Effects of heat stress on rectal temperature, respiratory rate and activity rates in peripartal sows and gilts.

Respiratory rate (RR) and rectal temperature (RT) of seven crossbred, second-litter sows and 11 crossbred gilts and rates of sitting and standing activity of 10 sows and gilts were measured from about 109 days of gestation to 5 days after farrowing at thermoneutral (T, 20.5 C) or hot (H, 29.8 C) ambient temperatures. Respiratory rate and RT were higher in heat-stressed sows and gilts (P~.05) before and during parturition. After parturition, neither RR nor RT differed (P>.05) among sows and gilts that were heat-stressed or held at thermoneutrality. Rectal temperature was elevated (P<.01) during the 4-hr period before parturition in all but the heat-stressed sows. Rectal temperature was higher (P<.01) during the 4 hr preceding parturition than during parturition for sows and gilts held at thermoneutrality. Rectal temperature was higher (P~.05) for gilts than for sows during parturition. Respiratory rate was lower (P<.05) during parturition than during the 4-hr period before parturition. From the time recording began until 12 hr before parturition the number of times standing-up, length of time standing and length of time sitting averaged 3.4 per hr, 1.6 min per hr and 4.1 min per hr, respectively. During the 12-hr period before parturition these activity rates were 5.0, 12.8 and 6.4, but during parturition they were only .2, .7 and 1.4, respectively. Activity rates were not affected by parity or ambient temperature. After parturition RT was lower (P<.05) than during parturition in all treatments, but at T it remained about .9 C (P<.001) above that during late gestation. Respiratory rate was lower (P<.01) after partu-