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Articoli di riviste sul tema "Ewes South Australia Fertility"
1
Adams, NR, MR Sanders e AJ Ritar. "Oestrogenic damage and reduced fertility in ewe flocks in south Western Australia". Australian Journal of Agricultural Research 39, n. 1 (1988): 71. http://dx.doi.org/10.1071/ar9880071.
Testo completoAbstract (sommario):
Prolonged exposure to oestrogen causes transsexual redifferentiation in the ewe, which can be assessed experimentally by measuring the cross-sectional area of lamina propria (lp) tissue lying underneath the cervical folds in the mid-cervix. The extent of transsexual redifferentiation caused by prolonged exposure to clover oestrogens was measured in ewes from 13 farms in Western Australia. Groups of 90-157 mature ewes were mated under normal farming husbandry, and consigned to the abattoirs 6-8 weeks later. Histological sections were prepared from the mid cervix of 37-80 ewes from each flock. The area of lp was increased in ewes from the three farms with a history of infertility due to oestrogenic clover, when compared with ewes from the four farms in non-clover areas. Overall, the mean area of lp in ewes from the 13 farms was correlated (r = 0.81, P < 0.01) with the proportion of non-pregnant ewes, but less so with the potential lambing rate as judged by the number of foetuses/100 ewes (r = -0.51, N.S.). This contrast came about because flocks affected by oestrogen-induced transdifferentiation also tended to have higher ovulation rates; a regression including both the ovulation rate and area of lp accounted for 89010 of the variation between flocks in potential lambing rate. It is concluded that clover oestrogens are an important cause of the relatively high proportion of ewes which fail to lamb in Western Australia.
2
Kleemann, David O., Simon K. Walker, Raul W. Ponzoni, Dennis R. Gifford, James R. W. Walkley, Darryl H. Smith, Richard J. Grimson, Kaylene S. Jaensch, Samuel F. Walkom e Forbes D. Brien. "Effect of previous reproductive performance on current reproductive rate in South Australian Merino ewes". Animal Production Science 56, n. 4 (2016): 716. http://dx.doi.org/10.1071/an15114.
Testo completoAbstract (sommario):
Reproductive performance of ewes in the current year may be influenced by their performance in the previous year and by the ability of seasonal and management conditions to facilitate full recovery before the next breeding cycle. This possibility was tested by analysing reproductive data from 2100 South Australian Merino ewes mated to Merino rams annually from 1991 to 1997. The model fitted to the data included the fixed effects of previous reproductive performance (PRP) (no lambs born; single or multiple lambs born, none reared; single lambs born, singles reared; multiples born, singles reared; multiples born, multiples reared), age of ewe (2.5, 3.5, 4.5 years), year (1992–1997), bloodline (A, B, L, X) and all two-way interactions. Current-year parameters were net reproduction rate (NRR, lambs weaned of ewes joined) and its components of fertility (ewes lambing of ewes joined), fecundity (lambs born of ewes lambing) and lamb survival (lambs weaned of lambs born). Other parameters were lamb liveweight at weaning per ewe joined and pre-mating liveweight. In addition, repeatability values were calculated across ages for these parameters. NRR was higher in the current year for those groups of ewes that reared lambs in the previous year; this was associated with the highly productive multiple-bearing and -rearing groups having a liveweight at the next mating similar compared to that of groups that did not rear lambs. Repeatability values of 0.27 for NRR and 0.40 for fertility suggest there are genetic and permanent environmental components contributing to the differences observed among the PRP groups for NRR, particularly so for fertility. Selecting ewes after their first lambing opportunity on fertility alone at a rate of 90% would give a non-cumulative increase in fertility of 3.4% at subsequent lambing opportunities. Hence, improvements in the current ewe flock for NRR by graziers managing flocks of the South Australian Merino strain are likely to come from (1) identifying and selecting those ewes of high fertility from early records and (2) attending to management factors impacting on fecundity and lamb survival.
3
Kleemann, DO, RW Ponzoni, JE Stafford e RJ Grimson. "Carcass composition of the South Australian Merino and its crosses with the Booroola and Trangie Fertility Merino". Australian Journal of Experimental Agriculture 28, n. 2 (1988): 167. http://dx.doi.org/10.1071/ea9880167.
