Studies on Western Australian Merino sheep. III. Genetic and phenotypic parameter estimates for subjectively assessed and objectively measured traits in ewe hoggets

Abstract

Between 1440 and 2084 Merino hoggets were scored for visual traits, with the number of records differing according to the traits. Eight wool traits and seven body traits were subjectively assessed, while four wool traits and five serial liveweights were measured. Heritabilities for all subjective traits were estimated, with sire models using restricted maximum likelihood, as were genetic and phenotypic correlations between subjective and objective traits. Heritability estimates for back wool, lock thickness, wool character, underline, condition, wool colour, hock shape, feet shape, face cover score, neck wrinkle, breech wrinkle and side wrinkle were moderate (0.1 to 0.3), while those for visual fineness and wool handle were high (0.34 and 0.41), and overall score, low (0.06). Correlations between these traits and objective traits having economic value (wool weight, average fibre diameter and liveweight) were low or negligible, indicating that it may be more efficient if classing traits are not used to the exclusion of objectively measured traits. However, under some circumstances, they may have potential for increasing selection efficiency or used as an inexpensive first step in a two-stage selection procedure.