What makes a “feed efficient” cow?

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Source: University of Minnesota

With high feed costs, improving whole-farm feed efficiency is crucial for maximizing herd profitability. The most important metric for determining your herd’s whole-farm feed efficiency is feed cost per hundredweight of energy-corrected milk sold.

Data from the University of Minnesota Center for Farm Financial Management shows that in 2022, dairy herds in Minnesota in the top 10% for profitability (net return) spent 60% as much on feed per cwt of milk ($9.58) than herds in the lowest 10% ($15.61). This highlights the critical importance of maintaining low feed costs for dairy farms.

Two factors affect whole-farm feed efficiency: 1) the amount of feed loss due to shrink and refusals and 2) the digestive and metabolic efficiency of the cow itself.

Energy losses

When thinking about feed efficiency, it is important to consider where nutrients, particularly energy, can be lost to anything other than milk production. The major sources of energy loss from cows include feces, urine, gas (primarily methane and carbon dioxide) and heat. Energy can also be retained in tissues such as adipose tissue or muscle, rather than being used for milk production.

Fecal and urinary energy loss

Fecal energy losses are mostly due to poor digestion of feeds, improper feed processing, poor ration formulation, or feeding high concentrations of low-digestibility feeds.

Even when all of these are done properly, factors such as poor bunk management, decreased eating frequency of cows, stressors such as heat, diseases, and even noise or poor water quality can still decrease digestive efficiency.

Increased urinary energy loss can occur when protein is overfed, requiring energy for excreting nitrogen.

Gas emission energy loss

Methane, carbon dioxide and other gases are produced during rumen fermentation, expelled by the cow and lost to the environment.

Much attention has been paid to reducing these gas emissions (especially methane) from an environmental standpoint, but reducing them also benefits farmers because they can represent a loss of up to about 10% of total feed energy.

Methane production is important to maintaining metabolic hydrogen balance within the rumen. Reducing methane emissions without negatively impacting rumen microbial growth and fiber degradation is challenging. Most approaches to reducing methane focus on increasing propionate concentration because propionate consumes hydrogen that would otherwise go towards methane production.

Heat energy loss

Heat is generated both during rumen fermentation and during metabolism due to the breakdown or synthesis of nutrients. The total amount of heat an animal loses can be reduced by reducing the total number of chemical reactions, particularly “wasteful” reactions.

In the rumen, certain bacterial species and protozoa are more or less wasteful. Feed additives such as ionophores selectively reduce these species.

Within the cow, activation of the immune system, heat stress or metabolic stress can lead to unproductive energy consumption. Minimizing stress on cows is a major way to improve feed efficiency.

Dilution of maintenance concept

Within dairy nutrition, we generally consider higher-producing cows to be more feed-efficient. Cows require a certain amount of energy for basal functions such as breathing, muscle contraction, digestion and hormone production, which we term “maintenance energy.”

The milk production of a cow has a minimal impact on maintenance energy. Maintenance energy takes a much smaller percentage of feed nutrients compared to milk production. As a guideline, 14-16 pounds of dry matter are needed for maintenance in a lactating cow.

Because maintenance energy needs are fixed, increased milk production decreases the percentage of energy intake used for maintenance functions compared to milk production, even if total feed intake increases.

Genetic selection

In December 2020, the Council on Dairy Cattle Breeding introduced the feed-saved trait. This trait estimates the difference in the amount of feed animals consumed after accounting for milk production, body weight and body condition. The goal is to identify sires that genetically make the same amount of milk with less feed.

Notably, because this trait requires individual feed intakes of cows, data must be collected from research herds with that capability. This means it is not measured across a diverse range of commercial environments and includes fewer total cows in its evaluation compared to data collected for traits such as milk production, confirmation, or daughter pregnancy rate.

Initial development of the feed-saved trait started at Michigan State University and the University of Wisconsin, with several other research institutions — including the University of Minnesota — contributing data to improve the evaluation. Estimates suggest that feed saved is 19% heritable, which would put it lower than production traits, but higher than health traits such as somatic cell score or daughter pregnancy rate.

Increasing the feed efficiency of individual cows is worthwhile but challenging. It requires a multi-faceted approach including proper ration formulation and reduction in animal stress. In the future, feed efficiency may be improved through genetic selection.

As we try to improve feed efficiency, it is useful to think about and minimize sources of energy loss from the animal.

Author: Isaac J. Salfer, assistant professor of dairy nutrition