With a growing number of feeder and weaner pigs making the long trek from North Carolina to Midwest hog farms, a researcher at the U.S. Department of Agriculture's Agricultural Research Service stationed at Purdue University wanted to know the impact those long hauls had on pig health.
Using a research grant from the National Pork Board, investigator Susan Eicher designed a study to determine if rest (mid-journey lairage) would improve pig health.
Four replications were conducted, one during each season of the year in January, April, August and October. Fifty-lb. pigs were housed in 16 pens (13 to 16 pigs/pen) with eight pens/treatment, says Eicher.
Two groups with lairage or rested pigs were transported for eight hours, given a rest with food and water for eight hours, then transported eight hours.
Two groups were continuously transported for 16 hours (without rest). Groups were not mixed prior to or after transport from the Purdue Swine Research Farm.
Truck temperatures varied with the seasons. Body weight loss was not different between treatment groups. Behavior was evaluated by scan sampling of the pens prior to and after transport.
The groups of continuously transported pigs drank more water and walked more following transport.
The lairage groups showed avoidance to eat and drink that varied by season of the year.
After the tests, pigs were off-loaded into grower barns at the Purdue facility. Blood samples were obtained from eight pigs in each treatment group and those pigs were humanely euthanized to obtain tissue samples.
Rest stops did make a difference in the health of the groups, according to Eicher. “We saw with the continuously transported pigs things you would expect to see — stress and immune measures reflecting the transport stress (increased white blood cell counts),” she says.
In continuously transported pigs, total white blood cell count was higher on Day 1 following transport than lairage pigs. Levels of monocytes (large white blood cells) also rose, becoming “antigen-presenting cells,” which is a sign that stress has caused a change in immune functions.
Blood samples were taken at Day 7 following transport, which showed continuing changes in immune responses of continuously transported pigs.
Additionally, the microbial population measures also indicated differences in intestinal microbial populations between the two treatments, indicating that the degree of stress may be affecting this variable, explains Eicher.
Tests of bacteria in pigs' intestines also revealed a shift and decrease in intestine microbial populations from Day 1 up to Day 14 following transport in the non-rested pig groups, indicating pig health could be compromised. “We didn't see big differences in the presence of salmonella organisms, but fewer bacterial populations have the possibility to lead to compromised gut health,” she says.
Further, she adds: “Alterations in microbial populations could alter the ability of the pig to use the nutrients that it eats. This study indicates that extended transport without lairage alters few behaviors, but changes the microbial populations of the jejunum and cecum (intestine) and the microbial populations of jejunum, ileum and cecum tissues, and alters innate immune functions that may cause greater susceptibility to pathogens.
“Overall, in this setting of a controlled lairage environment without mixing the pigs, lairage lessened changes after transport,” Eicher concludes.
The researcher is currently conducting similar transportation trials using weaned pigs, and also testing the value of yeast products in helping pigs cope with weaning and transport stress.
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