The digestion in camelids ; a comparison to ruminants

Abstract

Studies on digestion and metabolism in camelids have, over the past 15 years, benefited from technical and methodological progress made on ruminants. Today, reliable scientific information allows to compare the digestive and metabolic aptitudes of these two types of animals. The anatomy of the forestomach and the feeding behaviour of the camelids and ruminants are very different. Such differences have consequences on the digestion of food. Even though the microbial population is qualitatively the same, the cellulolytic activity of the bacteria is much more important in the camelid forestomach and the retention time of solid particles in the forestomach is much longer. The evolution of these two parameters is responsible for a better digestion of organic matter and of the cellulosic fractions of the rations. Due to better buffered digesta, the addition of large amounts of starch to a forage-based diet has not the negative effects on microbial cellulolysis usually observed in ruminants. Furthermore, camelids excrete less nitrogen in the urine and efficiently recycle urea via the mucous wall of the forestomach. This economy of nitrogen allows them to maintain a minimal production of microbial proteins for cases when dietary nitrogen is insufficient. However, camelids are much more sensitive than ruminants to risks of intoxication due to excess soluble nitrogen in rations. Reduced maintenance energy levels and a better yield of transformation of metabolisable energy into net energy, go along with a better use of ingested energy by camelids. A greater stability of physical-chemical conditions (pH, NH3) in the fermenting medium of the C1 compartment of camelids after feeding, as well as the higher outflow rate of the liquid phase, are elements that favour the development and activity of microorganisms.