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G D Snowder - One of the best experts on this subject based on the ideXlab platform.
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Genetic improvement of overall reproductive success in sheep: A review
Archivos Latinoamericanos de Producción Animal, 2020Co-Authors: G D SnowderAbstract:Reproduction is an economically important complex composite trait in sheep. Genetic improvement of composite traits can occur by selection for individual components traits, some combination of individual component traits, or by direct selection for the composite trait. This review discusses the responses of selecting directly for Litter Weight weaned compared to selection responses for one of its component traits. Litter Weight weaned is concluded to be a biological selection index determined by environmental factors under which it is selected for. Selection for Litter Weight weaned can result in a balanced biological composite trait with favorable responses in component traits such as fertility, number of lambs born, lamb survival, lactation, and lamb growth. It is concluded that selection to improve reproductive efficiency under most production and environmental systems would benefit from selection for a composite trait such as Litter Weight weaned rather than for a single component trait.
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Composite trait selection to improve reproduction and ewe productivity: a review
Animal Production Science, 2009Co-Authors: G D Snowder, N. M. FogartyAbstract:Reproduction and ewe productivity are complex composite traits that are influenced by several component traits. Genetic improvement by selection for an individual component trait may not always be advantageous because adverse or neutral genetic relationships can exist among the component traits. Selection for an overall composite trait of ewe productivity, defined as Litter Weight weaned per ewe joined, can result in a balanced biological composite trait with favourable responses in component traits including fertility, number of lambs born, lamb survival, lactation and lamb growth. Selection for Litter Weight weaned may also overcome adverse genetic relationships among reproductive component traits. This review examines the genetic responses of selecting directly for Litter Weight weaned, compared with selection responses for one or more of its component traits. It is concluded that selection to improve reproductive efficiency and ewe productivity, under most production and environmental systems, would benefit from selection for a composite trait such as Litter Weight weaned, rather than for a single component trait.
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genetic relationship between milk score and Litter Weight for targhee columbia rambouillet and polypay sheep
Journal of Animal Science, 2005Co-Authors: R M Sawalha, G D Snowder, Jeffrey F Keown, L D Van VleckAbstract:This study was conducted to evaluate the relationship between milk score (MS) and Litter Weight at 70 d (LW) for four sheep breeds in the United States. Milk score is a subjective measure of milk production used to assess milk production of range ewes when milk yield cannot be quantitatively determined. Variance components for MS and LW were estimated for each of Targhee, Columbia, Rambouillet, and Polypay breeds. Data collected from 1990 through 2000 at the U.S. Sheep Exp. Stn. in Dubois, ID, were analyzed with an animal model using REML. There were 13,900 records of MS and LW for 5,807 ewes. Records were grouped according to parity as first, second, and greater (mature), and all records (lifetime). Estimates of heritability for MS were in the range of 0.05 to 0.18 for first, 0.01 to 0.27 for second, 0.05 to 0.10 for mature, and 0.08 to 0.13 for all lifetime parity groups. Estimates of genetic correlation between MS at first and second parities ranged from 0.74 to 1.00. Similarly, mature MS was highly correlated genetically with MS at first (0.83 to 1.00) and at second (0.60 to 1.00) parities, suggesting that additive genetic value for milking ability at maturity could be evaluated as early as at first parity. Heritability estimates for LW ranged from 0.00 to 0.18 over all breeds and parity groupings. The genetic correlation between LW at first and second parity groups ranged from 0.43 to 1.00. Estimates of genetic correlation between LW at first or second parity with mature LW were mostly high and positive, except for Targhee (-0.10) and Polypay (0.14) at first parity. Litter Weight for mature ewes could be improved by selection at first or second parity. Estimates of genetic correlation at first parity between MS and LW were high (1.00) for Rambouillet and Polypay, and near zero for Columbia and Targhee. At second parity, estimates of genetic correlation between MS and LW were positive and moderate for Rambouillet and Polypay but more variable for Columbia and Targhee. Estimates of genetic correlation between MS and LW were mostly positive and may be favorable with smaller estimates of standard errors using all lifetime records rather than first or second parity records. Although estimates are variable, the average of the estimates of the genetic correlation suggests that LW can be improved by selecting ewes for favorable MS.
