Changes in the Levels of Insulin-like Growth Factors (IGF-I and IGF-II) in Bovine Milk According to the Lactation Period and Parity |
S. H. Kang, J. U. Kim, Y. Kim, K. S. Han, W. J. Lee, J. Y. Imm, S. Oh, D. J. Park, Y. I. Moon, S. H. Kim* |
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Correspondence:
S. H. Kim, |
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Abstract |
The objectives of this study were to characterize the changes occurring in the levels of insulin-like growth factors (IGF-I and IGF-II) in bovine milk during a one-year lactation period, and to determine the parameters affecting IGF content in bovine milk. Milk was collected individually from lactating Holstein cows (n = 70), and IGF-I and -II levels were determined via radioimmunoassay, using 125I after acid-ethanol treatment. The proximate compositions of the milk samples were determined using a near-infrared milk analyzer. The data were analyzed by the GLM and CORR procedures using SAS software to determine significant differences (p<0.05) occurring within groups (dairy farms, lactation periods, season, and parity). We noted an approximately six-fold reduction in the IGF-I concentration (from 2,462.7 to 353.0 ng/ml) and a three-fold drop in the IGF-II concentration (from 929.1 to 365.7 ng/ml) in the bovine colostrum, between 6 h after parturition and 18 h after parturition. IGF-I and -II content, measured at the early, middle, and late stages of lactation did not change significantly throughout the entirety of the lactation period. Interestingly, parity did not significantly affect IGF-I content, but did significantly affect IGF-II content between the primiparous and multiparous cows. We also found there were no significant relationships between IGF-I and total protein content or somatic cell counts (p<0.05). |
Keywords:
Insulin Growth Factor-I And -II; Radioimmunoassay; Lactation Period; Parity; Somatic Cell |
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