County Extension Director
G. Cliff Lamb
Assistant Director, Animal Science Programs
University of Florida, North Florida Research & Education Center
Efficiency has become the new emphasis in agriculture. There was a time when the goal was simply to maximize production, such as higher yields from our forages and more growth from our cattle. There does come a point when achieving maximum performance costs more than it is worth. With the increase in input costs of feed, fuel, and fertilizer, maximum performance does not produce the same returns as in the past. Hence the new trend for selection pressure on efficiency.
Photo Credits: Judy Ludlow
For the first time ever, we can select bulls based on feed efficiency, in addition to growth and carcass traits through the Florida Bull Test. Ranchers now have tools to select bulls that gain at a high rate on less feed. More importantly we can avoid bulls that consume high levels of feed and don’t perform as well. Over time, selecting more efficient bulls will improve the feed efficiency of the entire herd.
The two bulls compared in Table 1 both finished in the top 10 of the Bull Test with over 4 pounds of weight gain per day. The difference is that it took more than 12 pounds of feed on a daily basis to achieve similar gains of 4 pounds per day. This resulted in Bull B consuming 3.5 pounds more feed to gain a pound of weight compared to Bull A. Both bulls had excellent performance on the Bull Test, one, however, was significantly more efficient to feed.
One of the real challenges for selection for feed efficiency is to determine what data to use for comparison of animals of different frame sizes, age and weights. Researchers have developed an index called Residual Feed Intake (RFI). The RFI trait is the difference between actual intake and the predicted or expected intake, which is calculated based on animal weight and performance. The key to RFI is that it is highly heritable, yet is not highly correlated to performance traits, meaning selecting for RFI should have very little impact on other traits of interest.
As in every other lesson we have learned in selecting livestock, you can’t just select for one trait. If you select only based on RFI you can end up with cattle that don’t perform well in other vital areas such as growth, fertility, or carcass quality. This is just another tool to help ranchers select bulls that will improve the genetics of their herds, and in the end be more profitable.
Table 1 summarizes actual data, comparing the efficiency of two Angus bulls to the average of the 48 bulls in the 2010 Florida Bull Test. RFI = residual feed intake
Actual Data Start Wt. End Wt. Total Gain Feed Intake/day Avg.Daily Gain Lbs feed/ lb gain RFI – (residual feed intake) Bull A (Most Efficient) 734 1195 461 22.1 4.12 5.1 -3.7 Avg. for 48 bulls 812 1198 386 24.2 3.42 7.7 0 Bull B (Least Efficient) 1040 1498 458 34.5 4.08 8.6 4.8