In ovo injection of glycerol and insulin-like growth factor (IGF-I) for broilers

Abstract

This study was conducted to determine the effects of in ovo feeding of glycerol (GLY) and insulin-like growth factor (IGF-I) on hatchability, biochemical parameters, intestinal morphometry, performance and carcass characteristics of broilers. For this three experiments were conducted; the first evaluated different concentrations of GLY (non-injected control and five saline solutions containing 0, 10, 20, 40 and 80 nmol/mL GLY); the second different doses of IGF-I (non-injected control and five saline solutions containing 0, 12.5, 25, 37.5 and 50 ng/IGF-I embryo); and the third the association of GLY and IGF-I (non-injected control and four saline solutions containing 0, 10 nmol/mL GLY, 100 ng/mL IGF-I and GLY + IGF- I). Injections were performed at 17 days of incubation. In the first experiment, doses of 10, 20 or 40 nmol/mL GLY reduced (P<0.01) the incubation time and doses of 20, 40 or 80 nmol/mL GLY decreased (P<0.01) the glycemia. The dose of 80 nmol/mL GLY decreased (P=0.01) muscle glycogen and the doses of 40 or 80 nmol/mL GLY increased (P=0.02) the fructose 1,6-bisphosphatase (FBP) activity. The use of 20 or 40 nmol/mL GLY increased (P<0.05) the duodenum weight in the 1st and 7th days of age. The different concentrations of GLY increased (P=0.02) the breast weight at 7 days of age and the deposition of abdominal fat at 40 days of age. At 7, 14 and 21 days of age, doses 10 or 20 nmol/mL GLY resulted in broilers with better (P<0.05) performance. No effect of GLY was observed (P>0.05) on hatchability, glycerol kinase activity, hepatic glycogen content, intestinal morphometry and uric acid. In the second experiment, the dose of 50 ng/embryo IGF-I increased (P<0.05) the hatchability and muscle glycogen. Lower (P<0.01) glycemia and higher (P<0.01) FBP activity were observed with the injection of 12.5 ng or more of IGF-I/embryo. At 7 days of age, doses of 25, 37.5 or 50 ng/embryo IGF-I increased (P=0.04) the breast weight. The highest (P<0.01) villus height/crypt depth ratio in the duodenum was observed with injection of 12.5, 25 or 37.5 ng/embryo IGF-I after hatching and at 7 days of age with doses of 37.5 or 50 ng/embryo IGF-I in the jejunum and in the ileum with the different concentrations of IGF-I. No effect was observed (P>0.05) on incubation time, blood uric acid, performance or carcass characteristics. In the third experiment, the injections of GLY or IGF-I increased (P=0.01) the hepatic glycogen. Higher (P<0.05) muscle glycogen content and height villus in the jejunum and in the ileum after hatching were obtained with injection of GLY. The substances increased (P=0.05) the liver weight and decreased (P=0.05) FBP activity. At 7 days of age, lower (P<0.01) liver weight and greater (P=0.02) ileum weight were observed, respectively, with GLY and IGF-I. At 14 days of age, IGF-I resulted in broiler with higher (P<0.01) weight

gain and better (P=0.05) feed conversion. At 35 and 42 days of age, the use of GLY or IGF-I or GLY + IGF-I increased (P<0.01) feed intake and weight gain in relation to the non-injected group. No effects of the injected substances were observed (P>0.05) on hatchability, hatching time, glycemia and carcass characteristics at 42 days of age. It is concluded that GLY associated or not to IGF-I can be used as a substrate in in ovo nutrition to improve the performance of broiler chickens and that IGF-I can be used at dose of 50 ng/embryo to increase hatchability.