Genetic analysis of body weight in South African Angora kids and young goats

Abstract

The data used for this study consisted of 27 485 kid records, the progeny of 599 sires and 10 077 dams, and were collected on the 2000-to 2009-born kids of 11 Angora goat studs. Variance and covariance components and ratios pertaining to direct additive genetic variation, maternal additive genetic variation, maternal permanent environmental variation, and the relationship between direct and maternal effects for birth weight (BW; kg), weaning weight (WW; kg) and body weight at 8, 12 and 16 months (W8, W12 and W16; kg) were estimated with the ASReml program. Direct additive heritability estimates of 0.22, 0.20, 0.12, 0.34 and 0.58 were obtained for BW, WW, W8, W12 and W16, respectively. Maternal heritabilities were 0.10, 0.09, 0.03 and 0.06 for BW, WW, W8 and W12, respectively, while maternal environmental effects of 0.13, 0.11, 0.06 and 0.04 were estimated for the latter traits, respectively. An unfavourable correlation of -0.38 was obtained between direct and maternal genetic effects for BW. Low to medium positive direct genetic correlations were estimated between birth weight and body weights recorded at a later stage in life. High positive direct genetic correlations were estimated among WW, W8, W12 and W16. The maternal genetic correlations obtained between birth weight and the other body weights were medium to high. Phenotypic correlations among the traits ranged from low to high. Genetic trends of body weight at different ages indicate that although not many breeders use objective measurement as a selection tool, body weight increased slightly in the 11 studs over the 10-year study period. Since reproduction and body weight should be included in a selection programme for Angora goats, the relationship between the direct and maternal additive effects should be clarified. The importance of a sufficiently structured and related pedigree, especially on the part of the dams and maternal grand dams, has been highlighted in this study. As this is one of the constraints of this data set, data collection in the Angora goat industry should continue until a suitably structured data set has been built up that could be used to estimate multi-trait breeding values for the industry.___________________________________________________________________________________

Prediction of body weight from linear body measurements in sheep

“…The heritability for ABW was estimated as 0.42±0.17 which was higher than 0.38 as estimated by Borg et al (2009) in Western sheep but lower than 0.58±0.03 as reported by Snyman (2012) in Angora goats.…”

A Study on Phenotypic and Genetic Correlations between Birth Weight and other Growth Traits in Teddy Goat

“…Low to moderate estimates of genetic correlation between the birth and weaning weight were documented by some researchers [12][13][14][15][16][17][18][19][20][21][22][23]. Low phenotypic correlation as found in present study between the two traits were also reported by different researchers [12,17,20,24].…”

Quantitative trait loci associated with pre-weaning growth in South African Angora goats

“…These fitness traits show a slow selection response to conventional selection and incorporation of marker assisted selection (MAS) could result in faster genetic gains. After validation, the putative QTL identified in this study could be used to manipulate early growth and due to a strong positive genetic correlation, also yearling weight in Angora goats (Snyman, 2012). Additional research would however first be required to decrease the confidence interval ranges significantly in order to determine the precise locations of the QTL.…”

“…Although inter-age genetic correlations for body weight are strongly positive, this correlation decreases as time between measurements increases, indicating separate QTL that govern different growth stages (Hadjipavlou & Bishop, 2008). Snyman (2012) reported that no increase in direct or maternal birth weight was found over the past ten years in South African Angora goat stud herds making use of the current SI. This emphasises the need to identify chromosomal segments of interest for birth and weaning weight in order to improve survivability and reproduction efficiency.…”

“…This results in many young does not reaching the target weight of 25kg at 18 months and a low conception rate when they are mated for the first time. Snyman (2012) reported genetic correlation between weights at different ages for Angora goats, ranging from 0.36 between birth and weaning weight to 0.57 between birth and 16-month weight. These estimates were somewhat lower than what has previously been found in wool sheep, but increased for weaning weight with later age stages (0.73 to 0.93).…”