title: Dietary thyroid hormone improves growth and muscle protein accumulation of black-boned chickens.
abstract: 1. The objective of the study was to examine the effect of dietary thyroid hormone on performance and muscle protein accumulation of black-boned chickens. 2. A total of 720 1-d-old birds was housed in 24 pens and assigned to 4 diets containing triiodothyronine (T3) at 0, 0.1, 0.3 or 0.5 mg/kg. 3. The trial was split into starter (0 to 4 weeks) and grower (5 to 8 weeks) phases. At the beginning of the grower phase, each pen was split into two; one subgroup was fed basal diet (T3-) and the other continued with T3-added diet (T3+). 4. Dietary T3 at 0.1 mg/kg improved average daily body weight gain until week 6 but retarded it thereafter. However, T3 at 0.5 mg/kg depressed growth throughout the whole period. During weeks 7 to 8, T3 retarded growth, whereas growth recovered when T3 was withdrawn from the diet. 5. Birds fed the diet containing 0.1 mg/kg during weeks 0 to 4 and those receiving basal diet during weeks 5 to 8 showed the greatest thigh muscle growth, but this growth was depressed when they were fed the 0.5 mg/kg diet during weeks 0 to 8. 6. Serum T3 concentration was increased, while thyroxine (T4) concentration was decreased by dietary T3 treatment at 2 weeks old. At 4 weeks old, T3 and T4 concentrations decreased. At 6 and 8 weeks old, among T3-treated groups the serum T3 concentration of the T3- group was higher than that of the T3+ group. 7. In conclusion, dietary T3 improved weight gain and muscle growth of black-boned chickens before week 6, whereas supplementation depressed growth after 6 weeks. Optimum dietary T3 concentrations showed a carry-over effect on both body weight gain and thigh muscle growth.
authors.affiliation: College of Animal Science and Technology, Hunan Agricultural University, Hunan, Changsha, P R China. heyujia@hotmail.com
authors.forename: J H
authors.initials: JH
authors.lastname: He
authors.forename: M H
authors.initials: MH
authors.lastname: Cao
authors.forename: F X
authors.initials: FX
authors.lastname: Gao
authors.forename: J H
authors.initials: JH
authors.lastname: Wang
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001842:Bone and Bones / Q000502:physiology*; D002645:Chickens / Q000254:growth & development*; D004032:Diet / Q000662:veterinary*; D004305:Dose-Response Relationship, Drug; D009124:Muscle Proteins / Q000187:drug effects* / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D010858:Pigmentation / Q000502:physiology; D013972:Thyrotropin / Q000097:blood; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*
chemical_list: D009124:Muscle Proteins; D014284:Triiodothyronine; D013972:Thyrotropin