Research is continuing to show improved lifetime productivity for heifers that conceive early in their first breeding season. The latest research to evaluate this has come from Colorado State University (CSU) and was reported in the February issue of the Professional Animal Scientist, a journal published by the American Registry of Professional Animal Scientists (ARPAS).

The CSU researchers used over 6,500 records from more than 1,100 Angus cows at the University’s John E. Rouse Colorado State University Beef Improvement Center in Saratoga, Wyoming to evaluate lifetime performance of heifers that conceived to Artificial Insemination (AI) or Natural Service (NS) to the same bulls. Heifers were bred by AI before bulls were turned out for natural service mating so that heifers that conceived to AI were bred earlier in the breeding season than those that conceived to NS. Heifers that conceived to NS were younger at the time of first AI, indicating that they were born later in the calving season and, therefore, likely reached puberty at a later date (but not necessarily a later age) than heifers that conceived to AI.

When the two groups were compared over their lifetime, those that conceived to AI as yearlings:

  • Weaned calves that were 11 pounds heavier
  • Weaned 964 pounds more total calf weight in their lifetime
  • Weaned 2.2 more calves in their lifetime
  • Added between $922 and $975 more revenue in their lifetime

The range in reported revenues is a result of using different price scenarios for the calculation. However, the researchers concluded that the increased revenue was related to the increased weaning weights and not to the price scenario used.

This research supports other studies showing greater lifetime productivity of heifers that calve early in the breeding season. Heifer development programs that prepare heifers to conceive early in their first breeding season have long-term impacts on profitability.

For a more detailed summary of this research, you can access the abstract of this journal article.


  • J. T. French, J. K. Ahola, J. C. Whittier, W. M. Frasier, R. M. Enns, and R. K. Peel. (2013). Differences in lifetime productivity of beef heifers that conceived to first-service artificial insemination (AI) or a clean-up bull via natural service (NS) as a yearling and among females that were offspring of an AI or NS mating. Professional Animal Scientist 29: 57–63

Source: Elaine Grings