Developmental Changes of Plasma Insulin, Glucagon, Insulin-like Growth Factors, Thyroid Hormones, and Glucose Concentrations in Chick Embryos and Hatched Chicks

Abstract

Developmental hormonal changes in Cobb 500 chick embryos and hatched chicks were determined by measuring plasma insulin, glucagon, insulin-like growth factor (IGF)-I, IGF-II, triiodothyronine, thyroxine, and glucose concentrations at different ages of embryogenesis and posthatch development. Plasma samples were obtained daily from 10 d of embryogenesis (10E) through 13 d posthatch and also at 17 and 21 d posthatch. A significant increase in plasma insulin was observed with increasing age from 10E to hatch. Plasma glucagon levels remained low until 17E, and then significantly increased approximately 3-fold at hatch, which corresponded with increasing plasma glucose levels during late embryo development. The plasma insulin to glucagon molar ratio of incubation from 14E to 17E ranged from 2 to 4, and was significantly higher than at any other time during incubation. These results indicate that insulin may be an important promoter of chick embryonic growth by the anabolic drive to promote protein deposition. Insulin and glucagon increased after hatch, which may be due to increased feed consumption and increased utilization of carbohydrates as the key energy source, compared with nutrients obtained through lipolysis and proteolysis in the embryos. Plasma triiodothyronine increased 4-fold from 18E to 20E, and thyroxine increased 3-fold from 16E to 19E. Insulin-like growth factor-I and IGF-II peaked at 14E. Insulin-like growth factor-I steadily increased above embryonic levels during the 3 wk of the posthatch period, whereas IGF-II levels steadily declined. These results suggest that IGF-II may be a more important functionary for chick embryonic development than IGF-I, and that IGF-I may be more important than IGF-II after hatch. The profile of metabolic hormones in the present study may help support an understanding of significant changes that occur in embryonic development and posthatch growth in chicks.

Changes of Plasma Growth Hormone, Insulin-Like Growth Factors-I, Thyroid Hormones, and Testosterone Concentrations in Embryos and Broiler Chickens Incubated under Monochromatic Green Light

“…Plasma IGF-I is detectable as early as embryonic d 10, it increases until a plateau is reached from embryonic d 13 to d 18, and it decreases before hatching (Lu et al, 2007). In the present study, the changes of plasma IGF-I levels during the embryonic period are similar to those of Lu et al (2007). Besides, we observed that plasma IGF-I also dramatically increased and reached a plateau with age after hatching.…”

“…The decline in plasma GH preceded the decline in circulating IGF-I, suggesting that IGF-I and GH are weakly coupled during late posthatch development of the chicken. Besides, we found a significant decrease in plasma IGF-I in day-old chicks, though Lu et al (2007) reported that plasma IGF-I levels increased in day-old chicks. Feed intake can decrease plasma levels of IGF-I in day-old chicks (Guernec et al, 2003), which might be the reason for the dramatically decrease in plasma IGF-I of day-old broilers in the current study.…”

“…In a previous study, Lu et al (2007) reported there were no significant effects of sex on plasma hormones levels in chick embryos. Therefore, we did not sex embryos in the current study.…”

“…Thyroid hormones are also crucial endocrine regulators of the embryonic development, hatching process, and posthatch metabolisms of broilers (Decuypere et al, 2000;Decuypere and Buyse, 2005). Lu et al (2007) found that both plasma T3 and T4 levels showed significant positive correlations with chick embryonic body weight (BW), suggesting that thyroid hormones might be important for maintaining normal growth. As an important gonadal hormone, plasma testosterone concentrations have positive correlation with growth rates of male broilers raised under intermittent white light provided by incandescent lamps (Kühn et al 1996).…”

Effect of Artificial and Natural Day Light Intensities on some Behavioral Activities, Plumage Conditions, Productive and Physiological Changes for Japanese Quail

“…Thyroid hormones especially T 3 have a multiple effects on vertebrate metabolism and development. A T 3 regulate basal metabolic rate and are essential for the maintenance and constant body temperature and protein and lipid metabolism (Collin et al, 2005;Lu et al, 2007). Also during development, T 3 stimulate both growth and differentiation of organs, their action can be direct, indirect or permissive (Zation et al, 1993).…”