Urea excretion in ruminants. III. The role of the hind-gut (caecum and colon)

Abstract

The transfer of endogenous nitrogen to the hind-gut digesta of sheep and its relationship with urinary nitrogen excretion were studied concurrently with the estimation of nitrogen balance and of dry matter digestibility in sheep fitted with a re-entrant ileal cannula. Infusion of glucose into the terminal ileum increased the excretion of faecal nitrogen by 1 g/day, while the urinary urea nitrogen excretion decreased by 1 g/day, relative to the respective control levels. Plasma urea nitrogen concentrations remained unchanged. When glucose was infused, the excretion of nitrogen in the faeces was higher than the amount of nitrogen passing the terminal ileum. It is suggested that endogenous urea nitrogen was transferred to the digesta of the hind-gut, where it was incorporated into microbial protein and subsequently excreted in the faeces. The transfer of urea from the blood to either of the fermentative areas of the gut tract is apparently the preferential pathway of urea excretion in ruminants.

Spatial and temporal variation in nitrogen and phosphorus concentrations in faeces from springbok in the Kalahari

“…It has been found that elevated levels of faecal nitrogen may occur during a dry season due to the secretion of urea through the intestinal wall back into the gut lumen (Thornton et al 1970). Higher levels of faecal nitrogen may also be due to a shift in the feeding strategy of a mixed feeder, changing its diet to include more browse food plants than grasses during the winter months (Mbatha & Ward 2006).…”

The effect of a hindgut fermentation on urea metabolism in sheep nourished by intragastric infusion

“…In each of the above studies (0rskov et al 1970;Thornton et al 1970;0rskov & Grubb, 1978) the increased excretion of N in faeces was accompanied by a decrease in the excretion of N in urine and it was suggested that this inverse relationship indicated a transfer of urea N from the blood to the hindgut digesta. A similar conclusion can be drawn in the present work, since a decrease in the excretion of both total N and urea N in urine was seen at the higher level of hindgut infusion ( Table 2).…”

“…Thus 0rskov et al (1970) infused starch into the caecum of sheep given dried grass diets and calculated that 100 g of starch fermented in the large intestine was associated with an increase in the faecal excretion of 'bacterial and endogenous debris-N' of about 1 g/day. Similarly Thornton et al (1970) infused up to 90 g glucose daily to the ileum of sheep receiving a diet of oat hulls and lucerne chaff and showed an increase in faecal N of 1 g/day at the highest level of glucose infusion. 0rskov & Grubb (1978) also observed an increase in faecal N excretion of 05 g/day when 50 g of a mixture of glucose and methyl cellulose was infused at the terminal ileum of a single sheep nourished by intragastric infusion.…”

“…0rskov, Fraser, Mason & Mann (1970) and Thornton, Bird, Somers & Moir (1970) have shown that increases in hindgut fermentation achieved by ileal infusion of nutrients can result in a transfer of urea from blood to the lower digestive tract, but the extent of this transfer in relation to whole body urea metabolism does not appear to have been examined previously. The opportunity was taken in the present work to investigate also the effect of hindgut fermentation on endogenous urinary nitrogen (EUN) excretion and on the partition of nitrogen (N) between urine and faeces when N-free infusions were given.…”

The digestion of complex carbohydrates in the large intestine of the growing pig: effects on nitrogen metabolism

“…The microflora in the hindgut of sheep have more than adequate amounts of nitrogen (N) in relation to energy (Mason et al, 1977). Therefore, in sheep, the presence of fermentable energy in the cecum, sup plied either by the diet (Thornton et al, 1970) or by in fusion via a cannula (0rskov et a].., 1970;Rerat, 1978) , results in an increase in fecal N, mainly in the form of bacterial protein.…”