Estimates of environmental effects and genetic parameters for live weights and fleece traits of Angora goats

G.B. Nicoll, M.L. Bigham and M.J. Alderton

Land Corporation Limited, P.O. Box 1235, Hamilton and Whatawhata Hill Country Research Station, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1989, 49: 183-190

Three data sets comprising 2329, 2102, and 720 Angora goats sired by 30, 29 and 17 bucks used in the Land Corporation's Waitangi Angora flock, were used to obtain estimates of the effects of age, of dam, sex, rearing rank and birth day (age). Characters studied (and years of birth) in the three data sets were: Set 1: weaning weight and 12-month fleece weight (1978-1986); Set 2: 6-month fleece weight and yearling fleece weight (the sum of both 6- and 12-month fleece weights; 1978-1985); Set 3: 12-month live weight and 12-month fibre measurements of fibre diameter, standard deviation of fibre diameter, percent medullation and percent kemp (1984-1986).

The weaning weights of kids out of dams aged 3, 4, 5 and 6 + years were heavier than those out of 2-year old dams by 0.7, 1.0, 1.5 and 1.8 kg respectively (P<0.001). Corresponding differences in 6-month fleece weight were 0.01, 0.02, 0.03 and 0.03 kg (P<0.05). Age-of-dam effects were variable for 12-month live weight and arcsine-transformed percent kemp, and nonsignificant for the remaining traits studied. Males had heavier live weights and fleece weights than females (P<0.001), but differences between the sexes were generally small for the fibre measurement traits. Multiple-reared kids (and later-born kids) had significantly lighter live weights and fleece weights than single-reared kids (and earlier-born kids). Both rearing rank and birth day effects were generally small and not significant for the fibre measurement traits.

Heritability estimates for weaning weight, 6-, 12-month and yearling fleece weights, 12-month live weight, fibre diameter and standard deviation of fibre diameter were respectively 0.10, 0.24, 0.25, 0.36, 0.24, 0.51 and 0.21. Arcsine transformation of percent medullation and percent kemp data yielded heritabilities of 0.16 and 0.02 respectively. Subject to the limited number of sires represented in the data sets studied, genetic correlations between 12-month fleece weight and the two live weight traits were negative and of medium magnitude. There were also strong positive genetic correlations between 12-month fleece weight and both fibre diameter and arcsine- transformed percent kemp. Phenotypic correlations among live weight, fleece weight, and fibre diameter traits were all positive and of medium to high magnitude. Corresponding correlations with arcsine-transformed percents medullation and kemp were generally small and positive.

It was concluded that direct incorporation of the genetic and phenotypic parameter estimates obtained in this study into selection index calculations, could not be advocated without due attention to the limited sample sizes and associated errors of estimation.

Keywords: NZSAPAB; Angora goats; environmental effects; heritabilities; genetic correlations; phenotypic correlations; live weights; fibre traits

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