Useful Information

Do Your Cows Fit Your Ranch?

by Christine Mushrush | Published August 11, 2022

This is one question we are constantly asking, and when we pay attention our cows will give us the answer. Certainly, they tell us with a pregnancy diagnosis each fall, with their body condition score and their production record (progeny weaning ratios). But to really fine tune our selection so that our factory functions at optimal efficiency, we have to look in far greater detail than simply pregnant or open.

With annual cow costs being significantly higher than they were just a decade ago, we can’t leave any lost revenue on the table, nor can we justify extra time, labor and feed for cows that take more days to deliver their next calf. Simply put, a pregnant vs. open diagnosis no longer provides enough information. Even among cows that check pregnant, there are substantial differences in profitability created by differences in their average calving interval as well as the distribution of their calving dates throughout the calving season. Working with other seedstock producers, commercial cow/calf operations, and with the help of cattle data management specialists we have participated in the development of a new phenotypic measurement of cows’ reproductive efficiency.

This is not an EPD meant to be used across herds, but rather a tool to compare the reproductive fitness of cows within their respective herds.  This was presented, for the first time in our March 2022 sale catalog as CIV (Calving Interval Value), and it identifies differences in the repeatability of each bull’s dam’s average calving interval as well as the distribution of her calving dates versus the rest of the herd.

How CIV Works

CIV looks at two components of a cow’s annual reproduction: Most Probable Calving Interval (MPCI) and Calving Season Distribution (CSD). In simplistic terms, CIV = MPCI + CSD

The weightings are established by the economics. Calves that are born earlier in the calving season are gaining weight sooner and therefore heavier at weaning. Cows that have fewer calves over their lifespan because they have longer calving intervals incur more feed cost, or are more likely to drop out of the herd after only two or three calves and fail to recapture their development expense.

The data for both MPCI and CSD are centered around herd average and the trait units for both is days. So an MPCI value of +30 represents a cow whose most probably calving interval is 30 days longer than herd average. Whereas an MPCI value of -10 represents a cow whose calving interval is 10 days shorter than herd average. Similarly, a CSD value of +45 represents a cow whose calves average being born 45 days after the average calving date, and a -14 would represent a cow whose calves average being born 14 days ahead of the average calving date.

Note: herds that breed heifers ahead of cows will not have a 365-day calving interval.  For example, if a cow does everything right and breeds first service A.I. for her yearling and 2-year-old service, then she’d have a 395-day calving interval where heifers are bred 30 days ahead of the cows.  If she breed’s just as early for her third calf, her calving interval will drop down to 380.  If she repeats that for her 4th calf her calving interval will drop to 375 days.  So she’ll get closer to 365 days but may never get there.  But remember, she’s being measured against her herdmates, so her most probable calving interval (MPCI) will compare very favorably.  

Using CIV

The trait units for CIV are dollars ($) and reflect differences in the economic value of cows’ MPCI and CIV. In general, those cows that maintain a Most Probably Calving Interval that is very close to herd average and have CSD values that reflect calves born earliest in the calving season will have the highest $CIV. Those females that breed first service AI as heifers and every year thereafter will understandably have the highest CIV values. Also, a cow can have a relatively low calving interval, but because her calves are consistently born later in the calving season, she will still have a less desirable $CIV value.


1) Herds that breed all cows and heifers utilizing Synchronized A.I. programs tend to have a more lopsided calving season distribution than herds that rely 100% on natural service sires.

2) Herds with a shorter breeding season will have lower variation in CIV values.

3) Herds that cull late calving cows will also have less variation in CIV values.

Thank you for reading our article. If you have any questions, comments or would like to receive our 2023 bull catalog next spring to have access to this data, please contact us at info@mushrushranches.com.