ISSUE FOCUS FEED & ADDITIVE MAGAZINE April 2025 35 Cows don’t need protein as such—they need amino acids, the building blocks of proteins. Traditionally, we’ve overfed crude protein to meet these needs, a cheap and cheerful approach when nitrogen waste wasn’t a worry. Times have changed. Protein quality, price swings, and environmental pressures now loom large. Enter rumen-protected amino acids (RPAAs). By targeting amino acid supply, we can boost yields of milk, protein, and fat—ultimately lifting energy-corrected milk or solids—while cutting waste and costs and improving farm profitability. Modern rationing systems, like the Cornell Net Carbohydrate and Protein System (CNCPS), have shifted from crude protein to metabolizable protein, factoring in amino acid needs per unit of energy. This leap forward lets us tailor rations to a cow’s genetic potential, reduce cost, or optimise milk contracts. Plus, there’s a bonus: Balanced amino acids can improve health and fertility. WHAT COWS REALLY NEED Put simply, cows don’t need protein in their diet— they need amino acids to produce milk and body proteins. Feed them protein, and much of it breaks down in the rumen into nitrogen and amino acids, reforming as microbial protein. This microbial protein, the cheapest way to deliver amino acids, then flows to the hindgut for absorption by the cow. We maximise it by syncing energy and protein in the rumen. Add in bypass protein—stuff that escapes rumen fermentation—and you’ve got the cow’s metabolizable protein and amino acid supply sorted. But here’s the challenge: If an amino acid runs short, performance dips. Cows redirect amino acids from immunity, fertility, or milk protein to keep production humming, until output eventually stalls. In most European diets, methionine is first limiting —95% are deficient—followed by lysine. STRATEGIES FOR USING RUMEN- PROTECTED AMINO ACIDS: SUBSTITUTION OR PARTIAL REPLACEMENT Balance ration to increase MP-Lysine and MP-Methionine Perhaps the most versatile and effective way to use rumen-protected amino acids (RPAAs) in dairy rations is to substitute or partially replace feedstuffs with lower levels of lysine and methionine with RPAAs, which offer higher concentrations of these essential amino acids. The benefits are numerous: • Potentially lower ration costs, • Space created for more energy or fibre,
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