Fiber or insoluble carbohydrate fibers are one of the important and significant parts of dairy cow's diet. Unlike other animals, cows and other ruminants are able to use this part of their diet to a significant extent to meet their nutritional needs. They are an advanced fermentation plant that converts various carbohydrate compounds into volatile fatty acids and uses them to provide an important part of the required energy. A better understanding of the mechanisms of digestion of fibers in the rumen can help us to get better efficiency from this part of the feed. In this article, we are going to discuss the optimal use of fibers to produce milk in cows.
What is the role of fiber in cattle nutrition?
Fiber refers to the structural parts of plant cells that form part of the analysis of feed types. Fibers in the feed of monogastric animals such as poultry have a lower digestibility, but ruminant animals are able to digest them to a greater extent. The importance of fiber in the feed of ruminants is due to the optimal digestive function of other nutrients in maintaining the health of the digestive system. and the quantity and quality of effective production
Is. Therefore, the amount and nature of fiber in cattle feed plays an effective role.
Chemical definitions of fiber in cattle feed
Fiber, as mentioned earlier, is a part of feed that mainly has a structural role and its digestibility is much lower than other nutrients. It is mainly composed of cellulose, hemicellulose, pectin and lignin.
Crude fiber (CF): contains the least amount of fiber and is obtained after washing the feed with acid and base.
Acid detergent-insoluble fiber (ADF) is very close to crude fiber, mainly consisting of cellulose and lignin. Neutral detergent-insoluble fiber (NDF) mainly consists of cellulose, hemicellulose, lignin, and a little of the protein part of the feed.
Nutritional implications of fiber in animal feed
Indigestible fiber (iNDF): is the part of the cellular diarrhea that has not been digested in the digestive tract of the cow for a long time (144 hours).
uNDF: The indigestible part of forage after 240 hours of incubation, this number is 30 hours for non-forage sources. In fact, INDF is a part of INDF that will never be digested.
Fiber with digestive potential (pdNDF)
xNDF: digestible protein
Effective fiber (eNDF): the amount of fiber that is effective for maintaining milk fat.
Physically effective fiber (peNDF) returns to the physical form of feed and is effective in maintaining rumination and optimal lactation performance.
Nutritional implications of fiber in cattle feed. Indigestible fiber (INDF) is a part of the cell wall that is digested in the digestive tract of cattle over a long period of time (144 hours):
Factors affecting fiber digestion in the rumen
Fibers are slowly digested in the rumen of ruminants due to their physical structure and the coiling of lignin in their structure. The rate of fiber digestion in the rumen may be influenced by the following factors.
1- The structure and nature of fiber (pectin, cellulose and hemicellulose ratios)
2- The amount and structure of mature lignin, plant species, environmental stressors for plants during growth
3- Particle size
4- Feed passage rate is greatly influenced by UNDF feed particle size and dry matter consumption and its effects on rumen dynamics.
5-The amount of rumination
6- Rumen microbial population that is influenced by diet and environment.
Physical digestion of feed by cattle
Ruminants reduce the size of forage particles by primary chewing. After swallowing, these particles float in the upper part of the rumen contents. The food particles then return to the mouth and become smaller by rumination and are smeared with saliva again. which naturally exists helps maintain rumen conditions.
Microbial digestion of fibers in the rumen
The first step of ruminal fermentation of fibers is the colonization of fungi and bacteria on feed particles. Many species of bacteria can secrete enzymes that speed up the process of fiber digestion. This type of bacteria is called fibrolytic. In addition, other microorganisms such as fungi and protozoa can similarly decompose fibers. Fibrolytic or fiber-decomposing bacteria are very sensitive to oxygen and severe anaerobic conditions (by measuring the potential decrease is measured) the maximum possible amount is needed to achieve colonization.
The digestion of fibers by each type of microorganism is different. Bacteria come into contact with the fibers and digestive enzymes such as cellulase and xylanase, which are secreted by them, break down the fiber. Silicate protozoa ingest plant particles, cellulose and xylan are broken down in cellular digestive vacuoles. This enzymatic digestion mechanism is very complex. Fungi also stick to food particles and penetrate into them. This also facilitates the digestion of fiber by bacteria.
Heavy livestock products
The amount of ruminal metabolism of fibers depends on the digestibility of fibers, the rate of fiber digestion and the rate of passage of fibrous matter through the rumen.
1. Forage digestibility (peNDF) depends on morphological factors such as maturity, leaf-to-stem ratio and ligninization of anatomy and plant species.
2. The rate of fodder digestion depends on the species differences in the structure and ratio of lignin and the degree of maturity of the plant.
3. The rate of passage can depend on the particle size, acute or sub-acute acidosis rumen abnormalities, the amount of feed moisture and the amount of dry matter consumed by the animal. The digestion of fibers in the rumen leads to the production of volatile fatty acids, which provide more than 70% of the energy needed for milk production. Therefore, the efficiency of fiber digestion in the rumen is an important component in the amount of milk production. Research has shown that for every one percent increase in the digestibility of NDF production
It increases daily by 0.24 kg and for the production of fat-corrected milk (FCM), this amount will increase to 0.25 kg.
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Mehdi Ehsani Farimani
Research and development manager of Sephermakian Fartak company
