Experiences with Our Techniques for the Recovery of Nematode Larvae from Herbage
Washing a representative sample of herbage in a commercial washing-machine.
Collecting larvae on a 25 μm sieve.
Concentrating larvae in a saturated magnesium sulfate solution.
Counting and differentiating larvae microscopically.
Drying the herbage to a constant weight at 70°C.
Calculating the number of larvae/kg dry herbage.
We have used this technique routinely since 1973. Twentyfour to 30 samples were usually processed for microscopic examination by one person during a working day of eight hours. The microscopic examination took another 10 to 25 minutes per sample, mainly depending on the number of larvae to be differentiated. The rate of recovery was approximately 60%. No significant differences between replicate samples processed and counted by different individuals could be traced.
There was a close correlation between the arithmetic mean of two duplicate larval counts of a pasture and the total worm burdens of the gastrointestinal tract of 28 tracer calves. Duplicate herbage samples had been taken on the days on which a tracer calf was put on, or taken from, a pasture used by first season stock. The calves had been reared wormfree from one week to three months of age before being turned out, and for 16 or 17 days after housing when they were autopsied and examined quantitatively for their gastrointestinal worm burdens.
KeywordsMagnesium Sulfate Worm Burden Saturated Salt Solution Nematode Larva Herbage Sample
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