Effect of feeding time on urinary and faecal nitrogen excretion patterns in sheep

Abstract

Understanding the relationship between time of feeding and subsequent nitrogen excretion may enable the development of better farm management strategies to reduce greenhouse gas output. This work examined the impact of time of feeding on urinary and faecal nitrogen losses. Sheep were fed either in the morning or the afternoon with annual ryegrass harvested at 0800 to ensure that feed quality was consistent for both feeding treatments. Peak urine volume occurred 8 h post feeding and the lowest urine volumes occurred immediately prior to feeding. Animals fed in both the morning and afternoon excreted approximately 60% of their urine volume and total urea within 12 h of being offered fresh feed. This work suggests that shifting animals to new pasture late afternoon would result in more urinary nitrogen being deposited at night when lower ambient temperatures should lead to reduced volatilisation and lower N₂O production.