|Lamberson, W - UNIVERSITY OF MISSOURI|
|Safranski, T - UNIVERSITY OF MISSOURI|
|Bates, R - UNIVERSITY OF MISSOURI|
|Keisler, D - UNIVERSITY OF MISSOURI|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 1995
Publication Date: N/A
Interpretive Summary: Somatotropin (ST), also known as growth hormone, is produced by the pituitary gland and is needed for body growth. ST stimulates the production of another hormone, insulin-like growth factor-I (IGF-I), which is produced by the liver and is a potent stimulator of growth and development. This study was conducted to evaluate the relationship between nIGF-I secretion and production traits in swine. Serum levels of IGF-I wer evaluated in 100 pigs from 6 to 21 weeks of age. The endpoints measured were heritability, growth, body fat content, meat quality, age at puberty, and litter size. A fairly high heritability was found for IGF-I secretion, indicating that this endocrine function can be enhanced by genetic selection. Growth was the only endpoint found to be related to serum IGF-I levels. IGF-I secretion was positively related to growth, particularly at the younger ages. Given the known influence of a variety of factors (age, breed, nutrition, environmental temperature, etc) on IGF-I secretion, the achievement of more efficient growth by genetic selection for the secretion of this hormone will likely need to be conducted under experimentally controlled conditions.
Technical Abstract: IGF-I is a peptide hormone which has been shown to be involved in metabolic regulation of growth and reproduction in livestock species. The objectives of this study were to quantify concentrations of IGF-I in growing pigs and determine if IGF-I concentration can be used as a predictor of growth, composition and reproductive traits. Forty intact male and 60 female pigs, ,divided equally between two locations, were weighed and bled at 3 wk intervals from 6 to 21 wk of age. Serum was separated and IGF-I concentration determined via RIA. Backfat and loin eye area were measured with the use of B-mode ultrasound and adjusted to 100 kg. Age at puberty and first parity litter size were measured on gilts. Performance traits were fitted to a model including the effects of IGF-I concentration, sex, location and interactions. IGF-I concentrations increased (P < .05) from 3 to 18 wk of age before dropping at 21 wk of age. Concentrations increased more rapidly in males than females and differed significantly between sexe from 12 to 21 wk of age. Repeatability of IGF-I concentration was .29; IGF-I concentrations of samples collected at six wk were not correlated with those at later ages. Correlations between IGF-I concentrations of samples at later ages ranged from .27 to .51. Heritability of IGF-I concentration was .27. There was a tendency for weight to be affected by a sex x age interaction (P = .09). Weight of boars exceeded weight of gilts only at 21 wk (111.4 +/- 1.1 vs 107.1 +/- .8 kg). Regressions of weight on IGF-I concentrations were positive at all ages, but greatest at 6 wk. IGF-I concentration did not significantly affect backfat thickness, loin eye area, percentage lean, age at puberty or litter size.