Genetic parameters among weight, prolificacy, and wool traits of Columbia, Polypay, Rambouillet, and Targhee sheep.

Bromley, Cassity; Snowder, G. D.; Vleck, L.D. Van

doi:10.2527/2000.784846x

Cited by 79 publications

(108 citation statements)

References 27 publications

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“…This might have contributed to lower estimates. Estimates of c² pe for reproduction traits accord to estimates reported by Bromley et al (2000) (0.01 to 0.07)…”

Section: Resultssupporting

confidence: 76%

“…The estimates obtained for number of lambs born and weaned were generally low. The h² estimate for number of lambs born per ewe lambing (0.06) presented in Table 5 falls within the range of literature estimates (0.03 -0.12) (Brash et al, 1994b;Bromley et al, 2000;Rosati et al, 2002;Cloete et al, 2002a;b;. In the case of number of lambs weaned per ewe lambing, the estimate was 0.03.…”

Section: Resultssupporting

confidence: 72%

“…10 (Brash et al, 1994b, Bromley et al, 2000, Swan et al, 2001Cloete et al, 2002a;b;Rosati et al, 2002;Cloete et al, 2003;Matika et al, 2003). The fraction of variance due to permanent environment was 0.07 for both traits which corresponds well with estimates obtained by Bromley et al (2000); Swan et al (2001) and Rosati et al (2002) Total weaning weight per ewe lambing is a trait often used as an overall measure of lamb production (Bromley et al, 2001) and has had favourable genetic and economic responses (Ercanbrack & Knight, 1998). Total weaning weight, a composite trait, depends on fertility, litter size, weight (growth) of individual lambs, mothering ability and embryonic and lamb survival.…”

Section: Resultsmentioning

confidence: 99%

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Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Wyk¹,

Fair²,

Cloete³

2004

SA J. An. Sci.

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Genetic parameters for production and reproduction traits in the Elsenburg Dormer sheep stud were estimated using records of 11743 lambs born between 1943 and 2002. An animal model with direct and maternal additive, maternal permanent and temporary environmental effects was fitted for traits considered traits of the lamb (birth and weaning weight and survival). Fixed effects were sex, birth status, year and age of dam. Weaning weights were pre-adjusted to a 100-day equivalent. For reproduction traits (considered as traits of the ewe), which included number and weight of lambs born and weaned, repeatability models were fitted. The random part consisted of direct additive and ewe and sire permanent environmental effects. Direct and maternal heritability estimates were 0.13 and 0.23 for birth weight and 0.07 and 0.09 for weaning weight. Corresponding proportions of total phenotypic variance due to maternal permanent and temporary environment were 0.09 and 0.28 and 0.06 and 0.22 respectively. The genetic correlation between animal effects was -0.23 in the case of birth weight. The results showed that temporary environment (full sibs within a year) generally has a major effect on all pre-weaning traits. The direct heritability estimate of survival was 0.02 while the temporary maternal environmental variance as a proportion of phenotypic variance was 0.10. The estimates obtained for number and weight of lambs born and weaned were generally low, ranging from 0.03 for number of lambs born to 0.11 for total weight at birth. The permanent environmental effect of the ewe accounted for 6-7% of the total phenotypic variance. Genetic correlations of total weight of lamb weaned with the other reproduction traits were generally high (0.64 to 0.92) with low standard errors. The corresponding phenotypic, environmental and ewe permanent environmental correlations were all medium to high and estimated with a fair deal of accuracy according to low standard errors. The genetic relationship between weaning weight of the ewe and her lifetime reproduction (accumulated over four lambing chances) ranged between 0.40 and 0.67. Correlations between number of lambs weaned per ewe and weight of lamb weaned per ewe were particularly high (0.8 -0.9). It was concluded that the maternal environmental effect should be partitioned into two components (permanent and temporary) when data sets involving multiple births over many generations are considered.

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“…This might have contributed to lower estimates. Estimates of c² pe for reproduction traits accord to estimates reported by Bromley et al (2000) (0.01 to 0.07)…”

Section: Resultssupporting

confidence: 76%

Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Wyk¹,

Fair²,

Cloete³

2004

SA J. An. Sci.

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show abstract

“…The genetic correlation between prolificacy and birth weight was close to zero. Bromley et al (2000) concluded that birth weight and prolificacy were only slightly genetically correlated, with mostly different genes involved in the expression of these two traits. The genetic correlations between prolificacy and weaning weight, 12 month weight, 18 month weight, ewe mating, post-partum and ewe weight at weaning were 0.…”

Section: Resultsmentioning

confidence: 99%

Phenotypic and genetic relationships between lamb and ewe traits for the Sabi sheep of Zimbabwe

Matika¹,

Wyk²,

Erasmus³

et al. 2001

SA J. An. Sci.

