- Relationship among body weight and hair production traits of Angora goat ewes over their lifetime in the flock
Relationship among body weight and hair production traits of Angora goat ewes over their lifetime in the flock
M.J. Herselman1 & M.A. Snyman1
1Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg EC, 5900, South Africa.
Background: In Angora goats, income from the current flock is generated through hair production and reproduction. Angora goat ewes are mostly kept in the flock until the age of six to seven years. However, in some flocks nearly 10% of the ewes are older than seven years of age. It is therefore imperative that the ewes are able to maintain quantity and quality hair production until the end of their productive flock life.
Aim: The aim of this study was to determine the relationship among body weight and hair production traits of Angora goat ewes over their lifetime in the flock and assess the variation in hair production among ewes.
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 used for this study. Body weight, fleece weight, fibre diameter and staple length data recorded from 12 months until 11 years of age on the ewes were analysed. The number of fibres produced for each animal was calculated from the fleece weight, fibre diameter, staple length and specific gravity of mohair. For each animal, various ratios between the traits were also calculated. The GLM procedure of SAS was used to estimate the effect of age of the ewe on the various individual traits, as well as the trait ratios. The variation among all ewes, as well as 7-year old ewes, in terms of fleece weight produced per unit of body weight was also determined.
Results and Discussion: The relationships of age of ewe with body weight and fibre diameter followed similar trends; both increased up to five years of age, after which it tended to level off. Fleece weight, however, increased until three years of age, after which it decreased with age. No specific trend was discernable for staple length. The ratio of fleece weight produced per unit of body weight was the highest for kids and young ewes up until two years of age. Thereafter it declined with an increase in age. Fibre diameter and staple length followed the same trends as fleece weight relative to body weight. Expressing fibre diameter and staple length relative to unit of fleece weight produced, indicated that older ewes produce lighter fleeces with longer staples and higher fibre diameter than kids and young ewes (two years of age and younger). The number of fibres produced per animal declined from 2.194 x 106 per unit of body weight 0.67 in 12 month old kids, to 0.400 x 106 in 11-year old ewes. The number of fibres produced per unit of body weight 0.67 ranged from 0.178 x 106 to 7.878 x 106 for the 12-month old kids (average = 2.194 x 106) and from 0.142 x 106 to 2.287 x 106 for the 7-year old ewes (average = 0.807 x 106).
Conclusion/recommendations: Components of fleece weight include fibre diameter, staple length, number of fibres per area of skin (follicle density) and skin area (body size or body weight). From the trends of these traits with age, it is apparent that the decrease in fleece weight with age is due to a decrease in the number of follicles producing fibres. As ewes are not able to maintain high levels of hair production until older ages, it would thus not be advisable to select for increased fleece weight in young ewes.
Proc. 51st Congr. S. Afr. Soc. Anim. Sci. Bloemfontein. 10-12 June.