South African Journal of Animal Science
On-line version ISSN 2221-4062
Print version ISSN 0375-1589
SCHOLTZ, A.J. et al. Divergent selection for reproduction affects dag score, breech wrinkle score and crutching time in Merinos. S. Afr. j. anim. sci. [online]. 2012, vol.42, n.3, pp.274-279. ISSN 2221-4062.
Merino lines that were divergently selected from the same base population from 1986 to 2009 for their ability to rear multiples were assessed for dag score in autumn and spring, breech wrinkle score, and crutching time. Animals in the Low (L) line had higher dag and breech wrinkle scores and took longer to be crutched than High (H) line contemporaries. Expressed relative to H line least squares means, means of L line individuals were respectively 54%, 65%, 42% and 40% higher for autumn dag score, spring dag score, breech fold score, and crutching time. Gender effects for dag score were inconclusive, as ewe hoggets were more daggy than rams in autumn, with an opposite trend in spring. Shearer (n = 6) also affected crutching times, with an almost twofold difference in mean crutching time from the quickest shearer (27.7 ± 3.1 seconds) to the slowest shearer (49.4 ± 3.7 seconds). The inclusion of dag score and breech wrinkle score as linear covariates in an analysis on crutching time eliminated the effect of selection line. It thus seems that the quicker crutching times of H line animals may be related to line differences for dag score and, to a lesser extent, for breech wrinkle score.
Keywords : Reproduction; selection lines; shearing time; wrinkle.