Location: Livestock Behavior ResearchTitle: Serotonin’s role in piglet mortality and thriftiness Author
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2014
Publication Date: 10/1/2014
Publication URL: http://handle.nal.usda.gov/10113/59755
Citation: Dennis, R.L., McMunn, K.A., Cheng, H., Marchant Forde, J.N., Lay Jr, D.C. 2014. Serotonin’s role in piglet mortality and thriftiness. Journal of Animal Science. 92:4888-4896.
Interpretive Summary: High piglet mortality continues to cause a welfare problem and economic loss to the swine industry. Losses due to liveborn neonatal preweaning mortalities account for 9% to 18% of the litter mostly due to a combination of starvation and crushing. However, the causes of preweaning mortality are multifactorial and interrelated, including elements of the farrowing environment, biology of the sow and biology of her litter. A vital hormone and neurotransmitter, serotonin, is known to regulate energy and glucose balance, which is critical for neonatal survival. During embryonic development, serotonin is also known to assist in the maturation of vital biological systems including the neural and digestive systems. Insufficient serotonin during pre- and early post-natal development could result in under-development of these systems, resulting in a higher chance of early mortality. In the present study we determined that umbilical levels of serotonin were lower in piglets that die within 48 hours of birth compared with those that survive. We also found that umbilical levels of serotonin correlate positively to normal neonatal behaviors such as time spent sleeping and spending time under the heat lamp. Our data show that umbilical serotonin concentrations play a crucial role in piglet development and survivability. These results suggest a potential means of intervention for improving piglet survival and well-being.
Technical Abstract: Improving piglet survivability rates is of high priority for swine production as well as for piglet well-being. Dysfunction in the serotonin system has been associated with growth deficiencies, infant mortalities or failure to thrive in human infants. The aim of this research was to determine if a relationship exists between infant mortality and failure to thrive (or unthriftiness), and umbilical serotonin (5-HT) concentration in piglets. Umbilical blood was collected from a total of 60 piglets from 15 litters for analysis of 5-HT and tryptophan (the amino acid precursor to 5-HT) concentrations. Behavior was scan sampled for the first 2 days after birth. Brain samples were also taken at 8 h after birth from healthy and unthrifty piglets (n = 4/group). The raphe nucleus was dissected out and analyzed for 5-HT and dopamine (DA) concentrations, as well as their major metabolites 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), respectively. Data were analyzed by analysis of variance using SAS 9.2 software. Piglets that died within 48 h of birth (n = 14) had significantly lower umbilical blood 5-HT concentrations at the time of their birth compared to their healthy counterparts (n = 46; P = 0.003). However, no difference in tryptophan was detected (P = 0.38). Time spent under the heat lamp and sleeping were positively correlated with umbilical 5-HT levels (P = 0.004 and 0.02, respectively), while inactivity had a negative correlation with 5-HT levels (P = 0.04). In the raphe nucleus, the center for brain 5-HT biosynthesis, unthrifty piglets had a higher concentration of 5-HIAA (P = 0.02), and a trend for higher concentrations of 5-HT (P = 0.07), compared with healthy piglets. DA levels did not differ between thrifty and unthrifty (P = 0.45); however, its metabolite HVA was greater in unthrifty pigs (P = 0.05). Our results show evidence of serotonergic dysfunction, at both the central and peripheral levels, accompanying early piglet mortalities. These data suggest a possible route for intervention, via the serotonin system, to improve piglet survivability. However, further research is required to validate this hypothesis.