How to balance Amino acids in dairy Cow ration


Amino acids are the building blocks for protein, one of the most critical nutrients in the dairy cow ration. While the benefits of amino acid balancing can be great— increased milk and components, reduced ration costs and improved feed efficiency—the practice of balancing for these protein building blocks is often overlooked. Understanding the role amino acids play and why they are critical to the diet can help deliver a more precise ration for boosting performance and maintaining a healthy herd.


Protein is first limiting nutrient in cattle and buffalo diet because they are fed with poor quality roughages, which have low protein content and its low availability. Dietary protein requirements of cattle & buffalo depend upon the microbial population in the digestive system. Ruminal microbes alter the quality and quantity of dietary protein before it reaches in small intestine. The protein absorbed in small intestine is named as metabolizable protein. Metabolizable protein is efficiently utilized when there is a balance of amino acids required for the animal’s maintenance and milk production. Dietary protein degradation in rumen is about 60 to 70% which later forms microbial protein, due to which there is less chances of availability of original amino acid supplied through diet to animal. There is a possibility that better quality protein is degraded in rumen (chain of amino acids). Alternatively, there is other practical way to reach required level and ratio of amino acids, through dietary supplementation with rumen protected amino acids, so that any amino acids imbalance is corrected and overall utilization of dietary protein is improved. Amino acid nutrition of dairy cattle & buffaloes has received a lot of attention over the last few years. Two essential amino acids viz. lysine and methionine are limiting amino acids for milk protein and milk production. Lysine and Methionine are found in low concentration in feed protein and it cannot fulfill the animal requirement, secondly microbial protein is also insufficient to meet the animal’s requirements. So protected Lysine and Methionine are added in feed to fulfill the deficiency of these amino acids.

Rumen-degradable protein (RDP) is required by rumen microorganisms and amino acids (AA) are required by the cow.

Amino acids are the required nutrients, not Crude Protein, for the dairy cow.
Methionine and Lysine are the most limiting Amino acids, and Methionine is more essential than Lysine.

Balancing for Lysine and Methionine can provide significant opportunities for minimizing the risk of cows experiencing amino acids deficiencies and for reducing the need for protein supplements.
Increases in milk protein and fat concentrations observed with Lysine and Methionine balancing reflect an improved protein status that can have far-reaching effects on health and performance.

Balancing for amino acid has been a contributing factor to higher milk yields, higher milk component levels, and greater dairy herd profitability for many dairy producers

The shortage of feeds and forages is the major constraint in accelerating the growth of animal production in India . The feeding stuffs available are of poor quality and their nutrients are poorly utilized by animals. These feedstuffs are less digestible and contain lower quantities of energy, protein, minerals, and vitamins; consequently, the nutrients available to animals are further decreased. Crude protein (CP) content of these feedstuffs is low, and its utilization is further impeded due to non availability of rumen fermentable energy source. In ruminants, a large portion of the feed protein is transformed into microbial protein and is ultimately absorbed along with escaped feed protein. Absorbable amino acids from feed origin and microbial origin constitute metabolizable protein (MP), which is in true sense utilized by the animal for maintenance, growth, and production . For many years, CP content has been used in formulating diets for lactating dairy cows because there was little information available regarding the response of dietary protein in complex ruminal microbial environment . In addition, it was long been postulated that the high quality microbial crude protein (MCP) synthesized in the rumen would complement deficiencies in the quality of dietary protein that escaped ruminal fermentation. However, for high yielding cows, microbial protein synthesis supplies a decreasing proportion of the required protein, and significant amounts of dietary protein must escape ruminal degradation in order to meet protein needs. On the other hand, the animal scientists are under strong pressure to design ways to reduce nitrogen (N) losses from ruminants in order to prevent environmental pollution. Therefore, present research works are being diverted toward improving the efficiency of N utilization by lactating cows while maintaining optimum milk production levels. The CP system does not have a provision for differentiating between the requirements of ruminal microbes and the requirements of the host animal. Therefore, supplementations based on the CP system may result in protein deficiencies in animal. Thus, time has come to replace the current protein evaluation system to MP system, which has many advantages over the old ones. The system provides a more rational description of the energy available for microbial growth (fermentable metabolizable energy [FME]) by discounting the energy content of dietary lipids and fermentation end products . Another advantage with MP system is that it provides a framework with which the net absorption of amino acids from the small intestine can be computed in relation to the animal’s requirement . MP system is also a better predictor of milk yield in lactating animals than CP . Hence, replacement of conventional CP system with MP system seems to be a better idea to define and refine protein utilization and diet formulation as this system fits well with the biology of ruminants.

