There is no more unnerving feeling than hearing the veterinarian say “open” too many times during preg-check. Having some open cows is normal in a 60-90 day breeding season. However, if the number of open cows is excessive (greater than 6-10%), evaluation of management, nutrition and herd health needs to take place.
Research illustrates a strong link between body condition score (BCS) of cows and their ability to breed back. Cows in better condition (BCS >5) have a greater probability of breeding early and a greater chance at becoming pregnant and staying pregnant. Thin cows at calving generally do not breed up well. Remember back to calving… were cows thin? This may be the cause of poorer preg-check.
Nutritional plane or the weight gain pattern may also be the problem. Cattle losing weight often do not get pregnant or stay pregnant. Thus, if cattle were losing weight at time of breeding, then likely they would not conceive in high percentages. Drought, washy grass, and poor hay quality can be reasons for not meeting cow energy requirements
Handling stress, especially transportation of cows, can result in stress that can affect conception. It’s best to not haul or stress cows 4 to 45 days after breeding. This coincides with embryo implantation, a sensitive time when trying to get a cow pregnant. 
Drought and other environmental anomalies can stress plants, creating toxins. Feeds containing high levels of mycotoxins, nitrates, prussic acid, etc. can be responsible for abortion. Testing high risk feeds is a must. Eliminating the feed from the ration or addition of a toxin binder may be necessary. Animals eating poisonous plants can also manifest higher abortion rates.
Water is another possible source of contamination to animal nutrition. Excess minerals may be causing mineral interactions. Also, elevated nitrate levels could be present in water and hurting the ability of cows to hold a pregnancy.
Compromised herd health is worthy of investigation. Your veterinarian will have the best ability to diagnose herd health issues. Visual appraisal as well as blood work is usually needed to determine what disease may be causing failure of cattle to breed and hold a pregnancy. Some common diseases that can result in abortion or failed breeding are Anaplasmosis, Bovine Respiratory Disease (BRD), Leptospirosis, Leukosis, Johnes, and Neospora. Consult your veterinarian for more information on the possibility of these diseases being the culprit of a poor preg-check. 
Lastly, bull fertility and genetic defect status is an important factor to evaluate annually. While this is normally quite evident, it always needs to be part of this conversation. Semen checking bulls, monitoring breeding activity, and having the ability to substitute bulls is necessary in some years to maintain breeding season goals.
 

*Originally published in Progressive Cattle magazine