As a cattle producer, you are constantly managing to give your herd the best chance at production, health and well-being. Unfortunately, an unseen obstacle can be working in the background to derail your efforts: internal parasites.
Parasitism often cannot be diagnosed with the naked eye, but it undermines herd productivity and health in big ways. Internal parasites thrive in the cow’s gut, decreasing feed intake and robbing nutrients that should be going toward growth, reproduction and immune support.
How do you combat this unseen threat quietly robbing your herd of performance? Simple diagnostic tools, such as FECRTs, let you see what’s really happening inside the animal. Combined with parasite surveillance data from across your region and the country, these insights give you a clearer picture of how your current deworming program is working, so you can build a smart, targeted deworming plan that protects herd health and your bottom line.
Using FECRTs to assess the herd
When we look at testing for parasites within our herds, there are two common approaches.
The first is a composite fecal egg count (FEC), which provides a snapshot in time. Producers take 20 random, fresh fecal samples from the ground in a pasture, feedyard or backgrounding operation. These samples are golf ball-sized, individually bagged and sent to the lab to evaluate overall parasite load for that group.
The second approach is the FECRT, which determines dewormer effectiveness. Twenty samples are taken before deworming and 14 days after deworming; 20 samples are again taken from the same group of cattle. We compare pre- and post-treatment egg counts to determine how effective our deworming program was.
FECRTs are the best tool to assess if the current deworming program is working in your herd. A successful deworming should result in a 90% or greater reduction in parasite eggs in feces – but not all dewormers will deliver that result. FECRT data can identify reduced efficacy or resistance within the herd, giving you the ability to change your deworming protocols and stay ahead of parasites.
FECRT results seen across different states
The largest database of FECRT results actively monitors the field efficacy of cattle deworming products in the U.S. The database includes results from all major dewormer forms – oral, feed products, pour-ons and injectables. Results from the database show pour-on and injectable dewormers (macrocyclic lactones) average around 60% efficacy, while oral and feed products dewormers (benzimidazoles), including fenbendazole, were approximately 98% effective.
Extension services in Florida, Missouri and Kentucky have taken a closer look at how major dewormer classes are performing through on‑farm field surveillance studies.
Kentucky: Data from FECRT collected from 79 herds showed that dewormers in the benzimidazole class achieved a 99% reduction in parasite egg counts in both cows and calves. Macrocyclic lactone dewormers, when used alone, resulted in a 73.7% parasite egg reduction in cows and 63.5% reduction in calves. When benzimidazoles and macrocyclic lactones were used together, the 90% reduction threshold was met.
Missouri: FECRT from 51 herds indicated reduced efficacy for macrocyclic lactones, with egg reductions of 69.4% in calves and 80.1% in cows. In contrast, benzimidazole‑class dewormers met the greater-than-90% efficacy threshold in both age groups. Injectable and pour‑on macrocyclic lactones performed similarly, with reductions of 70.7% and 72.7%, respectively.
Florida: Florida researchers reported comparable findings from FECRT collected across 35 herds. Dewormers containing benzimidazoles reached the 90% reduction benchmark, while macrocyclic lactones used alone did not.
Together, these findings from on‑farm surveillance across multiple states indicate that dewormer efficacy can differ by class under real‑world conditions.
Use strategic timing to make the most of your deworming program
Using FECRT data to choose the best dewormer for your herd is only the first step. Timing, frequency and seasonality all factor into a successful deworming program. For cows, the ideal deworming program is:
- Before spring turnout if they weren’t treated in the fall
- Six to eight weeks after turnout to interrupt the parasite life cycle
- Again in the fall after cattle come off pasture or after the first frost
Calves are more vulnerable to parasites since they lack prior exposure. Deworming in the summer while they are still on the cow six to eight weeks after turnout is a strategic way to protect health and gains.
A research study compared weight gain, fecal egg counts, parasite enumeration and pasture larvae counts over a 99-day summer grazing period of steers on pasture that were strategically dewormed versus a control group.
Steers were randomly assigned to one of two treatments:
- A control treatment with fenbendazole suspension and moxidectin pour-on on day zero
- A strategic deworming treatment with fenbendazole suspension and moxidectin pour-on on day zero, plus fenbendazole pellets on days 29 and 59
Strategically dewormed steers gained an average of 17.1 more pounds over the 99-day study and saw an improved average daily gain by 0.18 pound per head per day compared to control steers. Considering today’s market prices, this could result in $45 to $49 per head increase in revenue.
Fecal egg counts were significantly lower following the treatments on days 29 and 59. At the end of the study, adult gastrointestinal worm counts were 12 times lower in strategically dewormed steers compared to control steers.
The study also evaluated pasture larvae count, showing that pasture management can help disrupt the parasite life cycle. As cattle shed internal parasite eggs in their manure, the eggs hatch and progress through several larval stages until they reach an infective form.
Animals were maintained in the same pastures throughout the course of the study. Multiple treatments with 0.5% fenbendazole pellets on pasture resulted in reduced pasture larvae contamination. Pasture nematode larval contamination was reduced by 61% on day 84 and 33% on day 99 in pastures grazed by strategically dewormed steers.
Feed formulations save time and labor
The good news is that you can achieve similar benefits in your herd without added time or labor. There are easy deworming options that don’t require a trip through the chute. Using feed forms of dewormers – such as those found in range cubes, dewormer blocks or pellets – require relatively little time and labor while still being highly effective.
Accurate dosing is critical, not only to give the dewormer the best chance of working effectively but also to help reduce the development of resistance. It is important to follow the label directions carefully and feed the proper amount required for the total number and weight of the cattle being treated.
Evaluate your dewormer efficiency
If you’re not on guard, parasites will decrease your herd’s productivity. But the tools available can help shed light on how parasitism impacts your herd and ensure the best plan is in place. Work with your veterinarian to do FECRT testing annually. It is a simple, reliable method to assess efficacy. Work with your veterinarian to assess your deworming program and ensure you are getting maximum efficacy from your dewormer.
References omitted but are available upon request by sending an email to the editor.
