Dry matter intake from parturition to midlactation.

Six years of data from the Purina Research Center were summarized to quantitate relationships among DMI, DIM, BW, and 4% FCM. Cows were fed individually and housed in a tie-stall barn from parturition to 21 wk postpartum. Best overall equation predicting DMI was kg DMI = .008037 x kg BW + .3134 x kg 4% FCM + .2286 x DIM - .002176 x (DIM)2 + .00000705 x (DIM)3, R2 = .64, CV percentage = 11.1. Data were best fit when separate equations were developed for each week postpartum up to 6 wk and then for periods including 6 to 8, 9 to 13, and 14 to 20 wk. The commonly used equation, kg DMI = .02 x kg BW + .33 x kg 4% FCM, overestimated DMI until wk 10 but underestimated DMI thereafter. The NRC multifactor DMI estimates could be lower or higher than equations developed up to wk 8, depending on values chosen within range of several factors. At wk 8 and beyond, NRC estimates were lower than equations developed, even when highest level within range of several factors was chosen. Calculated energy balances resulted in greater and extended energy deficit for cows in their second or later lactation compared with first lactation. Loss of BW alone was a poor indicator of energy status in early lactation.