Influence of high ambient temperatures on food intake and feeding behaviour of multiparous lactating sows

Forty multiparous Large White sows were used to investigate the effects of five ambient temperature levels (18, 22, 25, 27, and 29 degrees C) and two dietary protein contents on their feeding behaviour during lactation. At each temperature treatment, ambient temperature was kept constant over the 21-day lactation period. Dietary protein content was either 140 or 170 g/kg with essential amino acids levels calculated to be non-limiting. Photoperiod was fixed to 14 h of artificial light. The animals were given food ad libitum between the 7th and the 19th day of lactation. Feeding behaviour was not influenced by diet composition. Over the 13 days under ad libitum feeding conditions, voluntary food intake decreased from 7.80 to 3.50 kg/day between 18 and 29 degrees C, which was achieved through a decreased daily number of meals at the highest temperature (6.8 to 4.5 at 18 and 29 degrees C, respectively). No significant difference among temperatures was observed on meal size, even if the highest (1372 g) and the lowest (883 g) values were obtained at 18 and 29 degrees C, respectively. Rate of food intake was not influenced by temperature and averaged 133 g/min; consequently, decreased voluntary food intake under heat exposure resulted in reduced ingestion time (61 and 29 min/day at 18 and 29 degrees C, respectively). Hourly food intake peaked at the beginning and the end of the light period. If resulted in a mainly diurnal partition of food intake. This partition was significantly affected by temperature as proportionately 0.87 and 0.91 of total food intake occurred during the day at 27 and 29 degrees C, respectively, v. 0.81 on average between 18 and 25 degrees C. Number of meals was lower during the night (I I v. 5.2 during the day on average); if decreased with increased temperature both during the day and the night. Meal size was lower during the night (938 v. 1080 g during the day on average). The ratio between water and food intake was significantly higher at 29 degrees C (8.1 v. 4.2 l/kg on average between 18 and 27 degrees C). Standing activity averaged 124 min/day with no significant difference between temperatures.