Testo completoAbstract (sommario):
South Australian medium-wool (M), non- Peppin medium-wool Booroola (B) and Peppin medium-wool Trangie Fertility (TF) Merino rams were joined to M ewes at Turretfield Research Centre, South Australia, in 2 years. Carcass composition was assessed in the ewe and wether progeny at 2 mean slaughter liveweights, viz. 24 and 38 kg. When adjusted to the same carcass weight, B x M had 13% more carcass chemical fat, 15% more subcutaneous fat, 6% less bone and the same lean tissue as M. The same result was observed for TF x M in relation to M in year 2. However, TF x M had more lean and the same amount of subcutaneous and chemical fat as M in year 1. Within the Booroola strain, there were no differences between offspring from 3 sires with genotype FF and the 1 sire with + + for any of 5 variables analysed. We conclude that crossing the Booroola with the South Australian Merino produces carcasses with the same amount of lean tissue, less bone and more fat when compared at the same carcass weight. The rank of TF x M with the other strains for the major carcass components remains obscure owing to a strain x year interaction.
4
Barwick, S. A., D. J. Brown, B. R. Cullis, A. K. Bell, T. J. May, M. W. Lollback, I. M. Rogan et al. "The performance of the Border Leicester in Australia". Animal Production Science 61, n. 1 (2021): 1. http://dx.doi.org/10.1071/an19493.
Testo completoAbstract (sommario):
Aims We examine the average performance of Border Leicester (BL) flocks that are part of LAMBPLAN, Australia’s sheep performance recording and genetic evaluation system. We also summarise outcomes from the New South Wales Department of Primary Industry’s research on BL improvement, and discuss the performance required for the BL to continue to be a pivotal part of the Australian prime lamb industry. Key results Modest gains have been recorded in the BL in growth since 2000 and faecal egg counts have reduced, suggesting improved worm resistance. The net reproductive rate has slightly improved, while inbreeding continues to increase. In work conducted by the New South Wales Department of Primary Industries, an improved BL flock, encompassing selection for multiple births and a broadening of the breed’s genetic base, had advantages over purebred BLs in many aspects of performance, including a 19.3% advantage in the net reproductive rate. Advantages in fertility were ~5%, litter size ~7% and lamb rearing ability ~5%. BL improved × Merino and (BL improved × BL) × Merino crossbred ewes also had advantages over traditional BL × Merino ewes in their joining performance when joined to Dorset rams. Conclusions Selection in the BL needs to emphasise traits in a manner consistent with their importance to commercial lamb production. Implications Embracing this selection and broadening the BL’s genetic base will assist the BL to maintain its place in the Australian lamb industry.
5
Harrison, Matthew T., Karen M. Christie, Richard P. Rawnsley e Richard J. Eckard. "Modelling pasture management and livestock genotype interventions to improve whole-farm productivity and reduce greenhouse gas emissions intensities". Animal Production Science 54, n. 12 (2014): 2018. http://dx.doi.org/10.1071/an14421.
Testo completoAbstract (sommario):
Livestock greenhouse gas (GHG) emissions form the largest proportion of emissions from agriculture. Here we seek intervention strategies for sustainably intensifying the productivity of prime lamb enterprises without increasing net farm emissions. We apply a biophysical model and an emissions calculator to determine the implications of several interventions to a prime lamb farm in south-eastern Australia. We examine the effects of lamb liveweight or age at sale, weaning rate, maiden ewe joining age, genetic feed-use efficiency, supplementary grain feeding according to green pasture availability, soil fertility and botanical composition. For each intervention, stocking rates were optimised to the lesser of a minimum ground cover threshold or a maximum supplementary grain feeding threshold. Total animal production of the baseline farm was 478 kg clean fleece weight plus liveweight (CFW+LWT)/ha.annum and ranged from 166 to 609 kg CFW+LWT/ha.annum for interventions that replaced existing pastures with annual ryegrass or increased soil fertility respectively. Annual GHG emissions intensity of the baseline farm was 8.7 kg CO2-e/kg CFW+LWT and varied between 7.7 and 9.2 kg CO2-e/kg CFW+LWT for interventions that reduced maiden ewe joining age or increased sale liveweight, respectively. Stocking rate primarily governed total animal production, and in many cases production drove emissions, so interventions that increased production did not always reduce emissions intensity. Indeed, replacing existing perennial ryegrass/subterranean clover mixed pastures with perennial legume swards caused large reductions in both production and emissions, and interventions that increased soil fertility via phosphate addition caused large increases in production and emissions; as a consequence, both strategies had little effect on emissions intensity. Implementing several beneficial interventions simultaneously further increased production and reduced emissions intensity relative to implementing individual interventions alone. Baseline production increased by 61% by increasing soil fertility, improving feed-use efficiency and reducing the joining age of maiden ewes, while baseline emissions intensity was reduced by 17% by improving feed use efficiency, reducing the joining age of maiden ewes and supplementary grain feeding. We demonstrate that imposing several strategies on existing sheep farming systems simultaneously is more conducive to sustainable agricultural intensification than is imposing any single intervention alone, provided individual strategies were beneficial in their own right. The best strategies for both sustainably increasing production and reducing emissions intensity are those that decouple the linkage between production and emissions such as interventions that shift the balance of the flock away from adults and towards juveniles while holding average annual stocking rates constant.
