Submitted to: Poultry Science
Publication Type: Abstract Only
Publication Acceptance Date: 1/26/2004
Publication Date: 1/26/2004
Citation: Kidd, M.T., Corzo, A., Barber, S.J., Branton, S.L., Kerr, B.J., Hoehler, D., Locatelli, M.L. 2004. Dietary threonine responses in three commercial broiler strains. Poultry Science. p.1770. Interpretive Summary:
Technical Abstract: roilers consuming diets marginal in Thr may result in Lys inefficiency in turn reducing breast meat because Thr is third limiting. There are no published reports evaluating Thr responses across broiler strains. Because the growth and tissue accretion rates of commercial broilers differ, a study evaluated Thr needs in three commercial broiler strains (A, multipurpose; B, high-yield; C, high-yield) known to differ in terms of feed intake, growth rate, and breast meat yield. Birds were randomized across 96 floor pens (12 birds/pen), received a common diet from d 1 to 20, and fed graduations of Thr (0.52 to 0.87% total Thr in 0.07% increments) from d 21 to 42. Treatments (3 x 6 factorial) were replicated between 5 or 6 times. The corn, soybean meal, and peanut meal test diet contained 0.43% and 0.96 digestible Thr and Lys, respectively. A feed conversion interaction (P < 0.05) occurred indicating that strain C was more sensitive to Thr deficiency than strains A and B. The abdominal fat interaction (P < 0.05) indicated that strain A had more relative fat than strains B and C. All strains differed (P < 0.05) in terms of BW gain (A, 78.2; B, 75.1; C, 72.9 g/d). Strain C had the lowest (P < 0.05) feed intake resulting in the lowest (P < 0.05) Thr intake, but it had the highest (P < 0.05) breast meat yield. Most parameters tested yielded quadratic (P < 0.05) models whereby Thr estimates could be predicted. Namely, BW gain and breast meat yield resulted in total Thr estimates (95% of the upper asymptote) of 0.74 and 0.71%, respectively, which are in good agreement with the 1994 NRC (0.74%). The plasma Thr sigmoid response verified the former estimates. Analysis of strain intercepts and slopes as affected by Thr differed (P < 0.05) in terms of feed intake, but not BW gain or breast meat yield. The 21 to 42 d Thr need across strains is about 0.74% total or 0.65% digestible (Thr/Lys of 0.68).