Effects of dietary fat, vitamin E and zinc supplementation on tibia breaking strength in female broilers under heat stress

The objective of this experiment was to characterize the relationship between dietary fat and antioxidant supplementation, on tibia breaking strength (TS) and performance parameters in broiler chickens under heat stress. The chicks with a similar body weight were equally assigned to one of the two controlled-environment chambers from 21 to 56 days of age. The birds were fed diets as follows: 1) basal diet supplemented with 5% saturated fatty acid; 2) basal diet supplemented with 5% unsaturated fatty acids (2% canola oil plus 3% fish oil); and 3) the second diet supplemented with antioxidants (100 IU vitamin E and 50 mg/kg zinc); that birds received these 3 diets in two temperatures (22°C and 32°C). Results showed that feed conversion ratio was not influenced by antioxidant and fat supplementation but antioxidants could improve body weight gain and feed conversion ratio significantly; although, higher feed intake was observed (P < ı0.05). High environmental temperature showed deleterious effects, including: reduction of feed intake and live weight and increase of feed conversion ratio. Characterization of tibia bone showed that, the higher environmental temperature decreased length and width of tibia, ash and its strength, significantly (P < 0.05).