Clinical Assistant Professor in Equine Medicine Univeristy of Nottingham Burton-on-Trent, England, United Kingdom
Abstract:
Background: Telomeres maintain genomic integrity, shortening as an animal ages. Telomere length (TL) dynamics are proposed as welfare markers since stress accelerates telomere attrition (TA) rate while exercise lengthens sequences. This requires understanding normal TL dynamics at all stages of life. TA rate is greatest during high growth periods, slowing after maturation has been reached, although lengthening has also been reported to occur. TL dynamics have not been investigated during rapid growth in horses. Hypothesis: TL dynamics differ between young horses and adults. Animals: Privately-owned Thoroughbred mare-foal dyads (n=34) from one farm.
Methods: A prospective cohort study was performed. Venous blood was collected from mare-foal dyads every 3 months from birth for 12 months (T0-T4), stored at -80C until analysis. DNA was extracted from blood leukocytes and relative TL (RTL) assessed by RT-qPCR. The eHBB was the single copy gene (S) used, and RTL presented as a calibrated normalised T/S ratio (QBASE+ software), transformed into z-scores for analysis. Linear mixed models were fitted with covariates (foal sex, birth weight/mare body condition score [BCS], dam/sire age).
Results: Mare RTL did not change between timepoints. Foal RTL at T0 was not associated with mare RTL. Foal RTL was greater at T1 (p=0.017) and T4 (p< 0.001) compared to T0. None of the covariates significantly affected foal TL. Conclusions and Clinical Importance: These results demonstrate that telomere lengthening occurs in developing horses. Understanding TL dynamics including potential parental and environmental influences is fundamental to interpreting the effects of stress and exercise on TA rate.
