No abstract

No abstract

No abstract

Studies were undertaken to determine the influence of dietary proteins on the rennin and pepsin contents of preruminant calf veil. Three groups of 12 Friesian calves were each fed either milk proteins, whey proteins or a 50:50 mixture of these 2 diets. They were slaughtered at a constant weight of 150 kg and their veils collected and dried. Another group of veils was obtained from 8 animals that had been fed milk proteins in a separate experiment. The extraction of the abomasal enzymes was carried out at acid pH, and the extracts were quantitatively analysed for rennin and pepsin by DEAE-cellulose column chromatography. Qualitative analyses were also performed by agarose-acrylamide gel electrophoresis. The only enzymes observed using this last method were rennin and bovine pepsin II. Statistical analysis of the quantitative enzyme determinations indicated a trend for the veils from calves fed diets containing casein to be richer in total activity and in rennin, while the level of pepsin remained approximately constant. It seems that casein may induce the secretion of rennin. However, further experiments will be necessary to confirm this. Important differences were observed between the 2 groups of veils from calves given the same diet, but grown in slightly different conditions.During the first week of the life of the calf, its stomach undergoes pronounced modifications. Indeed, at birth, only the abomasum plays an important role in digestion, due to the closure of the oesophageal groove. Until recently it was thought that the animal abomasum secretes rennin from birth and that this enzyme disappears at weaning, being replaced by pepsin. It is now known that the veil of the unweaned calf always secretes pepsin to some extent (Henschel, Hill & Porter, 1961).Today, milk is being progressively replaced in the preruminant calf diet by feeds containing fats and nitrogenous products of lower price. It was, therefore, interesting to study the effects of such diets on abomasal enzyme secretion. We obtained some 30 dried veils from preruminant calves slaughtered at the same weight. The animals had been divided into 3 groups fed milk proteins, whey proteins or a 50:50 mixture of these 2 diets. Determinations of rennin and pepsin were carried out by DEAEcellulose column chromatography of the solutions obtained after macerating the veils in acid conditions. The results were statistically analysed.

No abstract