J. S. Johnson

Rapid cooling after acute hyperthermia alters intestinal morphology and increases the systemic inflammatory response in pigs.

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.

Evaluating the behavior, growth performance, immune parameters, and intestinal morphology of weaned piglets after simulated transport and heat stress when antibiotics are eliminated from the diet or replaced with L-glutamine.

Study objectives were to evaluate the effects of post-weaning transport during heat stress (HS) and thermoneutral (TN) conditions when dietary antibiotics are removed or replaced with a nutraceutical. Sixty mixed sex piglets from 10 sows ( = 6 piglets/sow) were weaned (18.8 ± 0.8 d of age) and then herded up ramps into 1 of 2 simulated transport trailers in either TN (28.8 ± 0.2°C) or HS (cyclical 32 to 37°C) conditions where they remained for 12 h. During the 12 h of simulated transport, fans were used to simulate air movement through the trailer, feed and water were withheld, and rectal temperature (T) was measured hourly. Following the 12 h simulated transport, piglets were unloaded from the trailer, weighed, and then housed individually in TN conditions [28.5 ± 0.1°C; 29.1 ± 0.1% relative humidity (RH)] and assigned to 1 of 3 dietary treatments balanced by weaning weight, sex, sow, and transport environment. Treatments were dietary antibiotics [A; = 20 piglets; 5.5 ± 0.2 kg BW; chlortetracycline (400 g/ton) + tiamulin (35 g/ton)], no dietary antibiotics (NA; = 20 piglets; 5.6 ± 0.2 kg BW), or 0.20% L-glutamine (GLU; = 20 piglets; 5.6 ± 0.2 kg BW) fed for 14 d. During the diet treatment period, feed intake (FI), BW, and behaviors were monitored daily. At the conclusion of the diet treatment period, all piglets were euthanized and intestinal samples were collected for histology. The T and post-transport BW loss were increased in HS (40.7°C and 0.43 kg, respectively) compared to TN-exposed (39.2°C and 0.27 kg, respectively) piglets during simulated transport. Throughout the 14 d dietary treatment phase, FI was greater overall ( < 0.01; 60.3%) in GLU compared to A and NA pigs, and tended to be greater (37.7%) in A compared to NA pigs. BW was greater overall ( < 0.01; 8.7%) in GLU and A compared to NA pigs, but no differences were detected between A and GLU pigs. Lying behavior was greater ( = 0.05; 11.7%) in NA compared to A and GLU piglets in the first 2 d following simulated transport. The villus height to crypt depth ratio was greater ( < 0.05) in the duodenum (12.1%) and jejunum (12.8%) for A and GLU compared to NA pigs, and greater in the ileum (15.6%) for GLU compared to A and NA pigs. In summary, withholding dietary antibiotics after weaning and transport can negatively affect piglet productivity and measures of intestinal morphology compared to dietary antibiotic administration and L-glutamine provision.

Effects of rapid temperature fluctuations prior to breeding on reproductive efficiency in replacement gilts.

Rapidly cooling pigs after heat stress (HS) results in a pathophysiological condition, and because rapid temperature fluctuations may be associated with reduced reproductive success in sows, it lends itself to the hypothesis that these conditions may be linked. Objectives were to determine the effects of rapid cooling on thermal response and future reproductive success in pigs. Thirty-six replacement gilts (137.8±0.9kg BW) were estrus synchronized and then 14.1±0.4 d after estrus confirmation, pigs were exposed to thermoneutral conditions (TN; n=12; 19.7±0.9°C) for 6h, or HS (36.3±0.5°C) for 3h, followed by 3h of rapid cooling (HSRC; n=12; immediate TN exposure and water dousing) or gradual cooling (HSGC; n=12; gradual decrease to TN conditions) repeated over 2 d. Vaginal (TV) and gastrointestinal tract temperatures (TGI) were obtained every 15min, and blood was collected on d 1 and d 2 during the HS and recovery periods at 180 and 60min, respectively. Pigs were bred 8.3±0.8 d after thermal treatments over 2 d. Reproductive tracts were collected and total fetus number and viability were recorded 28.0±0.8 d after insemination. HS increased TV and TGI (P=0.01; 0.98°C) in HSRC and HSGC compared to TN pigs. During recovery, TV was reduced from 15 to 105min (P=0.01; 0.33°C) in HSRC compared to HSGC pigs, but no overall differences in TGI were detected (P<0.05; 39.67°C). Rapid cooling increased (P<0.05) TNFα compared to HSGC and TN pigs during recovery-d 1 (55.2%), HS-d 2 (35.1%), and recovery-d 2 (64.9%). Viable fetuses tended to be reduced (P=0.08; 10.5%) and moribund fetuses tended to be increased (P=0.09; 159.3%) in HSRC compared to HSGC and TN pigs. In summary, rapid cooling prior to breeding may contribute to reduced fetal viability and reproductive success in pigs.

