Dairy producers often receive conflicting information on the best forage system for their operation.

For example, a nutritionist typically will make recommendations that will provide the best production for the least cost without necessarily emphasizing the potential impact to the environment. But recommendations from a nutrient management plan writer will be based on the best scenario for whole farm nutrient balance without necessarily considering the impact on animal performance. 

Ideally, the goal should be to produce and feed as much home grown forages as possible, feed total protein to the cow’s requirement, and formulate diets to improve the lactating cow’s nitrogen (N) utilization efficiency. The goal of the cropping system is to raise forages that optimize N utilization. Is there one forage system that fits all – balances farm nutrients and provides the best forage ration?

Research results
In the winter and spring of 2005, 60 cows each at the Penn State Dairy Teaching and ResearchCenter were group fed either an alfalfa- or grass-silage based ration. The performance results were extrapolated to measure the economic impact of these forage diets on a 250-cow dairy with 400 acres of cropland and a 50-cow dairy with 50 acres of cropland.

The lactating cows were fed a ration with up to 50 percent hay crop forage to 50 percent corn silage on a dry matter basis. Including all cows and heifers, this created a stocking density of 1.13 animal equivalent units (AEU) per acre for the 250-cow dairy and 2.22 AEU per acre for the 50-cow dairy. (One AEU is equal to 1000 pounds.)

Previous research suggests that farms with less than 1.25 AEU/acre are deficient in farm N balance with low pollution potential, while those with 1.25—2.25 AEU/acre are balanced for N with high pollution potential.

Under the grass silage based diet extrapolation, a major economic difference occurred on the 250-cow farm where the farm actually needed to purchase more than $7,000 in supplemental N fertilizer to meet the grass N requirement. On the 50-cow farm there was little need for additional N fertilizer in the grass based system. Because the stocking density more closely matched the crop fertilizer needs, the economic difference in purchased N was not an issue on the smaller farm. The simulation illustrated the economic benefit of appropriate animal density where animal units closely match crop nutrient requirements.

The most important effect of replacing alfalfa with grass acreage is the difference in yield potential over multiple cuttings. The 12.5 tons/acre yield potential of alfalfa compared to 8.8 tons/acre for grass requires more acreage for grass to meet forage inventory needs. Under the grass scenario, this reduces the potential acreage available to produce other crops, i.e. corn grain and can result in increased purchased feed cost for the grass-based system. 

To evaluate the underlying economic differences between the systems, milk revenue was equalized for the grass and alfalfa based rations at a rolling herd average of 27,000 pounds. The alfalfa diets generated $83 additional net farm income per cow. This agrees with work conducted by Al Rotz from the USDA pasture lab where he reported a $63 per cow advantage in net return to management for a 50 percent alfalfa/50 percent corn system compared to a 25 percent alfalfa/25 percent grass/50 percent corn system.

A producer considering a change to different forage based systems, i.e. grass-based, needs to carefully analyze this change for their unique farm situation. Soil test levels and stocking density on a particular farm will impact your economic consequences.

Remember, the management practices in harvesting and storing grass, alfalfa and corn silages vary and they can affect the quality of the ensiled forages. Some forage based systems are less forgiving than others and can result in reduced animal performance and therefore undesirable economic outcomes if not managed properly.

While the research didn’t identify an “ideal” forage system that works for every farm, it does show that producers should carefully evaluate their options related to environmental issues, whole farm nutrient balances and optimizing animal performance before making dramatic changes in the forage system.

Penn   StateDairy Alliance