Abstract

In change-over trials, mid-lactation dairy cows were fed concentrate-supplemented, isonitrogenous and isofibrous perennial ryegrasslegume silage diets that satisfied energy requirements but were suboptimal with respect to metabolizable protein supply. Legumes were either birdsfoot trefoil with low levels of condensed tannins (typical for hemiboreal conditions), or white clover. Averaged over two experimental years, birdsfoot trefoilbased silage resulted in lower digestibility (P < 0.001) of dry matter (50 g kg(-1)), organic matter (52 g kg(-1)), neutral detergent fibre (120 g kg(-1)) and nitrogen (24 g kg(-1)) and lower rumen total volatile fatty acid concentration (7 mm; P = 0.009). Milk protein yield was 36 g d(-1) higher with birdsfoot trefoil silage (P = 0.002), while raw milk yield tended to be 0.8 kg d(-1) higher (P = 0.06). Rumen ammonia concentration was similar between diets, but milk urea concentration (P < 0.001), urinary urea excretion (P = 0.002) and faecal-N proportion (P = 0.001) were higher with birdsfoot trefoil silage. The results suggest that grassbirdsfoot trefoil silage produced in hemiboreal areas exhibits a protein-sparing effect in dairy rations, despite a low condensed tannin content that is further diluted by companion grasses and ration concentrate proportion.

Keywords

birdsfoot trefoil; white clover; silage; dairy cows; condensed tannins; nitrogen balance

Published in

Grass and Forage Science
2012, volume: 67, number: 4, pages: 546-558
Publisher: WILEY-BLACKWELL

Authors' information