Feed efficiency in lactating cows and relationship to income over feed costs

Source: PennState Extension

Feed efficiency measures the relative ability of cows to turn feed nutrients into milk or milk components. In the simplest terms it is the pounds of milk produced per pound of dry matter consumed.

What Is Feed Efficiency?

Feed efficiency (FE; sometimes called dairy efficiency or dry matter intake efficiency) is a simple measure to determine the relative ability of cows to turn feed nutrients into milk or milk components. In the simplest terms it is the pounds of milk produced per pound of dry matter consumed. This measure should always be a consideration of dairy diets and becomes increasingly important during times of decreased profit margins (high input and low returns). A way to combat these decreased profit margins is to increase the milk made from every pound of dry matter fed. An added benefit to increasing cows’ feed efficiency is that fewer nutrients will be excreted in manure, so feed efficiency affects both economic and environmental efficiency. This is of considerable importance to dairies struggling with manure application management.

There are two ways to improve feed efficiency. One is to increase milk yield with the same dry matter intake, and the other is to decrease dry matter intake and maintain the same milk yield. Many diet modifications that increase milk yield will also increase feed efficiency. In general, as the cow produces more milk the proportion of nutrients used for maintenance becomes smaller. In other words the fixed costs of the animal are spread out over more pounds of milk, making the animal more cost and energy efficient. Once the fixed costs are achieved in a dairy cow, producing additional milk takes less energy and protein. However, a problem arises with these “fixed costs,” as they are not exactly fixed. As dry matter intake increases there is a decrease in feed digestibility, and the cow becomes somewhat less efficient at extracting energy from the ration. This decrease in digestibility grows larger as intake increases and becomes a real issue in high producing dairy cows with high intakes.

Therefore it is important to optimize rather than maximize dry matter intake in the cow. In many situations getting more dry matter intake in a high producing dairy cow is an economically sound practice. However, in some circumstances the cost of having a more energy dense or digestible diet may be more expensive than the return from increased milk. This would result in a lower income over feed cost (IOFC) and would not be advised.

Calculating Feed Efficiency

There are several important factors to consider when measuring and calculating feed efficiency.

Use Actual Dry Matter Intake (DMI): Accurate DMI data is vital for accurate estimates of FE. This means weighing not only what was fed but also the refusals. Intakes can be measured for herds or groups, even for individual cows in tie-stall barns.

Measure DM of Ration Components: It is important to monitor the DM content of the TMR and the forages used in the ration to obtain accurate FE estimates. Fermented forages and TMR should be checked for DM content weekly.

Convert to Energy-Corrected Milk (ECM): It is very common to standardize FE by using ECM yield. This standardization allows for comparison across breeds or dairies that vary substantially in milk composition. The following formula should be used to convert to ECM yield (Tyrrell and Reid, 1965):

• ECM = (12.82 x fat lbs) + (7.13 x protein lbs) + (0.323 x milk lbs)

Calculations that use ECM are slightly different from those using actual (uncorrected) milk values, and both methods can be found in the literature. Both have value, and the results are often similar.

To further improve the accuracy of calculating FE, intake could also be corrected for energy content. Correcting feed DM to a standard Mcal/lb would increase the accuracy of calculating FE and allow for comparisons between rations of different compositions. Or perhaps FE could be calculated as the Mcal of milk produced per Mcal of feed consumed. Determining FE this way would eliminate the variability associated with the energy density of the TMR and forage digestibility. This method would put a greater focus on the cows’ ability to produce milk efficiently, rather than FE being a product of the feed. This would be a more effective approach when comparing animals for genetic selection, which may become more common in the future.

Factors That Influence Feed Efficiency

Forages

Forages have the greatest effect on feed efficiency. Since they make up a very large component of the slowly digestible part of the diet of lactating cows, they are critical for maintaining a desired FE. They also have a large impact on FE because they are the most variable feed ingredient in terms of digestibility and nutrient composition and they comprise a greater proportion of the ration than any other feedstuff. It has been shown that FE is directly related to forage digestibility, with increased digestibility leading to increased FE. Unless concentrates are very unusual or processed incorrectly to have damaged protein or other components, they are almost always more digestible than forages. Since energy density has the same relationship with FE, much effort should be applied during harvest, storage, and feeding of forages to achieve the highest quality forage possible. Feeding forages of only the highest quality to lactating cows is of utmost importance.

Another way that forages can influence FE is through the maintenance of a desirable rumen environment. Acidosis (low rumen pH) can negatively affect FE by decreasing fiber digestibility through changes in the rumen microbial profiles. Adequate physically effective fiber (forage particle size) in the ration will maintain the proper rumen environment by stimulating chewing and ruminating, increasing saliva secretion, and improving buffering capacity of the rumen. Forage particle length is also needed to maintain the rumen environment and proper rumen motility.

If you see that FE values are very high it may mean that forage quality and feed quality may need to be improved. This may mean having a better allocation of feeds to the various animal groups on the farm or that forage harvest practices need to change in subsequent years.

