Analysis of records of a Perendale flock V. Repeatabilities and genetic correlations between ages

Lewer, RP; Rae, A. L.; Wickham, G. A.

doi:10.1080/00288233.1983.10427036

Cited by 5 publications

(1 citation statement)

References 15 publications

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“…On the other hand several authors have investigated the effect of ewe age on wool production, various wool characteristics, and litter size (e.g. E ikje 1975; L ewer et al 1983; A tkins 1986; A tkins 1990; G ates and U rioste 1995). The studies indicated that genetic correlations between fleece weights recorded at early ages (1 or 2 years old) and fleece weights recorded at higher ages are different from one.…”

Section: Introductionmentioning

confidence: 99%

Population parameters for birth and ewe fleece weight at different parities in Baluchi sheep

Yazdi

Näsholm

Johansson

et al. 1997

J Animal Breeding Genetics

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Direct and maternal performance of ewes at different parities were examined in Baluchi sheep. The data set was collected during the period 1966-1989 from two flocks at a sheep breeding station in the north-east of Iran. The animals included in the data set were unselected and randomly mated. The traits analysed were birth weight of lamb and fleece weight at different parities of the ewe. Variance components were estimated using Restricted Maximum Likelihood with a bivariate animal model including fixed effects of year, sex, type of birth and parity, and random effects of additive genotype of lamb (direct genetic effect), additive genotype of ewe (maternal genetic effect) and common environment (excluded for ewe fleece weight), and random residual effect. Direct and maternal genetic correlations between different parities were estimated. There was evidence of increasing phenotypic and genetic variances and heritabilities from parity 5 for birth weight of lamb in flock 1, but only evidence of a slightly increasing age trend for the environmental and phenotypic variance in flock 2. The average heritabilities over flocks and parities were 0.12, 0.11 and 0.26 for the direct, maternal and total heritability, respectively, while the average genetic correlation between direct and maternal effects for this trait was 0.42. There were no indications of any age changes in variances or heritabilities for ewe fleece weight in flock 1, but indications of slightly increasing age trends for the environmental and phenotypic variance. The average heritabilities over flocks and parities were 0.19, 0.04 and 0.22 for the direct, maternal and total heritability, respectively, while the average genetic correlation between direct and maternal effects was slightly positive in flock 1 but increasingly negative with age of the ewe in flock 2. Direct genetic correlations between parities 1-5 were very high for birth weight of lambs (on average 0.96) in contrast to the markedly lower correlations of parities 1-5 with parity 6 (on average 0.67) in flock 1 with a similar pattern for the maternal genetic correlations. In flock 2, these correlations were also high but without the marked decrease between parities 1-5 with parity 6 that was found in flock 1. Direct genetic correlations between the various parities for ewe fleece weight were similar for the two flocks, ranging from 0.73 to 0.92 and without any obvious differences between the various combinations of parities. However, the maternal were markedly lower than the direct genetic correlations, especially for the combinations of parity 5 and 6 with the earlier parities, and most pronounced in flock 2 fluctuating from -0.54 to 0.79. To obtain reliable estimates of breeding values for birth weight of lamb, it is recommended that the prediction should include not only earlier but also later parities (ages) of the ewe.

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Section: Introductionmentioning

confidence: 99%