Vet’s Voice: Deworming and pasture management | TSLN.com

Vet’s Voice: Deworming and pasture management

Dave Barz, DVM

For the April 23, 2011 edition of Tri-State Livestock News.

I thought spring was here, but Mother Nature sure fooled me. She made it snow. The wet muddy conditions will be hard on those calving and we can only hope for better weather. Twenty years ago the jury was divided as to whether it was economical or necessary to deworm cows. Now most producers are using some type of deworming.

The original deworming debate centered around the question, “Does the deworming of the adult cow increase her productivity enough to justify the cost of deworming?” Now with feed costs at all time highs, the feed conserved by deworming more than pays for the price of the product.

Now researchers argue, “We must deworm cows before pasture turnout to avoid pasture contamination with parasite eggs and larvae.” The less parasites carried by the cow to grass, the fewer eggs will be shed on the pasture. With the lower population of worm larvae, the fewer larvae calves will consume. These lower worm loads will convert to more calf pounds at weaning. This involves both deworming and pasture management.

There are many pasture management techniques which help lower parasite populations. In cold climates like ours, internal parasites go into a form of hibernation both inside the host animal and in the soil. As the weather warms, these hibernating parasites emerge and begin their normal lifecycle. As the eggs are shed on the ground, the emerging larvae climb up wet-damp grass. These larvae are very small and usually don’t climb up the grass plant more than 4-6 inches. During early summer it is best to make sure pastures are not overgrazed. If grasses are 12-16 inches tall, very few larvae will be ingested. These larvae also rarely travel more than 12 inches from the manure port. This also requires careful analysis of cow-calf densities in pastures.

In the past we used strategic deworming strategies, trying to eliminate parasites during the grazing season. This required rounding up cows and calves during the grazing season to administer dewormers. Most producers could not justify the time needed, but some dewormers devised administration through mineral or blocks.

Pour-on dewormers need to be used on a rotational basis. There are several of these macrocyclic lactones on the market. We have used these products in the fall and winter for controlling lice populations. We are beginning to see some resistance for this use and also some internal parasite resistance. We feel injectable sister products are a better alternative. These do well against the brown stomach worm (Ostertagia), a common problem in our area. White wormers are also effective against the brown stomach worm as well as Cooperia. For mixed infections, these are the wormers of choice. Monitor the results of deworming by pulling a fecal sample from the calf before and after deworming. Egg counts in cows aren’t as diagnostic, as cows develop immunity to the parasites over time which decreases egg shedding.

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It is recommended to deworm cows in the fall and again in the spring to decrease pasture contamination. The calves raised in this part of the country have the potential to gain 3 pounds per day when on pasture. A moderately infested calf may only gain 2.2 pounds per day, showing no clinical signs of parasite populations. The difference of 0.8 pounds per day for 150 days on pasture is more than 100 pounds of potential loss. With today’s market, those numbers are significant.

Careful pasture management and a well-planned deworming program can add pounds to calves at weaning. Consult your veterinarian, extension specialist or nutritionist for a program which works for you. The extra sale dollars will not only pay for deworming, but also put profit in your pocket.

I thought spring was here, but Mother Nature sure fooled me. She made it snow. The wet muddy conditions will be hard on those calving and we can only hope for better weather. Twenty years ago the jury was divided as to whether it was economical or necessary to deworm cows. Now most producers are using some type of deworming.

The original deworming debate centered around the question, “Does the deworming of the adult cow increase her productivity enough to justify the cost of deworming?” Now with feed costs at all time highs, the feed conserved by deworming more than pays for the price of the product.

Now researchers argue, “We must deworm cows before pasture turnout to avoid pasture contamination with parasite eggs and larvae.” The less parasites carried by the cow to grass, the fewer eggs will be shed on the pasture. With the lower population of worm larvae, the fewer larvae calves will consume. These lower worm loads will convert to more calf pounds at weaning. This involves both deworming and pasture management.

There are many pasture management techniques which help lower parasite populations. In cold climates like ours, internal parasites go into a form of hibernation both inside the host animal and in the soil. As the weather warms, these hibernating parasites emerge and begin their normal lifecycle. As the eggs are shed on the ground, the emerging larvae climb up wet-damp grass. These larvae are very small and usually don’t climb up the grass plant more than 4-6 inches. During early summer it is best to make sure pastures are not overgrazed. If grasses are 12-16 inches tall, very few larvae will be ingested. These larvae also rarely travel more than 12 inches from the manure port. This also requires careful analysis of cow-calf densities in pastures.

In the past we used strategic deworming strategies, trying to eliminate parasites during the grazing season. This required rounding up cows and calves during the grazing season to administer dewormers. Most producers could not justify the time needed, but some dewormers devised administration through mineral or blocks.

Pour-on dewormers need to be used on a rotational basis. There are several of these macrocyclic lactones on the market. We have used these products in the fall and winter for controlling lice populations. We are beginning to see some resistance for this use and also some internal parasite resistance. We feel injectable sister products are a better alternative. These do well against the brown stomach worm (Ostertagia), a common problem in our area. White wormers are also effective against the brown stomach worm as well as Cooperia. For mixed infections, these are the wormers of choice. Monitor the results of deworming by pulling a fecal sample from the calf before and after deworming. Egg counts in cows aren’t as diagnostic, as cows develop immunity to the parasites over time which decreases egg shedding.

It is recommended to deworm cows in the fall and again in the spring to decrease pasture contamination. The calves raised in this part of the country have the potential to gain 3 pounds per day when on pasture. A moderately infested calf may only gain 2.2 pounds per day, showing no clinical signs of parasite populations. The difference of 0.8 pounds per day for 150 days on pasture is more than 100 pounds of potential loss. With today’s market, those numbers are significant.

Careful pasture management and a well-planned deworming program can add pounds to calves at weaning. Consult your veterinarian, extension specialist or nutritionist for a program which works for you. The extra sale dollars will not only pay for deworming, but also put profit in your pocket.

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