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Title: Factors affecting milk ELISA scores of cows tested for Johne’s disease

Author
item Norman, H
item Wright, Janice
item BYREM, T - ANTEL BIOSYSTEMS

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/4/2009
Publication Date: 7/12/2009
Citation: Norman, H.D., Wright, J.R., Byrem, T.M. 2009. Factors affecting milk ELISA scores of cows tested for Johne’s disease. Journal of Dairy Science. 92(E-Suppl. 1):386(abstr. W7).

Interpretive Summary:

Technical Abstract: Infection with Mycobacterium avium subsp. paratuberculosis (Johne’s disease) has been estimated to cost dairy producers over $1.5 billion per year. The objective of this study was to examine the influence a number of environmental and genetic factors have on ELISA milk test scores for Johne’s disease collected through the Dairy Herd Improvement Program (DHIA). Means and standard deviations for ELISA scores were 0.04 and 0.18. SAS GLM was used with the following model: ELISA Score = Test year + parity + test stage + season of birth + test season + residual. Test scores remaining (29,389) with information on all effects designated in the model were from 25 herds and 139 herd-years. Animals tested in parity 1, 2, 3, and >=4 represented 49%, 25, 13, and 13%. Days from calving to T stage in 60 d increments through >=361 d were 10, 7, 6, 9, 23, 22, and 23%, respectively. Seasons of birth (Jan. – Mar., Apr. – June, etc.) were 22, 25, 27, and 26%; test seasons were 25, 22, 23, and 29%. Test for 2002, 2003, … , 2008 (2008 was an incomplete year) were 3, 6, 12, 16, 19, 26, and 17%. Least square differences (LSD) between years were significant (-0.04, -0.03, -0.01, 0.00, 0.01, -0.00, and 0.00), between parities were significant (parity 1 to >=4 were -0.03, -0.01, 0.01, and 0.0), as were those between stages (stage 1 to 7 were -0.02, -0.03, -0.02, -0.02, -0.02, -0.02, and 0.00). Interactions were examined also between parity and stage and revealed that ELISA scores were higher near peak yield (61 to 120 d) in parities 1 and 2 in relation to later stages than these were in parity 3 or 4. Seasons of birth and test seasons were both non-significant. Variance components were estimated with AIREMLF90 software using the same model as above, but with random sire and cow added. The heritability was low (1%), while the repeatability was moderate (21%). These results will be reexamined with substantially more DHIA data that has already been collected, and is currently being edited.