Ask The Mechanic

Solutions, Not Obstacles

Image by Becky Mills

Q: We have five good heifers we would like to keep for replacements, but we don’t have a place to keep them away from the bull. Isn’t there a shot our veterinarian can give to postpone them coming into heat?

A: Many years ago, I was at a dairy doing a monthly reproductive herd check when the owner asked me if I had read a certain book. I told him I was so busy I didn’t have time to read. He told me he didn’t either; he listened to books on tape. I told him audio books were expensive; he told me he checked them out at the library. I told him I did not have a cassette player in my truck; he told me he didn’t either. I noticed he had headphones around his neck and a Walkman on his hip. The book he asked about is long forgotten, but the lesson I learned that day has lasted more than 30 years. We often create obstacles that really are not there.

Your obstacle isn’t your heifers and when they come into heat as much as what you are doing with your bull in what should be his off-season. Find a way to remove him from your herd. Not only does this prevent those replacements from getting bred, it allows for a controlled calving season.

Specific to your question, I know of no approved, available, safe, long-term way to suppress estrus in heifers. Prostaglandins, including Lutalyse and Estrumate, can terminate pregnancy in the first three to four months. But, this might need to be done several times. Keep in mind, later-term-induced abortions can often lead to retained placentas, and this could decrease subsequent fertility.

Q: What size needle do you recommend for giving cows shots?

A: To some degree, this depends on where you are giving the injection and what it is. Start with placement. Injections should always be given in the neck. If so labeled, they should be given under the skin, or subcutaneously (SQ).

Concerning needle size, I recommend the smallest gauge needle possible. Large needles make bigger holes, are more painful and cause more damage, and product can leak back out. I use 20-gauge, ¾-inch needles for SQ vaccinations on calves. With adult cattle, or when administering thick medications, I use a 16-gauge with a ¾-inch needle. I only use needles once. This means they are sharper when you use them, and it eliminates any risk of spreading disease in the herd. For intramuscular injections, I recommend an 18-gauge, 1- to 1½-inch needle. If the product is very thick, I may use a 16-gauge needle, but I find very little need for this size now with products currently on the market.

Another key to good injection technique is proper restraint. Never inject more than 10 milliliters at one site, and never inject through a dirty hide. If you don’t use a clean needle every time, change them out at least every 10 head. A clean needle is critical every time you pull up vaccine or medication. Never use bent or burred needles. At the end of the day, my motto is “needles are cheap; cows are not.”

If you have not done this already, I highly recommend becoming Beef Quality Assurance (BQA) certified. Needle size and proper vaccination protocol is a big part of the training. BQA saves the cattle industry millions, if not billions, of dollars through reduced damage to valuable cuts of meat. It also helps reduce the incidence of disease. Most states have BQA meetings where you can become certified, and there is an online program, as well (

Q: Last fall, we banded a bull and later found we missed one testicle. We rebanded him, and he became lame on one leg. He fell over and just laid there. We cut the band after about 5 minutes, but he died an hour later. What do you think happened?

A: I can only guess at what might have happened. The calf could have sustained damage to the nerves or spinal cord while in the chute. This would explain the lameness and, if the damage were severe enough, it could lead to death.

I have had to deal with several of these cases, and it is tough to remove the remaining testicle surgically when you miss one at banding. There is often a lot of scar tissue, and it is very traumatic to the animal.

It is possible the main artery to the testicle ruptured, and the calf bled out into the abdomen. An embolus or blood clot that moved to the lungs or brain is another possibility that would have caused death.

We will never know for certain what happened. This highlights how important it is to make sure you have both testicles and nothing else below that when you band calves.

Please contact your veterinarian for questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice, but is purely for informational purposes.

Write Dr. Ken McMillan at Ask The Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email


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