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.Keywords: Birth weight, genetic parameters, maternal effects, weaning weight
Highlights
Body weight is one of the most important selection criteria in almost any sheep- and goat-breeding enterprise
The ram kids received supplementary feeding from weaning until 8 months. For most of those studs where the ram kids were run under veld conditions after weaning without supplementation, 12- and 16-month body weights were available, while these weights were not available for those studs in which the ram kids were fed after weaning. That explains why it seems that the ram kids lost body weight from 8 to 12 months
The different feeding strategies caused a large variation in average body weight between the studs at the various ages, which increased the total variation in body weight in the animal population used for this study, the relatively high coefficients of variation obtained
Summary
Body weight is one of the most important selection criteria in almost any sheep- and goat-breeding enterprise. Continuous selection for increased body weight has led to a situation where a further increase in body weight is contra-indicated. This is not the case in Angora goats, where there is still a positive relationship between ewe body weight and reproductive performance (Snyman, 2010a). Body weight should be one of the most important criteria in the selection programme of Angora goats. Angora goat stud breeders use a selection index that emphasizes increasing body weight (Snyman et al, 1996). Much of the selection for body weight that is done in breeding sires is subjective
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
