Hay was fed to an in vitro continuous culture of the rumen microbial population and to sheep kept in metabolism cages, and the effects of potassium chlorate addition on the rumen fermentation were studied. The compound was given for 8 days in vitro and for either 3 or 8 days in vivo.Potassium chlorate addition in vitro (13-7 mg/g hay D.M.) depressed the production of CH 4 and acetate, had little effect on propionate production and caused a small increase in the production of w-butyrate and w-valerate. The treatment also depressed cellulose digestion and the concentration of DNA in fermentor liquor, but increased the CO a :CH 4 ratio in fermentor gas.When given in vivo for 8 days at 6-7 mg/g hay D.M., potassium chlorate progressively depressed total VFA concentration in rumen fluid, had no effect on VFA molar proportions but caused a small increase in the CO 2 :CH 4 ratio in rumen gas. When administered in vivo for 3 days at 14-4-15-3 mg/g hay D.M. the treatment increased the molar proportions of propionate and depressed those of acetate in rumen fluid without affecting total VFA concentration. There were considerable differences between animals in propionate response, and the maximum responses were generally obtained 2-5 days after dosing had ceased. Potassium chlorate addition also caused a temporary reduction in appetite with some sheep.It was concluded that potassium chlorate was toxic to the rumen microbial population when given for 8 days, but that large doses given over 3 days could be used to increase the ratio of propionic acid relative to acetic and butyric acids produced from • the rumen fermentation.
The growth pattern of full fed Friesian steers was one of initial increasing rate of gain followed by a declining rate of gain with increasing bodyweight. Differences in ration energy level which had a significant effect on performance had little influence on efficiency or carcase composition of large breed type steers. In a serial slaughter experiment with Friesian steers, the carcases of animals grown on a grass silage/barley diet had more fat and less meat than those grown on a concentrates/chopped straw diet even though both diets were similar in energy content and supported similar levels of performance. There was an interaction between the effects of diet and slaughter weight. At low carcase weights there was no effect of diet on composition but with increasing carcase weight, the diet effect emerged. A restriction of 20 per cent in feed intake reduced performance, efficiency and carcase fat content.
A survey was conducted on 5100 purchased male Friesian calves in the period of 1976 to 1985 to determine the effect of serum immunoglobulin (Ig) level (low 15 ZST units or high 15 ZST units), purchase weight (light 40 kg or heavy 40 kg) and feeding system (bucket or ad libitum) on the occurrence of diarrhea, respiratory disease and mortality in the period 1 to 49 days following purchase. In the low and high Ig categories the respective proportions were 0.21 and 0.14, 0.6 and 0.28, 0.11 and 0.03 for diarrhea, respiratory disease and mortality. The corresponding values for light and heavy calves were 0.26 and 0.14, 0.30 and 0.32, 0.09 and 0.04. Similarly for bucket and ad libitum calves the respective values were 0.15 and 0.17, 0.28 and 0.34, 0.05 and 0.06.
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