While it might be difficult within your management system to gather cows for pregnancy diagnosis prior to weaning time, please read on with an open mind to determine whether one or more of the potential advantages of earlier pregnancy diagnosis might make it worth trying on your operation. Keep in mind, there may be a year in which environmental conditions (e.g., drought leading to limited forage) might make it the right choice in that particular year.
Potential advantages of earlier pregnancy diagnosis:
1. Marketing open cows earlier in the season when cull cow prices are higher may yield a greater return. The value of this should not be overlooked. A significant portion of the gross profit on a cow-calf operation comes from the sale of cull cows. Ask yourself this question: What fraction of my cows have covered their heifer-raising, feed and ranch overhead costs? It is not unlikely that some cows only turn you a net profit on the day that you cull them. Maximizing – or, better, optimizing – the return on culling day can contribute significantly to your bottom line.
2. Depending on the body condition score of the individual cow, placing an open cow on feed for a short period of time prior to marketing may also yield a greater return. The cost-benefit for this will, of course, vary year to year based on feed price, your ability to correctly predict the future sale price, etc.
3. Removing open cows from the pasture leaves more forage for the remaining cows.
4. Following the identification of the pregnant cows, they can then be segregated into a herd with bull calves and a separate herd with heifer calves to avoid unintended pregnancies in the heifer calves.
5. If cows are body condition scored at the time of pregnancy diagnosis and thin cows are segregated and managed in a different pasture with better forage or supplemental feed, then (with earlier pregnancy diagnosis) they will have more time to “catch up.”
6. If using artificial insemination, then – with earlier pregnancy diagnosis – you will be more able to determine which cows are pregnant to A.I. vs. natural service. It is much easier for your veterinarian to accurately assess the age of the fetus when pregnancy diagnosis is performed when all pregnancies are less than or equal to approximately 100 to 120 days of gestation. Stated in a different way: The earlier that it is done, the more accurately it can be done. “Pregnant to A.I.” versus “pregnant to herd bull” can potentially be a deciding factor in a culling decision if a specific cow is “on the bubble.”
7. As mentioned above, earlier pregnancy diagnosis helps a veterinarian better predict calving dates. Thus you can be reasonably confident regarding which cows will calve early in the calving season versus those who will calve later. Potential advantages of this include the opportunity to minimize population density in the calving area – leading to decreased disease incidence in the calves by not moving later calvers into the calving area at the start of the season – and the opportunity to cull a cow who is “on the bubble” if she is a late calver. Remember, every 21 days later that a cow calves leads to approximately a 50-pound decrease in pounds of calf weaned. Furthermore, if the cow is a late calver this year, then she will likely be a late calver next year.
8. Earlier pregnancy diagnosis – along with disciplined culling of open cows – enables you to improve herd fertility faster by allowing cows that do not become pregnant promptly under your management, in your environment, to cull themselves.
9. If you choose not to try earlier pregnancy diagnosis in the cows, at least try it in the heifers. Open heifers can be sold at a younger, more appropriate age to enter the feedlot, and they may bring a higher price. Remember, there is no excuse for a heifer to be open.
10. Notwithstanding the labels of such vaccines, there is evidence that traditional weaning time may still be too early to get the most benefit from neonatal diarrhea/scours vaccines. Pregnancy diagnosis at an even earlier time leads to the opportunity to wait and then time scours vaccine administration more appropriately. (Of course, it also means that you will need to work the cows a second time.)
There is a largely mistaken belief that rectal palpation for pregnancy diagnosis – particularly when performed early in gestation – causes pregnancy loss and potentially other problems. The results of several studies have shown that there is little to no risk to the pregnancy from rectal palpation.
If open cows are sold prior to your typical weaning time, then you’ll need to wean the calves that are nursing those cows early. Yes, this will require some facilities and feed and management. However, these calves will be old enough to wean and will likely gain more weight on feed than out with their dam (even factoring in weaning shrink). This is especially likely if you are doing it because it is a drought year.
In conclusion, timing is everything. It is indeed important to delay pregnancy diagnosis until you can capture all of the pregnancies in the cows that you want to keep. You need to decide whether you truly want to keep those late calving cows. 
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Lowell T. Midla
- Technical Services Manager
- Merck Animal Health
PHOTO: Earlier pregnancy diagnosis – 90 to 100 days – can help producers make better management and marketing decisions. Staff photo.
