Reproduction and lactation in the rat : a bioassay for fescue toxicity

The objective of this research was to develop a quick, easy to interpret, inexpensive bioassay of potentially dangerous fescue pastures. A further aim was to identify the mechanisms of action of the toxin(s) of fescue in aglactia and abortion reported to occur in mares.

The feeding of ground fescue hay to laboratory rats may be an effective way to assay for fescue toxicity, thus circumventing the tedious and costly process of extraction in developing a dependable bioassay of toxic fescue. Although the results of using extracts of fescue and the ground hay are similar, neither adequately distinguishes between toxic or non-toxic forages when reproductive efficiency and lactation of rat dams are assessed. However, the rat pups seem to be able to distinguish the toxic from the non-toxic forages as a result of in utero changes. The gestation ration fed to dams influenced pup survival in this study (P<.01) and pup hemoglobin (P<.05). Conducting the bioassay at low (1.1 C) environmental temperatures enhanced the toxic effects of the fescue on pup survival. Pups nursing fescue fed dams had a lower (40%) survival rate than did the controls (90%).