What additives are used in ruminant feed?
1) Yeast Culture
The main functions of yeast culture are:
① Increase dry matter intake and daily weight gain
② Improve feed digestibility and reduce digestive metabolic diseases
③ Improve milk production performance in female animals and reduce reproductive performance
④ Improve digestive health in young animals and reduce diarrhea
⑤ Improve animal immunity and alleviate inflammatory responses
⑥ Improve animal growth performance
⑦ Alleviate stress during the rearing process
⑧ Improve fur quality
⑨ Improve meat quality and reduce dripping and cooking losses
⑩ Improve the body’s nutritional metabolism and improve the air environment in livestock houses.
Yeast culture was first used as a feed additive as a protein supplement for ruminants.
Yeast culture is mainly used in ruminant and aquaculture, playing a dual role in nutrition and health care. Numerous studies at home and abroad have proven that yeast culture plays an important role in promoting animal growth, improving feed utilization, preventing diseases, improving immunity, and improving the environment. When used as a feed additive, the nutritional effect of yeast culture is mainly to optimize the nutritional value of feed. Yeast culture is a pure natural feed ingredient that can improve feed palatability and digestibility. Good palatability helps maintain a stable feed intake; good feed digestibility allows animals to absorb more nutrients to promote production performance. The reason why yeast culture shows a significant milk-enhancing effect in dairy cows is that the culture is a metabolite of yeast, which can promote rumen fermentation, causing ammonia bacteria, protein-synthesizing bacteria, and fiber bacteria to multiply and grow in large numbers, thereby improving the digestibility of crude fiber in feed and the efficiency of bacteria in synthesizing cell protein using NPN (non-protein nitrogen).
2) Enzyme Preparations for Ruminants
Most ruminant feed enzymes contain cellulase and hemicellulase, derived from cellulose and hemicellulose, the main structural polysaccharides in plants. The types of cellulase and hemicellulase vary considerably among commercial enzyme products, depending on the source organism and its growth pattern.
The application of enzyme preparations in ruminants is limited by several issues. With ongoing research and trials on enzymes for ruminants, it is certain that enzyme preparations are effective in ruminants, making the development of a comprehensive technical system for the application of ruminant enzyme preparations imperative.
The use of exogenous enzymes in ruminants involves six key technical points:
1. Synergistic effect between exogenous enzymes and rumen microbial enzymes;
2. The relationship between exogenous enzymes, microbial enzymes, and host digestive enzymes;
3. Full consideration of ruminant behavior;
4. The application pattern of exogenous enzymes should be segmented before and after rumen function establishment;
5. Minimize disruption of ruminant digestive tract metabolic function;
6. Research on the application of combined and complex enzymes.
Research on the mechanism of enzyme application in ruminants:
1. Enzymes improve feed digestibility by acting on feed before feeding.
2. Enzymes work synergistically with rumen microorganisms to indirectly stimulate digestive activity and participate in the transrumen digestion of fiber in the posterior intestinal tract.
Enzymes also have certain effects on the gastrointestinal microbiota and the ruminants themselves.
3) Rumen-protected Amino Acids (Lysine and Methionine)
Methionine is an important nutrient for ruminants. However, direct addition to the diet is rapidly degraded by rumen microorganisms, failing to meet the animal’s high-yield requirements. Therefore, rumen-protected methionine has become a research hotspot and focus.
