A QUICK WAY TO SPOT PREGNANT HEIFERS

Pregnant heifers in the feedlot cost owners time and money regardless of how they are managed. A management program designed with input from a veterinarian can help to minimize losses and address a situation that’s not of the feedlot’s own making.

Veterinarian Andrew Bronson of BioCheck Veterinarian Diagnostics and Technologies at Lethbridge, Alta. has designed and is now marketing a new ultrasound pregnancy-testing instrument called Repro-Scan that can be used by veterinarians or trained feedlot employees as part of a proactive pregnant heifer management program. He demonstrated the Repro-Scan at the annual Western Canada Feedlot Management School hosted by the Western College of Veterinary Medicine this past summer.

Repro-Scan comes with a flexible extension arm and a detachable ultrasound scanning unit directly wired to a monitor. It can be configured to plug into a power source or with a 12-volt battery and battery charger for greater portability. Options include a head-mounted goggle display instead of the table-top monitor, and a wireless sender and receiver for mobility around the chute.

Repro-Scan can detect pregnancies as early as 35 days and up to full term. Bronson says it doesn’t take long for a person to develop a high degree of accuracy once they learn to identify anatomical landmarks and understand what they are seeing on the monitor. Sound waves bounce off of bone and solid tissue, which shows up in white on the monitor. Fluids are black because sound waves pass right though them. He likens it to star gazing. If you know nothing about astronomy, it looks like a sky full of stars; when you know a constellation and where to look for it, it’s easy to spot.

Bronson began using ultrasound technology for pregnancy checking feedlot heifers in 2003. When the U.S. border reopened to cattle under 30 months of age, all heifers had to be tested prior to export. It was gruelling physical work, he recalls. Many veterinarians develop arm and shoulder injuries from the repetitive movement of pregnancy checking during the course of their careers.

Repro-Scan is easier to use and the cost of the unit is significantly less than that of the technology he was using back then. The convex image on the or the feedlot can work with its own veterinarian. With some practice, good facilities, and a crew to keep the heifers moving through the chute, the Repro-Scan operator can check up to 100 head an hour.

THE PREGNANT HEIFER PROBLEM

The pregnancy rate in feeder heifers is highest in light, off-type yearling heifers sourced through auction markets later in the fall. This tends to be the time of year when cow-calf producers decide to cut the bottom end

Repro-Scan monitor is about 16 centimetres across and 14 centimetres deep versus the credit card size of the image generated by the linear probe. As far as Bronson is aware, Repro-Scan is the first ultrasound unit in the world with the settings pre-programmed into the software — all the operator has to do is plug it in and it’s ready to use. If there is a malfunction, BioCheck has the replacement parts on hand and does the servicing.

Using Repro-Scan is much easier than palpating, both physically and in terms of detecting a pregnancy, Bronson comments. He provides the training, which takes about one afternoon, of their replacement heifers. Bronson’s worst experience in the field was one lot of feeder heifers with a pregnancy rate of 85 per cent. Typically, it’s 10 to 25 per cent, he says.

The rate is generally lower — from two to 15 per cent — for good-quality, 850-to 950-weight yearling heifers placed in the fall. In these instances, the breeding may have occurred if a bull jumped the fence during the winter feeding period or while the heifers were on pasture. Odds are that it wasn’t a heifer bull, so the resulting fetuses will have genetic potential for heavier birth weights.

Current-year heifer calves are least likely to be bred, he adds. Still, up to five per cent of fall-placed heavy heifer calves and up to three per cent of feeder heifers placed later in the winter or spring could be pregnant, particularly when bulls have been left to run with the cows for the entire grazing season.

Aside from immaturity, the issue with bred heifers in feedlots is that they are fed to fatten rather than to be developed as replacement heifers, Bronson explains. The rate of calving and post-calving complications and death loss can be high due to dystocia, retained fetal membranes, uterine infections, uterine prolapse and calving paralysis.

The direct cost of a pregnancy in a feedlot today averages out to about $200. The losses are related to veterinary bills and drug costs to treat the complications. The death loss of a nearly finished heifer is the worst-case scenario.

There are additional costs associated with lower performance on feed and higher consumption to support the pregnancy. Income is reduced when pregnant heifers are sold on the rail because feedlots ship the heifers at a finished target weight, but the animal is actually lighter by the weight of the fetus and an equal weight of the uterus and fluids.

A PROACTIVE MANAGEMENT PROGRAM

Generally, feedlot owners either take their chances and try to manage calvings on an individual basis when they occur, or they have a program in place to mass abort all heifers, or at least the groups of high-risk heifers, Bronson explains. The failure rate of mass abortion programs is about 10 per cent and it’s usually in 120-day-plus pregnancies.

Another option is a selective program, whereby all of the heifers are pregnancy checked and only the pregnant heifers are treated with the abortifacient drugs. Traditionally, veterinarians have done the pregnancy checking by palpitation, however, it’s

not always possible for feedlots to find a veterinarian who is willing and able to do the work when it needs to be done, and it costs about the same as aborting all heifers.

Repro-Scan is an alternative for veterinarians and feedlots that will help to make proactive management of pregnant feeder heifers more feasible than it has been in the past.

Your first decision will be whether to pregnancy check and treat the pregnant heifers on arrival, or delay the procedure for two or three weeks until they adjust to the feedlot environment.

Bronson’s preference is sooner rather than later because it will be easier on the heifers when the fetuses are smaller, less feed will be wasted on the developing fetus, and it saves the time and expense of running them through the chute a second time.

Some feedlots prefer to delay the procedure because they feel that the additional stress on arrival could trigger bovine respiratory disease and that the abortifacients may interfere with vaccines administered at the same time. Other feedlots delay treatment for high-risk heifers only.

A word of caution — MGA (melengestrol acetate), which is a synthetic progestational steroid, may interfere with the abortion program. The recommendation is to discontinue feeding MGA for seven days prior to and 14 days after treatment.

Next, you’ll have to decide whether to mark the treated heifers and send them directly to their home pens, or set up an abortion pen to hold them for monitoring. An abortion pen should be separate and apart from the hospital pen, clean and well bedded. Pen space and employee availability will be the main considerations.

The home-pen advantage is that it’s quick and easy. The drawback is that it makes it difficult to closely monitor the treated heifers and you won’t really know how effective the program has been, Bronson explains. A 60-day fetus, for example, is only three inches long, so you could easily miss the evidence.

Holding all of the treated heifers in one pen makes it easier to check them regularly and frequently, assist in a timely manner, and follow up as required. Ideally, all of the treated heifers would be pregnancy checked again in seven to 10 days and those found to be still in calf would be given a second treatment.

A basic Repro-Scan unit will pay for itself after a couple thousand head relative to having a veterinarian palpate all heifers or aborting all heifers, Bronson says. Check with your provincial Agriculture Department to find out if Repro-Scan is eligible under a program for new technology.

Contact Bronson at 403-328-1844 or visit the website at www.repro-scan.com.

About the author

Comments

explore

Stories from our other publications