Abstract

The opportunity to reduce nitrogen (N) losses to the environment from wintering systems for dairy cows may arise from a combination of restricted grazing systems and feeding low N diets to reduce N intake. Lack of information on urination behaviour and grazing intake during restricted grazing makes it difficult to predict animal and environmental responses. Three winter forage systems were simulated and pregnant, non-lactating Friesian x Jersey dairy cows were offered diets which varied in crop allowance and supplement: early sown-kale (EK) comprising 14 and 3 kg DM/cow/d of kale and barley straw; late-sown kale (LK) comprising 11 and 5 kg DM/cow/d of kale and green-chop oat silage; and fodder beet (FB) comprising 8 and 6 kg DM/cow/d fodder beet and grass baleage. Grazing behaviour, DM intake, DM utilisation and urination and faecal frequency, were recorded for six hours following morning crop allocation. After six hours, utilisation of EK, LK and FB crops were 82, 76 and 90%, corresponding to respective DM intake rates of 1.9, 1.4 and 1.2 kg DM/cow/hr. Average urination frequency (2.7 urinations/cow) and duration (9.1 seconds/urination) during the six hour grazing bout was similar for all treatments, and urine N concentration was also similar for each treatment (2.22 g N/L). As cows consumed a high proportion (> 75%) of their daily intake within six hours, and few urination events occurred during this period, the results indicate suitability for use of these systems in a restricted grazing regime combined with a standoff pad in order to mitigate losses of N to environment.

BAB, Jenkinson, GR Edwards, and RH Bryant

Proceedings of the New Zealand Society of Animal Production, Volume 74, Napier, 23-28, 2014