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Dominik, Sonja
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Given Name
Sonja
Sonja
Surname
Dominik
UNE Researcher ID
une-id:sdomini2
Email
sdomini2@une.edu.au
Preferred Given Name
Sonja
School/Department
School of Environmental and Rural Science
11 results
Now showing 1 - 10 of 11
- PublicationAccuracy of estimated genomic breeding values for wool and meat traits in a multi-breed sheep population(CSIRO Publishing, 2010)
; ; Hayes, B JEstimated breeding values for the selection of more profitable sheep for the sheep meat and wool industries are currently based on pedigree and phenotypic records. With the advent of a medium-density DNA marker array, which genotypes ~50 000 ovine single nucleotide polymorphisms, a third source of information has become available. The aim of this paper was to determine whether this genomic information can be used to predict estimated breeding values for wool and meat traits. The effects of all single nucleotide polymorphism markers in a multi-breed sheep reference population of 7180 individuals with phenotypic records were estimated to derive prediction equations for genomic estimated breeding values (GEBV) for greasy fleece weight, fibre diameter, staple strength, breech wrinkle score, weight at ultrasound scanning, scanned eye muscle depth and scanned fat depth. Five hundred and forty industry sires with very accurate Australian sheep breeding values were used as a validation population and the accuracies of GEBV were assessed according to correlations between GEBV and Australian sheep breeding values. The accuracies of GEBV ranged from 0.15 to 0.79 for wool traits in Merino sheep and from –0.07 to 0.57 for meat traits in all breeds studied. Merino industry sires tended to have more accurate GEBV than terminal and maternal breeds because the reference population consisted mainly of Merino haplotypes. The lower accuracy for terminal and maternal breeds suggests that the density of genetic markers used was not high enough for accurate across-breed prediction of marker effects. Our results indicate that an increase in the size of the reference population will increase the accuracy of GEBV. - PublicationImpact of young ewe fertility rate on risk and genetic gain in sheep-breeding programs using genomic selectionGenomic selection could be useful in sheep-breeding programs, especially if rams and ewes are first mated at an earlier age than is the current industry practice. However, young-ewe (1 year old) fertility rates are known to be lower and more variable than those of mature ewes. The aim of the present study was to evaluate how young-ewe fertility rate affects risk and expected genetic gain in Australian sheep-breeding programs that use genomic information and select ewes and rams at different ages. The study used stochastic simulation to model different flock age structures and young-ewe fertility levels with and without genomic information for Merino and maternal sheep-breeding programs. The results from 10 years of selection were used to compare breeding programs on the basis of the mean and variation in genetic gain. Ram and ewe age, availability of genomic information on males and young-ewe fertility level all significantly (P < 0.05) affected expected genetic gain. Higher young-ewe fertility rates significantly increased expected genetic gain. Low fertility rate of young ewes (10%) resulted in net genetic gain similar to not selecting ewes until they were 19 months old and did not increase breeding-program risk, as the likelihood of genetic gain being lower than the range of possible solutions from a breeding program with late selection of both sexes was zero. Genomic information was of significantly (P < 0.05) more value for 1-year-old rams than for 2-year-old rams. Unless genomic information was available, early mating of rams offered no greater gain in Merino breeding programs and increased breeding-program risk. It is concluded that genomic information decreases the risk associated with selecting replacements at 7 months of age. Genetic progress is unlikely to be adversely affected if fertility levels above 10% can be achieved. Whether the joining of young ewes is a viable management decision for a breeder will depend on the fertility level that can be achieved in their young ewes and on other costs associated with the early mating of ewes.
- PublicationDesign and phenotyping procedures for recording wool, skin, parasite resistance, growth, carcass yield and quality traits of the SheepGENOMICS mapping flock(CSIRO Publishing, 2012)
; ; ; - PublicationGenetic parameters for methane emissions in Australian sheep measured in portable accumulation chambers in grazing and controlled environments(CSIRO Publishing, 2022-03-10)
; ; ; ; ; ; Context. Genotype by environment interaction or sire re-ranking between measurements of methane emission in different environments or from using different measurement protocols can affect the efficiency of selection strategies to abate methane emission. Aim. This study tested the hypothesis that measurements of methane emission from grazing sheep under field conditions, where the feed intake is unknown, are genetically correlated to measurements in a controlled environment where feed intake is known. Methods. Data on emission of methane and carbon dioxide and uptake of oxygen were measured using portable accumulation chambers from 499 animals in a controlled environment in New South Wales and 1382 animals in a grazing environment in Western Australia were analysed. Genetic linkage between both environments was provided by 140 sires with progeny in both environments. Multi-variate animal models were used to estimate genetic parameters for the three gas traits corrected for liveweight. Genetic groups were fitted in the models to account for breed differences. Genetic correlations between the field and controlled environments for the three traits were estimated using bivariate models. Key results. Animals in the controlled environment had higher methane emission compared to the animals in the field environment (37.0 ± s.d 9.3 and 35.3 ± s.d 9.4 for two protocols vs 12.9 ± s.d 5.1 and 14.6 ± s.d 4.8 mL/min for lambs and ewes (±s.d); P < 0.05) but carbon dioxide emission and oxygen uptake did not significantly differ. The heritability estimates for methane emission, carbon dioxide emission and oxygen uptake were 0.15, 0.06 and 0.11 for the controlled environment and 0.17, 0.27 and 0.35 for the field environment. The repeatability for the traits in the controlled environment ranged from 0.51 to 0.59 and from 0.24 to 0.38 in the field environment. Genetic correlations were high (0.85–0.99) but with high standard errors. Conclusion. Methane emission phenotypes measured using portable accumulation chambers in grazing sheep can be used in genetic evaluation to estimate breeding values for genetic improvement of emission related traits. The combined measurement protocol-environment did not lead to re-ranking of sires. Implication. These results suggest that both phenotypes could be used in selection for reduced methane emission in grazing sheep. However, this needs to be consolidated using a larger number of animals and sires with larger progeny groups in different environments.
