DIAGNOSTICS FOR BETTER CATTLE PERFORMANCE
By Dr. George A. Perry Texas A & M AgriLife Research and Extension Center
As the cost of production increases, the importance of maintaining the cow herd also increases. Research has indicated it takes the net revenue from approximately six calves to cover the development and production costs of each replacement heifer; thus, any cow that misses a single calf is not likely to recover the lost revenue of that missed calf. Therefore, longevity of a beef female is important to the sustainability and profitability of any beef operation, and reproduction is the main reason for animals leaving the herd. Understanding available diagnostic tools to improve the performance of your herd will help improve longevity and reproductive efficiency.
This article will focus on four areas in which diagnostic tests can be utilized to improve the performance of cow-calf operations. Disease Testing
Bovine Viral Diarrhea Virus( BVDV) costs the U. S. beef industry $ 1.5 to $ 2.5 billion annually and is the leading cause of morbidity in the cattle industry. Prevalence of BVDV is around 16 % of cattle worldwide, but in the U. S., it is less than 1 % of the cattle population. However, it is estimated that at least one animal infected with BVDV is present in ~ 16 % of herds, and presence of an infected animal for cattle entering a feedlot is around 0.3 % at arrival, 2.6 % in chronically ill cattle, and 2.5 % in dead cattle.
The main method BVDV can enter a herd is through new animals, likely animals that are purchased( bulls, replacement heifers, cows and especially bred cows / heifers). Pregnant females more than doubled the likelihood of bringing BVDV into the herd, but testing animals decreases the likelihood of introducing BVDV into your herd by half. One of the main things to remember with pregnant females is, even though the dam may be negative for BVDV, the calf in utero could be infected. At time of birth, it needs to be considered a new animal in your herd and tested before exposure to your resident herd to avoid possible exposures. Fertility Testing
Any single bull affects the genetics / future of a herd in a much greater proportion than a single cow, as half the genetic makeup of every calf a bull sires comes from him, and loss in fertility results in the loss of a potential calf crop.
Carrying out a breeding soundness examination( BSE) is an important exercise to identify potentially sub-fertile and / or infertile bulls and to avoid the resulting economic losses. These examinations are conducted by veterinarians and should be performed four to six weeks before the breeding season each year. This allows for time to retest a bull when a deferred classification is given, or time to find a replacement if the bull is considered unsatisfactory. The components of a breeding soundness examination include 1) scrotal circumference measurement, 2) sperm motility, 3) sperm morphology, 4) testicle palpation, 5) palpation of seminal vesicles, and 6) observation of physical problems. Pregnancy Testing
Every missed estrus is equivalent to three weeks of production lost waiting for that female to cycle again. Unfortunately, there is no early pregnancy test that is 100 % accurate. Transrectal ultrasonography is considered the gold standard in early pregnancy diagnosis, but equipment is expensive, and proper training is required to accurately be able to diagnose early pregnancies. Our laboratory recently compared multiple blood pregnancy tests to transrectal ultrasonography to determine how accurate they are( see table). All tested pregnancy tests had good comparisons with each other and with transrectal ultrasonography. Thus, there are options to determine pregnancy status as early as 28 days after insemination without the need for expensive equipment and / or training.
When calves are weaned at a single time, the variance in which calves are born has a large impact on the pounds of calf weaned, with age-of-calf being the single largest factor affecting weaning weight. The ability to determine pregnancy early also allows for determining not only which cows conceive early in the breeding season but also allows monitoring of any embryonic loss occurring. Embryonic loss can be a signal of disease or other management related issues. Thus, knowing who is pregnant early in the breeding season and any losses that might be occurring helps give early insight into problems before they become large issues. Parasite Testing
Dewormers( anthelmintics) have been used for years to improve the health and performance of cattle. The misuse of these dewormers, however, can inadvertently lead to a large population of resistant parasites, making dewormers less effective for parasite reduction. The two most common classes of dewormers are benzimidazoles( Synanthic ®, Safeguard ®, Panacur ®, Valbazen ®, etc.) and macrocyclic lactones( Ivermectin ®, LongRange ®, Cydectin ®, Dectomax ®, etc.).
Many producers deworm their entire herds several times a year with the same dewormer. While the intention behind this practice is to eradicate the parasite population within the herd, many times this practice can cause more harm than good. This is due to treating cattle that may not require treatment, and / or using a dewormer that has low efficacy within a herd. Over time, dewormer resistance can increase within a pasture and / or herd. Through continuous anthelmintic treatment with the same compound, susceptible parasites are killed off, leaving only resistant parasites behind. This leads to larger numbers of resistant parasites, which can pose a problem for producers.
To determine whether anthelmintic resistance exists in your herd, testing its efficacy is important and can help avoid the development of resistance. Fecal samples are collected pre-deworming and 14 or 28 days post-deworming( 14 days for benzimidazoles and 28 days for macrocyclic lactones), and a fecal egg count is performed on each sample to determine parasite eggs per gram of feces( EPG). Resistance is calculated using this Fecal Egg Count Reduction Test( FECRT): % resistance =( post-treatment EPG- pre-treatment EPG) /( pre-treatment EPG) x 100. Conclusion
By implementing specific diagnostic tests, you can reduce the possibility of bringing diseases into your herd, increase the likelihood of a successful breeding season, identify animals that conceive early in the breeding season, and avoid developing resistance to anthelmintics. Each of these diagnostic tests is easily implemented in your cow-calf operation and will help avoid reproductive wrecks that can occur.
12 APRIL 2025 www. NCBA. org
Test
Agreement, %
False Positive, %
False Negative, %
Samples, n
Ultrasound: Lateral Flow 92.38 5.61 2.00 2,744 Ultrasound: RVPT 90.73 6.46 2.80 1,533 Ultraound: RPT 92.61 5.91 1.48 2,436 RVPT: Lateral Flow 95.07 3.56 1.37 1,460 RPT: Lateral Flow 96.22 1.31 2.46 2,360
RPVT: RPT 97.36 1.80 0.83 1,443
Ultrasound = transrectal ultrasonography Lateral Flow = IDEXX Alertys OnFarm Pregnancy Test
RVPT = IDEXX Alertys Rapid Visual Test RPT = IDEXX Alertys Ruminant Pregnancy Test