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 125 Ι 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).
Highlights
There have been several studies concerning Insulin-like growth factors (IGF-I and IGF-II) in bovine milk during the lactation period (Campbell et al, 1989; Collier et al, 1991)
Francis et al (1988) reported that insulin-like growth factors were present in bovine prepartum mammary secretions, and both colostrum and milk
Animals Individual milk samples from 70 Holstein dairy cows, which had been managed in two dairy herds in northern Kyoung-ki Province, were assayed for naturally occurring IGF-I contents for one year, between September 2000 and August 2001
Summary
There have been several studies concerning Insulin-like growth factors (IGF-I and IGF-II) in bovine milk during the lactation period (Campbell et al, 1989; Collier et al, 1991). Francis et al (1988) reported that insulin-like growth factors were present in bovine prepartum mammary secretions, and both colostrum and milk. There have been several studies concerning Insulin-like growth factors (IGF-I and IGF-II) in bovine milk during the lactation period (Campbell et al, 1989; Collier et al, 1991).
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