Ruminants, like nonruminants, possess metabolic needs for amino acids for their maintenance and production. A balanced and sufficient supply of amino acids is essential to achieve efficient productivity and profitability.

The lysine challenge

Lysine is crucial for protein synthesis, growth, and lactation. Due to its relatively low concentration in most feed proteins compared to levels found in rumen bacteria, milk, and tissue proteins, its been recognized as one of the most limiting amino acids for dairy cows.

Protein typically represents about 40% of the total cost of the diet for lactating dairy cows. Of the few protein sources available to meet the necessary lysine requirements, most are expensive and/or offer an inconsistent amount of lysine that is biologically available to the cow.

Because lysine is easily degraded in the rumen by microbiota, rumen-protected (RP) amino acids have become a well-established method in maintaining high levels of milk protein production and maximizing the nitrogen-use efficiency. This paradigm shift has proven to be a catalyst for economic efficiency to improve production and dairy profitability — offering a targeted and efficient means to address the inherent limitations of conventional feeding strategies.

RP lysine products are stable in the rumen and bypass microbial degradation. They reach the abomasum and small intestine intact and are available to be absorbed. This protection creates a controlled and sustained release in the small intestine, optimizing absorption to raise metabolizable amino acid supply, which is expected to boost milk protein synthesis.

The primary economic benefit of RP lysine supplementation lies in its positive impact on milk production because of this upsurge in milk protein synthesis. The economic advantage is then two-fold: greater milk output per cow and an improved protein-to-energy ratio, optimizing overall feed utilization efficiency. A recent meta-analysis showed that elevating the supply of intestinally available RP lysine in early lactating cows resulted in a linear increase in milk production as well as energy-corrected milk (ECM) and feed efficiency.

The effects of supplementing RP lysine extend to the enhancement of milk composition. It has been shown that cows also produce more butterfat, indicating a potential impact of amino acids on fatty acid synthesis.

Beyond production metrics, RP lysine supplementation has been associated with improved overall cow health and reproductive performance. The optimization of protein synthesis has downstream effects on metabolic pathways, positively influencing fertility, immune function, longevity, and even calf health. Reduced metabolic disorders and enhanced reproductive efficiency contribute to further economic gains through lower veterinary costs and improved herd sustainability. A study published in 2021 showed that metabolizable lysine given to prepartum dairy cows had positive effects on offspring performance, with the major result being a greater average daily gain for calves during the preweaning phase (6 to 8 weeks of age).

Finally, the strategic use of RP lysine can allow for the partial replacement of blood meal or protein feeds with cheaper alternatives — a great cost-saving advantage. This precision in amino acid delivery allows for a reduction in overall crude protein content in the diet while maintaining or enhancing milk production. The consequent decline in the reliance on high protein and/or high variability in nutritional composition feeds translates into substantial cost savings for dairy producers.