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
The aim was to investigate the effect of selenium and vitamin E injection frequency in late pregnancy on lamb performance and blood biochemical parameters of ewes. The treatments were:
1) received only basic ration (witness),
2) once received an injection form of selenium and vitamin E (E + selenium) in 9 weeks before delivery.
3) She received two injections + selenium at 9 and 6 weeks before delivery.
4) She received three injections of E+selenium at 9 and 6 weeks before delivery and one week after delivery.
Performance of lambs, serum lipid parameters such as triglyceride, cholesterol, VLDL, LDL, HDL, AST and CPK enzymes, elements of iron (Fe), copper (Cu) and zinc (Zn) and the concentration of T4 and T3 hormones were measured. Six weeks before delivery, in treatment 2, T4 concentration decreased and the ratio of T3 to T4 and Zn concentration increased. One week after delivery, in treatments 2 and 3 compared to treatment 1, the concentration of T3 and the ratio of T3 to T4 increased and the concentration of Zn and AST decreased.
In treatment 3, HDL concentration increased and LDL decreased. Fe concentration in treatment 3 was lower than treatments 1 and 2. Cu concentration did not differ between treatments. Two weeks after delivery, the concentration of T3 and the ratio of T3 to T4 were higher than other treatments. The concentration of triglyceride, cholesterol and LDL, AST and CPK in treatment 4 was lower and HDL concentration was higher than treatment 1 and 2, but there was no difference between treatment 3 and 4. The concentration of Fe, Zn and Cu in treatment 3 and 4 was lower than treatment 1. There was no difference between the birth weight of the lambs, the weight of one and two weeks. 45-day weight and daily weight gain in treatments 2, 3 and 4 were higher than treatment 1, but daily weight gain was not different between treatments 2, 3 and 4.
In general, at least one and maximum two injections of selenium and vitamin E at the end of the pregnancy period are sufficient and necessary to improve the balance of thyroid hormones, regulate fat metabolism and improve the performance of lambs.
Significantly decreased and the ratio of T3 to T4 as well as the concentration of Zn increased (P < 0.05). Lipid parameters, AST, Fe and Cu were not affected. One week after delivery, the concentration of T4 in treatment 3 was significantly lower than treatment 1 and 2, but the concentration of T3 and also the ratio of T3 to T4 in treatment 2 and 3 were higher than treatment 1. The concentration of TG, Chol and VLDL-C was not significantly different between the treatments, but in treatment 3, the concentration of HDL-C was higher and LDL-C was lower than other treatments. The concentration of Zn and AST in treatment 2 and 3 was lower than treatment 1. Fe concentration in treatment 3 was lower than treatments 1 and 2. Cu concentration was not significantly different between treatments. Two weeks after delivery, the concentration of T4 in treatment 4 was significantly lower and the concentration of T3 as well as the ratio of T3 to T4 was higher than other treatments. The concentration of TG, Chol and LDL-C, AST and CPK in treatment 4 was lower and the concentration of HDL-C was higher than treatments 1 and 2, but there was no difference between treatments 3 and 4.
The concentration of Fe, Zn and Cu in treatment 3 and 4 was lower than treatment 1, but no difference was seen between treatments 1 and 2. In lambs, birth weight, one and two week weight did not show any significant difference. 45-day weight and daily weight gain in treatments 2, 3 and 4 were significantly higher than treatment 1, but daily weight gain was not different between treatments 2, 3 and 4. In general, the results of this research showed that at least one and maximum two injections of selenium and vitamin E to ewes at the end of the pregnancy period are sufficient and necessary to improve the balance of thyroid hormones, regulate fat metabolism, and also improve growth performance in born lambs. is.
Authors: Zahra Panahi Derche, Hassan Ali Arabi, Abbas Farah Avar, Mustafa Maliki, Hadi Yazdani
Boali Sinai University, Hamedan
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