VARIATION IN GROWTH-HORMONE, TRIIODOTHYRONINE (T3) AND LIPOGENIC ENZYME-ACTIVITY IN BROILER STRAINS DIFFERING IN GROWTH AND FATNESS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 47  (4) , 411-425
Abstract
Developmental changes in body weight, lipid deposition, growth hormone (GH) and triiodothyronine (T3) concentration and lipogenic enzyme (malic and citrate cleavage) activity from day 1 through 42 days of age were examined in 3 strains of broilers. The 3 strains from diverse genetic backgrounds had been similarly selected for growth rate and a preliminary investigation had shown strain 2 to be faster growing and fatter than strains 1 or 3. In the present experiment, day 1 body weight did not differ between strains but by 14 days of age, strain 2 birds were heavier than those in strains 1 and 3. By 42 days, body weights were similar for strains 1 and 2 but were greater than strain 3. Percent carcass fat did not differ between strains before 28 days of age. At 28 and 42 days, strain 2 had a higher percent body fat than strains 1 and 3. Females grew slower, but deposited more carcass fat than males. Plasma T3 levels did not differ between strains until 42 days of age when strain 2 had higher T3 levels than strains 1 or 3. Males of all strains had higher T3 levels than did females. The slower growing strain 3 had significantly elevated GH levels compared to the faster growing strain 2, while GH concentration of strain 1 was intermediate to the other strains. Males had greater GH levels from 14 to 42 days of age compared to females. There were no consistent strain or sex differences in lipogenic enzyme activity. The temporal patterns of enzyme activity were similar between strains and sexes.