- Lifetime relationships among body weight and fleece traits in Angora ewes
Lifetime relationships among body weight and fleece traits in Angora ewes
M.A. Snyman# and W.J. Olivier
Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg EC, 5900, South Africa
#Corresponding author: Gretha Snyman
It is accepted that the ewe flock is mainly responsible for current flock income in any small stock enterprise. This is even more important in mohair producing Angora goats than in sheep breeds where income from mutton production contributes directly to income generated per ewe. As with all biological traits, there are differences among animals in their ability to maintain higher levels of production throughout their flock life than other animals. 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. Data collected since 2005 during the winter shearing on the adult ewe flocks of the participants of the Grootfontein Angora Biobank were analysed to obtain lifetime relationships among body weight, fleece weight, fibre diameter and staple length. Fleece records of the ewes recorded at 12 and 18 months of age were obtained from the GADI-Biobank databank and included in the analyses. The relationships between age of ewe and body weight and fibre diameter followed similar trends, both increased up to four to five years of age, after which it tended to stabilise. Fleece weight, however, increased until two years of age, after which it decreased with age. Staple length tended to follow the same trend as body weight and fibre diameter; i.e. increasing up to four years of age, after which it tended to stabilise. Some of these trends are in contrast with the genetic correlations estimated among these traits at second and third shearing (12 to 18 months of age), where a positive genetic correlation was estimated between body weight and fleece weight, as well as between fibre diameter and fleece weight. From these trends, where fleece weight decreased with age, while body weight and fibre diameter tended to remain constant after four to five years of age, it seems as if these correlations do not apply later in life. Components of fleece weight include fibre diameter, staple length, number of fibres per area of skin (follicle density) and skin area (body size). As body weight (size), fibre diameter and staple length all remained constant later in life, it seems as if the decrease in fleece weight should be due to a decrease in follicle density or the number of fibres produced. These results warrant a more in-depth investigation into follicle characteristics and its possible changes with age of the animal.
Proceedings 48th SASAS congress, Empangeni