Growth and carcass characteristics of Icelandic lambs - a review.

Studies on weight and carcass characteristics of Icelandic lambs are reviewed with emphasis on genetic parameters and genetic improvement. Direct heritability of weaning weight was found to be 0.15-0.29 and 0.11-0.18 for carcass weight. Maternal heritability was 0.27 and 0.24 for weaning weight and carcass weight, respectively. Carcass measurements representing shape and size of the carcass were highly heritable, while cross-sectional measurements of muscle and fat thickness have high or medium-high heritability. Ultrasonic measurements of fat and muscle thickness of live lambs have a heritability of 0.42-0.56, with high genetic correlations with carcass measurements of muscle and fat. Ultrasound measurements have been used as selection criteria in the national breeding scheme, as well as breeding values for carcass classification scores. Selection for more compact animals has changed the conformation of the breed in the past 50 years. Significant genetic improvement has been documented, yielding increased muscling and decreased fat of lamb carcasses.