Insulin, IGF-I, and lactoferrin concentrations and yields and their associations with other components within colostrum, transition, and whole milk of primiparous and multiparous Holstein cattle.

The primary objective of the study was to characterize concentrations and yields of lactoferrin (LF), insulin, and IGF-I in colostrum, transition milk (TM), and whole milk (WM) of multiparous (MP) and primiparous (PP) cows. A secondary objective was to determine associations between colostrum and TM components (fat, protein, lactose), IgG, and bioactive compounds (oligosaccharides, LF, insulin, IGF-I; defined as compounds present in micro quantities that stimulate physiological responses systemically or locally within the neonate). Holstein cows (10 MP and 10 PP) were assigned to the study at calving and colostrum was collected 5.3 ± 0.7 h (mean ± SE) after calving, followed by twice daily sampling of milkings 2-5 (TM) and milking 12 (WM). Colostrum, TM, and WM samples were analyzed by commercial ELISA to determine concentrations of LF, insulin, and IGF-I. Concentrations of insulin, IGF-I, and LF were greatest in colostrum compared with all other milkings. Similarly, IGF-I and LF yields were greatest in colostrum, whereas insulin yield was greatest in colostrum and milking 2 compared with milking 4, 5, and 12. Primiparous cows had greater insulin and lower LF concentrations in colostrum compared with MP cows. Additionally, lower LF concentrations in PP cows persisted through milkings 2 and 3. The majority of associations between components and bioactive compounds in colostrum were positive; however, correlations were different between PP and MP cows. Specifically, there were a greater number of strong (ρ > 0.80) correlations between components and IgG in PP cows. In contrast, MP cows demonstrated a greater number of strong correlations among bioactive compounds. To the authors' knowledge, this study is the first to characterize the yields of IGF-I, LF, and insulin during the colostral (collection within 6 h) and TM period in both MP and PP cows. The study findings indicate that parity influences the levels of LF and insulin, but not IGF-I. Our study also uniquely demonstrates associations between early lactation components and bioactive compounds, which are not consistent among parities.