- Growth rate of Angora goat kids from birth to 16 months of age
|Last update: November 22, 2010 02:09:49 PM|
GROWTH RATE OF ANGORA GOAT KIDS FROM BIRTH TO 16 MONTHS OF AGE
M. A. Snyman
Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg (EC), 5900, South Africa
email: Gretha Snyman
The importance of pre- and post-weaning growth rate in Angora goats lies more in young goats reaching an acceptable weight at mating age, than in marketing of meat. The relatively poor growth rate of Angora kids, compared to other small stock breeds, is well known. During a study done to investigate the factors contributing to reproduction and kid mortality rate in 12 Angora goat studs, various body weights of kids were also recorded. In this paper, growth rate of kids from birth to 16 months of age, under varying management systems, will be discussed.
Birth weight, weaning weight, 8-, 12- and 16-month body weight of kids born during the 2000 to 2002 kidding seasons in 12 Angora studs (± 3900 kids per year) were analysed. Fixed effects for year of birth, stud, management group within stud, rearing environment, sex, birth/rearing status, age of dam in years and age of kid in days were included in the linear model fitted for each weight. For birth weight, weaning weight and 8-month body weight, data on male and female kids were available, while for 12- and 16-month body weights only data of female kids were available. The reason for this is that culling of a large proportion of male kids took place after 8 months of age, and the remaining male kids are divided into various rearing groups in preparation for the buck sales at 18 months of age.
The average birth weight was 3.2 kg and ranged from 2.4 kg to 3.4 kg between studs. The relationship between birth weight and mortality rate from birth to weaning age is more curvi-linear than U-shaped. Kids with a birth weight below 2.0 kg, only had a survival rate of 50%, while more than 90% of kids with birth weights above 3.5 kg survived till weaning age.
The average weaning weight of kids was 18.1 kg, and varied from 14.2 kg to 21.9 kg for the various studs. Average 8-month body weight of kids was 22.8 kg and ranged from 17.8 kg to 27.9 kg for the different studs, while the respective weights at 12 months of age of female kids were 20.7 kg average, with a range between 15.4 kg and 25.9 kg. Average daily gain was 110 g/day from birth to weaning, 47 g/day from weaning till 8 months of age and 28 g/day from 8 to 12 months of age. Body weight of female kids at 16-months of age varied from 18.9 kg to 31.7 kg among studs (average = 25.3 kg).
When comparing growth curves of male kids from different breeders from birth to 8-months of age, it is evident that in those studs where the male kids did not receive any supplementary feeding after weaning, body weight of the kids remained virtually constant from weaning till 8 months of age. In the studs where the male kids received supplementary feeding after weaning, the kids showed an increase in body weight after weaning. Female kids usually receive no supplementary feeding after weaning, and kids from all breeders showed no increase in body weight from weaning to 8 months of age.
Variable growth rates of female kids from 8- to 12- and 16-months of age were observed among the different studs. In some studs, the kids showed an increase in body weight, while other remained constant or some even lost weight after 8 months of age.
The phenomenon where kids did not grow after weaning, referred to as “weaning shock”, has farther-reaching complications than it seems at first glance. Due to the fact that young does do not grow much after weaning, a large proportion of them do not reach the generally accepted minimum weight of 27 kg before their first mating at 18 months of age. For example 30%, of young does in this study had mating body weights of less than 25 kg. The lower reproductive efficiency of young does could largely be ascribed to their lower body weight, and this impacts negatively on the overall reproductive efficiency of the herd. The underlying reasons for the poor growth performance after weaning in Angora kids needs to be investigated further.