David P. Price is a consulting nutritionist specializing in feedlot and range cattle
Spring worming is a ritual with many ranchers. But with the cost of pharmaceuticals and the downturn in the markets, it is wise to approach worming from a managed prospective. That is, instead of a routine chore, we need to analyze whether it is truly necessary and if so, administer wormers in a “strategic” manner.
Strategic meaning it is possible to clean up pastures so as to reduce or eliminate the need for future worming. The caveat to this is you must be rotationally grazing. It is not possible to eliminate parasites from pastures that are continuously grazed. Likewise, if a large concentration of wildlife is present, pastures may be recontaminated. That said, with purposeful management it is possible to greatly reduce the need for worming.
First off, cows should be tested for parasites before any worming is done. This entails taking manure samples from at least 10 individuals and sending them to a parasitology laboratory. In lieu of that, most any veterinarian with parasitology training can function to determine if significant parasites are present. The advantage to a lab specializing in parasitology is they can usually provide a more accurate description as to what type of parasites are present. This type of lab work is a simple matter of diluting the samples and looking at them under a microscope. Worm eggs become clearly visible. The real skill is identifying from what species of worm the eggs came from. When this is the only enterprise the laboratory engages in, obviously there is more experience in identifying species. This can be of significant importance with respect to which wormer to buy (as not all products are effective against all species).
But the most fundamental purpose is to tell whether worms are present or not. If they aren’t, then worming the cows is obviously a waste of time and money.
If they aren’t wormy, that does not mean they won’t become infected later on, but it does mean worming now will do no good. (They’ll still become infected later on.)
It is important to realize that for worms to infect cattle they need warm temperatures and moisture. If it is cold, or if it is dry, cattle won’t become infected. (And if they aren’t infected, it will do no good to treat them.)
But when the spring thaw comes and it warms up, worm eggs hatch. If moisture is present on grass, the freshly hatched worm larvae will swim up the moisture on the leaves of grass, and wait for an unsuspecting grazing animal. When the grass is consumed, the larva is swallowed and the animal is infected.
If, on the other hand, no cattle are present, the larvae will die. This is how we clean up pastures. Defer pastures during the spring warmup. The problem is this is not something that can be cut in stone with respect to timing. If moisture is not present during the deferral, the parasites will not hatch. Likewise, if warm temperature are late in arriving, the clean up will likewise be late. Once you have a clean pasture, obviously we don’t want to put infected cattle on it. As soon as they lift their tails, it will be recontaminated.
When first starting out, it is often necessary to worm twice. After the first worming, wait roughly six weeks after conditions are right for reinfection. Then worm a second time to eliminate the reinfection, and then wait another two weeks or so before moving the cattle.
Obviously, once the herd and pastures are parasite free, any new cattle brought in must be wormed and kept isolated before being turned out. Otherwise, just a few head can reinfect the pasture.
My parasitologist friends tell me since the emergence of the large number of generic anthelmentic drugs, they are seeing a significant amount of parasite resistance. Likewise, as we mentioned previously, not all products are effective against all species. This emphasizes further the need for testing. If you’ve bought brand X, but it’s not effective against the species you have, or a resistance has been developed to that drug, your pastures will not clean up.
Taking manure samples is one of the jobs that often doesn’t get done. When it doesn’t and cattle are wormed unnecessarily or with the wrong product, you may as well have thrown the money spent out in the street. Without the lab work, we cannot make considered decisions.