Early life thermal stress: Impact on future thermotolerance, stress response, behavior, and intestinal morphology in piglets exposed to a heat stress challenge during simulated transport1

Study objectives were to evaluate the impact of early life thermal stress (ELTS) on thermoregulation, stress response, and intestinal health of piglets subjected to a future heat stress (HS) challenge during simulated transport. From d 7 to 9 post-farrowing, 12 first-parity sows and their litters were exposed to thermoneutral (ELTN; 25.4 ± 1.1 °C w/heat lamp; n = 4), HS (ELHS; cycling 32-38 °C w/heat lamp; n = 4), or cold stress (ELCS; 25.4 ± 1.1 °C w/no heat lamp; n = 4) conditions, and then from d 10 until weaning all piglets were exposed to thermoneutral (TN) conditions (25.3 ± 1.9 °C w/heat lamp). During the ELTS period, respiration rate, rectal temperature (TR), and skin temperature (TS) of three mixed-sex piglets per dam were monitored daily (0800, 1200, 1600, 2000 h). At 13 ± 1.3 d of age, temperature recorders were implanted intra-abdominally into all piglets. At weaning (20.0 ± 1.3 d of age), piglets were bled and then herded up a ramp into a simulated transport trailer and exposed to HS conditions (cycling 32-38 °C) for 8 h. During the 8 h simulated transport, core body temperature (TC) and TS were assessed every 15 min. After the simulated transport, piglets were unloaded from the trailer, bled, weighed, and then housed individually in TN conditions (28.5 ± 0.7 °C) for 7 d. During this time, ADFI and ADG were monitored, blood samples were taken on d 1, 4, and 7, and piglets were video-recorded to assess behavior. Piglets were sacrificed on d 8 post-simulated transport and intestinal morphology was assessed. Data were analyzed using PROC MIXED in SAS 9.4. In the ELTS period, piglet TR was increased overall (P = 0.01) in ELHS (39.77 ± 0.05 °C) compared to ELTN (39.34 ± 0.05 °C) and ELCS (39.40 ± 0.05 °C) litters. During simulated transport, TC was greater (P = 0.02) in ELHS (40.84 ± 0.12 °C) compared to ELTN (40.49 ± 0.12 °C) and ELCS (40.39 ± 0.12 °C) pigs. Following simulated transport, BW loss was greater (P = 0.01; 40%) for ELHS compared to ELTN and ELCS pigs and ADFI was reduced (P = 0.05; 28.6%) in ELHS compared to ELTN pigs. Sitting behavior tended to be increased (P = 0.06; 47.4%) in ELHS vs. ELCS or ELTN pigs. Overall, circulating cortisol was greater for ELHS (P ≤ 0.01; 38.8%) compared to ELCS and ELTN pigs. Goblet cells per villi were reduced (P = 0.02; 20%) in the jejunum of ELHS vs. ELCS and ELTN pigs. In summary, ELHS reduced thermotolerance and increased the future stress response of piglets compared to ELCS and ELTN.