Infusion of various short chain fatty acids causes different changes in the blood glucose and insulin concentrations in growing lambs deprived of food overnight.

Glucose and insulin concentrations of jugular blood plasma were monitored in growing lambs over 8 h, following a 2 h infusion of acetate, propionate, n-butyrate, n-valerate and physiological saline into the ruminal vein. Propionate and especially n-valerate infusion significantly increased blood glucose concentration. n-Butyrate induced only a small increase of shorter duration, while acetate failed to exert a pronounced effect on the blood glucose level. SCFA infusion, except for acetate, raised the insulin level in the blood. Relative rise was closely correlated with the length of carbon chain of the SCFA, that is, n-valerate caused the largest elevation of the insulin level, followed by n-butyrate and propionate. At the same time, acetate failed to cause a marked influence on the insulin level. These results of insulin showed agreement with glucose concentration changes, with the exception of n-butyrate treatment, where the increase of plasma insulin concentrations after the infusion proved to be much larger than that of glucose, relative to the preinfusion value.

Feeding animal fats to sheep.

In an experiment lasting 7 weeks, 18% of the calculated energy requirement of 5 nonpregnant ewes was met by giving natural fats of animal origin mixed in the ration (at a level of 6.6%). Changes in certain blood and blood plasma parameters of lipid and energy metabolism were monitored at 5 time-points during the experiment. Samples of rumen fluid were taken three times for determining the concentrations of volatile fatty acids (VFA). Rumen fermentation was studied by in sacco method. Total lipid (TL) content of the liver and fatty acid composition of the liver tissue and subcutaneous adipose tissue (from the tailhead) were analyzed at the beginning and at the end of the experiment. At the concentration used in this experiment, fat supplementation caused neither digestive disturbances nor any other adverse changes in the animals' health status. It did, however, exert a significant influence on blood plasma lipid composition. TL and total cholesterol (TCh) concentration increased and blood glucose level decreased. A rise in triglyceride (TG) content was accompanied by a drop in free fatty acid (FFA) concentration. The in sacco experiments and volatile fatty acid (VFA) levels in the rumen fluid suggested an impaired crude fibre digestion in the rumen. At the same time, fat supplementation enhanced rumen proteolysis. The TL content of liver samples did not exceed the physiological limit. The liver biopsy samples had decreased myristic acid and increased stearic and oleic acid concentrations. No change occurred in the fatty acid composition of the fat depots.