Substitution of roughage by concentrates in dairy cows

Abstract

The effects of the concentrate supplementation level, the type of roughage and the type of concentrate on the substitution rate (SR) between roughage and concentrates have been studied over a course of 8 trials in three experimental sites. In each trial, the 3 levels of concentrates were compared using a 3x3 Latin square design, repeated with 3 or 4 groups of Holstein-Friesian crossbred cows in mid-lactation, each period lasting 1 month. The 8 trials corresponded to 8 different diets according to the type of roughage and the type of concentrates used. The SRs increase systematically with the concentrate supplementation level, on average 0.47 between L and M and 0.67 between M and H. For a given roughage, the increase in the energy concentration of the concentrate corresponds to an increase in the SR values, mainly between L and M. The average SR values observed when using maize silage (0.7) are higher than those observed with grass silage (0.53) and also for the hay (0.44). These trials show, looking at the 3 variation factors in the study, that in mid-lactation, the higher the energy balance is, the more important the SR values become.