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Calculating feed efficiency

Virginia Ishler Published on 30 June 2014

The livestock industry has used feed conversion ratio, feed conversion rate or feed conversion efficiency to measure an animal’s efficiency in converting feed mass into increased body mass. This has been used by the beef, poultry, swine and fish industries as a way to measure profitability.

It is only recently that feed efficiency or dry matter intake efficiency has been used in monitoring the performance of dairy cattle. For dairy, it is a measure to determine the ability of lactating cows to turn feed nutrients into energy-corrected milk. It takes energy to not only produce the volume of milk but also the fat and protein in the milk.

There are two main reasons why feed efficiency has gained a lot of attention recently. The first deals with the volatility of the grain markets. When corn was more than $7 per bushel and soybeans more than $12 per bushel, this forced producers and nutritionists to examine ways to improve profit margins.

The other reason is related to nutrient management. The more efficient cows are at converting feed into milk, then it seems reasonable there would be less manure excreted. This has implications to producers with a limited land base.

How is feed efficiency calculated?
For lactating dairy cows, feed efficiency equals energy-corrected milk divided by dry matter intake. Figure 1 shows an example calculation. The most difficult number to obtain in this equation is dry matter intake. As important as this number is, it is still very elusive on many dairy operations.

Calculating feed efficiency

For herds that have the luxury of grouping cows based on certain criteria, feed efficiency can help determine if the ration is on target. If it is being done on a whole-herd basis, this can be a useful number to check monthly over time to make sure the herd is on track based on days in milk.

If feed efficiency is going to be a truly meaningful number, then measuring dry matter intake is essential. For herds feeding a TMR, this would require knowing the dry matter percentage of the TMR, the batch weight fed to the group, the number of cows in the group and the refusals.

There are several ways in which the dry matter percentage can be determined. A digital scale, microwave oven or Koster tester are fairly standard methods. A TMR analysis that matches to the appropriate feeding date can be used, or there are new devices available for instant dry matter determinations on farm.

With feed costs being high, many producers feed for limited refusals: 0 to 3 percent. This number can be determined by taking a skid steer and recording the number of bucketloads of refusals. Producers usually have a good handle on the weight of the feed in one bucketload and can estimate if scales are not available. Some producers will put the refusals back in the mixer wagon to check weights.

Once all the information is available, dry matter intake can be determined for the pen. For example, a farm has a pen of 60 cows fed 7,000 pounds of TMR with 250 pounds of refusal and the TMR testing 53 percent dry matter. The calculation would be: (7,000 pounds - 250 pounds) x 0.53 / 60 = 59.6 pounds of dry matter intake. Using the equation in Figure 1, feed efficiency could be calculated.

If a producer wants to calculate the dry matter intake for the entire herd, ideally it should be done for each group, weighted for the number of cows in each group and the average intake determined.

For example, if a herd has two lactating cow groups, pen 1 holds 60 cows averaging 59.6 pounds of intake and pen 2 has 120 cows averaging 54 pounds of intake, the herd average would be (59.6 x 60) + (120 x 54) / 180 cows = 55.9 pounds dry matter intake for the herd.

In component-fed herds where all ingredients are fed separately, each individual forage and grain would need weighed and its dry matter percent determined. The dry matter percentage of the forages would have to be known.

Platform scales costing around $70 could be used to weigh the feeds. The amount delivered to a cow could be scooped into a bucket and weighed. The weights should be determined for about five cows that are close to average production based on the bulk tank average or by the Dairy Herd Improvement Association (DHIA).

Once the as-fed amounts per cow are known, the dry matter pounds would be calculated similar to the TMR-fed herd, all ingredient amounts added up for an average dry matter intake.

What are the feed efficiency recommendations?
Table 1 lists the recommended feed efficiency for cows in various stages of lactation. Feed efficiency is a tool to assist in determining if there are potential problems and should not be used as the only information when making decisions to change.

Feed efficiency for cows

There are some strategies to consider if feed efficiency is too low (less than 1.3) or too high (more than 1.8). First, always recheck your weights and calculations to make sure the number you have is correct. If the feed efficiency is really low, then energy can be a limiting factor. Cows tend to consume dry matter to meet their energy needs.

If forage quality is poor, high-byproduct feeds are fed or the amount of energy fed is not sufficient, cows may consume a lot of dry matter but not produce for the level of intake. If feed efficiency is too high, then the energy density of the diet may be very high due to the inclusion of added fats.

The issue with a too-high feed efficiency is that cows eat pounds, and many times cows are not receiving enough fiber pounds (neutral-detergent fiber) or other nutrients that could impact both production and health over the long term. Feed efficiency can be high in cows producing a lot of milk but not eating well because of metabolic disease.

Feed efficiency should be monitored over time as a means to make sure the ration is on track for production. PD

virginia ishler

Virginia Ishler
Extension Specialist
Penn State University – Extension Dairy Team

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