EFFECTS OF CONSUMING ENDOPHYTE-INFECTED TALL FESCUE ON GROWTH, REPRODUCTION AND LACTATION IN MICE SELECTED FOR HIGH FECUNDITY

Effects of a diet containing endophyte-infected tall fescue seed (83% infected) were investigated using 2 lines of mice, one line selected f or fecundity (L(+)) and the other a randomly selected control line (K) . Treatments included a commercial stock diet (C), 50% stock plus 50% non-infected tall fescue seed (N), and 50% stock plus 50% infected tal l fescue seed (I). The experiment was conducted using mice on respecti ve treatments in 2 phases (successive generations), with 15 to 23 mate d females per line and diet subgroups. Mated females of Phase 1 were a ssigned at random within line to experimental diets which were fed dur ing gestation and through 21 d of lactation. Litters were standardized to 10 pups 1 d after birth. Stock diets were fed to all groups from D ay 21 to weaning on Day 28. Weaned male and female pups were allotted to previous diets. Mated females in Phase 2 were managed as in Phase 1 through weaning at 28 d. Diets of males did not affect reproduction a nd data were pooled within female diets. Selected (L(+)) dams gave bir th to more live pups than K dams (P<0.05) during both phases (+3.4 and +2.8 +/- 0.4 pups, respectively). Diet but not line affected litterin g rate of mated females in Phase 1 (71.3%, I; <87.1%, C or 93.0%, N; P <0.05) and Phase 2 (82.1%, I<93.8%, N or 97.1%, C; P<0.05). Diet had no effect on fecundity during Phase 1 but females on I diet had reduce d (P<0.05) litter size by 1.9 and 3.2 +/- 0.5 pups compared with the f emales on N and C diets, respectively, in Phase 2. Feed consumption an d weights of dams during lactation generally ranked C>N>I. Growth of p ups during both phases also ranked C>N>I. Vaginal opening at 28 d diff ered by line (71.4%, K<89.3%, L(+), P<0.05) and diet (56.8%, I<92.0%, C or 92.2%, N, P<0.05). These results suggest both acute and chronic e ffects of consumption of endophyte-infected diets. Absence of line-by- diet interactions demonstrates that adverse effects were unrelated to genetic differences between lines.