Resistance vs. resilience: A solvable dilema?

Selecting for resistance to gastrointestinal parasites in sheep provides an epidemiological advantage, but the anticipated improvements in productivity have been far from consistent. The timing of immune development, as judged by faecal egg counts (FEC), in lines of Romney sheep that had been selected for either resistant or resilience to gastrointestinal parasites was compared. Peak FEC and the time from which FEC remained at less than 200 eggs per gram (epg) occurred at a younger chronological age and lighter live weight in resistant compared with resilient animals (P≤0.02 for all) but at a similar relative maturity of circa 0.45 (P=0.26 and P=0.16 for peak FEC and FEC