Reproduction and Enzyme Detoxification Activities in Mouse Lines Selected for Response to Fescue Toxicosis

In previous work, one mouse line was selected for resistance to fescue toxicosis (R) and a second line was selected for susceptibility (S) based upon reductions in post-weaning growth rate caused by an endophyte infected diet. The first objective of the current experiment was to determine whether long term reproduction of S mice was more severely depressed than that of R mice by the toxic diet. The second objective was to quantify glutathione-S-epoxytransferase (GST) and uridine diphosphate glucuronosyl-transferase (UDPGT) activities in livers of R and S dams from the experiment and to determine whether reproduction during continuous cohabitation and liver detoxification enzyme activities were correlated within genetic line x diet groups. Twenty-eight mating pairs per line x diet combination, resistant mice fed a non-toxic diet (R-), resistant mice fed a toxic diet (R+), susceptible mice fed a non-toxic diet (S-) and susceptible mice fed a toxic diet (S+), were cohabited continuously for 36 wk. Effects of the toxin-containing diet on the number of offspring born, the number of pups weaned, and litter weights were detectable (P < .01) within the first litters produced. Reproductive variables were more seriously influenced by the toxic diet within the S line than the R line when these measures were compared within four equal time phases. The effects of the toxic diet on reproduction were greatest early in the experiment; by the fourth time phase,