Academic literature on the topic 'Progeny merit'

Groups of sibs, sisters to bulls being bred for progeny testing, can be produced by multiple ovulation and embryo transfer (MOET). Sib tests are complete at 3 yr of age, and progeny tests when bulls are about 5.5–6 yr of age. The merit of commercial semen could be increased by using the bulls with the highest estimated breeding values from both the sib test group and the progeny test group rather than only from the latter. With current selection rates (20%) among progeny-tested bulls for commercial use, current genetic trend (0.1 SD units per year) in bulls and with the equivalent of 3–7 full sisters per bull, the relative genetic superiority of semen from the combined groups could be from 1.10 to 1.20 times that from the progeny-tested group alone. Key words: Embryo transfer, sib testing, progeny testing, commercial semen

USDA quality and yield grade are primary driving forces for carcass value in the United States. Carcass improvements can be achieved by making selection decisions based on the results of genetic evaluations in the form of expected progeny differences (EPD), real-time ultrasound imaging, and physical evaluation of candidate breeding animals. In an effort to advance their ability to accurately predict the breeding value of potential sires for carcass traits, the American Simmental Association launched the Carcass Merit Program as a means to collect progeny sire group carcass information. All records were extracted from the American Simmental Association database. Progeny data were organized by sire family and progeny performance phenotypes were constructed. Sire genotypes were filtered, and a multi-locus mixed linear model was used to perform an association analysis on the genotype data, while correcting for cryptic relatedness and pedigree structure. Three chromosomes were found to have genome-wide significance and this conservative approach identified putative QTL in those regions. Three hundred ninety-three novel regions were identified across all traits, as well as 290 novel positional candidate genes. Correlations between carcass characteristics and maternal traits were less unfavorable than those previously reported.

The impact of using high genetic merit beef bulls in a dairy beef supply chain was compared to using unrecorded beef bulls. Dairy cows were inseminated with Ezicalve Hereford semen (high genetic merit for calving ease and growth), followed by natural mating with Ezicalve and unrecorded Hereford bulls. The resulting 186 progeny were monitored from birth to 2 years old. Ezicalve sired calves required no calving assistance and averaged 4 kg lighter at birth than those from unrecorded sires (P

AbstractLook ahead mate selection (LAMS) schemes have been proposed to improve longer-term genetic merit when both selection and crossbreeding are important. We investigate the performance of a LAMS scheme which includes both predicted progeny merit and predicted grandprogeny merit in a mate selection index (MSI). Simulation of a multi-breed beef population, with additive breeding values, direct and maternal breed effects and direct and maternal heterosis was used to compare response from the LAMS scheme to mate selection on progeny merit only (PROG), selection on estimated breeding value (EBV) followed by random mating (RAND) and a structured crossbreeding scheme (CROSS). An additional strategy, LAMS + CO, was similar to LAMS but included a negative weighting on the coancestry of selected animals in the MSI to reduce inbreeding. LAMS gave up to 3% greater response in generation eight than PROG, 4·5% greater response than RAND, and 15% greater response than CROSS. Results from LAMS + CO were very similar to LAMS but inbreeding was 11% less from LAMS + CO at generation eight. The advantage of LAMS and LAMS + CO over PROG in later generations was hypothesized to be the result of positive assortative mating and greater use of maternal effects. Evidence to support the hypothesis of assortative mating was a positive significant correlation of EBVs of mates (sires and dams) in LAMS and LAMS + CO but not in PROG. Strategies PROG, LAMS and LAMS + CO all created closed populations of animals with optimum composite breed proportions.

ABSTRACTFormulae are derived to calculate the genetic merit of a commercial population during replacement of one breed by another, based on the rates of genetic change in the old and new breeds, the initial difference between the breeds, the lag between the first use of replacement stock and the appearance of their genes in commercial progeny and the effect of replacement on the old breed improvement scheme. By comparing the merit of the population with and without replacement the value of a change in breed can be assessed. The method is illustrated with an example from pig breeding.

