Threonine requirement of the grower turkey tom

Two experiments were conducted to determine threonine requirement for maximum performance and breast and drumstick major muscle relative weights of turkey toms raised from 8-10 wk and 11-13 wk of age. Also plasma free amino acid concentration in response to feeding a diet with graded levels of threonine was measured. A corn-peanut meal diet was formulated to contain 0.59, 0.72, 0.85, 0.98 and 1.11% threonine and fed to Large White turkey males (British United Turkeys, BUT) in both trials. Each treatment was replicated among 5 and 8 individual cages in experiments 1 and 2, respectively. Two days prior to the end of each trial, blood was removed from the brachial vein of five toms per treatment and analyzed for plasma amino acid concentration. At the end of each experiment, final body weight and feed consumption were recorded and feed efficiency was computed. Birds were then sacrificed and pectoralis major and gastrocnemius muscles were weighed. The 0.85% dietary threonine resulted in the highest weight gain and feed efficiency ratio in the first trial. In the second experiment an increase (P0.05) in weight gain was also obtained by the 0.85% dietary threonine with no further significant improvement beyond that level. Therefore the current results indicate that the threonine requirement for maximum weight gain of turkey toms raised from 8 to 10 and 11 to 13 wk of age is 0.85%. The changes in blood threonine concentration further supported the estimated requirement of threonine obtained from the performance data. Increasing dietary threonine from 0.59 to 1.11% during both growing periods, however, had no effect on pectoralis major or gastrocnemius muscles yield. In conclusion threonine requirement for maximum performance of the grower turkey tom raised from 8 to 13 wk of age was 0.85% diet, a value slightly higher than that reported in the literature.