Don't shoot until you see the whites of their eyes...

I collected lamb droppings, floated the samples in a fecalizer with a saturated solution of boric acid, made slides and examined them under a microscope at 40X.  I found but 1 parasite egg and that is  more than acceptable. 

To confirm these findings, we looked at the mucous membranes of the lambs for signs of anemia (bloodlessness) and found none: their noses were pink, as were their gums, and when we rolled back their lower eye lids we found dark red membranes, the most healthy FAMACHA score.

At this time, we will not deworm the lambs as a group even though they had been grazing with the ewes a week ago and had been exposed to parasites from their immune mothers.  Vigilance, using microscopic fecal examinations and watching for anemia, is required over the Summer months when the lambs are at pasture and most vulnerable.

It's not that a shepherd wants no parasites in her sheep, what she wants is sheep that have an immunity to the parasites they do and will have.

Sheep must develop an immunity to stomach worms, meaning they can function well despite presence of parasites; and as such, the flock is not over-treated with anthleminitics.  That overuse compromises the efficacy of the medication as has happened on many farms in the southern United States: the dewormer no longer kills the worm that kills the sheep.  So then what do you do?