- Growth and mohair production of Angora and Angora x Boer goat genotype kids
|Last update: November 22, 2010 02:06:10 PM|
GROWTH AND MOHAIR PRODUCTION OF ANGORA AND
ANGORA X BOER GOAT GENOTYPE KIDS
Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg (EC), 5900, South Africa
Email: Gretha Snyman
A project aimed at developing an easy care, hardy goat, with a relatively high reproductive ability and good carcass characteristics, and which will also produce good quality mohair, free from kemp and medullated fibres, was initiated at the Jansenville Experimental Station in South Africa in 1988. Two genotypes, viz. a 75 % Angora goat : 25 % Boer goat (G1) and a 87.5 % Angora goat : 12.5 % Boer goat genotype (G2) were subsequently established. The objective of this paper is to evaluate growth and mohair production from birth to 18 months of age of the kids of these two established genotypes against that of pure bred Angora goat kids.
Data from G1- (n=921), G2- (n=827) and Angora (n=361) kids born from 1992 to 2000 were available. Kids were shorn at five months of age for the first time, and subsequently at 10, 14 and 18 months of age. At each shearing, body weight, fleece weight, clean yield percentage, clean fleece weight, fibre diameter and staple length were recorded. Before the second, third and fourth shearings, fleece and conformation traits of all kids were subjectively assessed on a linear scale based on the standards of excellence set for South African Angora goats.
General linear model procedures of SAS were used to analyse data on body weights and mohair traits. There were significant differences in body weight at all ages, where G1-kids were the heaviest, followed by the G2-kids and then the Angora kids. Angora kids produced the heaviest fleeces (P<0.05) at 10 months of age, followed by the G2-kids and then the G1-kids, while G2-kids produced the heaviest fleeces at 18 months of age. Fleeces produced by G1-kids had the highest clean yield at 10 and 18 months of age, as well as the longest staples at 10 months of age. At 18 months of age, there was no significant difference in staple length among the genotypes. Angora kids produced fleeces with lower fibre diameter than those produced by G1- or G2-kids (P<0.05).
Generation of the kid had no effect on birth weight of G1-kids, while 3rd generation G2-kids had the highest birth weight (P<0.05). Weaning weight and body weight at 10 months of age of 1st generation G1-kids were the highest, followed by 2nd and then 3rd generation kids. The opposite trend was observed among the G2-kids, where 3rd generation kids had the highest body weights. At 18 months of age, there was no difference (P>0.05) in body weight between generations within G1, while 3rd generation kids in G2 remained heavier than 2nd generation kids. Fleece weight at 10 and 18 months of age were higher in 3rd than in 1st or 2nd generation G1-kids, while the same applied only for fleece weight at 18 months of age in the G2-kids. The only significant effect of generation on fibre diameter was observed at 18 months of age in G1, where 3rd generation kids produced fleeces with the highest fibre diameter.
Significant differences among genotypes occurred for all subjectively assessed traits. Face, neck and bellies and points covering of Angora kids were fuller (P<0.05) than those of G2- and G1-kids respectively, while they also had a softer face covering. Fleeces produced by Angora kids also had better style and more ideal character than those produced by G1- and G2-kids. Evenness of fleece was best in the G1-kids, followed by G2-kids and Angora kids respectively. Density of the fleece followed the opposite trend than evenness of fleece. Amount of yolk was also more ideal in the Angora kids. General conformation and hocks were best in G1-kids (P<0.05).
The effect of Boer goat genetics on body weight of G1- and G2-kids found in this study, is in accordance with results reported by various authors. Apart from increased direct genetic effects on pre-weaning growth rate, the higher milk production potential of the Boer goat most probably also contributed to higher weaning weights recorded in G1- and G2-kids. The higher body weight and better conformation of G1- and G2-kids also implies a heavier carcass at slaughter age.
For the growth traits and most of the fleece traits analysed, G1-animals performed better than G2-animals. It is therefore suggested, that further selection for improved mohair quality be done in the G1-herd.