Milk component strategies
Commercial dairy herds are increasing both in profitable milk components and in overall yields. Does this mean cows should be challenged with more nutrient-rich diets to determine their productivity per unit of energy?
Mike Van Amburgh with the Department of Animal Science at Cornell University explored the topic as he presented “Feeding for High Components: Why Milk Fat & Not More Milk Protein” at the recent Herd Health & Nutrition Conference hosted by Cornell PRO-DAIRY and Northeast Agribusiness & Feed Alliance.
The term “nitrogen efficiency” is one that Van Amburgh wants to forget.
“We can make them efficient on nitrogen by making them deficient,” he said. “We can’t get first or second lactation cows to do this.”
The problem lies in generating a big response in the cow’s butterfat, but not in protein.
“In herds that achieve these outcomes, there are several consistent factors: good protocols and adherence to them – all employees are trained and retrained; cows are comfortable; stalls are managed and barns are not overcrowded; plenty of fresh, clean water; at least 12 hours per day of lying time and upwards to 13 to 14 hours; there’s a similar calf management plan; heifers calve at tight intervals of 22 to 23 months, plus or minus a month; higher quality and digestibility of forages and good inventory; and willingness to invest in amino acid balancing.”
Van Amburgh noted that world-record producing cows can make more than 74,000 lbs. of milk, which means the genetic potential exceeds 149,000 lbs.
The breeding value of milk and fat yield has been increasing for decades, along with the breeding value of protein yield. To illustrate his point, Van Amburgh noted that in a study of a 4,000-head herd in northern New York, the high genomic portion of the herd fed a similar diet to a low genetic herd yielded an average of 88 lbs. more milk, 5.6% more fat and 3.6% more protein. In a 1,700-head herd in central New York, the high group yielded more than 72 kg of energy-corrected milk.
By meetings the cows’ requirements, farmers can improve the animals’ energetic efficiency and milk component yields. Essential amino acids (EAAs) may play a role. Van Amburgh said little research exists regarding lysine requirements for bovines, so he referenced lactating sow research, noting that the lysine requirement increases by 0.47 grams/day or 2% of the current average requirement level for each year.
“We estimated the current values in 2014,” he said. “Thus, we have 11 years of progress to account for. Using the lactating sow as a model, that means a 24.4% increase in lysine.”
Fixing the ratio between lysine and the rest of the EAAs can have positive results. Feeding cows like they’re low producers curtails their full genetic potential for milk production. Van Amburgh likened a herd’s nutritional requirements to a conveyor belt of milk component production, with empty boxes for amino acids, ATP, carbon sources, reducing equivalence and glucose. If the cows have all they need, they produce milk rich in lactose, fat and protein without compromising their condition.
“If we don’t fill these boxes, the machine is not efficient,” he said.
Optimum supply of each EAA relative to metabolizable energy can help farmers address the needs of today’s dairy cows. But many nutritionists and farmers base their feeding programs on the net energy system developed in the 1960s and ‘70s.
“The cows were 1,200 pounds, round-boned – they weren’t today’s dairy cows,” Van Amburgh said.
The current energy system “is not adequate to identify the opportunity of meeting the non-energy nutrient requirements because the energy system doesn’t know what to do with the components,” he added. “The current system does not capture the energy excretion because it is likely a change in energetic efficiency that requires re-evaluation in chambers.”
He encourages farmers to “think about looking at energy-corrected diets to capture the improved efficiency effect of today’s cows.”
