Alfalfa finds its way into a majority of U.S. dairy rations due not only to its feed attributes, but also due to its adaptability for growing and availability for purchase as a feed commodity. Compared to most grass forages at similar maturity (including the non-grain forage fraction of corn silage), dairy-quality alfalfa hay and haylage offer several potential advantages, according to Dan Wiersma, DuPont Pioneer livestock information manager:
Crude protein yields
Alfalfa offers a valuable combination of crude protein and yield. No other forage consistently delivers 20 percent crude protein while yielding 3-5 tons of dry matter per acre under good agronomic management. Results can be even higher under irrigation. This can result in 2,000 pounds of protein per acre, twice the 935 pounds from soybeans beans yielding 50 bushels per acre.
Experts suggest effective alfalfa inclusion levels can range from 25% to 75% of the forage fraction of dairy diets.
Alfalfa often has a high percentage of soluble protein and RDP than other forages and protein sources. This contributes to a high proportion of RDP. Caution: RDP can vary depending on crop maturity and storage. Cutting at earlier maturity contributes to higher RDP.
Effects of maturity
Greater maturity reduces the crude protein percentage in alfalfa and lowers the percentage of soluble protein and RDP. As the plant matures, the cell-wall matrix becomes more complex, rendering forage protein less degradable by rumen microbes. A greater percentage of the crude protein will become bypass protein. Also, maturing plants accumulate more dry matter, which dilutes the crude protein percentage in the plant.
As alfalfa matures, a decline in NDF digestibility (NDFD) is possible, increasing acid detergent fiber (ADF) and boosts lignin content. This leads to an overall reduced rate and extent of fiber digestion. These changes also limit the practical inclusion level of advancing maturity alfalfa in dairy rations, especially for high-producing cow groups.
From an agronomic standpoint, alfalfa fits nicely into rotation with other crops that need nitrogen. It can provide more nitrogen for a following crop than any other leguminous species commonly grown in the U.S. Corn following alfalfa enjoys a yield boost that exceeds the nitrogen response.
The value of alfalfa
Alfalfa can be a key forage component in successful dairy diets. Inclusion levels can vary widely depending on availability, forage quality, commodity pricing and overall fit with other forages and feedstuffs in the diet. High digestibility and relatively rapid ruminal passage of dairy-quality alfalfa permit high inclusion levels in diets, including high producing cow groups. Dairies may need to adjust rations to manage RDP, which can vary widely.
Corn silage and alfalfa may work well together in dairy diets. Alfalfa's high crude protein compliments the high starch content of corn silage. If kernels in corn silage are processed well, the high rumen availability of this source of starch can augment rumen microbial RDP utilization. Rotating alfalfa with corn can be efficient and profitable, especially on farms with sufficient land to grow the majority of their own forage.
This article was originally published in the February 2015 issue of Progressive Dairyman, and is reproduced with their permission.