What is a heifer bull?

Answer 1

Heifers have smaller pelvic areas than mature cows do, so they need to be bred to a bull that has, genetically, low birth weights. Heifers are also best bred to yearling bulls(primarily 12 to 18 months of age), which are smaller than the bigger mature bulls and won't increase the chances of crippling the heifers when trying to mount them. Young and/or small bulls tend to have the genetics for siring smaller calves, and heifers have the body size that tend to develop small calves, however, in either case this does not always occur: Yearling bulls are primarily unproven bulls; small bulls may sire large calves; Breed of the yearling bull plays a part in low birthweight genetics; condition, feed and environment play a role in lowbirthweight rates in heifers and cows.

Young bulls are not the best because 99% of the time they are unproven sires. In other words, they are virgin bulls, or have never mated with a cow or heifer and produced offspring. They are selected by the rancher because they are expected to produce low birthweight calves out of the heifers, only because the Expected Progeny Differences (EPDs) combined and calculated from the sire and dam, and compared with other bulls of the same breed and raised in the same conditions, says so. Smaller bulls also need to have the EPD numbers to be able to be used on heifers. If there are no papers that come with a small bull that you buy, you are making a big gamble on him. Even EPDs on yearlings are not reliable, especially if you have a 60% chance that that bull will sire large calves instead of small ones. Thus young unproven bulls may have high birth weights that should not be used on heifers; the same goes with smaller bulls.

Breed also has a large affect on how the heifers calve out, and what size of calves the bull will sire. For instance, a yearling Simmental bull is put in with about 20 Red Angus heifers. Low birth weight EPDs for the Simmental breed is different from the low birthweight genetics of the Red Angus breed, so there's a higher chance that 10 or 15 of those Red Angus heifers will need assistance. Even using a Red Angus yearling bull that may have the numbers for low birth weights may not sire low birthweight calves in all of the heifers. But, primarily using a Continental bull that is of a breed that is notorious for large calves, like Simmental, Charolais, Maine Anjou and Belgian Blue, for instance, on your heifers, is asking for trouble. Small bulls like Dexters, White Park, Red Poll, etc. tend to sire small calves that are easy for your heifers to pop out.

So heifer bulls are chosen through careful selection of genetics, size and breed, with the type of heifers in mind, in order to have a successful, worry-free calving season. If you know what to look for, you will have some happy heifers on your hands.

Answer 2

A heifer that is either in heat (going in or out of), or a hermaphordite heifer as a result of being twinned with a bull.