Amino Acids – The Required Nutrients

It has been known for decades that animals require AA for the synthesis of tissue, regulatory, protective and secretory proteins and that there are hundreds of these proteins that must be synthesized every day. It is also well documented that the AA composition of each protein is different, that protein synthesis is a genetically determined event, and that as a result, the AA composition of a protein is the same every time it is synthesized. Besides their role in protein synthesis, which affects virtually every aspect of metabolism in every living cell, AA are also key regulators of various pathological and physiological processes, including immune responses, as well as being used for the synthesis of all of the other N-containing compounds in the body, which includes dozens of compounds such as hormones, neurotransmitters, nucleotides (RNA and DNA), histamine, polyamines such as such as spermine and spermidine, etc.

These observations are mentioned to highlight the impact that AA have on overall body metabolism and the likely importance that optimizing AA nutrition has on health, fertility and production performance of animals. Finally, for nearly as long as the nutritive significance of AA has been recognized, it has been known that some of the AA cannot be synthesized by the animal, or synthesized fast enough, from other AA, to meet requirements for protein synthesis. These AA were termed essential AA (EAA) (Rose,1938). The remaining AA that are needed for protein synthesis but can be synthesized
by the animal were called nonessential AA.

Importance of Amino Acid Balance

What this early understanding of AA nutrition and subsequent research has indicated is that: 1) AA are the building blocks for protein synthesis, 2) the ideal profile of absorbed EAA may be different for maintenance, growth, pregnancy and milk production and that as a result, the ideal profile may be different for an animal at different stages of its life cycle or at different physiological states (e.g., high vs. low milk production), and that 3) providing a more balanced profile of absorbable EAA allows meeting AA requirements with less dietary protein. The latter point has been exploited by the swine and poultry industry. By selective use of protein supplements and feed grade sources of the most limiting AA such as Lys and Met, AA requirements are being met with lower concentrations of dietary protein.

Balancing diets for AA also has the advantage of sparing dietary protein for dairy cows, but the protein fraction that is spared is RUP, not RDP. Balancing diets for AA provides the opportunity to supply similar or greater amounts of the most limiting AA with reduced or similar concentrations of RUP. However, because microbial protein provides about 50% of the absorbed AA requirements of lactating dairy cows, there is less opportunity to spare as much as RUP in cows as total dietary protein in pigs or

Limiting Amino Acids 

Lysine and Met have been identified most frequently as the two most limiting AA for lactating dairy cows in North America (NRC, 2001). A variety of research studies continue to support these early observations (e.g., Appuhamy et al., 2011, Chen et al., 2011; Doepel and Lapierre, 2010, 2011; Noftsger and St-Pierre, 2003; Noftsger et al, 2005; Ordway et al., 2009; Socha et al., 2005; St-Pierre and Sylvester, 2005). That Lys and Met are the first two limiting AA for lactating dairy cows should not be surprising given their low concentrations in most feed proteins relative to their concentrations in rumen bacteria or in milk and tissue protein.

