Nutritive characteristics, mineral concentrations and dietary cation–anion difference of feeds used within grazing-based dairy farms in Australia

Feed types consumed by cows on 44 contrasting dairy farms from all major dairy regions in Australia were identified and sampled on five occasions over a 15-month period to determine nutritive characteristics and mineral concentrations. Perennial ryegrass was the most dominant and commonly used forage, although a broad range of other home-grown forages was also grazed or conserved. Almost all farms utilised cereal or legume grains or grain-based concentrates, as well as a range of by-products and mineral additives. The present study has documented, for the first time, the nutritive characteristics, mineral concentrations and dietary cation–anion difference (DCAD) of the broad variety of feed types used on dairy farms across Australia, and has also highlighted the substantial variation that can occur among and within feed types. While there were effects of season, region and some defined farm-management practices on important nutrients for specific feeds, among-farm variation was generally large. These results suggest that farmers and nutritionists should be mindful when formulating dairy rations using feed nutritive characteristics and mineral concentrations reported in feed databases, as there is a potential for considerable variation in specific feeds. In particular, these defined differences suggest that appropriate feed testing of grazed pasture and conserved forage should be undertaken on at least a seasonal basis to monitor changes in nutritive characteristics and mineral concentrations, so as to optimise dietary formulation for the nutrition of grazing dairy cows.