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Pets Large & Small

Local vet poisons neighbor's cows

Dr. Kimberly Brokaw, DVM

(9/2015) There are many different types of herbicides available for killing weeds in a pasture or a hay field. Most of us who grow hay, regularly use herbicide to kill weeds. This is particularly true when a pasture or hay field is not yet well established. Each of the herbicides comes with a package insert listing the dangers to people and grazing animals, how it should be applied, when it is safe to allow animals to graze or make hay, what it can be mixed with, etc.

One of the things that always concerns me is how some of the herbicide's instructions say the person applying the spray needs to wear protective gear and not touch the spray, and then in the next sentence it says it is safe for animals to graze immediately after the spray is applied. People and animals are usually not that different in their tolerance for many (but not all) poisons. I have treated several horses that have coliced after eating grass from recently sprayed pastures. I've treated both dogs and horses for "shake and bake" following pesticide exposure. The animal starts having seizures (shaking) which raises their internal body temperature to dangerous levels. Most have survived with veterinary treatment.

For these reasons I am hesitant to treat my pastures with herbicides. The only exception is poison ivy. I react horribly to poison ivy so I spray to keep it from overwhelming my pastures. When I do have to spray the horse fields to eradicate poison ivy, I am careful to pull the horses off the field (even though the label says it is safe for them to graze after spraying).

When spraying the hayfield, I am less cautious. Previously we had hired a commercial company to spray herbicide and fertilizer on the field. After a couple years in a row where they sprayed in the rain, rutting up the field, and not killing all the weeds, I decided that I could figure out how to treat the fields myself. Then I could control when they were sprayed and with which chemical.

Before I even got to herbicide selection, I realized spraying was more involved than I thought. Fortunately for me I always enjoyed high school math and word problems were one of my favorite parts of math class. If you have my sprayer with a 30-foot boom, and set the spray nozzles at 20 inches above the ground, when the pressure in the tank is at 30 psi and you are traveling at 5mph, it puts out 15.4 gallons of liquid per acre. How much herbicide do you add to the 150-gallon tank to kill the weeds, not kill the grass, and have it safe to make hay for horses?

Luckily I already had a very good knowledge base on both weed identification and herbicide toxicity to horses. Different herbicides as well as different concentrations of certain herbicides would kill different types of weeds so weed identification is important. I could spray one herbicide in the fall and not have to worry about the long withdrawal time as we weren't going to be making hay until spring anyway and no animals are grazing on the hay field.

After much thought, I selected the herbicides I wanted, taking into account which ones worked best with non-ionic surfactant vs fertilizer. Rather than simply picking one, I picked three and opted to combine them all together for a greater spectrum of weed killing activity. Plus with it being the fall, I could use herbicides that would not be safe to use in the spring due to the long withdrawal time. I obtained the herbicides and proceeded to calculate how much to add to the tank. If I'd just been adding one product it would have been a simple matter of pouring in the amount listed on the back of the bottle. However, as I was combining three (yes I did a compatibility test to make sure they wouldn't all congeal in the tank), I would have to convert to lbs per acre of active ingredient into how much do you dump in the tank. In the end I came up with 2.25 cups of one product, 1.3 gallons of another, and 2 pints of the third. I dumped it all in, started the tractor, and sprayed the fields. After a little glitch where a neighbor had to assist me with getting the sprayer working again, the fields were sprayed. I instructed people who I knew rode their horses around the fields to not let them graze when riding for the next 37 days.

Over the next few days I watched as the weeds started to die and I felt successful. I'd managed to kill weeds, not rut up the fields, and not kill or sicken any horses. It was in the midst of my feeling of accomplishment that I was riding my horse around the field and noticed that almost all of my neighbor's cows were trying to break out of his pasture and get into the recently sprayed hay field. On the plus side, none of the cows were in the field, yet. These neighbor cows have a history of escapes, but my neighbor assured me, before I sprayed, that he was fixing the fence so there would be no more escapes.

As I felt a wave of anxiety come over me, I reminded myself that none of the cows were dead yet. I figured I had a few options. I could hope the fence held, not say a word to the farmer, and hope that if they escaped into my field, they all survived. The second option, was to tell him about how I had concocted my own super strength field spray by combining an assortment of chemicals together. Not only was this concoction toxic to his cows but it also meant that if his cows came into my field, he now couldn't send them to slaughter for the next few weeks as the meat was contaminated. Hopefully, the second option would make him do something, immediately, to keep the cows out of my field.

I talked with my neighbor, again, and he said he thought the repairs he made after the last great cow escape would hold. Luckily my neighbor wasn't planning on slaughtering any of the cows for the next 5 months. So the only question was were they going manage to break into the field and would they get sick?

I was picturing reading newspaper headlines "Local vet poisons neighbors cows." Definitely not the kind of publicity I wanted and I was sure the clinic I work for felt the same way. I continued my ride around the hay field. I could see where he had cleared part of the underbrush and added new stakes to hold up the wire. Hopefully it will hold and I won't see a herd of dead cows in my backfield on my next trail ride.

Read other articles by Dr. Kim Brokaw