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Title: Phenotypic and Genetic Relationships of Common Health Disorders with Milk and Fat Yield Persistencies from Producer- Recorded Health Data and Test Day Yields

Author
item APPUHAMY, A - VPI & SU
item CASSELL, B - VPI & SU
item Cole, John

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2008
Publication Date: 4/1/2009
Citation: Appuhamy, A.D., Cassell, B.G., Cole, J.B. 2009. Phenotypic and Genetic Relationships of Common Health Disorders with Milk and Fat Yield Persistencies from Producer-Recorded Health Data and Test Day Yields. Journal of Dairy Science. 92(4):1785-1795.

Interpretive Summary: This study investigated phenotypic and genetic relationships of milk and fat yield persistencies to health disorders in dairy cows. Test day milk weights and producer recorded health data were used. Disease traits for mastitis, and metabolic, reproductive, and locomotive disorders were developed. Phenotypic associations were examined in terms of the impact of persistency on disease incidence and vice versa. A bivariate linear-threshold model was used to estimate the genetic correlations. Results showed that increasing persistency is associated with reduced mastitis incidence specifically in late lactation. Genes predisposing cows to ketosis, mastitis, and displaced abomasums were associated unfavorably with persistency.

Technical Abstract: The objective of this study was to investigate phenotypic and genetic relationships of common health disorders in dairy cows to milk (PMY) and fat (PFY) yield persistencies. Health and production data from 398 commercial dairy herds were used. Disease traits were developed in binary form for individual lactations considering mastitis only during the first 100 DIM (MAST1), only after 100 DIM (MAST2) and at any stage of lactation (MAST), and reproductive disorders (REPRO), metabolic disorders (METAB) and lameness (LAME). PMY and PFY were defined to be uncorrelated with 305 d yield. Impact of the diseases on PMY and PFY were investigated separately in first (FL) and later (LL) lactations. Phenotypic associations of PMY and PFY with likelihood of diseases in current and next lactation were examined using odds ratios from a logistic regression model. A linear-threshold model was used to estimate the genetic relationships of displaced abomasums (DA), ketosis (KET), metritis (MET), MAST, MAST1, and MAST2 with PMY and PFY across parities. METAB and REPRO had significant positive relationships with PMY and PFY in both FL and LL. MAST1 tended to associate with significantly greater PMY and PFY in LL. MAST2 was related to significantly lower PMY and PFY in both FL and LL while cows affected by MAST tended to have significantly less persistent lactations. Incidence of MAST and MAST2 tended to decrease for increasing PMY and PFY in present and previous lactation. Heritability of disease incidences were 0.03, 0.01, 0.10, 0.02 to 0.05, 0.02, and 0.04 to 0.10 respectively for DA, KET, MAST, MAST1, MAST2, and MET. DA, KET, MAST, MAST1, and MET had unfavorable genetic correlations of 0.35, 0.46, 0.17, 0.02 and 0.27 with PMY and 0.16, 0.21, 0.07, 0.06, and 0.12 with PFY. Favorable genetic correlations of -0.24 and -0.04 were found for MAST2 with PMY and PFY respectively. Results suggest that diseases in early lactation increase persistency of milk and fat. Selection for greater lactation persistency must consider these antagonistic relationships.