-pubertal condition.
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Kerby, Mike J., and Keith Cutler. "Use of artificial insemination and oestrus synchronisation in beef herds." Livestock 27, no. 6 (November 2, 2022): 259–64. http://dx.doi.org/10.12968/live.2022.27.6.259.
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The use of artificial insemmination (AI) in beef herds has been increasing in the last two decades especially when used in conjunction with oestrus synchronisation (OS) protocols. The resultant improvement in reproductive efficiency has a significant impact on productivity and profitability, particularly in seasonal block calving beef herds. Within this it is key that the nulliparous heifers calve down promptly in the block, and if these heifers can have heifer calves it will expediate genetic gain. This article reviews the benefits of using AI and the OS programmes commonly used, including those involving prostaglandin F 2 alpha (PG) alone, progesterone-releasing devices either with PG or with gonadotropin-releasing hormone and PG or with additional equine chorionic gonadotropin. It also comments on the relatively new ‘7 and 7 Synch’ protocol as well as approaches to pre-synchronisation, non-cycling beef cows, late-calving beef cows and pre-pubertal heifers.
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Fernandez, Rachel, Kasey A. Elder, John F. Odhiambo, Kiana Green, Rachel Dunn, and Derrick Coble. "81 Effects of Hurricane-Related Stress During Gestation on Replacement Heifer (Bos Taurus) Development in a Limited-Resource Beef cow-Calf System." Journal of Animal Science 100, Supplement_3 (September 21, 2022): 38–39. http://dx.doi.org/10.1093/jas/skac247.075.
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Abstract In a limited resource cow-calf operation, obtaining puberty in heifers is one of the main concerns for long-term productivity. Although nutritional factors have a large role in heifer development, environmental factors are sometimes overlooked until a catastrophic event such as a hurricane occurs. For this project, two heifer groups, born in the same herd at different intervals, were compared: Group 1(experienced catastrophic hurricane event in 3rd trimester of their fetal development) and Group 2 (no adverse event during gestation). The groups were weighed four similar time points during development: at 12 months of age (Period 1, pre-pubertal), 13-14 months (Period 2, puberty), pre-breeding (Period 3), and at the end of breeding (Period 4). The blood cortisol, glucose, and progesterone concentrations were compared between the groups during their pre-pubertal period. Group comparisons were performed using mixed procedures of SAS. Data are presented as means ±SEM. Group mean differences were declared significant at P < 0.05. We observed a significant (P < 0.01) Group by Period effect on heifer body weight (655.2± 14.2 vs. 747.3 ±15.4, for Groups 1 and 2, respectively). Overall, Group 1 was lighter than Group 2 in periods 1 and 2, but there was no difference thereafter. There were significant group differences in glucose (60.5± 8.8 vs 95.3±11.5, mg/dL for groups 1 and 2 respectively, P< 0.01) and progesterone (62.2±12.6 vs 124.0± 13.8, pg./mL for groups 1 and 2, respectively, P< 0.01). However, there was no significant difference in cortisol concentrations (P< 0.48). Therefore, catastrophic weather events such as hurricanes that are common throughout the world might have a negative impact on heifer development, as observed in this project. This observation warrants further investigation. Funding agency: USDA- NIFA CBG #2021-38821-34599
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Lawson, T. J., and A. D. Kennedy. "Inhibition of nighttime melatonin secretion in cattle: threshold light intensity for dairy heifers." Canadian Journal of Animal Science 81, no. 1 (March 1, 2001): 153–56. http://dx.doi.org/10.4141/a00-058.
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Five pre-pubertal Holstein heifers were exposed for 16 h to a light intensity of 400 lx and thereafter to intensities of 0, 50, 100, 200, or 400 lx for an additional 8 h (5 x 5 Latin square design). Exposure to all intensities inhibited (P < 0.05) melatonin secretion for the initial few hours (of the 8-h exposure period); melatonin concentration subsequently increased, particularly with the lower light intensities. Only the highest light intensity (400 lx) suppressed (P < 0.05) plasma melatonin concentrations for the entire 8-h exposure period. Key words: Threshold, supplemental, light, intensity, inhibition, melatonin, heifer
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Cardoso, Rodolfo C., and Gary L. Williams. "205 Neuroendocrine pathways and the nutritional control of puberty in heifers." Journal of Animal Science 97, Supplement_2 (July 2019): 119–20. http://dx.doi.org/10.1093/jas/skz122.211.
