Increase Profits by Deworming Your Nursing Beef Calves

Recent research refutes revered dogma regarding parasites.

By Steven E. Wikse, DVM, DACVP
Robert W. Field, DVM
Thomas M. Craig, DVM, PhD
Patricia S. Holland, DVM, MS
Kerry S. Barling, DVM, PhD
and Robert E. Toombs, DVM, MS (deceased)
Departments of Large Animal Medicine and Surgery (SEW, RWF, PSH, KSB) and Pathobiology (TMC), Texas A&M University, College Station, Texas

          Standardized Performance Analysis (SPA) of the financial performance of beef herds by agricultural economists shows the profit margin of cow/calf operations in Texas is very low.   Implementing management practices that have a positive benefit:cost ratio can improve that profitability.

Parasitologists at Texas A&M University have long recommended control of gastrointestinal (GI) parasites by periodic treatment of cattle with anthelmintics. Their standard recommendations were to treat cows once or twice a year and to treat beef calves at weaning.

The old dogma was calves did not build up a high enough level of parasitism worth treating until they were weaned. However, field trials conducted by the authors of this article have eliminated that dogma. We have identified a new opportunity to increase the profitability of beef cow/calf operations: We have demonstrated that heavier weaning weights result from treatment of nursing beef calves for GI  parasites.  

Parasites are everywhere

            Cattle in all geographic areas of Texas are infected with GI parasites.

The Gulf Coast and East Texas are considered parasite heaven; however, even calves in West Texas carry parasitic burdens capable of impairing growth.  

The GI parasites common in Texas calves are species of Ostertagia and Cooperia.   Ostertagia ostertagi, the “brown stomach worm”, resides in the abomasum and is considered the most damaging of all GI parasites. 

The three species of Cooperia, C. oncophora, C. punctata and C. pectinata, live in the small intestine and are less pathogenic than Ostertagia.

When combined with Ostertagia, however, Cooperia infection can become very detrimental.

Reduced growth rates -- “Hidden Losses”

            GI parasitism is sometimes called a “production disease” because it can lower production in cattle that have no signs of being ill.  

Signs of GI parasitism in calves (diarrhea, dilute/rough haircoat, stunting) only occur with heavy infections. Most calves with GI parasitism have no obvious signs, but “hidden losses” result from reduced growth rates which result in lower weaning weights.    

Parasitic infections have a potent two-pronged impact that reduces growth rates of calves: 1) digestion and absorption of feed is impaired; and 2) calves ingest less feed due to appetite suppression. 

The decrease in appetite accounts for 70 percent of the reduction in growth rates of parasitized calves (Photo 1). This recent research is shocking news.  

There was an old dogma that you don’t need to deworm cattle when you have plentiful pastures because you have enough nutrition to feed the cattle and the worms. 

Another dogma has been buried! Parasitized cattle will ingest much less of that plentiful pasture. Actually, instead of getting little benefit from deworming cattle when feed is abundant, that’s when you will get the greatest benefit from your deworming program.

Bonus benefits of deworming

There are bonus benefits from deworming of nursing calves in addition to heavier weaning weights.

Ostertagia ostertagi has been shown to inhibit the immune response of calves. The impairment of immunity is specific for Ostertagia to aid its establishment in the calf’s body, but also acts as a general inhibition of immunity against any organism.  

This indicates that calves with untreated Ostertagia infections are more susceptible to infectious diseases such as pneumonia. It also suggests calves with untreated Ostertagia infections have a reduced ability to respond to vaccination.  

Also, sheep with Ostertagia infections can absorb copper only half as well as those treated for Ostertagia. The same, no doubt occurs in calves. This has the potential to decrease the resistance of calves to infectious diseases because they need copper for a strong immune response.  

Thus, Ostertagia infections impair the immune system of calves through two mechanisms and control of Ostertagia will enhance their resistance to infectious disease.

Texas research trials

          Over the past 20 years, clinical trials conducted by the authors in Texas beef herds have demonstrated that treating nursing calves and their dams for GI parasites will increase weaning weights.  

Most of the trials were carried out in spring-calving herds in central and South Texas. Various anthelmintics were used, including doramectin (Dectomaxâ, Pfizer Animal Health), fenbendazole (Safe-Guardä/Panacurâ, Hoechst-Roussel), and ivermectin (Ivomecâ, Merial).

Cow/calf pairs were randomly divided into two groups; a non-treated group and a treated group. An anthelmintic was administered to calves and dams in treated groups. Treated and untreated pairs were pastured together in some trials and placed on separate pastures in others.

Treatments were usually given in May, June or July when the average weights of groups of calves ranged from 200 to 350 pounds. Fecal worm eggs per gram (EPG) were performed on calves at the start of each study.

Weaning weights were greater in the treated calves in 11 of 12 trials. The advantage varied from eight to 46 pounds with an average of 25 extra pounds for the treated calves for the 12 trials.  

Treated calves gained an extra 0.10 to 0.20 pounds per day. Using any of the above anthelmintics increased growth rates of calves; however, in the few trials where two anthelmintics were compared on the same ranch, we did see differences in their effect on calf growth. 

Macrocyclic lactones had the greatest benefit, probably due to their persistent killing activity.

An interesting finding was that greater increases in weaning weights were found in calves with young dams. One study resulted in average improvements in calf weaning weights of 19 pounds for four-year-old dams; 38 pounds for three-year-old dams; and 57 pounds for two-year-old dams.

The average fecal EPG of the treated calves had no relationship to their growth rates. A group of calves that had 41 pounds increase in weaning weights from treatment had an average of only three fecal EPG in July at the beginning of their trial. 

Guidelines have been published listing how high fecal EPG should be before a significant benefit can be expected from deworming of nursing calves. We and researchers at other universities agree there is no need to perform fecal EPG counts to decide whether to deworm nursing beef calves. They will all be parasitized and they will all benefit from being treated. 

