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Responses to alternative genetic choices in dairy grazing systems

Responses to alternative genetic choices in dairy grazing systems. 1. 2. 3. 4. 5. Phenotypic trend in days open. Lactation. Benefits of improved reproduction. Lower semen cost Improved ability to optimize lactation and lifetime yields

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Responses to alternative genetic choices in dairy grazing systems

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  1. Responses to alternative genetic choices in dairy grazing systems

  2. 1 2 3 4 5 Phenotypic trend in days open Lactation

  3. Benefits of improved reproduction • Lower semen cost • Improved ability to optimize lactation and lifetime yields • Reduced culling due to delayed or failed conception • More herd replacements

  4. Bull fertility evaluations • Estimated Relative Conception Rate (ERCR) • 70-day nonreturn rate (NRR) Source: • DRMS (Raleigh, NC), 1986−2005 • USDA (Beltsville, MD), 2006−present • Western Bull Fertility Analysis • 75-d veterinary-confirmed conception rate • Source: AgriTech (Visalia, CA), 2003 −present

  5. ERCR distribution (Aug. 2007)

  6. New service sire evaluation coming • Based on conception rate rather than NRR • More accurate • Inseminations from most of the United States • All services (not just first) • Additional model effects included • Available in Spring 2008 • Documentation at ftp://aipl.arsusda.gov/pub/outgoing/BullFert/

  7. Pregnancy rate (PR) • Percentage of nonpregnant cows between 50 and 250 days in milk that become pregnant during each 21-day period • Advantages over days open (DO), the days from calving to conception • Easily defined • Information from nonpregnant cows included more easily • Larger (rather than smaller) values desirable

  8. PR (continued) • PR = [21/(DO − VWP + 11)]100 • Voluntary waiting period (VWP) assumed to be 60 days • Factor of +11 adjusts to middle day of 21-day cycle • Examples • Herd with average of 133 DO has PR of 25% • Herd with average of 154 DO has PR of 20%

  9. USDA pregnancy rate • Linear approximation • PR = 0.25 (233 − DO) • 1% higher PR = 4 days fewer open

  10. Current breed averages

  11. Daughter pregnancy rate (DPR) • First USDA genetic evaluations in 2003 • Same across-breed animal model as for yield traits, productive life (PL), and somatic cell score (SCS) • Heritability of 4%

  12. DPR (continued) • Predicted transmitting abilities (PTAs) reported as percentages • Daughters of bull with PTA DPR of 1 expected to be 1% more likely to become pregnant during estrous cycle than if bull had PTA DPR of 0 • Each increase of 1% in PTA DPR equals a decrease of 4 days in PTA DO • PTA DO approximated by −4 × PTA DPR • Example: Bull with PTA DPR of +2.0 would have PTA DO of −8

  13. 1 2 3 4 5 Phenotypic trend in days open Lactation

  14. DPR trend (August 2007 base)

  15. Bull PTA DPR frequency (Aug. 2007)

  16. NM$ CY$ PTI FM$ 2008 Application of selection indexesfor dairy producers H.D. Norman Missouri Dairy Summit (16)

  17. Lifetime merit indexes

  18. Genetic merit of high-DPR Holstein bulls

  19. Genetic merit of high-DPR Holstein bulls

  20. Genetic merit of high-DPR Holstein bulls

  21. Genetic merit of high-DPR Holstein bulls

  22. Genetic merit of high-DPR Holstein bulls

  23. DPR benefits to herd • Decreased units of semen needed per pregnancy • Decreased labor and supplies for heat detection, inseminations, and pregnancy checks • Additional calves produced • Higher yields because more ideal lactation lengths

  24. Lifetime value • Factors in determining economic value to DPR • Loss of about $1.50/DO • 2.8 lactations per cow • No breedings for half of cows during final lactation • Correlation of heifer and cow fertility (0.3) • Value of extra calves • Other unmeasured health expenses • Total lifetime merit value of $21/PTA DPR unit

  25. What genetic programs work well for U.S. graziers?

  26. Grazier breeding • Objective • Cattle with better fertility or other desired characteristics • Approaches (occasional use) • Bulls from countries that practice grazing • Bull breed different from cow breed to capitalize on heterosis • Effectiveness in grazing herds?

  27. Genetic alternative • To achieve top fertility, consider direct selection for daughter fertility • U.S. bulls with high DPR • High fertility bulls from all sources

  28. Comparison study • Daughter performance within U.S. herds • New Zealand AI Holstein/Friesian bulls • Other AI Holstein bulls (predominantly U.S.) • Cows included • DHI records in AIPL national database • Calved (1st parity) before December 2006 • Time to express the performance traits

  29. Traits examined • Milk, fat, protein • Somatic cell score • Days open • Conformation traits

  30. Yield and SCS data • First-lactation daughters (239 herds) • 896 sired by 40 New Zealand bulls • 13,251 sired by 1,888 U.S. bulls • Second-lactation daughters (211 herds) • 680 sired by 34 New Zealand bulls • 10,927 sired by 2,283 U.S. bulls • Third-lactation daughters (181 herds) • 453 sired by 29 New Zealand bulls • 7,403 sired by 1,784 U.S. bulls

