9
Heat Stress in utero Affects Piglets Later in Life
Heat stress is currently an issue in the swine industry, having been shown to decrease reproductive performance of boars and sows as well as alter growth and composition of growing pigs. Climate change and leaner production pigs, which are naturally more susceptible to heat stress, may accentuate this issue. These factors make it important to study heat stress in an attempt to quantify the production stages most vulnerable, allowing the industry to make adjustments accordingly. The objective of this study was to measure postnatal effects of in utero heat stress on thermal properties of growing pigs. Pregnant sows were placed in the Brody Environmental Chambers under either heat stressed (28-34°C: gestational heat stress, GHS) or thermo-neutral (18-22°C: gestational thermo-neutral, GTN) conditions throughout gestation. At 110d of gestation they were moved to the same farrowing facility and housed under thermo-neutral conditions. Gilt progeny (n=165) from these sows were weaned and moved to mechanically ventilated, fully slatted rooms at the University of Missouri Swine Research Finisher where the current work was conducted. Rectal, ear, and rump temperatures, and respiration rate (RR) were recorded twice weekly from 3 to 6 months of age. Room temperature was recorded each time pig temperatures were taken, and they ranged over time and time of day from 23.01°C-29.78°C. Body weights were recorded every 3 weeks from 2 to 6 months of age. Data were analyzed using mixed model procedures (Proc Mixed; SAS Inst.). Temperatures were similar for GHS and GTN pigs overall (39.11°C, 35.61°C and 35.56°C for rectal, ear and rump temperatures, respectively). Increasing respiration rate is one of the major mechanisms used by pigs to regulate temperature, and it appears GHS pigs were able to maintain the body temperature with less effort, having lower RR (15.04±0.13 vs 15.83±0.15 breaths per min for GHS and GTN, respectively, P<0.001). Higher room temperatures at the time of measurement were associated with increased RR (12.28±0.49-19.62±0.49 breaths per min; P<0.001), though this did not differ by treatment. These data imply that metabolic differences exist between the two treatment groups whereby greater or lesser respiration rate is needed to maintain similar body temperatures. This could have implications on feed intake and efficiency, though housing both gilt groups together prevented us from collecting such data. Further quantification of treatment differences will allow producers to more accurately determine the value of cooling for pregnant sows.
Keywords:
Pigs, heat stress, in utero