Influence of increasing ambient temperature on performance of multiparous lactating sows

Sixty-three multiparous Large White sows were used to investigate the effects of five ambient temperature (T) levels (18, 22, 25, 27 and 29°C) and two dietary protein contents (14 and 17 %) on their lactation performance. At each temperature treatment, ambient temperature was maintained constant over the 21-d lactation period. Essential amino acids levels were similar in both diets. The animals were fed ad libitum between the 7th and the 19th day of lactation. Diet composition did not influence lactation performance. Over the 21-d lactation, the daily feed intake (FID) decreased from 5.67 to 3.08 kg/d between 18 and 29°C, respectively. This decrease was curvilinear and averaged 1.49, 3.25 and 10.20 MJ of digestible energy intake per day per extra degree between 18 and 25°C, 25 and 27°C and 27 and 29°C, respectively (FID, g/d = - 49502 + 1213 T – 31,5 T2 - 330 BW – 0,61 BW2, RSD = 1018, BW: body weight, kg). The gradient between skin and rectal temperatures was minimal (2°C) and constant at 27 and 29°C. This constancy of the gradient coincides with the marked reduction of feed intake. The respiratory rate increased from 26 to 124 breathes per min between 18 and 29°C which indicates that the evaporative critical temperature was below 22°C. The BW loss increased from 23 to 35 kg between 18 and 29°C but its estimated tissular composition remained constant. The piglet growth rate was almost constant between 18 and 25°C (241 g/d) and was reduced above 25°C (212 and 189 g/d at 27 and 29°C, respectively).