- PublicationAge at First Oestrus. A Useful Trait for Early Reproductive Performance?(Association for the Advancement of Animal Breeding and Genetics (AAABG), 2013)
; ; ; An increasing number of Australian sheep breeders are joining ewes at 6-8 months of age, which is 6-12 months earlier than ewes are traditionally first joined. When joining at a young age, additional factors such as the attainment of sexual maturity must be considered. The age of sexual maturity is a challenging trait to measure with limited data currently available in sheep. This study explored several methods of analyzing age of first oestrus (AFO) data, an indicator trait for sexual maturity, and explored the relationship between AFO and early reproductive performance. Lambing records from 2218 Maternal-cross ewes joined naturally at 7-10 months were used, a subset of 906 ewes had AFO information collected through the use of teaser wethers. Heritability estimates for AFO were low (0.03 - 0.09) whilst estimates for number of lambs born and weaned at yearling age were 0.20 and 0.16 respectively. Genetic correlation between AFO and number of lambs born and weaned at yearling age were 0.45 and 0.51, respectively, but had high standard errors. Improving reproductive performance through the use of teasers to record AFO is not recommended, thus a need exists to find reliable measures for early reproductive traits including sexual maturity. - PublicationExploring Genotype x Environment Interaction and Heritabilities for a Reproduction Trait in Merino Sheep Using Three Approaches(American Society of Animal Science, 2014)
; ; - PublicationThe value of genomic selection for stud and commercial Merino rams(Association for the Advancement of Animal Breeding and Genetics (AAABG), 2011)
; ; The additional value that can be gained from selecting stud and commercial rams based on genomic information was evaluated for Merino studs using two different breeding objectives. Selection index theory and gene flow methodology were used to contrast the accuracies and selection responses of indexes using phenotype information only, with those using additional genomic information of either high or low accuracy and selecting males at one year of age. With the inclusion of genomic information and earlier selection index accuracies increased and an additional 11-64% in commercial dollar value per ram could be gained from genetic improvement. The breakeven point for DNA testing was evaluated to be between $13.04 and $64.48, depending on the breeding objective and the accuracy of the genomic information. - PublicationGenetic and phenotypic parameters between yearling, hogget and adult reproductive performance and age of first oestrus in sheepThe aims of this study were to quantify the relationship between age of first oestrus and yearling reproductive performance in maternal-cross ewes in the Information Nucleus Flock data and to estimate genetic and phenotypic correlations between early and later reproductive performance defined as three ages, yearling, hogget and adult in both Merino and maternal-cross ewes. Information on 2218 yearling records, 2047 hogget records and 910 age of first oestrus records were used in the analysis of maternal-cross ewes, whereas 3286 hogget and 2518 adult reproductive records were used in analysis of Merino ewes. Heritability estimates for yearling reproductive performance in maternal-cross ewes ranged from 0.08 ± 0.09 for ewe fecundity to 0.16 ± 0.05 for number of lambs born and were generally higher than hogget heritability estimates for both maternal-cross and Merino ewes. Age at first oestrus was found to have a low heritability, 0.02 with standard errors of 0.07 and 0.06 with and without weight fitted as a covariate. Genetic correlations between age at first oestrus with and without weight fitted as a covariate and yearling reproductive performance were positive, ranging from 0.07 ± 0.49 with lamb survival to 0.94 ± 0.39 with number of lambs born, which was unexpected. Correlations between traits from the same age class were high in both breed groups. Genetic correlations between yearling and hogget performance in maternal-cross ewes were generally lower than one, ranging from 0.46 ± 0.68 for lamb survival and 0.79 ± 0.50 for fertility suggesting that yearling and later reproductive performance are related but genetically different traits. In Merino ewes, the genetic correlations between hogget and adult performance followed a similar pattern. The small number of records in this study generated high standard errors for estimates, which restricts the conclusions that can be drawn. Overall, this study supports current practice used by 'Sheep Genetics', the Australian genetic evaluation system for sheep, in considering yearling reproductive performance as a trait separate from later parities for genetic evaluation purposes.
- PublicationIs there a relationship between temperament and internal parasite resistance in Merinos?(Association for the Advancement of Animal Breeding and Genetics (AAABG), 2011)
; - PublicationSexual maturity and yearling reproductive performance in ewes: Genetic analysis and implications for breeding programs(2016)
; ; ; Bunter, KimThe successful breeding of ewes before the age of 12 months presents an opportunity to improve flock reproduction efficiency and increase returns for sheep producers. However, uptake of this practice is currently low in Australia and New Zealand. A contributing factor to this is that reproductive performance at 1 year of age is lower and more variable than in older ewes; between flocks and also from year to year. Whilst previous research has explored what factors contribute to successful reproduction at 1 year of age, there is no universally accepted measure of puberty and sexual maturity in sheep nor is there an accurate phenotypic predictor of yearling reproductive success. Although established genetic correlations between reproduction and production traits exist, reproduction has previously been analysed as a repeated records trait across parities, rather than treating first parity as a separate trait. Model studies show that genomic information offers the opportunity to select animals more accurately at younger ages. However the implications of a lower and more variable fertility rate of ewes mated prior to 1 year of age has been largely ignored. The aim of this thesis was to evaluate the impact of mating ewes prior to 1 year of age on flock genetic progress and to quantify the relationship between potential pubertal traits, yearling reproduction traits, reproduction traits at later parities and other key production traits.