Effects of air-conditioned versus naturally ventilated housing during hot weather on the reproductive efficiency of gilts or sows

Abstract

One hundred and ninety-eight sows and gilts were used during the summers of 1975 through 1978 to evaluate air-conditioned housing as a means of reducing the deleterious effects of heat stress on reproductive efficiency. At weaning (1975 and 1976) or mating (1977 and 1978), females were randomly assigned by pairs to either an air-conditioned (AC) building or to a naturally ventilated open sided building (NV); they remained in these for 30 days after mating. Boars were housed in the AC building. Temperature in the AC building was kept at 22 ± 1°C. Average maximum ambient temperatures outside the NV building were 32°C in 1975, 31°C in 1976, 33°C in 1977 and 31°C in 1978; average minimum ambient temperatures were 19, 18, 20 and 19°C, respectively. Although not greatly different between treatments, farrowing rate (farrowed/mated) was higher in AC housing in 1975 and 1978. Days to estrus after weaning (only available for 1975 and 1976), were less ( P<0.01) for AC compared with NV housed sows (6.5 ± 1.0 vs. 11.7 ± 1.1). During 1975, 1976 and 1977, total pigs born, number born alive and number alive at 7 and 14 days favored sows housed in AC, whereas the reverse was true for 1978. Stillbirths were greater for NV sows in 1978, with no difference between AC and NV sows during the other years. Average birth weights did not differ between treatments. These results suggest that housing sows in an air-conditioned building during hot weather for 30 days after weaning may marginally improve reproductive performance as measured by litter size and return to estrus after weaning.