Veterinary Viewpoints: Old McDonald Had a Farm

Tuesday 17th August 2021

Media contact: Derinda Blakeney, APR | University of Veterinary Medicine | 405-744-6740 |

Old McDonald did actually have a farm, and what made his farm so fun for us as kids, and maybe now that we sing it with the kids in our lives, were all of the different animals he had. Multi-species farms are common in Oklahoma, and they bring joy, as the song suggests. However, there are some considerations when multiple animal species are housed in close proximity to one another. Certain drugs, feed and feed additives that are beneficial to the health of one species can even be harmful to other species.

Here are the five biggest dangers on a multi-species farm:

  1. copper is an important trace element. It is required by all animals for a large number of important biological processes. The amount of copper that livestock species require varies widely. Sheep are by far the most sensitive livestock species to copper. Although sheep require a small amount of copper in their diet, it is potentially dangerous to give them almost any feed that is not labeled for sheep. Goats are slightly more tolerant of copper than sheep and require a little more in their diet, but we are also seeing copper toxicity in goats. Typically, feeds for pigs and poultry are the most dangerous, followed by horse feed and cattle feed. Only feed food that has a picture of your animal on it and do not allow other species to access this food.

Remember that everything that is eaten shows up in the feces. The manure of these more copper-tolerant species is also rich in copper. I once consulted on a case in which several sheep died on a farm that was adjacent to a pig farm. The sheep stood in a pasture below the pigsty and there was drainage to the sheep pasture. The grass along the fence between the two was lush from all the manure and the sheep would graze along that fence line and die of copper poisoning.

Feeds are not the only sources of copper on a farm. Loose and blocked trace elements, injectable trace elements, copper boluses, algicides (copper sulfate), and other agricultural chemicals can also contain copper and be toxic.

  1. Ionophores are a class of feed additives that promote growth and help control coccidia in ruminants such as cattle, sheep and goats. Ionophores include drugs such as Monensin (Rumensin) and Lasalocid (Bovatec). However, their usefulness ends with the ruminants as they are deadly to horses. There are many stories of horses being accidentally fed or breaking in and consuming ionophore-containing cattle feed. The ionophores cause acute heart failure. Even traces of these drugs can be fatal, with some reports of horse deaths from feed mills that mixed horse feed after cattle feed in the same mixer without properly cleaning it.
  2. Grain, especially corn, are used in the feeding of all types of livestock. So how can they be problematic in multi-species operation? Let’s talk about the digestibility of grain using corn as an example. Maize comes to us in various forms: whole maize, steam flaked, rolled, cracked, ground, etc. The less maize is processed, the less digestible it is. You know this because on a whole grain diet you often see whole kernels of corn in animal manure. However, as the corn is processed, more starch is exposed, making it more digestible, but also potentially more dangerous. With increasing processing and starch exposure, the risk of cereal overload or rumen acidosis increases. Whole grain maize therefore causes far less grain overload and rumen over-acidification than much finer ground maize, for example for poultry or pig feed. If an ox breaks into a container of whole corn it can experience severe abdominal pain that needs treatment, but if it breaks into chicken or pork feed corn it could puff up and die quickly from the extra processing.

I recently saw one of the worst cases of rumen acidosis in a beloved goat I have ever seen for breaking into the feeder room and eating a large amount of waterfowl food. She came to us unconscious on Christmas morning and took a week of hospitalization to recover. The fine corn grinding used in poultry and wild bird feed is extremely dangerous for cattle, sheep and goats.

  1. alfalfa is an important protein-rich feed on many farms that is fed to a large number of species. While it is safe for most of our common domestic animals, animals that alfalfa should never be exposed are male sheep and goats, especially if they are domestic pets or miniature breeds such as Nigerian dwarf or pygmies. Male sheep and goats are at high risk of bladder stones, which become lodged in the urethra and can lead to urethral ruptures or bladder and kidney failure. Bladder stones can also be formed in these men from a high-grain diet, but the stones made from an alfalfa-based diet are by far the most difficult to treat. When feeding horses or cattle with grain and alfalfa, it is best to keep male sheep and goats away from these feeding places.
  2. Avermectin Deworming class includes the products that contain ivermectin (Ivomec and generics), doramectin (Dectomax), moxidectin (Cydectin), and eprinomectin (Eprinex, LongRange). Many brands of horse deworming paste contain an avermectin de-wormer – be sure to read the labels. Farm dogs are the problem here. As you know, when you give a de-wormer, especially an oral paste, to a horse, some of them will be dropped on the ground. In addition, the active ingredient is excreted in the faeces and is present in the dung on the pasture. Some breeds of dogs, especially white-footed herding dogs, are very sensitive to ivermectin and should never be exposed to these drugs as they can damage the nervous system and be fatal. Most fatal farm dog exposures come from paste worming agents that fall to the ground during administration or from eating the manure of a treated animal as the drugs are excreted in the feces.

Here are some safety tips for caring for multiple species:

  1. Keep each feed in a container with a secure lid in a safe room. Make sure the container is clearly labeled with the species for which the feed is made.
  2. Separate species at feeding time to discourage other species from sneaking food or ingesting food that has fallen on the ground.
  3. Keep feed containing ionophore in a completely separate area from horse feed.
  4. Discuss safety and health concerns with ranch help and ranch sitters so that they are aware of the dangers. Provide clear, written feeding instructions, including the exact amount to be fed.
  5. Keep the stables picked and cleared of manure.
  6. Always read the label of any supplements or medication you plan to use. Never use a product from an animal species that is not on the label unless directed to do so by your veterinarian.

Meredyth Jones

About the Author: Meredyth Jones, DVM, MS, DACVIM, is an Associate Professor of Food Animal Medicine and Surgery in the College of Veterinary Medicine at Oklahoma State University. A graduate of the American College of Veterinary Internal Medicine (Large Animal), she also holds Large Animal Consulting & Education.

Veterinary Viewpoints is offered by the faculty of the OSU Veterinary Medical Teaching Hospital. The American Animal Hospital Association-certified hospital is open to the public and provides routine and specialized care for all animal species, 365 days a year, as well as 24-hour emergency care. Call 405-744-7000 for an appointment or more information.

OSU’s College of Veterinary Medicine is one of 32 accredited veterinary colleges in the United States and the only veterinary college in Oklahoma. The college’s Boren Veterinary Medical Hospital is open to the public and provides routine and specialized care for small and large animals. The hospital provides 24-hour emergency care and is certified by the American Animal Hospital Association. For more information, visit or call 405-744-7000.

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