Effects of Syndyphalin-33 on appetite, endocrine, and immune parameters in the recently weaned pig

This thesis discusses the background information regarding the physiological effects the pig encounters during weaning as well as a potential factor that can be used to assist the pig during this time. Specifically, the research focus is to assess the ability of the tri-peptide opioid agonist, Syndyphalin-33 (SD-33), to increase feed intake and body weight and modulate immune responses during the post-weaning period. The results of this research have demonstrated that SD-33 increases feed intake, transiently increases growth hormone and cortisol levels, and increases total white blood cell counts while selectively increasing monocyte numbers in healthy weaned pigs. This research also demonstrates that, although co-treatment with SD-33 during an immune challenge of Salmonella enterica did not result in increased feed intake, SD-33 exerted effects relating to increasing the circulating populations of immune cells at 48 h postinjections, selectively increasing monocyte numbers. Based on these results, SD-33 may have the potential to be used as an agent to decrease the negative effects of stress during weaning in pigs. However, further investigation is needed to better understand the timing of effect, and to rule out any immunosuppressive effects, which would be detrimental to the animal’s well-being.