21 May 2007

3 minute read

Heifers culled on the basis of pelvic area, average daily gain, reproductive tract scores, disposition, or structural soundness at the time of the prebreeding exams and finished in a feedlot had a 3-year average net profit of $9, whereas heifers diagnosed as nonpregnant shortly after the breeding season were sold for a net loss of $86. The loss for pregnant heifers that were then diagnosed nonpregnant after wintering on native pasture and sold at a sale barn was $133. These figures indicate the importance of identifying heifers that will not breed during the breeding season and culling those heifers before they become an economic liability. Heifers that were diagnosed pregnant during the breeding season were allocated to three groups: first-service AI, second-service AI, or natural mating. Average profits were $163 for first-service AI heifers, $139 for second-service heifers, and $83 for heifers naturally mated. These figures take into account all synchronization costs. Therefore, the advantage of AI over natural mating is certainly evident from these analyses, but without sound data these results could not have been noticed. In fact, many people would (and still do) shy away from AI because of the initial costs associated with synchronization, management, and an AI technician. Nonetheless, these results would encourage a producer to seriously consider AI, realizing that the profit potential is far greater than just using natural mating.

FERTILITY: Heritability estimates for fertility (pregnancy rate) are relatively low (.00-.10). However reproductive rate is so economically important it cannot be ignored. Culling heifers that fail to conceive within a set breeding season should enhance cow herd fertility.

CALVING EASE: The birth weight of the calf relative to the dam's pelvic area can be a primary determinant of calving difficulty. As a rule of thumb, bulls having birth weight EPDs within the 15th percentile of their breed can usually be considered calving ease sires.

MILKING ABILITY/FLESHING ABILITY: Within a breed, the most effective way to alter milk production is to use milk EPDs for sire selection. For the commercial producer the easiest way to increase milk may be to crossbreed with a sire from a heavy milking breed. Fleshing ability can be related to milking ability. An optimum body condition score would be 5-6 on a 1 to 9 scale.

TEMPERAMENT: The heritability of temperament is .15-.40. Cull heifers having poor dispositions because they create problems in the rest of the herd.

MUSCLE THICKNESS: For most producers, selecting heifers that avoid extremes will be optimum.

STRUCTURAL SOUNDNESS: Overall structural soundness effect longevity. Some areas to evaluate are the feet, legs, eyes, jaw, and mammary system.