Methionine, as a crucial limiting amino acid for ruminants, plays a significant role in maximizing animal production potential, alleviating the shortage of protein feed resources, reducing fecal and urinary nitrogen emissions, and protecting the environment. However, due to the unique digestive and metabolic pathways of ruminants, directly added crystalline methionine is rapidly degraded by rumen microorganisms (protozoa, bacteria, and fungi), losing its significant biological efficacy. Therefore, rumen-protected methionine has become a current research hotspot for ruminant nutrition, aiming to increase the number of limiting amino acids in the small intestine and bring it closer to the ideal amino acid level, thereby achieving increased production and income. In recent years, researchers have deepened their understanding of rumen-protected methionine, but many questions still warrant further investigation: First, to thoroughly study the metabolic pathways and mechanisms of methionine in animals, and to further understand its effects on ruminant nutrition, production, and immunity; second, to further optimize rumen-protected methionine technology for large-scale promotion and application, and to explore coating methods for other limiting amino acids, vitamins, and small peptide products based on this; third, to fully study the synergistic effects of adding rumen-protected methionine and rumen-protected lysine, and to determine their appropriate addition amounts and ratios for optimal results; and fourth, to actively promote the application of low-protein diets for ruminants, with rumen-protected amino acid research as the core. Lysine is an essential amino acid required by dairy cows. In the body, cattle utilize lysine for a range of functions including: maintenance, growth (in lactating heifers or primiparous cows), reproduction, lactation, and milk protein synthesis. Lysine is often a limiting amino acid, especially in diets high in corn products. With rumen-protected lysine products, it is now possible to increase lysine supply in a more targeted or purposeful manner.
Rumen-protected choline (RPC) effectively prevents the degradation of choline by rumen microorganisms, allowing choline to be released and absorbed in the ideal site—the small intestine. Numerous studies have confirmed that RPC promotes peripartum dairy cow health and improves production and reproductive performance.
When dietary protein or methionine is insufficient, choline can partially replace methionine in its function. Methionine and lysine are the most important limiting amino acids in lactating cows; adding choline can conserve methionine, allowing more methionine to be used for milk production.
With the rapid improvement of dairy farming technology in my country, the feeding and management of peripartum dairy cows is receiving increasing attention. Choline has gained widespread interest due to its unique physiological functions in peripartum dairy cows, such as preventing fatty liver and ketosis. Due to the digestive physiology of ruminants, direct addition does not achieve ideal results; rumen protection treatment is necessary.
Currently, the biggest problem with rumen-protected choline is the immature coating process. Commercially available choline chloride carriers are mainly plant-based and mineral-based, with choline chloride content mostly ranging from 50% to 60%, limiting the choline content of rumen-protected choline products. The highly hygroscopic nature of choline chloride poses significant challenges to the selection of coating processes and negatively impacts coating effectiveness. Therefore, there are currently no rumen-protected choline products on the domestic market that can be widely used in dairy production.
Increasing the choline chloride content in commercially available choline chloride products, reducing their hygroscopicity, finding suitable coating materials, and developing coating processes suitable for chlorination properties will be the focus and direction of future rumen-protected choline product development.
Rumen-protected vitamins are essential nutrients for ruminants requiring rumen protection. Vitamin deficiency or insufficiency can negatively impact ruminant production performance and disease resistance/stress tolerance.
The rumen significantly degrades multivitamins. While fat-soluble vitamin K3 and most water-soluble B vitamins can generally be synthesized in the rumen or body tissues, fat-soluble vitamins A, D3, and E must be supplemented. For high-producing dairy cows, nicotinamide and biotin supplementation are often necessary to increase milk production and prevent hoof diseases.
It is generally believed that rumen microorganisms can synthesize sufficient B vitamins for dairy cows, and the role of B vitamins in lactating cows has been overlooked. However, with significantly increased milk production and nutritional requirements in dairy cows, the B vitamins synthesized by rumen microorganisms are no longer sufficient to meet the metabolic and milk production needs of high-producing cows. Studies have shown that deficiencies in B vitamins, particularly pantothenic acid, pyridoxine, biotin, and folic acid, can limit dairy cow production performance.
Adding rumen-protected B vitamins to dairy cow feed can improve lactation efficiency, milk fat percentage, and milk protein percentage, thereby increasing milk production and improving the economic benefits of dairy farming.
6) Rumen-Passed Fat
Rumen-passed fat powder is an energy source that does not affect rumen fermentation and is easily digested, absorbed, and utilized by the rumen’s post-digestive system. Rumen-passed fat powder is not easily broken down in rumen juice and can pass through the rumen without affecting the rumen microbiota. However, in the abomasum and duodenum, it is converted into an absorbable form through chemical and enzymatic action and is ultimately absorbed in the small intestine. Numerous studies have found that the best way to improve the energy supply of ruminants by adding fat is to ensure that the fat reaches the animal’s post-digestive tract for digestion, absorption, and utilization.
