Flexible testing and use of milk-only records

P.M. VanRaden*1, G.C. Fok1, L.R. Bacheller2, G.B. Jansen2, and J.A. Carrillo2

1USDA, Agricultural Research Service, Animal Genomics and Improvement Laboratory, Beltsville, MD 20705-2350, USA
2Council on Dairy Cattle Breeding, Bowie, MD 20716

2022 J. Dairy Sci.


National genetic evaluation software assumed that fat yield was always recorded and excluded milk-only records. Milking systems often can accurately measure and record milk volume, but inline estimation of milk components is more difficult. Edit programs were revised to begin using milk-only records in April 2022 in the multi-trait evaluation of yield traits. Other trait groups such as cow fertility and health also will have more usable records because edits for those traits require having usable yield records. Herd variance ratios had been estimated from 1 trait (milk yield since 1992 and then fat yield since 2007) and applied to adjust all 3 traits (milk, fat, and protein). Since 1998 when data collection ratings (DCR) were introduced, milk and fat received the same weight calculated as an average of the DCR values for milk and components instead of separate weights because of software limitations. Programs were revised to use trait-specific variance adjustments and weights, to include milk-only records, and to remove much obsolete code. Most milk-only records are unsupervised and therefore get the same reduced weights and extra edits for percent milk shipped and percentage of valid ID as other owner-sampler herds. Lactation weights for milk, fat, and protein now use 3 separate DCR based on the testing patterns and correlations among test days within lactations. New and official genetic evaluations were compared from December 2020 data. Numbers of usable lactation records were 98,269,605 for milk, 97,393,419 for fat, and 78,044,073 for protein, indicating that 876,186 milk-only records were added. Correlations of new with previous PTA were > 0.9995 across all bulls for all 3 traits and were > 0.997 for bulls born since 2007 with > 50% reliability. The SD of PTA increased slightly by 1.3% for milk, 2.1% for fat, and 2.4% for protein but reliability also increased a little from the extra records. Further research could help adapt to more flexible testing options and automated data collection that continue to increase in popularity.