The blood draw was about four hours after she was given her hay, so even if she was breaking a fast, there was enough time that it wouldn't have greatly impacted the insulin number. Even if having the hay was impacting her result, it would not have driven her insulin levels to 357uIu/ml.
When did she receive her last hay the evening before? A fast means a time interval of more than 6 hours between when the horse last ate something (which isn't the time you last provided food) and when it starts eating again. This applies to any time of the day/night. You can give hay later the night before, or provide more at that last feeding so it last longer and/or make sure the first hay of the day is fed earlier than four hours before the vet is due. If the vet is coming later in the day, just be sure to provide small amounts of hay over the course of the day so the horse never goes more than 6 hours without eating something.
Lavinia, George Too, Calvin (PPID) and Dinky (PPID/IR)
Nappi, George and Dante Over the Bridge
Jan 05, RI