Many nutritionists have questioned the possibility of histidine (His) as a potential limiting AA. However, to the author’s knowledge, His has only been identified as first limiting when grass silage and barley and oat diets were fed, with or without feather meal as a sole or primary source of supplemental RUP (Kim et al., 1999, 2000, 2001a, 2001b; Huhtanen et al., 2002; Korhonen et al., 2000; Vanhatalo et al., 1999). None of these diets contained corn or corn byproducts. Based on NRC (2001) predicted
concentrations of Lys, Met, and His in MP for the diets fed in these experiments, coupled with similar evaluations of diets where cows have (or have not) responded to increased levels of Lys and Met in MP (McLaughlin, 2002), leads the author to speculate that His may become the third limiting AA in some diets, particularly where no blood meal is being fed and where barley and wheat products replace significant amounts of corn in the diet.

Reasons for Providing Lactating Dairy Cows with Optimum Concentrations of Lys and Met in MP

1. Reduce the risk of cows experiencing a Lys or Met deficiency, or both, and the resulting consequences of reduced protein synthesis on health and fertility, growth and N balance, and milk and milk component production and increase their chances of realizing their genetic potential for milk yield and component concentrations.

Current literature is limited on the metabolic effects of specific AA deficiencies in cows, over and beyond the effects on lactation performance, but it seems reasonable to think that the reported effects of Lys and Met deficiencies in pigs and chickens are also true for lactating dairy cows.

2. Take advantage of the opportunity to feed less RUP in herds where RUP is being over-fed because of low concentrations of Met, or Met and Lys, in RUP and MP.

3. Increase efficiency of conversion of RUP and MP to milk protein and minimize
wastage of dietary N.

4. Increase income-over-feed-costs and dairy herd profitability.

Balancing Diets for Lys and Met

The following five feeding strategies have been shown to be effective in balancing diets for Lys and Met, allowing producers to realize the benefits expected of balancing diets for AA.

1. Feed a mixture of high quality forages, processed grains, and byproduct feeds that will provide a blend of fermentable carbohydrates and physically effective fiber that maximizes feed intake, milk production, and yield of microbial protein. Microbial protein has an apparent excellent AA composition for lactating dairy cows. The average reported concentrations of Lys and Met in bacterial true protein of 7.9% and 2.6% exceed the optimum concentrations of 7.2-7.3% and 2.4-2.5% that were established by Rulquin et al. (1993), NRC (2001) and Doepel et al. (2004)

Other than the concentrations of both Lys and Met in fish meal, the concentration of Lys in blood meal and Met in oats, the concentrations of Lys and Met in rumen bacteria far exceed concentrations in most other feeds.

2. Feed adequate but not excessive levels of RDP to meet rumen bacterial
requirements for AA and ammonia. Realizing the benefits of feeding a balanced supply of fermentable carbohydrates on maximizing yields of microbial protein also requires balancing diets for RDP. Rumen degraded feed protein is the second largest requirement for rumen microorganisms. It supplies the microorganisms with peptides, AA, and ammonia that are needed for microbial protein synthesis. The amount of RDP required in the diet is determined by the amount of fermentable carbohydrates in the diet. Diet evaluation models differ in their estimates of RDP in feeds and animal requirements. The NRC (2001) model typically predicts RDP requirements of 10 to 11% of diet DM. Regardless of the model used, it is important to use the predicted requirements ONLY AS A GUIDE and to fine tune according to available research and animal responses. Monitor feed intake, fecal consistency, milk/feed DM and N ratios, milk fat concentrations, and milk urea N (MUN) to make the final decision. A common target value for MUN is 10 mg/dL, but values lower than this is not uncommon in high producing cows with more precise feeding.

Don’t short-change the cows on RDP…superior carbohydrate balancing can be negated with an inadequate supply of RDP. Underfeeding RDP decreases microbial digestion of carbohydrates, decreases feed intake, decreases synthesis of microbial protein, decreases production of volatile fatty acids (VFA), and decreases milk yield. A deficiency of RDP can suppress the ability of the microorganisms to reproduce without affecting their ability to ferment carbohydrates. This will can result in lower than expected milk/feed ratios because of lower than expected synthesis of microbial protein. Also, avoid over-feeding RDP to the point that rumen ammonia concentrations markedly exceed bacterial requirements and MUN become high. Not only does it result in wastage of RDP, but there is also good evidence that it decreases flows of microbial protein to the small intestine (e.g., Boucher et al., 2007; Peter Robinson, personal communication).

