THE EFFECT OF MITOCHONDRIAL-DNA ON MILK-PRODUCTION AND HEALTH OF DAIRY-CATTLE

Maternal lineage effects, probably indicative of mitochondrial DNA (mt DNA) differences, may be important for milk production and reproductiv e success in dairy cattle (Bas taurus). Sequence variation of mtDNA in 36 maternal lineages of dairy cattle was studied with animal models t o assess effects on milk production and reproductive traits. Cattle wi thin maternal lineages defined by registered pedigrees were assumed to be uniform for the nucleotide sequences examined. Sequence polymorphi sms of bovine mtDNA were shown to be associated with milk production, reproduction, and health costs incurred. One particular base-pair subs titution was associated with additional production of 842 kg milk and 37 kg milk fat per cow per lactation. Another single base-pair substit ution was associated with a decrease of 36 days and one unsuccessful b reeding between successive calvings. Effects of this size are economic ally important and have broad implications in genetic selection of dai ry cattle.