Pet Forum / Mammals / Rats / December 2007

This article seems to show that the administration of tylosin over a two
year period extends rats lives:

http://www.inchem.org/documents/jecfa/jecmono/v29je08.htm

(about halfway down the page)

Groups of about 25 male and female Harlan rats (total 213)
   received 0, 0.001, 0.01 or 0.1 % tylosin base in their diet for 2
   years. Survival was better in tylosin treated groups than in control
   rats (54% and 30% respectively). No effects were seen on growth,
   haematology, or relative organ weights. Macroscopy and microscopy
   revealed an increased number of animals with fatty changes in livers
   and kidney at all dose groups and a slight increased incidence of
   bile duct proliferation at the 0.1 and 0.01% levels, but neither was
   dose-related (Anderson et al., 1966; Study R10-58).

In another 2-year study groups of Harlan rats (30/sex/group)
   were fed diets containg 0, 0.01, or 1.0% tylosin base. Survival was
   better in rats fed tylosin than in control rats (57% and 29%
   survival in high dose and control rats, respectively). No effects
   were seen on growth, haematology, urinalysis, organ weights,
   macroscopy and microscopy. A dose-unrelated increase of fatty
   changes in liver and kidney was observed. (Anderson et al., 1966;
   R3-59).

Seems to indicate that a rat NOT on tylosin has about a 1 in 3 chance of
making it to 2 years whereas a rat on tylos has a better than 1 in 2 chance
of making it.