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Genetic and phenotypic correlations were estimated between lamb and ewe traits in a flock of Sabi sheep reared at the Matopos Research Station. Direct additive estimates of heritability were: 0.28 ± 0.04; 0.17 ± 0.00; 0.25 ± 0.01; 0.39 ± 0.01; 0.59 ± 0.01; 0.50 ± 0.01; 0.68 ± 0.03; 0.12 ± 0.003; 0.25 ± 0.01; 0.11 ± 0.00; 0.12 ± 0.00; for birth weight, weaning weight (120 days), 12 month weight, 18 month weight, ewe mating weight, post partum weight, ewe weight at weaning of lamb, total weight of lamb weaned, slaughter weight, hot and cold carcass weights respectively. Genetic correlations between birth weight and other weights to 18 months were high (0.75-0.85), whilst the relationship between weaning, 12 month and 18 month weight was close to unity. The genetic correlation between birth weight and ewe weights (mating, post-partum and dam weight at weaning of lamb) were moderate viz. 0.51 ± 0.08, 0.40 ± 0.09, 0.49 ± 0.07 respectively and were close to unity at 18 months of age viz. 0.96 ± 0.02, 0.92 ± 0.03, and 0.84 ± 0.03 respectively. Total weight of lamb weaned was moderately correlated to birth weight (r g = 0.46 ± 0.15) but tended to be highly correlated with 18 month weight (0.92 ± 0.10) and ewe weights (0.75 ± 0.09-0.91 ± 0.07). The genetic correlation between birth weight and slaughter and carcass weight was moderate and was high at 18 months. The heritability estimates from a univariate logit transformed analysis for fertility, prolificacy and lamb survival were 0.08 ± 0.04, 0.22 ± 0.03, and 0.01 ± 0.02 respectively. The genetic correlation between fertility and lamb weight and ewe weights was low (-0.08 ± 0.004, to 0.06 ± 0.02) and some estimates had large standard errors. The genetic correlation between prolificacy and birth weight was close to zero. The genetic correlations between prolificacy and weaning weight, 12 month weight, 18 month weight, ewe mating, post-partum and ewe weight at weaning were 0.07 ± 0.02; 0.12 ± 0.00; 0.07 ± 0.02; 0.22 ± 0.00; 0.13 ± 0.00; 0.24 ± 0.00 respectively, and that between fertility and prolificacy was negative (-0.17 ± 0.07). Genetic correlations between lamb survival and birth weight, weaning weight, 12 month weight, 18 month weight and total weight of lamb weaned were 0.18 ± 0.00, 0.26 ± 0.00, 0.15 ± 0.00, 0.15 ± 0.00, 0.13 ± 0.00 respectively. Selection for birth weight and total weight of lamb weaned have possible uses in a selection index for the Sabi flock. _______________________________________________________________________________________

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“…Also, seasonal character of the oestrus incidence and lactation has to be eliminated and fertility has to exceed two lambs per sheep and partus. _____________________________________________________________________________________ In order to achieve these high objectives, permanent genetic improvement of traits which are of interest to breeders is necessary (Lewis et al, 1996, Okut et al, 1999, Sakul et al, 1999, Bromley et al, 2000, Petrović et al, 2003, 2004, 2005, 2006.…”

Section: Introductionmentioning

confidence: 99%

Genetic improvement of fertility in sheep by selection according to physiological parameters

et al. 2007

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Abstract:In this paper, fertility parameters of sheep are discussed and principles analyzed in order to obtain the optimal methods for their evaluation. Mathematical procedures for evaluation of genetic and phenotypic parameters and anticipation of genetic values, today, are mainly based on different linear and non-linear concepts, therefore it is necessary to accept the reality that there is no absolute accuracy. Special emphasis is on the possibility of use of physiological quantitative fertility indicators in sheep selection, considering that there is correlation between them and fertility traits. In this regard, the degree of response to direct and indirect selection within population is analyzed in order to established the nature of parameters necessary for evaluation of data and determine the relative degree of such response.

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Genetic parameters among weight, prolificacy, and wool traits of Columbia, Polypay, Rambouillet, and Targhee sheep.

Cited by 79 publications

References 27 publications

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Phenotypic and genetic relationships between lamb and ewe traits for the Sabi sheep of Zimbabwe

Genetic improvement of fertility in sheep by selection according to physiological parameters

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