Poorya Dadvar - Department of Animal Science, Ilam Agricultural Research and Education Center, AREEO, Ilam, Iran
Ali Maddahian - Department of Agriculture, Payame Noor University, Tehran, Iran
Omid Dayani - Department of Animal Science, College of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran

The effects of in ovo feeding (۰ and ۱g/L) and dietary feeding (۰ and ۱g/kg diet) of betaine on hatchability, performance, body temperature and blood parameters of broiler chicks under heat stress condition, were investigated using ۶۰۰ fertile eggs (Ross ۳۰۸) for in ovo injection at ۱۷.۵d of incubation. After hatching, ۱۹۲ male chickens were divided into four groups: ۱- In ovo feeding of non-betaine solution and post-hatch diet without betaine, ۲- In ovo feeding of non-betaine solution and post-hatch dietary feeding ۱g per kg of betaine, ۳- In ovo feeding of ۱g per L betaine solution and post-hatch diet without betaine, and ۴- In ovo feeding of ۱g per L betaine solution and post-hatch dietary feeding ۱g per kg of betaine. The chicks were exposed to heat stress from ۷-۲۸d for ۴h/d. The results showed that body weight of hatched chicks and the hatched chick body weight to initial egg weight ratio, was significantly increased by in ovo feeding of betaine (P<۰.۰۵). The effects of in ovo feeding and dietary feeding of betaine resulted in higher feed intake (P<۰.۰۵) and daily weight gain (P<۰.۰۱) and improved feed conversion ratio (P<۰.۰۵) for ۷-۲۱d. Birds that received dietary betaine had more carcass, breast and leg weight than chickens receiving betaine-free diet at ۲۸d (P<۰.۰۵). The experimental treatments had no significant effect on carcass yield at d ۴۲. During heat stress between ۱۴ and ۲۱d age, the group that did not receive betaine (in ovo or dietary) had the highest cloacal temperature (P<۰.۰۱). The concentration of high-density lipoproteins, triglycerides and cholesterol in the blood of chickens that received betaine-free diet was significantly higher than other groups (P<۰.۰۵). In general, dietary betaine feeding improved the performance and carcass parameters and decreased blood lipids and cloacal temperature of chicks under heat stress conditions. However, these effects were not observed from days ۲۸ to ۴۲, which were free of heat stress.

carcass, cholesterol, cloacal temperature, in ovo injection