Effect of concentrate supplementation on herbage intake and milk yield of dairy cows grazing an alpine pasture

The research was performed on a natural alpine pasture (at an average altitude of 1300 m) from June to August, with 18 Brown Swiss cows divided into three groups and fed different levels of concentrates above 12 kg 4% fat corrected milk (FCM): low (L) 1 kg per 3 kg FCM, medium (M) 1 kg per 2.5 kg FCM and high (H) 1 kg per 2 kg FCM. Herbage intake was estimated during an initial 21 day period with the n-alkanes method, by collecting daily four grab samples of faeces per day and 60 samples of herbage with the hand-plucking technique. Milk production and the fat and protein contents were recorded for the entire 3 month experimental period. The average intake of herbage (12.2 kg OM) during the 21 day period was not significantly influenced by the level of supplementary concentrates. During the entire period, the production of FCM showed an increasing trend, but without significant differences, from group L to group H, namely 15.0, 15.8 and 16.9 kg, respectively. The protein content was highest (although not significantly) with the highest level of concentrates. The possibility that the lack of a relationship between herbage consumption and concentrate level was principally due to the high herbage NDF content was discussed.