Stress Influencing On Food Intake And Regulatory Mechanism In Broilers

A series of experiments in different aspects were conducted to study the effects of corticosterone on food intake in broilers. Besides CRFmRNA gene expression was conducted to discuss the mechanism of corticosterone on appetite. And different feeding scheme or water with glucose influencing on corticosteone level was also studied.The effects of long-term dietary administration of corticosterone (CORT) on food intake in broilers were evaluated. Mimiced chronic stress by high energy diet (HED) and low energy diet (LED) supplemented with corticosterone(30mg/kg).Chronic stress decreased energy efficiency in all stressed groups, improved food intake and daily energy intake obviously(P<0.05)in HED stress group of neonatal chicks, not in LED stress group of neonatal chicks.Chronic stress had no influence on food intake but an increasing tread on daily energy intake in stressed group of growing broilers, while food intake and daily energy intake expressed as relative cumulative food intake and relative cumulative energy intake were increased obviously in all stress groups. Furthermore chronic stress decreased significantly(P<0.05) CRFmRNA gene expression in HED stressed group of neonatal chicks, but not in LED stressed group of neonatal chicks, and increased leptin level in all stressed groups. The results demonstrated corticosterone administration could improve food intake and energy intake in broilers, and the limitation of gastrointestinal tract could cover the effects of corticosteone on food intake in LED stressed groups Appetite increased by corticosterone administration attributed to high dose corticosterone feedback inhibiting on CRFmRNA in circulating and high energy gained in stressed broilers, and corticosterone could weaken the ability of leptin decreasing food intake.The effects of long-term dietary administration of corticosterone (CORT) on the glucose or sucrose intake in broilers were studied. One half of the experimental chickens were assigned to drink water supplemented with glucose or sucrose, and another half of chicken were supplied with tap water supplemented with saccharin serving as control groups. Chronic stress mimiced by corticosterone increased glucose intake, and had no influence on sucrose intake, but improved significantly energy from sucrose (P<0.05). Contrast with stressed groups supplemented with saccharin, there was no discrepancy on food intake, relative cumulative food intake and daily energy intake, while increased relative cumulative energy intake in stressed groups supplemented with glucose and sucrose. The results showed chronic stress could have a preference for glucose or sucrose.The results also showed more glucose or sucrose intake could resist stress.ICV or subcutaneous injection corticosterone on food intake in neonatal chicks was evaluated. The results showed ICV corticosterone improved obviously food intake during 0-1H (P<0.05), and had no influence on food intake during 1-3H. ICV corticosterone decreased CRFmRNA gene expression in hypothalamus of neonatal chicks and increased plasm NPY level, which demonstrated CRFmRNA decreased could be achieved through inhibiting directly by ICV corticosterone. Furthermore food intake increased was the results of CRFmRNA decreased and NPY level improved together. And that coricosterone concentration decreased steadily weakened the ablitity of corticosterone inhibiting on CRFmRNA, resulting in food intake indistinctively during 1-3H.The 3d and 5d ages of neonatal chicks were chosen to subcutaneous corticosterone (4mg/kg). Contrast with control groups, subcutaneous corticosterone had on influence on food intake during 0-1H, but increased obviously food intake during 1-3H or 1-5H in stressed groups(P<0.05), Furthermore CRFmRNA gene expression level in hypothalamus was also decreased in stressed group.The results showed food intake increased could be achieved by corticosterone feedback inhibiting on CRFmRNA. Besides the difference of injection ways between ICV corticosterone and subcutaneous corticosterone resulted in the discrepancy of food intake in time slot.Different feeding scheme or water with glucose on corticosterone level in neonatal chicks was also studied. The results showed blood index in neonatal chicks under ad libitum kept steadily, while there was a"high- low-high"fluctuating in neonatal chicks under fixed feeding amount, the same with corticosterone under fixed HED feeding amount, but there was no reason that corticosterone kept constantly under fixed LED feeding amount, needed to be explored. The results also showed HED contributed to induce resistance, elevate corticosterone production. Besides under fixed feeding amount, water with glucose supplied, there was a constantly trend on blood index and corticosterone level in neonatal chicks...