3. Feed high-Lys protein supplements, or a combination of high-Lys protein supplements and a rumen-protected Lys supplement, to achieve concentrations of Lys in MP that come as close as possible to meeting the optimal concentration.

Feeding low-Lys, high-protein feeds such as corn gluten meal is NOT consistent with balancing for Lys. In similar fashion, feeding larger amounts of dried distiller’s grains with solubles (DDGS) also compromises balancing for Lys and requires feeding more RUP that would otherwise be needed to realize similar yields of milk protein. There may well be times when it is economical to feed larger amounts of DDGS, but it comes at the metabolic expense of having to feed more RUP.

4. Feed a “rumen-protected” Met supplement in amounts needed to achieve the optimal ratio of Lys and Met in MP. Feeding a rumen-protected Met supplement, in conjunction with one or more of the
aforementioned high-Lys protein supplements, is almost always necessary to achieve the correct Lys/Met ratio in MP (Table 3). To achieve the desired predicted ratio of Lys to Met in MP, and to ensure full use of the available MP-Lys for protein synthesis, it is important to use a realistic estimate for the amount of MP-Met provided by the Met product that you are feeding. Over-estimating the efficacy of a RP-Met supplement usually leads to disappointing production outcomes, and more often than not, leaves the nutritionist and dairy producer believing that balancing for Lys and Met has little value.
5. Do not overfeed RUP.

There are several disadvantages to overfeeding RUP. These include: 1) lowered concentrations of Lys and Met in MP (because most sources of supplemental RUP contain low concentrations of Lys, Met or both, relative to optimal concentrations in MP. 
2) lowered milk production (because surplus RUP usually replaces fermentable carbohydrates in the diet, the primary substrates for synthesis of milk components) 
3) a more expensive diet (because most sources of supplemental RUP are more expensive than most sources of nonfiber cabohydrates) And
4) Increased urinary and fecal N (because of lowered conversions of feed protein to milk protein).

Identifying the optimum concentration of RUP in diet DM is challenging. The nutritional model that you use can be used as a guide, but it should not be used to provide the final answer. The reason is that there are too many factors that affect RUP requirements (e.g., intestinal supply of microbial protein, RUP digestibility, RUP-Lys digestibility, and concentrations of Lys and Met in MP) for current
nutritional models to adequately consider and adjust requirements for. Each of these factors can have a significant effect on how much RUP is needed. Therefore, unless you are feeding an average diet to which your model validates, it is more than likely that your model will under or over estimate RUP requirements.

While disappointing, it must be emphasized that current models do not adjust MP requirements, and thus RUP requirements, for changes in predicted concentrations of AA in MP. This is a serious deficiency and until models are designed to predict milk and milk protein yields from supplies of MP-Lys and MP-Met, just know that the MP requirement, and therefore the RUP requirement, for a given yield of milk and milk protein decreases with higher concentrations of Lys and Met in MP.

As a second step for identifying the optimum concentration of RUP in diet DM, it is suggested that insofar as feeding management allows, let the cows tell you how much they need. Don’t be surprised, as a result of balancing for Lys and Met in MP, how little RUP is actually needed in the diet. Moreover, field experience indicates that cows are more responsive to changes in diet RUP content when RUP has a good AA balance vs. when the balance is not good. This makes sense because the nutritional potency of the RUP is greater when it has a good AA balance vs. a poor AA balance.

