by Chad Mullins and Barry Bradford
The authors are a Ph.D. student and assistant professor of dairy cattle nutrition, Kansas State University, Manhattan.
The lower milk prices are generally, the harder it is to justify high-priced alfalfa. Having by-product feeds nearby is a key.
People are beginning to reconsider alfalfa's role in rations.
Because traditional feeds can be costly, more people are looking towards co-products. Many of these commonly fed are derived from corn milling and fall into a broad category referred to as nonforage fiber sources. Most of these are relatively inexpensive compared to cereal grains.
But, results from feeding high levels of nonforage fiber sources in place of forages or concentrates have been mixed. Success depends a lot on other ration ingredients. Our challenge is to incorporate these nonforage fiber sources effectively in an effort to limit the use of expensive ingredients.
Alfalfa hay, in particular, has become more expensive. Because of greater pressure for land use, the amount of land devoted to alfalfa has declined by nearly 4 million acres since 1995. Not surprisingly, as alfalfa supplies have become tighter, its cost has risen by nearly 50 percent in the last 20 years.
Looking at alfalfa's value
Recently, we examined the possibility of cutting back on alfalfa or eliminating it altogether, with the use of nonfiber forage sources. Because of the mechanical stimulation provided by alfalfa hay, our primary concern was that feeding diets without alfalfa hay could lead to rumen problems or milkfat depression. The trial was reported in the July 2009 Journal of Dairy Science, page 3510.
Our study evaluated four diets formulated to contain 21, 14, 7, and 0 percent alfalfa hay (all on a dry matter basis) as shown in the table. Alfalfa hay used in this study was of typical quality for dairy use (relative feed value: 147). We balanced the rations for similar concentrations of crude protein, neutral detergent fiber, nonfiber carbohydrate, and starch. As a result, rations containing more alfalfa had less corn silage and less soybean meal but more corn grain. We included wet corn gluten feed at 31 percent of dietary dry matter (DM) as the nonforage fiber sources.
Cows consuming more alfalfa hay produced more milk and had less body weight gain than those fed less alfalfa. Cows fed more alfalfa also had greater feed intake. Surprisingly, treatments did not affect milkfat yield or level.
When we calculated the energy used for body weight gain and milk production, the total net energy for productive use actually dropped with more alfalfa in the ration despite greater milk production and intake. This relationship strongly suggests that adding alfalfa hay lowered diet digestibility.
Although feeding higher levels of alfalfa hay improved milk production, it also led to greater feed intake. We evaluated the potential economic effects of such a response to determine the theoretical value of alfalfa hay relative to corn silage. We incorporated changes in milk income, feed consumed, and feed costs in a model to determine the relative difference in alfalfa hay versus corn silage value (on a dry matter basis). We fixed the price of alfalfa and milk, but changes to these numbers had little effect since the model was based on the milk:feed price ratio. Adding 21 percent alfalfa hay also allowed the exchange of 5 percent soybean meal for corn grain. So, the model was somewhat sensitive to the soybean meal to corn grain price differential. We set the soybean meal to corn price differential at $188 per ton which was a typical value for the summer of 2009.
According to our analysis, the breakeven price that can be paid for alfalfa hay substantially drops with lower milk:feed ratios. When the ratio is low, the added milk you get from alfalfa hay does not offset the cost of this feed.
For example, at a milk:feed price ratio of 1.45 (June 2009 which was a record low), alfalfa hay is worth no more than $35 per ton of dry matter over the price per ton of corn silage (on a dry matter basis). Thus, if corn silage is worth $100 per ton of dry matter, alfalfa hay is worth $135 per ton of dry matter or $120 as-fed. As the milk:feed price ratio goes up, the value of alfalfa hay compared to corn silage becomes greater. At a milk:feed ratio of 2.5, alfalfa hay is worth $50 per ton of dry matter more. Consequently, if corn silage is worth $100, then alfalfa hay should be worth $150 per ton of dry matter ($135 as-fed).
The value of alfalfa hay determined by our model is below typical on-farm prices and considerably less than the average price in 2008 ($172). If the soybean meal to corn price differential is $188 per ton or less, alfalfa hay never should demand more than a $60-per-ton of dry matter premium over corn silage.
Because our research demonstrated little economic return from including alfalfa hay in the diet when the milk:feed price ratio is low, we used a partial budget model to evaluate responses from a similar study where rates of feeding alfalfa hay varied, but treatment effects on milk production and feed intake were more dramatic. This data was reported by a group of researchers at South Dakota State University. That group fed diets with 15 percent distillers grains as a nonforage fiber source instead of wet corn gluten feed. In their study, protein values were kept similar by adding corn gluten meal (instead of soybean meal) as alfalfa was pulled out.
In that situation, the effect of milk:feed price ratio on breakeven alfalfa hay to corn silage price differential was far greater (range minus $20 to $100 per ton dry matter). The model demonstrates that, with a low milk:feed price ratio, it is hard to justify alfalfa hay in similar diets, but during periods with a high milk:feed price ratio (such as 4.0) alfalfa can demand a premium of up to $100 per ton of dry matter over corn silage.
What this means
Dairy nutritionists traditionally have relied heavily on alfalfa. However, based on these studies, adding alfalfa hay to diets with large proportions of nonforage fiber sources may not be profitable, especially when milk:feed price ratios are low.
The relative value of alfalfa hay presented here is calculated from intake and production variables. It does not include costs associated with feed storage or predicted increases in manure output or impacts on body weight change when more alfalfa is fed. On most farms, commodity storage is limited, less manure output is desirable, and cows that gain weight (in early to midlactation) generally breed back more easily.
The strategy of reducing alfalfa hay feeding rates may only work if your farm is located in an area where nonforage fiber sources are readily available. In that case, feeding less alfalfa hay may help you improve return over feed cost. On the other hand, if the nonforage fiber source has to be hauled a considerable distance, you probably have little to gain. Also, cows require a certain amount of forage fiber, and, if alfalfa hay is replaced partially by corn silage, you will need enough corn acres to grow the additional forage.