Nitrogen digestion and urea recycling in Hokkaido native horses fed hay‐based diets
Nitrogen (N) digestion and urea‐N metabolism in Hokkaido native horses fed roughage‐based diets containing different types and levels of protein sources were studied. Horses (173 ± 4.8 kg) fitted with an ileum cannula were fed four diets consisting of 100% timothy hay (TH), 88% TH and 12% soybean meal (SBM), 79% TH and 21% SBM, and 51% TH and 49% alfalfa hay at 2.2% of body weight. Dietary protein content varied from 5% to 15% of dry matter. Apparent N digestibilities in the pre‐cecum and total tract for the TH diet were lower than those for other diets. However, the proportion of post‐ileum N digestion to N intake was not affected by the diets. Urea‐N production was linearly related to N intake, but gut urea‐N entry was not affected by the diets. The proportion of gut urea‐N entry to urea‐N production tended to be higher for the TH diet (57%) than the two SBM diets (39%). Anabolic use of urea‐N entering the gut was not affected by the diets (20–36% of gut urea‐N entry). These results indicate that urea‐N recycling provides additional N sources for microbial fermentation in the hindgut of Hokkaido native horses fed low‐quality roughages.
No Supplementary Data
No Article Media