Influence of dietary proteins on rennin and pepsin content of preruminant calf vell

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.

A procedure for the isolation of gastric enzymes

“…Assuming that 50 % of the total MCA of the tissue was extracted in each case, the enzymic activities of the crude extracts showed that total units/g tissue were considerably higher for the lamb and kid than for the cow, sheep and goat, which were fairly similar ( Table 1). The levels of enzymic activity/g tissue for all sources in this study were considerably lower than that reported for calf chymosin by Garnot et al (1974). The enzymic activity in piglet stomach was very much lower (4 RU/g) than that in the other sources and this together with the small size of piglet stomachs resulted in greater difficulty in isolating piglet chymosin.…”

Effects of age and suckling on chymosin and pepsin activities in abomasums of goat kids

“…In fact, casein in the milk is the main factor causing the secretion of prochymosin. It has been shown (Garnot 1974) that the abomasums of calves fed a casein diet contained more chymosin and stable levels of pepsin, and the higher the content of casein in the diet, the longer the retaining time of chymosin and pepsin in the abomasums. This could stimulate the secretion amount and speed of prochymosin by cells of the fundus gland of abomasums.…”

Étude des caillettes des bovins à l'état ruminant pour l'obtention d'extraits coagulants à base de pepsine bovine. I. Méthodes d'extraction

“…Ce sont des procédés basés sur une macération des caillettes, séchées ou fraîches, en milieu acide, généralement dans des solutions d'acide chlorhydrique [3][4][5][6][7]. Dans ces procédés l'extraction et l'activation des pro-enzymes se font simultanément, de sorte que l'obtention des enzymes actives est plus rapide en général que dans le procédé traditionnel.…”