Putative quantitative trait locus affecting birth weight on bovine chromosome 2

A genome scan for chromosomal regions influencing birth weight was performe d using 151 progeny of a single Hereford x composite bull and 170 microsate llite markers spanning 2.497 morgans on 29 bovine autosomes. A QTL was iden tified at the telomeric end of bovine chromosome 2 (maximum effect at 114 c M) accounting for approximately 2.8 kg of birth weight or 0.64 residual sta ndard deviations (after adjustment for sex of calf, age of dam, and breed o f dam). No significant effect on growth from birth to weaning was detected in this region. The presence of this QTL within a resource herd composed of breeds common to the Northern Great Plains provides an opportunity to init iate marker-assisted selection to reduce birth weight with minimal effect o n postnatal growth. Thus, potentially the amount and degree of dystocia can be reduced and the economic loss associated with calving difficulty lessen ed without compromise of subsequent growth performance. In addition, this f inding indicates that significant genetic variation for birth weight (and p resumably other production-related traits) exists within herds composed of commercially adapted Bos taurus germplasm.