Effect of Feeding Levels and Physical Activities on Heat Production in Laying Hens under Different Ambient Temperatures

Abstract

Eight Single Comb White Leghorn laying hens were used to investigate the effects of feeding levels (FL), ad libitum and 40% feeding, and physical activities on heat production (HP) under different ambient temperatures (Ta) of 25, 29 and 33°C. HP were measured by the indirect calorimetry where each hen was observed for 48 h in each condition. Activity count (ACT), standing time (STN) and eating time (ETN) were also measured for the same 48 h. ACT was measured by the Actigraph and the STN and ETN were detected by the infra-red beam switches. HP decreased with the increase of Ta and with the decrease of food intake (FI). The daily ACT decreased significantly (P<0.05) at 33°C in the ad libitum fed hens in comparison with that of 29°C, and in the 40% fed hens ACT had a decreasing tendency with the increase of Ta. On the other hand, the daily STN increased significantly (P<0.05) at 33°C comparing with that of 25 and 29°C in both the ad libitum and 40% fed hens. HP in the 40% fed hens decreased by 24%, 17% and 17% at 25, 29 and 33°C, respectively in comparison with that of ad libitum fed hens. From the multiple regression equations, excluding the activity-related HP, an estimation of the increase of HP for 1 g of FI was done and it was approximately 3.9kJ at each Ta in the ad libitum fed hens. Almost 28% of the daily HP was related to the activity at each Ta. The hens changed their physical activities with the increase of Ta in both the ad libitum and 40% feeding and the maintenance energy expenditure may decrease with the increase of Ta.

Keywords

• heat production
• physical activity
• ambient temperature
• feeding level
• laying hen