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Abstract
This study was undertaken to determine whether mice could be used as a small animal bioassay to study the effects of endophyte (Acremonium lolii)-infected perennial ryegrass (Lolium perenne) on growth and reproduction. Seventy-two CD-1 mice (36 males and 36 females) were randomly assigned to one of six dietary treatments and housed separately for 56 days before being allowed to cohabit for 49 days. The diets included ad libitum feeding of rations containing 50% (v/w) Purina Rodent Chow plus 50, 37.5, 25, or 0% infected ‘Grasslands Nui’ perennial ryegrass seed, and rations containing either 50% un-infected seed or 100% rodent chow restricted to the average daily intake of the 50% infected diet (pair-fed). The 37.5 and 25% diets were made to 100% with un-infected seeds. Mice fed the 50% infected seed diet did not consume less food but gained significantly less weight (P < 0.05) than the other treatment mice during the 56-day trial. All mice fed ryegrass seed gained less than the mice fed restricted chow (P < 0.05) during this time. The parturition data indicated a trend of fewer pups per litter and significantly lower (P < 0.05) total litter weight and mean weight per pup born from mice fed the 50% infected seed diet. Mice fed the 50% infected seed diet had fewer pups that survived through a 14-day suckling period, because of cannibalism. Aberrant behaviour was also noted in mice fed the toxic diets. The reduced growth rate and reproductive performance in mice fed the endophyte-containing diets may lead to a bioassay for general toxicity of endophyte-infected perennial ryegrass.