Ideal characteristics of rumen-passed fat powder:
① High total energy content;
② To ensure high digestibility of added fat powder, it should typically contain more than 80% free fatty acids;
③ Too high or too low a fatty acid saturation is detrimental to fat digestibility; the ideal iodine value is between 6 and 15;
④ Rumen-passed fat should not affect feed palatability;
⑤ Easy to store and not easily spoiled, easy to handle and transport, non-corrosive, and has no adverse effects on feed.
Rumen-protected fat powders can be classified according to their different protective mechanisms, resulting in varying absorption rates. Based on this, rumen-protected fat powders can be categorized as follows:
① Coated oils, including formaldehyde-protein coated oils and blood meal coated oils;
② Saturated (hydrogenated) fats;
③ Fatty acid compounds, primarily calcium salts of fatty acids;
④ Products primarily composed of palm oil or palm oil fatty acids.
7) Anionic Salt Products
In the 1990s, nutritionists discovered that improving the acid-base balance of dairy cow diets could prevent postpartum hypocalcemia. Dietary acid-base balance is related to the anions and cations in the diet.
Elements such as sulfur, phosphorus, and chlorine in feed enter the body and are converted into acid groups such as sulfate, phosphate, and hydrochloride, respectively; elements such as sodium, potassium, calcium, and magnesium enter the body and are converted into their respective cationic bases. When the total equivalent of bases in the body is greater than the total equivalent of acid groups, the body fluids are alkaline; conversely, they are acidic. Whether a diet is alkaline or acidic largely depends on the difference between the equivalents of cations and anions.
Anionic salts have a good effect on reducing the incidence of postpartum diseases. In dairy herds with a high incidence of metabolic diseases, feeding anionic salts is a major preventive measure against puerperal fever, ketosis, retained placenta, and abomasal displacement. Even in well-managed dairy herds with a low incidence of metabolic diseases such as puerperal fever and ketosis, feeding anionic salts can prevent subacute hypocalcemia, thereby increasing milk production during lactation by 8% to 10% or more.
Feeding with anionic salts significantly improves reproductive performance, increases conception rate, shortens the non-pregnant period, and extends lifespan. Additionally, feeding with anionic salts increases milk fat percentage, reduces somatic cell count, and improves dairy quality.
8) Ammonium Chloride
Feed-grade ammonium chloride has two main applications in livestock production. Firstly, it can be used as a non-protein nitrogen feed additive for ruminants, replacing some of the biological protein in the feed. Secondly, it can be used as an acidity regulator to acidify body fluids and urine. Ammonium chloride is a strong urine acidifier and has a good preventive and therapeutic effect on phosphate urinary stones.
Ammonium chloride can also be used as a non-protein nitrogen feed additive for ruminants, but currently, the most widely used non-protein nitrogen feed in ruminant production is urea and its derivatives; research on ammonium salt feeds is relatively limited.
8) Urea-based Non-protein Nitrogen
Urea is a simple, non-protein nitrogen compound. Urea also has disadvantages and limitations in feed use, such as poor taste and the risk of urea poisoning from excessive use. To address the shortcomings and deficiencies of urea in animal feed, processes such as corn gelatinization and extrusion have been employed to eliminate the ammonia-alkali odor of urea and to achieve a certain degree of slow release, thereby reducing the risk of urea poisoning.
1. Enhances animal appetite, increases feed intake, and accelerates animal growth.
2. Masks unpleasant odors and improves feed palatability.
3. Alleviates stress, maintains feed intake, and promotes disease prevention.
4. Stimulates digestive juice secretion and improves nutrient digestibility and absorption.
1. Improves feed palatability. By extending and prolonging sweetness and suppressing off-odors, it improves overall feed palatability, making the feed taste better.
2. Effectively masks or reduces unpleasant odors in poorly palatable feeds (such as certain proteins, vitamins, and antibiotics). Increases feed intake in animals under stress.
3. Shortens feeding cycles.
