The effects of body condition at calving, food intake and performance in early lactation on blood composition of dairy cows given complete diets

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Abstract
In each of two trials, three groups of eight cows, with condition scores of 1-5 to 2, 2-5 to 3 and 3-5 to 4 at calving, were given a complete diet for the first 16 weeks of lactation. Food intake, milk yield, live weight and condition score were measured, and related to levels of plasma glucose and free fatty acids, serum insulin, prolactin and progesterone in weekly blood samples, in an attempt to explain differences in food intake.In both trials, levels of plasma free fatty acids were high after calving for all cows and declined rapidly until week 8, after which they were fairly constant. Glucose and insulin levels increased after calving, producing curves similar to that for dry-matter intake in the first 8 weeks of lactation. Prolactin levels fluctuated too markedly to provide useful information. Progesterone levels increased until week 7 and then fluctuated at 3-week intervals coincident with oestrus. Dry-matter intake was negatively correlated with free fatty acid levels and positively correlated with insulin in trial 1, and with glucose and progesterone in both trials.