Most who work in the cattle IVF field as a commercial enterprise are, in some way or other, challenged every day. However, some situations are so challenging, they are worthy of a story to be told.
An Australian Wagyu breeder enlisted a team consisting of an experienced cattle ART vet, IVF and genetics leaders, including ourselves and SpeedBreed, Gnarwarre (near Geelong, Victoria, Australia), to deliver as many calves as possible from just two straws of semen. The genetics within those two straws was of such high value that each straw cost tens-of-thousands of Australian dollars. And to complicate things further, we had no idea how the semen would perform under IVF conditions! This was a BIG investment by the breeder – it had to work. The first decision that carried a risk was to cut one straw in half, use one half for the first day’s collection and the other for a 2nd day’s collection.
Although the OPU went well on the first day of collection (29 donor cows, providing 284 good quality COCs), and the transport maturation looked fine, there were fewer cleaved embryos than expected following IVF (51%). It gave, what we would categorise as a poor, but by no means uncommon result from untested semen. As a result, good quality embryo number was also lower than expected (56, 38% of cleaved), but this is also a characteristic of poor fertilisation. We suspected the issue was a not-optimized IVF step. The sperm motility was fine, but we know some bulls that have good AI fertility may be poor at IVF. We agreed to increase the heparin level, to twice our normal dose. This was a further risk, but we needed to boost IVF rates. It was worth it, as the cleavage rate was 75% of COCs (304 from the same 29 cows), and good quality embryo production from cleaved was just below 60% (135 embryos). For OPU-derived oocytes, this is at the upper end of the spectrum.
We are now awaiting the pregnancy outcomes, but this story is about the need to adjust practices, evaluating the risks and making decisions that really impact IVF success.