attlemen have a wide range of legitimate concerns when buying replacement bulls and birth weight tends to be near the top of the list, as it should. But statistics may not always be as
reliable an indicator as one is led to believe by presumed industry standards.
Many of these numbers are used to produce expected progeny differences (EPDs). And I should acknowledge at the start an inherent dislike toward the EPD program. While there clearly are many breeders who base their decisions around EPD values, virtually to the exclusion of everything else, we were never part of that group. It was impossible for us to accept that a gal on a computer six hours away who had never seen a Pine Meadow animal had a superior grasp of our own herd’s genetic potential.
Breeders looking for a bull that raises the odds of having sons and daughters that look more like him than the average should consider a line-bred product. In people the results of genetically related matings are known as inbred. In cattle they are more acceptably labelled “line” or “double” bred. These cattle are relatively rare since such crosses harbour a high potential for disaster but where they work they seem to work exceptionally well.
We found some of our very best cattle were the offspring of first-generation sire-based sons and daughters. If a breeder’s herd is relatively clear of genetic imperfections those line-bred genes will be reinforced and additionally expressed in calves of the following age group. Conversely if there are cracks in the foundation of such genetics you will know this soon enough but at least a breeder has the comfort of knowing there are unwanted features in those particular blood lines he or she likely wants nothing to do with when developing a long-term herd sire.
A high birth weight calf out of a low birth weight bull does not necessarily signify pervasive problems to come. It may just be the result of that particular mix of genes, nothing more. It does not detract from the value of the bull, it merely reinforces what we already know — calf birth weights can’t be programmed precisely.
Any recorded birth weight in isolation doesn’t mean a lot other than to identify the range of weight possibilities from an identifiable bloodline. I have long felt that birth-weight records should be grouped in 10-pound segments rather than pretend present scale readings are precise to the pound. This would be a much more realistic number than most of those currently in use.
A key factor impacting birth weights, that few buyers think to ask about and even fewer breeders seem to know, is the length of gestation. In the latter stages of pregnancy a fetus can gain anywhere from one to two pounds per day in the womb. If delivery is a week early or late the difference in birth-weight statistics can be relatively enormous . Select ing one calf from a pen of peers based on birth-weight comparisons alone has significant negative potential if you don’t know the gestation period.
Virtually every seed stock producer will harvest a new calf crop this year that is surprisingly inconsistent in birth weights. When sele ting bulls a fair question to ask is the range of weights from each male’s progeny that year. It needs to be the current year — calf weights vary substantially year to year even if all other aspects are presumed to have remained the same.
You likely won’t get this number. Most breeders don’t have it. But it can readily be calculated and should be. To avoid potential problems the top and bottom weights should be disregarded in whatever percentage brings comfort to the buyer. If the average weight is, for example, 85 then there should an identifiable grouping of calves at that number plus or minus a few pounds.
The lowest birth-weight bulls should be selected as much by visual as other considerations. If the calf is a week early you will gain nothing genetically — the full term 85-pounder suddenly becomes a very desirable 75-pounder without genetic modification. If it was a twin you are buying genetics not expressed in that bull but which remain the average for that sire. If this bull breeds close to true he will follow his peer group average in the size of calves sired by him rather than following his own weight.
There are reasons cows deliver off schedule — anything from illness to fighting will bring on early calving and to hail this result as potentially heritable may be stretching the possibilities a tad.
The other pervasive problem in selecting a low birth-weight bull is determining not only when each calf is weighed but how. Few buyers seem to question the accuracy or consistency of the scale. They may well be precise at 40 pounds but are they equally proficient at a hundred? Spring-loaded scales are notoriously inconsistent and recorded weights to the pound from a bouncing calf on such an instrument are not easily confirmed.
Others stand on a platform holding the calf while someone else works the bar. The scale itself is likely close to 100 per cent accurate but the person holding the calf can vary in weight with the time of day and their clothing. Unless he/she is weighed each time, as well, the end number can be off true by a substantial percentage.
Timing is another factor. Much as we all like to declare taking a newborn’s weight is our first priority the reality is likely much more diverse. Invariably other things are going on in the barn and the yard so the calf will likely be weighed in the order of convenience, not sooner. The temptation to discount scale weight to compensate for such tardiness and further to err on the side of making the number look better rather than worse, are natural tendencies that create errors.
Breeders working off the farm have to make the same type of adjustments, when they weigh the calves born while they were away at work
Then there are the people who are confident enough to guess at calf birth weights. You will see those numbers rather frequently in sale catalogues — 100, 105, 110 — very consistent, but the reliability may seem vaguely suspicious.
My suggestion would be to pick the bull you like, check out his mom and dad, examine his half brothers and sisters, and depend on your eyes, accumulated experience and judgment. A “feel” for something may be an unconscious warning or endorsement, but either way should not be ignored. If you have even a vague emotion of doubt don’t buy. There are other bulls.
You know what a good bull should look like at a particular age — his positive features will remain and today’s negatives will only get worse. If he has a sagging back line don’t expect that to change. If he’s rubbery now that’s how he is. If he wiggles when he walks that won’t straighten itself out — if he has corns they won’t magically disappear when you get him home, and if he has testicles you can’t see without a floor mirror — keep looking around. There are good bulls out there in all weight ranges — just be certain as possible that when you are buying a bull based on birth weight you don’t over value numbers on the card.