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Characterizing the sow physiological response to an increased heat load is essential for effective heat stress mitigation. The study objective was to characterize the effects of a 400-min heating episode on sow heart rate variability (HRV) at different reproductive stages. HRV is a commonly used noninvasive proxy measure of autonomic function. Twenty-seven sows were enrolled in the study according to their gestation stage at time of selection: 1) nonpregnant (NP; n = 7), 2) mid-gestation (MID; 57.3 ± 11.8 d gestation; n = 11), and 3) late-gestation (LATE; 98.8 ± 4.9 d gestation; n = 8). The HRV data utilized in the study were collected from each pig as the dry bulb temperature in the room increased incrementally from 19.84 ± 2.15 °C to 35.54 ± 0.43 °C (range: 17.1–37.5 °C) over a 400-min period. After data collection, one 5-min set of continuous heart rate data were identified per pig for each of nine temperature intervals (19–20.99, 21–22.99, 23–24.99, 25–26.99, 27–28.99, 29–30.99, 31–32.99, 33–34.99, and 35–36.99 °C). Mean inter-beat interval length (RR), standard deviation of r-r intervals (SDNN), root mean square of successive differences (RMSSD), high frequency spectral power (HF), sample entropy (SampEn), short-term detrended fluctuation analysis (DFAα1), and three measures (%REC, DET, LMEAN) derived from recurrence quantification analysis were calculated for each data set. All data were analyzed using the PROC GLIMMIX procedure in SAS 9.4. Overall, LATE sows exhibited lower RR than NP sows (P < 0.01). The standard deviation of r–r intervals and RMSSD differed between each group (P < 0.01), with LATE sows exhibiting the lowest SDNN and RMSSD and NP sows exhibiting the greatest SDNN and RMSSD. Late-gestation sows exhibited lower HF than both MID and NP sows (P < 0.0001), greater DFA values than NP sows (P = 0.05), and greater DET compared to MID sows (P = 0.001). Late-gestation also sows exhibited greater %REC and LMEAN compared to MID (P < 0.01) and NP sows (all P < 0.01). In conclusion, LATE sows exhibited indicators of greater autonomic stress throughout the heating period compared to MID and NP sows. However, temperature by treatment interactions were not detected as dry bulb increased. Future studies are needed to fully elucidate the effect of gestational stage and increasing dry bulb temperature on sow HRV. [ABSTRACT FROM AUTHOR]

The metabolic heat production of modern pigs has increased by an average of 16%, compared with sows of 30 years ago. Therefore, it is likely that temperature recommendations require updating to meet the needs of modern pigs. The objective of this study was to evaluate whether different reproductive stages of sows altered thermal preference and if current recommendations required updating. Twenty multiparous sows (3.4 ± 1.2 parity) in different reproductive stages (nonpregnant: n = 7; mid-gestation: 58.5 ± 5.68 d, n = 6; and late-gestation: 104.7 ± 2.8 d, n = 7) were tested. Thermal preference was individually tested, and sows could freely choose a temperature, using a thermal gradient between 10.4 and 30.5 °C. Sows were given 24 h to acclimate to the thermal apparatus. Before testing began, sows were given daily feed allotment and returned to the apparatus. Video from the 24-h test period was used to record sow behavior (time spent inactive), posture (upright and sternal and lateral lying), and location using instantaneous scan samples every 15 min. Data were analyzed using PROC MIXED procedure in SAS 9.4. A cubic regression model was used to calculate the sow’s most preferred temperature based on the location, or temperature, in which they spent the most time. The preference range was calculated using peak temperature preference ±SE for each sow. The reproductive stage altered where sows spent their time within the thermal gradient (P < 0.01). Late-gestation sows preferred cooler temperatures (14.0 °C) than mid-gestation (14.8 °C; P < 0.01) and nonpregnant sows (14.8 °C; P < 0.01). In summary, sow thermal preferences were within the lower half of the current recommended range (10 to 25 °C). This indicates that temperatures at the higher end of the recommended range could be uncomfortable to sows and that the thermal comfort zone of sows may be narrower than recommendations indicate. [ABSTRACT FROM AUTHOR]

