Lesson 14. DIGESTIVE SYSTEM AND ROLE OF NUTRIENTS IN DAIRY CATTLE
Module 9. Feeding of dairy animals
DIGESTIVE SYSTEM AND ROLE OF NUTRIENTS IN DAIRY CATTLE
Feeding is the important factor influencing productive function of the dairy animal and milk production in particular. The feed that the animal consumes, after undergoing digestion, releases the nutrients for the synthesis of milk. For maximum production, sufficient nutrients are to be provided in the ration of the animal so that the animal utilizes them and high milk production can be achieved. Hence a balanced ration should be provided to the dairy animal in order to achieve maximum out put of milk. In this chapter digestive system of cattle, role of various nutrients and their requirements, various feed resources and their nutritive values are discussed.
14.2. Digestion of the Ruminants
Fig. 14.1 Digestive system of Cattle14.2.1 Digestive system of ruminants
The digestive organs of ruminants consists of mouth, oesophagus, rumen, reticulum, omasum and abomasum, small intestine, and large intestine.
The cow takes food into the mouth. The food taken in by the animal after mixing with saliva enters into the rumen through oesophagus.
Cattle stomach has four compartments such as:
The herbivores generally have an expanded part of digestive system so as to hold the bulky fibrous feeds and delay their passage to undergo microbial fermentation. In ruminants this enlarged part is represented by the rumen which is the biggest compartment in their four-chambered stomach.
The micro- organisms are benefited as follows:
The temperature of rumen is 38- 40°C. This is ideal for the growth of micro-organisms and they flourish as if grown in an incubator.
Proteins are attacked by bacteria and the end-products are usually ammonia and short chain fatty acids. A considerable proportion of the protein needs of the animals are met through such microbial protein. These micro-organisms ultimately pass from the rumen to the lower stomach and intestines, where digestion of the microbial protein takes place in the same way as protein is digested in non-ruminants.
Reticulum: It is a smaller sac partially separated from rumen. This organ has a thick wall resembling honeycomb. The contents of rumen and reticulum mix freely. Reticulum is connected to omasum, the third compartment of stomach through an opening on the right side of reticulum.
Omasum: This organ has many layers of muscular leaves giving it the resemblance to a book. After fermentation the ingesta passes through the reticulo-omasal orifice into the omasum. With the help of the muscular leaves having horny papillae the ingesta is squeezed out. Water and fatty acids so squeezed out are absorbed.
Abomasum: it is the true stomach in the ruminant. From this organ onwards the digestion taking place in ruminants is similar to that of non-ruminants.
Small Intestine: Duodenum is the first loop of small intestine. It is an important area because pancreatic duct and bile duct join.
Large Intestine: Absorption of water takes place from large intestine.
14.3 Role of Nutrients in Dairy Cattle
E.g.: water, proteins, carbohydrates, fats, minerals and vitamins are the well recognized feed nutrients.
220.127.116.11 Major elements
The dietary requirement of the essential major elements is more than 0.010% (100 ppm). The average tissue concentrations of these elements also exceed 100 ppm.
- Skeletal development in various species of farm animals is dependent on adequate calcium and phosphorus supply in the presence of vitamin D. Calcium deficiency in young animals is characterized by poor skeletal development and rickets. In adult animals chronic Ca deficiency leads to osteomalacia and osteoporosis. Dairy cows shortly after calving may develop milk fever, a condition characterized by low plasma Ca with symptoms of muscular spasms and paralysis.
- Phosphorus is the important element in the energy transformations of living cells involving formation and breaking of high energy P bonds. Pica or deprived appetite with tendency to chew objects like bones, wood .or leather is seen. Reproductive problems like anoestrus and low conception, rates are often seen in females having P deficiency.
- Sodium, Chlorine and Potassium are mainly concerned with maintenance of acid-base balance and osmotic pressure in the animal body. Magnesium plays a vital role in many body processes especially as an activator in many enzymatic reactions.
18.104.22.168 Trace elements
The dietary needs and body concentrations of essential trace elements are always below 100 ppm. On the basis of present day knowledge, 14 trace elements appear to be essential.
- Iron is an essential part of the respiratory pigment hemoglobin.
- Presence of copper is necessary for the utilization of iron. Copper is also a constituent of some of the enzymes like cytochrome oxidize, catalase, tyrosine and ascorbic acid oxidize.
- Cobalt is a constituent of vitamin B12.
- Zinc plays an important role in keratinisation and calcification and, as a constituent of many important enzymes, it has an essential role.
- Iodine forms about 65 per cent of the hormone thyroxin of thyroid gland which regulates the development of the animal and the metabolic rate.
- Body contains comparatively larger quantities of sulphur, mostly in the organic form. The body can utilize mostly the organic sulphur which is part of the amino acids, methionine and cystine.
- Selenium in trace quantities is an essential nutrient in spite of its well-known toxic effect in larger doses which cause 'alkali disease' or blind staggers.
- Excess fluorine increases the incidence of dental caries and bone abonormalities
Vitamins are vital constituents required by the body. They are classified as water soluble and fat soluble. Members of the B-complex and vitamin C belong to the category of water soluble vitamins whereas vitamins A, D, E and K form the fat soluble group.
22.214.171.124 Water soluble vitamins
Vitamins B-complex group includes thiamine (B1), riboflavin (B2) and vitamin B6 (Pyridoxine, pyridoxamine and pyridoxaI), niacin, pantothenic acid, biotin, folic acid, Choline and cyanocobalamine (B12),
- Thiamin as a constituent of the coenzyme carboxylase and otherwise plays an important role in intermediary metabolism.
- Riboflavin required to form many lipoprotein enzymes and coenzymes, which act at important stages in the metabolic release of food energy in the body.
- Niacin (Nicotinamide) is essential metabolically for all species of animals as it forms part of two important co-enzymes co enzyme I (NAD) and co-enzyme II (NADP).
- Vitamin B6 (pyridoxine, pyridoxamine and pyridoxal) helps in efficient metabolism of tryptophan.
- Feeding of raw egg-white has been found to produce biotin deficiency in many species due to presence of avidin in raw egg-white which makes dietary biotin unavailable.
- Folic acid plays an important role in intermediary metabolism.
- Choline is essential for the formation of cell structure.
- Vitamin B12 (Cyanocobalamine) prevents and cures pernicious anemia in human beings.
- Vitamin C is essential in the diet of all species
126.96.36.199 Fat soluble vitamins
Fat soluble vitamins include Vitamin A, D, E and K
- Vitamin A has four distinct biological functions; namely, bone formation and growth, vision, reproduction and maintenance of healthy epithelial tissue. Vitamin A deficiency symptoms are watering from the eyes, night blindness, loss of appetite, exophthalmia and infected eyes. This is followed by retardation of growth and malformation of epithelial and skeletal structures. Excess of vitamin A can cause toxicity. However animals have some built-in mechanism to guard against hypervitaminosis.
- Vitamin D has a major role in calcium and phosphorus metabolism. Its main role is to increase the absorption of calcium from the alimentary tract. Deficiency of the vitamin causes rickets in all species.
- Vitamin E (Tocopherols) is important for the health of reproductive system and act as antioxidants. Vitamin E has inter-relationships with selenium, sulphur containing amino acids, poly unsaturated fatty acids and antioxidants.
- Vitamin K is involved in the coagulation of blood. Cattle may develop deficiency of vitamin K when they consume large quantities of mouldy sweet clover hay.