Halplotypes of the ovine ADRB3 gene (ADRB3) and their association with post-weaning growth in New Zealand Suffolk sheep.

The β3-adrenergic receptor (ADRB3) regulates thermogenesis and lipolysis in brown and white adipose tissue. Previously, sixteen ovine ADRB3 haplotypes have been defined. In this study, the relationship between these ADRB3 haplotypes and variation in post-weaning growth was investigated in 797 New Zealand Suffolk lambs from 38 sire lines and eight studs, using PCR-SSCP and General Linear Mixed-effects Models. Seven haplotypes were found in these sheep and they comprised five previously reported intron sequences and four previously reported 3'UT sequences. The frequencies of the various diplotypes ranged from 0.1 to 17.6% and individual haplotypes from 0.8 to 32.5%. The presence of haplotype A-b was associated with a decreased weaning-weight (P=0.001). Sheep with the B-c/F-e diplotype had a higher mean weaning-weight than those with A-b/B-c or A-b/E-e (P<0.05). The presence of C-a was found to be associated with increased post-weaning growth (P=0.008), while the presence of B-c was associated with decreased post-weaning growth (P=0.005). Sheep with A-b/C-a had higher mean post-weaning growth than those with A-b/A-b, A-b/B-c, B-c/B-c, B-c/E-e or B-c/F-e (P<0.05). Sheep with B-c/B-c had lower mean post-weaning growth than those with A-b/C-a or B-c/C-a (P<0.05). Additive effects for the different forms of the B-c haplotypes on post-weaning growth were identified. The effects of the ovine ADRB3 haplotypes on weaning-weight and post-weaning growth confirm that they could be used as a candidate gene-marker for improving sheep growth.