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Abstract Approximately 5 million beef heifers enter the U.S. cow herd annually, and their lifetime productivity is heavily-dependent upon their ability to attain puberty and produce a calf by 24 mo of age. However, a significant proportion of heifers within existing U.S. production systems fail to achieve these objectives. Therefore, approaches are needed that facilitate nutritional programming of the reproductive neuroendocrine axis, while minimizing feeding costs and optimizing the consistent establishment of puberty by 14–15 mo of age. Accelerated rates of BW gain during early calfhood, particularly between 4 and 9 mo of age, facilitate pubertal development by programming hypothalamic centers that regulate GnRH secretion. Among the different metabolic hormones, leptin plays a critical role in conveying nutritional information to the brain and controlling pubertal progression. Two hypothalamic neuronal populations that express the orexigenic peptide neuropeptide Y (NPY) and the anorexigenic peptide alpha melanocyte-stimulating hormone (αMSH) are key components of afferent pathways that convey inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. Our studies have demonstrated that short-term increases in dietary energy intake during juvenile development result in epigenetic, structural, and functional modifications in these hypothalamic pathways to promote high-frequency, episodic release of GnRH/LH. However, integrating the foundational knowledge of metabolic imprinting of the brain for early puberty with issues related to lifetime performance is complex. One approach has been to employ a novel stair-step nutritional regimen involving alternating periods of dietary energy-restriction and re-feeding during juvenile development. This approach is designed to support early onset of puberty by imprinting genomic, biochemical and morphologic alterations in the hypothalamus during key periods of brain development while optimizing other aspects of growth and performance. Finally, our recent findings suggest that maternal nutrition during gestation can also induce neuroendocrine changes that are likely to persist long after puberty and influence reproductive performance throughout adulthood in cattle.
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Paez, J. R., H. Basurto, A. Cohen, and C. S. Galina. "Potential for Producing Viable Embryos in Post Pubertal Heifers. Comparison during the Dry and Wet Seasons in the Tropics Using a Protocol Based on FSH or eCG." Journal of Agricultural Science 7, no. 12 (November 8, 2015): 84. http://dx.doi.org/10.5539/jas.v7n12p84.
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<p>The use of pubertal heifers to produce embryos before their natural breeding period which is normally at 3 years is a possibility that needs to be researched thus the objective of this assay was to superovulate pubertal <em>Bos indicus</em> heifers to obtain embryos in the dry and wet season, two phases were fodder availability is quite distinct.</p><p>Twenty Brahman heifers 18 to 24 months and weighing 300 to 330 kg were synchronized with a progesterone releasing device (CIDR, Pfizer, Mexico) for 9 days and concomitantly applying a superovulatory regimen, using a total of 280 mg of FSH (Folltropin-V Bioniche Mexico) in eight applications with decreasing dosages 12 h apart, starting with two dosages of 50 mg followed by another two of 40, two of 30, and ending with two of 20 mg.</p><p>One day before the device was withdrawn; an injection of 25 mg of prostaglandin F2a (Dinoprost Pfizer, México) was administered. For treatment with eCG an injection of 2000 I.U. of Equine Chorionic Gonadotropin eCG (Folligon, Intervet México) was administrated at day 6 after CIDR insertion.</p><p>There were differences in the total follicular response between the dry season average n = 84 and the wet, average n = 51 (p < 0.05) but not between treatments. The number of good quality embryos recovered in either season was not more than 4. Response in relation to number of corpus luteum (CL) present and number of embryos was affected by season (p < 0.05) regardless of the treatment utilized.</p><p>The production of embryos in post pubertal heifers is not feasible based in our results. Heat stress, nutritional inconsistencies, season when treatment applied and age might be some of the main driving factors for this poor response.</p>
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Chase, C. C., E. C. Wright, A. K. McNeel, R. A. Cushman, G. A. Perry, A. S. Cupp, J. L. Vallet, D. D. Sypherd, and J. R. Miles. "142 EFFECT OF HIGH AND LOW ANTRAL FOLLICLE COUNT IN PUBERTAL BEEF HEIFERS ON IVF." Reproduction, Fertility and Development 26, no. 1 (2014): 184. http://dx.doi.org/10.1071/rdv26n1ab142.
