1 / 21

Trait Selection When Culling U.S. Holsteins

This study analyzes trait selection in U.S. Holsteins over 20 years, focusing on culling decisions based on milk yield, fitness traits, and conformation records. It identifies trends and emphasizes on different traits across parities. Results show changes in emphasis over time, with implications for genetic improvement strategies.

felipek
Download Presentation

Trait Selection When Culling U.S. Holsteins

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Trait Selection WhenCulling U.S. Holsteins H.D. Norman, J.L. Hutchison, J.R. Wright, and M.T. Kuhn Animal Improvement Programs Laboratory http://aipl.arsusda.gov Agricultural Research Service, USDA, Beltsville, MD, USA dnorman@aipl.arsusda.gov 301-504-8334

  2. Changes in trait selection • More traits available for selection • Assignment of economic weights in genetic indexes • Economic information on benefits and costs associated with traits • Estimation of phenotypic and genetic relationships among traits

  3. Objectives • Determine emphasis currently placed on different yield and fitness traits when culling during the first 3 parities • Document trends in trait emphasis when culling over the last 20 years

  4. Data • Yield (milk, fat, true protein), somatic cell score, days open, dystocia score, and conformation records • U.S. Holsteins that 1st calved between January 1982 and October 2000 by 36 months of age • Dairy Herd Improvement herds on test for 1600 days after cow’s 1st calving date • Identified sires • Calving intervals of 270 to 650 days

  5. Models • Yield and somatic cell score Y = H + S + e • Days open and dystocia score Y = A + C + H + S + e • Final score and linear type traits Y = A + D + H + S + e Y = trait A = age group H = herd-calving season C = calendar month S = survival group D = lactation stage e = residual

  6. Defining survival groups • 1st-parity analysis • Cows with 1st parity only • Cows with 1st and 2nd parities only • Cows with 1st, 2nd, and 3rd parities only • Cows with 4 parities or more • Alternate 1st-parity analysis • Cows with 1st parity only • Cows with 2 parities or more

  7. Defining survival groups • 2nd-parity analysis • Cows with 1st and 2nd parities only • Cows with 3 parities or more • 3rd-parity analysis • Cows with 1st, 2nd, and 3rd parities only • Cows with 4 parities or more

  8. Differences in 1st-parity milk yield (kg) by survival group Differences in 1st-parity milk yield (kg) by survival group

  9. Differences in 1st-parity somatic cell score by survival group

  10. Differences in 1st-parity days openby survival group

  11. Differences in 1st-parity dystocia scoreby survival group

  12. Differences in 1st-parity final scoreby survival group

  13. Results for other parities • 2nd-parity differences within 15% of 1st-parity differences except for days open and dystocia score • Less difference in survivor advantage for days open over time compared with 1st parity • Differences for dystocia score about half those for 1st parity • 3rd-parity differences similar to those for 1st and 2nd parities

  14. Trait emphases*(%) during 1st-lactation culling *Relative to 100% for milk yield (on standardized trait basis)

  15. Conformation trait emphases during 1st-lactation culling • Relative to 100% for final score • Body traits received more emphasis during 1980s (22 to 32%) than during recent years (1 to 20%) • Udder trait emphasis has remained consistent (40 to 64%) • Emphasis on udder depth had greatest increase (from 13 to 41%) • Emphasis on feet and legs increased slightly • Emphasis on dairy form decreased (from 50 to 23%)

  16. Trait emphases*(%) during 2nd-lactation culling *Relative to 100% for milk yield (on standardized trait basis)

  17. Trait emphases*(%) during 3rd-lactation culling *Relative to 100% for milk yield (on standardized trait basis)

  18. Conclusions • Relative emphasis among traits when culling has remained reasonably consistent since 1982 regardless of parity • Protein yield received nearly the same emphasis as milk yield • Emphasis on fat yield was slightly lower than on milk yield (72 to 91%)

  19. Conclusions • Increased emphasis being placed on lower somatic cell score in later parities • Culling emphasis on days open has increased, and clearly more given for later parities • Culling emphasis on dystocia score was low relative to milk yield (7 to 19%) • Emphasis on final score when culling was low relative to milk yield (22 to 38%)

  20. Application Knowledge from this study could be useful for: • Selection by artificial-insemination organizations of bulls to progeny test or to retain in active service consistent with trait priority of dairy producers • Development of culling-decision software with index-style culling guide • Optimal genetic gains at minimal cost

  21. Acknowlegments • Tom Lawlor, Holstein Association USA, for providing Holstein conformation data.

More Related