AbstractThe objective of any well designed progeny test programme is to identify those individuals that have inherited the favourable genes from his parents. Bulls that enter a progeny test programme have been highly selected on a set of selection criteria. The criteria vary among organizations based upon their breeding philosophy and their prediction of the future economic value of various traits. The accuracy of choosing among this highly selected group is quite low. Increasing the accuracy of selection before progeny testing is the greatest potential application of genetic marker technology. Markers associated with traits of importance can greatly enhance traditional selection methods by increasing the prospect of an individual having the desired characteristics. Genetic marker-assisted selection can greatly increase the actual genetic merit of traits of economic importance

How to maximize the use of the genetic merits of the high-ranking boars (also called superior ones) is a considerable question in the pig breeding industry, considering the money and time spent on selection. Somatic cell nuclear transfer (SCNT) is one of the potential ways to answer the question, which can be applied to produce clones with genetic resources of superior boar for the production of commercial pigs. For practical application, it is essential to investigate whether the clones and their progeny keep behaving better than the “normal boars”, considering that in vitro culture and transfer manipulation would cause a series of harmful effects to the development of clones. In this study, 59,061 cloned embryos were transferred into 250 recipient sows to produce the clones of superior Pietrain boars. The growth performance of 12 clones and 36 non-clones and the semen quality of 19 clones and 28 non-clones were compared. The reproductive performance of 21 clones and 25 non-clones were also tested. Furthermore, we made a comparison in the growth performance between 466 progeny of the clones and 822 progeny of the non-clones. Our results showed that no significant difference in semen quality and reproductive performance was observed between the clones and the non-clones, although the clones grew slower and exhibited smaller body size than the non-clones. The F1 progeny of the clones showed a greater growth rate than the non-clones. Our results demonstrated through the large animal population showed that SCNT manipulation resulted in a low growth rate and small body size, but the clones could normally produce F1 progeny with excellent growth traits to bring more economic benefits. Therefore, SCNT could be effective in enlarging the merit genetics of the superior boars and increasing the economic benefits in pig reproduction and breeding.

Bulls that originate from breeding schemes with extensive use of multiple ovulation and embryo transfer (MOET) can be selected on pedigree information, the performance of their contemporary female full- and half-sibs or based on a progeny test. Combined selection across groups of bulls with different sources of information is shown to be superior to selection of progeny tested bulls alone. The magnitude of the superiority for a given selection rate is determined by the differences in genetic merit between the groups and ranges from 5 to 65%. Depending on the annual genetic progress the majority of the bulls are selected either on pedigree or progeny information. The proportion of sib-tested bulls ranges from 9 to 23%. When breeding activities are concentrated in nucleus herds, possible genotype by environment interactions between performance in the test herd and in the commercial population have to be considered. Genotype by environment interactions increase the proportion of progeny tested sires that will be selected. However, the proportion of progeny tested sires used is reduced by genotype by environment interactions among the groups of a heterogenous commercial production environment. Key words: Embryo transfer, sire selection, genotype-by-environment interactions

A program to determine optimum contribution selection using differential evolution was developed. The objective function to be optimized was composed by the expected merit of the future progeny and the coancestry among selected parents. Simulated and real datasets of populations with overlapping generations were used to validate and test the performance of the program. The program was computationally efficient and feasible for practical applications. The expected consequences of using the program, in contrast to empirical procedures to control inbreeding and/or to selection based exclusively on expected genetic merit, would be the improvement of the selection response and a more effective control of inbreeding.

Mate selection is an attractive breeding strategy for multi-breed beef cattle populations, as it allows selection and crossbreeding to be exploited simultaneously. Two components are required for mate selection; an objective function called a mate selection index (MSI) which describes economic gain as a function of selection and mate allocations (or 'mate selections'), and a mate selection algorithm which finds the mating set which maximises the MSI.

One concern with mate selection is that as breeding decisions are based on progeny merit only (the next generation), short term genetic merit may be maximised at the cost of longer term genetic merit. To address this concern, LAMS (Look Ahead Mate Selection) schemes have been proposed. In LAMS schemes, some weight is given in the MSI to the merit of predicted grand-progeny in mate selection decisions.

