Correlation between growth curve parameters and plasma metabolites in replacement dairy heifers.

This paper considers the relationships among growth curve parameters and plasma metabolites in dairy heifers. Sixty Italian Friesian heifers were randomly assigned on two experimental feeding groups to obtain a moderate (0.70 kg/d; M) or a high (0.90 kg/d; H) average daily gain from 5 to 15 mo of age. Every 28 d, heifers were weighed, scored for BCS, and measured for: wither height, hip height, body length, and heart girth. Blood samples were collected at 9 and 15 month of age, then at 14 and 7 days before calving, to be analyzed for plasma metabolites and enzymes. Laird’s growth function was estimated for body size measurements, and Pearson’s correlation coefficients were calculated between b1 (which reflects the initial specific growth rate), b2 (which reflects the maturation rate of the animal), and plasma metabolite concentrations during growth and before first calving. Among the explored blood metabolites and enzymatic activities at 9 and 15 mo of age, those with high correlation with growth curve parameters were glucose, urea, and ceruloplasmin. Both at 9 and 15 mo of age plasma cholesterol and ceruloplasmin concentrations were positively correlated with their respective values before calving (P<0.001). Plasma glucose at 15 mo was negatively correlated with plasma albumin before calving (P<0.001). The curve parameters from skeletal height measurement were correlated with prepartum plasma creatinine concentration, suggesting that this item was affected by the development of skeletal muscles. Before calving, plasma NEFA and BHBA were positively correlated with enzymatic activities and positive acute phase proteins, mainly related to liver function.