Variable Grain Intake During Two Portions of the Lactation

Abstract

In two trials a total of 96 cows was divided at parturition into four groups based on grain feeding. During day 0 to 45 (period 1) grain was fed ad libitum (H) or at 1kg per 4kg milk (L), and during period 2, day 46 to 180 (trial 1) or 270 (trial 2), the high grain:milk ratio was 1:2.5 (H) and the low 1:4 (L). This gave a continuous high rate (HH), continuous low rate (LL), and two crossover groups (LH and HL). Corn silage intake was limited, but hay was allowed ad libitum. During trial 1 the greatest amount of milk, fat-corrected milk, fat, and solids-not-fat was for group LH. These values for group LL were below those of the other three. During trial 2 no differences in production were significant between the four groups during period 1, period 2, or 1 plus 2. Body weight loss during period 1 was least for H, and over the entire experiment body weight gains were more for H cows. Cows in H in period 1 produced 2.0kg more milk, consumed 5.0kg more grain, and 2.6kg more total digestible nutrients than L cows. During period 2, H cows produced 1.1kg more milk, consumed 4.2kg more grain, and 2.0kg more nutrients than those on L. Feeding grain 1:2.5 during days 1 to 45 did increase milk during that period and during remainder of the lactation. Feeding grain at 1:2.5 grain:milk ratio compared to 1:4.0 during day 46 to 180 or 270 did increase milk production during that period. The extent of these increases varied greatly between two trials. For both trials, fat-corrected milk per cow per day averaged 24.2, 24.4, 23.9, and 22.1kg for HH, HL, LH, and LL, and daily production during period 2 as a percentage of period 1 averaged 91, 84, 97, and 92. Returns above feed costs were about equal for HH, LH, and LL with HL greater. Overall the most satisfactory system was HL.