The Effects of Cortisol and Norepinephrine on Weanling Piglets and the Selection of an Anxiolytic Probiotic

Elizabeth M Petrosus, Purdue University

Abstract

At weaning, piglets experience many changes including a switch from milk to solid food, a disturbance in the established hierarchy of the pen, mixing with unfamiliar piglets, and separation from the sow. While these shifts do not pose any immediate threat to the piglet, such changes may induce a negative affective state. Fear is the perception of an immediate danger (Barlow, 2002; Craske et al., 2009), while anxiety, in contrast, is defined as the perception of an upcoming negative event (Barlow, 2002; Craske et al., 2009). Thus, as there is no immediate threat to the piglets, it can be said that piglets experience anxiety-like states during weaning. While it is known that piglets experience anxiety-like states, there is a lack of data on how this negative affective state may cause changes to the piglet’s body. The objective of the first project was to administer cortisol or norepinephrine to piglets in order to induce anxiety. Then, identify changes to stress hormone concentrations, body temperature, the intestinal microbiome, translocation after challenge with Salmonella enterica serovar typhimurium, and behavior. Plasma cortisol concentrations had treatment by day interactions; on d 0.5 cortisol treated piglets had greater concentrations of cortisol than control and norepinephrine piglets, and on d 1 norepinephrine treated piglets had greater concentrations of cortisol than cortisol treated piglets. Plasma norepinephrine concentrations had treatment by day interactions; on d 0.5 norepinephrine concentrations were greater in norepinephrine treated piglets than cortisol piglets, on d 1 norepinephrine concentrations were greater in norepinephrine treated piglets than control piglets, and on d 2 norepinephrine concentrations were greater in norepinephrine treated piglets than cortisol piglets. For body temperature, cortisol treated piglets exhibited greater temperatures than norepinephrine or control piglets. Lactobacillus populations in rectal contents had treatment by day interactions; on d 0 cortisol treated piglets had greater concentrations of Lactobacilli than norepinephrine treated piglets, on d 7 and 14 norepinephrine treated piglets exhibited greater Lactobacilli concentrations than cortisol piglets, but on d 14 cortisol treated piglets also exhibited less Lactobacilli than control piglets. In cecal contents, cortisol and norepinephrine treated piglets exhibited greater Escherichia coli populations. In ileal tissue, E. coli populations tended to have a treatment by day interaction; on d 0.5 cortisol piglets had greater concentrations of E. coli than norepinephrine piglets. For populations of aerobes in jejunal content, there was a treatment by day interaction; on d 14 cortisol and control piglets exhibited greater concentrations of aerobes than norepinephrine treated piglets. In ileal content, there tended to be greater concentrations of anaerobes in norepinephrine treated piglets than cortisol treated piglets. In ileal tissues, coliforms tended to have a treatment by day interaction; on d 2 control piglets had less coliforms than the cortisol and norepinephrine piglets. For Salmonella typhimurium populations in rectal contents after challenge, there were greater concentrations in control piglets than norepinephrine treated piglets. For lying or sitting, there tended to be a treatment by hour interaction; the percent of cortisol piglets lying or sitting were less than the norepinephrine piglets and tended to be less than the control piglets for 20, 40, and 60 minutes post-treatment. For standing, there tended to be a treatment by hour interaction; the percent of cortisol piglets standing were greater than the norepinephrine piglets and tended to be greater than the control piglets for 20, 40, and 60 minutes post-treatment. For eating, there was a treatment by day interaction; the percent of cortisol piglets eating were greater than the control and norepinephrine piglets for 20, 40, and 60 minutes post-treatment, and the percent of norepinephrine piglets eater were less than the cortisol and control piglets for 0.66, 334, and 335 hours post-treatment. For huddling there was a treatment by day interaction; the percent of cortisol piglets huddling were less than the percent of norepinephrine piglets and tended to be less than the control piglets for 20, 40, and 60 minutes post-treatment. The results suggested that anxiety-like states in piglets may be associated with changes to body temperature, the microbiome, infection, and behavior. A possible way to reduce anxiety-like behavior in piglets may be to orally administer a probiotic supplement. These supplements are believed to act on the gut-brain axis and affect anxiety-like behavior. However, no research has yet attempted to isolate microorganisms from weanling piglets and tested for anxiolytic properties. The objective of the second project was to isolate anxiolytic probiotics from the intestines of weanling piglets with the intent of optimizing the probiotic mixture for oral administration in a future behavioral study. Isolates have been submitted to the NRRL (Peoria, IL), and a patent application has been submitted and is under review. Altogether, the two projects help to piece together the story of anxiety in weaning piglets. The first shows how anxiety physically causes changes in piglets while the second offers a potential treatment for anxiety by selecting a mixture of anxiolytic probiotics.

Degree

M.S.

Advisors

Patterson, Purdue University.

Subject Area

Agriculture|Animal sciences

COinS