Blending alfalfa, corn silage in rations

WISCONSIN DELLS, Wis. — When it comes to optimizing the performance of forages in dairy rations, alfalfa and corn silage have a symbiotic relationship according to Dr. Luiz Ferraretto, a ruminant nutrition specialist with the University of Wisconsin-Madison.

“Alfalfa is such a good match to corn silage and so important to dairy diets,” Ferraretto said.

Ferraretto presentated on the importance of high-quality forages in dairy diets at the Midwest Forage Association Symposium Feb. 19 in Wisconsin Dells.

Ferraretto said he first learned to formulate dairy diets using corn silage as the only forage source. He said adding alfalfa into the mix was a difference-maker.

“There are a lot of other nutrients we have to consider, things we can use to formulate diets, but there is nothing we can do if we don’t have very good forage digestibility,” Ferraretto said. “Whether you are talking about alfalfa or corn silage, at the end of the day, our goal is to make sure we have very good forage neutral detergent fiber digestibility. That is what actually drives performance in dairy cows.”

Ferraretto said forage quality and efficient feeding behavior go hand-in-hand.

“We care a lot about intake and production numbers, but feeding behavior is something we overlook,” Ferraretto said.

Ferraretto discussed a study of diets low in digestible fiber and high in digestible fiber, comparing sorghum-based diets with conventional corn silage-based diets. Cows consuming the lower digestibility diet had an intake of 85%-95% of those fed the diet that was more easily digested.

“What was really shocking was that those cows took between 6%-20% more time to eat 5%-15% less feed,” Ferraretto said. “That cow is very likely sorting. It is a major issue. As a nutritionist, if that cow is sorting my diet, (that diet) doesn’t mean anything. She is eating something else, or she is probably taking longer to masticate, because it has lower digestibility.”

Ferraretto said sorting behavior impacts more than milk production.

“There is a health component, too,” Ferraretto said. “Every minute that this cow is spending extra at the feed bunk, she is not resting or, more importantly, ruminating while resting, which I think is a metric we should be using more.”

Corn silage and alfalfa are a perfect match in dairy rations, Ferraretto said.

“Alfalfa has much higher numbers for crude protein compared to corn silage, while corn silage has more starch,” Ferraretto said. “Those match quite well in the rumen of a dairy cow. We need both. The synchronization of those makes sure the cow digests them together to create microbial proteins in the rumen. That helps a lot with milk production, milk protein production and so on.”

Amounts of alfalfa used in rations have decreased over the years, Ferraretto said.

“The number of acres of alfalfa harvested over the years has been declining in the U.S.,” Ferraretto said. “Herd sizes continue to increase, but not necessarily land availability for forage production. Whenever we don’t have enough land, we plant something that produces more, or you buy forage. That is part of the reason why corn silage continues to increase in diets, while alfalfa decreases. It’s not that people don’t want to use alfalfa, it’s just that it’s getting harder.”

Another downside to alfalfa is the lack of consistency that comes from having multiple cuts per year, creating variability in the nutrient value of the feed stuff.

“We need the combination of (quickly) degradable carbohydrates and slowly degradable carbohydrates,” Ferraretto said. “The combination of alfalfa and corn silage helps with that.”

A study that evaluated rations ranging from 90% alfalfa and 10% corn silage to the converse of 90% corn silage and 10% alfalfa showed the ratio of corn silage to alfalfa does not significantly affect the general outcome, Ferraretto said.

“Milk production was the same; efficiency was the same,” Ferraretto said. “However, it was found that when we have between 30%-50% of the forage being alfalfa, those cows produced more protein and more of the fatty acids, which are the fat truly produced by the mammary gland.”

Particle size is another reason to include alfalfa in dairy rations, Ferraretto said, as the generally larger particle size of corn silage leads to lower intake and decreased production because cows spend more time eating less.

“Alfalfa is typically much more difficult for cows to sort, with the exception of very dry, very long particle-size hay,” Ferraretto said. “Alfalfa allows you to have shorter-size corn silage and still have good, effective fiber.”

Ferraretto said producers should be vigilant in watching for signs of clostridia when storing and using alfalfa haylage.

“Clostridia is a nightmare; corn silage has no clostridia, but with haylage, it isn’t so hard to happen,” Ferraretto said. “It’s wet, has less sugar and a lot of protein, which buffers fermentation. It also has more soil contamination. I think we should pay more attention to soil contamination than fermentation with alfalfa.”

Overall, Ferraretto said he believes using alfalfa in tandem with corn silage is a positive venture.

“Alfalfa has a lot of economic benefits,” Ferraretto said. “Feeding alfalfa makes corn silage better. We want to keep increasing forages in the diet to the extent we are able to.”