Texas ranch results

The Texas Beef Partnership in Extension Program (Beef PEP) is a cooperative effort between the Texas A&M University College of Veterinary Medicine, Texas Cooperative Extension Service, Texas veterinary practitioners, Texas cow/calf producers and Pfizer Animal Health.  

Pfizer Animal Health and the College of Veterinary Medicine provide funding for the project and Pfizer Animal Health donates animal health products used in study herds. The purpose of Beef PEP is to enhance the profitability and sustainability of Texas cow/calf producers. 

The project has completed three years of work in six beef herds. The main goal in the study herds was to reduce the cost of production by implementation of profitable ranch management practices.

Instead of a formal research trial focusing only on the impact of deworming of nursing calves on weaning weights, the practice was added to multiple new management practices implemented together in the herds.

None of the herds had been deworming nursing calves before the study. Five herds added the practice. Four of those five herds had been deworming cows at least one time a year before the project. 

The five herds that implemented deworming of nursing calves along with many other management changes had an average increase of 88 pounds in weaning weights (Photo 2). We felt that the practice of treating nursing calves for GI parasites accounted for a considerable part of the dramatic increase in weaning weights in the herds.     

Deworming of nursing calves

            The seasonality of transmission of GI parasites makes timing of deworming treatments critical for successful control programs.

Ostertagia ostertagi is only transmitted during months when temperature and moisture conditions of pastures are favorable for survival and maturation of its larvae. Favorable conditions in Texas usually occur in the spring (mid-March, April, May and mid-June) and the fall (mid-September, October and mid-November).  

Greater parasite numbers are acquired by calves in the spring than the fall. Some transmission can also occur in winter months if weather is mild.  

Transmission of Ostertagia is minimal during the “summer brownout” (June, July and August), but Cooperia spp. are transmitted to calves during that period.  

Contamination of fall pastures with Ostertagia results when larvae that survive the summer brownout by remaining in an arrested state in the abomasum emerge into its rumen and mature into egg-laying adults. 

In Texas, the single most important time to treat cows and calves for GI parasites is just before the summer brownout. If treatment is given too far in advance of the summer brownout, the animals will become re-infected; if treatment is given after the summer brownout has started, the calves will have fewer days of increased weight gain before weaning. 

It’s very important that the anthelmintic used for that treatment kills adult worms and nearly 100 percent of larvae arrested in the abomasum so cattle enter the summer brownout period free of both adults and arrested larvae. This will help maintain the appetites of cattle during poorer grazing of summer and minimize the amount of transmission of Ostertagia in the fall.  

          There are two classes of commonly used anthelmintics (Table 1); benzimidazoles, which are white liquids or pastes administered orally, and the newer macrocyclic lactones which are administered by injection or pour-on.  

Table 1 – Anthelmintics commonly used to deworm calves and their dams

* No label claim             

Although both classes kill nearly 100 percent of adult worms, there are important differences in their activities. The macrocyclic lactones kill nearly 100 percent of arrested larvae and have variable numbers of days of residual killing power following treatment while the benzimidazoles kill approximately 20 to 95 percent of arrested larvae and have no residual killing power.  

Treatment with macrocyclic lactones resulted in greater improvements in calf growth rates than benzimidazoles in our trials. In addition, residual killing properties of macrocyclic lactones allows the treatment date to be scheduled somewhat in advance of the summer brownout in the cooler months of May or June.

Because of their lack of residual killing power, treatment with benzimidazoles must be delayed until late June or early July when transmission of GI parasites has stopped from the summer brownout.

There is some controversy among veterinarians and animal scientists on whether  deworming the cow is necessary for increased calf growth rates. In most areas of Texas, deworming of the cow is warranted solely for her benefit. In addition, it has been definitely established that milk production increases when parasitized cows are dewormed.  Thus, we recommend deworming both cow and calf. 

Bottom line

          The bottom line is the prediction of the economic outcome (benefit:cost) of the management practice.  The estimate should be calculated in a conservative manner.

The average benefit is the income from 25 extra pounds of production. The cost is the sum of the cost of the anthelmintic plus the expense of working the herd. The expense of working the herd would vary from one ranch to another.  

For our example, we will use a working cost of $2.00 per cow/calf pair. Presently, a 500-pound calf would sell for $0.95 to $1.02 per pound. At $0.95 per pound, 25 extra pounds would be $23.75 benefit.  

The cost of deworming a 1,100- to 1,200-pound cow and her 200- to 350-pound calf with Dectomaxâ, for instance, would be $4.10 for the Dectomaxâ plus $2.00 to work the pair for a total cost of treatment of $6.10.  

That would be $23.75 benefit for a $6.10 investment; a benefit:cost ratio of 3.9 or 390% return on investment in six months.  

Looking at it another way, treatment would result in an additional profit of $17.65 per calf at weaning.

          Deworming of nursing beef calves is a management practice that results in increased growth rates comparable to growth-promotant implants.  These two practices go well together and result in partially additive increases in growth rates of calves. 

          The benefit:cost of deworming of nursing beef calves is highly profitable. This is new information that offers a tremendous opportunity to enhance profits. 

Presently less than 10 percent of Texas beef cow/calf operations use the practice. Texas ranchers market more than four million beef calves a year. The implementation of this management practice has the potential to increase the annual income of Texas ranchers by many millions of dollars.

          The decision on whether or not to deworm your nursing calves is easy. Don’t worry about whether they are infected with gastrointestinal parasites: They are!  

Don’t worry about whether they are infected with a high enough number of gastrointestinal parasites to decrease their growth rates: They are! 

The best approach to this opportunity to increase profits is the Nike approach: Just Do It!