GENETIC POTENTIAL OF FEED EFFICIENCY BEING EXPLORED

by: Wes Ishmael

Whoever first uttered that immortal maxim about being unable to manage something without measuring it was likely someone in the cow business—casting a wishful and frustrated glance at his cows, then at his hay pile.

You know that feed costs comprise the lion's share of annual cow carrying costs. Peruse the research literature and you understand why: 70-75 percent of dietary energy consumed by beef cows goes toward maintenance alone.

Consequently, you understand if you could alter average feed efficiency—how much a cow consumes, relative to her production—just a little, you could make a giant difference in the bottom line.

Specifically, Mark Allan, explained in an article last year, “With 70-80% of the total variable costs in beef production being feed costs, the slightest improvement in feed efficiency will have a significant impact in profitability in multiple areas of beef production (see RFI Value).” Allan is a molecular geneticist who until recently worked in the Nutrition Research Unit at the U.S. Meat Animal Research Center (MARC). In December he went to work for Pfizer Animal Health as Associate Global Director of Technical Services.

Unfortunately, you also realize how impossible the dream can seem.

Identifying feed efficiency in cattle has always been an after-the-fact process and fairly convoluted besides. At least on a group basis, it's easy to determine how much feedlot cattle consume, relative to how much weight they gain, which yields a feed-to-gain ratio. Heretofore, that's about all anyone had to go on when it came to feed efficiency.

The chief challenge with this kind of information is that feed-to-gain only tells you a part of the efficiency story. It tells you something about feed intake and gain, but says nothing about animal weight or body composition at the time, nothing about how efficiently an animal utilizes each pound consumed for maintenance.

Consequently, using feed-to-gain as a selection tool on the front side of the equation would mean choosing animals that consume more, gain more or both. On both counts, you typically are selecting for cattle that gain more, which also usually have larger mature size. So, you end up selecting for cattle with higher dietary maintenance requirements, though you still have no idea how efficient the cattle are for maintenance.

The New Measuring Stick

That's why Residual Feed Intake (RFI) has captured the industry's imagination in recent years. In basic terms RFI (also known as Net Feed Efficiency) is defined as the difference between an animal's actual feed intake and the feed intake expected for maintenance and weight gain. In other words, RFI measures the efficiency of cattle to utilize each pound of feed consumed. Icing on the cake comes with the fact that it is independent of gain.

At least it does when it comes to growing and finishing cattle. Though RFI is a useful tool, Allan is quick to point out, “All the data generated to date is in growing and finishing bulls and steers. There is presently no evidence that RFI in growing and finishing animals equates to efficiency in the cow.”

With RFI, a lower number is more beneficial. Compared to those with a higher RFI, a lower number means the animal consumed less feed than expected for the performance it achieved.

“This information can be utilized in the selection of bulls expected to sire calves with lower finishing feed costs and daughters with lower feed maintenance requirements,” explains John Dhuyvetter, an area livestock specialist at North Dakota State University's North Central Research Extension Center in Minot.

The notion of RFI isn't new, nor is the knowledge about what is required to calculate it, but technology in recent years has made it more practical to exploit the potential.

As the RFI definition suggests, calculating it requires collecting individual animal intake data. Researchers have accomplished this over the years by various means, everything from housing and feeding cattle individually—weighing feed in and out of the bunk—to more automated systems whereby test animals are limited to a specific feeding gate. Each method was time consuming and too expensive to be utilized beyond isolated research projects. Plus, such systems couldn't account for how the systems changed cattle behavior and the subsequent impact on feed consumption and conversion.

“The lack of progress in understanding the genetics of feed efficiency stems from the difficulty in trying to accurately measure individual intakes, coupled with extreme costs and beef cattle's long generation interval,” says Allan. “Feed efficiency is difficult to define and needs to be evaluated in the producing female, as well the growing/finishing animal.”

Enter a handful of companies that have developed automated daily intake and behavior monitoring systems that make collecting the data accurate and economically feasible.

Arguably the most popular commercial systems in the United States today come from Grow-Safe, LLC, a Canadian company. According to the company, GrowSafe technology is behind more than 120 scientific publications. More than 40 agricultural universities utilize their systems.

The company's efforts in this area trace back to the early 1990's, developing monitoring systems capable of reading multiple low frequency Radio Frequency Identification (RFID) transponders in close proximity to one another. By 1996 that meant they could develop a system by which individual cattle could be monitored in a feedlot situation for how often they went to the feed bunk and how long they stayed each time. A few years later, the folks at GrowSafe incorporated, among other things, the accurate measure of animal weight, feed intake and animal behavior. In 2002, the addition of other measures, including thermal imaging and ultrasound started bringing more customers into the fold. All told, a system today can integrate data from up to 256 external devices, environmental and biologic sensors. So, the system is about lots more than individual feed intake, though that aspect is central to ferreting out RFI.

