The study objective was to characterize effects of early gestation in utero heat stress (IUHS) on postnatal fasting heat production (FHP) and blood biomarkers associated with metabolism in growing pigs. Based on previous observation of increased postnatal core body temperature set point in IUHS pigs, we hypothesized that FHP would be altered during postnatal life because of IUHS. Pregnant first-parity gilts were exposed to thermoneutral (TN; = 4; 17.8 ± 0.1°C) or heat stress (HS; = 4; cyclical 28 to 38°C) conditions from d 30 to 60 of gestation. At weaning (21 d of age), 2 median-weight male pigs (1 barrow and 1 boar) were selected from each litter ( = 8 in utero TN [IUTN] and 8 IUHS pigs) and then housed in TN conditions based on age. Blood samples were collected at 8, 9, and 10 wk of age when pigs were in a fed state to analyze thyroxine (T4) and triiodothyronine (T3) concentrations. Pigs were trained to enter an indirect calorimeter from wk 8 through 10 of life and then acclimated over a 24-h period 1 wk prior to testing. At 12 wk of age, pigs were fasted for 24 h, and then indirect calorimetry was performed on individual pigs over a 23-h testing period to determine FHP and the respiratory quotient in 3 intervals (0900 to 1700 h, 1700 to 0000 h, and 0000 to 0800 h). Body weight was determined before and after testing and was similar for all pigs ( = 0.77; 37.0 ± 0.5 kg BW). Data were analyzed using PROC MIXED in SAS 9.4. No boar vs. barrow differences were observed with any analysis. Overall, FHP per kilogram BW was greater ( = 0.03; 12.1%) in IUHS pigs compared with IUTN pigs. Fasting heat production per kilogram BW was greater ( < 0.01; 19.8%) from 0900 to 1700 h compared with 1700 to 0000 h and 0000 to 0800 h and was greater (10.9%) from 1700 to 0000 h compared with 0000 to 0800 h. The RQ did not differ by in utero treatment ( = 0.51; 0.72 ± 0.01); however, the RQ was increased ( < 0.01; 13.0%) from 1700 to 0000 h compared with 0900 to 1700 h and 0000 to 0800 h. No other FHP and RQ differences were detected. Although no in utero treatment differences were observed for T4 ( = 0.11; 52.2 ± 6.2 ng/mL), T3 was greater overall ( = 0.04; 19.5%) in IUHS pigs than in IUTN pigs. In summary, FHP and circulating T3 were increased in IUHS pigs, and this may have implications for postnatal production efficiency in pigs gestated during hot summer months.

The objective was to determine the effects of immunization against gonadotropin-releasing hormone on reproductive characteristics in boars. A total of 72 boars were used in a randomized design with three treatments: single immunization (SI) (10 weeks of age) or double immunization (DI) (10 and 15 weeks of age) with Improvest® and intact controls (no Improvest®; CNT) (n=24/group). At 10, 15, 20, 25 and 40 weeks of age, blood was collected and serum harvested to evaluate testosterone concentrations. Testosterone concentrations were less for DI boars compared with CNT boars and SI boars at 20 and 25 weeks (P<0.001), but not at 40 weeks of age. At week 25, 18 pigs (n=6/group) were sacrificed and testes were removed, weighed and measured, and seminiferous tubules were examined and scored using histological slides of testes parenchyma. A sample of neck fat was assessed for boar taint aroma. All testicular measurements and weights and seminiferous tubule scores were less for DI boars compared with SI and CNT boars (P<0.001). More (P<0.05) SI and CNT boars had detectable boar taint aroma than DI boars. Libido was assessed at 32, 36, 47, 60 and 63 weeks of age and semen collected at 60 weeks of age was analyzed for indicators of quality. There were no effects of treatment (P=0.41) or treatment by week (P=0.71) on libido. Semen volume, gel weight and total number of sperm cells, determined in a subset of boars (n=3/treatment), were not different among treatments. Sperm concentration was greater for DI than SI (P=0.01), and tended to be greater for DI compared with CNT (P=0.10). Sperm motility tended to be greater for DI boars compared with CNT boars (P=0.066). In conclusion, our results show that there are no long-term effects of immunocastration on reproductive characteristics in boars.

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The study objective was to determine whether in utero heat stress (IUHS) affects piglet physiology and behavior following common production practices. A total of 12 gilts were confirmed pregnant and allocated to either heat stress (HS; n = 6) or thermoneutral (TN; n = 6) conditions on day 30–60 of gestation. At weaning (22.5 ± 2.3 days of age), 1 boar and 1 barrow of median weight were selected from each litter and transported for approximately 7 h. Piglets were then blocked into pens (n = 2/pen) by in utero treatment (IUHS (n = 12) or in utero thermoneutral (IUTN, n = 12)) and sexual status (boar (n = 6/in utero treatment) or barrow (n = 6/in utero treatment)). Plasma cortisol, non-esterified fatty acids (NEFA), insulin and glucose were evaluated 1 day prior to transport (pre-transport) and immediately after transport (post-transport). Behavioral data were collected on day 1–7 for 60 min at four different time points each day. In utero heat stressed piglets exhibited reduced cortisol concentrations compared to IUTN piglets immediately post-transport (p = 0.04). Glucose concentrations were not affected by in utero treatment. Insulin concentrations were reduced in IUTN piglets post-transport compared to pre-transport (p = 0.002), but no differences were detected for IUHS pigs. Non-esterified fatty acids tended to be reduced overall for IUHS vs. IUTN pigs (p = 0.08). Overall, IUHS piglets performed more drinking behaviors (p = 0.02) and tended to perform more aggressive behaviors (p = 0.07) than IUTN piglets in the 7 days post-transport. In summary, there was some evidence for altered physiological and behavioral responses among IUHS piglets compared to IUTN piglets following weaning and transport.