- Supplementary feeding of sheep on winterveld in the Karoo
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Supplementary feeding of sheep on winterveld in the Karoo
Van der Vyver PHB, Van Niekerk BDH
THE response of animals to supplementary feeding depends mainly and in most cases - even in the grassveld regions - on the energy value of the ration. This observation is based on experiments conducted with the supplementary feeding of sheep on winter veld in the Karoo.
Sheep graze selectively and in addition their protein requirements are low under these feeding conditions. A chemical analysis of the protein content of veld samples consequently gives a misleading impression of the actual quality of food eaten by the sheep.
It would be a great help to the farmer if the value of feeds for drought and winter-feeding purposes are indicated in terms of their energy value. He would then be able to determine with ease which feeds he can buy and feed to best advantage.
On a farm in the Philipstown district we carried out an experiment to determine the influence of maize, lucerne and a mixture of lucerne and maize (fed on an equal nett energy basis) on the body weight and wool production of Merino ewes and their lambs. The results of this experiment also gave an indication of what may be expected in this respect from sheep receiving supplementary feed on the veld during the winter months, and of what such supplementary feeding would cost.
RATIONS AND EXPERIMENTAL ANIMALS
The experiment was conducted from 4 June to 14 October 1964 on the farm Kareefontein of Mr. C. J. Marais. Altogether 694 Merino ewes and 692 lambs, divided into four more or less equal groups, were used. For practical reasons the body weights and wool data of only 30 representative ewes and their lambs were recorded during the experiment.
The four groups of ewes with lambs, the lambs being two to four weeks old, were fed four rations during the experimental period of 19 weeks.
The lucerne hay was moistened with molasses to ensure that the sheep would consume all of it. Crushed yellow maize was used in this experiment.
The sheep were fed only twice a week, but the quantity of feed consumed by them was expressed in terms of the average daily intake.
For the rest all animals received precisely the same treatment. Phosphate-salt licks were available to all sheep and the sheep were treated against internal parasites and enterotoxaemia
The ewes with their lambs were kept on Karoo veld consisting predominantly of dry Lehmann lovegrass; Eragrostis lehmannians, and divided into four separate camps. To minimise the effect of differences in veld quality that may have existed between the camps, the groups changed camps at intervals of two weeks. The sheep were fed twice weekly, Mondays and Thursdays, and the ewes and their lambs were weighed every two weeks when they changed camps.
At the end of the experiment all ewes and lambs were shorn to determine the influence of supplementary feeding on raw-wool production At this stage the lambs carried 5½ to 6 months and the ewes 7 months wool of which the last 4¾ months wool was produced during the experiment;
The weight gains of the 4 groups of ewes are reflected in Figure 1 and in Table 1. The figure shows, that the group of ewes that received no supplementary feed only just maintained their weight during the first four months. Only during the last three weeks of the experimental period did their weights show a rising trend. This is probably attributable to the effect of reduced milk production as well as an improvement in the quality of the veld as a result of the 1.50 inches of rain recorded on 13 June and 0.40 inches on 1 August.
Of the groups that received supplementary feed the group that was fed only maize (4 ounces, per ewe/lamb per day) during all stages or the five-months experimental period, maintained the highest bodyweights The lucerne group (8 ounces per ewe/lamb per day) did second best, while the group that was fed a mixture of maize (2 ounces per ewe/lamb per day) and lucerne hay (4 ounces per ewe/lamb per day) performed the poorest.
It is also interesting that the weight losses as a result of the exceptionally cold weather experienced during the experiment were considerably more marked in the control group than in the three groups of sheep that received maize or lucerne supplementation.
According to a, statistical analysis of the weight gains of the ewes all three groups that received supplementary feeding differed highly significantly from the control group. The differences between maize and lucerne groups were also significant; while both these groups in turn performed highly significantly better than the groups fed the maize/lucerne mixture.