6
Hinch, G. N., M. Lollback, S. Hatcher, J. Hoad, R. Marchant, D. F. Mackay e J. M. Scott. "Effects of three whole-farmlet management systems on Merino ewe fat scores and reproduction". Animal Production Science 53, n. 8 (2013): 740. http://dx.doi.org/10.1071/an12440.
Testo completoAbstract (sommario):
As part of the Cicerone Project’s whole-farmlet experiment on the Northern Tablelands of New South Wales, Australia, the fat scores and reproductive performance of ewes were measured to assess the effect of different management systems on these important production parameters over time. The three farmlets (each of 53 ha) included one (farmlet B) subjected to ‘typical’ district management consisting of moderate levels of inputs and a target stocking rate of 7.5 dse/ha, with flexible grazing management across eight paddocks. A second farmlet (A) was managed in a similar fashion to farmlet B with respect to number of paddocks and grazing management, but modified by high rates of pasture renovation and higher levels of soil fertility, with a target stocking rate of 15 dse/ha. The third farmlet (C) was managed at the same level of moderate inputs as farmlet B but employed intensive rotational grazing over 37 paddocks and also had a high target stocking rate of 15 dse/ha. The experiment was conducted over 6.5 years from July 2000 to December 2006. In spite of the fact that target levels of stocking rate were chosen at the beginning of the experiment, stocking rate, together with fat scores and reproduction were treated as emergent properties of each farmlet system. Joining took place in April–May and lambing occurred in September–October of each year. Over the first 2 years of the experiment, there were few differences among farmlets in ewe fat scores or reproductive performance. From 2003 onwards, while the percentage of ewes pregnant was similar between farmlets, the average proportion of multiple births (ewes scanned in late July, with twins) was 30%, 16% and 12%, respectively, on farmlets A–C. However, lamb losses were greater on farmlet A, with average lamb mortalities recorded on farmlets A–C of 29%, 10% and 19%, respectively. Over the duration of the experiment, ewes on farmlets A and B were more often above a fat score level of 3, and less often below 2.5, than were ewes from farmlet C. Differences among farmlet ewes in fat score were found to be significant in 7 of the total of 13 assessments over the duration of the experiment. A generalised additive model applied to whole-farmlet data showed that green digestible herbage, legume herbage, stocking rate, the amount of supplement fed and especially the proportion of each farmlet grazed at any one time all influenced fat scores of ewes. While fat scores and conception rates tended to be highest on farmlet A, farmlet B had slightly better reproductive outcomes due to less lambing losses, whereas ewes on farmlet C tended to have somewhat lower fat scores and levels of reproduction. These farmlet-scale findings highlighted the importance for livestock managers to focus not only on grazing management, stocking rate and stock density during lambing, but also on the availability of sufficient green, and especially legume herbage, and the difficulty of overcoming a deficit in quality herbage with supplementation.
7
Graham, J. F., B. R. Cullen, G. M. Lodge, M. H. Andrew, B. P. Christy, P. J. Holst, X. Wang, S. R. Murphy e A. N. Thompson. "SGS Animal Production Theme: effect of grazing system on animal productivity and sustainability across southern Australia". Australian Journal of Experimental Agriculture 43, n. 8 (2003): 977. http://dx.doi.org/10.1071/ea02197.
