The biometry of lactation

SUMMARY A consideration of input-output relationships relating energy intake to its probable utilization for growth, condition and lactation by dairy cows leads to a series of equations describing observable responses. Energy is expressed in terms of units of milk equivalent, common to all equations, and the lactation curve, y n = an ò e −cn is shown to be capable of biological interpretation, having regard to the subordinate equations from which it is derived. This expression relates milk production y n during a time interval n through the parameters a, b and c . The validity of the steps by which the function is developed is examined by reference to published work.