Vaccines and Open Cows

[Lucky]

For as long as I can remember we have always worked cows in May after our last calf is born. This allows us to pen the cattle once, vaccinate everything, and get the calves worked. We turn bulls out May 1st so generally get them vaccinated as well. I've been reading lately that NOT vaccinating cows and bulls at least 30-45 days before turning bulls in can cause cows to abort early or not cycle. What's y'alls thoughts on this?

I hate to pen the cows April 1st and then again May 1st to catch the late calvers but if it helps with breed up it would sure be worth doing. Also hoping I haven't been causing problems by vaccinating too late.

 

[Katpau]

Apparently studies have shown reduced conceptions on cows vaccinated less than 45 days prior to bull turnout. Because of those studies, we vaccinate on about April 1st and bulls are turned out about May 15. We only leave bulls in for 60 days, and have considered cutting that to 45 days, since almost all calves are born in the first 45. We cull any cows that are open at weaning. Because we try to keep a very tight calving window, we want to make sure to give them every opportunity to conceive. I would think someone who calves over 90 or even 120 days would not need to worry as much about vaccinating just before turning in the bulls. Calving is the most stressful time of year, so I only want cows that conceive and calve early with no complications.