The effect of Booroola on fat content and fat quality of carcasses in crosses with German Mutton Merinos

Taking actual consumer demands into consideration possible influences of fe cundity genes, like that of the Australian Booroola Merino (FecB), on fat c ontent, fat distribution and fat quality of lamb carcasses are of special i nterest. Within a project investigating the introgression of the FecB-gene into German Mutton Merino (GMM) in total 144 male lambs with different port ions of Booroola (B) were tested between 1995 and 1997. The animals were fe d ad lib. a pelleted grain mixture from 20 up to 42 kg body weight. There a re no differences in kidney fat percentage, subcutaneous fat thickness, per centage fat of the loin as well as intramuscular fat (IMF) between carcasse s of B-crosses (1/8 or 1/16 B) and GMM. Differences in the fat score disapp ear in lambs of the third backcross generation. The offspring of heterozygo us carriers has a higher percentage of intermuscular fat and less IMF. B-cr osses show lower melting points in IMF and kidney fat, which corresponds wi th changes in the fatty acid composition. Also the ratio between linoleic a nd linolenic acid was higher, especially in the offspring of gene-carriers. In general the differences between GMM and the involved B-crosses are smal l and unfavourable estimations of the carcass quality by the consumers are unlikely. Obvious there is no pleiotropic effect of the FecB-gene on fat co ntent, distribution and quality. Correlated effects appear only in a few tr aits and show no evidence in crossbred lambs with even or less than 1/16 B.