Effects of season and parity on performance of lactating sows in a tropical climate

The effects of season in a tropical climate and parity on lactation performance of 106 Large White sows over several reproductive cycles (301 lactations in total) were studied in Guadeloupe (French West Indies, 16 (degree) N latitude, 61 (degree) W longitude) between January 1999 and March 2003. Two seasons were determined a posteriori from climatic parameters recorded continuously in a station close to the experimental unit. During the warm season, ambient temperature and relative humidity averaged 23.5 (degree) C and 0.831, respectively. In the hot season, the corresponding values were 26.0 (degree) C and 0.834, respectively. Over the 28-day lactation period, average daily food intake (ADFI) was lower (P < 0.001) and live-weight (LW) loss was higher (P < 0.05) during the hot season than during the warm season (3.9 v. 4.7 kg/day and 17 v. 12 kg, respectively). Growth rate and mean LW of piglets at weaning were lower (P < 0.05) during the hot season (203 v. 220 g/day and 7.0 v. 7.5 kg, respectively). However, the weaning-to-oestrus interval was not affected by season (5.4 days on average). The effect of season on ad libitum ADFI was less accentuated for primiparous than for multiparous sows (warm-hot 360 v. 1001 g/day). Irrespective of the season, ADFI was lower (P < 0.01) and piglet growth rate tended to be lower (P < 0.1) in primiparous than in multiparous sows (4.0 v. 4.4 kg/day and 205 v. 215 g/day, respectively). Moreover, the percentage of sows that returned to oestrus later than 5 days after weaning was higher in primiparous than in multiparous sows (25 v. 2%, P < 0.001). This study confirmed the negative effects of the hot season on performance of lactating sows raised in a humid tropical climate; the effects of season are dependent on parity number.