Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/1998
Publication Date: N/A
Interpretive Summary: Early growth is an important determinant of gain and efficiency in growing pigs. A major limiting factor of piglet growth is feed intake, particularly in the period immediately following weaning. Very little is known about potential regulators of feed intake in the young pig, but recently a new family of hormones (called "orexins") was discovered in the brain of the rat which would increase feed intake in that animal. The purpose of this study was to develop porcine orexin and evaluate the effects of this new hormone on feed intake in young pigs. This study provided promising data which demonstrated (for the first time in any species) that a single intramuscular injection of orexin would increase feed intake. These findings provide an important base from which future efforts may be directed in an ongoing effort to improve pig performance. The results from this study would be of interest to agricultural scientists sin academia and industry who are interested in regulation of feed intake and the interactions that occur between nutrition and growth.
Technical Abstract: Early growth is an important determinant of gain and efficiency in growing pigs. A major limiting factor of piglet growth is feed intake. Orexins, newly discovered neuropeptides, may be important regulators of appetite. The orexin gene, which encodes orexin-A and -B, was recently identified in rodents and man. The objectives of this study were to clone the cDNA for porcine orexin, utilize the cDNA sequence information to produce synthetic hormone, and evaluate the effect of orexin administration on feed intake in weanling pigs. Oligonucleotide primers were designed for RT-PCR production of porcine orexin cDNA. The PCR products were cloned, sequenced, and found to be 88.5 % homologous to the human orexin sequence. Predicted translation of porcine orexin cDNA revealed orexin-A and -B amino acid sequences that were 100% and 96% homologous to the known human peptides, respectively. Porcine orexin-B was synthesized according to the predicted sequence. Twenty-six crossbred piglets were utilized in three replicates (n=8-10/replicate). Piglets were weaned between 2-3 wk of age. One wk after weaning, equal numbers of animals in each replicate received intramuscular injections of orexin-B (3 mg /kg body weight) or vehicle (sterile water). Feed intake was monitored from -24 to 24 hr relative to injection (time 0). The orexin-injected pigs ingested an additional meal at 12 h when compared with the control animals (P = .02). Cumulative feed intake was increased by orexin-B administration from 12 to 24 hr post-injection (P < .05). Total feed intake at 24 hr was improved by 18% in orexin-treated pigs (P = .05). The ability to stimulate appetite during critical periods of early growth, particularly following weaning, could result in significant improvements in swine production efficiency.