Infrared thermography could be a big aid in ensuring a bull's potency in the field.

Even a bull that passes his BSE (breeding soundness exam) with flying colors occasionally won't get the job done when he actually goes to work. In fact, work done at the Meat Animal Research Center (MARC), Clay Center, NE, indicates that as many as 25% of these bulls have physiological problems that limit their effectiveness.

Soon, however, there's expected to be wide availability of a technology that can help maximize the chances that bulls with good transcripts can also get the job done in the real world.

A More Practical Version The technology - infrared thermography - isn't new, but it's expected to become much more practical and affordable than the cumbersome and expensive commercial units being used today.

A number of companies are working to develop portable versions of the infrared units long used by law enforcement and the military to detect missing people in the wilderness or fix locations of humans in a hostage situation. It's also commonly used in the medical profession to diagnose circulation problems in humans and, more specifically, to diagnose scrotal/testicular pathology in men.

The portable units are expected to cost around $10,000 versus the current systems which sell for as much as $100,000, says Glenn Coulter, head of the Livestock Sciences Section at the Lethbridge Research Center in Alberta, Canada. The increased affordability should serve to put the portable units within the reach of veterinarians and technicians.

Chuteside Task Takes One Minute Infrared thermography (IRT) provides a pictorial image of an object's infrared emissions - irradiated heat energy - permitting estimation of an object's surface temperature to an accuracy of 0.1 degrees C., Coulter says.

Included as part of the breeding soundness physical exam at chuteside, the IRT process (excluding analysis which is done later) takes about a minute, says Donald Lunstra, a research physiologist at MARC.

After opening the back of the chute on a restrained bull, a handheld infrared video camera is used to record images of the bull's scrotal area. A single image is taken in 11/425 of a second.

The IRT scanner converts electromagnetic infrared energy into electronic video signals. These signals are amplified and displayed as an eight-level, gray scale image and are stored on video tape for later processing and analysis by a dedicated computer. The computer has the ability to enhance images with as many as 36 colors, each representing a specific temperature range.

A scrotum, Coulter says, is an optimum subject for IRT because of its normal temperature range, lack of hair cover and its capability to radiate infrared or heat energy.

The pictorial image of the heat radiated from a normal functioning bull scrotum shows up as horizontal, parallel bands of color (see figure 1). Those bands depict the normal graduation toward cooler scrotal temperatures as you move down the scrotum and further away from the bull's body.

"In an abnormal thermograph, that parallel banding doesn't exist. Instead, you can get an infinite number of combinations and permutations of hot spots and cold spots, rather than the structured banding," Coulter says (see figure 2).

Because maintenance of a specific temperature range within the testes is essential for normal sperm production, a thermograph used in tandem with a BSE, can further confirm a properly functioning bull, Coulter explains.

Presumably, the surface temperature of the scrotum reflects the temperature of underlying structures such as the testes and epdidymides. "The adverse effects of elevated testicular temperature on sperm production, seminal quality and subsequent male fertility are well documented," Coulter says.

Thermography Test At MARC To determine IRT's effectiveness as a fertility assessment tool, Coulter and MARC's Lunstra performed thermographs on the scrotal surfaces of 73 yearling bulls.

The average scrotal surface temperature, the temperature at the top and bottom of the scrotum, scrotal temperature gradient, and thermal class ("normal," "questionable" or "abnormal" scrotal surface thermal pattern) were recorded for each bull's thermogram. Of the 73 bulls, 37 (51%) had a normal temperature pattern, while 20 (27%) had a questionable pattern, and 16 (22%) had an abnormal temperature pattern.

Thirty of the bulls, all of which had passed BSE testing and had acceptable testis size and semen quality, and represented the three thermal classes, were selected for the breeding trial. Each bull was exposed single-sire to approximately 18 heifers during the 45-day pasture breeding period.

Lowered Pregnancy Rate The results indicated that pregnancy rate was lower for bulls with abnormal scrotal temperature patterns than for bulls with normal and questionable temperature patterns. Meanwhile, pregnancy rate was related significantly to all four major characteristics (surface, top and bottom temperatures and temperature gradient) of scrotal thermograms.

The results indicated that bulls with abnormal scrotum temperature patterns had a reduced ability to maintain an effective thermal gradient from top to bottom of the testes. In addition, bulls with abnormal scrotal temperature patterns had reduced pregnancy rates in natural mating, Coulter says.

"All the bulls in this study, even those who exhibited abnormal scrotal temperature patterns, had been judged as acceptable for use as breeding sires, based on recommended semen quality and BSE criteria," Coulter says. "Thus, IRT thermography may be most useful after the elimination of potential sires that don't meet minimum soundness, testis and semen quality criteria."

Research conducted at Iowa State University, Coulter adds, found that reproduction rate is at least five times more important economically than growth performance for the average cow-calf producer.

"Thus, you can see that the beneficial effects of even small increases in pregnancy rates should not be ignored," he says.

How soon will the technology be available? "We're hoping sooner than later," Lunstra says. "A number of companies are working on it. One of those is AGA Infrared Systems in Danderyd, Sweden."

Meanwhile, Lunstra and Coulter were to begin another study in late April, this one with mature bulls.

"We'll be looking to see if we can confirm that thermography is as effective in mature bulls as it was in yearlings. If it is, it has the potential to have quite a bit of impact on our ability to identify bulls with reduced fertility. In this next study, we'll also be looking at repeatability of the thermographs," Lunstra says.

Treatment Benefits As Well What causes the "hot spots" in the scrotal images, Lunstra says, is most likely some type of injury or infection. "The animal might have been kicked or stepped on, and some inflammation resulted. It could also possibly be congenital.

"With thermography we're discovering abnormalities in the testes that we couldn't detect by palpation or tests of semen quality," Lunstra says. "Another benefit to the technology is that if these conditions can be identified, treatment with antibiotics could be administered to clear up the condition and allow future use of that bull."