- Effect of weaning on the growth of Angora goats
|Last update: August 17, 2011 02:24:49 PM|
The effect of weaning on the growth of Angora goats
P R King, J J Olivier and D Wentzel
Grootfontein Agricultural College,
IT is a well-known fact that a large percentage of Angora goat kids have a poor growth rate after weaning. After kids have been weaned under normal Karoo conditions, it can take up to five months before they regain their weaning mass.
Poor growth after weaning gives rise to various problems in the Angora goat industry. The low kidding percentage of two-toothed ewes obtained by farmers can largely be ascribed to the fact that the ewes, because of poor growth after weaning, do not weigh at least 27 kg at time of mating. It is generally accepted that Angora goat ewes must have a minimum mass of 27 kg for successful mating. Another problem, which can probably be attributed to this poor growth after weaning, is the high mortality that occurs from weaning until two-tooth age. In a survey by Terblanche (1988) among Angora goat farmers, it was found that the mortality rate during this period was 12,5 per cent. This is an appreciably higher percentage than is found in other types of small stock. Weaning shock as the possible reason for poor growth after weaning was researched respectively by Grootfontein and the Jansenville experimental farm. In an experiment carried out in pens, two groups of 25 Angora goat ewes with single kids (groups A and B) were used. The kids of group A were not weaned, while the kids of group B were weaned at four months of age. The ewes received a ration consisting of 80 per cent milled lucerne and 20 per cent mealie meal. Because it is known that nutrition plays an important role in post-weaning growth, the experiment was repeated the following year, when the ewes received a relatively poorer ration of only lucerne hay. Average daily gains in mass of the kids of the different treatment groups were calculated from weaning (four months old) to seven months of age.
The average daily increase (ADI) of the unweaned group on the better ration was 33,8 g compared with the 21,9 g of the weaned group. During the repeat on the lucerne hay ration, the unweaned kids increased by 17,7 g per day compared with the 9,6 g per day of the weaned kids (Table 1). Although various statistics were not significant, the daily gain of the unweaned group on the lucerne/mealie meal ration was 54 per cent more than the weaned group. On the poorer ration, however, the growth of the unweaned group was 85 per cent better than the weaned group.
The statistically significant difference in the growth rate between the two feeding programmes (year one and year two) confirms the big effect nutrition has on post-weaning growth.
Because of the nutritional results obtained (under penned conditions), the experiment was expanded and repeated in 1988 under veld conditions on the Jansenville experimental farm. Three groups of 93 ewes with single kids (born
in the 1987 season) were used in this experiment. As a result of good rains in January 1988, before the commencement of the experiment, the veld was in above-average condition during the period of the experiment. The kids of Group 1 were not weaned. The kids of Group 2 were weaned and placed alone in a camp. The ewes of Group 3 were exchanged with the ewes of Group 2. The kids of Group 3 were thus weaned, but were placed in a camp with ewes. (The swopping of ewes when weaning, is done as a general practice in the Angora goat industry).
The ADI of the kids was calculated for the period from weaning (four months of age) until the age of seven months. The ADI of Group 2 (weaned kids) was 10,2 g and that of Group 3 (ewes exchanged) was 12,4 g. On the other hand, the ADI of the control group (not weaned) of 34 g was approximately three times better than that of the weaned and exchanged groups (Fig 1). This dramatic difference was statistically highly significant.
From this it is clear that weaning does have an inhibiting effect on post-weaning growth. Further, the practice of swopping ewes in order to decrease stress during weaning, holds practically no benefits and is of only limited value.
A further important, but until now unexplained, finding with regard to post-weaning growth, was the difference in the growth rate between ram and ewe kids. In (Fig 2) the average growth rate of the ram and ewe kids of each group is given separately. The ADI of the ram and ewe kids is almost the same when they are not weaned. However, when they are weaned or exchanged, the daily increase of the rams is significantly higher than that of the ewe kids.
If the growth results of the ram and ewe kids of the weaned groups are compared, it is obvious that ram kids achieved significantly better growth under both penned and veld conditions than the ewe kids (Fig 3). Under penned conditions, however, the differences between the sexes were smaller, probably because of better nutritional status under penned conditions. The ADI of the ram kids was 28 g, compared with the 9,4 g of the ewe kids. In practice it would thus be best not to wean the ewe kids together with the ram kids, but to delay weaning them until they are seven months old, just before the next mating season. During the first year under penned conditions, it was established that the ewes whose kids were not weaned, weaned their kids naturally at about five-and-a-half months. During the two years during which the ewes received a relatively lower grade ration, the ewes had already weaned their kids at five months. Due to the relatively poorer nutritional conditions on the veld, it can be expected that the ewes will wean their kids naturally at an even earlier stage. The fact that the ewes naturally wean their kids relatively quickly, has the result that they apparently then have ample time to recover from the negative effects of lactation before the following mating season. If, however, weaning has to take place for any other considerations, it is advisable to give the weaned ewe kids supplementary feed to ensure an acceptable growth rate after weaning.
Further research is being planned at present to determine the effect of late weaning on the reproduction performance of ewes during the following season. The reproduction rate and body mass of the two-toothed ewes which were exposed to the various programmes will also be compared. In addition, the practice of later weaning will be examined to determine if it can significantly decrease mortality from weaning to two-toothed age. Growth before weaning age was relatively good (142 g/day), and the average mass of the veld groups at weaning was an acceptable 18,7 kg. In comparison with the growth rate before weaning age, the growth rate of even the unweaned group after four months of age was still unacceptably low (33,9 g/day). At present research is being done to explain this poor growth after weaning.
Angora goat and mohair journal 33 (2)