Introduction
India ranks first in milk production and by the year 2022 it targets to achieve 172 MMT milk production at an annual growth rate of 4 percent. Protein is first limiting nutrient in cattle& 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.
Three goals in balancing dairy rations with Amino acids
- Rumen Degradable Protein (RDP) requirement: Maximum carbohydrate digestion and synthesis of microbial protein.
- 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).
- 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:
- Microbial protein (50-60%)
- Rumen undegradable protein(RUP) (30-40%)
- 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
- Establishment of optimal concentrations of the most limiting amino acids(AA) (lysine and methionine) in Metabolizable protein.
- For Metabolizable protein(MP) calculation following parameters are required:
- Body weight in Kg
- Milk yield in Kg/day
- Dry matter intake in kg/day
- Milk protein yield in gram/day
- After Metabolizable protein calculation actual lysine and methionine requirement are calculated as per NRC recommendations.
- Lysine requirement -7.2% of MP (Metabolizable protein calculated)
- Methionine requirement-2.4% of MP (Metabolizable protein calculated)
- 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
- Reducing the risk of an Amino Acid deficiency (Not the crude protein but the amino acids are required nutrients for dairy cows).
- 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.
- 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.
- 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.
- 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.
- Ratio of 3:1 rumen protected lysine and methionine usage has great impact on feed formulation and diet plan.
- Balancing diet with rumen protected methionine and lysine equally plays critical role in buffalo as well cattle nutrition (improvement in SNF of milk).
- For milk products like chenna/paneer, khoa and dried whey, rumen protected methionine plays vital role.
Conclusions
1. 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.
References are available upon request.
by Dr. Manish Pathak, Kemin Industries South Asia Pvt Ltd
