Milk Composition Measures as Indicators of Energy Balance in Crossbred Dairy Cows

This study had the objective of evaluating the potentials of using milk composition measures as indicator of energy balance (EB) in dairy cows. Milk composition traits (milk protein, fat and lactose percentage) from thirteen (13) primaparous and 47 multiparous (F1) Friesian x Bunaji cows were used for this study. The milk composition was analyzed weekly from 4 to 300days postpartum. The analyzed percentage milk fat, protein and lactose were used to calculate the milk composition measures. The average estimates of EB based on milk measures for all the 3 stages of lactation were positive, however, the magnitude of the average estimates of the EB increased with stages of lactation; the average estimates of EB were 21.99, 46.514 and 59.097MJ/d, respectively, for stages 1, 2 and 3 of lactation. The EB appeared to be less repeatable even within stages of lactation; 0.23, 0.26, 0.31 respectively for stages 1, 2, and 3. The magnitude and direction of the correlations between EB and milk composition traits varied across stages of lactation; the correlation coefficient was relatively stronger in the 3 rd stage than the 1 st and 2 nd stages of lactation. The potential indicators of EB are the protein contained variables, such as milk protein percentage (MPC), fat-protein ratio (FPR), change in milk protein yield (dmPy) and change in fat-protein ratio (dFPR). These variables had strong relationship with EB both within and across lactation stages. However, the correlation between EB and change in milk protein yield (dmPy) was consistently strong both within and across lactation stages. Base on the foregoing, it can be deduced that the most reliable indicator of energy balance in the medium yield Friesian x Bunaji dairy cows is the change in milk protein yield (dmPy), although other variables such as milk protein content (MPC), fatprotein ration (FPR) and change in fat to protein ratio (dFPR) could also be used as indicators of energy balance. However, dmPy seems to be the component common to all of these potential milk production variables.