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Telomere length variation and association with age and health status.

T. Muratori



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Telomere length variation and association with age and health status.
T. Muratori*1, I. Haagen1, A. Shabtay2, M. Cohen-Zinder2, U. Lipkin3, C. Dechow1. 1Penn State University University Park, PA, 2Newe Ya'ar Research Center, Agricultural Research Organization Ramat Yishay, Israel, 3The Hebrew University of Jerusalem Jerusalem, Israel.

Telomere length (TL) is a potential health and welfare biomarker that has not been fully developed in dairy cattle. The study's aim was to examine TL variation and associations with age and the occurrence of health events. TL was available for 521 observations on 434 Holsteins that ranged from birth to 97 mo of age in 2 herds. Whole blood was collected over 2 years and stored on blood cards until DNA extraction. TL was ascertained using multi-plex quantitative PCR with primers for telomere and the reference gene (β-globin) included in the same well on 384-well plates; samples were run in quadruplicate and those with a coefficient of variation greater than 5% after removing results from one outlier well were edited from the data. The difference in the number of cycles (DCt) between detection of the TL signal and reference gene signal was analyzed with a mixed model in SAS with linear and quadratic effects of age, herd, and health status as fixed effects; health status was characterized as healthy for 467 observations not associated with a health event at the time of blood collection, diseased for 32 observations where blood was collected the week of a disease treatment, and disease follow-up for 22 observations where blood was recollected 2 weeks after the initial disease collection; diseases were analyzed as one group rather than individual diseases due to the limited number of health events. Random effects were animal and collection date within herd. The repeatability of TL was 51% when calculated as the proportion of variance associated with animal relative to total variance; the standard deviation of DCt for the random animal effect was 0.82. There was a quadratic age effect with TL increasing from birth to 3 years of age and declining thereafter. The effect of health status was significant with a DCt least-squares-means of 4.70 for the diseased group which was significantly less than both healthy (5.18) and disease follow-up (5.26) groups. In conclusion, TL is a dynamic measure that appears to vary among animals, with age, and with health status.

Keywords: telomere, health, variation.