Sheep are ruminants similar to cattle. This means that sheep have a 4 compartment stomach, including a reticulum, rumen, omasum, and abomasum. There are some minor differences in the anatomy when comparing small ruminants to larger ruminants. Sheep have a larger mouth relative to their body size which allows them to have more mechanical digestion. This allows sheep to increase their chewing and ruminating ability to reduce the need for the processing of cereal grains. Sheep are also highly selective grazers when compared to cattle. When out on pasture, they have a higher digestibility than cattle on the same pasture because of selection. However, when they are fed in confinement and fed the same feed, the digestibility becomes similar due to reduced selection.
The reticulorumen is less compartmentalized in sheep and goats compared to cattle. This means there is less division of feedstuffs for digestion. Due to selection techniques, these compartments are not as necessary. In this compartment, microbes break down carbohydrates to use for energy and produce short-chain fatty acids for the host. Short-chain fatty acids include propionate absorbed for glucose production in the liver, acetate is the most abundant and is used as a precursor for other molecules, and butyrate for BHBA (Beta-hydroxybutyric acid). Glucose cannot be fed directly to sheep to increase blood glucose. The reticulorumen will digest this glucose to produce SCFAs at a rate which will cause acidosis and not increase the blood glucose at all. Crude protein provides nitrogen for microbes and metabolizable protein for the host. Urea is a non-protein nitrogen source in ruminant diets. This means that the nitrogen in urea is recycled through the body and used by microbes in the reticulorumen to produce proteins instead of being directly absorbed.
The omasum in small and large ruminants serves the same role but is larger relative to body size in larger ruminants. The leaf-like structures in the omasum use muscle contractions to absorb water and SCFAs from the rumen contents. The digesta become very compact and dry before moving into the abomasum for gastric digestion. The abomasum is the true stomach of the ruminant that uses gastric acid (HCl) to digest feed. Unlike the omasum, sheep and goats have a larger abomasum relative to body size than cattle. Protein digestion begins in this compartment and continues through the intestines. The amino acids from protein digestion and glucose from starch digestion are then absorbed in the small intestine. The large intestine is responsible for recovering more water, some digestion and fecal pellet formation in small ruminants.
There are of course a lot more details about how each part of the digestive tract functions but I am going to leave it at this for now. Please let me know if you have any questions. Hoping to have another blog post up this week about our sheep products and a little more into nutrition and flushing.
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