The definition of efficiency is a ratio of outputs to inputs. Businesses use measures of efficiency to establish benchmarks and goals for production and finance, which may result in decisions that increase productivity without increasing costs of production. A well-run, profitable commodity business is usually operated more efficiently than its competitors. 

In the case of beef cattle, competition can arise from two sources: other producers who sell similar classes of cattle and other protein-producing species, such as pork and poultry, that compete with beef in the marketplace. Measuring efficiency across the entire integrated beef system is difficult due to the different classes of cattle (growing, finishing, breeding), breed differences and how the different biological systems (nutrition, reproduction, lactation, basal metabolism) interact. There are measures of efficiency that can be used to optimize biological productivity and/or economical profitability in beef production enterprises. One of these is feed efficiency.

Although the depths of feed efficiency research have vastly expanded in the past decade, most research efforts have focused on growing/fed cattle. Still today, little data has been collected on the breeding herd, which consumes about 70% of the feed utilized throughout all beef production systems. Forage-grazing females such as replacement heifers, young cows and mature cows compose the predominant classes of cattle. Therefore, it is important for producers to better understand the implications feed efficiency has on the breeding herd.

Feed efficiency

Residual feed intake (RFI) is one measure of feed efficiency that has not been shown to increase mature weights or greatly affect other phenotypic traits in cattle. It measures the variation in feed intake beyond that needed to support maintenance and growth requirements. It is calculated as the difference between actual feed intake and the feed an animal is expected to consume based on its body weight and average daily gain. Therefore, when cattle consume less feed than expected for their size and rate of gain, they have a negative RFI, which equates to a more desirable feed efficiency status as compared to cattle with more positive RFI values. 

One of the important findings in almost all of the studies to date show little or no correlated response in other important traits such as growth rate when selecting for RFI, so calves with lower RFI values consume less feed for similar performance.

Reproductive efficiency

Reproductive efficiency is a key component to cow-calf enterprises because it is a primary determinant of profitability. Since nutritional status has been identified as an important mediator of reproductive events, differences in feed intake may affect the age of puberty for heifers as well as the length of the anestrous period for cows. 

It has been reported heifers with positive RFI values (inefficient) tend to reach puberty earlier than negative RFI (efficient) heifers, whereas no effects have been noted on pregnancy or conception rates.   

In mature, non-lactating cows, pregnancy rates for cows producing low, medium or high RFI progeny were similar. However, cows producing more efficient progeny tended to calve later in the season than their counterparts. Therefore, it appears that RFI has no effect on overall pregnancy rates. However, more efficient females may have slightly delayed attainment of pregnancy throughout their lifetime.    

One study investigated the postpartum reproductive performance of first-calf heifers and multiparous cows that had been previously evaluated shortly after weaning for RFI. Although prepartum and postpartum body weight and body condition score (BCS) did not differ by RFI group for either cows or heifers, efficient cows exhibited estrus sooner, developed a corpus luteum (CL) sooner, and exhibited estrus in conjunction with CL formation sooner than inefficient cows. However, no difference was detected between efficient and inefficient heifers for estrus and/or CL formation. 

The authors concluded selection for efficient cattle using RFI as a selection tool may result in a shorter postpartum interval in multiparous Brahman cows. When cow performance was assessed based on heifer feed efficiency rank (Table 1), cows that were most efficient as heifers had significantly lower DMI than their counterparts and consumed 2.6 or 2.8 pounds (lb.) a day less than cows that were medium and high heifers. Interestingly, DMI was the only parameter that significantly differed. Therefore, the most efficient heifers subsequently became cows that were phenotypically similar, but consumed less feed than cows that were considered less efficient as heifers.  

With these results taken collectively, it still remains unclear whether or not more efficient females have a reproductive advantage or disadvantage over less efficient counterparts. Feed efficiency is not a new measure, but it is one that is receiving more attention as feed costs have increased. 

Ongoing and future research efforts in feed efficiency will likely clarify how feed efficiency affects the reproductive efficiency of the breeding herd. Producers who understand and appropriately incorporate this type of information into their operation will have the means to make sound decisions to improve the efficiency and profitability of their enterprise.