Threonine needs of finishing broilers: Growth, carcass, and economic responses

Marginal dietary deficiencies of threonine, the third limiting amino acid i n broilers, may result in economic losses from increases feed conversion an d reduced breast meat accretion. It is important, therefore, to meet the mi nimum dietary threonine level needed in a broiler diet. Few studies, howeve r, have addresses the threonine level needed in a broiler diet. Few studies , however, have addressed the threonine needs of finishing broilers. Those which have do not agree with current NRC standards. This study was conducte d to determine the level of threonine needed for performance, the carcass t raits of finishing broilers, and the economic importance of threonine in te rms of profitability. A total of 4096 male commercial broilers received threonine-deficient diets containing corn, peanut meal, wheat middlings, poultry oil, and supplement al amino acids from 42 to 56 days of age. The experimental diets ranged fro m 0.45% to 0.81% total dietary threonine in 0.06% increments. This study in cluded a corn-soybean- poultry meal control diet. Growth, feed conversion, and carcass responses of broilers fed the experimental diets supplemented w ith surfeit threonine were equal to or better than responses obtained from broilers fed the control diet. A total dietary threonine level of 0.66% to 0.67% appears to be adequate to support good growth and carcass response in broilers from 42 to 56 days of age. Economic analysis indicated that the l evel of dietary threonine resulting in optimum profitability was near the l evel that resulted in optimum feed conversion and carcass composition.