|Lay Jr, Donald|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2016
Publication Date: 2/2/2017
Citation: Johnson, J.S., Lay Jr., D.C. 2017. 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. Journal of Animal Science. 95:91-102. doi:10.2527/jas.2016.1070.
Interpretive Summary: Stress is a multi-factorial problem that can negatively affect pig performance and is closely linked with welfare. Although stress is not necessarily harmful when animals are able to cope, there is a potential for distress when animals are exposed to multiple stressors. In modern swine production systems, pigs are frequently exposed to multiple stressors (e.g., mixing, weaning, transportation, handling, isolation, thermal stress) that have the potential to increase disease incidence and in severe cases morbidity and mortality. In particular, weaning, transport stress, and thermal stress have the potential to increase disease incidence, especially when they occur concomitantly. To combat the negative effects of weaning and transport stress on piglet health and well-being, current management practices call for the use of dietary antibiotics for newly weaned and transported piglets to reduce pathogen load and promote growth. However, due to the possible contribution of in-feed antibiotics to the development of antibiotic resistant strains of bacteria, their use may be limited in the future thereby contributing to reduced piglet welfare and productivity. Therefore, study objectives were to evaluate the impact of post-weaning simulated transport during heat stress and thermoneutral conditions when dietary antibiotics were either eliminated from the diet or replaced with 0.20% L-glutamine. We determined that withholding dietary antibiotics after weaning and simulated transport had a negative effect on piglet welfare; however, temperature during transport did not significantly impact post-transport welfare. Specifically, withholding dietary antibiotics increased intestinal damage, reduced feed intake and growth, and increased behaviors associated with illness in pigs compared to piglets provided either dietary antibiotics or L-glutamine. These data provide further evidence that eliminating dietary antibiotics after weaning and transport will negatively impact the welfare and health of piglets, and may also indicate that the inclusion of L-glutamine could be a viable alternative to dietary antibiotics in swine production.
Technical Abstract: 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 (n = 6 piglets/sow) were weaned (18.8 ± 0.8 d of age) and then herded up ramps into one of two simulated transport trailers in either TN (28.8 ± 0.2°C) or HS (cyclical 31 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 (TR) 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% RH) and assigned to one of three dietary treatments balanced by weaning weight, sex, sow, and transport environment. Treatments were dietary antibiotics [A; n = 20 piglets; 5.5 ± 0.2 kg BW; chlortetracycline (400 g/ton) + tiamulin (35 g/ton)], no dietary antibiotics (NA; n = 20 piglets; 5.6 ± 0.2 kg BW), or 0.20% L-glutamine (GLU; n = 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 TR and post-transport BW loss were greater (P < 0.01) 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 (P < 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 (P < 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 (P = 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 (P < 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 welfare and productivity compared to dietary antibiotic administration and L-glutamine provision.