Testosterone levels and parasites
- From: James Michael Howard <jmhoward@xxxxxxxxxxxxxxxx>
- Date: Tue, 11 Jul 2006 11:58:30 GMT
Dtsch Tierarztl Wochenschr. 2006 May;113(5):178-81.
Influence of sex on the resistance of sheep lambs to an experimental
Haemonchus contortus infection.
Gauly M, Schackert M, Hoffmann B, Erhardt G.
Institute of Animal Breeding and Genetics, University of Gottingen, Germany
36 intact male and 69 female lambs of two breeds (n = 63 Merinoland; n = 42
Rhon) aged 12 weeks were orally infected with 5000 infective-stage larvae,
L3, of the nematode Haemonchus contortus. After 4 and 8 weeks faecal egg
counts (FEC), haematocrit values and plasma testosterone levels were
determined. All lambs were slaughtered at 20 weeks of age. The
gastrointestinal tracts were examined for the presence of adult stages of
H. contortus. Male lambs showed significantly higher log FEC (p < 0.001),
higher mean establishment rates (p < 0.05), higher worm burdens (p < 0.01)
and lower haematocrit values (p < 0.001) when compared with female lambs.
Correlations between economically important traits (body weight, daily
weight gain) and parasitological parameters were significantly higher in
male animals. Testosterone level was 4 weeks after infection significantly
positive correlated with worm burden. The results suggest that female lambs
are more resistant against an experimental H. contortus infection when
compared with male lambs. Testosterone seems to play an important role in
resistance. This approach can be of importance if parasite resistance is
incorporated into breeding programs and the estimated breeding values for
rams are only based on male offspring information. Therefore male breeding
values are probably not representative for the whole population.
.
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