Effects of exposure to hot temperature and reduction of dietary protein level on performance of multiparous lactating sows

The effects of exposure to high ambient temperature (29 vs 20°C) and reduction of dietary crude protein (CP) level were tested on 59 multiparous Large White x Landrace sows. The control diet (R1) contained 17,6% of CP and 0,96% of lysine; the two low heat increment experimental diets (R2 and R3) were obtained by reducing CP content (14,2 and 15,2% for R2 and R3, respectively) and increasing fat content (R3). The dietary digestible lysine content per MJ of net energy (NE; 0,82 g/MJ NE) and essential amino acid contents were similar for all diets. Sows had free access to feed between the 7th (d7) and the 27th day (d27) of lactation. Exposure to 29°C resulted in a decrease of feed intake (4,22 vs 7,63 kg/d at 20°C between d7 and d27), a lower piglets’ growth rate (203 vs 272 g/d) and increased body weight loss (34 vs16 kg). Performance were maintained with the low CP diets (R2 + R3 vs R1) and total nitrogen excretion was reduced (- 22%) at 20°C. Such diets attenuated significantly the negative effects of high ambient temperature on NE intake and body weight loss (47,9 vs 40,9 MJ NE and 30 vs. 40 kg, respectively). Creep feed intake was significantly higher for piglets suckling sows exposed at 29°C. Neither ambient temperature nor diet affected the weaning to estrus interval (4,9 d on average).