Effects of diet on responses to exhaustive exercise in Nile tilapia ( Oreochromis nilotica) acclimated to three different temperatures

Abstract

The effects of exhaustive exercise on O 2 consumption (Ṁ O 2 ), waste nitrogen (ammonia and urea) excretion, and on lactate, ammonia and water content of white muscle and liver, were determined in tilapia fed a diet enriched either in long chain polyunsaturated fatty acids of the ω3 series (ω3 LCPUFA) as menhaden oil (menhaden oil diet; MOD) or in saturated fatty acids (SFA) as coconut oil (coconut oil diet; COD), and acclimated to three different temperatures (16°, 23° and 33°C). At all temperatures, exhaustive exercise elicited an increase in postexercise Ṁ O 2 and ammonia excretion rates, and in white muscle lactate and ammonia levels. There were no differences between the two dietary groups in the total amount of O 2 consumed and muscle lactate accumulated, but at 23°C and 33°C exhaustive exercise stimulated a significantly greater increase in ammonia excretion in COD as compared with MOD tilapia. The magnitude of the difference in postexercise ammonia excretion between COD and MOD animals increased with increases in environmental temperature, being greater at 33°C than at 23°C. The increased ammonia excretion observed in the COD group was not a result of differences in white muscle ammonia or water content following exhaustive exercise. The data indicate that diets enriched in ω3 LCPUFA are beneficial in that tilapia fed these diets exhibited reduced ammonia excretion following exhaustive exercise, compared with tilapia fed diets enriched in SFA.