Wouldn't it be nice to know the gender of your calves before they're born? With fetal gendering, you can determine whether a calf is a bull or heifer in utero. Fetal gendering is a non-invasive procedure that uses transrectal ultrasound to examine a pregnant cow or heifer to determine the gender of the calf (or calf) she is carrying.

Learn about the Fetal Gendering Process

bovine ultrasound Testing

Wearing gloves, the technician gently guides the bovine ultrasound probe into the rectum of the restrained cow. The probe is positioned at the base of the rectal wall and manipulated until a clear image of the fetus is obtained. The major parts of the body (head, trunk, limbs, etc.) are first visualized to determine the orientation of the fetus. The technician then scans near the umbilical cord and under the tail to locate the hyperechoic genital tubercle.

The genital tubercle is a structure present in both developing fetuses, with the genital tubercle behind the umbilicus indicating a bull calf and the genital tubercle located under the tail indicating a heifer calf. Depending on the stage of pregnancy, the technician may also attempt to observe scrotal swelling or scrotal swelling to help determine the sex of the calf.

Ultrasound images of calf sex

Advantages of fetal sex identification

Marketability of breeding cattle

Some producers have a greater incentive to produce heifer or bull calves. For example, in the dairy industry, the market for heifers is often much stronger than for bull calves, while for commercial beef producers, bull calves may be more valuable than heifers. Therefore, when breeding females are sold, their value in a particular market may increase significantly when the sex of the fetus is known.

Easy management

Knowing how many bull and heifer calves to expect at calving can help producers jump-start future plans. A producer who keeps his own breeding females can understand whether he needs to budget for additional replacements. For a cattleman who markets bulls, he can begin negotiating and filling bull contracts earlier. When a purebred breeder sells a flush that guarantees a minimum number of pregnancies to a specific sex, fetal sexing of the calf carried by the recipient will let her know if the agreement has been fulfilled or if the donor needs to be sexed again.

Important Considerations for Fetal Sexing

Time Frame

While fetal sexing can provide valuable information to the cattle producer, there is a limited window of time in which it can be performed. Because the genital tubercle begins to migrate around day 50 of gestation, it is impossible to differentiate between male calves and heifers by ultrasound before this time. The earliest that any degree of fetal sexing can be performed is day 55, although many technicians advocate waiting until the genital tubercle has completed migration around day 60 of gestation. On the other hand, fetal sexing usually needs to be completed before day 90 of gestation. Beyond this point, the fetus is usually too deep in the abdominal cavity to reach with an ultrasound probe or is too large to obtain a satisfactory image. While fetal sexing can be determined beyond 90 days, it is a gamble whether sexing can be determined.

Accuracy

The accuracy of fetal sexing is primarily attributed to the time frame in which sexing is performed and the skill and confidence of the technician. When performed by a skilled technician between 60 and 90 days of gestation, the accuracy of fetal gender determination should be at least 95%.