Stayability EPD Improvements

When RAAAs Stayability EPD was released in 1994 Total Herd Reporting (THR) was still in its infantcy. Due to the fact that Stayability is calculated by observing a females production record, the initial calculation of Stayability was developed for non-THR data. This calculation basically observed if a female who entered the herd (measured by determining if she weaned a calf) remained in production until she was 6 years of age. Therefore, a female who entered the herd could fail to produce a calf as a 4 and 5 year old but still receive a positive observation for Stayability if she weaned a calf as a 6 year old. Now with over a decade of THR data, research was performed to utilize THR data to its fullest extent in the new Stayability EPD calculation.
The changes that were made include:

1. Once a female enters a herd (measured by reporting a progeny) she must remain productive each year until 6 years of age in order to receive a positive observation for Stayability.
2. Females receive a negative observation for "rolling-over" to the next calving season (i.e. a female who enters production by having a calf born in the Spring will be penalized if she moves to calving in the Fall – this is not based on THR schedule).
3. Observation used for measuring Stayability was changed from a female weaning a calf to a calving observation. By using calving observation you eliminate the possibility of a female receiving a negative observation due to her calf dying for abnormal reasons.
   With the implementation of these improvements its not surprising that many animals Stayability EPD changed. Although these changes can be significant, the new Stayability EPD is certainly a better genetic prediction that you can implement to make genetic improvement.

Stayability Basics

Stayability – Predicts the probability that a bull’s daughters will remain in the herd until at least 6 years of age.
Example: Bull A has a 5 Stayability EPD while Bull B has a 15 Stayability EPD. If these two bulls were randomly mated to a group of cows, the resulting daughters of Bull B would have a 10% higher probability of remaining in the herd until at least 6 years of age as compared to the daughters of Bull A.
Or,
If these two bulls were randomly mated to a group of cows, Bull B would have 10% more daughters remaining in the herd until 6 years of age as compared to the daughters of Bull A.

If you have further questions please contact Larry Keenan at larry@redangus.org or (940)387-3502.