The RETP predicted transmitting ability (PTA) represents the expected resistance of an animal’s offspring to retained placenta in a herd with average management conditions. Larger, positive values are more favorable.
Retained Placenta (RETP)
RETP measures the resistance to retained placenta.
Benefits of Trait
Introduced in 2018, 2020, and 2022, genetic and genomic evaluations for resistance to retained placenta (RETP) are provided for Holstein, Jersey, and Brown Swiss males and females. Evaluations are expressed in percentage points of resistance above and below the breed average.
- Retained placenta is a common risk factor of subsequent metritis. Selecting for improved resistance to retained placenta will also improve resistance to metritis.
- The direct cost of retained placenta is approximately $68 per case. This does not include any associated costs such as decreases in production and fertility already accounted for in Net Merit.
- Producers now have an indication of an animal’s genetic resistance to developing retained placenta compared to the breed average.
Resistance to Retained Placenta (RETP)
Percentage points. The average resistance rate is equal to 96.4% in U.S. Holsteins. The resistance rate is equivalent to the incidence rate subtracted from 100.
Daughters of a Holstein bull with a RETP PTA of +2.0% are expected to have an average resistance rate to retained placenta of 98% (assuming the breed average resistance is approximately 96%). Daughters of a Holstein bull with a RETP PTA of -2.0% are expected to have an average resistance of 94%. Daughters from the bull with PTA -2.0% are expected to have three times the number of cases of retained placenta as daughters from the bull with PTA of +2.0%
Health trait evaluations, including for RETP, became available for Holsteins on April 3, 2018, for Jerseys on April 7, 2020, and for Brown Swiss on August 9, 2022.
RETP is included in selection indexes for Holsteins, Jerseys, and Brown Swiss as part of the Heath $ sub-index.
Estimated heritability is 1.0% for resistance to retained placenta (observed scale).
Young genomic bulls are expected to have reliabilities averaging 42% for resistance to retained placenta, and progeny tested bulls are expected to have genomic reliabilities averaging 47%. As additional data is accumulated, reliabilities will increase.
The largest significant (P < 0.05) correlation with PTA for resistance to retained placenta was with Productive Life PTA at 0.17. Additional significant correlations were 0.14 with Daughter Pregnancy Rate PTA, 0.13 with Cow Livability PTA, 0.13 with Cow Conception Rate PTA, and 0.12 with Heifer Conception Rate PTA.
RETP evaluations were developed using producer-recorded data collected through Dairy Herd Information (DHI) affiliates from herds across the U.S. Strict editing was applied to ensure only the most reliable data was included for the development of genetic evaluations. The edited data included a total of 2 million RETP records from 1.1 million cows. These health records are used in conjunction with lactation data available in the National Cooperator Database.
The standard deviation (variation) for RETP PTA is 0.8%. Because 1 and 2 standard deviations normally include 68% and 95% of observations, respectively, we assume about 68% of bulls will have a RETP PTA between -0.8% and +0.8% while 95% of the bulls will range from -1.6% to +1.6%.
RETP PTAs range from 2.7 percentage points below to 2.1 percentage points above average in evaluated Holstein bulls born since 1990 with reliabilities of ≥75% (December 2017).
Pre-release analysis indicates the active A.I. Holstein sires in December 2017 (614 bulls) range from -2.1% to +1.3%, with the average at approximately -0.3 percentage points.
Future Development
In the future, further model improvements and development will be researched and tested. This may include the development of a multi-trait model that incorporates multiple reproductive disorders and/or measures of fertility.
Related Publications
Parker Gaddis, K.L., J.B. Cole, J.S. Clay, and C. Maltecca. 2012. Incidence validation and relationship analysis of producer-recorded health event data from on-farm computer systems in the United States. J. Dairy Sci. 95:5422–5435. doi:10.3168/jds.2012-5572.
Donnelly, M. R., A. R. Hazel, B. J. Heins, & L. B. Hansen, 2018. Health treatment cost of Holsteins in 8 high-performance herds. J. Dairy Sci. (in preparation).
Liang, D., L.M. Arnold, C.J. Stowe, R.J. Harmon, & J.M. Bewley, 2017. Estimating US dairy clinical disease costs with a stochastic simulation model. J. Dairy Sci. 100(2): 1472–1486.
Information last updated March 2018.