Nutritional Interaction of Methionine Sources and Sodium and Potassium Levels on Broiler Performance Under Brazilian Summer Conditions

SUMMARY Two experiments were conducted to study the performance of heat-stressed chickens fed different levels of Na or K with 2 Met sources. In experiment 1, chickens from 7 to 21 d were fed Na at 3 levels (0.15, 0.20, or 0.25%) and from 21 to 48 d at 0.12, 0.17, or 0.22% Na. In experiment 2, chickens from 8 to 21 d were fed K at 3 levels (0.9, 1.0, or 1.1%) and 22 to 48 d at 0.8, 0.9, or 1.0% K. In both experiments, chickens were fed 2 Met sources, DLMet(DLM),and2-hydroxy-4methylthiobutanoicacid(HMB),addedequimolar.Inexperiment 1, all-vegetable diets (corn-soy) were used, and in experiment 2, meat and bone meal was included. Both experiments were performed under Brazilian summer conditions. In experiment 1, no significant interactions between Met and Na levels were found. A positive response for HMB, compared with DLM, was found across Na levels for weight gain (P < 0.05) and feed conversion ratio (FCR P < 0.02) at 48 d. There was no response to Na for weight gain and feed intake (FI), but birds fed the higher level had the best FCR (P < 0.03). In experiment 2, K levels showed a consistent interaction with Met for FI: the highest level of K showed greater FI in HMB birds, but this was not seen when DLM was used. Low and intermediate K levels resulted in better FCR (P < 0.03) compared with higher K levels. No differences in litter moisture were observed between different levels of K. Feathering problems were not evidenced in either experiment. The HMB used in an equimolar amount to DLM resulted in equal bird performance.