D220
Fecal Flotation and Parasite Control Programs

Introduction: The frequency and type of product used for de-worming will vary depending on region of the country, areas grazed, and types of parasites encountered. Because it is difficult to recommend one parasite control program to fit all operations, the frequency of de-worming should be based on producer experience and veterinary advice. In some situations, fecal egg counts can be a useful tool in identifying abrupt changes in parasite numbers and identifying when a significant parasite burden is present. However, it is important to realize that fecal egg counts should NOT be the only determining factor on when to de-worm. For example, some of the most important and damaging worms, such as the brown stomach worm (Ostertagia), are poor producers of eggs. It is also important to note that the number of eggs in the manure does not indicate how much damage has been done by parasites, and that it is difficult to distinguish between eggs of different species of worms. The following information will discuss the basics of fecal egg counts, the methods used to perform fecal flotations, and then describe how to interpret fecal egg counts.

The Importance of Proper Internal Parasite Control: Assessing when cattle need to be de-wormed can be difficult. Because of this, mistakes can be made and the use of anthelmintics (de-wormers) can be overdone. Excessive de-worming is wasteful, and it increases the chance for parasites to develop resistance to the de-worming products. The effectiveness of de-worming can be preserved by keeping de-worming to a minimum, compatible with profitable production standards.

1. To develop and survive, nematodes (roundworms) must have moisture.
2. As the concentration of cattle increases, the concentration of parasite eggs/larvae for ingestion also increases. Therefore, cattle that are in large grazing environments are not likely to suffer from significant parasite problems.
3. Some types of nematodes, such as Ostertagia, can stop their development until conditions become favorable, and then develop into an infective stage.
4. Many of the eggs and some larval stages will survive the cold and freezing of winter. Very few will survive the heat and drying that occur during the summer. The only exception to this can be when they are found in a very moist environment (meadows, irrigated pastures, around springs, etc.).
5. Fecal egg counts can sometimes be an indication of the parasite load found in an animal; however, there may be many arrested or immature larvae present that are not shedding eggs. These can mature and cause a significant problem, but may not be detected on a fecal flotation. There can also be low numbers of very damaging parasites that may not appear to be that significant on the fecal egg count. To overcome this problem, it is necessary to check fecals from several different animals 3-4 times during the year. Fecals should be repeated until an obvious pattern is noted in the life cycles of the parasites common to the area. This pattern can be used to then determine the proper de-worming schedule for the specific operation.
6. Egg shedding is related to the type of feed being ingested. When the feed is green, wet, and lush, the egg count will increase. When the feed is dry and fibrous or has high levels of concentrates, egg shedding will decrease.
7. Fecal egg counts can be used as a good indication of the parasite load found on a given pasture. The counts can be used to help determine when pasture rotation is necessary.
8. Cattle can develop some immunity to nematodes.

What are Fecal Worm Egg Counts?: A fecal worm egg count is simply a count of the number of worm eggs present in each gram of feces from a cow. There are many different tests that can be used, with one of the most common being a McMaster’s fecal eggs per gram (EPG) test. Most of the tests are really quite simple. However, there are many steps where mistakes can be made if the procedure is not thoroughly understood. Regular practice is required to accurately count all of the eggs. For these reasons, fecal worm egg counts are considered a laboratory procedure.

Collection of Fecal Samples: A reasonable and realistic sample of the herd needs to be examined before any confidence can be placed in a fecal egg count as a predictor of a parasite load. Fecal samples should be collected from a minimum of 6 individual animals selected randomly from the herd. A misleading result can take place if fewer animals are sampled. The following numbers are often used as a recommendation for the number of animals to sample: Six animals from a group of 50, or 6–10 for a group of 100.

Using a gloved hand, collect fecal samples directly from the rectum of selected animals. By far, this provides the most accurate samples, but requires the corralling of the animals and is distasteful to many people. Another procedure involves moving the animals to a convenient place in a pasture (a corner works) and holding them there for a few minutes. During this time, many will defecate, allowing for the collection of fresh fecal samples. Care must be taken to avoid contaminating samples collected in this fashion with soil and plant material. To avoid contamination, gather samples from only the top surface of the manure pile in areas that have not contacted the ground.

