Authors: Lydia Hardie, Brad Heins, and Chad Dechow
Motivation
- Because organic cows receiving antibiotics may no longer produce organic milk, longevity of an organic cow takes on a different meaning than that of a conventional cow; namely it reflects more than avoiding death or chronic illness but also reflects avoiding severe acute illness such that antibiotics would be needed for healing.
- We can use the trait stayability (the ability to stay in the herd to a chosen timepoint such as to a particular lactation) to reflect longevity because it is indifferent to the reason for leaving the herd. Stayability is also a useful trait for genetic analyses because it can be measured life-long and can easily be measured on many animals, even if they have minimal information available about other traits such as milk production.
- If stayability in organic cows is positively related to national evaluations for productive life and livability, which are primarily measured on conventional cows, organic dairy producers will also see improved longevity in their cows.
Objectives
- Estimate heritabilities and genetic correlations for stayability in organic Holstein cows
- Establish genetic relationships between stayability in organic Holstein cows and nationally available traits provided in bull proofs
Conclusions
- Stayability in organic Holstein cows is similar to herd life in conventional herds, ranging from 0.07 to 0.15 depending on the time period considered.
- The genetics behind stayability are more similar between first and second lactation cows than between lactating cows and heifers.
- Selecting on productive life and livability will improve the genetics of longevity of organic Holstein cows. However, the correlations are moderate and there may be some bulls that rank differently