Practical implications of comparative digestion in farm animals

Monogastric (non-ruminant) animals cannot digest fibrous feed (cellulose, hemicellulose) and depend on high quality, low-fiber concentrate diets. Among the monogastrics, horses and rabbits, due to their well developed caecum is less efficient than in the rumen. Therefore, horses should be fed good quality forages. On the other hand, ruminants, because of efficient microbial fermentation in the rumen, have acquired the ability to digest a wide range of roughages, including poor quality cereal straws and other crop residues. Ruminants can also utilize non protein nitrogen from sources such as urea as a dietary crude protein and convert it to a protein of high biological value (microbial protein).
The unique digestive features of ruminants enable them to utilize agro-industrial by products and wastes which cannot otherwise be used by monogastrics, including man. As ruminants depend largely on the fermentation products of the rumen (VFA's and microbial protein), conditions in the rumen should be optimal at all times to support efficient fermentation. This can easily be achieved by taking care of the nutrient requirements of rumen microbes. Recent developments in ruminants nutrition have emphasized that these animals should be fed in such a way that their capacity to utilize roughages and non-protein nitrogen is exploited to the greatest extent possible, and at the same time high quality feeds (such as good quality feeds and starches) should be protected from rumen fermentation so that they escape from the rumen and are efficiently digested and abosrbed in the small intestine. Unlike ruminants, monogastrics cannot synthesize amino acids and vitamins B and K. Therefore they depend on feed resources for these nutrients.

Functions of various parts of the digestive tract: Stomach - 2

Earlier Post: Functions of various parts of the digestive tract: Stomach
Omasum: The third compartment of the ruminant stomach is known as the omasum. It constitutes about 12.6% of the total volume of the stomach in cattle, buffaloes, sheep and goats. The inner lining of the omasum is raised into longitudinal folds are pillars, which greatly increase the surface area. The principal function of the omasum is to absorb water and reduce size of the feed particles. The contents of the omasum are much drier than those of the rumen and abomasum. Because of the small size of the omasum, its contents are not retained for long and are passed on to the abomasum.
Abomasum: This is the fourth and last chamber of the ruminant stomach. It resembles the simple stomach of the monogastric animals and is the only glandular part of the ruminant stomach. The inner lining of the abomasum has folds which are more prominent in the glandular region. It secretes hydrochloric acid and pepsin. The acidic environment of the abomasum causes destruction of microbial cells which are subsequently digested by the pepsin secreted into the abomasum. The rate of abomasal secretion is influenced by the volume and composition of ingesta entering the abomasum. The digesta leaving the abomasum (in a ruminant) and the simple stomach (in a non-ruminant) is called chyme.
Development of the stomach in young ruminants: In ruminants, the rumen is small and non - functional at birth. The abomasum, on the other hand is comparatively large and well developed. As the animal grows, the rumen gradually develops and attains a size which is 10 times greater than the abomasum in adult animals. Since the rumen does not play any role in digestion during early life, the milk suckled by the calf bypasses the rumen and goes directly in to abomasum through a special mechanism, the oesophageal groove. In the abomasum an enzyme, rennin, is secreted which has a strong coagulating action on milk. This helps in retaining the milk for longer time in abomasum for further digestion. The oesophageal groove is a tube like structure with a slit. Suckling and swallowing of milk and other liquids causes closure of the oesophageal groove, thus directing the liquid food to the abdomasum. Ingestion of solid food causes the oesophageal groove to open, allowing the feed to drop in to the rumen. As the intake of growing calf gradually changes from milk to solid feed, the stomach compartments, particularly the rumen, increase in volume, formation of papillae on the internal surface, and establishment of rumen micro-flora. Early development of the rumen can be encouraged by offering good quality solid feed after two weeks of age. This can also help in early weaning of  young calves.
B. Non - Ruminants (Mono Gastrics): In these animals, the stomach is a "V" - Shaped muscular sac. Muscular contractions of the stomach wall help in breakin gdown the feed particles, and at the same time cause mixing of the stomach contents. About two thirds of the inner surface of the stomach wall has glands which secrete gastric juice containing mainly hydrochloric acid and the enzyme pepsin. The pepsin digests protein into peptides and amino acids and requires acidic medium for its action. Hydrocholoric acid helps in maintaining acidic pH in the stomach. The feed is exposed to gastric enzymes ofr some time, and the semi-digested feed is passed to the small intestine through an opening controlled by sphincter muscles.

Note: Next post on this blog will be comprised of details about "Small Intestine".

Introduction to Digestion in Farm Animals

Digestion in animals involves mechanical, enzymatic, and microbial processes in the gastrointestinal tract, which convert large feed particles to a size which can be absorbed, transported, and used by the animals. The digestive systems of all farm animals are not the same, rendering them less competitive and able to adapt to a wide range of available feed resource niches. Based on the structure and functions of the digestive tract, farm animals are divided into two major groups:  ruminants or polygastrics, e.g. cattle, buffaloes, sheep, and goats; and non-ruminants or monogastrics, e.g. horses, donkeys, rabbits, dogs and cats. The key difference between these two groups of animals lies in the structure of the stomach. Ruminants, as opposed to non ruminants, have three additional stomach compartments where digestion takes place in different environments. In general, for farm animals the processes associated with digestion include prehension, ingestion, grinding or mastication, digestion of feed, absorption of nutrients, and excretion of waste products.