To date, there have been few studies predicting the benefits of mate selection in multi-breed beef cattle populations. The impact of mate selection, especially LAMS schemes, on population structure and longer term genetic gain is unknown. Further, the advantages of mate selection when the genetic model of multi-breed populations is extended beyond selection and heterosis to include within breed dominance variance is unknown.

This thesis was designed to investigate three issues:

1. What population structures will emerge when mate selection (including LAMS schemes) is applied in multi-breed populations?
2. What is the effect of longer term implementation of LAMS schemes on genetic merit of multi-breed populations
3. Does mate selection significantly improve the genetic value of a multi-breed population when individual dominance is included in the MSI (relative to other breeding strategies, such as selection followed by mate allocation)?

To investigate the first issue, a deterministic evaluation of mate selection was considered. Mate selection was at the level of genetic groups, where genetic groups were defined by breed composition and selection history. The initial population structure consisted of breeds A and B. Genetic merit of genetic group l was y_l =  µ_l + g^A_lm_A + g^B_lm_B + g^A_jd_ABg^B_k + g^B_jd_ABg^A_k, where g^A_l, the proportion of breed A in progeny genotype l, is calculated as g^A_l = 1/2(g^A_j + g^A_k), where g^A_j and g^A_k are proportions of breed A in parental genotypes j and k respectively. The proportion of breed B in progeny genotype l is calculated similarly. Parameter d_AB, is the F₁ heterosis when breeds A and B are crossed, and µ_l is the mean additive breeding value for progeny genotype l.

The aim of each breeding schemes was to create a new herd in the first generation by importing sires and dams of breeds A and B, and then breed a further generation of progeny in the home herd. The second generation of progeny could be created either by importing more sires and dams, or using sires and dams bred in the home herd in the previous generation. It was assumed no selection was occurring within the foreign populations. Breeding schemes were compared by using the sum of progeny merit over the two generations, for a range of heritabilities and heterosis values. Schemes evaluated were structured crossbreeding (F₁ and F₂ designs), progeny merit each generation as mate selection criteria (PROG_DET), or cumulative merit over two generations as mate selection criteria (CUMUL_DET). CUMUL_DET was a LAMS scheme, as merit of the generation beyond the progeny generation was considered in the mate selection decisions. At all parameter values, PROG_DET and CUMUL_DET gave better cumulative merit than structured crossbreeding designs. This was a result of selecting sires and dams from the whole population rather than within genotypes or genetic groups. The advantage of mate selection strategies over structured strategies was greatest when h²=0.6; up to 1.9% for cumulative merit from CUMUL_DET over the best F₁ cross.

CUMUL_DET gave slightly greater cumulative merit than PROG_DET in all scenarios, with the advantage increasing with greater heritability or greater selection intensities. The advantage of CUMUL_DET over PROG_DET was from allocation of a proportion of purebred matings in the first generation in the home herd in CUMUL_DET. In the second generation, purebred progeny from these selected purebred parents could be crossed to breed F₁ grandprogeny with maximum heterosis and cumulative additive merit from selection. The proportion of purebred matings in the home herd in the first generation increased with heritability (1% of all matings in the first generation when h²=0.1 and 11% when h²=0.6).

To investigate the second issue, response from implementation of tactical (at the individual animal level) LAMS schemes was investigated. The genetic model used included additive breed and maternal effects, and direct and maternal heterosis. For this model, progeny merit of an individual progeny from a mating was PM_i = 1/2(p^T_s + p^T_d)a + p^T_sDp_d + p^T_da_m + p^T_mgsD_mp_mgd where vector p represents the proportion of genes of each breed in sire (s) or dam (d), maternal grand sire (mgs) or maternal granddam (mgd), a is a vector of fixed breed effects (breed means for each breed), a_m is a vector of fixed maternal breed effects, D is a breed x breed matrix of direct heterosis effects, and Dm is a breed x breed matrix of maternal heterosis effects.

