EFFECT OF FIBROUS AND STARCHY CARBOHYDRATES IN CONCENTRATES AS SUPPLEMENTS IN A HERBAGE-BASED DIET FOR HIGH-YIELDING DAIRY-COWS

The effects of two concentrates composed of different carbohydrate sources (beetpulp versus maize) on intake, digestibility, yield and composition of milk by high-yielding dairy cows fed fresh herbage indoors was investigated. In 1988 two diets and in 1989 three diets were used with nine cows per diet. In 1989 concentrates were supplied on an equal amount of DM and in 1989 on an equal amount of energy. The animals received the concentrates after milking time. In 1988 the experimental period lasted for 8 weeks and in 1989 for 10 weeks. In 1988 intake of herbage DM tended to be higher on the maize-enriched diet, resulting in a significantly (P < 0.05) higher intake of OM and energy. Nitrogen intake was also significantly (P <0.001) higher but mainly as a result of an unintentional high crude protein content of the maize concentrate. In 1988 and 1989 the apparent digestibility of N was significantly (P < 0.05) higher on the starchy as compared with the fibrous diet. In 1988 the milk yield on the maize-enriched diet was significantly (P <0.05) higher than on the beetpulp-enriched diet partly due to a higher intake of energy. In 1989 no significant effect of carbohydrate source on milk yield was observed. Milk fat concentration declined as the proportion of starch in the diet increased. Milk protein content was not significantly affected by the source of carbohydrate.