Comparative studies on the digestive physiology of sheep fed on semi-purified or roughage-concentrate diets

Abstract

1. The food and water intake and diurnal variations in the rumen contents were measured in sheep with rumen fistulas receiving semi-purified or pelleted roughage-concentrate diets. The rates of secretion and composition of parotid saliva of the sheep on both diets and of sheep fed on hay were determined. The sheep had continuous access to the diet. 2. The mean daily intakes of the semi-purified and roughage-concentrate diets were 920 and 2234 g respectively. The corresponding water intakes were 2.50 and 6.05 1.3. Noneof the sheep ruminated on either diet. The weight of total contents and of dry matter in the rumen was highest in animals on the roughage-concentrate diet, and marked diurnal fluctuations, which reflect the eating habits of these animals, were observed. The semi-purified diet appeared to have a very marked water-retaining capacity in the rumen. 4. The estimated daily total secretion of both parotid glands was 2.7, 5.4 and 11.5 1. in sheep fed on the semi-purified diet, roughage-concentrate and hay respectively. No appreciable differences were observed in the composition of parotid saliva between the three groups of sheep. In sheep receiving hay, saliva secretion was lower during eating than between periods of eating, during part of which time the sheep presumably ruminated. 5. It is concluded that the observed differences in parotid secretion reflected differences in the physical form of the diet.