Accounting for Fertilizer Value in Purchased Feeds for Beef Cows

Published: March 28, 2008

When you purchase feed for beef cattle, you are bringing fertilizer onto your farm. Corn, hay and other feedstuffs all contain nutrients that pass through the animal into the feces and urine. Since fertilizer prices are much higher than last year, it means the fertilizer value of the nutrients in feedstuffs could influence the decision of what is the least-cost source of supplemental feed for cattle on your farm.

Table 1 lists the nutrient concentration and total digestible nutrients of selected feedstuffs. These common feedstuffs vary in both their feeding value and the density of nutrients in the feed.

Not all the nutrients in the feed will be available as fertilizer in the manure. Growing and lactating animals will retain some feed nutrients, and some nitrogen will be lost from urine in the field. Still, the nutrient value can be significant and can differ significantly among feed types.

There are two ways fertilizer value can be integrated into feed purchasing decisions. The most straight forward approach is to consider the impact of the possible fertilizer value on the purchase price of the feed. For example, a ton of low quality hay contains 55 pounds of fertilizer nutrients whereas the high quality hay contains 115 pounds based on the feed analysis in Table 1. If we assume 35 percent of the nitrogen and 85 percent of the phosphate and potash is available as fertilizer in the manure, high quality hay has over double the fertilizer value of low quality hay ($45/ton vs. $20/ton based on $0.70/lb nitrogen, $0.70/lb phosphate and $0.55/ lb potash). This difference could be used to justify some of the higher price of high quality hay.

In another example with the same assumptions, dried distiller's grain contains about three times more nutrients than corn grain (152 versus 46 lbs/ton). After animal retention and estimated losses, the fertilizer value of dried distiller's grains is $56/ton compared to $17/ton for corn grain.

Since most beef cattle diets are more likely to be deficient in energy than in protein, when producers compare feeds they should evaluate them based on the cost per ton total digestible nutrients (TDN). For example, which is the better value, corn at $5.50/bushel ($196/ton) or high quality hay at $125/ton? The comparative costs per ton of dry matter are $218 for corn ($196/0.9) and $144 for high quality hay ($125/0.87). The comparative costs per ton of TDN are $243 for corn ($218/0.9) and $240 for high quality hay ($144/0.60). So, on a TDN basis the two sources of feed have similar value.

However, if you consider the fertilizer value the picture changes. To get one ton TDN with corn you need to feed 1.2 tons of corn with a fertilizer value of $22 (1.2 tons X $17/ton). With high quality hay you need to feed 1.9 tons of hay with a fertilizer value of $86 (1.9 tons X $45/ton). If you value the fertilizer on your farm the hay is a much better value feed.

The fertilizer value in supplemental feeds will be completely wasted unless farmers have a plan capture and efficiently utilize it. Spread the wealth! Frequently move feeders and feeding areas around the pasture. And do not feed in the same pasture every winter but change fields to distribute the fertilizer benefits of supplemental feeds around your farm.

When you purchase feeds ask for or obtain a feed analysis and determine the fertilizer value of your specific feed. For more information on the fertilizer value of feeds see MU guide 2083 "Calculating Fertilizer Value of Supplemental Feed for Cattle on Pasture" (http://extension.missouri.edu/explorepdf/agguides/ansci/g02083.pdf.)