“My mare had a reaction to the extender”… Did she really?
Well, we’ve certainly written about this before, but it’s worth covering again before we get going with the bulk of the AI work this season.
So, you have a couple of attempted cycles of AI… and it looks like you’re one of the unlucky ones. Your mare isn’t pregnant. You’re talking to the vet/AI technician/stud staff and they say:
“I think she’s having a reaction to the extender”
or
“The semen has been extended with an egg yolk extender and she’s having a reaction”
Well, it sounds kind of plausible initially, but actually some very nice research from last year suggests that this really isn’t the case. Palm et al (2008) infused phosphate buffered saline, seminal plasma, milk-based extender, and egg-yolk based extenders into the uteruses of 8 mares over four cycles, changing what was infused on each cycle, in alternating order. They then used lavage and biopsy to look at the immune response to each different infusion.
The results were very interesting. Similar immune responses were seen after uterine infusion with PBS, seminal plasma, and milk-based extender. The least pronounced immune response was seen after infusion with egg-yolk-based extender. Essentially, an immune response is a natural response to any substance getting into the uterus. Whether it’s semen, extender, or saline, an immune response (”reaction”) is perfectly natural.
The only thing that might cause any sort of adverse reaction in a semen extender might be the antibiotics contained in the extender. In fact, we heard a very interesting piece of anecdotal evidence this week about a mare we were working with last year. The mare failed to conceive on several consecutive cycles. A reaction to the egg yolk extender was eventually blamed, and the mare conceived when inseminated with raw semen directly after a collection. This year, the mare has been treated for a minor infection, and has been found to be extremely sensitive to a range of antibiotics. Almost all commercially available semen extenders contain a broad-spectrum antibiotic, and it is fairly likely that this factor was the main cause of her failure to conceive; due to an allergic reaction of the endometrium to antibiotics.
Milk and egg yolk are fairly innocuous, and it’s really not plausible that they would cause an allergic reaction in the endometrium. If you’ve ruled out other problems, then consider an antibiotic sensitivity, but don’t blame the semen extender!
