The efficiency test utilizes the calibrated GrowSafe System, now Vytelle. Each bunk allows one individual to eat at a time. An electronic identification (EID) tag is utilized to collect data that essentially monitors and tracks their consumption. The data captured is utilized to calculate the RFI (Residual Feed Intake). RFI is relevant and important to producers as it correlates the pounds of gain to the pounds of intake and therefore the increment cost of gain. As such, RFI allows producers to determine those individuals who have the capacity to gain quickly and more cost effectively!
The GrowSafe Residual Feed Intake defines the incremental pounds of feed required for 1 pound of gain above or below the average (the MBT contemporary group). Efficient animals eat less than expected and have a negative or low RFI, while inefficient animals eat more than expected and have a positive or high RFI.
Midland Bull Test has 14 pens with 7 nodes in each pen. The Midland Bull Test Efficiency Test is a 49 day test that is done within the 112 day performance testing period for bulls. All Bulls on test at Midland are efficiency tested. The GrowSafe pens are also equipped with GrowSafe Beef. This technology collects fore half body weights on each bull whenever they consume water. This allows multiple weights throughout the day and provides more data points to enhance the testing. Data collected from the GrowSafe Systems is 3rd Party analyzed and verified for accuracy. This data is then utilized to produce an RFI EPD for each of the the bulls.
Feed efficiency EPDs attempt to capture an animal’s genetic ability to put on more weight with less feed. While there are many ways to calculate feed efficiency (such as feed conversion ratio and residual average daily gain), an especially useful way is residual feed intake or RFI. RFI is feed intake adjusted for an animal’s weight and gain. An animal that eats more also tends to be larger and gain more weight. By adjusting these factors out of an animal’s intake measurement, we are able to better understand which animals process feed more efficiently. We can then select for our typical growth traits (yearling weight, weaning weight, or post wean gain) and at the same time select for intake (in the form of RFI) and know that there is no double counting of an animal’s size. The RFI EPDs are expressed in actual kilograms of feed an animal will eat per day. And like other EPDs, they have an associated accuracy that expresses how sure can be of the predicted performance.
|BULL ID||RFI EPD||RFI ACC|
The table above is an example of three bulls with RFI EPDs. We would expect bull X’s calves to eat 0.65 kg more feed per day than the average calf his size, bull Y’s to eat 0.35 kg less feed per day than the average calf his size, and bull Z’s to eat 0.42 kg less feed than the average calf his size. Based on these numbers, we would obviously rather choose bull Z as a sire. Another consideration is the accuracy of prediction in selecting animals. While bull Z is more efficient than bull Y, his accuracy is also lower meaning we’re less sure about his EPDs. If we are in a situation when we would like more accuracy in our selection, we may select bull Y since his feed efficiency EPD is close to bull Z’s but his accuracy is much higher. Single trait selection is always a bad idea. RFI is no exception to this rule. Selection for RFI should always be done in conjunction with selection for growth. This selection for growth can be done by looking at weaning weight, yearling weight, or post wean gain EPDs. This will allow breeders to pick animals that gain the most while consuming the least amount of feed.