Testo completoAbstract (sommario):
The effects of various grazing management systems on sown, naturalised, and native pastures were studied at 6 different locations in the temperate high rainfall zone (HRZ, >600 mm rainfall/year) of southern Australia, as part of the Sustainable Grazing Systems (SGS) Program. The treatments examined had different pasture species and fertiliser management, with grazing method ranging from set stocking (continuous grazing) to rotation with rests based on pre- and post-grazing herbage mass or season and plant phenology. Sites were located at: Albany, Western Australia; Manilla, Barraba, Nundle, New South Wales; (grazed by wethers); and Carcoar, New South Wales; Maindample, Ruffy, north-east Victoria; Vasey, western Victoria; (grazed by ewes and lambs).Grazing method significantly (P<0.001) influenced stocking rate (expressed as dry sheep equivalents (DSE)/ha), but effects were not consistent across sites. At Vasey the stocking rate of the rotation treatments ranged from 5 to 23% higher than the set stocked treatments depending upon year. For all sites, significant factors (P<0.001) affecting stocking rate were soil Olsen P, soil pH, grazing management (resting), legume percent, and an index of growing season effectiveness. Although total annual rainfall had a significant effect (P<0.002) in an initial analysis, its influence became non-significant (P>0.05), when a growing season index (P<0.001) was used. Non-significant (P>0.05) factors included solar radiation, annual average temperature, fertiliser applied in the current year, and average annual perennial and broadleaf percent composition. The implications of these data for productivity and sustainability (as assessed by perenniality and water use) were encouraging. Generally, there were positive relationships between increased stocking rate and the probability of achieving a zero mm soil water surplus in winter, and between increased productivity and the proportion of perennial grass species where extremes of treatments were compared at each site. The results indicate that stocking rate can be increased without jeopardising sustainability, that grazing management can bring about more sustainable pastures, that there is scope to increase productivity particularly through increasing soil fertility, and growing season length can be used to predict potential carrying capacity. These are positive outcomes that graziers in the HRZ of southern Australia can use to enhance productivity (thus profitability) and sustainability.
8
Robertson, S. M. "Crop stubbles are as important for sheep production as annual pastures in the Victorian Mallee". Australian Journal of Experimental Agriculture 46, n. 8 (2006): 993. http://dx.doi.org/10.1071/ea04033.
Testo completoAbstract (sommario):
The impact of different management strategies on production and profit can be evaluated with knowledge of how sheep production responds to changes in the available feed base and sheep or pasture management. This study aimed to quantify on-farm pasture and sheep production in mixed sheep and cropping systems in the Victorian Mallee of south-eastern Australia (325 ± 50 mm annual rainfall) as a prelude to computer simulation modelling. During 2001 (average rainfall) and 2002 (extreme drought) pasture production, the feed base and sheep production were monitored in 15 paddocks on 5 properties located across the region. Crop stubbles were the major source of feed for 6 months of the year, enabling ewes to maintain liveweight. There was more variation in pasture parameters between paddocks at the 1 location than between locations. The botanical composition, plant density, soil fertility and management were key variables associated with between-paddock variation in pasture production. Variation in pasture production between years was larger than within-year differences. In contrast, stocking rates were not much lower in the drought year of 2002 than in 2001. This study suggests there is potential for management to improve pasture production, and demonstrates the importance of feed sources other than annual pasture for sheep production in environments where the annual pasture growing season is short.
9
Cottle, D., C. A. Gaden, J. Hoad, D. Lance, J. Smith e J. M. Scott. "The effects of pasture inputs and intensive rotational grazing on superfine wool production, quality and income". Animal Production Science 53, n. 8 (2013): 750. http://dx.doi.org/10.1071/an12289.