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Pubertal heifers can be classified between those with high (n = 25) or low (n = 15) antral follicle counts (AFC). The objective of this study was to determine oocyte development and maturation (e.g. fertility) in an IVF system for high- and low-AFC heifers. From a pool of 120 heifers, 10 high- and 10 low-AFC heifers were determined by transrectal ultrasonography; all heifers with evidence of oestrous cyclicity (i.e. pubertal) were synchronized with two 5-mL injections of prostaglandin F2α 11 days apart. Heifers were euthanized over 4 days on Days 15 to 16 of the synchronized oestrous cycle. A total of 15 heifers (n = 7 high and n = 8 low AFC) were at the appropriate stage of the oestrous cycle. Ovaries were collected and transported to the laboratory. Follicles less than 8 mm in diameter were aspirated. The IVF procedures and media were as previously described (Miles et al. 2004. Biol. Reprod. 71, 1919–1926). Cumulus-oocyte complexes (COC) were identified and washed in oocyte collection medium and then in maturation medium and were cultured (5% CO2; 38.5°C) for 24 h. Following maturation, COC were transferred and washed in fertilization medium. Thawed frozen semen from a crossbred bull was subjected to the swim-up procedure. Motile spermatozoa were collected and added to COC to yield a final concentration of spermatozoa per milliliter of fertilization medium. About 24 h later, presumptive zygotes were washed in development medium, placed in microdrops of development medium, and cultured for 8 days. On Days 3 and 8 after fertilization, cleavage and blastocyst development, respectively, were assessed. Data were analysed using the Proc Mixed procedure of SAS (SAS Institute Inc., Cary, NC, USA) and the model included the effects of day of collection (n = 4), group (n = 7 high- or n = 8 low-AFC heifers), and the interaction. The interaction did not differ (P = 0.10). Day of collection influenced (P < 0.05) the number of COC and the number of oocytes cleaved. High- compared to low-AFC heifers had the greater (P < 0.05) numbers of COC (42.7 ± 4.66 v. 22.1 ± 4.59), oocytes that cleaved (28.1 ± 3.60 v. 15.9 ± 3.55), and developed to blastocysts (13.2 ± 1.71 v. 6.2 ± 1.69). However, there was no difference (P > 0.10) in the percentage of COC that cleaved (65.3 ± 5.58 v. 66.2 ± 5.50%, high v. low, respectively) or that developed to blastocysts (46.7 ± 6.75 v. 42.2 ± 6.65%). In conclusion, AFC did not appear to affect oocyte maturation and development through the blastocyst stage.
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Sejrsen, Kris, John Foldager, Martin T. Sorensen, R. Michael Akers, and Dale E. Bauman. "Effect of Exogenous Bovine Somatotropin on Pubertal Mammary Development in Heifers." Journal of Dairy Science 69, no. 6 (June 1986): 1528–35. http://dx.doi.org/10.3168/jds.s0022-0302(86)80569-0.
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Devi, Laishram Sunitibala, D. V. Singh, and Sandeep Kour. "Morphological Traits of Pubertal and Pregnant Frieswal Heifers Under Field Conditions." Journal of Animal Research 5, no. 4 (2015): 903. http://dx.doi.org/10.5958/2277-940x.2015.00149.7.
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Stahringer, R. C., D. A. Neuendorff, and R. D. Randel. "Seasonal variations in characteristics of estrous cycles in pubertal Brahman heifers." Theriogenology 34, no. 2 (August 1990): 407–15. http://dx.doi.org/10.1016/0093-691x(90)90532-x.
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Torres, A., M. Batista, P. Diniz, E. Silva, L. Mateus, and L. Lopes-da-Costa. "Effects of oocyte donor age and embryonic stage of development on transcription of genes coding for enzymes of the prostaglandins and progesterone synthesis pathways in bovine in vitro produced embryos." Zygote 23, no. 6 (September 26, 2014): 802–12. http://dx.doi.org/10.1017/s0967199414000446.
