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Title: ASSESSMENT OF VOLUNTARY WAITING PERIOD AND FREQUENCY OF ESTRUS SYNCHRONIZATION AMONG HERDS

Author
item Miller, Robert
item Norman, H
item Kuhn, Melvin
item CLAY, J - DRMS

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2005
Publication Date: 7/24/2005
Citation: Miller, R.H., Norman, H.D., Kuhn, M.T., Clay, J.S. 2005. Assessment of voluntary waiting period and frequency of estrus synchronization among herds [abstract]. Journal of Dairy Science. 88(Suppl. 1):301.

Interpretive Summary:

Technical Abstract: Lactation stage when cows are first inseminated (voluntary waiting period, VWP) and extent of estrus synchronization (ES) were examined. Data were 5,551,562 lactations with first inseminations from 1995 to 2002. Annual herd means were computed for days in milk until first service (D1). For each herd-year, cumulative distribution of D1 was grouped as <=30, <=40, <=50, <=60, <=75, <=90, <=120, <=150, and <=200 d. For 3377 herds on DHI test, mean D1 were 89, 91, 92, and 95 d for 1995 through 1998, respectively. For 1995, cumulative frequencies were 1, 3, 9, 22, 45, 64, 84, 93, and 98% for the 9 lactation stages; corresponding frequencies for 1998 were 1, 3, 8, 19, 40, 58, 80, 90, and 97%. First insemination was later in lactation in 1998 than in 1995. Herd VWP was defined as days in milk when 10% of cows had been inseminated for the first time. For 1995, cumulative frequencies of herds with VWP of <=30, <=40, <=50, <=60, <=75, and <=90 d were 1, 7, 33, 78, 98, and 100%; corresponding frequencies for 1998 were 1, 5, 28, 72, 96, and 99%. Thus, >50% of herds had VWP of <60 d. Intraclass correlation of D1 was 0.70, which suggested consistency in lactation stage at first insemination across years within herds. To identify ES herds, a chi squared was calculated for each herd-year to detect differences in frequencies of first inseminations by weekday. Herd-years were classified into 4 groups: 1) chi squared < 22.46, 2) 22.46 <= chi squared < 100, 3) 100 <= chi squared < 250, and 4) chi squared >= 250. In 1995, 91.2, 8.0, 0.8, and 0.1% of herds were in those groups, respectively; corresponding percentages for 2001 were 77.2, 15.7, 4.4 and 2.7. If groups 3 and 4 contained ES herds, then ES frequency steadily increased from 0.9% in 1995 to 7.1% in 2001. Mean herd D1 and services per cow were 95.4 and 2.1 for group 1 versus 74.0 and 2.5 for groups 3 and 4. Fertility data from ES herds may require different treatment than those from herds using traditional estrus detection.