Stage of Lactation

Days in milk (DIM) will have an influence on FE, because cows in early lactation will be losing body weight and using that energy for milk production. This will artificially increase FE that is calculated using only DMI and milk production. A high FE (> 2.0) in early lactation can actually indicate a problem that cows are losing too much weight, possibly leading to other metabolic disorders. On the other hand, late-lactation cows will be gaining weight thus lowering their calculated FE. This lower FE should not be viewed negatively because cows need to gain body weight in late lactation so those body reserves can be utilized when the cow begins the next lactation in negative energy balance. Therefore average DIM of the herd should be taken into account when evaluating FE, and variation by stage of lactation is completely normal (Table 1).

Maintenance Requirements

Changes in the maintenance requirements of lactating cattle will affect how much of their energy intake they can devote to milk production. For instance, a cow grazing pasture will have to utilize more energy walking around to consume feed than a cow in a freestall or tie-stall barn. Other factors besides physical activity that can affect cows’ maintenance requirements are: body size, outside temperature or season of year, and stress. The larger the cow, the more maintenance requirements she will have. The more stressed the cow is beyond her thermoneutral zone, the more energy she will expend to maintain her normal temperature. This aspect is important for cold and especially heat stress.

Lactation Number

Feed efficiency is affected by lactation number because cows in their first lactation are still growing, and a portion of their energy intake is appropriated to support that growth. After cows reach maturity they no longer have an energy requirement for growth, and they can focus their entire energy intake on maintenance and milk production.

Cow Comfort

This factor is related to maintenance requirements because an increase in stress will generally lead to an increase in energy expended for maintenance. There are many factors that can cause cows stress, several examples are: excessive heat and cold, overcrowding, disease, and excessive mud and manure.

Feed Additives

There is evidence that feeding yeast, ionophores, and direct-fed microbials to lactating dairy cows can increase feed efficiency, especially when cows are heat stressed. These additives generally increase FE by positively affecting fiber digestion; however, the gains are usually less than could be achieved by improving forage quality.

Using Feed Efficiency

Feed efficiency is just one tool for monitoring herd performance but should never be the sole number used to make decisions. However, FE can be useful in determining if there are opportunities to improve IOFC and potentially reduce manure volume and nutrients.

IOFC is calculated as follows:

• All-milk price per cwt x (daily average milk production / 100) – daily feed cost per cow

It should never be assumed that high FE correlates with improved IOFC. Table 2 illustrates this point using a research study conducted at Penn State in 2006 that compared the nutrient efficiencies for rations based on either alfalfa or grass. Each month the particle size of the corn grain switched between coarsely ground and finely ground. All other parameters remained the same. The grass-based ration had consistently higher FE compared to the alfalfa-based ration for 3 out of the 4 months. However, the alfalfa-based ration far exceeded the grass-based ration in IOFC.

Examining FE within the forage base, in March the alfalfa diets had lower FE compared to February and April but produced more income. The same thing happened on the grass-based ration comparing February and March. It should be noted that FE was very respectable on both alfalfa and grass diets over the four months considering the rations were fed as a one-group TMR to 60 cows each at 180 days in milk.

The other scenario that can play out is a very low FE for the current level of milk production. Table 3 illustrates a real farm situation where FE is extremely low. There is a huge opportunity to improve IOFC if FE can be improved. This table represents the potential that is possible if improvements can be made to the diet without sacrificing production. If forage quality is poor then there may be limits to what is feasible to bring intakes into line. Improvements in FE could be achieved if the energy density of the diet could be increased, most likely by utilizing purchased supplements. Monitoring IOFC along with FE is a good strategy to ensure that income is not being sacrificed for improved FE.

Feed efficiency has implications for environmental concerns. In theory, if animals can more efficiently convert feed into an exportable product, i.e. milk, then less manure volume and manure nutrients should be produced. Tables 4 and 5 examine a situation where cows average 80 pounds of milk and at varying FE of 1.49, 1.55, and 1.61. The reduction of manure volume as FE improves could potentially extend the farm’s capacity to store manure for a longer time, reducing the risk of storage overflow or forced spreading of manure when conditions are less than ideal. The reduction of nitrogen and phosphorus could potentially allow more flexibility in how much manure could be spread on various fields. As demonstrated in this example, monitoring FE and examining ways to make improvements over time could have substantial implications for nutrient management plans.

Feed efficiency has many applications as a management tool to improve production, profitability, and nutrient management. For decades the beef industry has seen the importance of maintaining or improving FE to keep their margins in line. The dairy industry has been behind the curve when it comes to using FE to make decisions related to risk management and nutrient management. If used correctly FE can be a powerful tool. Making improvements in feed efficiency will almost always be profitable as it means getting more milk per unit of dry matter fed, or the same amount of milk by feeding lesser amounts of higher quality feeds.

Reviewed by Robert VanSaun and Rebecca White, Penn State

Authors: Jud Heinrichs, Professor of Dairy Science and Virginia A. Ishler, Extension Dairy Specialist