For many dairy nutritionists and farmers, the next step to higher milk protein content is balancing amino acid levels in the herd’s rations.
When the ration’s amino acid levels are matched to the cow’s biological needs, the cow’s nutritional status improves. To achieve this goal, the ration fed typically includes a rumen-protected, metabolizable methionine. The most common result is an increase in milk protein, the best known benefit of amino acid balancing, according to Dan Luchini, Ph.D., Manager – Ruminant Products Technical Services at Adisseo.
Other benefits exist, though, he notes, such as increases in both milk volume and milk fat and a decrease in nitrogen excretion. To quantify the response to amino acid balancing in a single number, the figure for energy corrected milk (ECM) is often used.
Balancing amino acids supports more efficient nitrogen so less crude protein (CP) can be fed. Reducing crude protein helps reduce feed costs and makes room for more high-quality forage while decreasing nitrogen excretion.
In recent research, one group of cows was fed a 16.8% crude protein diet that provided an estimated 2,590 grams of metabolizable protein with a lysine to methionine ratio (Lys: Met) of 3.33. Another group of cows was fed a 15.7% crude protein diet that delivered 2,450 grams of metabolizable protein for a Lys: Met ratio of 2.98. The ration with higher crude protein contained 140 more grams of metabolizable protein, yet its amino acid levels were out of balance. Both rations delivered similar grams of metabolizable lysine. The ration with lower crude protein, however, provided six extra grams of metabolizable methionine from its 40 grams of dry MetaSmart, a rumen-protected methionine.
The cows fed the diet with the lower nitrogen load (15.7% CP) produced two extra pounds of milk with better fat and protein percent. They had a significant 3.5 lbs of extra ECM. They also had lower plasma urea nitrogen (PUN) and milk urea nitrogen (MUN) which confirm better efficiency of nitrogen utilization.
Source: Adisseo