Samband mellan överlevnad, tillväxt och pälskvalitet hos lammen och fruktsamhet och modersegenskaper hos tackan

Abstract: There are several factors influencing the profitability of production with sheep. Two of the most important factors are ewe fertility and lamb survival. Also growth capacity of the lambs is important. This paper aims to review correlations between the ewe’s fertility and maternal behavior and lamb survival. It also includes growth of the lambs and pelt quality. The number of lambs born and weaned per ewe covered has an important role in sheep production. The ewe’s individual fecundity and ability to raise the lambs have great importance but also breed, season and year have significant influence on the amount of lambs born and weaned. The lamb survival is affected by birth weight, dystocia and sex of the lambs. Male lambs with low birth weight have especially hard to survive the first days after parturition and are more often victim for dystocia. The ewe’s maternal behavior influences the lamb survival. Older ewes tend to have better maternal behavior than younger ewes and mothers of triplets tend to have better behavior than mothers of one or two lambs. Some traits in sheep production, e.g. lamb growth and adult weight, have medium to high heritabilities and can therefore easily be improved by selection. Fertility traits have low heritabilities and are therefore harder to improve by selection and breeding. Beyond heritabilities, genetic correlations between traits are important to consider and knowledge about them is necessary when planning breeding. Also the herd environment influences lamb survival and production. It can be factors such as quality of the feeding stuff and air in the stable and hygiene. All factors together make lamb survival and production a complex system of traits, which is influenced by genetics and environmental effects. The traits are correlated and often hard to separate.