Two experiments evaluated the effects of dietary supplementation on maternal reproductive parameters. In Experiment 1, 16 mares were assigned to dietary treatments: control, flaxseed, or linseed meal for 16 wk. Blood samples were analyzed for progesterone (P4), serum chemistry panel values, and fatty acids. Flaxseed supplementation increased (P < 0.01) alphalinolenic acid concentration, but treatment had no other effects. In Experiment 2, 45 multiparous ewes were allotted to dietary levels of metabolizable protein (MP): 60% (MP60), 80% (MP80), or 100% (MP100) from d 100 to d 130 of gestation. At d 130 ewes were slaughtered and tissues harvested. There was a day x fetal number interaction for P4, estradiol 17β, and thyroxine (T4) along with a treatment x fetal number interaction for T4. There was a day effect for cortisol and triiodothryonine. Results indicate dietary supplementation alters maternal parameters including hormones and fatty acids.