The effect of age on the enzyme potentialities of abomasum (chymosin and pepsin) and pancreas (chymotrypsin, trypsin, lipase, colipase and amylase) was studied in the preruminant calf. Three foetuses were collected after slaughter of their dams (260 d of gestation) and 32 calves were maintained as preruminant and slaughtered between birth and 147 d of age. The abomasal mucosas and pancreata were collected and analysed. The abomasal and pancreatic glands of the foetus contained large amounts of

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... nzymes, except pepsin and amylase. On a liveweight basis, the amount of chymosin was maximal at 1.5 d post partum and decreased thereafter ; the amount of pepsin increased until 21 d and then did not change. The development of pancreatic enzyme activities was usually the reverse of that of chymosin ; amylase activity was particularly low at birth. After birth, the development of secretory potentialities could be divided into three phases : during the colostral period, the trend of pancreatic activities was the reverse of that observed for abomasal activities ; from 1.5 to 21 d, most of the enzyme potentialities (except those of chymosin and amylase) appeared to be stimulated by intake level ; after 21 d (1.5 d for chymosin and amylase), the development of secretory potentialities appeared to depend more on age than on intake. Introduction.