Effects of exposure to high ambient temperature and dietary protein level on sow milk production and performance of piglets

The effects of high ambient temperature and level of dietary heat increment on sow milk production and piglet performance over a 28-d lactation were d etermined in 59 multiparous crossbred Large White x Landrace pigs kept at a thermoneutral (20 degreesC) or in a hot (29 degreesC) constant ambient tem perature. Experimental diets fed during lactation were a control diet (NP; 17.6% CP) and two low-protein diets obtained by reduction of CP level (LP; 14.2% CP) or both reduction of CP and addition of fat (LPF; 15.2% CP); the NE:ME ratio was 74.3, 75.6, and 75.8% for NP; LP, and LPF diets, respective ly. All diets provided 0.82 g of digestible lysine/MJ of NE, and ratios bet ween essential AA and lysine were above recommendations. Creep feed was pro vided after d 21 of lactation. Reduction of CP level did Rot influence (P > 0.10) milk production, milk composition, or piglet performance. Despite hi gher nursing frequency (39 vs 34 sucklings per day), milk production decrea sed (P < 0.01) from 10.43 to 7.35 kg/d when temperature increased from 20 t o 29 degreesC. At d 14, DM (18.6 vs 18.1%) and energy (4.96 vs 4.75 MJ/kg) contents in milk tended (P = 0.09) to be higher in sows kept at 29 degreesC . Over the 28-d lactation, piglet BW gain and BW at weaning decreased (P < 0.01) from 272 to 203 g/d and 9.51 to 7.52 kg, respectively, when temperatu re increased from 20 to 29 degreesC. Daily creep feed intake over the 4th w k of lactation was higher (P < 0.01) at 29 degreesC than at 20 degreesC (38 8 vs 232 g/litter, respectively), which was reflected in a greater increase in BW gain between wk 1 to 3 and wk 4 at the higher temperature (147 vs 13 0%); BW gain between weaning and d 14 postweaning was higher (P < 0.05) for piglets originating from sows kept at 29 degreesC (280 vs 218 g/d). In con nection with their lower growth rate, DM (31.2 vs 33.0%), protein (15.5 vs 16.0%), lipid (12.3 vs 13.9%), and energy (8.39 vs 9.09 kJ/g) contents in w eaned, slaughtered piglets were lower (P < 0.01) at 29 than at 20 degreesC. In conclusion, modification in the CP:NE ratio in order to decrease dietar y heat increment did not affect milk production and piglet performance in t hermoneutral or hot climatic conditions. Our results confirm the negative e ffect of high ambient temperatures on milk yield and emphasize the importan ce of creep feed supply to improve pre- and postweaning growth of piglets i n these conditions, especially when weaning occurs after 3 wk of age.