If you have noticed that your mares are suddenly having wide variations in behaviour, it is easy to simply denote them as mood swings. In reality, you might find that your horse is suffering from a tumour that also produces hormones which in turn cause the various problems of the horse’s behaviour.
Thus, if a quiet mare suddenly turns into an unpredictable horse that is ill-tempered without provocation, or if a mare finds itself in heat continuously, the odds are good that their animals’ hormone levels are off. While tumours are generally bad news, these kinds of tumours may actually fall into the family of the benign Granulosa Theca Cell Tumours (GTC), which occur as abnormal growths inside the ovaries.
The tell-tale sign of such a tumour having formed within the ovary is an enlargement of the affected area that may be detected via rectal palpations. To double-check your findings, you will want to have the animal undergo a rectal ultrasound that will not only verify the existence of the tumour but also give you some accurate measurements.
Another way of checking for a GTC is via a blood test which will be able to alert you to increased hormone levels. Of course, this test is not nearly as useful and accurate as the rectal ultrasound. Interestingly, the tumours may either secrete testosterone or progesterone, and the mares’ behaviour will be different according to the secretion of the hormone. The best treatment available for an affected mare is to have the ovary removed vaginally. This is an operation that is termed a colpotomy.
If, on the other hand, the ovary is too large for this procedure, the veterinarian may need to remove it via an incision made to the flank of the animal. Should the tumour have gone undetected and continued growing for an extended period of time, then a midline incision will be the only viable option for surgical removal.
There is the possibility of an ovary being misdiagnosed as containing an oversized tumour because it may present itself as being abnormal in size. This frequently happens when the end of the breeding season is approaching. In horse aficionado circles, such ovaries are referred to as “autumn ovaries.”
Still functioning normally, the ovaries simply feel enlarged; yet a rectal ultrasound will most often help a trained veterinarian to determine the difference between a benign tumour and an “autumn ovary.”
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