Growth and physiological responses to toxicosis in lines of mice selected for resistance or susceptibility to endophyte-infected tall fescue in the diet - PubMed (original) (raw)

. 1997 Aug;75(8):2165-73.

doi: 10.2527/1997.7582165x.

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Growth and physiological responses to toxicosis in lines of mice selected for resistance or susceptibility to endophyte-infected tall fescue in the diet

W D Hohenboken et al. J Anim Sci. 1997 Aug.

Abstract

In three experiments, mice from lines selected for resistance (R) or susceptibility (S) to growth depression from endophyte-infected fescue seed in the diet were fed diets containing infected (E+) or non-infected (E-) seed. Activities of liver enzymes known to participate in oxidation, reduction, or hydrolysis or in conjugation of xenobiotics were measured in these mice. In all experiments, E+ caused greater reduction in initial ADG of S than of R mice. In Exp. 1, liver cytochromes P450 and b5 activities were not affected by line, diet, or their interaction. These enzymes were not evaluated in subsequent experiments. In all experiments, glutathione-S-transferase (GST) and uridine diphosphate glucuronosyltransferase (GRT) activities differed between lines. Resistant mice had significantly higher GST activity on both diets in Exp. 1, on E- in Exp. 2, and on E+ in Exp. 3. Resistant mice had higher GRT activities on E+ in Exp. 1, on E- in Exp. 2, but after 4 wk on either diet in Exp. 3. Before test diets were imposed in Exp. 3, GST and GRT activities were higher in R-line mice. Divergent selection created lines that differed in response to tall fescue in the diet. Postweaning growth of resistant mice was less severely depressed by E+, although susceptible mice later expressed compensatory gain. Activities of two detoxification enzymes generally were higher in livers from R-line mice, suggesting a biochemical mechanism for the difference. Using such traits, it may be possible to select ruminants for resistance to fescue toxicosis.

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