Note: An article which well describes some of limitations of using RFI indexes for selection for feed efficiency, so re-posted here for your information.
By SCOTT LAKE Beef Cattle Extension Specialist and GARY MOSS Professor University of Wyoming
There has been a tremendous buzz throughout the beef industry the last few years and the buzz is “efficiency”. Almost every symposium and popular press publication has at least one talk or article about efficiency.
Indexes (residual feed intake and residual average daily gain) have been developed and accepted by the Beef Improvement Federation and most breed registries. All this is with good reason. Feed input costs are usually the largest single expense for beef producers. If feed costs could be reduced or outputs per unit of feed increased, profitability would increase. However, as we explore and find new methods to select cattle (i.e. efficiency), it appears we are heading into an arena that has more “unknowns” than “knowns”.
For example, reducing feed costs have obvious beneficial implications, but at what cost? And are the advantages truly as beneficial as we think? Do we understand the ramifications of selecting for efficiency?
As we search for new ways to increase efficiency and ways to make our systems more profitable, are we forgetting about knowledge that is already available? Feed intake is an extremely important topic and when applied correctly, can have a marked impact on the finances of an operation. But, doesn’t it make more sense to utilize the increase in efficiency that heterosis provides and select bulls for profitability rather than efficiency?
Research reported in the 1980’s (Short et al.) described the order and importance of nutrient partitioning and assimilation. It was concluded that energy was not partitioned evenly nor randomly, but rather had defined biological orders of importance. Basal metabolism was the first order of importance for nutrient use, followed by requirements for growth, energy reserves (storing fat), pregnancy, resumption of estrous and reproductive processes.
The question we don’t understand is how animals with varying efficiencies partition nutrients. It seems likely that highly efficient animals for one trait must partition their use of nutrients differently from animals with lower efficiency. This may seem elementary, but it is important to remember that all consumed are to be partitioned to support important metabolic functions.
So what makes one animal more efficient than another? Assuming two animals with identical nutrient requirements eat the exact same amount of feed, why does one animal gain more weight than another? Do animals with greater efficiency utilize more of their energy for metabolism or growth and subsequently less for other processes, such as reproduction?
There is evidence that selection for efficiency alone can exert some detrimental effects on production in both sheep and cattle. Factors such as age of puberty could be negatively associated with feed efficiency. Scientific reports indicate there is a correlation between age at puberty and duration of post partum interval in cattle. If age of puberty in cattle is increased through selection, there is a possibility of affecting the cows’ ability to rebreed in a timely manner each year. Data in this area are inconclusive and should be sorted out before selection decisions are based on perceived economic advantages of selecting for feed efficiency alone.
How big of an economic value is associated with increased feed efficiency? One of the misunderstandings of RFI and efficiency is that these values do not necessarily translate to profitability. A recent evaluation of Grow Safe data from bull tests conducted at the University of Wyoming demonstrated that selection for RFI, or efficiency, does not translate to performance or profitability.In the bull test referred to, the difference in feed intake between the low testing RFI bull (in this case, a low RFI value is good) and the second highest RFI bull (again, in this case, a high value is bad) was a little over 3 pounds of feed per day.
If this is translated to a cow and her performance, that would equate to about $54 of extra feed over the course of a 6-month winter-feeding period that the high RFI cow would consume compared to low RFI cow. Assuming they perform similarly in efficiency to the bull test. Fifty-four dollars per cow of feed savings would be fantastic! However, the cow consuming more feed also produced a calf that would perform 20 percent better than the low RFI cow. So if the low RFI calf weighed 500 pounds at weaning, the high RFI cow produced a calf weighing 600 pounds (again assuming that calf performance will reflect that of the bull).
With today’s cattle markets, even after considering an $0.08 slide, the heavier calf is worth about $96 more than the lighter calf.Simple math tells us that even after subtracting out the added feed costs, the heavier calf was worth $42 more than the lighter calf.
Dr. Steve Paisley, University of Wyoming, has begun ranking bulls on test by RFI, as well as by a traditional ADG and feed to gain ratio. By combing these tests, a bull purchaser can see which bulls performed in the upper third of all three tests. Those are the bulls that have the greatest potential to increase a producer’s profitability. It is also important to remember that an RFI ranking at a bull test is simply an index and only applicable for comparison of animals on that test. It is possible that the bull with the best efficiency ranking in one test could end up middle of the road in another test, or even worse than the bulls/cows that you already own.
Please don’t misunderstand; RFI is a fantastic tool that allows beef cattle producers to make informed decisions about animal selection. However, it is a tool and should be used in conjunction with the other tools that producers already use for selection criteria. The assumption that cows and calves perform similarly to the bulls on test is not proven. Bulls are usually placed on a fairly high plain of nutrition in a lot. How does test performance translate to cows foraging on range grass or “limit-fed” hay during winter?
Considering the vast differences in physiological processes that occur for nutrient digestion and assimilation between a forage and grain diet, it is questionable if there is a direct correlation between efficiency measured with forage diets compared to grain fed diets. If cattle producers want to increase profitability and whole system efficiency, reproduction can have one of the greatest impacts simply because even small calves are worth more than no calves.
One of the real puzzles in the beef industry is why don’t more beef cattle producers crossbreed cows? As we chase efficiency and ways to be more profitable, think about this, crossbred cows produce on average 1.5 more calves in their lifetime, mainly because they stay in the herd on average 1.5 years longer. Crossbred cows also have an approximately 2 percent increase in weaning ratio, wean calves that are 18 percent heavier, and those calves gain 0.1 pounds/day more throughout their lifetime. If maintaining the right color is of importance, there are many breeds that will help maximize growth and are available in black, red, white and every shade in between.
Maybe the best scenario of both worlds is to utilize RFI in a production index as described above, and select for efficient high growth bulls in a crossbreeding program. Thereby, taking advantage of the benefits of both heterosis and feed efficiency. Feed efficiency is an important tool for selection that when used in conjunction with other tools, can have a beneficial impact on profitability.
However, for breeding cows and bulls, feed efficiency or RFI is just one aspect of production that should be considered as a selection criteria. The most important measure of production efficiency is producing the most pounds of quality beef per unit of forage or concentrate. This index clearly differs by cattle type, reproductive performance, forage/feed type, and the environment of each production enterprise. If cattle producers want to increase profitability and whole system efficiency, reproduction can have one of the greatest impacts simply because even small calves are worth more than no calves.