The Heartbreak Bull

For some of us, a new bull or blood line is just what we think we need this year. We have to decide whether to choose: 1) from our herd, 2) an out cross (same breed, different blood lines) or 3) a different breed than we currently own. The latter two options give us some hybrid vigor, but with that comes a dilution to the genetics that you have created to perform on your ranch. Everything else being equal, the bull of a different breed will give us more hybrid vigor (Webster: Increased vigor or other superior qualities arising from the crossbreeding of genetically different plants or animals. Also called heterosis.) than staying within our breed. Now, I don’t know that these qualities are always superior to what nature has in mind at our zip code. This article is not about that whole discussion.

Both of these crossing scenarios will give different results themselves and differing amounts of hybrid vigor depending upon how much crossing the creator of the bull(s) has already done himself.

More of us need to think about the characteristics this selected bull is going to be passing along to his daughters rather than just a bigger weaned calf. We HAVE TO live for the next two to seven years with those heifers-become-cows that are the siblings to the short-term-profit from a larger weaned calf (maximum production at all costs). If we base our selection criteria for this new bull on what mother nature will throw at him and his offspring in our environment, we GET TO live for the next ten to twelve years (low input cost and high fertility) with his heifers-become-cows.

Why the difference in longevity between the two scenarios I proposed above? Hormonal function, butterfat and phenotype are the genetic differences. Epigenetics* also play a part in how performance plays out from ranch to ranch. Better hormonal function is observed in both bulls and cows that shed their winter hair coat early and in bulls whose shoulders are taller than their hook bones. The genetic ability to pass along butterfat can be observed in a bull with unusually small legs (length and diameter) and numerous vertical folds in the hide (hopefully this phenomenon can be seen extending all the way to the back of the ribs). The phenotype that most closely indicates fertility in a bull is seen in wide shoulders, a large crest and large testicles in a scrotum that is bald and shaped like a football. These highlights are only a few of the many indicators of each of these desirable traits.

And then there is the whole discussion around developing on grain or not and what that does to the quantity and quality of semen production. Long story short, we wind up with fat cells taking the place of semen-producing cells and the testicles stay too warm, thereby producing more abnormal cells and fewer sperm cells in general.

Let’s assume we have decided the space race (long, tall cows with a reverse wedge) is not working for cow fertility and that the keeping costs of the resultant heifers-become-cows on the ranch is too high. Looking for a smaller-frame bull to bring our cow size back down seems to make sense.

We should NOT go from frame-score seven bulls to frame-score three bulls on frame-score seven cows all in one year. Remember how many calves were pulled as you tried to go up in frame score trying to get that higher weaning weight? Large moves in either direction have consequences!

Just think of the angles involved at the time the bull joins with the cow. That really short bull on a tall cow is similar to laying the target at the rifle range away from you on a forty-five-degree slope: much harder to hit at one hundred yards. And then if our cows have forward-sloping vulvas instead of vertical vulvas, we have made the angle of entry even more shallow. Just as in the movie Apollo 13, where they were worried about the returning capsule skipping off the earth’s atmosphere because the angle kept lessening because they had not brought back any moon rocks. But I digest.

Regarding hitting the target at the rifle range, the closer the steady rest is positioned to the front of the barrel of the rifle, the more accurate the shots are grouped on the target. Similarly, with the bull, the closer the prepuce opening is to the belly of the bull the more accurate his aim. A prepuce that hangs down three to four inches makes it harder for the bull to aim during mating.

A frame-three bull at fifteen months of age is 47.1 inches tall. A frame-seven heifer at fifteen months of age is 52 inches tall. OK, I can see how that COULD work. But what if we are trying to breed mature frame-seven cows at 55.8 inches tall. That frame-three bull is not as tall or long as that frame-seven bull, so during breeding attempts, he looks a bit like Trigger when Roy Rogers asked him to rear up. Add in that non-vertical vulva and, “Houston we have a problem.”

Usually when I finally hear about the problem of a broken tool on a young bull it was almost always on the best yearling bull someone bought. To start off, I have to consider what would have been going on in that bull for him to be considered the best and why did that lead to the problem?

In a bull, fertility (I don’t like to use masculinity anymore because it is too subjective) can be measured in shoulder width and the total dimension of the testicles. There are secondary traits that are also described in Herd Bull Fertility by James Drayson’s, Bonsma Lectures by Jan Bonsma, Factors Affecting Calf Crop by Koger, Reproduction and Animal Health by Gearld Fry and others. The wider the shoulders of the bull are compared to the length of the rump, the more fertile the bull, everything else being equal.

Drayson’s book lays out testicular circumference and LENGTH for various ages of the animals and puts them into five categories of breeding capability. You want a bull in the top two categories, optimal and tolerable. Regarding length and circumference, length is absolutely the most important measurement (well documented in Drayson’s book), yet we typically don’t even measure it anymore.

So that bull with the large factory and wide shoulders is looked upon as the best one you bought, and he probably is. When it is time for him to mate with the cow, he is all business and nothing is getting in his way. He has already bested the other bulls in the pasture and there is work to do. If he is TOO much shorter than the cows (target laid over at a forty-five-degree angle) and the vulva is sloped forward (now the target is eighty to ninety percent smaller), it is increasingly hard to hit the target. But his instincts say go for it, and he misses the target. You can picture in your mind’s eye why he is the one who winds up with a broken tool. He quite possibly could have bred those frame-seven heifers, but the mature frame-seven cows were “A Bridge Too Far.”

A better scenario would be to go to a mature frame-score 5 bull to breed your cows, and use the fifteen-month-old frame-score three or four bull on the replacement heifers. To get rid of those sloped vulvas, make sure there is no raised-tail process in the bull. Better yet, a rounding down from the hook bones to the back end with plenty of slope from hook bones to pin bones would make the transformation even more rapid.

Why should we be looking for this different bull in the first place? Large, long, tall cows with the reverse-wedge look do not thrive, do not breed back, and generally cost a lot to supplement to have any chance of surviving, let alone thriving, in an all-grass environment.

*Epigenetics: the study of heritable changes in gene function that do not involve changes in DNA sequence

Posted on May 6, 2019 .