Evaluating the Health and Productivity of Weaned Piglets after Simulated Transport and Heat Stress When Antibiotics Are Eliminated from the Diet

The study objective was to evaluate the effects of post-weaning transport during heat stress (HS) on post-transport piglet health and productivity when dietary antibiotics were removed or replaced with a nutraceutical. Sixty mixed sex piglets from 10 sows (n=6 piglets/sow) were weaned (18.8±0.8d of age) and then herded up ramps into one of two simulated transport trailers in thermoneutral (TN; 28.8±0.2⁰C; n=30 piglets) or HS (cyclical 32 to 37⁰C; n=30 piglets) conditions for 12h. This procedure is referred to as simulated transport as in piglets are weaned from the sow, herded down an alley and up a ramp into a trailer, fans simulated air movement, and feed and water were withheld; however, trailer movement was not simulated, only the regrouping, isolation, and duration component. Following the 12h simulated transport, piglets were unloaded from the trailer, weighed, and then housed individually in TN conditions (28.5±0.1⁰C; 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 14d. Feed intake (FI), BW, and behaviors were monitored daily. On d15, all piglets were euthanized and intestinal samples were collected for histology. Data were analyzed using PROC MIXED in SAS 9.4 and pig was the experimental unit. Throughout the 14d 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 (P=0.08; 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 2d following simulated transport indicating greater illness behavior in NA pigs. 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. No temperature by diet treatment differences were observed with any comparison. In summary, withholding dietary antibiotics after weaning and transport can increase illness behaviors, reduce productivity, and negatively alter intestinal morphology compared to dietary antibiotic or L-glutamine provision.