PHYSIOLOGICAL CHANGES IN INTERMEDIARY METABOLISM OF VARIOUS SPECIES OF RUMINANTS INCIDENT TO FUNCTIONAL DEVELOPMENT OF RUMEN

Abstract

Blood glucose was detd. in young and/or adult ruminants of the following spp.: cattle, sheep, goat, addax antelope (Addax nasomaculata). aoudad (Ammotragus lervia); Asiatic sika deer (Cervus sika). Dybowski''s deer (C. dybowskii). eland (Taurotragus oryx), European red deer (Cervus elaphus), Indian blackbuck (Antilope cervicapra), mouflon (Ovis musimon), and white-tailed deer (Dama virginiana.). In contrast to the typical adult levels of 40-65 mg./100 ml., young ruminants were found to have blood glucose levels in the "carnivore range" during the first few weeks of life. Young ruminants of 4 spp. exhibited much higher intraven. glucose toleran ces than adults of the same spp. The differences between young and adult ruminants are believed to result from metabolic changes incident to bacterial fermentation of carbohydrates in the rumen, as they appear when the young animals undergo a shift in diet from milk to hay. The glycemic level in these spp. bears an inverse relationship to the size and functional development of the rumen. Because both young and adult ruminants are unable to maintain their characteristic levels of blood glucose while fasting, it is postulated that ruminant spp. exhibit a relative deficiency in the pituitary-adrenal mechanism for mobilization of endogenous metabolities for gluconeogenesis under these conditions. The low intraven. glucose tolerance characteristic of adult ruminants is believed to be due to a high rate of exogenous gluconeogenesis. The necessity for this is obviated in the milk-fed young animal by absorption of carbohydrate per se from the gut. Adult llamas, Arabian camels and one Arabian-Bactrian camel hybrid (pseudoruminants) were found to have blood glucose levels similar to those of the young ruminants, i.e., significantly higher than adult ruminants. The physiological basis of this is unknown.