Testo completoAbstract (sommario):
A farmlet experiment was conducted between July 2000 and December 2006 as part of the Cicerone Project, which sought to enhance the profitability and sustainability of grazing enterprises on the Northern Tablelands of New South Wales, Australia. A self-replacing Merino enterprise was grazed as the dominant livestock enterprise, together with ~20% of the carrying capacity as cattle, on each of three farmlet treatments: higher levels of soil fertility and pasture renovation with flexible rotational grazing over eight paddocks (farmlet A), moderate soil fertility and pasture renovation with flexible rotational grazing over eight paddocks (farmlet B) and moderate soil fertility and pasture renovation with intensive rotational grazing over 37 paddocks (farmlet C). Prior to commencement of the trial, the three 53-ha farmlets were allocated equivalent areas of land based on soil type, slope and recent fertiliser history. This paper describes the effects of the three pasture and grazing management strategies on the production, quality and value of the wool produced per head, per ha and per farmlet. Up until 2001 there were no differences in wool production between farmlets. Thereafter, significant differences between farmlets emerged in greasy fleece weight per head and price received per kg of fleece wool. For example, the clean fleece value averaged over the 2003–05 shearings for all hoggets, ewes and wethers was 1531, 1584 and 1713 cents/kg for farmlets A, B and C, respectively. There were small but significant differences, which varied between sheep class and year, between the farmlets in average fibre diameter and staple length but less so with staple strength. In general, while the differences between farmlets in staple strength varied over time, farmlets A and B tended to have wool with longer staple length and broader fibre diameter than farmlet C and this affected wool value per kg. Differences in wool income per ha between farmlets grew in later years as the farmlet treatments took effect. In spite of farmlet A having a slightly lower wool value per kg, after taking into account its greater fleece weight per head and its higher stocking rate, the total wool income per ha was higher than on either farmlets B or C. The average gross wool income per ha from 2003 to 2005 was $303, $215 and $180 for farmlets A, B and C, respectively. The highest amount of greasy wool produced was in 2004 when 38.2, 26.5 and 21.5 kg/ha was harvested from farmlets A, B and C, respectively. The fibre diameter profiles of 2-year-old ewes showed similar profiles for farmlets A and B but a significantly finer fibre diameter profile for farmlet C ewes due to intensive rotational grazing. However, sheep on all three farmlets produced wool with high staple strength. Multivariate analyses revealed that greasy fleece weight, staple length and staple strength were significantly positively correlated with the proportion of the farm grazed at any one time, and with soil phosphorus, legume herbage and green digestible herbage thus highlighting the significant influence of pasture and soil inputs and of grazing management on wool production and quality.
10
Kleemann, DO, RW Ponzoni, JE Stafford, IN Cutten e RJ Grimson. "Growth and carcass characters of the South Australian Merino and its crosses with the Booroola and Trangie Fertility Merino". Australian Journal of Experimental Agriculture 25, n. 4 (1985): 750. http://dx.doi.org/10.1071/ea9850750.
Testo completoAbstract (sommario):
South Australian Merino (M) and highly fecund Booroola (B) and Trangie Fertility (TF) Merino strain rams were mated to M ewes to produce M, B x M and TF x M progeny. At 4-5 months of age (24-kg slaughter group), TF x M and M lambs were heavier than B x M lambs (25.3 and 24.8 kg respectively, v. 228 kg). Similar proportional strain differences were observed at 14-1 5 months of age (38-kg slaughter group), except that, in one year, no difference was observed between the M and B x M strains, resulting in a strain x year interaction (P<0.05). When adjusted for age, TF x M carcasses were heavier than those of B x M at the first slaughter and heavier than those of B x M and M strains at the second slaughter. B x M and TF x M strains had the same fat depths and eye muscle areas, when compared at the same age, but B x M had greater fat depths and larger eye muscle areas than TF x M, relative to carcass weight; values for M were less than those of B x M and TF x M, with and without carcass weight as a covariate. Similarly, ranking of the strains did not change for carcass length, leg length and depth of thorax with and without carcass weight as a covariate. Carcasses of M lambs were longer than those of B x M, TF x M being intermediate. No differences were observed among progeny of FF and + + Booroola sires for the 12 variables measured. We conclude that carcasses of B x M and TF x M high fecundity cross Merino strains have greater depths of fat at both the same age and same carcass weight than those of the South Australian Merino, and suggest that the effect of the Booroola F gene on the characters measured is negligible. The implications of the results to the sheep industry are discussed.
Tesi sul tema "Ewes South Australia Fertility"
1
Nottle, Mark Brenton. "Short-term nutrition and its effect on ovulation in the ewe". Title page, table of contents and summary only, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phn921.pdf.
Testo completo
2
Nottle, Mark Brenton. "Short-term nutrition and its effect on ovulation in the ewe / by Mark Brenton Nottle". Thesis, 1988. http://hdl.handle.net/2440/19113.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 143-165)xiii, 168 leaves : ill. (some col.) ; 30 cm.
Reports on studies undertaken to examine the physiological basis of the known ability of lupin grain to increase ovulation rate in the ewe.
Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Sciences, Waite Agricultural Research Institute, 1989
3
Faulkner, Deborah Robyn. "The spatial dynamics of fertility in South Australia 1976 to 1996". 2005. http://hdl.handle.net/2440/37832.