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SummaryThe ability of early bovine embryos to produce prostaglandins (PGs) and progesterone (P4), and the role of these mediators in embryonic development and survival are poorly understood. In this study we tested the hypothesis that day 7 bovine embryos are able to transcribe genes coding for enzymes of the PGs (PTGS2, PGES, PGFS) and P4 (StAR, P450scc, 3β-HSD) synthesis pathways, and that transcription levels of these genes are associated with developmental progression and heifer age-related [pre-pubertal (PP) versus post-pubertal cyclic (C)] oocyte competence. Compared with C heifer oocytes, PP heifer oocytes showed a lower (P < 0.0001) in vitro blastocyst rate, but in embryos developing until day 7, heifer age had no effect on quality grade. Day 7 quality grade 1–2 embryos were selected for RNA extraction and gene transcription analysis by qRT-PCR, in a 2 × 2 factorial design [age (PP or C) × embryonic stage (compact morulae and early blastocysts, CM + EBL, or blastocysts and expanded blastocysts, BL + BEX); 15 embryos/group]. Transcription levels of PTGS2, PGES, PGFS, P450scc and 3β-HSD were not affected by heifer age but were higher (P < 0.01) in BL + BEX than in CM + EBL. In conclusion, the main limiting factor for embryo production from PP heifers is oocyte competence. Day 7 bovine embryos evidence transcription of genes coding for enzymes of PGs and P4 synthesis pathways, and transcription levels are associated with blastocyst differentiation. This prompts for an autocrine/paracrine action of PGs and P4 in early bovine embryonic development.
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Albino, Ronan L., Marcos I. Marcondes, Robert M. Akers, Edenio Detmann, Bruno C. Carvalho, and Tadeu E. Silva. "Mammary gland development of dairy heifers fed diets containing increasing levels of metabolisable protein: metabolisable energy." Journal of Dairy Research 82, no. 1 (January 16, 2015): 113–20. http://dx.doi.org/10.1017/s0022029914000697.
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This study was conducted to evaluate the development of the mammary gland in Holstein heifers subjected to different dietary metabolisable protein (MP): metabolisable energy (ME) ratios. Twenty-five Holstein heifers (initial body weight (BW) 213±13·5 kg and initial average age 7·8±0·5 months) were divided into five treatments. The treatments were designed to provide MP:ME ratios equal to 33, 38, 43, 48, and 53 g of MP per Mcal of ME. All diets were formulated to have the same energy content (2·6 Mcal ME/kg dry matter). Actual MP:ME ratios were 36·2, 40·2, 46·2, 47·1, and 50·8 g MP/Mcal ME. The experiment was conducted in a randomised block design, while considering initial BW as a blocking factor to evaluate pre- and post-pubertal periods. Block effect was not observed for all variables evaluated; hence it was considered that the diets had the same influence both on pre- and post-pubertal phases. Dry matter and nutrient intake did not change between treatments, excepting protein intake and digestibility. Serum concentrations of insulin-like growth factor 1 increased linearly across treatments. Changes in the pixel brightness of mammary gland ultrasound images, which are associated with lipid content, were significantly influenced by MP:ME ratios in the diet of heifers that were subjected to accelerated growth rates. It is not recommended to use diets of less than 38 g MP/Mcal ME in diets to heifers allowed to gain more than 1 kg/d.
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Tosta, R., R. Sala, D. Pereira, D. Kendall, F. Elliff, J. Ziemer, E. Adelsberger, J. Moreno, B. Catussi, and P. Baruselli. "109 Effect of ruminal infusion with propylene glycol on the invitro embryo production of Holstein (Bos taurus) prepubertal heifers and pregnancy rate of the embryo transfer." Reproduction, Fertility and Development 32, no. 2 (2020): 181. http://dx.doi.org/10.1071/rdv32n2ab109.
