Faecal worm egg counts (FEC) were recorded on 779 lamb progeny in a performance recorded flock in Northland during summer-autumn 1990 to determine breed and sire variations. Progeny were ram lambs born in 1989 representing 4 Perendale, 4 Romney and 7 cross-bred sires. The study protocol was that the lambs remained undrenched until the mean FEC of representative 'monitors' reached 1000-1500 eggs/g. Then all stock were faecal sampled, drenched and the protocol repeated. Full samplings occurred on 12 February (FEC1) and 12 March (FEC2). All animals grazed as one mob throughout the programme. There were significant variations within and between breeds in FEC. Perendale and Crossbred lambs had significantly lower faecal egg outputs than Romneys on both occasions (FEC1=3560, 4073, 4757; FEC2=2535, 3242, 3737, respectively). One possible explanation of the results is that Perendales selectively avoid parasite contamination on pasture through differences in grazing behaviour. Alternatively, they may have consumed less pasture and larvae because they were lighter. If these are not the cases these data suggest that Perendales in this flock may be more resistant to internal parasites.

BG, Ward, RW Purchas, and AY Abdullah

Proceedings of the New Zealand Society of Animal Production, Volume 52, , 33-36, 1992
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