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Unformatted text preview: Effect of Low-Protein Diets on Growth Performance and Body Composition of Broiler Chicks 1,2 K. Bregendahl, 3,4 J. L. Sell, and D. R. Zimmerman Department of Animal Science, Iowa State University, Ames, Iowa 50011 ABSTRACT Three experiments were conducted to in- vestigate effects of dietary manipulations to improve growth performance and whole-body composition of broiler chicks fed low-protein diets supplemented with crystalline amino acids. In all experiments, male chicks (1 d old) were fed a common corn-soybean meal diet (23% CP) for 7 d and subsequently allotted to treatment diets in a completely randomized design (10 chicks per floor pen, six replications). Chicks had free access to the isoenergetic diets (3,200 kcal ME n /kg) for 2 wk, after which chicks were weighed and then fasted for 24 h, and the whole-body DM, N, and ether extract contents of two chicks per pen (and six baseline chicks) were determined. In Experiment 1, Gln or Asn replaced 1% triammonium citrate in the low-protein diet (19% CP). In Experiments ( Key words : broiler chick, low-protein diet, crystalline amino acid, growth performance, body composition) 2002 Poultry Science 81:1156–1167 INTRODUCTION The excretion of N originating from dietary protein is largely responsible for the environmental issues arisen from intensive livestock production (Morse, 1995). In re- sponse, dietary means to decrease the impact on the envi- ronment of intense livestock production have successfully been implemented; one of which is the partial replace- ment of intact protein (e.g., soybean meal) with crystal- line, free amino acids (AA). Through this replacement, excesses of dietary AA are minimized in relation to their requirement, bringing the dietary protein closer to ideal protein and, in turn, decreasing the dietary CP content. Kerr and Easter (1995) calculated that for each percentage 2002 Poultry Science Association, Inc. Received for publication October 9, 2001. Accepted for publication March 7, 2002. 1 Journal Paper Number J-19505 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA, Project Number 3812, and supported by Hatch Act and State of Iowa funds. 2 Presented, in part, at the 2001 Midwest and Annual Meetings of the American Society of Animal Science. 3 To whom correspondence should be addressed: [email protected] uoguelph.ca. 4 Current address: Department of Animal and Poultry Science, Room 255 Animal Science and Nutrition Building, University of Guelph, Guelph, Ontario N1G 2W1, Canada. 1156 2 and 3, dietary concentrations of crystalline essential and nonessential amino acids, respectively, were increased incrementally in the low-protein diets (19 to 20% CP). In all experiments, chicks fed low-protein diets grew slower, used feed less efficiently, and retained less N and more ether extract than chicks fed the control diets ( P ≤ 0.05), despite additions of crystalline Gln or Asn and despite increased dietary concentrations of crystalline essential and nonessential amino acids. Chicks fed low-proteinand nonessential amino acids....
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- Spring '11
- NRC, Essential amino acid, Diets, EAA