Nutrient requirements – amino acids
For several decades, researchers have shown that animals need amino acids to make tissue proteins, regulatory proteins, protective and secretory proteins, and that hundreds of these proteins must be made daily. It is also documented that the amino acid composition of each protein is different, and that protein production is a genetically predetermined process, and the amino acid composition of a protein is the same whenever it is made. In addition to the role of amino acids in the construction of proteins, they can affect every aspect of metabolism in living cells, amino acids are also important regulators of physiological and pathological processes, including immune responses, which can be used to make all compounds containing Nitrogen is used in the body including: hormones, neurotransmitters, DNA and RNA nucleotides, histamine, polyamines such as spermine and spermidine, etc. These observations point to the effective role of amino acids in the overall metabolism of the body and the importance of optimizing the nutrition of amino acids on the health, fertility and productive performance of the animal. Finally, since the nutritional importance of amino acids has been recognized, it has become clear that some amino acids cannot be made by the animal, or that their production rate is not sufficient to make proteins. These amino acids are called essential amino acids. The rest of the amino acids that are needed to make protein can be made by the animal, which are called non-essential amino acids.
The importance of amino acids balance in the diet of dairy cows
Providing a balanced profile of absorbable essential amino acids makes it possible to meet amino acid needs with less dietary protein. By selective use of protein supplements and food sources that contain higher amounts of limiting amino acids such as lysine and methionine, amino acid requirements will be met in lower concentrations of dietary protein. Diets balanced for amino acids can save dietary protein in dairy cows, but it should be noted that such a reduction is related to the RUP portion of the feed, not RDP. Diets balanced for amino acids provide an opportunity to increase the amount or A similar majority of limiting amino acids should be provided with a similar reduction or concentration of RUP.
Limiting amino acids
Lysine and methionine are often recognized as the two limiting amino acids for dairy cows in North America (2001, NRC). Various studies confirm such an observation. It should not be surprising that lysine and methionine are two limiting amino acids for lactating cows because their concentration in feed proteins is lower than the amino acids found in rumen bacteria or milk and tissue proteins.
Many nutritionists think that histidine is considered as a potential limiting amino acid. However, according to researches, histidine is considered as the first limiting amino acid when diets containing grass silage, barley and oats with or without feather powder are fed as the only source of RUP.
Based on the concentrations estimated by the National Research Council (2001 NRC) of lysine, methionine and histidine in metabolizable protein for the diets fed in these experiments with similar evaluations of the diet, the cattle increased the level of lysine and methionine in the protein. No metabolizable response was obtained, leading researchers to believe that histidine may be the third limiting amino acid in some diets. Especially if blood powder is not fed and significant amounts of corn in the diet are replaced with wheat and barley products.
Reasons for providing optimal concentrations of lysine and methionine in metabolizable protein for dairy cows
1-Decreasing the experience of the risk of lysine or methionine deficiency or both and the consequences of reduced protein production on health and fertility, growth and nitrogen balance, milk production and its components, and increasing the chance of understanding the genetic potential for production and concentrations of milk components. The current paper addresses the metabolic effects of specific amino acid deficiencies in cows, in addition to the effects on lactation performance, the reported effects of lysine and methionine deficiencies in pigs and poultry also apply to lactating cows.
2-Feeding lower RUP in the herd due to lower concentrations of methionine or methionine and lysine in RUP and MP.
3-Increasing the conversion efficiency of RUP and MP to milk protein and minimizing the loss of food nitrogen
4-Increasing income over feed cost (IOFC) and increasing herd profitability
Balancing diets for lysine and methionine
Five effective nutritional strategies for balancing rations in terms of lysine and methionine that allow the producer to realize the expected benefits of amino acid balancing:
1. The feed is a mixture of quality fodder, processed grains and by-products that will provide a combination of fermentable carbohydrates and physically effective fibers that will maximize feed consumption, milk production and microbial protein production. Microbial protein has an excellent combination of amino acids for dairy cows. The reported average concentration of lysine and methionine in real bacterial protein is 7.9% and 2.6%, respectively. Lysine and methionine concentration in fish meal, lysine concentration in blood powder, methionine concentration in oats, lysine and methionine concentration in bacteria. Rumens have the highest concentration compared to other foods.
