No abstract

Nine methods of adjusting lamb weaning weight for the effects of age-of-dam, sex, birth-rearing rank, and weaning age were compared. Evaluated several ways, the effectiveness of the methods did not differ very much. It is concluded that the best adjustment procedures are the combined additive and multiplicative, or multiplicative alone. An exception is adjustment for weaning age effects, which should be additive.

Sources of variation in adjustment factors for weaning weight of New Zealand Romney lambs were studied. Data from 12 flocks and 6 years were used. Adjustment factors for sex differences were affected significantly by flock, year, and interactions between flock and year. Birth-rearing rank factors were affected mainly by interactions between flock and year, and age-of-dam adjustments seemed to be affected by flock and interactions. Only a small proportion of the variance in adjustment factors could be explained by flock level for weaning weight. It is concluded that some sort of flock X year specific adjustment should be carried out in flocks weaning more than about 150 lambs per year. An exception is adjustment of lambs l)orn as twins and reared as singles, where considerably larger flocks are required before flock X year specific adjustment will be better than overall adjustment.

No abstract

No abstract