Testo completoAbstract (sommario):
In the past the identification and explanation of spatial variations in fertility was seen as an important contribution to the field of population geography. By the 1980s with the substantial declines in fertility and the ' end ' of the demographic transition came the belief low fertility equated with little variation between groups and across space. Recent evidence however suggests the interaction of various factors including place - specific factors has led to spatio - temporal changes in fertility that have not been expected based on theoretical and national patterns of fertility. The objective of this thesis was to investigate if spatial differentials in fertility still exist, and have relevance in a low fertility setting. The study examines the geography of fertility in the State of South Australia from the mid 1970s to the mid 1990s using unpublished issue data from the 1976, 1981, 1986 and 1996 Australian Censuses for women aged 45 - 49 years and 15 - 44 years. In addition to identifying the patterns trends towards convergence or divergence in the patterns over time and the reasons for the patterns were also identified. The findings of this study indicate strong spatial variations in fertility still exist, have persisted over time and there are localised conditions which temper overall expectations from theory. While it is assumed declines in fertility equate with a convergence in differentials, the statistical parameters used in this study showed trends towards convergence or divergence varied by geographical scale and age group. Despite the limited attention socio - economic factors have received in the examination of population issues in Australia, they remain central to explaining the fertility patterns and trends found in this study. In fact in metropolitan Adelaide fertility may be a significant contributor and influence on social polarisation.Thesis (Ph.D.)--School of Social Sciences, 2005.
4
Faulkner, Deborah Robyn. "The spatial dynamics of fertility in South Australia 1976 to 1996". Thesis, 2005. http://hdl.handle.net/2440/37832.
Testo completoAbstract (sommario):
In the past the identification and explanation of spatial variations in fertility was seen as an important contribution to the field of population geography. By the 1980s with the substantial declines in fertility and the ' end ' of the demographic transition came the belief low fertility equated with little variation between groups and across space. Recent evidence however suggests the interaction of various factors including place - specific factors has led to spatio - temporal changes in fertility that have not been expected based on theoretical and national patterns of fertility.
The objective of this thesis was to investigate if spatial differentials in fertility still exist, and have relevance in a low fertility setting. The study examines the geography of fertility in the State of South Australia from the mid 1970s to the mid 1990s using unpublished issue data from the 1976, 1981, 1986 and 1996 Australian Censuses for women aged 45 - 49 years and 15 - 44 years. In addition to identifying the patterns trends towards convergence or divergence in the patterns over time and the reasons for the patterns were also identified.
The findings of this study indicate strong spatial variations in fertility still exist, have persisted over time and there are localised conditions which temper overall expectations from theory. While it is assumed declines in fertility equate with a convergence in differentials, the statistical parameters used in this study showed trends towards convergence or divergence varied by geographical scale and age group. Despite the limited attention socio - economic factors have received in the examination of population issues in Australia, they remain central to explaining the fertility patterns and trends found in this study. In fact in metropolitan Adelaide fertility may be a significant contributor and influence on social polarisation.Thesis (Ph.D.)--School of Social Sciences, 2005.
5
Ladd, Brenton M. "The intensity of competitive interactions as a function of fertility, in Mediterranean-type old fields in South Australia / Brenton Ladd". 2003. http://hdl.handle.net/2440/21985.
Testo completoAbstract (sommario):
"April 22, 2003"Bibliography: leaves 131-147.
147 leaves : ill., 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Studies the establishment of tree seedlings in Mediterranean-type oldfields in South Australia to test for a correlation between habitat fertility and the intensity of competition. Also investigates whether resource competition and invertebrate herbivory are confounded with each other. Testing for correlation was carried out using a quantitative literature review in combination with field and glasshouse experiments. Results suggest that direct effects,and indirect effects may be heavily confounded, and that a positive correlation between fertility and the intensity of competition is most probable when a phenomenological definition of competition is used.
Thesis (Ph.D.)--University of Adelaide, School of Environmental Engineering, 2003
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Ladd, Brenton Mark. "The intensity of competitive interactions as a function of fertility, in Mediterranean-type old fields in South Australia / Brenton Ladd". Thesis, 2003. http://hdl.handle.net/2440/21985.
Testo completoAbstract (sommario):
"April 22, 2003"Bibliography: leaves 131-147.
147 leaves : ill., 30 cm.
