No abstract

A component of the stator of the yeast ATP synthase (subunit 4 or b) showed many cross-linked products with the homobifunctional reagent dithiobis[succinimidyl propionate], which reacts with the amino group of lysine residues. The positions in subunit 4 that were involved in the cross-linkings were determined by using cysteine-generated mutants constructed by site-directed mutagenesis of ATP4. Cross-linking experiments with the heterobifunctional reagent p-azidophenacyl bromide, which has a spacer arm of 9 A, were performed with mitochondria and crude Triton X-100 extracts containing the solubilized enzyme. Substitution of lysine residues by cysteine residues in the hydrophilic C-terminal part of subunit 4 allowed cross-links with subunit h from C98 and with subunit d from C141, C143, and C151. OSCP was cross-linked from C174 and C209. A cross-linked product, 4+beta, was also obtained from C174. It is concluded that the C-terminus of subunit 4 is distant from the membrane surface and close to F(1) and OSCP. The N-terminal part of subunit 4 is close to subunit g, as demonstrated by the identification of a cross-linked product involving subunit g and the cysteine residues 7 or 14 of subunit 4.

This study aimed at comparing the growth and mineralization of the femur, tibia, and metatarsus of male and female broiler chicks. On the day of hatch, 100 male and 100 female Ross 308 broiler chicks were transferred stainless cages with 10 birds per cage. On d 7, 14, 21, 28, 35, and 42, five males and five females were sacrificed and their femur, tibia, and metatarsus were collected. Results showed that the tibia was the heaviest and the longest and contained the highest content of ash and calcium (Ca) among the three leg bones. The femur had the greatest diameter. The weight, length, diameter, and ash weight of the femur, tibia, and metatarsus linearly increased with age. The ash, Ca, and phosphorus (P) content in the femur and the tibia quadratically increased with age; by contrast, these parameters in the metatarsus linearly increased with age. The bones grew faster in 1 to 21 d of age. The weight, diameter, and ash weight of the three bones of males were higher than those of females. The Ca to P ratio of the three bones (femur, tibia, and metatarsus) was approximately 2.0:1. These data indicate that there are differences in bone growth and mineralization among the femur, tibia, and metatarsus of male or female broiler chicks.

The objective of this study was to investigate the optimal zinc (Zn) requirement of broiler chickens based on Zn retention. On the day of hatch, 350 male Ross 308 broilers were randomly assigned to seven treatments with five replicates of ten birds each. Zinc was supplemented as ZnSO 4 •7H 2 O at 0, 20, 40, 60, 80, 100, or 120 mg/ kg in the starter diet (fed from 1 to 21 d of age) and at 0, 16, 32, 48, 64, 80, or 96 mg/kg in the grower diet (fed from 22 to 42 d of age). The analyzed Zn levels were 34.98 and 27.57 mg/kg in the basal starter and grower diets, respectively. Supplemental Zn levels did not influence body weight gain, feed intake, feed conversion ratio, or liver Zn content of broilers at 21 and 42 d of age (p>0.05). Tibia ash Zn content of 21-d-old broilers increased when Zn supplementation level increased from 0 to 40 mg/kg Zn in (p<0.05). The highest breast muscle Zn content in 42-d-old broilers was observed when 100 and 80 mg Zn/ kg was supplemented in the starter and grower diets, respectively. Fecal Zn content, Zn intake, Zn excretion, and Zn retention of 31-to 33-d-old broilers linearly increased with supplemental Zn levels (p<0.05). Zinc retention values, calculated as the difference between Zn intake and Zn excretion, were negative, about zero, and positive when starter/grower diets were supplemented with 0/0 and 20/16, 40/32, and 60/48 and 120/96 mg/kg, respectively. These results indicate that supplementing 40 and 32 mg Zn/kg in starter and grower diets, respectively, promote the growth performance of broiler chickens, while reduce Zn excretion in the environment.