2. Adequate feeding (not excessive) of RDP in order to meet the needs of rumen bacteria for amino acids and ammonia.
Realizing the benefits of a balanced diet in terms of fermentable carbohydrates to maximize microbial protein production requires balancing the RDP of the diet. Degradable protein in the rumen is the second major requirement of rumen microorganisms. Microorganisms needs are provided through peptides, amino acids and ammonia for microbial protein synthesis. The amount of RDP required in the diet is measured by the amounts of fermentable carbohydrates. Diet evaluation models work differently in estimating the RDP of feeds and animal needs. The NRC model usually predicts the RDP requirement to be 15-11% of the dry matter of the diet.
The final decision should be made based on the monitoring of feed intake, stool consistency, ratios of dry matter or milk nitrogen to feed, milk fat concentration and milk urea nitrogen. Usually, the desired amount of MUN is 15 dl/mg, but with careful feeding, lower amounts are not uncommon in high production cows. Decreasing feed RDP causes a decrease in carbohydrate microbial digestion, feed consumption, microbial protein synthesis, VFA production and milk production. RDP deficiency can suppress the ability of microorganisms to reproduce without affecting their ability to ferment carbohydrates. This will reduce the expected ratio of milk to feed consumption due to the reduction of microbial protein production. Also, excessive feeding of RDP causes rumen ammonia concentration and then MUN to increase. This not only leads to RDP loss, but evidence shows that it can reduce the flow of microbial protein to the small intestine.
3. Protein supplements with high lysine or a combination of a protein supplement with high lysine and a protected lysine supplement in order to achieve concentrations of lysine in MP to reach near-optimal concentrations.
Feeding foods with high protein and low lysine, such as corn gluten, are not suitable for balancing lysine. In similar methods, feeding more amounts of distilled grains (DDGS) is suitable for balancing lysine and requires feeding more RUP, which supports the production of more protein. Milk is required.
4. Supplemental feeding of protected methionine in the amounts required to reach the appropriate ratio of lysine and methionine in MP:
It is often necessary to feed a protected methionine supplement in conjunction with one or more high lysine protein supplements to achieve the appropriate lysine to methionine ratio in MP. From the use of available lysine for protein synthesis, it is important that the producer has a realistic estimate of the methionine MP provided by the fed methionine product.
Do not feed too much RUP.
There are several disadvantages to excessive RUP. 1- Reducing the concentration of lysine and methionine in MP: because most RUP supplements contain small concentrations of lysine and methionine).
2- Reduction of milk production: because the surplus of RUP usually replaces fermentable carbohydrates in the diet, which are the main substrate for the synthesis of milk compounds.
3-More expensive ration: most RUP sources are more expensive than non-fiber carbohydrates sources.
4- Increase in nitrogen in urine and feces: because the conversion of feed protein into milk protein is reduced.
Benefits of lysine and methionine balance in metabolizable protein
The balance of lysine and methionine in MP using the specified steps has led to several important advantages in both research and pharmaceutical reports. These advantages include:
1. Increasing the amount of milk produced
2. Increasing the concentration and amount of milk protein and fat
3. Reducing the need for supplements
4. More predictable changes in milk and milk protein production with changes in RUP supply
5. Reduction of nitrogen excretion per unit of produced milk or milk protein
6. Improving animal health and reproduction
7. Increasing herd profitability.
The most prominent benefits of improving lysine and methionine nutrition are the effect on lactation performance and the need for RUP supplementation. Increasing the concentration of milk components is the most noticeable and generally the fastest state that can happen. Increasing milk protein percentage is the most noticeable response to better amino acid nutrition. There are also changes in the amount of milk produced. Measuring this reaction (increasing milk) is sometimes difficult because many variables are effective in milk production, while milk protein, like the amount of milk, is not affected by many variables. Research has shown that a small percentage of cows They react to this with high production.
An increase in milk production will also occur. This response is sometimes more difficult due to the greater variability inherent in the amount of milk production compared to the concentration of milk protein, so research shows that a smaller percentage of cows respond to a higher amount of milk production. However, both responses would be expected. Preliminary research shows that milk production increases up to 0.2 kg in the early lactation period. An increase in milk production in early lactation may or may not be associated with an increase in milk protein, which depends on the level of lysine and methionine in metabolizable protein to support high production.
As mentioned, the main advantage of rations that are balanced for lysine and methionine is the reduction of the RUP level of the ration, while achieving the levels of milk components and the amount of milk production will be similar or higher than usual. Researches show that in this case it is possible to reduce the percentage of RUP up to 2% of the dry matter unit of the ration. This confirms that cows need grams of amino acids and not grams of metabolizable protein.
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