I have bred thousands of cattle on time insemination protocols and am here to tell you, there is no short answer to your question. Obviously, even in a time/force breed using GnRH, you always like to grab ahold of a firm, toned up cervix and feel really good about putting a straw in that female. However, we have done some projects where we keep very detailed records of how each cow/heifer palpates and there are a lot of those females that have a cervix that would feel very similar to a linguini noodle that do, in fact conceive. A few things to consider on the 2 cows that did not show any signs of heat 72 hrs after cidr pull:
1) How long ago did she calve? There is no substitute for post-partum days
2) Was the vagina obviously inflamed or was there any "odd" colored discharge at time of force insemination? Many times, when using cidrs, as clean as one tries to be when inserting the cidr, you drag manure or other foreign material into the vagina, causing infection. This is the main reason I am not a fan of using cidrs for conventional synchronization.
3) Did she have any calving problems? Big calf, abnormal presentation, retained placenta, twins?
4) What has she been eating, and for how long? This time of year especially, some people will stop feeding hay and kick their cows out on pasture in the middle of the breeding season. Normally I suggest that you either continue to feed hay or whatever ration they have been on until you are done a.i.ing or switch the cows over to fresh pasture no less than 7-8 days prior to attempting to breed them. Change of diet is never good for getting cows to cycle.
5) How old is she? Many times in sychronized groups of cows, after 96 hours of heat detection, you are left with the thin 2s and 3s nursing big calves and the old grandma cows that have lost some teeth and have lost some condition and are obviously not on the gain. Cows that are not gaining or at least maintaining body condition cannot cycle.
6) Body Condition! Similar to question number 4 but yet different. Thin cows are behind the 8-ball for getting bred. Cows distribute energy in a very distict sequence. Body mass maintenence first, milk production second and reproduction last. Basically, if a cow is deathly thin, she won't milk because she is pouring every ounce of energy she consumes into herself. A thin cow will milk, but not cycle. A cow in moderate flesh, on a balanced ration and gaining weight will do it all. It's really that simple.
Hope this helps you to analyze your situation and maybe come up with a good reason why your cows did not come into heat.
