Fiber in cattle feeding

Fiber in cattle feeding

It is impossible to form a nutritionally balanced diet without having a complete understanding of the structure of nutrient components of feed and their effect on biological processes in the animal's body. In modern terms new technologies of dairy production are introduced, large-scale cows of high-yielding breeds are purchased in large quantities. Naturally, livestock breeders have difficulties in technological preparation.

In this article, an attempt is made to describe a simplified structure of carbohydrates of vegetable feed used in modern foreign technologies. I hope that the material presented in this article will be useful for many farmers who recently embarked on the path of mastering new technologies.

Carbohydrates are one of the most important components of the biochemical composition of feed. The quantitative content of them in the diet greatly determines the state of life of the animal organism as a whole.

Typically, vegetable carbohydrates are divided into two groups: fibrous (structural) and non-fibrous (non-structural).
Structural carbohydrates are carbohydrates that are part of the fiber of plant foods. All other types of carbohydrates are non-structural. Next, consider the current classification of the main types of carbohydrates and get acquainted with the most important common characteristics of them, which are used for balancing the diets for cattle.

Structural carbohydrates (CS)

Until now, in the domestic practice, only one parameter, raw fiber, was used to estimate the content of SU in rations. The term "Raw cellulose"Is a generalizing for all carbohydrates that make up the structure of the plant cell.

Naturally, understanding the nature of the effect of fiber on the digestive processes in the gastrointestinal tract of the animal also has a generalized character, despite the fact that carbohydrates are very different in their composition from the physical, chemical and biological properties of the SU.

In other words, the use of raw fiber alone to evaluate the nutritional properties of vegetable feed does not ensure a balanced diet.

In countries with highly developed dairy farming technology, by the end of the 1990s, a new set of parameters for the carbohydrate composition of feeds, as well as a technology for measuring and applying them for balancing rations, had been used to replace raw fiber.

Neutral-detergent fiber (NIR)

In laboratory conditions, the NDC content in the feed is measured by the amount of residue after treatment with neutral solvents. This residue is basically a combination of three types of carbohydrates: cellulose, hemicellulose, and lignin.

The most difficult digestible fraction of NDC is lignin (wood). The greater content of lignin corresponds to the lower quality (digestibility) of cellulose. Lignin is a sign of the maturity of the plant. As the maturation of lignin content in plant cells increases, digestibility and nutritional value of feed is reduced.

In general, the NIR is an indicator of the quality (digestibility and nutritional value) of plant foods. The ratio between the components of the NIR determines the digestibility, and hence the nutritional quality of the vegetable feed.

In addition, due to the fact that fiber is the most bulk fraction of feed, the content of NIR also assesses the potential consumption of the ration (the filling of the rumen) to animals, taking into account the capacity of the rumen.

It is recommended to keep the NIR content in the diet at least 28%. The optimal value of NIR, at which the best digestibility of fiber in the rumen is observed is 37% of the dry matter.

Here it is necessary to make a very important observation related to the presence of a certain amount of nitrogenous compounds remaining after treatment with a neutral solvent, determined as part of the crude protein of the whole food.

This fact is a consequence of technical features of the production of laboratory tests and is a "concomitant" effect. We will mention this part of the crude protein below when analyzing the balance of dry matter components.

NDC of bulk forages

The optimal value of the OND is 1.1-1.2% of the animal's live weight

Saying that the NIR is the largest fraction of feed, we made a simplification in the sense that fiber is not only a part of voluminous but also concentrated fodder of plant origin.

Therefore, the filling of the scar should be assessed only for that part of the NIR, which is formed by bulk plant foods.

On practice, NDC of bulk forages separate into a separate parameter. Within the limits of this article, we will designate it as the abbreviation of the ODCA. ONCD is one of the most important parameters for balancing the ration, which determines the quality and speed of the fermentation process in the rumen, the ratio of the varieties of bacteria, the activity of the chewing process,

Studies have shown that there is an optimal value of the OND, which is 1.1-1.2% of the animal's live weight.

Effective NIR

Since the suppliers of the ONCDs in the diet are bulk fodder (hay, hay, silage, etc.), characterized by the presence of large stems of plants, it makes sense to assess the need for their grinding before feeding the ration.

The assumption is based on the peculiarities of cows eating bulk fodder. If the particles of plants are large in size, then the cow, when eating, sorts them, i.e. Chooses smaller fractions, because of which the largest part of the feed is not eaten by the cow. This means that the previously calculated balanced diet is not implemented and the expected results will not be achieved. Therefore, the bulk feed needs to be ground.

