|Kojima, C -|
|Jenkins, S -|
|Cooper, T -|
|Roberts, M -|
|Kattesh, H -|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 12, 2009
Publication Date: July 15, 2009
Citation: Kojima, C.J., Jenkins, S.J., Cooper, T.A., Roberts, M.P., Carroll, J.A., Kattesh, H.G. 2009. Effects of syndyphalin-33 on feed intake and circulating measures of growth hormone, cortisol, and immune cell populations in the recently weaned pig. Journal of Animal Science. 87:3218-3225. Interpretive Summary: The recently-weaned pig often exhibits decreased feed intake, increased susceptibility to disease, and poor growth. These responses to the stress of weaning often manifest as a growth lag, but can be manifested as more severe morbidity and even mortality, particularly in conditions of suboptimal herd health or management. Through its actions on appetite, syndyphalin-33 may offer some protection during the weaning process, increasing overall health and well-being during this critical period. Syndyphalin-33 is a synthetic enkephalin with prolonged pain reliever activity. In pigs, rats, and sheep, administration of syndyphalin-33 via oral routes, subcutaneous or intravenous, resulted in transient increases in circulating concentrations of growth hormone. Therefore, we conducted two experiments to investigate the potential for syndyphalin-33 to eliminate the post-weaning growth decline in recently weaned pigs. A preliminary experiment focused on the effects of syndyphalin-33 on feed intake and growth, while the second experiment investigated acute effects of syndyphalin-33 on the growth, stress, and immune axes. Results indicated that while treatment with syndyphalin-33 increased feed intake in the first experiment, there was no increase in body weight in either of the experiments. However, treatment with syndyphalin-33 did increase growth hormone concentrations and increased monocyte numbers, thus suggesting an effect on the immune system. Collectively, these data indicated that syndyphalin-33 has potential to be used as an agent to increase feed intake and decrease the negative effects of stress during weaning in pigs, but 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. This research will be of interest to scientists in academia, industry, and government agencies working primarily in the field of appetite regulation in domestic animals.
Technical Abstract: The synthetic met-enkephalin syndyphalin-33 (SD-33) increases feed intake in sheep and transiently increases circulating growth hormone (GH) concentrations in sheep, rats, and pigs. Two experiments were performed to evaluate the effects of SD-33 on recently-weaned pigs. In a preliminary experiment, pigs were administered either SD-33 (0.5 umole/kg, given intramuscularly) or saline immediately prior to a 3 h transport and subsequent placement into group pens. Treatment with SD-33 increased (P = 0.01) daily feed intake; cumulatively, pen intake over 7 d post-weaning tended (P < 0.06) to be greater than in control pens. In the second experiment, pigs were weaned and fitted with jugular catheters. The following day, pigs were treated with either SD-33 or saline as described above. Transient increases (P < 0.05) in circulating concentrations of GH (at 1 and 1.5 h post-injection) and cortisol (at 3.5 and 4 h post-injection) were observed in pigs treated with SD-33 relative to controls. No difference in feed intake was observed between treatments over 4 d post-injection. Increased (P < 0.05) numbers of circulating neutrophils, lymphocytes, and monocytes were observed in both treatment groups over 4 d post-injection, and treatment with SD-33 tended (P < 0.07) to selectively increase monocyte numbers. Although SD-33 has potential to be used to increase feed intake and decrease the negative effects of stress during weaning in pigs, further investigation is needed to better understand the timing of effect and to rule out possible immunosuppressive effects.