Benefits of Balancing for Lys and Met in MP

Balancing for Lys and Met in MP, using the steps as outlined, has led to many important benefits, both in research and on-farm implementation. The benefits include:

1) increased milk yields, 2) increased concentrations and yields of milk protein and fat, 3) reduced need for supplemental RUP for similar or greater component yields, 4) more predictable changes in milk and milk protein production to changes in RUP supply, 5) reduced N excretion per unit of milk or milk protein produced, 6) improved health and reproduction, and 7) increased dairy herd profitability. That these benefits to balancing for Lys and Met in MP have been achieved supports the conclusion that while other AA may become limiting, it seldom occurs before the recommended target levels for Lys and Met are achieved.

The most understood and appreciated benefits of improved Lys and Met nutrition are affects on lactation performance and the need for supplemental RUP. Increased milk component concentrations are the most visible and generally are the quickest to occur. It is no longer uncommon to hear reports of increases in milk protein concentrations of 0.20 to 0.25 percentage units and increases in milk fat concentrations of 0.10 to 0.15 percentage units…often on less dietary RUP. This does not mean that responses of this magnitude are always observed, but what it does mean is varying degrees of Lys and Met deficiency exist among herds and that one can expect variable effects on animal performance when balancing for Lys and Met. Increases in milk protein percentages are the most visible of the responses to better AA nutrition, and when observed, it should only be considered as the “the tip of the iceberg”.

Increases in milk yield will also occur. This response is sometimes more difficult to measure because of the inherent greater variability in milk yield than milk protein concentrations on a day-to-day basis and the fact that research has shown that a smaller percentage of cows will respond with higher milk yields. Nevertheless, this is both an expected and observed response. Early studies indicated 2 to 5 lb more milk in early lactation (Garthwaite et al., 1999). More recent studies now have shown 5 to 10 lb
more milk. Increased milk yields in early lactation may or may not be accompanied by increases in milk protein percentages if levels of Lys and Met in MP are not pushed high enough. What field observations in particular have indicated is that if you see an increase in milk protein percentages, assume at least some increase in milk yield.

As mentioned earlier, a “feed advantage” to balancing for Lys and Met is the possibility for reduced RUP feeding while achieving similar or higher milk component levels and milk yields. Research and field observations alike indicate that it is no longer uncommon to see reductions in RUP of 1.0 to 2.0 percentage units of diet DM. This confirms that cows require “grams of amino acids” and not “grams of MP).

Amino Acid Requirement:

Dairy cows require amino acids to make milk and muscle protein, to make the protein in a growing fetus, and to make the proteins they need to maintain themselves (such as enzymes required to digest feeds). Each of these proteins is made up of a different profile of amino acids. For this reason, a cow will require different amounts of each of the essential amino acids depending on her stage of lactation, growth, and pregnancy.

Amino acid requirements can be expressed using either the factorial method or the ideal protein method. With the factorial method, requirements are based on the needs of the animal (for example, the amount of milk to be produced and its amino acid content) and the various efficiencies with which amino acids are absorbed and utilized. Unfortunately, these efficiencies are difficult to estimate. The mammary gland takes up more of some amino acids than it puts out in milk. With some non-essential amino acids, the mammary gland takes up fewer than are found in the milk produced. The pattern of amino acids needed for milk production is therefore different than the amino acid pattern of milk.


Amino Acid Total Uptake Mammary Output
Arginine 8.53 3.40
Histidine 3.29 2.74
Isoleucine 8.80 5.79
Leucine 13.04 9.18
Lysine 9.14 3.40
Methionine 2.82 2.71
Phenylalanine 4.51 4.75
Threonine 4.76 3.72
Valine 10.01 5.89
Evans, 1999

Body cells use active transport mechanisms to take up amino acids. There are 3 different types of transport for amino acids: neutral amino acids (threonine, leucine, valine, isoleucine, phenylalanine, methionine, cystine/cysteine, and tryptophan), basic amino acids (histidine, arginine, and lysine), and acidic amino acids. Within an amino acid type, one amino acid can compete for and inhibit the transport of another amino acid. Because of the potential negative effects of amino acids on each other, the factorial method may overestimate production responses when there is an excess of one amino acid. For example, in one study where lysine was the first-limiting amino acid and extra methionine was supplemented, milk protein production was actually reduced (Rulquin and Verite, 1993).

