| Autor: |
Holland, M. D., Hossner, K. L., Tatum, J. D., King, M. E., Mauck, H. S., Odde, K. G. |
| Zdroj: |
Journal of Animal Science; December 1988, Vol. 66 Issue: 12 p3190-3196, 7p |
| Abstrakt: |
Serum samples and BW were obtained from 2-yr-old beef heifers, pregnant with either single (SF, n = 12) or twin (TF, n = 7) fetuses, at 7-d intervals from d 190 of gestation until calving. Serum insulin-like growth factor I (IGF-I) concentrations of SF heifers gradually declined from d 190 (69.9 ± 1.0 ng/ml) to d 263 (55.6 ± .8 ng/ml), then exhibited a slight increase by d 277 (63.4 ± 1.1 ng/ml). Serum IGF-I concentrations of TF heifers essentially paralleled, yet were lower (P< .05) than, concentrations in SF heifers for all days tested except d 197 and 205. The SF heifers pregnant with heifer fetuses (n = 6) had higher IGF-I concentrations (P< .1) than heifers pregnant with bull fetuses (n = 6) for all days tested except d 214 and 235. Instantaneous absolute growth rate (IGR) of SF heifers declined from 1.485 kg/d at d 190 to .257 kg/d by d 277. Rate of decline in IGR of TF heifers was much greater (P< .0001). Correlations between serum IGF-I concentrations and IGR for SF and TF heifers were .79 (P< .001) and .59 (P< .05), respectively. These data suggest that number and sex of fetus influence maternal concentrations of IGF-I and that the combined growth rate of the dam and conceptus during gestation is related to serum IGF-I concentration. |
| Databáze: |
Supplemental Index |
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