Determining the Digestible Lysine and Lysine: Threonine Ratios for Growing Turkeys

There have been relatively few lysine requirement studies that have covered the full productive life of commercial toms (0 to 20 wk). Lysine is the reference amino acid for Ideal Protein ratios and accurately defining the requirement reduces fractional errors in the corresponding ideal protein ratios. A series of studies were conduct to determine the lysine concentrations (total and digestible) in g per Megacalorie (Mcal) of ME needed to support optimum performance of turkeys during five age periods that cover the full production cycle of commercial turkeys. The lysine concentration is reported as gram per mcal ME in order to adjust for the effect of metabolizable energy on nutrient intake for comparison with previous reports in the literature. Four dietary lysine levels were used in each of five studies conducted between 2 and 20 wk of age: The NRC (1994) recommended total lysine concentration, two levels below and one level above. Performance parameters included BW gain, feed efficiency and carcass weight. The maximal lysine response in the 2to 4-wk poults was at 5.86 g per Mcal ME (1.70% total lysine). Poults fed 4.99 g per Mcal ME (1.54% total lysine) had the best performance from 4 to 8 wk. There were no dietary lysine effects in the 8to 12-wk and 12to 16-wk turkey toms except for carcass protein efficiency in 12to 16-wk. Turkeys fed diets containing 3.29 g (1.05% total lysine) or above, performed maximally during the 16to 20-wk period.