Determining the effects of early gestation in utero heat stress on postnatal fasting heat production and circulating biomarkers associated with metabolism in growing pigs

Abstract

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.

Heat Stress Impacts Immune Status in Cows Across the Life Cycle

“…In utero hypothalamic-pituitary-adrenal axis programming also occurs in pigs (47). When in utero heat stressed pigs are exposed to postnatal stressors [i.e., handling, (48) or heat insult, (49)] they have higher cortisol concentrations and increased core temperature, respectively. It has been established that the immune system has lower priority in fetal nutrient partitioning than other systems, such as the nervous system and brain (50) which might explain the programming effect of systems regulated at the brain level (i.e., cortisol regulation and thermoregulation).…”

Maternal and fetal thyroid dysfunction following porcine reproductive and respiratory syndrome virus2 infection

“…The concentration of total triiodothyronine (T3) and total thyroxine (T4) in maternal and fetal serum were determined using commercially available RIAs (MP Biomedical, Irvine, CA, USA) for each analyte, which have previously been used with porcine samples [20]. Assays were conducted in duplicate in accordance with the manufacturer's directions with the exception that both samples and standards were diluted 1 in 4 prior to T4 assay to effectively reduce sample viscosity and thereby improve assay performance.…”

“…Feed restriction for as little as 24 h has been shown to cause a significant decrease in the circulating T3 and T4 levels in swine [28]. There is also established interplay between feed intake and ambient temperatures [20,29,30] as well as additional alterations following adaptation to new diets [31]. Given that the control and infected gilts originated from the same genetic nucleus farm, the apparent susceptibility of the thyroid hormone system to environmental conditions leads us to posit that the observed pre-challenge difference likely stems from minor differences in the conditions between the facilities in which these two groups were housed.…”

Evaluating the Effects of In Utero Heat Stress on Piglet Physiology and Behavior Following Weaning and Transport

“…Pigs exposed to in utero heat stress (IUHS), defined as exposure of the fetus to maternal body temperatures above euthermic levels, are negatively affected throughout postnatal life [20]. For example, IUHS pigs exhibit a chronically elevated core body temperature [21], decreased head and bone weight as a percentage of body weight [22,23], increased circulating triiodothyronine (T 3 ) concentrations and fasting heat production [24], increased fat deposition and circulating insulin concentrations [25], as well as decreased protein accretion [23]. However, little is known about the effects of IUHS in piglets after common production stressors on welfare measures such as the physiological and behavioral stress response.…”

“…We hypothesized that IUHS piglets would exhibit a greater physiological and behavioral stress response (increased cortisol; increased aggression and standing, decreased eating, drinking, lying, interaction with straw, and huddling with a pen mate) following weaning and transportation. Additionally, because previous work demonstrated that IUHS pigs have a greater maintenance requirement when compared to IUTN pigs [24], indicators of energy availability and utilization were measured to account for the potential effect of metabolic stress on the physiological and behavioral response to a stressor. We further hypothesized that weaning and transport would lead to a more negative energy balance in IUHS piglets, as compared to their IUTN conspecifics, and this may contribute to reduced welfare.…”