Parasites are one of the largest management headaches in the small ruminant industry, and arguably one of the most complicated issues faced by producers. The complex nature of parasite management is daunting, yet understanding best management practices is essential to your success in raising small ruminants. This is particularly important if they are being pasture-raised and managed. The American Consortium for Small Ruminant Parasite Control (https://www.wormx.info/) is an exceptional resource to consult periodically for best practice information. While I am not a veterinarian, I am a small ruminant producer. Quite often when I am at farms doing nutrition consultation, I also end up assisting customers with parasite issues. It is a major problem in our industry. Because 2019 was an exceptionally wet year in our region, parasites hit numerous flocks/herds hard. At the same time, too much moisture lowered grass quality, and hay quality was decreased when the excessive number of rainy days meant hay producers lacked enough dry days to cut, dry and bale hay. The challenges faced as a result of these issues led to important discussions with producers. For many years, the recommendation was to deworm several times a year as a routine part of management, and to rotate dewormers periodically. The more we learn about parasites, the more we realize how much of a headache we have caused ourselves in the emergence of dewormer resistance. There are a few key components to a parasite management plan, yet producers should consult the many fact sheets and studies available to be better equipped to tackle this tricky challenge.
Nutrition is an important factor in the health and productivity of your flock/herd. Research suggests that high protein diets can help combat parasitism or susceptibility to parasitism. However, protein is generally overfed in most systems now, making it important to understand your nutrition program completely before deciding to simply add more protein. Numerous vitamins and minerals are important in immune function, including copper, zinc, selenium, manganese, iron, iodine, and Vitamin A. It’s essential to your operation to closely monitor the nutrition of your animals year-round. Animals that are stressed due to factors including the weather, lambing/kidding, freshly weaned, moved, poor body condition, etc. are going to be more susceptible to health concerns. Genetic selection Producers should remember that there are animals within the flock that will be more “resistant” to parasites than others. There are also going to be animals that appear to be more “resilient” as they may carry a high parasite burden but don’t show the effects. For a true understanding of which animals in your flock are resistant versus resilient, FEC’s (fecal egg counts) are an important tool. Genetic resistance to parasites is moderately heritable so it can be an important tool to select for animals that carry a lower parasite burden and require less deworming. An important rule of thumb is that 70-80% of worms shed on your property often come from 20-30% of the herd. Producers who work towards having fewer “problem” animals may have less of a parasite concern later.
Rotational grazing is an important part of managing parasites in small ruminants. Allowing animals to constantly graze the same area impacts nutrition, and the practice allows them to continually infect themselves with infective larvae. Multi-species grazing can also be a helpful tool, as cattle and horses can “clean up” small ruminant parasites. There are several other factors to consider regarding pasture management, however, they are not as easily applied in the Upper Plains and under most Midwestern conditions including using forages like sericea lespedeza. Dry lotting animals can be another important tool in the toolbox, especially if rest time for pastures is necessary. Do not graze pastures to the ground, as generally no lower than 3-4 inches of grass height remaining in the pasture is important. Under an ideal temperature of around 85 degrees and high moisture levels, parasite eggs will hatch, experience 2 molts and can develop into the infective stage within 3-4 days. If the temperature is higher than 85 degrees, there could be a greater hatch rate with a lower hatch percentage. In an ideal world, animals would be able to graze a pasture until the infective larvae appear, and then would be moved. However, these decisions are determined by temperature and moisture, which explains why the summer of 2019 was such a perfect storm for parasites.