Select Sires

Putting Bull Fertility in Perspective
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired July 17, 2003
With Mel DeJarnette,
reproductive specialist,
Select Sires Inc.

Mel, in this week’s Reproductive Moment you put bull fertility in perspective.

With the problems dairymen are facing getting cows pregnant these days, bull fertility has come to receive much attention in the sire selection process. While it’s always a good idea to consider a sire’s fertility in the selection process, it’s important to keep bull fertility in the proper perspective. Bull variation in fertility is usually a function of variation in the quality of semen they produce. However, unlike the herd bull running with the cows, every ejaculate taken from an A.I. sire in a major stud is screened for quality and must pass stringent standards before being released into inventory. Any collections that fail to meet these high standards are immediately discarded. As a result, what many people don’t realize is that 90 percent of all active A.I. dairy sires are within plus or minus three percent of the breed average according to ERCR’s calculated by DRMS and Raleigh. The spread of fertility from the very best to the very worst A.I. sire is seldom more than about 10 percent. In contrast, because of varying environmental and management factors, it’s routine observance for A.I. reps to see the same batch of semen from the same bull with 60 percent conception rate in one herd and 25 percent in the next. If the 25 percent conception rate herd wants to stack the odds in his favor by selecting for higher fertility sires, it’s not such a bad idea, but the reality is that selection for sire fertility can only move that average to about 28 or 29 percent at best. To become a 60 percent herd like his neighbor, it’s going to make some changes that are a lot more difficult than just sire selection. It’s a difficult tendency to break, but we really need to stop thinking in terms of high and low fertility bulls, and start thinking in terms of above and below average. When you really think about it, because of the intense quality control program, the discarding of semen at major studs, all A.I. bulls are high fertility bulls. However, by definition when you calculate an average, the individuals become divided into above and below average groupings. A good example might be the Cincinnati Bengals. In recent years they have consistently fielded a well below average football team, however they could beat the socks off of any amateur group you or I could pull together. They’re simply below average in a highly selected population of professionals. So just as selecting for high fertility sires is not going to cure all your breeding problems, using a bull who is a few percentage points below the herd average is not going to send the farm into foreclosure. If he’s got the genetics you want in your herd, don’t be afraid to use him, because he’s still a safe bet to get cows pregnant. If you don’t keep the value of genetics and fertility in perspective in your sire selection program, you could be throwing out the baby and keeping the wash water.

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Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751