Diurnal Concentration of Urinary Nitrogen and Rumen Ammonia Are Modified by Timing and Mass of Herbage Allocation
Graduate School, Faculty of Veterinary Sciences, Universidad Austral de Chile, PO Box 567, Valdivia, Chile
Institute for Agricultural Research, Remehue Research Centre, PO Box 24-0, Osorno, Chile
Department of Agricultural Science, Lincoln University, PO Box 7647, Lincoln, New Zealand
Animal Production Institute, Faculty of Agricultural Sciences, Universidad Austral de Chile, PO Box 567, Valdivia, Chile
Animal Science Institute, Faculty of Veterinary Sciences, Universidad Austral de Chile, PO Box 567, Valdivia, Chile
Author to whom correspondence should be addressed.
Received: 4 October 2019 / Revised: 1 November 2019 / Accepted: 8 November 2019 / Published: 13 November 2019
Low nitrogen use efficiency in grazing dairy cows leads to high urinary N excretion, which contributes to greenhouse gases emission. This problem has been associated with high N and low energy intake, increasing rumen ammonia (NH3) concentration, and thereby, increasing urinary N excretion. Under this situation, it is important to discover nutritional and grazing management strategies that allow reduced urine N excretion in the pasture. This study evaluated whether changes in time of herbage allocation and herbage mass modify the diurnal pattern of urinary nitrogen (N) concentration and ruminal NH3 of lactating dairy cows. We found that the combination of time of herbage allocation and herbage mass modified rumen NH3 production and urinary N concentration. Results suggest that maintaining cows in the holding pen at the milking parlor for two hours after morning and afternoon milking could allow collection of urine from cows in the slurry pit during peak N concentration, returning cows to the pasture at a time of day when urinary N concentration is decreased.