ISSUE FOCUS 50 FEED & ADDITIVE MAGAZINE January 2026 tein. If the rest of the dietary pieces are readily available and fit properly, the cow completes the puzzle efficiently. If pieces are missing or there are too many, energy will be diverted from milk production to managing the imbalance, either by compensating or disposing of the excess. Every gram of excess protein that a cow doesn’t use is a gram she must eliminate. That disposal costs energy which could otherwise be used to support milk production. In one beef cattle study, feeding excess protein from corn byproducts (poorly balanced proteins) increased maintenance energy use by more than 5%.1 This energy was spent breaking down the excess protein, converting it into urea via the liver and then sending the urea to the kidneys to be excreted. Another study determined that excess dietary protein directly impacts milk gross energy output, which means the disposal of any protein overage has a direct effect on milk yield.2 99.7 31.4 68.4 66.6 113.1 75.9 59.4 81.8 25.4 58.6 64.1 85.1 68.5 56.4 17.9 6 9.8 2.5 28 7.4 3 17.9 8.7 16.9 17.9 34.8 25.6 25.2 0 2.7 7.1 15.4 6.8 18.2 22.2 72.4 17.9 13.1 21.5 20.9 74 32.2 28.6 0 7.1 11.7 18.4 46 24.8 25.6 133.6 26.6 6 16.7 20.6 33.4 20.6 21.4 8.7 0 6.9 18.1 5.4 13.2 18.4 70.7 21.5 8 17.5 15.3 28 20.4 15.6 3.6 2 7.7 12.8 0 13 12.6 51.7 28.7 10.5 16.1 15.4 28 18.9 14.4 10.8 4.5 6.3 12.9 0 11.5 11.4 57.4 Amount, g Lysine Methionine Threonine Isoleucine Leucine Valine Phenylalanine Overage Lysine Methionine Threonine Isoleucine Leucine Valine Phenylalanine Total Amino Acid Needs Deficit Barley Corn Microbial supply Soybean meal Canola meal Fishmeal Table 1. Calculating the ability of feed ingredients to meet the demands for milk production3
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