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The aim of this study was to evaluate the effect of ruminal infusion with propylene glycol (PG) on the invitro embryo production (IVEP) of Holstein (Bos taurus) prepubertal heifers (7 to 8 months). For this study, 16 prepubertal heifers were distributed into two groups: Propylene Glycol Group (PGG; n=8) and Control Group (CG; n=7). Additionally, 8 pubertal heifers were used for the positive control group (PUB). All animals (n=23) underwent an ovum pickup (OPU) for follicular ablation on Day 0, followed by an FSH protocol treatment (160mg performed in 4 injections twice a day in decreasing doses, designated as D2PM, D3AM, D3PM, and D4AM). Animals from PGG received a ruminal infusion with 250mL of PG twice a day on Days 0, 1, 2, 3, and 4, using a drench. Animals from CG and PUB did not receive any additional treatment. On Day 5 all animals underwent another OPU, and oocytes were used for the IVEP (Sexing Technologies commercial laboratory). The produced embryos were transferred fresh to Holstein heifer recipients. Additionally, blood sampling was performed on D4PM (M1) and on the day of OPU (D5AM, M2) for insulin-like growth factor (IGF-1, via radioimmunoassay) and glucose (hexokinase) analysis. Data were analysed using the GLIMMIX procedure of SAS. No difference was observed between groups for number of recovered oocytes (CG: 14.28±1.9; PGG: 14.87±3.9; PUB: 10.50±2.2; P=0.24), number of viable oocytes (CG: 10.71±2.5; PGG: 10.75±2.7; PUB: 9.50±2.0; P=0.80), cleaved oocytes (CG: 7.71±1.5; PGG: 9.50±2.1; PUB: 6.25±1.4; P=0.14), cleavage rate (CG: 54.2% (7.7 out of 14.2); PGG: 64.1% (9.5 of 14.8); PUB: 59.0% (6.2 of 10.5); P=0.35) and number of blastocysts (CG: 1.71±0.5; PGG: 2.00±0.6; PUB: 3.12±1.0; P=0.71). Pubertal heifers had higher blastocyst rates compared with prepubertal heifers, regardless of PG treatment (CG: 11.9% (1.7 of 14.2); PGG: 13.5% (2 of 14.8); PUB: 29.5% (3.1 of 10.5); P=0.01). No difference was observed between groups for 30-day (CG: 41.7% (5 of 12); PGG: 46.7% (7 of 15); PUB: 42.9% (6 of 14); P=0.96) or 60-day pregnancy rates (CG: 41.7% (5 of 12); PGG: 33.3% (5 of 15); PUB: 42.9% (6 of 14); P=0.86). In addition, no difference was observed for pregnancy loss between 30 and 60 days (CG: 0.0% (0 of 12); PGG: 13.3% (2 of 15); PUB: 0.0% (0 of 14); P=0.99). Regarding metabolic blood analysis, no difference was observed for IGF-1 (ngmL−1) between groups (P=0.38), moment of sample collection (P=0.06), and interaction of group×moment (P=0.87; CG/M1: 263.36±15.2; CG/M2: 297.71±18.7; PGG/M1: 304.25±26.9; PGG/M2: 332.61±31.6; PUB/M1: 309.16±19.9; PUB/M2: 311.07±18.8). Glucose (mg dL−1) was higher (P=0.0001) for pubertal heifers (91.63±1.4) compared with the other groups (CG: 102.25±1.1; PGG: 107.71±3.5); however, no difference was observed for moment of sample collection (P=0.35) or interaction of group×moment (P=0.36). These data show that treatment with PG was not efficient to improve the IVEP of prepubertal Holstein heifers, embryos from prepubertal heifers treated with PG did not have increased pregnancy rate, and treatment did not increase IGF-1 or glucose blood levels.
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Pitchford, Wayne S., Judith M. Pitchford, Jena G. Alexopoulos, and Michelle L. Hebart. "Genomic Analysis of Purebred and Crossbred Angus Cows Quantifies Heterozygosity, Breed, and Additive Effects on Components of Reproduction." Animals 12, no. 1 (December 28, 2021): 61. http://dx.doi.org/10.3390/ani12010061.
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Multiple studies have quantified the production differences of Hereford Angus crossbreds compared to purebred Angus for a range of traits including growth, carcass, and reproductive traits. This study aims to quantify breed and heterosis effects on maternal performance using genomics. Thirty Hereford and thirty Angus sires were mated to 1100 Angus heifers and cows in a large commercial herd run on pasture at Musselroe Bay, Tasmania, Australia. Approximately 1650 calves were born. Heifers were weaned, scanned for attainment of puberty prior to joining at approximately 15 months of age, joined, and then recorded for status of pregnancy, calving, lactating, 2nd pregnancy, and weaning of second calf. Heterozygosity effects were significant for heifer pre-joining weight and height as well as proportion pubertal. Breed differences were significant for the same traits plus pregnancy rate at second joining and proportion rearing two calves. Genetic parameters were reported for 13 traits. On average, higher genetic merit (Estimated Breeding Value, EBV percentile) Hereford bulls were used than Angus for growth and puberty, but they were similar for fat and reproduction. Days to calving BREEDPLAN EBVs of the sires were related to puberty and reproduction. Scrotal size BREEDPLAN EBVs of the sires were related to attainment of puberty genomic EBVs calculated. In summary, breed differences in growth and puberty were due to heterosis, but there was an advantage of Hereford genes for reproductive performance. Ongoing emphasis on selection for reduced days to calving and estimation of multi-breed EBVs is important.