For this reason, the ideal protein method (ratio approach) is more commonly relied upon to balance rations for amino acids. The ideal protein method is based on research study responses to amino acids expressed as a percentage of either metabolizable protein or intestinal essential amino acids. The relationship of amino acids to each other drives the ration rather than the actual amount of individual amino acids absorbed. According to the research of Schwab at the University of New Hampshire , 5% of the intestinal essential amino acids should be methionine and 15% should be lysine. According to research from Rulquin and Verite in France , 2.5% of the metabolizable amino acids should be methionine and 7.3% should be lysine. The NRC (2001) publication summarized a large dataset and concluded that 2.2% of the metabolizable amino acids should be methionine and 7.2% should be lysine. Without supplementation of individual amino acids, it’s hard to reach these goals. According to Sniffen et al., 2001, milk protein is reduced when methionine is less than 2.1-2.2% of metabolizable amino acids and lysine is less than 6.0-6.5% of metabolizable amino acids. Sniffen et al., 2001 analyzed the results from 21 experiments that were conducted with rumen-protected lysine and methionine and a range of concentrates and forages. For milk production and milk crude protein yield, the optimum amount of methionine was 2.07% of metabolizable protein and the optimum amount of lysine was 7.04% of metabolizable protein.

Based on their modeling work, Sniffen et al., 2001 endorsed the ratio approach to amino acid balancing. However, it was recognized that the metabolizable protein requirement must still be met and that factorial supplies of individual amino acids should still exceed factorial requirements. At this time, computerized models using both the factorial approach and the ideal ratio approach for balancing amino acids should be the most effective.

Three goals in balancing dairy rations with Amino acids

1. Rumen Degradable Protein (RDP) requirement: Maximum carbohydrate digestion and synthesis of microbial protein.
2. Metabolizable Protein(MP) requirement: For maintenance, growth, optimum health and reproduction, and desired levels of milk and milk protein production with minimal intake of Rumen undegradable protein(RUP). Metabolizable protein (MP) is a much better reflection of protein supply to the cow than is Crude Protein (CP).
3. Protein and Amino acid(AA) requirements: For milk yield, protein and fat content with minimum amount of dietary crude protein (CP).
Lactating dairy cows DO NOT have a requirement for crude protein whereas, they have a requirement for amino acids (National Research Council, 2001). If dietary CP is overfed, it is wasteful, and whatever protein i.e. excess nitrogen is excreted which leads to decrease in animal performance, and increase in environmental pollution.

The Amino acids(AA) a dairy animal receives are a mixture of:

1. Microbial protein (50-60%)
2. Rumen undegradable protein(RUP) (30-40%)
3. Endogenous protein (10%)
Methionine and Lysine Requirements are expressed as % of MP(Metabolizable protein)
The concentrations of Lysine and Methionine in Metabolizable protein (MP) for maximal content of milk protein were 7.2% and 2.4%, respectively (3.0:1.0 ratio NRC recommendations) and practical recommendations of 6.6% Lysine, 2.2% Methionine.

