Effects of nutritional regimes of physiological stress responses in broilers

Physiological stress was induced in broilers by feeding diets containing corticosterone (CS). Feeding CS at an inclusion level of 15 mg/kg of diet from d 21 to 35 resulted in stress responses including decreased weight gain, increased feed intake, increased feed conversion, and increased heterophil to lymphocyte ratios. Experimentation was then conducted to evaluate the effects of physiological stress on amino acid (AA) digestibility. Feeding broilers 15 mg of CS/kg of diet from 21 to 30 d of age resulted in decreased weight gain, impaired feed conversion, and increased liver weight, thus validating the occurrence of stress. However, AA digestibility was not affected by physiological stress in this research. As AA digestibility was unaffected by stress, research was conducted to examine the possibility of stress amelioration through varying nutrient regimens. Thus, two experiments were conducted to examine the effects of increasing dietary glucogenic AA, ketogenic AA, L-Trp, AA density, carbohydrate density, and L-carnitine for broilers fed 15 mg of CS/kg of diet. No nutrient regime resulted in stress amelioration during the stress period, as feeding CS to broilers receiving any nutrient treatment resulted in impaired live performance. However, feeding increased L-Trp during stress resulted in improvements in weight gain during post-stress recovery, although feeding L-Trp during stress also resulted in decreased carcass yield. A final experiment was conducted to examine the effects of providing stressed broilers supplemental electrolytes or sucrose in the drinking water. This research utilized a lower CS inclusion level of 5 mg/kg of diet fed from d 21 to 30. Broilers fed CS in combination with water electrolytes had improved weight gain compared to other stress treatments. Also, feeding supplemental electrolytes or sucrose during stress resulted in improved feed conversion post-stress.