Recycling of urea nitrogen to the gut of the tammar wallaby (Macropus eugenii)

• 1.1. The transfer of urea from plasma to the gut of tammar wallabies (Macropus eugenii) was studied using infusions of [¹⁵N]-urea and [¹⁴C]-urea in animals given either a high nitrogen chopped lucerne hay or a low nitrogen chopped oaten hay diet.
• 2.2. The proportion of urea entering the plasma pool which was degraded in the gut was similar on both diets (74–86%). Incorporation of urea into non-ammonia nitrogen in the gut was 1.1–1.7 g N/day in tammars given the high nitrogen diet, equivalent to 34–53% of dietary N intake, and 0.75–0.78 g N/day in tammars given the low nitrogen diet, equivalent to 103–112% of dietary N intake.
• 3.3. On the lucerne diet 63% of bacterial nitrogen in the midstomach was derived from ammonia.
• 4.4. It appears that blood urea is transferred into the stomach of tammars given lucerne more readily than into the rumen of sheep given lucerne.