[Physiological model of water and chlorine shifts in the lamb stomach following intake of sheep milk or milk substitutes].

It has been found that the average concentration of hydrogen ions in the milk chyme formed in the abomasum of suckling lambs within a period of 1-3 hours after feeding is above a pH of 3.0, similar to that of calves (JANCARIK, 1961). Hence, the digestion of milk proteins in lambs must be expected to proceed mostly at a pH higher than that of pepsin digestion, that is to say, in most cases it will range between 3.0 and 5.0. pH titration curves were made of fresh untreated ewe's milk obtained from ewes of different breeds (Merino, Finnsheep, Romanowsheep) to calculate the amounts of water and chlorine which have to be secreted with the gastric acid to attain the pH level that is required for the digestion of proteins contained in 100 ml of ewe's milk. Similarly, calculations were made with regression equations (table 2) showing that the gastric secretion of water and chlorine as expressed by the percentage proportion of H2O and Cl in the blood was considerably higher in the young and especially the very young animals (figure 1). The susceptibility of young lambs is due to this fact. Moreover, attention is drawn to the interrelationship between the gastric digestion of proteins and general possibility of dehydration and loss of chlorine in cases of disturbed gastric secretion (e.g. gastric achlorhydria, absence of gastric enzymes, gastrogenic dysentery). The buffer capacity of fresh ewe's milk cannot be directly estimated from the concentration of hydrogen ions in it. It has been established that in some sheep the pH of milk may, under physiological conditions, exceed the value of 7.0; a condition that has an adverse effect on the nutrition of weak lambs. Figure 2 shows the differences between different breeds concerning gastric Cl secretion. The situation is similar with regard to H2O.