Abstract

It is debatable whether or not genotype influences follicle- stimulating hormone (FSH) secretion in the Booroola ram. Where differences in FSH have been reported, these may have been due to effects of sire, breed and age rather than Booroola genotype. The aim of this study was to determine if these factors do influence FecB gene expression in plasma FSH concentrations in the Booroola ram. A total of 45 Booroola rams of known genotype, breed, age and sire were blood sampled (10 ml by jugular venepuncture) once daily for 11 days, castrated, bled once daily for further 13 days, and then three times weekly for a further 7 weeks. There were no gene-specific differences in mean plasma FSH concentrations before or after castration, or in the rate of the post- castration rise in FSH, between FecBFecB (BB) and Fec+Fec+ (++) rams. This was consistent when data from rams of three ages (1, 2 or 3 years) and of either Booroola Merino or Booroola Romney breeds were combined, or when genotypes, were compared within breeds, or within ages. There was, however, a significant effect of sire on plasma FSH concentrations, which was evident before but not after castration. These results suggest that variation in FSH between sire groups may explain differences previously attributed to genotype.

CA, Morris, JE McCall, RL Baker, and BR Southey

Proceedings of the New Zealand Society of Animal Production, Volume 52, , 133-136, 1992