Hormones and Growth in Poultry

Abstract

The hormonal control of growth in poultry and other species is complex. The available evidence supports the concept that growth hormone and the thyroid hormones are the principal hormones responsible for the attainment of normal growth in the domestic fowl. Other hormones, including somatomedins, epidermal growth hormone, sex steroids, and vitamin D metabolites, are also involved in the control of growth. Considerable study will be required for the elucidation of the exact roles of the various hormones in avian growth.

Sexual dimorphism for growth in Muscovy ducks and changes in insulin-like growth factor I (IGF-I), growth hormone (GH) and triiodothyronine (T3) plasma levels

“…The data also suggested that GH concentrations decreased earlier in females (about 4 weeks of age) than in males (about 7 weeks of age) as observed previously in Pekin ducks [20], chickens [23] and turkeys [1]. In birds [20] and mammals [12], higher variable levels of GH observed in young compared to older animals and in males compared to females were related with pulsatile GH secretion of higher frequency and amplitude. A similar mode of secretion is suggested in Muscovy ducks by the very large coefficient of variation observed in our data until 8 weeks of age.…”

“…mL -1 between 1 and 9 weeks of age. In Pekin ducks, Scanes et al [20] showed that the decrease of plasma GH levels occurred earlier in females. In Muscovy ducks, a trend for higher GH concentrations in males compared to females was observed across the experimental period.…”

Effects of hyper- or hypothyroid status on growth, adiposity and levels of growth hormone, somatomedin C and thyroid metabolism in broiler chickens

“…Since both thyroid hormones depressed circulation GH levels (confirming the results of Harvey, 1983), while exogenous GH is a potent stimulator of liver 5'-monodeiodinase in chickens (Kfhn et al, 1985), the decrease found in peripheral T 4 conversion can be related to the decreased GH levels after thyroid hormone treatment. The lower GH levels in birds treated with thyroid hormones may be regulated by an increased negative feedback mechanism on the release of thyrotropin-releasing hormone (TRH), which is known to be a potent GH-secretagogue (Scanes et al, 1984). Also, the rather high GH levels in the MMI-fed broilers can be related to the diminished negative feedback of circulating thyroid hormones on TRH release in these birds.…”

Estimation of the genetic parameters of sexual dimorphism of body weight in 'label' chickens and Muscovy ducks

“…At a given age, they are more mature than males [12,18] Buvanendran [5] in a meat-type chicken line and 0.69 at 40 weeks by Singh et al [32] in a layer-type chicken line. Using REML in layer-type chicken lines, Hagger [14] and Tixier-Boichard et al [35] [20], Marks [21,22]) and the hormonal regulation of growth [4,29,37] contribute to the existence of sexual dimorphism. The correlation between the ratio of male to female body weight and sexual dimorphism was very high in chickens (0.98) which suggested concomitant evolution of both traits.…”