Nutrition affects milk components
What you feed the herd affects both herd health and milk composition. Kevin Harvatine, Ph.D., professor of nutritional physiology and chair in Agricultural Sciences at Penn State, presented “Fatty Acids & Milk Components: Optimizing Milkfat Yield” as part of the recent Herd Health & Nutrition Conference hosted by Cornell PRO-DAIRY and Northeast Agribusiness & Feed Alliance.
“As soon as protein is a penny more than fat, no one cares about fat,” Harvatine said. “We should care about both for maximum profit on the farm.”
Milkfat and the protein yield are the drivers of the income part of income-over-feed cost (IOFC). Many factors determine milkfat concentrations and yield: decreased milk by fat depression; increase by additional substrate; and other influences like cow genetics, parity, milk flow and stage of lactation.
“Things like the season are really important,” Harvatine said.
Milkfat concentration has been increasing since 2010, largely from breeding efforts.
“We’re gaining genetic potential from that cow,” Harvatine said. “Can we breed ourselves out of this? It’s going to be hard to increase the protein-to-fat ratio because they are positively correlated. There are no high protein and lower fat cows to select. We’re in a little bit of a biological quagmire.”
Making the right short- and long-term decisions can maximize IOFC today and in the future. Short-term decisions include adapting to market conditions such as real IOFC and analyzing if the farm’s management is as good as it can be that day.
Long-term decisions include predicting markets for feed, milk and labor, managing genetics and facilities and improving expertise, consistency and farm management.
“How do we look at things independent of the market?” Harvatine said. “Ask, ‘Am I as good as I can be today?’ You also need to think where will the market be three or five years from now.”
The milk check is among the influences on immediate decisions as cashflow is king, along with the real IOFC. But long-term factors to monitor include the fat and protein yield, along with the cost of energy-corrected milk (ECM) and money-corrected milk (MCM).
Harvatine said a simple approach for long-term goals is to monitor fat and protein yield while beating average percents.
“If you are below average percents, you have opportunity to do better,” he said. “Do you have some milkfat depression?”
He believes that ECM, fat-corrected milk and fat and protein-corrected milk are all standardizing on an energy basis.
“They’re all the same to standardize milk to energy value, not component yield,” Harvatine said. (The standard equation is to correct to 3.5% fat and 3.2% protein.)
He urged farmers to “view variation in standard concentrations – true vs. crude protein and assumptions on energy values. It is not standardizing to equal fat and protein yield.”
Further, he believes producers overuse ECM. “Unless milk is a biofuel, it does not make sense for farm goals to be based on energy,” Harvatine said. “Our goal is to convert feed into money, so we should be benchmarking to what is valued in the market.”
The five-year average values fat at $2.80, protein at $2.36 and other solids at 0.327.
“We overvalue fat by 60% compared to protein,” Harvatine said. “The market values lactose at 70% of protein when paid at 14%.”
Since nutritionists monitor intake and digestive efficiency, Harvatine proposed using nutritional efficiency as part of the equation; however, he said it’s not well-linked with income in either the short- or long-term.
“The old standard composition of 3.5% fat makes everyone above average and we all look like heroes,” Harvatine said. “It’s a little bit of fooling ourselves. It is 1.6 times more responsive than the changes in milkfat than protein. We can feed and manage for milkfat.”
MCM is another approach. It looks at the equivalent yield of 4.3% fat and 3.3% protein milk. Developed by Dr. Greg Bethard, MCM looks at fat and protein levels and a static market value of those components.
But Harvatine said that among this method’s challenges are that it’s not a standard equation “because he leaves it to you as to what that static value should be,” he said.
Farmers also have to pick component values and markets differ and change so farmers can’t use one long-term equation like ECM. Harvatine added that there’s confusion as to how to use MCM, as it compares constant static value for components over time to monitor the herd and current prices to compare between cows.
“You have to use a long-term static value as markets go up and down,” Harvatine said.
Value-corrected milk (VCM) as a standardization for MCM “will be different for different classes,” Harvatine said. “You will need to update prices over time so you can just create your own version.”
He also emphasized looking at seasonal patterns between winter and summer, as they affect milk composition and thus affect goals.
Farmers need to minimize diet-induced milkfat depression to optimize milkfat. Harvatine listed as risk factors unsaturated FA, rapid rumen availability and acidosis and high diet fermentability. The level and rate of starch digestibility, slug eating and bad silage can all contribute.
“The supply of substrate for milkfat synthesis has a smaller but important impact on milkfat yield,” Harvatine said. “Cows don’t make milkfat from thin air.”
Acetate production in the rumen is needed for fat synthesis and forage digestibility, along with rumen function. Feeding supplements such as sodium acetate can help increase milkfat yield; however, “the problem is you can’t afford to feed sodium acetate, so you have to manage the rumen to make it,” Harvatine said. “It’s not just coming from fiber. We need to have a stable rumen. This is the most profitable milkfat you’ll have.”
Although all farmers want to have total milkfat increase with preformed and de novo dairy fat concentration, that’s not reality.
“What often happens is as we decrease dietary fat, it decreases de novo fatty acid,” Harvatine said. “We’re not getting a direct monetary return – though we may see an increased yield and better body fat composition.”
Once the cow reaches her maximum capacity for de novo synthesis, “you will start to lose milkfat yield,” Harvatine said. “We have to be careful about where we’re starting at.”
His recommendation is to think about all the sources of fat in the animals’ diet, looking at corn silage variation and including oleic acid soybeans. In his research, adding roasted soybeans from 5% to 10% in the higher-producing cows increased milkfat. Increasing roasted high oleic acid soybeans tended to linearly increase milkfat in multiparous cows in their second experiment.
“As we fed more fat, they decrease de novo,” Harvatine said. “They were doing pretty well. High oleic soybeans can increase, decrease or not change milkfat yield.”
It decreased milkfat by milkfat depression. If unsaturated fatty acid is increased too much, it can cause issues with fermentability and acidosis. High oleic soybeans can increase milkfat by additional substrate. The diet was too low in fat and the cow was not able to make up for it with de novo synthesis.
Balancing the diet to minimize milkfat depression while maximizing energy intake makes the most sense. It’s about balancing fiber, starch, sugars and more. A balanced diet provides great fiber digestibility and rumen function to maximize acetate supply. It also supplies adequate fat.
Higher milkfat yield dilutes farmers’ fixed cost. Farmers should stop when the energy value falls below feed costs. Decreasing dietary fat may hurt milk flow, body composition score and reproduction.
Getting the fundamentals right includes accurately setting goals across the year; providing great forage and rumen fermentation to get the acetate needed for de novo synthesis; minimizing milkfat depression; and balancing dietary fatty acids based on goals and return.
