February 01, 2023

Set a goal for herd milk fat levels

UNIVERSITY PARK, Pa. — Examining their milk check can help dairymen decide where to focus feeding strategies.

“Look at what is paying the bills and for most that’s going to be the fat and protein yield,” said Kevin Harvatine, professor of nutritional physiology at Penn State University.

“I want to be above average in fat and protein because if we’re managing correctly we should be able to have maximal yield in a way that’s more profitable,” said Harvatine during a webinar hosted by Hoard’s Dairyman. “And we’re not making any more lactose or trucking any more water than what we have to.”

For example, the professor said, a 0.1 unit increase in fat or protein at $2.40 per pound on an 80-pound herd is 20 cents per cow per day.

“That’s $72 per year and that will change depending on the value for fat or protein,” he said. “Take your numbers and calculate how much an increase in production will return to you in value.”

If the high fat percent comes a cost to production, Harvatine said, that may not be a good strategy.

“A 0.1 unit change in milk components is equal to a little over one pound of milk,” he said. “When we look to increase fat and protein percents, we can’t hurt milk yield very much or we’re not going to have net benefits.”

The first step for dairymen to maximize the milk fat yield in their herds is to set a goal.

“Take into account the seasonal pattern,” Harvatine said. “The highest milk fat and protein is on Jan. 1 and the lowest is July 1.”

He thinks this rhythm is from the cows responding to changes in day length.

“Don’t expect the same fat on Jan. 1 and July 1,” he said. “We should be changing our goal across the year.”

There is also a seasonal rhythm for milk yield.

“But it’s a different timing because milk yield peaks late March to early April and the low point is in September,” Harvatine said. “So, we want to manage both of those.”

Mixing the feed correctly and delivering it so there is feed available all the time is important.

“If cows are without feed six hours a day and really hungry when they come to the bunk, they’re going to eat a lot of feed and that’s going to throw off that rumen,” Harvatine said. “We need to manage the feed to make sure cows are eating evenly across the day.”

Time of day may have an impact on milk fat.

“You can have 0.6 to 0.8 difference in milk fat concentration depending on milking intervals and feeding times,” Harvatine said. “And peak cows make less milk fat and protein than later lactation cows.”

Milk fat concentrations from 1960 to 2010 were consistently at 3.65 to 3.7, the professor said.

“But since 2010, the milk fat has been on a linear increase, so you should have a different goal for milk fat today than you did 10 years ago,” Harvatine said.

“The genetic potential for milk fat percent has increased 0.17 units in 10 years and milk fat yield has increase 106 pounds over that period,” he said.

Milk fat depression is a common cause of decreases in milk fat, Harvatine said.

“If you have a cow that changes over 0.3 percentage units or a herd that changes over 0.3 percentage units, it is likely diet-induced milk fat depression,” he said. “By adding a fat supplement, you can increase milk fat 0.1, 0.2 or 0.3, but beyond that changes will be from milk fat depression.”

When dairymen start making changes, they should see things moving in the right direction in seven to 10 days.

“If you don’t, you either did not pick the right thing or you did not change it enough,” Harvatine said. “You don’t have to wait a month.”

Although dairymen can’t eliminate the risk factors that cause milk fat depression, the professor said, they can manage the risk.

“We don’t want cows select feeding,” he said.

Silage fermentation and quality is also important.

“High yeast count forages will drop milk fat,” Harvatine said. “I see more issues with high corn silage diets than high haylage diets.”

High producing cows eat more feed.

“That turns up the rate of passage in the rumen, so we see more problems with high producing cows,” Harvatine said.

There is a difference in feeding cottonseed versus distillers grains.

“Distillers grains have 12% fat and the oil is in the solubles,” Harvatine said. “It’s like feeding a free oil because it is available very rapidly in the rumen.”

Cottonseed has almost 20% fat, but the fatty acid is within the whole cottonseed.

“The cottonseed stays in the rumen so long that it doesn’t cause a huge disruption,” Harvatine said. “By feeding fat we can increase the energy density, support milk yield and body weight gain without causing acidosis.”

He advises dairymen to consider the variation in moisture of cottonseed when adding it to rations.

“It is not as variable as corn silage, but it is something to keep an eye on,” he said.

The moisture amount will be more variable coming from the gin in the fall.

“It should be more consistent coming out of storage,” Harvatine said. “Make sure you use the right number so the right diet is getting in front of the cows.”

Martha Blum

Martha Blum

Field Editor