- Prediction of lifetime productive and reproductive performance of Angora ewes from early production
Prediction of lifetime productive and reproductive performance of Angora ewes from early production traits
1Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg EC, 5900, South Africa.
Background: The ewe flock plays an important role in the generation of income from any small stock enterprise. In the case of Angora goats it generates income from the current flock through hair production and reproduction. The ideal is to have a high producing ewe flock in terms of reproduction as well as mohair production. It is therefore important to identify ewes at an early age that will maintain a high level of mohair production and reproduction throughout their flock life.
Aim: The aim of this study was to predict from the information available at an early age which ewes will be the highest producers and reproducers over their lifetime in the flock.
Methodology: The project protocol was approved by the Ethical Committee of the Grootfontein Agricultural Development Institute (GVE/AP2/18). Data collected on the flocks of three South African Angora goat producers from 2000 until 2015 were included in this study. During kidding, full pedigrees, birth date, sex and birth status of each kid were recorded. The following production data were recorded on the kids: Body weight at birth, weaning, 8-, 12- and 16 months of age, as well as fleece weight, fibre diameter profile, style and character at the second and third shearings. Full reproduction data, body weight before mating, as well as fleece weight, fibre diameter profile, style and character at the winter shearing were recorded on the ewe flocks. Estimation of genetic parameters was done with the ASReml program, while prediction of lifetime performance was done by various logistic regression analyses (PROC REG procedure of SAS with the LOGISTIC option).
Results and Discussion: Early fleece weights were genetically favourably correlated with all the adult traits, except with adult fibre diameter. The opposite was true for early fibre diameter, which was genetically unfavourably correlated with all the adult traits, except with adult fibre diameter. Early body weights were also genetically favourably correlated with all the adult traits, except with adult fibre diameter. Maiden ewe reproductive performance at the first parity was favourable genetically correlated with lifetime reproductive performance. Although maiden ewe reproductive performance was favourably correlated with adult fleece weight and fibre diameter, the standard errors of these correlations were very high. Ewes that had higher 12- and 16-month body weights were more likely to kid, less likely to abort, more likely to have multiple kids and more likely to wean multiple kids. Ewes with higher total weight of kids weaned and number of kids born at their first parity were more likely to kid, less likely to abort, more likely to have multiple kids and more likely to wean multiple kids than ewes with corresponding lower early values.
Conclusion/recommendations: The negative relationship between reproduction and fleece production in the adult ewes emphasises the fact that positive selection pressure on early fleece weight should not be done at the cost of reproduction. Only young ewes with unacceptably low fleece weights should be culled, while too much selection pressure on early fibre diameter in the ewes should also be avoided. Positive selection pressure can be put on early body weights. As far as the early reproductive traits are concerned, emphasis should be placed on total weight of kids weaned and number of kids born at first parity.
Proc. 51st Congr. S. Afr. Soc. Anim. Sci. Bloemfontein. 10-12 June.