Researchers at the Texas A&M School of Veterinary Medicine & Biomedical Sciences (VMBS) have discovered that phenylbutazone, a nonsteroidal anti-inflammatory drug (NSAID) often prescribed to horses, can affect the ability of a mare’s eggs to so-called ‘ova’. “- to become viable embryos, which is a crucial step in assisted reproduction in horses.
This discovery, recently published in the journal Theriogenologyis important because of the time and money horse owners often invest in assisted reproduction.
Just like humans, horses sometimes need help from science to reproduce. If they do, special steps are required for a successful pregnancy due to the unique properties of equine germ cells.
“In horses, the process of in vitro fertilization (IVF) is more complex than in humans,” says Dr. Luisa Ramirez-Agamez, a Ph.D. candidate at the Department of Large Animal Clinical Sciences (VLCS) of the VMBS, which studies equine reproduction. “First, a mare’s eggs need about 30 hours to mature in the laboratory after being collected before they can be fertilized. We then need to inject the eggs with sperm to induce fertilization, a process known as Intracytoplasmic Sperm Injection (ICSI) .
“We found that phenylbutazone, commonly known as bute, can affect both the ability of a mare’s eggs to mature properly when cultured and whether the fertilized eggs will develop into a viable embryo,” she explained . “In both cases, the bute-affected eggs cannot be used for assisted reproduction.”
The value of horse-assisted reproduction
Assisted reproduction is an important resource for many horse owners, especially those who make a living from their herds. Many horse owners also place great value on producing offspring from their favorite horses to continue their legacies.
In some cases, mares that are chronically lame and unable to support a pregnancy on their own can become egg donors, with their eggs fertilized in a laboratory and carried to term by a surrogate mother.
“This is one of the specific situations affected by our discovery,” Ramirez said. “Mares that are chronically lame are likely to be put on bute because it helps with pain management – especially in the musculoskeletal system – which, according to our results, will hinder their ability to participate in assisted reproductive programs.
“In a future study, we hope to find an alternative to bute that provides the same level of pain relief but does not interfere with reproduction,” she said.
The good news is that bute’s effect on horse eggs appears to wear off within a few weeks.
“We collected the eggs three days after treatment, then 33 days and then 77 days,” she said. “We found that eggs collected three days after bute administration failed to produce embryos, but those collected after 33 days were successful. We hope to find a more precise answer to the question of how bute in a future study affects the quality of the eggs.”
Implications for human medicine
Looking to the future, Ramirez is interested in collaborating with researchers in human medicine because of the potential implications of her discovery for IVF in women.
“NSAIDs are often given to women during IVF to delay their ovulation cycle, which means the ovaries release an egg every month,” she explained. “Under normal circumstances, most women produce only one egg per month, but IVF is expensive and time-consuming, so women are given hormones that ensure they produce more than one egg each cycle. This way there is more than one egg. NSAIDs help preventing women from ovulating early so they don’t lose those eggs.”
But after her recent discovery about NSAIDs and equine reproduction, Ramirez wonders whether NSAIDs could also have unknown negative effects on IVF.
“NSAIDs are generally thought to have a positive impact on IVF in women, but our results suggest that these drugs are not as benign for reproduction in horses,” Ramirez said. “Some NSAIDs, such as Banamine, actually cause anovulatory follicles in horses – follicles in the ovaries that do not release eggs as they should during ovulation.
“This is not the case in women, which is why NSAIDs are thought to be safe. But now we know that bute can actually prevent fertilized eggs from becoming embryos, and it is possible that some NSAIDs could have a similar effect in women,” said them. . “This is something I want to explore.”
