EFFECT OF NUTRITIONAL STATUS ON PLASMA CONCENTRATIONS OF INSULINLIKE GROWTH FACTOR BINDING PROTEIN-3 AND INSULIN-LIKE GROWTH FACTOR-I IN PASTURE-FED HOLSTEIN-FRIESIAN COWS

摘要

Insulin-like growth factor binding protein-3 (IGFBP-3) is the predominant IGFBP in biological fluids including blood and milk (Baumrucker and Erondu 2000). The IGFBP-3 is bound to the insulin-like growth factors (IGFs) in most body fluids, and modulates their biological activity by controlling their availability to target tissues (Rechler and Clemmons 1998). Nutritional status plays a major role in regulating circulating levels of IGF-I and its respective binding proteins and cell membrane receptors(Thissen et al. 1994). There is limited information on the effects of level of nutrition on the concentrations of IGFBP-3 in plasma or milk, especially in pasture-based dairy herds. In this study, the effects of dry matter (DM) intake and metabolisable energy (ME) density on the concentrations of IGFBP-3 and IGF-I in the plasma samples of individual cows belonging to 2 dietary groups were evaluated. The association between the concentrations of IGFBP-3 and IGF-I in the plasma samples from these cows was also investigated.