Incidentally, the feed efficiency research facility MARC installed several years back has a one-time capacity of 300 head. It comes from a European company and allows them to also track individual feed and water intake, as well as about anything else your mind can conjure.

Not only are universities using the systems, but also some feedlots, bull test stations and even individual producers.

“We can begin adding positive selection pressure for a trait that hasn't been selected for to this point,” says Kent Abele, owner and manager of the Green Springs Bull Test (GSPT) at Nevada, Mo. GPST was the first publicly accessible bull test station in the U.S. to install a GrowSafe Feed Intake Monitoring System, making it the first public facility in the nation offering individual feed efficiency and residual feed intake data on a volume of bulls.

It's an eye-opener, too. According to Abele, there are huge RFI variations between animals, as well as noticeable differences between breeds. All add up to significant differences in cost.

Dhuyvetter explains, “In yearling bulls on feed tests, the variation is more than 5 pounds less feed per day for similar performance. Selection for low RFI could reduce cow herd maintenance requirements by up to 10 percent through time. Research also indicates selection for low RFI would lower methane emissions and reduce nutrients in manure.”

“The really exciting thing is that we're starting to see a high correlation between feedlot efficiency and forage efficiency,” says Abele.

Taking the Genetic Step

Ultimately, as with other individual animal measures, the keystone value of individual animal RFI data will come with its incorporation into Expected Progeny Differences (EPDs) and other genetic prediction tools.

“Heritability of feed efficiency has been estimated to be moderate, with values ranging from .28 to .44. These values indicate that genetic variation among and within beef cattle populations does exist for feed efficiency, making genetic selection possible,” says Allan.

Some breed associations already offer EPDs based upon RFI. An as example, the Red Angus Association of America provides members with an EPD for Maintenance Energy, and the American Angus Association calculates an economic EPD for Cow Energy Value. As well, some genomics companies offer individual DNA tests for RFI or as part of overall genetic profiles.

According to Dhuyvetter, current markers identify a portion of the variation in RFI, with the most favorably rated genotypes saving about 2.5 pounds of feed per day at similar gains, compared with the least favorable genotypes. He explains that for many breed populations, the practical range of variation that current markers identify is more likely to be .5 to 1 pound.

What's more, Whole Genome Selection could accelerate the breadth and depth of RFI data and subsequent genetic predictions. In simple terms, according to the Agricultural Research Service, Whole Genome-enabled animal selection is a technique that scans the animal's genome, the makeup of its DNA and predicts its genetic merit as a potential future parent. For more information about Whole Genome Selection, see So Cool, in July/August '08 Western Cowman.

As with any other trait of economic importance, Abele cautions folks to keep it within the perspective of balanced trait selection. More specifically, he suggests producers use other traits to identify bulls they're interested in, then make sure those bulls have an RFI that keeps them among the top two-thirds of the population for the trait.

Moreover, Allan explains, “It is critical with RFI that it is used in an index. Many of the RFI animals with the best RFI are in the bottom 50 percent for gain (low appetite, low gain)…We need to be careful not to select for animals with decreased appetite on the cow side. In some environments, limiting cow appetite could have terrible consequences.”

“The economic potential from widespread improvement in feed efficiency is huge for the cattle industry,” Dhuyvetter says. “At today's high grain and feed prices, the measurement, evaluation and application of improving feed efficiency are rightly receiving a lot of industry and academic attention.”

RFI Value

According to Alberta Agriculture and Rural Development (AARD), research in Alberta and Australia indicates that efficient growing animals (as measured by RFI) are efficient as adult cattle. As well, progeny of efficient beef cattle are also more efficient than those of less efficient cattle. Further, the folks at AARD say this same research shows that selection for low RFI can:

• lower maintenance requirements of the cow herd by 9-10 percent

• reduce feed intake by 10-12 percent

• have no effect on average daily gain or mature size

• improve feed conversion ratio by 9-15 percent

• slow gain in empty body fat by 4 percent

• lower weights of liver, stomach and intestines

• have no effect on distribution of 9 wholesale cuts

• improve calf-weight-per-cow feed intake by 15 percent

• lower methane emissions by 25-30 percent

• reduce manure nitrogen, phosphorus and potassium

Source: Alberta Agriculture and Rural Development, Agri-Facts, July 2006







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