PSXIII-B-5 - Early Gestation Heat Stress Improved Measures of Sow Growth Performance but Did Not Impact Fetal Growth

Abstract: In utero heat stress negatively impacts fetal development and alters postnatal phenotypes in swine. However, the effects of heat stress (HS) on fetal growth during early gestation is relatively unknown. The study objective was to evaluate the effects of gestational HS on measures of fetal growth in early gestation. Twenty-three gestating gilts were exposed to HS (n = 12; cyclic 26-38°C) or thermoneutral (TN; n = 11; 18.5 ± 1.2°C) conditions from gestation d 6 ± 0.9 to 33 ± 1.7. Vaginal temperature was recorded in 15 min intervals using data loggers. Respiration rates (RR) were recorded daily at 0800, 1200, 1600, and 2000 h. All gilts were individually-housed, and limit-fed 1.82 kg/d. Gilt body weights (BW) were measured weekly and average daily gain and gain:feed were calculated. At gestation d 33 ± 1.7, gilts were harvested and fetal weights and counts were recorded. Data were analyzed using PROC GLIMMIX. Vaginal temperatures and RR were greater (P < 0.01) in HS (38.5 ± 0.1°C and 59 ± 2 bpm, respectively) versus TN gilts (38.0 ± 0.1°C and 29 ± 2 bpm, respectively). Although no initial BW differences were observed (P = 0.39; 148.8 ± 4.1 kg), final BW tended to be greater (P < 0.07) for HS (166.5 ± 3.8 kg) versus TN (156.8 ± 4.0 kg) gilts. Average daily gain was increased (P < 0.01) for HS (0.5 ± 0.1 kg/d) versus TN (0.3 ± 0.1 kg/d) gilts. Gain:feed was greater (P < 0.01) for HS (0.27 ± 0.03) versus TN (0.16 ± 0.03) gilts. No fetal weight (P = 0.23; 4.3 ± 0.2 g/fetus) or count (P = 0.15; 15.2 ± 0.9 fetuses/gilt) differences were detected. In conclusion, HS-exposure during early gestation improved measures of growth performance in gestating gilts but did not impact fetal growth or count.