Effects of added high quality dehydrated alfalfa in maize silage diet given to dairy cows

Abstract

Effects on milk production of added high quality dehydrated alfalfa in a maize silage diet were assessed by comparing to a control diet 3 experimental diets containing either 2.5 or 5.0 kg (2.5L or 5.0L) of dehydrated alfalfa in a chopped form or 5.0 kg (5.0C)of a pellet form of the same alfalfa (19 % CP, 0.74 UFL). In a second trial, control and 2.5L diets were tested using a higher energy content alfalfa (23.8 % CP, 0.88 UFL). Maize silage was offered on an ad libitum basis and diets had the same net energy and PDI content. When 2.5L diets were fed, milk production was improved by 0.6 kg/d in trial 1 and by 1.0 kg in trial 2, milk fat content was decreased (-1.5 et -1.8 g/kg respectively in trials 1 and 2), and milk protein content did not change compared to the control diets. Moreover, dry matter intake was higher on 2.5L diets (+0.7 kg et +0.9 kg respectively in trial 1 et 2) thus energy intake was improved despite the lower energetic value of dehydrated alfalfa compared to maize silage (0.95 UFL/kg DM). When 5.0L diet was fed, milk protein content was lowered (-0.6 g/kg) but milk production and DM intake were unaffected compared to control diet. Compared to the chopped form, grinding did not affect milk production and milk composition but DM intake was higher. It was concluded that mixing about 3 kg of dehydrated alfalfa in a maize silage based diet allowed to modulate milk composition thus increasing milk protein output without any change in milk fat production.