Benefits & Strategies Of Lysine Amino Acid Nutrition

The benefits of AA balancing, with the focus being almost entirely on lysine (Lys) and methionine (Met) thus far, are well known and have been summarized. These benefits include reducing the risk of cows experiencing an AA deficiency, optimizing transition cow health, increasing milk and milk component yields, and feeding less rumen-undegradable protein (RUP) to post-transition cows.

The benefits of AA balancing are clearly most noticeable in transition and early lactation cows (Schwab, 2012, Osorio et al., 2014); however, benefits of reduced feeding of RUP and milk protein concentrations exist throughout the rest of the lactation (figure 1) as it will be discussed now.

Amino acids four key roles in the cow: immunity, efficiency, liver, and udder

Figure 1: Four key roles of amino acids in the cow.



The cow absorbs and uses individual amino acids rather than protein. Feeding less RUP not only decreases feed costs but it also allows for increased carbohydrate feeding. The clearest consequence in the carbohydrate feeding is increased synthesis of microbial protein, a protein of high quality, and increased synthesis of volatile fatty acids, important substrates for lactose and fat synthesis.

Therefore supplementation with rumen-protected amino acids that are limiting may improve protein efficiency in dairy cow diets in two ways.

  1. On Top: The profitable positioning is an “on top” application. In this situation, the nutritionist only supplies the specific needed amount of Lys and/or Met to the actual diet. This allows in most cases a significant increase in milk protein content and a subsequent milk value increase. It requires a proper management of rumen function, a control of by-pass protein and a minimum of digestible Lys (6.8% LysDi / PDIE) (INRA, 2010). In this way, the metabolizable protein currently supply to the cow will be better used improving protein efficiency.
  2. Reformulation: Following Kemin’s commitment for efficient farming, Kemin has developed a specific approach in order to use amino acid nutrition as a way to increase technical and economic efficiency. This approach is based on the belief that “more is no longer better” or “better can be cheaper”! The improvement in metabolisable protein utilization thanks to better amino acid balance (supply) is used in order to get the same performance, at reduced protein content in the complete diet. The formulation targets are to approach ideal amino acids profile, reducing “un-used” non-limiting amino acids and increasing limiting amino acid (lysine and methionine particularly).

Liver Function And Immunity

Amino acid balancing can have profound effects in early lactation cows. Experiments continue to show the importance of adequate Met supplementation of transition cows for a proper liver function.

When an excess of AA is supplied to the cow due to an oversupply or an unbalanced diet, AA are removed from the system as they cannot be stored. The process of deamination of amino acids takes place in the liver resulting in the presence of ammonia. The conversion of ammonia to urea, also takes place in the liver. Ammonia is very toxic and if not rapidly and efficiently removed from the circulation, will result in central nervous system disease.

The use of rumen-protected AA improves, as mentioned before, the protein efficiency and therefore lowers the AA burden in the animal.


Nutrition management may be an important means to improve dairy cow reproductive performance. It has been shown that Blood Urea Nitrogen concentration (BUN) is a sensitive indicator of the balance between amount and availability of digestible crude protein and energy fed to ruminants and BUN helps measure efficiency of protein utilization. Several studies reported the negative effects of blood or milk urea nitrogen on reproductive performance in dairy cows and suggested that overfeeding CP caused reproductive stress.

Improving the efficiency of protein utilization with any of the different feeding strategies (see above) of a proper AA balanced diet, may help to reduce the BUN and therefor have a positive impact on reproduction.


SmartMILK: Balancing for AA has, without question, been a contributing factor to higher milk yields, higher milk component levels, and greater herd profitability for many dairy producers.


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