Combine alfalfa and corn silage

Just as roast beef and mashed potatoes are a natural combination on the plate, corn silage and alfalfa come together in most lactating dairy cow rations. What can vary in these rations is the ratio of corn silage to alfalfa.

A clear trend over the past 20 years has been towards growing and feeding more corn silage versus alfalfa. Indeed, some nutritionists have opted for rations containing from zero to 20% of the forage dry matter fed being alfalfa.

“With economic, environmental and even social considerations encouraging the use of high fiber and forage diets, we may need to revisit how we use alfalfa in ration formulations,” notes nutrition researcher Rick Grant. dairywoman and president of the Miner Research Institute in Chazy, NY “Alfalfa has compelling benefits for soil health, nitrogen fixation, and sustainability of forage systems.”

Grant says corn silage and alfalfa are excellent complementary forages. Alfalfa’s fiber characteristics, high crude protein content, solubility, and higher lysine content correlate well with the high fermentable starch content of corn silage. “The net result of an optimal combination of these two forages should have a positive effect on rumen microbial protein synthesis and solids-corrected milk production,” Grant wrote in a recent issue of Miner Research Institute’s. Farm report newsletter.

Grant reports that he and his team recently completed a study to identify the optimal ratio of corn silage to alfalfa in the diet of lactating dairy cows. They wanted to determine if there was a benefit to feeding more alfalfa.

The researchers used 105 highly productive cows and fed them one of five different rations containing 62% forage in dry matter. Forage consisted of high quality chopped alfalfa hay containing 21.7% crude protein (CP) and 34% neutral detergent fiber (aNDFom) as well as corn silage at 9% CP and 37.4 % of aNDFom. The rations varied in their corn silage to alfalfa ratio distributed as follows: 10:90, 30:70, 50:50, 70:30 and 90:10 on a dry matter basis.

Chopped alfalfa hay was used in place of haylage to maintain consistent quality over the four-week feeding period. Grant notes that previous research has shown that feeding alfalfa hay or silage results in the same milk production responses.

The total mixed rations had a dry matter of 60% or less with some water added to the higher hay rations. Diets with higher hay content also had smaller particle size given the fragmentation of alfalfa when chopped. Although all diets were expected to provide similar levels of metabolizable protein, the diet highest in alfalfa provided approximately 150 grams more per day than the diet highest in corn silage.

The cow’s response

Regardless of diet, all cows consumed an average of 59 pounds of dry matter and 106 pounds of energy-corrected milk.

Table 1. Milk production response to various alfalfa/corn silage ratios

“Seeing this same high production over a wide range of alfalfa-to-corn silage ratios gives us great latitude in how much alfalfa can be fed versus corn silage,” Grant surmised.

Looking at milk components, Grant determined that the 30:70 and 50:50 diets of alfalfa and corn silage produced the greatest production of actual milk protein and slightly higher de novo fatty acid content in milk fat. Milk urea nitrogen (MUN) content was also lowest with the 30:70 diet.

Table 2. Response of milk components to various alfalfa/corn silage ratios

“The milk composition results suggest to us that an optimal ratio of alfalfa to corn silage, under our ration formulation conditions, was about 30:70 to about 50:50,” Grant concludes.

Based on the results of this research, the respected dairy nutritionist offers the following take home messages:

1. Alfalfa has substantial agronomic benefits.

2. This research shows that you can feed up to 90% forage as alfalfa with corn silage in 62% forage diets.

3. Milk components appear to be optimized between alfalfa/corn silage ratios of 30:70 and 50:50.

4. Sustainable dairy-forage programs could include higher alfalfa to corn silage ratios than those commonly used in the dairy industry today.