In utero heat stress and post-natal feeding behaviour, growth and carcass performance in pigs

Abstract. Heat stress (HS) experienced in utero could have long-term effects on pig performance and especially affects lean deposition rate during the growing finishing phase. The aim of the study was to compare the effects of two climatic conditions during gestation on feeding behaviour, growth performance and carcass composition. A total of 24 pregnant sows (12 gilts and 12 multiparous sows) were exposed to thermoneutral conditions (GTN; cyclic 18 to 24 °C) or HS conditions (GHS; cyclic 28 to 34 °C) from day 9 to 109 of gestation. Four male offspring (two entire males, EM and two castrated males, C) per sow were selected at 75 d of age and raised in 8 pens of 12 animals based on in utero temperature treatment and sex type. During the growing finishing period, feed was provided ad libitum and pigs were kept in thermoneutral conditions. Feed intake and feeding behaviour traits were recorded on a daily basis using single-place SKIOLD Genstar electronic feeders. Pigs were slaughtered at 156 d of age and carcass composition was measured by X-ray tomography. The interaction between sex and in utero environment was not significant (P>0.10) for any of the measured traits. The average daily gain (ADG) did not differ between EM and C pigs (1,082 vs 1,085 g/d; P>0.05). However, EM consumed less feed and had a better feed conversion ratio and leaner carcass than C (P<0.01 for each). As the daily number of meals was similar in EM and C, the lower feed intake in EM was related to a reduced meal size (359 vs 379 g/meal; P<0.01). Lower meal size (348 vs 390 g/meal; P<0.01), partially compensated by a higher number of meals (8.2 vs 7.6 meals/d; P<0.05), resulted in reduced feed consumption (2,597 vs 2,690 g/d; P<0.05) in GHS pigs compared to GTN pigs. GHS pigs tended to have a lower ADG (1,069 vs 1,098 g/d; P=0.08) than GTN pigs. In utero environment had no effect on carcass composition. In summary, heat stress during prenatal period appear to reduce performance and to modify feeding behaviour during the growing finishing phase but did not impact lean or adipose tissue accretion.