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Title: Dietary threonine needs for growth and immunity of broilers raised in different litter conditions

item CORZO, A
item KIDD, M
item Dozier Iii, William
item PHARR, T

Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2007
Publication Date: 10/25/2007
Citation: Corzo, A., Kidd, M., Dozier III, W.A., Pharr, T., Koutsos, E. 2007. Dietary threonine needs for growth and immunity of broilers raised in different litter conditions. Journal of Applied Poultry Research. 16:574-582.

Interpretive Summary: Feed cost represents 65% of the total live production cost for broiler chickens that supports an industry that produces 8 billion birds annually. Feed cost approximates 65% of the total cost for producing broilers. Large percentage of the cost of the diet is protein/amino acid contributing ingredients. Threonine is the third limiting amino acid for broiler chickens. The threonine requirement was evaluated with Ross × Ross 708 broilers from 21 to 42 days of age. Broilers in two studies were reared under two different litter conditions: new vs. built-up soft wood shavings. Results from this research indicate that broilers raised the new litter litter had lower digestible threonine requirements. Feed conversion was optimized with a digestible threonine requirement of 0.64 and 0.65%, respectively, for broilers reared on new and used litter. Digestible threonine requirements for breast yield were 0.65 and 0.67%, respectively, for broilers reared on new and used litter. It appears that broilers have a higher threonine need when reared with used litter, which may relate to a higher maintenance need for threonine.

Technical Abstract: Two studies were conducted simultaneously, and evaluated digestible Thr (d-Thr) needs of Ross × Ross 708 male broilers. Broilers in the two studies were reared under two litter conditions: new (NL) vs. used built-up soft wood shavings (BL). Separated by a center aisle, all floor pens from one side of the close-sided house contained NL while the opposite side contained BL. Broilers received common diets up to 21 d, and then fed one of six dietary d-Thr levels that ranged from 0.43 to 0.78% (0.51-0.86% total Thr) up to d 42. At 42 d, birds were processed. Sub-sample of birds from each experimental unit corresponding to either the 0.43% or 0.64% d-Thr treatments were taken, immune function quantified and lymphoid organs 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, carcass and breast meat absolute and relative weights. Depending on the variable, these responses were maximized between 0.63 and 0.66, and 0.65 and 0.70% d-Thr when broilers were raised in new and used litter, respectively. Low d-Thr (0.43%) was without effect on most immune parameters. However, low d-Thr decreased relative thymus weight and increased monocyte nitric oxide production in dirty and new litter environments, respectively.