LOOK CLOSELY AT COWS TO CULL AND HEIFERS TO SELECT AS REPLACEMENTS

by: Lew Strickland
DVM MS DACT Interim Ext. Veterinarian Auburn University


I can still hear my daddy now "we need to keep that cow for one more lactation because she is one of our best cows and hopefully we will get a heifer from her." It didn't seem to matter that her udder was broken down and her teats protruded out similar to a hat hanger, we were going to keep her.

Fortunately, the advent of sorted semen has changed the "I hope we get a heifer" to a more certain gender outcome so that we can select the cows with better genetics in the herd for breeding. What I would like for us to take a look at is what cows to cull and heifers to select for replacements.

Proper ID

This can be as simple as a notebook or as high tech as the current electronics allow. Proper identification is the first step to performance of an individual animal and their offspring. Ear tattoos should be included with ear tags in case of an ear tag being lost. Tag and tattoo calves to match their dams and their calving dates. Some of the production records recommended are: 1) cow and calf ID, 2) sire ID, 3) calf sex, birth date and weight, 4) calving ease score, and 5) weaning date and weight.

Pregnancy Status

A producer once told me that "an open cow to a producer is like an empty well to a thirsty man." They produce expenses without providing a calf to offset the expenses. Cows that are open at the end of a breeding season should be on the top of the cull list and treated with "trailermycin."

In a natural service herd, these cows can serve as a source of venereal diseases. Cows persistently infected with trichomoniasis and campylobacterosis can carry these diseases from year to year and reduce reproductive performance and economic profitability of a cow-calf operation. Pregnancy exams can be performed as early as 26 days with ultrasound, and routine palpation should be performed 60 to 90 days post-breeding. Working closely with your veterinarian can help to identify infertility and herd health problems.

Structural Soundness

The productive lifetime of a cow varies, but as long as the cow is structurally sound she may be able to continue to contribute to the herd.

Some parameters to consider when determining soundness are:

Does she still have teeth adequate for grazing?

Is her udder healthy? No obvious signs of mastitis, balloon teats, broken suspension?

Is there any obvious lameness? Are her limbs still structurally sound?

Health Concerns

Existing disease may influence the decision to cull. These conditions are a big "strike you're out" against the animal. "Cancer" eye is one of the most common and economically significant tumors of cattle. Treatment options are available depending upon severity of the lesion. Enucleation may be necessary if the eye is not salvageable. Vaginal or cervical prolapse usually occur pre- or post-calving. These can be repaired, but get ready for a repeat performance. These commonly re-occur and have a genetic component that can be passed on to offspring.

An additional "strike" is Johne's disease. Johne's is a chronic incurable disease that is contagious, especially to offspring of the infected animal. Serological and/or fecal tests can be performed to identify the infected animal.

Replacement Heifers

A producer must have in mind a cow "type" that can produce a terminal (slaughter) animal that satisfies market requirements for carcass weight, quality grade and yield grade. Frame size, carcass weight, excessive finish (fat) and marbling ability must be major considerations in selecting replacement heifers that will make up the future cowherd.

Records/ID

Once again, a complete permanent set of records, in conjunction with a permanent identification system, is crucial in selecting replacement heifers. These records should provide information on an individual's sire and dam, birth date, birth weight, weaning weight and yearling weight. Permanent records on every producing individual in your herd, and even on those culled animals that still have offspring producing in the herd, will allow producers to identify and select females with a record of above average production. Selection is just a guess without proper records.

EPD

The selection process can begin with Expected Progeny Differences (EPDs). These are available on most major breeds of cattle, and are good predictors of an animal's genetic potential for production. An estimate of an individual's birth weight, weaning weight. Yearling weight, milking ability and. in some cases, carcass quality can be calculated from the EPDs of an individual's sire and dam.

Soundness

Similar to the cow, heifers must be structurally correct as well. Length and depth of body, femininity and sound feet and legs are important criteria for selection. Replacement heifers should be chosen out of cows that do not have teat and udder problems.

Sire and Dam Traits

Selection of daughters from bulls with a large scrotal circumference is beneficial as well. Research shows that the daughters of bulls with a large scrotal circumference tend to reach puberty at an earlier age than do the daughters from bulls with smaller testicles. For a closed herd, all genetic progress is made through bull selection or replacement heifer selection.

Select replacement heifers from those born in the first part of the calving season. These heifers will be older, and they will be larger. These heifers should breed readily because they will be more mature at the beginning of the breeding season. Cows that are more fertile usually calve earlier in the season and tend to pass this fertility level on to their daughters. Coupling this female selection characteristic with selecting bulls with large testicles will improve fertility in your females.

Pelvic Measurement

There is no guarantee a heifer with a certain pelvic measurement will calve without any problems, but these measurements can be used to cull heifers with smaller pelvic measurements. Average pelvic measurement figures are about 155 to 160 cm-squared as a minimum for a 12- to 14-month-old heifer. Heifers with less than 160 cm-squared are more likely to experience dystocia than those meeting this minimum standard. An additional tool for selecting heifers is scoring reproductive tracts against a standard. Tracts are evaluated for size, tone and ovarian activity. This examination identifies heifers that have and have not attained puberty.

Conclusion

In summary, there are several key factors that are crucial for the selection of productive, high-quality females. These factors include:

Permanent records are essential.

EPDs help to predict an animal's genetic potential for production.

Do not get calves too fat at any time between birth and their initial breeding season. Fat deposition in the pelvic canal leads to dystocia.

Replacement heifers need to gain 1 to 1.5 lbs. per day from weaning time to breeding.

Structural soundness is a must for longevity.

Select heifers based on sire and dam traits.

Replacement heifers should meet the standards of pelvic measurement and tract scoring.







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