In utero heat stress (IUHS) increases the energy requirements of pigs during postnatal life, and this may compound weaning and transport stress. The study objective was to evaluate and mitigate the negative effects of IUHS following weaning and transport through the provision of a nutrient-dense (ND) nursery diet formulated to meet the greater energy requirements of IUHS pigs during the first 14 d post weaning and transport. Twenty-four pregnant gilts were exposed to thermoneutral (TN; n = 12; 17.5 ± 2.1 °C) or heat stress (HS; n = 12; cycling 26 to 36 °C) conditions for the first half of gestation (day 6 to 59) and then TN conditions (20.9 ± 2.3 °C) until farrowing. Nine TN gilts and 12 HS gilts produced litters. At weaning (16.2 ± 0.4 d), mixed sex piglets (N = 160; 4.78 ± 0.15 kg body weight [BW]) were transported (loading + transport + unloading) for 11 h 40 min. Following transport, piglets were blocked into pens (n = 4 pigs/pen) by in utero and dietary treatments: in utero thermoneutral (IUTN) + control (C) diet (n = 10 pens), IUTN + ND (n = 10 pens), IUHS + C (n = 10 pens), and IUHS + ND (n = 10 pens). Treatment diets were fed from day 1 to 14 post weaning and transport (period 1), and the C diet was fed to all pigs from day 14 to 35 post weaning and transport (period 2). Production measures were taken in 7 d intervals to calculate average daily gain (ADG), average daily feed intake (ADFI), average daily net energy intake (ADEI), gain: feed, and gain: net energy intake. Blood samples were collected prior to transport, following transport, and on days 2, 7, 14, 28, and 35 post weaning and transport to analyze cortisol, glucose, insulin, and nonesterified fatty acids. Behavior was assessed through video-recording on days 3, 5, 8, 11, and 13 post weaning and transport. In period 1, ADG was reduced (P = 0.04; 20.0 g/d) in IUHS vs. IUTN pigs. Pigs fed ND diets had reduced ADFI (P = 0.02; 9.3%) compared with C diet-fed pigs during period 1, which resulted in similar ADEI (P = 0.23; 1,115 ± 35 kcal/d). During transport, cortisol was decreased (P = 0.03; 25.8%) in IUHS vs. IUTN pigs. On day 2, glucose was decreased (P = 0.01; 13.8%) in IUHS vs. IUTN pigs. No in utero treatment-related behavior differences were observed but lying was reduced (P = 0.03; 6.5%) and standing was increased (P = 0.04; 14.1%) in ND vs. C pigs overall. In summary, IUHS reduced growth performance in pigs following weaning and transport, and providing an ND diet did not rescue the lost performance. [ABSTRACT FROM AUTHOR]

The study objective was to determine the direct effects of rapid cooling after acute hyperthermia on intestinal morphology and inflammatory response in pigs. In four repetitions, male pigs (N = 36; 88.7 ± 1.6 kg) were exposed to thermoneutrality (TN; n = 3/rep; 19.5 ± 0.1°C) for 6 h or heat stress (HS; 36.4 ± 0.1°C) for 3 h, followed by a 3-h recovery period of rapid cooling (HSRC; n = 3/rep; rapid TN exposure and ice water dousing for 1.5 h) or gradual cooling (HSGC; n = 3/rep; gradual decrease from HS to TN). Rectal (TR) and gastrointestinal tract (TGI) temperatures were obtained every 15 min for 6 h. In repetitions 1 and 2, blood was collected at 60 and 180 min during HS and 30 and 60 min during recovery, and then pigs were euthanized at 180 min of recovery and duodenum, ileum, and colon tissue were collected to evaluate intestinal morphology. HS increased (P < 0.01) maximum TR (40.7°C) and TGI (41.5°C) compared with TN treatment (38.9 and 39.3°C, respectively). Recovery reduced TR (P < 0.01; 0.4°C) in HSRC vs. HSGC pigs, but TGI was similar (40.7°C). HSRC reduced (P < 0.01) villus height-to-crypt depth ratio in the duodenum (34%) and ileum (46%) vs. HSGC pigs. Serum LPS concentration was greater in HSRC pigs (P = 0.04; 68.5% and 52.4%, respectively) compared with TN and HSGC pigs, and TNF-α concentration tended to be greater (P = 0.06; 41.2%) compared with HSGC pigs during recovery. In summary, rapid cooling reduced TR but had no effect on TGI, and this may be linked to increased intestinal damage and a systemic inflammatory response. [ABSTRACT FROM AUTHOR]

Roughly 2 million cases of Salmonella infection are found in U.S. livestock each year, costing a hefty $1.4 billion, on average. Certain swine seem prone to shedding the bacteria during [...]