Schemes investigated included mate selection with progeny merit only in the MSI (PROG strategy) and mate selection with progeny merit and grandprogeny merit equally weighted in the MSI (LAMS strategy). An additional scheme, COMP, was evaluated which used the contribution of the mating set to progeny with an optimal composite genotype as the MSI. Schemes were assessed using simulation of a single trait (yearling weight) over six generations of a four breed population. It was assumed no selection was occurring in foreign populations. With LAMS, a proportion of matings each generation in all simulations were allocated to breed F1 dams, improving the merit of the next generation, as a three breed cross could be created. LAMS gave the highest cumulative progeny merit over six generations; 20kg greater than PROG, and almost 70kg greater than COMP.

COMP created a population of optimum composite animals after six generations of breeding, with no variation in breed composition among individuals in the population (all animals had the optimum composite genotype). This strategy would be useful for commercial beef producers aiming to produce uniform lines of turnoff progeny.

The performance of LAMS was also evaluated when the genetic model was extended to include individual additive breeding values...

Feed inputs represent the largest variable cost of producing meat and milk from ruminant animals. Thus, strategies that improve the efficiency of feed utilization are needed to improve the global competitiveness of Israeli and U.S. cattle industries, and mitigate their environmental impact through reductions in nutrient excretions and greenhouse gas emissions. Implementation of innovative technologies that will enhance genetic merit for feed efficiency is arguably one of the most cost-effective strategies to meet future demands for animal-protein foods in an environmentally sustainable manner. While considerable genetic variation in feed efficiency exist within cattle populations, the expense of measuring individual-animal feed intake has precluded implementation of selection programs that target this trait. Residual feed intake (RFI) is a trait that quantifies between-animal variation in feed intake beyond that expected to meet energy requirements for maintenance and production, with efficient animals being those that eat less than expected for a given size and level of production. There remains a critical need to understand the biological drivers for genetic variation in RFI to facilitate development of effective selection programs in the future. Therefore, the aim of this project was to determine the biological basis for phenotypic variation in RFI of growing and lactating cattle, and discover metabolic biomarkers of RFI for early and more cost-effective selection of cattle for feed efficiency. Objectives were to: (1) Characterize the phenotypic relationships between RFI and production traits (growth or lactation), (2) Quantify inter-animal variation in residual HP, (3) Determine if divergent RFIphenotypes differ in HP, residual HP, recovered energy and digestibility, and (4) Determine if divergent RFI phenotypes differ in physical activity, feeding behavior traits, serum hormones and metabolites and hepatic mitochondrial traits. The major research findings from this project to date include: In lactating dairy cattle, substantial phenotypic variation in RFI was demonstrated as cows classified as having low RMEI consumed 17% less MEI than high-RMEI cows despite having similar body size and lactation productivity. Further, between-animal variation in RMEI was found to moderately associated with differences in RHP demonstrating that maintenance energy requirements contribute to observed differences in RFI. Quantifying energetic efficiency of dairy cows using RHP revealed that substantial changes occur as week of lactation advances—thus it will be critical to measure RMEI at a standardized stage of lactation. Finally, to determine RMEI in lactating dairy cows, individual DMI and production data should be collected for a minimum of 6 wk. We demonstrated that a favorably association exists between RFI in growing heifers and efficiency of forage utilization in pregnant cows. Therefore, results indicate that female progeny from parents selected for low RFI during postweaning development will also be efficient as mature females, which has positive implications for both dairy and beef cattle industries. Results from the beef cattle studies further extend our knowledge regarding the biological drivers of phenotypic variation in RFI of growing animals, and demonstrate that significant differences in feeding behavioral patterns, digestibility and heart rate exist between animals with divergent RFI. Feeding behavior traits may be an effective biomarker trait for RFI in beef and dairy cattle. There are differences in mitochondrial acceptor control and respiratory control ratios between calves with divergent RFI suggesting that variation in mitochondrial metabolism may be visible at the genome level. Multiple genes associated with mitochondrial energy processes are altered by RFI phenotype and some of these genes are associated with mitochondrial energy expenditure and major cellular pathways involved in regulation of immune responses and energy metabolism.