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genetic correlations for Litter Weight weaned with growth prolificacy and wool traits in columbia polypay rambouillet and targhee sheep
Journal of Animal Science, 2001Co-Authors: C M Bromley, L D Van Vleck, G D SnowderAbstract:Total Litter Weight weaned at 120 d postpartum per ewe lambing is often believed to be a measure of range ewe productivity. Genetic correlations for Litter Weight weaned at 120 d with prolificacy, growth, and wool traits for Columbia, Polypay, Ram- bouillet, and Targhee sheep were estimated using REML with animal models. Observations per breed ranged from 5,140 to 7,083 for Litter Weight weaned, from 5,140 to 7,095 for prolificacy traits, from 7,750 to 9,530 for growth traits, and from 4,603 to 18,443 for wool traits. Heritability estimates for Litter Weight weaned were low and ranged from 0.02 to 0.11. Fraction of variance due to permanent environmental effects av-
L D Van Vleck - One of the best experts on this subject based on the ideXlab platform.
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genetic relationship between milk score and Litter Weight for targhee columbia rambouillet and polypay sheep
Journal of Animal Science, 2005Co-Authors: R M Sawalha, G D Snowder, Jeffrey F Keown, L D Van VleckAbstract:This study was conducted to evaluate the relationship between milk score (MS) and Litter Weight at 70 d (LW) for four sheep breeds in the United States. Milk score is a subjective measure of milk production used to assess milk production of range ewes when milk yield cannot be quantitatively determined. Variance components for MS and LW were estimated for each of Targhee, Columbia, Rambouillet, and Polypay breeds. Data collected from 1990 through 2000 at the U.S. Sheep Exp. Stn. in Dubois, ID, were analyzed with an animal model using REML. There were 13,900 records of MS and LW for 5,807 ewes. Records were grouped according to parity as first, second, and greater (mature), and all records (lifetime). Estimates of heritability for MS were in the range of 0.05 to 0.18 for first, 0.01 to 0.27 for second, 0.05 to 0.10 for mature, and 0.08 to 0.13 for all lifetime parity groups. Estimates of genetic correlation between MS at first and second parities ranged from 0.74 to 1.00. Similarly, mature MS was highly correlated genetically with MS at first (0.83 to 1.00) and at second (0.60 to 1.00) parities, suggesting that additive genetic value for milking ability at maturity could be evaluated as early as at first parity. Heritability estimates for LW ranged from 0.00 to 0.18 over all breeds and parity groupings. The genetic correlation between LW at first and second parity groups ranged from 0.43 to 1.00. Estimates of genetic correlation between LW at first or second parity with mature LW were mostly high and positive, except for Targhee (-0.10) and Polypay (0.14) at first parity. Litter Weight for mature ewes could be improved by selection at first or second parity. Estimates of genetic correlation at first parity between MS and LW were high (1.00) for Rambouillet and Polypay, and near zero for Columbia and Targhee. At second parity, estimates of genetic correlation between MS and LW were positive and moderate for Rambouillet and Polypay but more variable for Columbia and Targhee. Estimates of genetic correlation between MS and LW were mostly positive and may be favorable with smaller estimates of standard errors using all lifetime records rather than first or second parity records. Although estimates are variable, the average of the estimates of the genetic correlation suggests that LW can be improved by selecting ewes for favorable MS.
