Long-term effect of level and pattern of winter concentrate allocation in dairy cows

Abstract

A total of 148 dairy cows were used in a long-term trial over their first four lactations. The experiment was designed to examine the effect of level and distribution of concentrate given during the winter period in addition to grass silage (ad libitum) and hay (4 kg/day) on milk production, reproduction, health and longevity. Cows in their first lactation were allocated to an experimental treatment in which they remained until in their fourth lactation or until culled (if this occurred before). Five treatments were compared: three levels of concentrate supply during the winter period (H, M and L) and, for levels M and L, two different allocation patterns (standard [S] or flat rate [F]). Winter concentrate allocation was individually predetermined for the first four lactations according to expected milk production. During summer, all animals grazed together as a single group. The occurrence of mastitis, reproductive performances (days open and interval between calving and first heat) and longevity were not significantly different between treatments. Foot lesions were more frequent in group H than in other groups. Effect of treatments on production performance was studied in cows having lactated for at least 12 weeks in the winter period in at least three successive lactations. Between the first and third lactation, live weight at calving increased by, respectively, 72, 44 and 36 kg in groups H, M and L, and milk yield over the first 12 weeks of lactation by, respectively, 8.3, 5.9 and 6.1 kg/day (P < 0.01). These differences were more pronounced in the highest producing cows. When considered over the first 40 weeks of lactation, the differences in production increase between the first and third lactation were no longer significant (1 175, 997 and 1 159 kg, respectively, in groups H, M and L), due to a greater compensation over the summer period for groups M and L during the third lactation. There was no significant difference in production and reproduction performances between groups S and F.