  31. Yield results • Milk U.S. daughter superiority • First lactation 983 lb*** • Second lactation 1,115 lb*** • Third lactation 772 lb*** • Fat New Zealand daughter superiority/advantage • First lactation 10 lb** • Second lactation 4 lb • Third lactation 11 lb • Protein U.S. daughter superiority/advantage • First lactation 10 lb*** • Second lactation 12 lb*** • Third lactation 5 lb

  32. Economic value • Current U.S. milk prices • MFP$ = 0.016  milk + 1.50  fat + 1.95  protein • U.S. daughter MFP$ superiority • First lactation $20.76 • Second lactation $34.80 • Third lactation $6.21

  33. SCS results • First lactation • U.S. daughter superiority of 0.15*** • Second lactation • U.S. daughter advantage of 0.09 • Third lactation • New Zealand daughter advantage of 0.05

  34. DO data • First-lactation daughters (219 herds) • 816 sired by 38 New Zealand bulls • 9,747 sired by 2,113 U.S. bulls • Second-lactation daughters (189 herds) • 614 sired by 33 New Zealand bulls • 9,747 sired by 2,113 U.S. bulls • Third-lactation daughters (161 herds) • 392 sired by 28 New Zealand bulls • 6,561 sired by 1,637 U.S. bulls

  35. DO results • First lactation • New Zealand daughter superiority of 8 days** • Second lactation • New Zealand daughter superiority of 7 days** • Third lactation • New Zealand daughter advantage of 2 days

  36. Type data • First-lactation daughters • 100 sired by 14 New Zealand bulls • 376 sired by 225 U.S. bulls

  37. Type results • Final score • U.S. daughter superiority of 1.5 points* • Strength • N.Z. daughter scored higher by 1.9 points* • Rear legs • U.S. daughter scored higher by 2.4 points* • Foot angle • N.Z. daughter scored higher by 1.7 points*

  38. Type results (continued) • Body condition • N.Z. daughter scored higher by 2.3 points* • Rear udder height • U.S. daughter superiority of 1.8 points* • Udder depth • U.S. daughter scored higher by 3.3 points*** • Teat placement • U.S. daughter scored higher by 2.3 points*

  39. Spring-calver subset • In addition to studying all herds using New Zealand bulls, a “grazing” subset was defined by seasonal calving • Number of March–May calvings more than 3 times number of September–November calvings for at least 3 of 5 years during 2002–06 • At least 25 reported calvings per year

  40. Spring-calver data • First-lactation daughters (18 herds) • 222 sired by 18 New Zealand bulls • 2,536 sired by 203 U.S. bulls • Second-lactation daughters (23 herds) • 153 sired by 16 New Zealand bulls • 1,845 sired by 243 U.S. bulls • Third-lactation daughters (14 herds) • 97 sired by 13 New Zealand bulls • 1,043 sired by 13 U.S. bulls

  41. Spring-calver yield results • Milk U.S. daughter superiority • First lactation 762 lb*** • Second lactation 1,102 lb*** • Third lactation 1,064 lb*** • Fat New Zealand daughter advantage • First lactation 11 lb • Second lactation 5 lb • Third lactation 5 lb • Protein U.S. daughter superiority/advantage • First lactation 11 lb* • Second lactation 16 lb* • Third lactation 12 lb

  42. Spring-calver SCS results • First lactation • U.S. daughter superiority of 0.24** • Second lactation • U.S. daughter advantage of 0.12 • Third lactation • U.S. daughter advantage of 0.17

  43. Spring-calver DO results • First lactation • U.S. daughter advantage of 4 days • Second lactation • New Zealand daughter advantage of 3 days • Third lactation • Days open averaged the same for both

  44. 2008 Conclusions H.D. Norman Missouri Dairy Summit (44)

  45. Conclusions • Strain differences between U.S. Holsteins and New Zealand Friesians for several traits • Higher milk and protein yields for U.S. bull daughters; higher fat yield in 1st lactation for New Zealand bull daughters • Superior 1st-lactation SCS for U.S. bull daughters

  46. Conclusions (continued) • Fewer 1st- and 2nd-lactation DO for New Zealand bull daughters • Higher strength and body condition score for New Zealand bull daughters • Better rear udder height, udder depth, and teat placement for U.S. bull daughters

  47. Caution • Strain differences observed influenced by individual bulls chosen from each country • Slightly greater selection intensity for New Zealand bulls than for U.S. bulls

  48. Recommendations to breeders • Usual Recommendation: Don’t select bulls solely on one trait because many traits have economic value • Consider economic value of all performance traits in your own market when making genetic choices • Dairies with seasonal calving should find an index that puts more weight on daughter fertility than those recommended for the general industry

  49. Selection for bull fertility • Breeding to bulls with higher conception rates returns a profit fairly quickly • Premium of $2 could be paid for semen per 1% improvement in fertility • Thus, a unit of semen from bull with ERCR of +2 is worth $8 more than a unit from bull with ERCR of −2 • Use bull fertility as a secondary selection trait after picking bulls on their economic indexes

  50. Selection for cow fertility • Selection for improved fertility will pay off, even though the benefit is delayed for 2 years • Choose your sires based on lifetime economic merit that includes daughter fertility, rather than for daughter fertility alone • However, producers with herd fertility problems could emphasize DPR extensively with little loss in overall net merit

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