The weight gains of the lambs (Figure 2) showed exactly the same trend as those of the ewes. However, the benefit obtained from maize supplementation was relatively greater, while the difference between lucerne hay and the mixture of lucerne and maize, on the other hand, was relatively small.
A statistical comparison of the body-weight gains of the lambs showed that all four groups differed significantly from one another.
The raw-wool production of the four groups of ewes and the four groups of lambs is reflected in Table 1. In the case of the ewes all three groups that had received supplementary feed produced approximately ½ pound of wool more than the control group. These differences were statistically significant, but the wool production of the three groups receiving supplementary feed did not differ significantly from one another or although slightly more wool was produced with the lucerne - containing rations than with the maize alone.
In the case of the lambs the differences in wool production of the four groups were small and one of the three groups that had received supplementary feed produced significantly more wool than the control group. Those that received maize did, however, produce significantly more wool than the group fed the lucerne/maize mixture.
Does supplementary feeding pay?
The supplementary feeding of animals on veld grazing may have various advantages. It is, for instance, known that ewes with lambs receiving supplementary feeding usually produce more wool; produce healthier wool (fewer tender fleeces); in the case of lambs, maintain the higher wool production, although to a lesser degree, for the rest of their productive life; have higher body weights - which is of economic value if the sheep are intended to be slaughtered, and in the case of ewes and ewe lambs, may produce better and healthier lamb crops in the ensuing breeding season.
With the exception of the direct increase in wool production obtained from the ewes and lambs, it is difficult to express these benefits in economic terms.
In most cases (depending on the price of wool and feed but particularly on the quality of the veld grazing) the income from the additional wool production is not sufficient to cover the feed and additional transport and labour costs. To be able to determine therefore whether it would be economically justified to give sheep supplementary feed on veld, one will have to consider also under the specific farming conditions the other four factors mentioned above.
If the weight gains of the ewes and lambs as well as the combined wool production of ewes and lambs are taken into account (see Table 1) it is clear that the supplementary feeding of a quarter pound of maize per ewe/lamb per day produced much better results than the supplementary feeding of a comparable quantity of productive feed energy in the form of lucerne hay or of a mixture of lucerne hay and maize. At current feed prices maize was by far the most economic ration to feed.
Since the various feeds (or combinations of them) were fed at approximately the same level of productive energy, it is difficult to explain the differences that occurred between the three rations, unless it is assumed that the supplementary feeding of these feeds influenced the eating habits of the three groups of sheep in different ways.
If the lucerne group and the maize group are compared, it is clear that the sheep fed maize used the veld better; that is to say, these sheep ingested more feed off the veld than those fed lucerne. This inference is borne out by incidental observations made during the experiment, for instance, that the sheep, which were fed only maize grazed further afield after having eaten the maize and having drunk water. The two groups that received lucerne or lucerne and maize were, however, not inclined to graze after they had been fed and remained lying at the watering places practically throughout the day.
A possible explanation for this finding is that maize is less filling than lucerne, particularly in respect of crude fibre, which possibly resulted in the sheep fed maize having had a keener appetite for veld roughage.
Another possible explanation is that maize is much richer in phosphate than lucerne hay and consequently maize will also supplement this mineral. Since the veld in this area is already deficient in phosphate, it may be expected that the provision of phosphate by means of maize will result in an increased feed intake. However, as all experimental sheep received a phosphate lick, it is doubtful whether the mineral content of the feed could have played an important part in the results obtained in this experiment.
A third possible explanation is that maize fed in supplementation, as against lucerne supplementation, has a higher digestibility, thereby causing a higher voluntary intake of the ration as a whole.
Not one of these explanations can, however, solve the problem of the poorer response to the lucerne/maize mixture. Only further research into the role of these factors will give a complete explanation of these findings.
From the results of this experiment it would appear that various feeds may affect the grazing habits of sheep in different ways; also that this effect, at any rate in the case of this experiment, is apparently not influenced by the protein content of the feed but possibly by its crude-fibre content or body and by its digestibility.
Farming in South Africa 41 (4)