Additional measurements on Muscle Line Cattle

Summary

This project studied the effect of selection for divergent muscling in an Angus cow herd on the performance of the steer progeny and the maternal productivity of the cow herd. Twenty years of selection have resulted in the herd comprising a Low muscle line (D muscle score); a High muscle line (C muscle score); and a Myostatin line (B muscle score) with one copy of a mutation in the myostatin gene causing muscle hypertrophy. High steers had the same growth rates, but improved feed efficiency and retail meat yield than Low steers, with no difference in meat quality. High muscled cows had similar calving rates and maternal performance to Low cows on good and poor nutrition. Myostatin steers had similar growth rates, and improved feed efficiency and meat yield to High steers, with no significant differences in meat quality. Myostatin cows had the same calving rates and maternal performance as High cows on moderate to good nutrition but their performance appeared to be reduced after 18 months on poor nutrition. Industry can be confident that moderate increases in muscling in cows will not reduce maternal productivity, but caution should be taken if using a myostatin gene to further increase muscling.