No individual sample should be less than 4-5 grams. This is equivalent to a heaped teaspoonful of fecal material. Place the fecal samples into individually labeled containers. Small plastic bags are ideal. The samples should be kept cool, so immediately place them into an insulated container with a frozen ice pack. Do not freeze samples or refrigerate them for long periods (more than a day). They should be delivered to a veterinarian as soon as possible after collection.

When to use a Fecal Egg Count: When collecting samples, concentrate on stocker and replacement animals that are 6-18 months old, young animals, weaners, and lactating animals. These animals experience the most worm problems. Cattle can develop an immunity to some parasites, and adult cows will seldom shed more than 10 eggs per gram (epg). Because of reduced immune status, there is often a rise in egg shedding at the time of calving. Individual cows may also shed high numbers of eggs if their immunity is compromised for some other reason. Because it takes time for them to get infected and begin shedding, new calves seldom shed many eggs until at least mid or late summer. Fecal samples should be collected from cows right before or right after calving. Calves should have fecal samples checked when they are about 6 months old. However, realize that depending on the time of year, the calf may be in a stage where egg shedding is at a very low level.

When to use Parasite Control: Because fecal counts only estimate the parasite load, there is no clear cut level at which de-worming is indicated. As a general guide, a level of about 500 eggs per gram of feces would indicate that de-worming is needed for cattle. However, a more effective way of deciding when to de-worm would be to monitor fecal samples every 4-8 weeks and de-worm when there is a dramatic rise in egg counts. This would also be a good indicator of when pasture contamination is significant and moving animals to another pasture is necessary.

If it is determined that de-worming is necessary, a second fecal egg count should be done 10-14 days after the de-worming. If there is less than a 90% drop in the eggs per gram between the first and the second fecal tests, there is parasite resistance to the de-wormer, and a different product should be chosen.

Treatment/Prevention: The following recommendations are the general basis of parasite control. They are not intended to be rigid guidelines and should be varied, even between pastures on individual farms or ranches where experience indicates that more or less control is needed. Also, the timing of de-worming may be altered to suit individual producer needs. All these decisions should be made with the help of a local veterinarian.

• To stop intestinal worms from accumulating, do not use the same pastures/pens for calving each year.
• If clean grazing such as stubble is available, cattle should be given an effective broad spectrum de-wormer before they are moved on to it.
• If possible, all animals that are de-wormed should be held in a dry lot for at least 3 days. This is because most de-wormers do not kill the parasite eggs, just the adult worms. Waiting 3 days will help the animal eliminate most of the parasite eggs in the dry lot and not on pasture/pens where other animals may ingest the eggs.
• If pastures are used for grazing, rotate them every 3-6 months.
• Prevent the post-calving rise in parasite egg production.
• Have a veterinarian perform a fecal egg count to check the effectiveness of any de-worming or parasite control programs. This should be done 10-14 days after de-worming.
• Avoid resistance problems by not using the same products year after year.
• Select for animals that are parasite-resistant. These are animals that have a natural resistance to internal parasites. They can often be identified through the use of fecal egg counts.

De-worming Program for Internal Parasites: In general, there are four common times when animals are de-wormed. In areas where parasite burdens are low, a once a year dose may be all that is required:

1. In colder climates where the animals are moved off of pasture for the winter, a dose can be given just before the move is made.
2. A second time for de-worming occurs 1 month prior to calving. De-worming cows about 2-4 weeks before calving and then moving them to a safe pasture/pen will prevent the rise in production of worm eggs after calving. If the cows are not moved after this dose, additional doses may be required.
3. A de-wormer for calves at weaning should also be given. After the de-worming, the calves should be moved to a "safe" pasture/pen.
4. Breeding bulls are often de-wormed 1 month before the breeding season.

* Page A620 of the dairy manual also has information about parasite control.

Below are common products used to perform a fecal flotation. Before collecting a manure sample for a fecal flotation, contact your local veterinarian or laboratory to determine how they would like the sample collected and then transported. Some clinics will provide a collection and transport device for the sample.

References: Economics of Deworming Beef Cattle and Herd Monitoring with Fecal Egg Counts, Clell V. Bagley, DVM, Extension Veterinarian Utah State University, Logan UT