Recent trends in mastitis and fertility indicators in the United States and reasons for change

1. Session 18 Abstr. 7375  Recent trends in mastitis and fertility indicators in the United States and reasons for change

2. Source: Purdue Dairy Clipart Source: Dairy Herd Management Mastitis indicators

3. International BT-SCC limits

4. U.S. milk quality measures • Bulk tank somatic cell count (BT-SCC) • Monitored by U.S. Department of Agriculture • Data from 4 of 10 Federal Milk Marketing Orders (FMO) • Accounts for nearly 50% of US milk supply • Herd test-day somatic cell count (TD-SCC) • Herds in Dairy Herd Improvement (DHI) somatic cell testing • Accounts for 97% of US DHI herds

5. U.S. SCC (all breeds)

6. 325 300 275 TD-SCC (1000s) 250 225 200 U.S. herd size and SCC 250 225 200 Cows/herd (no.) 175 150 125 100 98 00 02 04 06 08 Year

7. 325 300 275 TD-SCC (1000s) 250 225 U.S. herd milk yield and SCC 10,250 10,000 9,750 Milk (kg) 9,500 9,250 9,000 200 98 00 02 04 06 08 Year

8. Somatic cell score (SCS) • SCS used by U.S. DHI as a mastitis indicator • Simplicity • Desirable statistical properties (nearly normal distribution) • Conversion equations • SCS = log2(SCC/100,000) + 3 • SCC = 2(SCS − 3)(100,000)

9. SCS and change in herd size

10. U.S. and Canadian SCC U.S. TD-SCC Québec BT-SCC Ontario BT-SCC

11. U.S. and New Zealand SCC U.S. TD-SCC New Zealand TD-SCC

12. U.S. and Irish SCC U.S. TD-SCC Irish BT-SCC

13. German SCC “No increase or decrease in SCC for German Holsteins across time” – Reinhard Reents (personal communication, 2010)

14. U.S. versus E.U. SCC monitoring Program characteristic U.S. E.U. SCC sample Individual farm Individual farm BT-SCC limit 750,000 cells/ml 400,000 cells/ml Value used Consecutive monthly BT-SCC Geometric mean of 3 monthly BT-SCC Producer suspension 3 of 5 consecutive samples over limit 2 consecutive 3-month means over limit

15. Export concerns • E.U. change in SCC sampling point from bulk truck or plant silo to individual farm (October 1, 2010, enforcement) • 3-month mean (E.U.) used as single reference for period, which allows more time to reduce future SCC • Geometric mean (E.U.) mathematically lower than arithmetic mean (U.S.) and requires recalculation

16. Geometric versus arithmetic means

17. Fertility indicators Source: BBC (Louise Cassidy) Source: English Guernsey Cattle Society

18. U.S. days to 1st breeding Holstein Jersey

19. U.S. Holstein days to 1st breeding –––1st parity –––– All parities

20. U.S. Jersey days to 1st breeding –––1st parity –––– All parities

21. U.S. non-return rates (70 days) Jersey –––1st breeding –––– All breedings 60 55 Non-return rate (%) 50 Holstein –––1st breeding –––– All breedings 45 40 98 00 02 04 06 08 Breeding year

22. U.S. conception rates Jersey –––1st breeding –––– All breedings 45 40 35 Conception rate (%) 30 Holstein –––1st breeding –––– All breedings 25 20 98 00 02 04 06 08 Breeding year

23. U.S. heifer and cow conception rates • Genetic evaluations implemented • Bulls – January 2009 • Cows – August 2010 • Single-trait BLUP evaluation within breed • Data • Calvings during 2003 or later • Parities 1–5 • Services 1–7 • Age: Heifers 1 to <2.2 years Cows ≥2 years

24. U.S. Holstein conception rates 70 6.0 ––––Heifer CR – – –Heifer BV 60 3.0 Breeding value (%) Conception rate (%) 50 0.0 ––––Cow CR – – –Cow BV 40 -3.0 30 -6.0 01 02 03 04 05 06 Birth year

25. U.S. numbers of services Holstein Jersey

26. U.S. Holstein numbers of services –––1st parity –––– All parities

27. U.S. Jersey numbers of services –––1st parity –––– All parities

28. Pregnancy rate • Allows herd managers to measure how quickly their cows become pregnant again after having a calf • Defined as percentage of nonpregnant cows that become pregnant during each 21-day period

29. U.S. pregnancy rates 30 7.5 Jersey ––––PR –––BV 28 5.5 26 3.5 Breeding value (%) Pregnancy rate (%) 24 1.5 Holstein ––––PR –––BV 22 -0.5 20 -2.5 90 92 94 96 98 00 02 04 06 Birth year

30. U.S. calving intervals Holstein Jersey

31. U.S. Holstein calving intervals –––1st parity –––– All parities

32. U.S. Jersey calving intervals –––1st parity –––– All parities

33. Herd synchronization status • Identified through χ2 analysis with herd size considered • Deviation of observed frequency of 1st inseminations by day of the week from expected equal frequency • Maximum percentage of cows inseminated on a particular day of the week • Status categories • Not synchronized • Possibly synchronized • Probably synchronized • Synchronized

34. U.S. herd synchronization (no.)

35. U.S. herd synchronization (%)

36. U.S. herd synchronization (%)

37. U.S. cows by herd synchronization (%)

38. U.S. Holstein synchronization and reproduction* *2008 breedings

39. U.S. sexed-semen use

40. U.S. sexed-semen conception rates

41. Conclusions • Large decline in U.S. SCC during last decade while herd size and milk yield increased • In spite of less stringent legal standards, U.S. SCC comparable with SCC in other countries (probably because of incentives) • U.S. days to 1st breeding declined partly because of adoption of ovulation synchronization and timed AI

42. Conclusions (continued) • Units of semen per conception increased somewhat in the U.S. • U.S. pregnancy rates decreased and calving intervals increased for decades but are improving • Use of synchronized breeding has grown in the U.S.

43. Conclusions (continued) • Use of sexed semen for heifers has grown in the U.S. • Conception rate with sexed semen 20–30% less than with conventional semen in the U.S.

44. Thank you! Animal Improvement Programs Laboratory staff – 2010