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Unformatted text preview: Performance of Different Broiler Genotypes Fed Diets with Varying Levels of Dietary Crude Protein and Lysine K. G. Sterling, G. M. Pesti, 1 and R. I. Bakalli Department of Poultry Science, University of Georgia, Athens 30602-2772 ABSTRACT Two experiments were conducted to deter- mine if a 3-way interaction among genotype, dietary ly- sine, and CP is an important influence on dietary re- sponses. The genotypes were Ross 308 and Cobb in exper- iment 1 and Ross 508 and Arbor Acres Classic in experiment 2. The experimental designs were completely randomized with an incomplete 2 × 2 × 3 factorial arrange- ment of treatments. On d 7 of experiment 1, 4 replicate pens of 6 chicks each were fed 1 combination of dietary lysine and CP (17% CP with 0.6, 0.7, and 0.8% lysine and 23% CP with 0.7, 0.8, and 0.9% lysine) until d 21. On d 17 of experiment 2, 4 replicate pens of 35 chicks each were fed 1 combination of dietary lysine and CP (17% CP with 0.7, 0.8, and 0.9% lysine and 23% CP with 0.8, 0.9, and 1.0% lysine) until d 42. On d 43 of experiment 2, 3 birds per pen were processed. Regression analysis showed differences ( P < 0.05) due to genotype for body Key words : crude protein, lysine, broiler, genotype 2006 Poultry Science 85:1045–1054 INTRODUCTION Researchers have realized the diverse production po- tentials offered by gender, genotype, and genotype crosses and how nutrition, particularly nutrient levels, can influence those potentials. Genetic differences in growth rate, feed intake, and feed efficiency have been reported between genotypes (Washburn et al., 1975; Ma- lone et al., 1979; Holsheimer and Veerkamp, 1992; Mac- Leod et al., 1998; Smith and Pesti, 1998; Smith et al., 1998). In addition, genetic differences have been ob- served for breast meat yield, abdominal fat pad percent- age, and other parts yields (Acar et al., 1991; Holsheimer and Veerkamp, 1992; Smith and Pesti, 1998; Smith et al., 1998). Genetic differences influence the response of chicks to varying dietary levels of CP (Smith et al., 1998) and subsequently the requirements of amino acids (Han and Baker, 1991, 1993; Pesti et al., 1994). 2006 Poultry Science Association Inc. Received for publication March 4, 2005. Accepted for publication July 8, 2005. 1 Corresponding author: [email protected] 1045 weight gain (BWG), feed intake, and feed conversion ratio (FCR) in experiment 1, and BWG, carcass yield, breast fillet and tender yields, and abdominal fat pad percentage in experiment 2. Increasing dietary CP decreased abdomi- nal fat pad percentage in both experiments; however, increasing dietary lysine only decreased this parameter in the starter-phase chicks. In both experiments, Ross broilers had a greater response to supplemental lysine when 17% CP was fed, but less response to supplemental lysine when 23% CP was fed for both BWG and FCR (3- way interaction). Three-way interactions between dietary CP and lysine levels and genotype were observed for BWG ( P < 0.01), feed intake (0....
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- Spring '11
- Lysine, Broiler, Ross × Ross