title: Estimation of nitrogen maintenance requirements and potential for nitrogen deposition in fast-growing chickens depending on age and sex.
abstract: Experiments were conducted to estimate daily N maintenance requirements (NMR) and the genetic potential for daily N deposition (ND(max)T) in fast-growing chickens depending on age and sex. In N-balance studies, 144 male and 144 female chickens (Cobb 500) were utilized in 4 consecutive age periods (I: 10 to 25 d; II: 30 to 45 d; III: 50 to 65 d; and IV: 70 to 85 d). The experimental diets contained high-protein soybean meal and crystalline amino acids as protein sources and 6 graded levels of protein supply (N1 = 6.6%; N2 = 13.0%; N3 = 19.6%; N4 = 25.1%; N5 = 31.8%; and N6 = 37.6% CP in DM). The connection between N intake and total N excretion was fitted for NMR determination by an exponential function. The average NMR value (252 mg of N/BW(kg)0.67 per d) was applied for further calculation of ND(max)T as the threshold value of the function between N intake and daily N balance. For estimating the threshold value, the principle of the Levenberg-Marquardt algorithm within the SPSS program (Version 11.5) was applied. As a theoretical maximum for ND(max)T, 3,592, 2,723, 1,702, and 1,386 mg of N/BW(kg)0.67 per d for male and 3,452, 2,604, 1,501, and 1,286 mg of N/BW(kg)0.67 per d for female fast-growing chickens (corresponding to age periods I to IV) were obtained. The determined model parameters were the precondition for modeling of the amino acid requirement based on an exponential N-utilization model and depended on performance and dietary amino acid efficiency. This procedure will be further developed and applied in the subsequent paper.
authors.affiliation: Institute for Animal Physiology and Animal Nutrition, Georg-August-University, 37073 Goettingen, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Samadi
authors.forename: F
authors.initials: F
authors.lastname: Liebert
mesh_terms: D000367:Age Factors; D000596:Amino Acids / Q000378:metabolism; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002645:Chickens / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D002149:Energy Intake; D005260:Female; D008297:Male; D008954:Models, Biological; D009584:Nitrogen / Q000008:administration & dosage* / Q000378:metabolism*; D009751:Nutritional Requirements; D009752:Nutritional Status; D011237:Predictive Value of Tests; D011897:Random Allocation; D012737:Sex Factors; D015430:Weight Gain / Q000187:drug effects
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D009584:Nitrogen