Studies the establishment of tree seedlings in Mediterranean-type oldfields in South Australia to test for a correlation between habitat fertility and the intensity of competition. Also investigates whether resource competition and invertebrate herbivory are confounded with each other. Testing for correlation was carried out using a quantitative literature review in combination with field and glasshouse experiments. Results suggest that direct effects,and indirect effects may be heavily confounded, and that a positive correlation between fertility and the intensity of competition is most probable when a phenomenological definition of competition is used.
Thesis (Ph.D.)--University of Adelaide, School of Environmental Engineering, 2003
Libri sul tema "Ewes South Australia Fertility"
1
Institute, International Rice Research, a cura di. Efficiency of nitrogen fertilizers for rice: Proceedings of the Meeting of the International Network on Soil Fertility and Fertilizer Evaluation for Rice, Griffith, New South Wales, Australia, 10-16 April 1985. Los Baños, Laguna, Philippines: International Rice Research Institute, 1987.
Cerca il testo completoCapitoli di libri sul tema "Ewes South Australia Fertility"
1
Ponzoni, R. W., S. K. Walker, J. R. W. Walkley e M. R. Fleet. "The productivity of Bungaree, Booroola × Bungaree and Trangie Fertility × Bungaree Merino ewes in South Australia". In Genetics of Reproduction in Sheep, 127–37. Elsevier, 1985. http://dx.doi.org/10.1016/b978-0-407-00302-6.50017-9.
Testo completo
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Narayan, Edward, Gregory Sawyer, Natalie Hoskins e Greg Curren. "Reproductive Rates of Merino Ewes and Offspring Quality under AI Program". In Sheep Farming [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99617.
Testo completoAbstract (sommario):
Reproductive wastage is a major economic burden in sheep production globally, especially within Australia as livestock production systems face increased pressure from climatic variability (e.g. prolonged droughts or flooding). Sheep are sensitive to acute changes in their environment such as heat stress, which if not adequately monitored will result in significant production losses such as reproductive failure, increased parasite and worm burden, morbidity and mortality risks. Through basic and applied research in the areas of stress and reproductive physiology our team has made significant advancements in the understanding of sheep behaviour and physiological responses to acute and chronic stressors. Using minimally invasive hormone monitoring technology in combination with field based assessment of sheep health and productivity traits, our team has delivered new knowledge on how sheep react to acute environmental stress and how it impacts on sheep reproduction. In this chapter, we evaluated the fertility rates and embryo quality of Merino ewes under AI breeding program. We discuss factors such as heat stress that can impact on ewe and offspring quality.
3
Chu, C. Y. Cyrus. "Demographic Transition and Economic Development". In Population Dynamics. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195121582.003.0016.
Testo completoAbstract (sommario):
Demographic transition refers to a shift in reproductive behavior from a state of high birth and death rates to a state of low birth and death rates. This transition takes place because of advances in agricultural technology and medical science or improvement in hygiene environment, all of which result in corresponding declines in the mortality rate. In this first phase of the demographic transition, population growth rises because the decline in mortality rate has not been coupled with any significant change in parents’ fertility decisions. Then, in the second phase of the transition, parents begin to reduce their fertility as they realize that their ideal number of children can be more easily achieved with fewer births. The widespread use of contraceptive techniques facilitates parents’ attempts to reduce fertility, which in turn causes a decline in the population growth rate. Eventually, the population growth rate converges to a new level, which may be higher or lower than in the pretransitional stage. To facilitate comparison, we can use figure 11.1 to characterize the time and process of the transition. In figure 11.1, Tα marks the apparent starting point of a continuous decline in mortality. Tβ, which normally occurs later than Tα, refers to the time at which the fertility rate begins to decline. Tγ, is the point of lasting return, with an average rate of natural increase equal to or less than that of the period preceding the date of Tα. The convention is to define D = Tγ - Tα as the duration of the transition period. Chesnais (1992) separated the observations of world demographic transition into several types. The first type includes developed countries in Europe and Japan; the second type consists of countries with immigrant European populations, such as the United States, Australia, and Argentina; late-developing countries, such as India. South Korea, and Jamaica, belong to the third type. For countries of the first type, the mortality decline process is closely related to the development of medical technology, which was gradual and spread out over time; hence, the demographic transition is also long. Late-developing countries and those with large immigrant populations were able to adopt the already-developed medical technology from the advanced countries at one time.
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Haridasan, M. "Nutrient Cycling as a Function of Landscape and Biotic Characteristics in the Cerrados of Central Brazil". In The Biogeochemistry of the Amazon Basin. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195114317.003.0008.
