Resumo
The objective of this study was to assess the effect of ambient temperature (T) and feeding time (FT) on eggshell thickness (ST) and egg weight (EW) of broiler breeder hens. Thirty 44-week-old Ross 308 broiler breeder hens were randomly distributed into six environmentally controlled chambers and kept in individual cages. Three thermal treatments were applied: 20 ºC (T1), cyclic 20-30 ºC (30 °C between 1000 h and 1800 h) (T2), and 30 ºC (T3). Birds received 180 g of commercial breeder food at 0730 h (FT1) or 1530 h (FT2). There were two replications per treatment and egg collection was performed for seven days. The eggs from the birds at T1 and T2 fed at 1530 h (T1FT2 and T2FT2 respectively) were significantly heavier than those laid by hens at the same T when fed in the morning (T1FT1 and T2FT1); eggs from T1FT1 and T2FT1 were heavier than the eggs from T3, but there were no significant differences between them. Both T and FT had significant effects on ST, but no significant interactions were found. Birds fed at 1530 h had the highest ST, whilst birds at T3 showed the lowest. Birds on T2 produced the thickest shells due to a higher ST in birds fed at 1530 h. Birds fed at 1530 h consumed their food between 1800 h and 2030 h, resulting in a higher dietary Ca2 + available during shell mineralization. The effect of FT and biphasic T treatments on ST in feed restricted broiler breeders should be interpreted considering the length of the high T phase to the actual food consumption time.(AU)