Penicillin's Effects on Castrated Horses

Giving procaine penicillin before and after castration reduces the levels of inflammatory markers on a horse's blood test, which suggest that this approach might reduce bacteria in the surgical wounds, according to a Danish study.

The researchers gave a non-steroidal anti-inflammatory drug (NSAID) and three days of procaine penicillin, which is a combination of penicillin and procaine, a local anesthetic agent that is available in most feed stores, to 24 stallions, which were castrated under field conditions (standing, sedated) and compared them with 26 stallions that received an NSAID alone.

"We investigated signs of inflammation in blood samples from two groups of horses undergoing castration: horse receiving antibiotics in relation to the surgical procedure and a control group. The blood samples from the penicillin-treated horses showed that in this group, inflammation was lower than in the controls, and thus, it seems that the antibiotic treatment is of benefit to the horse," said Stine Jacobsen, DVM, PhD, of the University of Copenhagen.

"In addition, horses with signs of inflammation in the preoperative blood sample had an increased risk of developing complications after the surgery," she added, suggesting that a blood test before castration might predict the occurrence of postoperative infection. If there are signs of inflammation, owners might consider postponing castration for a week or two until inflammation has subsided, she suggested.

If providing procaine penicillin resulted in less inflammation after castration, that could mean there are fewer bacteria in the wound. Bacteria can be present in surgical wounds without causing obvious clinical infection, but still slow down the healing of the wound, and the penicillin-treated horses might have benefitted from the penicillin through reduction in bacterial numbers, she said.

More studies are needed to find out whether horses can be made more comfortable (by reducing soreness, edema, stiffness, etc.) after surgery, as well as suffer fewer postsurgical infections, by using penicillin.

The study, "Administration of perioperative penicillin reduces postoperative serum amyloid A response in horses being castrated standing," was published April online ahead of print in Veterinary Surgery.

The abstract is available on PubMed.

About the Author

Marie Rosenthal, MS

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