Clinical footscald and footrot in a New Zealand Romney flock: phenotypic and genetic parameters.
New Zealand Romney flocks with a tendency to clinical footscald and footrot outbreaks were studied. There were annual variations in prevalence of footscald and footrot, and prevalence increased with age among ewes. There was a higher prevalence of footscald and footrot among ♂ than ♀ lambs. Birth rank, birth date and dam's age did not significantly affect severity of infection in lambs. Repeatability of ewe infection over successive annual inspections was low. The h2s of infection severity, presence or absence of footscald or footrot, presence or absence of footrot only, and presence of footrot with or without footscald, estimated by half-sib analyses, were 0.14, 0.28, 0.17 and 0.25 resp. The h2 of infection severity, estimated from dam-offspring regression, was 0.12. Production traits were not associated with liability to footrot. It was concluded that selection of the top 5% of progeny-tested sires for breeding would reduce the prevalence of footscald and footrot by approx. 45% per generation.