Why a horse lives only 25 years approximately and a human can live 80 years? What biological process determines the lifespan of different animals? Why the animal size don’t interfere in that, since some turtles can easily live more than 100 years.
In: Biology
There’s a wide variety of reasons, many of them often species-specific (eg. genetic changes predisposing them to neoplasia, energetically expensive breeding strategies, particular physiologic or anatomic reasons, etc.).
In the case of horses *typically* their 20’s is when they start running out of reserve crown in their cheek teeth and are unable to break down fibrous feeds and they are unable to meet their nutritional needs or develop esophageal choke and develop pneumonia and die. With complete senior feeds we can circumvent this and many horses are able to live into their 30’s. Neoplasia (cancer), orthopedic complications, arthritis, chronic diseases like PPID/Equine Cushing’s predisposing them to laminitis are also things that start to become more likely at that age.
For elephants (which are another big animal) running out reserve crown is also a big one. But neoplasia is (probably) less common due to higher gene copy numbers of some tumor suppressor genes.
I might be wrong, but I believe a study was done that showed animals tend to die around after their cells have gone through roughly 5000 mutations. Just a potentially noteworthy thing
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