Abstract
The relationship between the concentration of serum insulin-like growth factor-I (IGF-I) and changes in body weight was studied in a total of 169 Holstein cows from 30 days before to 40 days after parturition. The concentration of serum IGF-I decreased after parturition and then increased again gradually. Lactating cows with low concentrations of serum IGF-I had decreased body weights and daily milk productions during a month. However, these cows had normal ranges of total protein, GOT, GPT, triglyceride, total cholesterol, non esterif ied fatty acids, BUN, and ketone bodies. These results suggested that the concentration of serum IGF-I in lactating cows might be related to changes in body weight and daily milk production. Serum concentrations of IGF-I might be useful and sensitive parameter for evaluating the condition of the liver and milk-production performance.
