Ionophore effects on animal metabolism

Abstract

Studies were conducted to determine the effects of ionophores, diet, level of intake and dietary restriction on vital organ mass and hepatic fructose 2,6-bisphosphate (F26P2) levels in growing non-ruminants and ionophores on vital organ mass and function in finishing steers. Liver weight and relative liver weight (RLIV; g liver/100 g body weight) of rats were increased (P $<$.05) by 50 but reduced by 150 mg/kg monensin. Total hepatic F26P2 tended (P $<$.16) to be 16% greater for monensin-fed rats. The RLIV of chicks was greater (P $<$.10) for the 100 mg/kg monensin treatment. Monensin-fed chicks had 84% (P $<$.13) total hepatic F26P2. Liver weight was 24% (P $<$.05) and RLIV was 35% (P $<$.05) larger for protein than carbohydrate-fed chicks. Hepatic level of F26P2 was 58% lower (P $<$.10) in 24 h fasted chicks than in fed chicks. Liver weight and RLIV were greater (P $<$.10) for lasalocid-fed chicks than control or monensin-fed chicks, at a restricted intake. Ad libitum fed chicks had twice (P $<$.001) the concentration and total hepatic F26P2 of restricted chicks. Liver weight (P $<$.05) and RLIV (P $<$.10) was larger for control than lasalocid- or monensin-fed rats. Level and total hepatic F26P2 tended (NS) to increase with increasing levels of intake. The liver weight of steers did not differ due to an ionophore. Hepatic glycogen levels tended (NS) to be greater for steers that were fed an ionophore. Fructose 1,6-bisphosphate was 22% lower (P $<$.10) in hepatic tissue of steers fed ionophores, while dihydroxyacetone phosphate was greater (P $<$.10) in steers fed lasalocid and tended to be greater (P $<$.19) for monensin-fed steers. Pyruvate tended (NS) to be greater while lactate and fructose 2,6-bisphosphate tended (NS) to be lower in hepatic tissue of steers fed an ionophore. The results of this research indicates that vital organ mass and hepatic F26P2 of growing non-ruminants are responsive to ionophore addition, diet, nutritional state and level of intake. Also, the addition of an ionophore to the diet of a finishing steer for 45 d had no effect on vital organ mass. However, several metabolites of carbohydrate metabolism were altered, indicating increased hepatic gluconeogenesis in finishing steers fed an ionophore.