Influence of high ambient temperature on performance of reproductive sows

Abstract Two trials were conducted on pure Large White multiparous (Trial 1, n = 36) and primiparous (Trial 2, n = 24) sows exposed to an ambient temperature within the zone of thermal comfort (18 or 20 °C) or above the evaporative critical temperature (27 or 30 °C). During a 3-week lactation, all sows in Trial 1 and those maintained at 30 °C in Trial 2 were fed ad libitum whereas sows at 20 °C in Trial 2 were paired-fed with those at 30 °C. The same standard diet containing 17.2% crude protein, 0.84% lysine and 13.0 MJ DE/kg was used during lactation. Single blood samples were drawn from the jugular vein before the morning meal at day 107 of gestation, at days 13 and 20 post-partum (p.p.), at days 1 and 12 post-weaning in Trial 2. After weaning, sows were checked daily for oestrus in the presence of a mature boar. Daily feed intake was lower at 27 °C than at 18 °C from day 4 p.p. until weaning in Trial 1 (−28%) and very low in both groups of sows in Trial 2 (2.8 kg/day). Lactational loss of sow liveweight did not differ between groups in Trial 1 whereas it was lower at 30 °C than at 20 °C in Trial 2 (1.32 vs. 1.80 kg/day, P