Studies in mineral metabolism. XXXIV. The effect of sulphur upon the weight and wool production of sheep when food intake is not limited

Abstract

On comparing the weight increases of the two groups of sheep it will be noticed that the mean increases are reasonably equal there being only a difference of 0.11 kg. in favour of the sulphur fed group which is altogether insignificant. When allowance is made for the difference in food intake it is found that this adjustment does not make an appreciable reduction in the variance and that the adjusted difference of 2.2 kg. in favour of the control group remains quite insignificant. In short, it may be said that the conclusion is justified that a daily dose of 5 grms. of flowers of sulphur is without effect on the bodyweight, food consumption and wool production of sheep. It seems necessary, however, to review briefly the work on sulphur feeding to sheep that has been published from this Institute in order to state the final conclusions clearly. Steyn's investigations (1931, 1932, 1934 and 1935) were undertaken, as stated by him, to determine the quantity of sulphur that could be administered to young and full-grown sheep with safety over prolonged periods. Obviously, the body weights of the sheep could be registered with advantage and this was done accordingly. Furthermore, the sheep had to be shorn in the course of the experiment, and hence, the weights of the wool produced were recorded. It is abundantly clear from Steyn's publication (1934) that he fully realizes the unsuitability of his material to determine the nutritional value of sulphur when, naturally, increase in body weight, food consumption, effect on production, etc., are important considerations and if this information had been required his experiments would have been planned differently so as to ensure the registration of these observations for the collection of suitable data for justifiable and definite conclusions. At best, therefore, it can be said that the results of Steyn's original experiment (1931, 1932) seemed to suggest that sulphur when administered to mature sheep at. the rate of 5 grms. once, twice or three times weekly, over prolonged periods stimulates increase in body weight and wool yield. In a subsequent experiment (Steyn 1935) 5 grms. of sulphur were administered daily to immature sheep without detrimental effect on body weight and on the wool production of the animals. As a matter of fact the differences in body weight and in the weights of the wool produced are significantly in favour of the sulphur fed animals. All the sheep were fed ad lib. as one group, which excludes a consideration of more efficient food utilization or increased food consumption of the sulphur fed when compared with the controls. Again, therefore, it can be said that this investigation suggested that sulphur feeding to sheep affects their body weights and wool production beneficially. What is, however, quite definite about this work is that sulphur administered in the doses stated did not affect the animals detrimentally. Working upon the indications of Steyn's original experiments (1931, 1932) du Toit et al (1935) carried out an investigation with sheep to determine the nutritional value of sulphur. Five grms. of sulphur were dosed to each animal in a group of sheep daily while another group was kept as controls. The experiment was planned to satisfy the requirements of a feeding trial. The body weights of the sheep were registered periodically, a productive ration was fed to the individual sheep in separate feeding boxes and the food consumption of the individual animals was recorded. The animals were kept on the basal ration for twelve months pre-experimental period after which the sulphur was administered to the one group for a further twelve months. Both groups were of course still kept on the basal ration for the second period of twelve months. Wool was collected from all the animals in both groups, analysed and reported on by van Wyk, Botha and Bekker (1935). In view of the entire absence of any significant difference in body weight, food consumption and wool production of the sulphur fed group when compared with the control group the conclusion appears to be justified that a daily dose of 5 grms. sulphur did not affect the sheep significantly, when they were given a production ration. The above experiment with sheep on a limited food intake obviously excludes a consideration of increased food consumption which might be an effect of sulphur feeding and hence the investigation reported on in the present paper under conditions of ad libitum feeding was undertaken. Again the experiment was planned, primarily with the object of determining the nutritional value of sulphur and fulfils the demands of a feeding trial. As in the previous work no beneficial effect of sulphur feeding could be determined, nor was the food intake of the sulphur fed group significantly affected. The main result of the Onderstepoort experiments on the effect of administering sulphur to sheep, could therefore be summarized as follows: Five grms. of sulphur will be given per os to sheep over prolonged periods without detrimental effects. The body weight, food consumption and wool production are apparently not significantly affected by the sulphur administered to the sheep.