Nitrogen digestion and urea recycling in Hokkaido native horses fed hay-based diets.

The research investigates how nitrogen digestion and urea metabolism functions in Hokkaido native horses when they’re fed a diet primarily made of hay with varying protein levels.

Objective and Methodology of the Study

• The study aimed to understand how nitrogen (N) is digested and the process of urea Nitrogen (urea-N) metabolism in a specific breed of horses native to Hokkaido, Japan.
• These horses were fed with a roughage-based diet, which was mixed with different types and levels of protein sources.
• The horses in the study were all fitted with an ileum cannula, which is a thin tube inserted into a part of the intestine called the ileum. This allowed researchers to collect and analyze nutrients as they were being digulated.
• The study utilized four different diets, all varying in percentage compositions of timothy hay and soybean meal, with the protein content varying from 5% to 15% of the dry matter of the feed.

Results of the Study

• The apparent nitrogen digestibility both in the primary part of the digestive tract (pre-cecum) and the digestive tract on whole (total tract) was observed to be lower for the diet consisting of pure timothy hay than the diets supplemented with soybean meal or a combination of timothy hay and alfalfa hay.
• The proportion of Nitrogen digested after it passed through the ileum, the latter part of the intestine, in relation to the Nitrogen intake wasn’t affected by the type of diet.
• Production of urea Nitrogen was found to be a linear function of the Nitrogen intake i.e., as Nitrogen intake increases, the urea-N production also increases irrespective of the diet. However, the entry of urea Nitrogen into the gut was not affected by the diet’s composition.
• The study revealed that the percentage of urea-N entering the gut in relation to the production of urea-N was higher for the diet consisting mainly of timothy hay than the diets supplemented with soybean meal.
• The study showed that the use of gut urea-N for new protein creation (anabolic use) remained unaffected by different diet types, consuming 20 to 36% of the urea Nitrogen entry in the gut.
• The results of this study indicate that the recycling of urea-N provides an additional source of nitrogen that supports microbial fermentation in the posterior part of the digestive system when horses are fed low-quality roughage.