Rotational grazing system impacts parasite control for cattle

STOCKTON, Ill. — Cattlemen develop rotational grazing systems for many reasons, including parasite control.

“We have not dewormed the adult cows for five years now,” said Bob Melcher, a retired veterinarian.

“We monitor the cows and there is no reason why we would justify the expense of deworming the cows because the parasite load is so low,” said Melcher during a presentation at a Nutrient Stewardship Field Day held at Greg Thoren’s farm and hosted by Illinois Farm Bureau.

“That is due to the resistance that we have developed and also through exposure,” he said. “We do deworm the calves.”

Recently, Melcher completed the yearly scan of pastures to evaluate the parasite load on Thoren’s farm.

“The parasite load in younger calves is higher than it has been in other years and Greg told me that he has not been quite as diligent about moving his cows as often as he should be,” the veterinarian said.

“We need to keep the rotation and move them before the parasite eggs hatch into larvae and infect the calves,” he said. “Going back to the five to a maximum of seven days rotation, I think we will see the parasite load come down and be less of a problem.”

Flies can affect the grazing patterns of cattle.

“Fly control is hard to do in a rotational grazing system because you do not have the animals confined where you can easily put fly control on them,” Melcher said. “So, we are using fly predators and pour ons.”

If there is a fly problem, he said, it is important to know which type of fly is on the cattle to determine the best treatment method.

“Horn flies live on the animal their whole life and they take 20 to 30 blood meals per day,” he said. “Face flies bother the animals’ eyes because they survive off the nutrition of the tears and stable flies bite the lower legs.”

The problem with face and stable flies is they live off the animal most of the time, Melcher said, and they just go to the cattle to feed.

“By reducing the environment where they prosper, that will help your situation,” he said.

Lice fall into two categories: biting lice and sucking lice.

“Biting lice eat the dead surface of the skin and sucking lice will suck a blood meal,” Melcher said. “I have seen populations get bad enough that it will affect the body condition of the animals.”

Therefore, it is important to apply the product correctly to the cattle and read the label before application.

“In the fall and winter lice will completely cover the animal, but in the summertime the lice are smart enough to get out of the sunlight especially on black-hided cattle and survive on the underside of the animal,” Melcher said. “If you do a poor job of covering the animal, you have wasted the product and you will have a break sooner or later.”

Cattlemen also should monitor their cattle for Asian longhorned ticks.

“These ticks are invading the state and there are six counties where it has been identified,” Melcher said. “They can cause damage by just sucking blood and they also carry theileria which causes breeding and production problems.”

These ticks are quite small.

“A female that is fully engorged and ready to lay eggs is only about the size of a pea,” Melcher said. “The nymph is about the size of a sesame seed.”

A female Asian longhorned tick can lay fertile eggs without ever mating with a male.

“A female can lay as many as 2,000 to 3,000 eggs, so one female can create a population explosion,” Melcher said.

The ticks are often found in the ears of cattle.

“Use a flashlight to look at the ears,” Melcher said. “In areas where they have this, veterinarians are changing needles between every animal, otherwise the theileria is going to spread like crazy.”

Controlling the spread of theileria is very important.

“The cattle are our harvesting equipment, so if they are not healthy, they will not use the crops in the pasture,” the veterinarian said.

Thoren uses the eShepherd virtual fencing system to graze pastures and cover crops on his farm. This is the first year he planted a field of sorghum-sudangrass.

“There are 25 head of fall calves that will be 2 years old in October,” he said.

This forage grows quite fast and produces a significant tonnage.

“The calves did not take it down where I thought it should be, so I ran their mothers behind them to clean it up,” the cattleman said. “The finishing cattle got the best feed and the cows got the rest, plus I put a back fence in and some of the regrowth is now over my knee.”

“Those calves have never had a pound of grain and they have been outside their whole life — they have never seen a shed,” Thoren said. “They are the healthiest cattle I have.”

“Put your cattle outside, and as long as they have a windbreak, shade and water, they will do fine,” he said.