Relationship of Plasma Growth Hormone to Growth Within and Between Turkey Lines Selected for Differential Growth Rates

Abstract

The ontogeny of plasma growth hormone (GH) was determined within and between genetically-related turkey lines selected for differential growth rates. Blood samples were obtained at weekly intervals from hatching through 195 days of age from male and female poults of a slow-growing, randombred line (RBC-2), representing the base population, and a fast-growing line selected over 20 generations from RBC-2 for increased 16-wk body weight (F). Growth rate of the F line exceeded that of RBC-2 during the very early (0 to 14 day) posthatch period (P less than .05), but was not different from that of the RBC-2 line by 77 to 195 days of age. Males of both lines were larger than females at all ages (P less than .05). Plasma GH increased from hatching until 2 wk of age and declined thereafter in both lines. Differences between overall plasma GH concentrations of the lines were not observed during the 0 to 14 day period, but concentrations were higher (P less than .05) in RBC-2 than F birds thereafter (21 to 195 days of age). Plasma GH concentrations initially (0 to 14 days) were higher in females than in males for both lines (P less than .05), but thereafter (21 to 195 days) declined more rapidly and averaged lower overall in females than in males (P less than .05). Correlations between measures of GH and growth rate within lines over age were strongly positive (r = .83 to .93; P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Pattern of Growth and Plasma Growth Hormone Secretion in Turkeys Selected for Increased Egg Production

“…Males continued to have higher concentrations of GH than females throughout the growth period ( Figure 3). This finding is consistent with previous observations in turkeys (Vasilatos-Younken et al, 1988;Bacon et al, 1989). There was a line by sex interaction for posthatch plasma GH.…”

“…After 4 wk, Leghorns had higher GH concentrations as well as higher relative growth rates. In general, circulating GH is greatest when relative rates of growth are maximum in quail and turkeys (Vasilatos-Younken et al, 1988). Vasilatos-Younken and Zarkower (1987) reported a high correlation between plasma GH concentration per unit metabolic body size and growth rate in chickens.…”

Secretory Pattern of Growth Hormone, Insulin, and Related Metabolites in Growing Male Turkeys: Effects of Overnight Fasting and Refeeding

“…The general consensus is that GH is secreted in a pulsatile fashion and that this pattern of secretion depends on age and sex (Nir et al, 1987;Shaw et al, 1987;Johnson et al, 1987). Likewise, the circulating levels of GH vary within weight-selected populations of poultry as an inverse relation to BW (Coturnix: Bacon et al, 1987;chickens: Burke and Marks, 1982;Nir et al, 1987;turkeys: Proudman and Wentworth, 1980;Vasilatos-Younken et al, 1988). Alterations of the FIGURE 5.…”

Production and characterization of recombinant chicken insulin-like growth factor-II from Escherichia coli

“…While a number of studies have used RIAs for serum IGF-I to assess growth perform¬ ance in chickens (Huybrechts et al 1985, Vasilatos-Younken et al 1988, McGuinness & Cogburn 1990), it has not been possible to determine absolute levels because heterologous reference standards have been used, and there has been insufficient information regard¬ ing the cross-reactivity of cIGF-II in the IGF-I assays employed. The development of specific RIAs using the recombinant chicken peptides will overcome this problem, enabling absolute levels of chicken serum IGFs to be measured for the first time.…”