From a confirmed scientific standpoint, I don't recall at what stage you need to incorporate dexamethasone into the equation in order to abort a bred cow - could probably find that with a little bit of looking, but haven't done so. But here's a tale:
We're moving toward a Fall-calving herd. Still have about 16-20 in the Spring-calving group. Spring-calving 1st-calf heifers have always been difficult to get re-bred, so, if we like 'em and they don't breed back, we roll 'em to the Fall group.
Last year, I had 5 first-calvers. At preg-check in late September, I palpated 4 of the 5 as open; the last one was skinny as all get-out, and I said "If these other girls aren't bred, there is no way this one is."
Bred the other 4 early on in the Fall breeding season, but could never catch this heifer in heat - but she was still in poor body condition, despite weaning her calf. I know we CIDRed her and gave a shot of Estrumate in the synch protocol - may have hit her with another dose 14 days or so later, 'cause she didn't show any heat. Never did show heat, so we turned her out to the bull.
Guess I should have palpated her in September, 'cause she calved out with all the other Spring cows - a nice, normal heifer calf, despite one or two doses of prostaglandin around 5-6 months gestation. (See - even us 'professionals' do stupid stuff)
That moved her up off of the 'short list' to leave - she may not be much to look at, but at least she's fertile!
Just reinforced to me that the most common cause of a cow/heifer not cycling is...she's bred.
