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Dietary Threonine Needs for Growth and Immunity of Broilers Raised Under Different Litter Conditions¹

A. Corzo^*,2, M. T. Kidd^*, W. A. Dozier, III, G. T. Pharr and E. A. Koutsos

^* Department of Poultry Science, Mississippi State University, Mississippi State, MS 39762; USDA, Agricultural Research Service, Mississippi State, MS 39762; Department of Basic Sciences, Mississippi State University, Mississippi State, MS 39762; and Department of Animal Science, California Polytechnic State University, San Luis Obispo, CA 93407

Correspondence: ² Corresponding author: acorzo{at}poultry.msstate.edu

Two studies were conducted simultaneously and evaluated the Thr needs of male Ross x Ross 708 broilers. Broilers in the 2 studies were reared under 2 litter conditions: new (NL) vs. used built-up soft wood shavings (BL). Separated by a center aisle, all floor pens from 1 side of the close-sided house contained NL, whereas the opposite side contained BL. Broilers received common diets up to 21 d and then were fed 1 of 6 total dietary Thr levels that ranged from 0.51 to 0.86% total Thr until d 42. At 42 d, birds were processed. A subsample of birds from each experimental unit corresponding to either the 0.51 or 0.72% Thr treatments was taken, immune function was quantified, and lymphoid organs were weighed. Results for live performance and carcass traits are in close agreement with previously reported values in the literature. Quadratic responses were observed for BW gain, feed conversion, and carcass and breast meat absolute and relative weights. Depending on the variable, these responses were maximized from 0.71 to 0.74% Thr when broilers were raised on NL and from 0.73 to 0.78% Thr when broilers were raised on BL. Low Thr (0.51%) was without effect on most immune parameters. However, low Thr decreased relative thymus weight and increased monocyte NO production in built-up and new litter environments, respectively.

Key Words: breast meat yield • broiler • immunity • litter • threonine

¹ This is journal article number J11074 from the Mississippi Agricultural and Forestry Experiment Station supported by MIS-322220. Use of trade names in this publication does not imply endorsement by the Mississippi Agricultural and Forestry Experiment Station and USDA-ARS of the products nor similar ones not mentioned.