To make sustained contributions to the breeding program, bulls should be structurally and reproductively sound. Sound feet and legs are essential in order for a bull to cover many acres of pasture, both for obtaining adequate nutrition and mating cows. Structural soundness is not an all-or-none phenomenon; rather it is expressed in various degrees. Bad feet, pigeon toes, excessively straight or sickle hocks, and loose or pendulous sheaths are examples of some of the more common structural problems of bulls. Because many structural problems become worse as bulls grow older and heavier, it is particularly important to critically evaluate young bulls.
Structural soundness of bulls that are candidates for selection should be evaluated in a systematic manner. Inspect each bull‘s feet, toes, heels, pasterns, knees, hocks, and sheath. When viewed from the front, the feet should point straight ahead, both when the bull is standing and walking. The feet should be large and round with a deep heel and with toes that are similarly sized. When viewed from the rear, the legs should be equally far apart at the hocks and pasterns and then toe out slightly from the pasterns to the ground. The bull should move freely with each hoof striking the ground evenly.
Many structural problems are partially heritable and should be particularly discriminated against when daughters will be kept for replacements. However, structural problems that do not compromise longevity or ability to service cows are of little consequence in the selection of terminal sires.
Evaluating bulls for structural soundness also provides an opportunity to gauge a bull‘s temperament or disposition, a moderately heritable trait. A bull with poor disposition may be dangerous or difficult to work, and his daughters may be difficult to manage as well.
Replacement Female Selection
Many of the concepts involved in the selection of sires are equally appropriate to selection of replacement females. In general, female selection is less intense than selection of males and accuracy is usually greater for proved bulls. Therefore, most genetic progress results from sire selection. From an economic perspective, selected replacement females should calve first at two years of age, reproduce annually thereafter, and remain in the herd for an extended period of time.
Beyond the ability to reproduce annually, replacement females should remain functionally sound to advanced ages. Proper foot, leg, and udder structure is important. A cow’s udder should be well attached, level across the bottom, and have small to moderate sized teats that are not excessively long. In general, soundness of the udder deteriorates with age.
Cow Culling Decisions
Removal of cows from he herd is largely an economic decision, because it has limited influence on genetic improvement. In most cases, it has been recommended that nonpregnant cows routinely should be culled. Functionally unsound cows should almost always be culled. Cows with impaired mobility or unsound mouths are unlikely to harvest sufficient nutrients to maintain body condition and be productive.
Seedstock breeders typically select replacement heifers from within their own herds as opposed to purchasing heifers from other breeders. This has the advantage of utilizing the same genetic resources that produce their marketable bulls. Selection of replacements is a multi-stage process and is similar to any other selection scheme for females. However, it is important to note that the quality of sires used to produce the heifers will greatly impact the genetic potential of future calf crops.
Heifers should be culled for structural problems that may interfere with their ability to raise a calf, breed back, and have a long productive life.
Edited from Morris Halliburton