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genetic correlations for Litter Weight weaned with growth prolificacy and wool traits in columbia polypay rambouillet and targhee sheep
Journal of Animal Science, 2001Co-Authors: C M Bromley, L D Van Vleck, G D SnowderAbstract:Total Litter Weight weaned at 120 d postpartum per ewe lambing is often believed to be a measure of range ewe productivity. Genetic correlations for Litter Weight weaned at 120 d with prolificacy, growth, and wool traits for Columbia, Polypay, Ram- bouillet, and Targhee sheep were estimated using REML with animal models. Observations per breed ranged from 5,140 to 7,083 for Litter Weight weaned, from 5,140 to 7,095 for prolificacy traits, from 7,750 to 9,530 for growth traits, and from 4,603 to 18,443 for wool traits. Heritability estimates for Litter Weight weaned were low and ranged from 0.02 to 0.11. Fraction of variance due to permanent environmental effects av-
C. Salgado - One of the best experts on this subject based on the ideXlab platform.
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genetic parameters for canalisation analysis of Litter size and Litter Weight traits at birth in mice
Genetics Selection Evolution, 2006Co-Authors: Juan Pablo Gutiérrez, B. Nieto, P. Piqueras, Noelia Ibanez, C. SalgadoAbstract:The aim of this research was to explore the genetic parameters associated with environmental variability for Litter size (LS), Litter Weight (LW) and mean individual birth Weight (IW) in mice before canalisation. The analyses were conducted on an experimental mice population designed to reduce environmental variability for LS. The analysed database included 1976 records for LW and IW and 4129 records for LS. The total number of individuals included in the analysed pedigree was 3997. Heritabilities estimated for the traits under an initial exploratory approach varied from 0.099 to 0.101 for LS, from 0.112 to 0.148 for LW and from 0.028 to 0.033 for IW. The means of the posterior distribution of the heritability under a Bayesian approach were the following: 0.10 (LS), 0.13 (LW) and 0.03 (IW). In general, the heritabilities estimated under the initial exploratory approach for the environmental variability of the analysed traits were low. Genetic correlations estimated between the trait and its variability reached values of -0.929 (LS), -0.815 (LW) and 0.969 (IW). The results presented here for the first time in mice may suggest a genetic basis for variability of the evaluated traits, thus opening the possibility to be implemented in selection schemes.
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Direct and correlated selection response for Litter size and Litter Weight at birth in the first parity in mice
Livestock Production Science, 1998Co-Authors: J. Fernández, A. Moreno, Juan Pablo Gutiérrez, B. Nieto, P. Piqueras, C. SalgadoAbstract:Two lines of mice derived from the same base population were selected for seven generations. Line S was selected to increase Litter size at birth and line W was selected to increase Litter Weight at birth. Two replicates were made in each line. Both traits were measured at first parity and Litters were not standardized. Direct and correlated response were evaluated for both traits. Expected selection response and genetic gain were evaluated at the first and seventh generation of selection. No significant differences were found between expected selection responses and estimated genetic gain. The genetic gain estimated was significantly higher (p
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direct and correlated selection response for Litter size and Litter Weight at birth in the first parity in mice
Livestock Production Science, 1998Co-Authors: J. Fernández, A. Moreno, Juan Pablo Gutiérrez, B. Nieto, P. Piqueras, C. SalgadoAbstract:Two lines of mice derived from the same base population were selected for seven generations. Line S was selected to increase Litter size at birth and line W was selected to increase Litter Weight at birth. Two replicates were made in each line. Both traits were measured at first parity and Litters were not standardized. Direct and correlated response were evaluated for both traits. Expected selection response and genetic gain were evaluated at the first and seventh generation of selection. No significant differences were found between expected selection responses and estimated genetic gain. The genetic gain estimated was significantly higher (p<0.01) for line W than line S for both traits.
H. Rahman - One of the best experts on this subject based on the ideXlab platform.
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Studies on production and reproduction traits of Soviet Chinchilla rabbits in Sikkim.
