| ||Q. Why can’t I just use the feed conversion ratio, Feed:Gain, as a measure of my cattle’s feed efficiency? If I can improve the number, surely I am selecting for feed efficient cattle.
A. On any farm it would be difficult to accurately measure the feed intake of an individual animal because most do not have the time, equipment or resources to measure it. When measuring a group of cattle – whether calves, cows or bulls, the Feed:Gain will be giving you an average for the group and you will not know which animal ate the least and which one ate the most. Within a population of animals of the same class (similar age, breed, weight and management), the spread or variation in feed intake of two animals gaining at the same rate can be 35% or more. If you selected based on Feed:Gain you would essentially be selecting for growth rate (ADG) and mature size. The beef industry has already done this and over the last 25 years we have increased mature size of our cattle and we know these cattle eat more but are not necessarily producing or performing better.
Traditionally, feed efficiency in beef cattle was defined as feed to gain ratio or feed conversion ratio (FCR). However, genetic evaluation of ratio traits like FCR are problematic in that selection response is unpredictable, usually placing higher than expected emphasis on the trait with higher genetic variance. Further, the genetic correlation between the numerator (e.g., dry matter intake, DMI) and denominator (e.g., average daily gain, ADG) is positive, and therefore, selection for improved FCR has resulted in cattle that grow faster, have increased mature size, and increased maintenance and feed requirements. Alternatively, efficiency measures that remove various known energy uses from feed intake, such as body weight and production, are now being used within breeding programs. Residual feed intake, also referred to as net feed efficiency is defined as the difference between an animal’s actual feed intake and its expected feed requirement for maintenance of body size and production. It is genetically independent of body size and growth.
Q. How do you know if you are making progress over the years in feed efficiency if the average RFI value is always zero?
A. Your record keeping will be critical. First, a baseline year would be selected (e.g. 2014), which is very similar to plotting the genetic progress in any trait (e.g., 200-d weaning weight set at 450 lb in 1975). Then each successive year is compared to the baseline year so over time you can see how the average value has improved. Because RFI is a relatively new trait being selected for, you should contact your breed association for more details on establishing the average.
Q. I can’t justify the purchase of expensive individual feed intake monitoring equipment for my ranch, so how do I get the benefit of RFI into my herd?
A. Many progressive producers and organizations have access to bull test facilities that include individual feed intake measurement. Seed stock producers with tested animals will offer these animals or their progeny through sales - making certain pedigrees known for their feed efficiency. You have the opportunity to source and purchase these tested animals so their genetics get into your herd. The combination of research and commercial feed intake testing will accelerate progress in the industry. Even though the upfront cost of testing can be substantial, you will discover the potential returns on that investment to also be substantial. Because RFI is a moderately to highly heritable trait, it will be passed on to the progeny making the influence of a negative RFI (feed efficient) bull significant in your herd; whether you keep replacement heifers from him or feed calves for market.
Estimated Breeding values (EBVs) for RFI, as determined by seedstock associations, become more accurate and reliable as more animals are measured for feed intake and RFI. In addition, genomic/DNA information obtained from tissue and/or blood samples is being used to enhance the accuracy of EBVs such that young males and females can have moderate accuracy EBVs early in life.
Q. There must be one breed of cattle that is more feed efficient than some of the other breeds. So, which breed has superior feed efficiency?
A. You have heard this before, but there is just as much variation within a breed as there is between breeds. Feed efficiency is no different. Variation in feed intake of two animals gaining at the same rate can be 35% or more. As an example, if a pen of 100 calves weighing 1000 lbs has an average individual intake of 25 lbs of feed, the expected range in individual feed intakes would be 20 to 30 lbs with no difference among gain in the calves. Your challenge comes in identifying the genetics for the animals that are below 25 lbs intake. With time, some breeds may be involved in more research and genetic selection for feed efficiency, making more pedigrees with superior feed efficiency known to the beef industry.
Q. Feed efficiency is just a measure of economic importance for the feedlot industry. How can I benefit from it as a cow/calf producer?
A. Feed efficiency is a measure of economic importance to any producer of cattle including cow/calf, backgrounding, feedlot and seed stock production regardless of being a purebred or commercial producer. Cattle that have lower feed intakes for an equal level of production will have reduced feed costs compared to those animals that have higher feed intakes. Because feed costs represent up to 70% of the production costs in a beef operation there are significant savings in determining which animals are the most feed efficient and then selecting for their genetics. This is particularly true for the breeding cow herd which is on a maintenance ration for the majority of their life and we want to maintain cattle with the lowest possible feed costs without sacrificing production.
Q. What are the disadvantages of measuring or selecting for RFI?
A. The cost of currently collecting the information for a particular group or individual animal can be substantial especially if you take into account that of all the animals on an RFI test, half will get a positive ranking (inefficient) and half will get a negative ranking (efficient). However, the associated feed costs of the inefficient animals will also be substantial if you retain them in your breeding program, so careful consideration to how they are marketed needs to occur. In addition, reputation breeders that have tested over many years for RFI need to make potential customers aware if these are progeny from superior feed efficient sires. The progress that a breeder has already made because of numerous years of testing and genetic improvement may be exceptional compared to another breeder. This might make the inefficient (positive RFI) cattle attractive from the reputation breeder.
Also, RFI should not be used as single trait selection. Any good genetic and marketing program has more than one feature to impress potential customers. When performance and economics are considered, a superior growth, negative RFI and ideal conformation bull that does not pass the semen test should not be marketed for breeding purposes just as an inferior positive RFI bull with poor ADG who passes a breeding soundness evaluation should not be marketed for breeding either.
Q. Aren’t efficient cattle smaller cattle because they have lower intakes compared to larger animals? Can’t I just select for smaller sized cattle because my feed costs will be reduced just by doing so?
A. Feed efficient cattle selected through RFI have the lowest feed intakes for their performance and production. By just selecting for size you are not considering how much they are eating for their output or production. RFI estimates efficiency of use of feed consumed by subtracting observed dry matter intake of an individual animal from the dry matter intake predicted by an equation developed from the relationship between dry matter intake, daily gain and metabolic mean weight across fed contemporaries.
RFI is genetically independent of body size and growth, meaning that there are large animals that are efficient and small animals that are efficient at equal growth rates, just as there can be large inefficient and small inefficient animals.
This is the third in a series of fact sheets on RFI written by Dr. Susan Markus. The other titles are: “Making Progress with Feed Efficiency – the case for Residual Feed Intake (RFI)” and “The Economics of RFI”.
For further information on feed efficiency go to Alberta Agriculture and Rural Development’s home page www.agriculture.alberta.ca to search for RFI curriculum for cattle producers. Additional information can be found at www.livestockgentec.com and www.growsafe.com