There is good evidence that telomeres predict variation in health and longevity, yet it is unclear whether these patterns are causally derived from telomeres per se, in part because relatively little research directly manipulates telomere length during early life, when telomere shortening is most dynamic. Here, we test how the telomerase activator TA-65 (i.e., cycloastrogenol) affects telomere length in five tissues during the peak of growth in the wild tree swallow (Tachycineta bicolor). Following 8 days of oral TA-65 administration, chicks experienced telomere lengthening in the blood and accelerated feather growth, but no changes to mass over time. TA-65 did not affect telomere length in the brain or spleen and led to shorter telomeres in the liver and adrenals. This whole-organism experimental manipulation of telomere dynamics therefore reveals limitations to telomere protection and biological senescence. In doing so, this work advances our understanding of early-life telomere dynamics and their potential role in generating future variation in health and lifespan.

Chicks were orally administered water or TA-65 for 8 consecutive days during early postnatal growth (4 to 12 days post-hatching). Each day, chicks were weighed. For each chick, blood was collected pre and post-treatment (4dph and 12dph), and for a subset of chicks, 4 non-blood tissues (i.e., brain, spleen, liver, adrenals) were collected at the end of the study.

DNA from all tissues was extracted using a Promega Maxwell RSC instrument, and telomere length was quantified for all DNA using qPCR. This dataset uses either 2^deltadelta Ct values (for relative telomere length of non-blood tissues) or a corrected change in telomere length (corrected for regression to the mean) for blood samples.

7 chicks have missing blood telomere lengths at 12-days old either because they didn't survive to that age (n=6), or had bad qPCR replicates (n=1).

A few chicks have 1+ days missing for mass, either because a nest was forgotten for one day (n=1, 5 chicks total) or because the chick died.

Datasets:

"ChickALLData" is used to compare blood telomere dynamics and wing length between treatments

"ChickGrowthRepeated..." is used to compare growth/mass between treatments (repeated measures)

"TissueRTLStacked" is used to compare non-blood tissue telomere lengths between treatments (repeated measures)