Indian Journal of Small Ruminants, 2020Co-Authors: R. Chandra, H.d. Karmakar, L. R. Chatlod, H. RahmanAbstract:The aim of this study was to evaluate the production and reproduction traits of Soviet Chinchilla rabbits in 93 Litters at Sikkim. The mean Litter size at birth, Litter Weight at birth, Litter size at weaning, Litter Weight at weaning, at 90 and 120 days of age, gestation period, inter-kindling period were 5.15±0.11, 284.72±19.33 g, 4.39±0.21, 2202.57±190.55 g, 540.50±17.12 g, 1540.50±134.22 g, 2080.00±186.52 g, 31.00±0.07 d and 121.50±0.50 d, respectively. Analysis of variance revealed that year of kindling had significant effect on Litter size at birth, Litter Weight at birth and Litter Weight at weaning. Parity also had influence on Litter Weight at weaning and season significantly influenced the Litter size at birth and Litter Weight at weaning.
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Performance of New Zealand white rabbits in subtropical climate of Sikkim
Indian Journal of Small Ruminants, 2017Co-Authors: R. Chandra, H.d. Karmakar, L. R. Chatlod, H. RahmanAbstract:The performance of New Zealand White rabbits was studied in the subtropical climatic conditions of Sikkim, India. Data from 96 Litters collected over 5 years (1999–2003) were analyzed to find out the effect of non-genetic factors on growth and reproductive performance. Effects of year, parity, season on Litter size at birth, Litter Weight at birth, Litter size at weaning and Litter Weight at weaning, individual Weight at 42, 90 and 120 days were studied. Year, season and parity had no significant effect on Litter size at birth, Litter Weight at birth, Litter size at weaning and Litter Weight at weaning. Sex also did not show any significant effect on body Weight of male and female rabbits at 42, 90 and 120 days of age. However, the season had significant (P
Younes Miar - One of the best experts on this subject based on the ideXlab platform.
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genetic and phenotypic parameters for Litter size survival rate gestation length and Litter Weight traits in american mink
Journal of Animal Science, 2018Co-Authors: Karim Karimi, M Sargolzaei, Graham Plastow, Zhiquan Wang, Younes MiarAbstract:The economic efficiency of mink production is greatly influenced by reproductive performance. Therefore, the objective of this study was to estimate phenotypic and genetic parameters for reproduction traits including total number of kits born (TB), number of live kits at birth (LB), number of live kits at weaning (LW), survival rate at birth (SB), survival rate at weaning (SW), gestation length (GL), average kit Weight per Litter at birth (AWB), average kit Weight per Litter at week 3 (AW3), and average kit Weight per Litter at weaning (AWW) in American mink. Data included records of 3,046 Litters collected by the Canadian Centre for Fur Animal Research at Dalhousie Faculty of Agriculture between 2002 and 2016. Significance (P < 0.05) of fixed effects (year, number of matings, color type, age of dam, origin of dam, sex ratio, and number of live kits) and random effects of permanent environment were determined using univariate repeatability models. A significant effect of permanent environment was only found for survival rate traits (P < 0.05). Subsequently, genetic and phenotypic parameters for all traits were estimated by fitting a set of bivariate models using ASREML 4.0. Heritabilities (± SE) were estimated to be 0.07 ± 0.03 for TB, 0.07 ± 0.02 for LB, 0.09 ± 0.04 for LW, 0.13 ± 0.03 for SB, 0.10 ± 0.02 for SW, 0.29 ± 0.03 for GL, 0.28 ± 0.05 for AWB, 0.19 ± 0.04 for AW3, and 0.10 ± 0.04 for AWW. Moderate positive genetic correlation was observed between AWB with SB (0.66 ± 0.10) and SW (0.61 ± 0.13). Furthermore, genetic correlations of LB with SW and AWB were 0.55 ± 0.16 and 0.53 ± 0.18, respectively. On the other hand, negative and moderate genetic correlations were observed between GL and survival rates at birth (-0.43 ± 0.14) and at weaning (-0.37 ± 0.15). These results indicated that selection for higher Litter Weights at birth can effectively improve survival rate and number of live kits in mink farms. It was suggested to incorporate Litter Weight traits as a selection criterion to increase maternal ability in mink breeding programs. Unfavorable genetic trends were observed for the studied traits indicating that phenotypic selection with low selection intensity had not been an efficient method to improve them over the last 10 yr. It was recommended to use genetic or genomic evaluation methods for mink selection.