PATTERN OF GROWTH AND PLASMA GROWTH-HORMONE SECRETION IN TURKEYS SELECTED FOR INCREASED EGG-PRODUCTION

Male and female turkeys of a slow-growing line selected for increased 180-day egg production (Line E) and its faster growing randombred control (RBC1) were sampled weekly for BW and plasma growth hormone (GH) content. Hatching weights were higher for RBC1 than Line E poults, but no difference was observed between sexes. The pattern of growth of the two lines, as described by the Gompertz equation, was different in magnitude of growth [BW at point of inflection (POI) and asymptote] but not in form (slope and age at POI and age at asymptote). Males achieved higher weights at POI and asymptote but took longer to reach these weights. Slope at POI was greater for females than for males. Plasma GH was higher in Line E than in RBC1 at hatching but higher in RBC1 than in Line E from Weeks 7 to 28. Males had higher concentrations of circulating plasma GH than females at all ages. The GH pool size was maximal at 5 wk for females and 10 wk for males. Maximal concentrations of circulating GH preceded maximal GH pool size by several weeks.