Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/1999
Publication Date: N/A
Citation: N/A Interpretive Summary: Somatic growth, in large part, depends on a functional pituitary gland - target tissue axis controlled by growth hormone secretion. With the availability of recombinantly derived growth hormone, producers have the possibility of controlling and manipulating the deposition of fat and lean tissues by growing pigs. Both for animal management and cost of treatment application, the younger the pig when treated, the better. Results of thi study suggest that young pigs are unresponsive to somatotropin treatment prior to 33 - 43 days of age. This conclusion is based on growth response and an indicator of amino acid metabolism. The mechanism for this early life refractory state appears to be dependent on matuartion of the insulinlike growth factor system and not a consequence of nutritional status.
Technical Abstract: Administration of somatotropin (ST) to prenatal and early postnatal pigs does not affect protein and lipid metabolism to the magnitude observed in older pigs. Maturation of the somatotropin-insulinlike growth factor (IGF) may be developmentally regulated or be limited by nutrient intake. Naturally-reared or artificially-reared pigs, which exceeded nutrient requirements by 30%, were treated with buffer or 120 ug porcine somatotropin per kg body weight starting at 10, 19, 33, 43, 63, 83 and 125 days of age for a 4 day period. Blood samples were assayed for functional indices of the ST/IGF axis. Circulating IGF 1 changed little with age while IGF 2 increased with age. Treatment with STincreased IGF 1, but had no affect on circulating IGF 2. Circulating IGF binding protein 3 increased and IGF binding protein 2 decreased with ST treatment.. ST treatment resulted in a decrease of plasma urea nitrogen at all ages. Developmental changes of IGF 1 and IGF binding proteins 3 and 2 coincide with changes in amino acid metabolism.