Question: What is the degree of grinding?

The maximum particle size of bulk feed should be such that the cow could not sort it. This will be ensured if the largest fractions of the feed are not more than one-third the breadth of the mouth of the cow. Usually, it is less than 5-6 cm.

When the size of the feed particles is too small, the cow's motivation for chewing decreases, which in turn reduces the activity of the salivary glands and reduces the amount of saliva.

Since saliva contains substances called buffers that provide an optimal pH value in the rumen, low chewing activity usually leads to an increase in acidity in the rumen, a decrease in bacterial activity and productivity, and subsequently to acidosis.

Hence the conclusion follows that the requirements for taking into account the above conclusions should be presented to the grinding process, that is, the maximum particle sizes should not be more than 5 cm, and the content of fine particles should be minimal. The predominance of 3 mm or less particles leads to a reduction in chewing activity (time spent on chewing), the fat content of milk and pH in the rumen.

To quantify the quality of grinding, use the parameter "Effective NIR"(END). The term "effective" here has the meaning of an effective particle size, i. E. Size, which provides the stimulation of the chewing process.

Table 1. Quantitative evaluation of ENDs is made by sifting the crushed coarse feed through three sieves with different hole diameters *

Sieve Diameter of the hole, mm The size of the delayed particles Recommended percentage in feed mixes
Top Sieve 19.0 mm More than 19 mm 2 - 8 %
Medium sieve 8.0 mm 8 to 19 mm 30 - 50 %
Bottom sieve 1.3 mm 1.3 to 8 mm 30 - 50 %
Pallet - Less than 1.3 mm Less than 20%
* NRC recommends, as the optimum, the following ratio of the particle size of the crushed coarse feed in the ration

Acid-detergent fiber (FTC)

Acid-detergent fiber is defined as a fiber residue after treatment with acidic solvents. The composition of the FTC includes mainly cellulose and lignin, i.e. Difficult to digest carbohydrates. Thus, the FDC differs from the NIR with a very low hemicellulose content. In practical calculations, it is believed that hemicellulose is absent.

Quantitatively, the FDC correlates fairly well with the energy content in the feed, so this parameter is sometimes used in regression formulas to calculate digestible energy. In addition to the FTC, a parameter that determines the quantitative content of lignin in the feed as an index of fiber digestibility is used to balance the ration, which makes it possible to assess the digestibility of the entire diet as a whole.

Non-structural carbohydrates (NSU)

It is quickly absorbed in the body carbohydrates, which include simple sugars, fructose, starch and others. They are well absorbed, have a strong effect on blood sugar (glycemic reaction), are partially absorbed by microorganisms in the rumen.

In the domestic practice, traditionally, the values of the contents in the feed of sugar and starch, as separate parameters of it, were used to analyze the ration being formed. Standards have been developed for these carbohydrates.

In some foreign technologies, this division of carbohydrates was not used, but the generalized aggregate parameter NSC (Non-structural carbohydrates - non-structural carbohydrates) was used.

This approach, like in the case of raw fiber, did not allow us to obtain a sufficiently accurate estimate of the ration being formed. Currently, all technologies use starch and sugar as separate components of NSO.

The CNCPS (CPM) technology developed with the participation of the Cornwall University of the US uses much more detailed detailing of the components of all carbohydrate feeds (about ten parameters), but this requires the presence of special equipment in the laboratories, highly skilled laboratory technicians and feeding specialists, and considerably increases the cost of laboratory services, although The gain from such detailing is not yet quite obvious.

In NRC technology, the generalized NSO parameter is not a laboratory-measurable parameter. The index of the NSO is estimated by calculation from the expression describing the dry matter composition of the feed

MV = MAC + Crude protein NSI + + Fat + Zola - NDKSP

Here, the CEDAW is a crude protein contained in the NIR, already taken into account in the meaning of Crude Protein as a whole. To avoid re-counting, it is subtracted from the sum of all the constituents of the dry matter.


The material presented here does not pretend to the completeness and accuracy of the wording, but rather the review of foreign and domestic publications devoted to the evaluation of carbohydrates in balancing rations of cattle.

Many concepts are presented in a simplified form in order to give the opportunity to formulate basic ideas about the structure of carbohydrates for those who get acquainted with this topic for the first time.

A source:krsaksoft