title: Methionine+cystine requirement of broiler chickens fed low-density diets under tropical conditions.
abstract: Two experiments were conducted to determine the M+C requirement of straight-run broiler chickens (Hubbard x Hubbard) during the period 4-21 (Exp. 1) and 21-40 (Exp. 2) days of age. Experiments were conducted during summer months (July-August) in open-sided houses, thus exposing chicks to chronic heat stress. Daily min-max temperature averaged 26-37C (Exp. 1) and 23-36C (Exp. 2). M+C deficient basal diets were formulated to contain low-nutrient-density, i.e., 2750 kcal per kg ME, 20.1% CP (Exp. 1), and 2780 kcal per kg ME, 17.0% CP (Exp. 2). Diets were supplemented with DL-methionine to provide total M+C level ranging from 0.64 to 0.89 % (six increments) and 0.54 to 0.79% (six increments), respectively in experiment 1 and 2. Requirements (0.95 of the maximum quadratic response) were found to be 0.77 and 0.75% total M+C, respectively for gain and feed efficiency, during 4-21 days; and 0.67% total M+C for both gain and feed efficiency during 21-40 days of age. Calculated on the digestible M+C basis, the estimates were 0.67 and 0.65% respectively for gain and feed efficiency during 4-21 days of age; and 0.60% for gain and feed efficiency during 21-40 days of age.
authors.affiliation: Department of Plant Sciences, Quaid-i-Azam University, Islamabad, Pakistan. usamaaftab@yahoo.com
authors.forename: Usama
authors.initials: U
authors.lastname: Aftab
authors.forename: Muhammad
authors.initials: M
authors.lastname: Ashraf
mesh_terms: D000375:Aging / Q000502:physiology; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D002645:Chickens / Q000254:growth & development* / Q000378:metabolism; D003553:Cystine / Q000008:administration & dosage* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008715:Methionine / Q000008:administration & dosage* / Q000378:metabolism; D009751:Nutritional Requirements; D009753:Nutritive Value; D011897:Random Allocation; D012621:Seasons; D014329:Tropical Climate; D015430:Weight Gain / Q000187:drug effects / Q000502:physiology
chemical_list: D004044:Dietary Proteins; D003553:Cystine; D008715:Methionine