Ovulation rates in ewes selected for resistance to facial eczema and the effect of exposure to zearalenone

J.F. Smith, A.G. Campbell, N.R. Towers, N.R. Cow, L.T. McGowan and C. Wesselink

Ruakura Agriculture Centre, Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1988, 48: 135-138

In 1986 the ovulation rates of 21 Romney ewes selected for facial eczema (FE) resistance (R) and 27 selected for FE susceptibility (S) were recorded on day 5 of the cycle following synchronisation of oestrus with controlled internal drug releasers (CIDR) at the end of April. The ewes were then all dosed daily with 10ml of slurry of a culture of Fasarium containing 6mg zearalenone for 10 d. The ewes were re-examined for post-treatment ovulation rate.

The resistant ewes had a higher ovulation rate pre-treatment than did the susceptible ewes (R=1.90 and S=1.50). Both groups showed a decline in ovulation rate after zearalenone treatment (R=1.35 and S=1.22).

In 1987 Romney ewes from 4 FE resistance selection flocks (Model resistant (MR) n=148; Model control (MC), n=105; Resistant (R), n=110 and Susceptible (S), n=73) were examined by laparoscopy at the beginning of April. The ovulation rates were higher in the resistant flocks (MR = 1.73; MC = 1.55; R = 1.55; R = 1.42 and S = 1.29).

These data indicate that the higher reproductive performance of FE resistant ewes could in part be due to their higher ovulation rates but that resistance to FE confers no protection against the effects of zearalenone.

Keywords: NZSAPAB; Facial eczema; ovulation rate; resistance; zearalenone; Romney

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