Dear Jacob, the presence of little blood in follicular fluid may be normal during aspiration. But, large amounts of it may be caused by wrong puncture way.

Dear , you may find useful information in links below:

vri.cz/docs/vetmed/58-10-527.pdf

Article In vivo collection of follicular fluid and granulosa cells f...

Article Occurrence and characteristics of residual follicles formed ...

Dear Jacob.

I did many punctures and I experienced (in some cows and mares) the same problem. However it wasn't every time. As Seyed proposed, there may be a wrong way of puncture. Just try to use other way.

Do you have blood clots or just blood in your sample? If there are clots think of increasing concentration of for example heparin. If there is just blood I don't think it is a big deal. I also use system with syringe and when I see that there is a blood in syringe I immediately filter the content through embryo filter.

There is a different way of oocyte aspiration in mares, you need to scratch the follicular wall to get the oocyte, and therefore the blood may appear in the syringe. On the other hand in cows it is not necessary. Do you just puncture the follicle, aspirate the FF and then you leave to collapsed follicle? If so I don’t see any reason why you should be getting blood in every aspirate. As you probably know you should be very gentle when aspirating the follicle. I sometimes feel that the tissue (rectum, ovary) is somehow fragile and in these animals I experienced increased blood content in syringe. In case you want to share your experience or talk more about this topic don’t hesitate to contact me.

Regards,

Jiri