Testo completoAbstract (sommario):
The cerrados of central Brazil have long been designated savannas without sufficient understanding of the structure and functioning of the different vegetation forms in the region. Excessive emphasis on identifying similarities with other savannas in Africa and Australia, and even within South America outside Brazil, prevented researchers from recognizing the cerrados’ special features and interdependence among themselves in the landscape where they occur. The more extensive cerrado sensu stricto on dystrophic soils, and to a lesser extent the gallery forests known locally as matas de galeria or matas ciliares, dominated the attention of most botanists and other researchers (Ratter and Dargie 1992, Furley 1992, Furley and Ratter 1988, Furley et al. 1992). Even with increasing interest in biodiversity and ecosystem functioning, very little ongoing research is reported on nutrient cycling from the cerrado region (Solbrig et al. 1996). Information available in the literature is restricted to isolated attempts to describe and quantify specific processes like litterfall and decomposition (Peres et al. 1983), rainwater composition (Schiavini 1983, Delitti 1984), soil fertility gradients (Lopes and Cox 1977), leaf nutrient concentrations (Haridasan 1987, 1992, Araújo and Haridasan 1988), primary productivity of the ground layer (Batmanian and Haridasan 1985, Meirelles and Henrique 1992), effects of burning (Coutinho 1990, Kauffman et al. 1994, Miranda et al. 1996c) and activities of soil fauna (Constantino 1988, Egler and Haridasan 1987, Oliveira Jr. 1985) at specific sites within a particular vegetation. Results of long duration experiments from permanent plots or watersheds are not yet reported in the literature. Very little information is available on the food webs or the role of fauna in nutrient cycling. Research on specific processes like CO2 emission on an ecosystem basis is quite recent (Miranda et al. 1996a, b, Mier et al. 1996). The following discussion is therefore restricted to the occurrence of different vegetation forms in the cerrado region and environmental factors affecting their distribution and functioning in relation to nutrient availability and nutrient cycling processes. One of the difficulties in getting information on research already carried out in Brazil is that the dissertations of graduate students in the universities are seldom published in indexed journals.
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Schlesinger, William H., e Sandy L. Tartowski. "Nutrient Cycling within an Arid Ecosystem". In Structure and Function of a Chihuahuan Desert Ecosystem. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195117769.003.0010.
Testo completoAbstract (sommario):
Low quantities of soil nitrogen limit plant growth in the Chihuahuan Desert (Ettershank et al. 1978; Fisher et al. 1988; Lajtha and Whitford 1989; Mun and Whitford 1989) and in other deserts of the world (Wallace et al. 1980; Breman and de Wit 1983; Sharifi et al. 1988; Link et al. 1995). Indeed, although deserts are often regarded as water-limited systems, colimitation by water and N may be the more general rule (Hooper and Johnson 1999; Austin and Sala 2002). In a broad survey of desert ecosystems, Hooper and Johnson (1999) found evidence for colimitation by water and N even at the lowest levels of rainfall. In arid ecosystems, water is delivered in discrete events separated by drier periods, which restrict biological activity and uncouple plant uptake of nutrients from decomposition. Local variations in net primary production in arid and semiarid ecosystems are largely determined by processes that control the redistribution of water and soil nutrients across the landscape (Noy-Meir 1985; Schlesinger and Jones 1984; Wainwright et al. 2002; see also chapter 11). In this chapter we focus on the N cycle in different plant communities of the Jornada Basin with the recognition that after water, N is the most likely resource to determine the plant productivity of this ecosystem. Where arid environments are dominated by shrubby vegetation, the distribution of soil properties is markedly patchy with strong accumulations of plant nutrients under shrubs and relatively infertile soils in the intershrub spaces (Noy-Meir 1985). These islands of fertility are particularly well described in the Chihuahuan Desert and other areas of the American Southwest. Local accumulations of nutrients under vegetation are also documented for desert habitats on other continents, including Europe (Gallardo et al. 2000), Africa (Gerakis and Tsangarakis 1970; Belsky et al. 1989; Wezel et al. 2000), Australia (Tongway and Ludwig 1994; Facelli and Brock 2000), and South America (Rostagno et al. 1991; Mazzarino et al. 1991, 1998; Gutierrez et al. 1993). In the Jornada Basin, Schlesinger et al. (1996) used geostatistics to compare the scale of soil heterogeneity in arid habitats dominated by shrubs and in adjacent areas of arid grassland.