Genetic evaluation of dairy cow livability J R

Genetic evaluation of dairy cow livability J. R. Wright* and P. M. Van. Raden Abstract 16043 Animal Genomics and Improvement Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705 -2350 � http: //aipl. arsusda. gov INTRODUCTION Reasons for disposal have been reported and stored in Dairy Herd Improvement records since 1970 (large amount of potential data) About 20% of cows die instead of being sold (across all lactations) Death loss per lactation averages 7% (higher for later parity, lower for earlier parity) Productive life (PL) measures cow’s ability to avoid dying or being culled Livability (LIV) measures cow’s ability to stay alive LIV is a subset of PL ($1, 200 more value based on dead cow = $0, culled cow = $1, 200) DATA & METHODS Data – 92 million lactation disposition records – 32 million cows LIV definition – Reverse of mortality (0 = died this lactation, 100 = lived this lactation) – Multiplied by average lactations per cow (2. 8) to put on same lifetime scale as PL – Expressed as percentage of all cows leaving the herd Methodology – Multitrait model with PL (by parity) using similar edits as for other traits (PL by parity not reported) – Records pre-adjusted for herd variance – Variance estimated by parity using sire-model REML (allowed for use of over 5 million 1 st-parity records) RESULTS (cont. ) Heritability – Ranged from 0. 004 (parity 1) to 0. 007 (parity 5) – 0. 0062 across parities Means and SD for PTALIV Breed Bulls* (no. ) Ayrshire 246 Brown Swiss 692 Guernsey 182 Holstein 45, 840 Jersey 3, 893 Milking Shorthorn 64 Mean (%) 0. 5 0. 1 – 0. 3 – 1. 1 – 0. 2 0. 7 Genetic trend for LIV SD (%) 2. 0 3. 5 2. 2 1. 7 1. 9 *Bulls with birth year of 1990, 50 daughters, and REL for PTA LIV of 0. 50) Correlation of PTALIV with PTA of other traits Trait Holstein* Jersey* Milk yield 0. 09 – 0. 08 Fat yield 0. 21 0. 01 Protein yield 0. 16 – 0. 01 PL 0. 70 0. 54 SCS – 0. 28 – 0. 07 Daughter pregnancy rate 0. 40 0. 54 Cow conception rate 0. 40 0. 33 Heifer conception rate 0. 28 0. 32 *Bulls with birth year of 1990, 50 daughters, and REL for PTA LIV of 0. 50) or CONCLUSIONS LIV correlation with PL (0. 70) seems sufficiently below 1 to add value from selecting for both LIV and PL LIV evaluations for bulls and cows will be released by CDCB later this year Future plans include incorporation of LIV into Net Merit with ~ 7% emphasis A similar LIV evaluation for heifer calves is under development, though data is much more limited