The effects of four levels of endophyte-infected fescue seed in the diet of pregnant pony mares.

Mean weight of 20 Quarter Horse placentas on a wet basis was 3.27 +/- 0.17 kg. These placentas contained mean dry fat-free tissue, DNA, RNA and collagen weights of 411 +/- 24 g, 11.2 +/- 0.6 g, 12.4 +/- 0.7 g and 210 +/- 15 g, respectively. In Ponies and Quarter Horses, there was a trend towards a decrease in these 4 values as gestation length increased. Analysis of placentas of Ponies fed different amounts of endophyte fungus-infected fescue seed showed that weight of dry fat-free tissue increased with increasing percentages of fescue seed in the diet. Diets containing fescue seed resulted in heavier placentas containing more dry fat-free tissue, DNA, RNA and collagen than placentas from mares fed the control diet containing no fescue seed. In mares fed 45% fescue seed, 3 of the 5 foals born suffered from abnormalities: 2 died and one was saved from suffocation in the placenta. No effects of toxic tall fescue were apparent in foals from mares fed the lower levels of fescue seed (15 or 30%).