Diet composition of grazing dairy cows with and without concentrate supplementation using different markers

摘要

The diet selection of dairy cows on multi-species pastures was investigated in a crossover study with 12 Swiss Holstein cows and 12 Holstein cows of New Zealand origin. All cows grazed full time and each cow was supplemented either with 0 or 6 kg concentrate per day. Both experimental periods consisted of a 21-day adaptation and a 7-day measurement period. Ihrcc marker groups, alkanes, long-chain fatty acids, and long-chain alcohols (LCOH), were analysed in feed and faeces samples to estimate diet composition based on non-negative least squares. In total seven feed groups were formed consisting of Loliumperenne, Dactylisglomerata, Trifolium repens, Taraxacum officinale, other grass species, other forbs and concentrate. The best discrimination of thefeed was achieved with LCOH, where 91% were correctly allocated, and the poorest with all three marker groups together (12%). The average diet estimation which came nearest to the botanical composition was achieved with alkanes and LCOH including a correction for faecal marker recovery. Results using this combination indicated no differences between cow strains but an effect of concentrate supplementation on herbage selection. 'Ihe aforementioned marker combination seems to discriminate satisfactorilyplant species selection of dairy cows, but further validation is needed.