Effect of low-protein diets on growth performance and body composition of broiler chicks.
Three experiments were conducted to investigate 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 MEn/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 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 < or = 0.05), despite additions of crystalline Gln or Asn and despite increased dietary concentrations of crystalline essential and nonessential amino acids. Chicks fed low-protein diets excreted less N (P < 0.001) than did chicks fed the high-protein diets, and N excretion increased linearly (P < 0.001) with N intake. In summary, low-protein diets failed to support equal growth performance to that of high-protein control diets.
Bregendahl
K
K
Department of Animal Science, Iowa State University, Ames 50011, USA. kbregend@uoguelph.ca
Sell
J L
JL
Zimmerman
D R
DR
D000596:Amino Acids / Q000008:administration & dosage; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition; D002645:Chickens / Q000254:growth & development* / Q000502:physiology; D004032:Diet; D018753:Diet, Protein-Restricted; D004435:Eating; D002149:Energy Intake; D008297:Male; D009584:Nitrogen / Q000008:administration & dosage / Q000378:metabolism; D013025:Glycine max; D015430:Weight Gain; D003313:Zea mays
D000596:Amino Acids; D009584:Nitrogen