Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/21/2016
Publication Date: 7/9/2016
Citation: Wright, J.R., Van Raden, P.M. 2016. Genetic evaluation of dairy cow livability. Journal of Dairy Science. 99(E-Suppl. 1)/Journal of Animal Science. 94(E-Suppl. 5):174(abstr. 0368).
Technical Abstract: Predicted transmitting abilities (PTA) for cow livability (LIV) were developed to measure a cow's ability to stay alive while on the farm, whereas PTA for productive life (PL) measures a cow's ability to avoid either dying on the farm or being culled. About 20% of dairy cows die instead of being sold, with death losses averaging 7% per lactation and recorded since 1970. LIV records for 69,710,392 lactations of 25,514,760 cows were evaluated with an all-breed animal model, using edits similar to a previous study. The scale reports cow livability instead of mortality so that positive PTAs are favorable (0 = died, 100 = lived for each lactation) and reports PTA on lifetime instead of per lactation basis to express LIV differences as a percentage of all cows exiting the herd. The model uses individual lactation records for culling as a correlated trait to increase reliability of LIV. Heritability was 1.3% on the observed scale for LIV per lactation vs. 3.0% for overall culling rate per lactation. The SD of true transmitting ability for LIV was 0.82% per lactation or 2.3% per lifetime using an average of 2.8 lactations per cow. For recent bulls with > 80% reliability, LIV PTAs are correlated favorably by about 0.70 to PL, 0.45 to daughter pregnancy rate (DPR), and -0.25 to somatic cell score (SCS) PTAs, with low correlations to yield trait PTAs. The 0.70 correlation with PL seems sufficiently below 1 to add value from selecting for both LIV and PL in an index. Genomic PTAs (GPTA) for young bulls computed from 4-year truncated LIV data had squared correlations with future data about twice as high as parent averages (PAs) for LIV. Genomic reliability was 56% compared to 30% from PA, but lower than 70% for GPTA PL. Economic values for LIV and PL were estimated assuming $1,200 less income for cows that die than those sold for beef. Relative emphasis on LIV was 7% of total emphasis, but relative emphasis on PL declined to 14% from 19% currently. Thus, total emphasis on cow longevity and livability could increase to 21% using 2 correlated traits instead of 19% with just 1 trait. The United States in 1994 was the first country to evaluate longevity, and can also become the first country to evaluate cow mortality or livability as a specific economic trait.