Steps to be followed while balancing amino acids Lysine and Methionine practically in diet

1. Establishment of optimal concentrations of the most limiting amino acids(AA) (lysine and methionine) in Metabolizable protein.
2. For Metabolizable protein(MP) calculation following parameters are required:
3. Body weight in Kg
4. Milk yield in Kg/day
5. Dry matter intake in kg/day
6. Milk protein yield in gram/day
7. After Metabolizable protein calculation actual lysine and methionine requirement are calculated as per NRC recommendations.
8. Lysine requirement -7.2% of MP (Metabolizable protein calculated)
9. Methionine requirement-2.4% of MP (Metabolizable protein calculated)
10. Amino acid supply can be expressed in several ways, such as g/d, % MP, and g/Mcal ME and each have usage depending on stage of lactation cycle of the cow. 30-35 g mMet/d in the close cow, 2.6-2.8% MP-Met in the fresh cow, and 1.14 g mMet/Mcal ME for post fresh cow. For lysine target are 90-95 g mLys/d in the closeup cow, 7.0-7.2% MP-Met in the fresh cow, and 3.03 g mLys/Mcal ME for post fresh cow.

The practical benefits of balancing Amino Acid Lysine and Methionine

1. Reducing the risk of an Amino Acid deficiency (Not the crude protein but the amino acids are required nutrients for dairy cows).
2. Optimizing transition cow health, increasing milk and milk component yields, and feeding less Rumen undegradable protein(RUP) to post-transition cows. Feeding less Rumen undegradable protein(RUP)not only decreases feed costs but also allows for increased carbohydrate feeding, which leads to increased synthesis of Metabolizable Protein, a protein of high quality, and increased synthesis of volatile fatty acids, important substrates for lactose and fat synthesis.
3. Impact of balancing Lysine and Methionine in early lactation and transition cows has great result in terms of promoting high dry matter intake soon after calving, increase milk production and composition as well as improvement in embryo quality and reduction in early embryonic losses.
4. Immune status of dairy cows is also improved due to balancing amino acid lysine and methionine. Various study suggests that there is a reduction in somatic cell count and control of mastitis by usage of rumen protected Lysine and methionine.
5. Amino acid balancing helps in lowering crude protein of ration around 2% by supplementation of rumen protected amino acid and helps to obtain similar results like earlier crude protein level. Broderick and his colleagues (2008) published a study that a ration with 16.1% CP and added Rumen protected Methionine resulted in the same amount of milk as a 17.3% CP ration without RP-Met, and both rations resulted in higher milk production than an 18.3% ration.
6. Ratio of 3:1 rumen protected lysine and methionine usage has great impact on feed formulation and diet plan.
7. Balancing diet with rumen protected methionine and lysine equally plays critical role in buffalo as well cattle nutrition (improvement in SNF of milk).
8. For milk products like chenna/paneer, khoa and dried whey, rumen protected methionine plays vital role.

From the above discussions, it is clear that the dairy cow has two sets of N requirements: The N requirements of rumen microbes for optimum fermentation and the amino acids requirements of the cow. Considerable progress has been made in meeting these requirements with more accuracy. It should be made sure that the cow’s RDP requirement is met so that rumen microbes get enough amino acids and ammonia for their growth. A deficiency will suppress the growth and activity of the microbes, decrease feed intake, and decrease the efficiency of MCP. However, excessive amounts of RDP feeding should also be avoided as it decreases the efficiency of use of dietary protein for milk protein production. Overfeeding of RUP is also not desirable as it lowers the efficiency of use of MP for milk protein production. The MP feeding standards for lactating cows represents a balance between animal requirements for MP and their fulfillment by dietary sources. The dairy cattle diets should preferably include a mixture of forages, processed grains, and agro-industrial byproducts in order to provide a suitable ratio of fermentable carbohydrate and dietary fiber for maximization of feed intake, milk yield, and MP yield. Many research works have reported improved herd health, reproduction and profitability when diets were balanced with MP. Despite some drawbacks, the MP system has merit in predicting and meeting the protein requirements of dairy cattle. The use of MP system should allow producers, researchers, and nutritionists to more accurately predict the type and amount of supplements necessary to achieve and maintain predetermined performance standards. By feeding the animals with correct amount specific diet at a specific time, the cost of production could also be significantly reduced. 
Thus, balancing the protein diet of dairy animals in terms of RDP, RUP, and MP is the best possible way for efficient utilization of nutrients and for maximizing milk production

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