Horse
Depending on breed, management and environment, the modern domestic horse has a life expectancy of 25 to 30 years. Uncommonly, a few animals live into their 40s and, occasionally, beyond. The oldest verifiable record was "Old Billy", a 19th-century horse that lived to the age of 62. In modern times, Sugar Puff, who had been listed in "Guinness World Records" as the world's oldest living pony, died in 2007 at age 56.
Namib Desert Horse
Scientists studying the horses rate their body condition on a scale of one (excellent) to five (very poor), based mainly on estimated weight and muscle tone. The horses tend to remain in above average condition, despite the harsh environment in which they live, with stallions generally averaging better condition then mares. During severe droughts, the average body score decreases, but even then horses are found with moderate body scores and the entire population is never in very poor condition. The condition of the horses is directly correlated to rainfall, through a correlation to available forage, though temperature, distance between forage and water and individual energy expenditures also play a role. Studies during the 1990s found no evidence of equine disease among the population and few external parasites. Investigations of carcasses found four internal nematode parasites present (strongyles, small and large pinworms and Ascarids), as well as the larvae of botflys.