|Lamberson, W - UNIVERSITY OF MISSOURI|
|Sterle, J - UNIVERSITY OF MISSOURI|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 5, 1996
Publication Date: N/A
Interpretive Summary: Insulin-like growth factors (IGFs) are peptide hormones which are involved in the regulation of growth and reproductive processes. There are two IGFs, referred to as IGF-1 and IGF-2. Relative to IGF-1, there is relatively little known about the biology of IGF-2, which is secreted at high levels in the pig. Accordingly, the present study evaluated the relationships of IGF-2 secretion to growth and reproductive traits in pigs Forty male and 60 female pigs were utilized. Random sampling from 52 offspring of these animals also was performed. No sex-related differences in IGF-2 secretion were observed. The secretion of IGF-2 was found to have low heritability. Serum levels of IGF-2 were related to growth from weaning to 12 wk of age, however the sum of serum IGF-2 and IGF-1 concentrations had a much stronger relationship to growth. Serum IGF-2 levels were not related to backfat thickness, loin eye area, percentage lean, time required to reach market weight, age of puberty, or litter size The sum of IGF-1 and IGF-2 concentrations was associated with faster growth and a decrease in time required to reach market weight. The results of this study indicate that IGF-2 may be involved in growth regulation, but the summation of IGF-2 and IGF-1 concentrations may provide a more valuable endpoint for predicting growth and for gaining an understanding of growth control which will be necessary for achieving improved performance in swine.
Technical Abstract: Insulin-like growth factors-I and II (IGF-I and II) are peptide hormones which are involved in metabolic regulation of growth. The objective of this study was to determine if IGF-II concentration was predictive of growth, compositional, and reproductive traits of pigs. Forty male and 60 female pigs, divided equally between two locations, were weighed at 3-wk intervals from birth to 22 wk and bled at 9 and 21 wk of age. Serum IGF-I IGF-II, and growth hormone (GH) concentrations were determined via RIA. Blood was collected from a random sample of 52 progeny from 13 litters at 9 wk of age and serum was assayed for IGF-II. IGF-II concentrations were greater at 9 than 21 wk of age (226.7 vs 159.3 ng/mL, respectively; P < .001), but did not differ between sexes. The correlation between IGF-II concentrations assayed from samples collected at 9 and 21 wk was .08. The partial correlations between IGF-I and IGF-II concentrations were .33 and .14 at 9 and 21 wk, respectively. The heritability of IGF-II concentratio estimated from offspring-midparent regression was .08 +/- .20. Increasing 9 wk IGF-II concentration was significantly associated with increases in weight from weaning to 12 wk. However, the sum of 9 wk IGF-I and IGF-II concentrations had a greater relationship to weight and gain in the growing phase than the concentration of either hormone alone. IGF-II concentration at 9 or 21 wk alone did not significantly affect backfat thickness, loin eye area, percentage lean, days to 100 kg, weight at 21 wk, age at puberty, or litter size but was associated with increased backfat and decreased days to 100 kg when summed with IGF-I concentration.