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Cardoso, Rodolfo C., Bruna R. C. Alves, Ligia D. Prezotto, Jennifer F. Thorson, Luis O. Tedeschi, Duane H. Keisler, Marcel Amstalden, and Gary L. Williams. "Reciprocal changes in leptin and NPY during nutritional acceleration of puberty in heifers." Journal of Endocrinology 223, no. 3 (October 17, 2014): 289–98. http://dx.doi.org/10.1530/joe-14-0504.
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Feeding a high-concentrate diet to heifers during the juvenile period, resulting in increased body weight (BW) gain and adiposity, leads to early-onset puberty. In this study, we tested the hypothesis that the increase in GnRH/LH release during nutritional acceleration of puberty is accompanied by reciprocal changes in circulating leptin and central release of neuropeptide Y (NPY). The heifers were weaned at 3.5 months of age and fed to gain either 0.5 (Low-gain; LG) or 1.0 kg/day (High-gain; HG) for 30 weeks. A subgroup of heifers was fitted surgically with third ventricle guide cannulas and was subjected to intensive cerebrospinal fluid (CSF) and blood sampling at 8 and 9 months of age. Mean BW was greater in HG than in LG heifers at week 6 of the experiment and remained greater thereafter. Starting at 9 months of age, the percentage of pubertal HG heifers was greater than that of LG heifers, although a replicate effect was observed. During the 6-h period in which CSF and blood were collected simultaneously, all LH pulses coincided with or shortly followed a GnRH pulse. At 8 months of age, the frequency of LH pulses was greater in the HG than in the LG group. Beginning at 6 months of age, concentrations of leptin were greater in HG than in LG heifers. At 9 months of age, concentrations of NPY in the CSF were lesser in HG heifers. These observations indicate that increased BW gain during juvenile development accelerates puberty in heifers, coincident with reciprocal changes in circulating concentrations of leptin and hypothalamic NPY release.
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PÔRTO, REGIANI, BENEDITO OLIVEIRA FILHO, HENRIQUE FERRAZ, LUCIANO CAIXETA, MARCO ANTONIO VIU, and MARIA LÚCIA GAMBARINI. "Histopatology of the reproductive tract of Nellore pubertal heifers with genital ureaplasmosis." Anais da Academia Brasileira de Ciências 89, no. 4 (December 7, 2017): 2987–96. http://dx.doi.org/10.1590/0001-3765201720160803.
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Macrina, A. L., P. R. Tozer, and R. S. Kensinger. "Induced lactation in pubertal heifers: Efficacy, response to bovine somatotropin, and profitability." Journal of Dairy Science 94, no. 3 (March 2011): 1355–64. http://dx.doi.org/10.3168/jds.2010-3811.
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Royal, M. D., A. P. F. Flint, R. Webb, D. Blache, and J. A. Woolliams. "Estimation of genetic variation in plasma leptin concentrations in pre-pubertal heifers." Proceedings of the British Society of Animal Science 2002 (2002): 44. http://dx.doi.org/10.1017/s1752756200007006.
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Leptin is involved in the regulation of food intake, energy expenditure and whole body energy balance. In livestock species these processes are important for optimisation of growth, reproduction, lactation and overall health and well-being. Condition score is a useful indicator of energy balance and is highly correlated (-0.84) genetically to commencement of luteal activity (CLA), an endocrine measurement of fertility in dairy cattle (Royal et al., submitted). Circulating leptin levels drop post-partum reflecting changes in energy balance and fat mobilisation. The interval to first ovulation post-partum is phenotypically correlated (0.83) to the interval from parturition to the leptin nadir (Kadokawa et al. 2000), suggesting that a delay in the recovery of leptin secretion postpartum increases the delay to first ovulation. The heritability of circulating leptin concentrations in humans and pigs is high (0.39-0.61; Cameron et al., 2000; Rotimi et al., 1997). If this were also the case in cattle, and postpartum changes were related to concentrations at an early age, then it would be of immense value to the genetic improvement of traits associated with fertility.