BMR silage genetics consistently offer higher NDF digestibility compared to standard (non-BMR) silage hybrids but this advantage currently comes at the cost of poorer agronomics and upwards of a 15-20% yield reduction. The increased feed intake coupled with lower yielding hybrids makes having an adequate land base essential for successful BMR adoption.
While BMR agronomics are improving, Eastridge (1999) focused attention on the variability in animal response to BMR in a summary of 10 BMR dairy trials where these was no consistent pattern in DMI and no consistent response in milk yield to level of BMR silage in the diet.
One of the first full lactation studies (Longuski, 2003) where BMR was fed only in the lactation diet (not in the transition diet), showed significantly higher 3.5% fat corrected milk yields from 50 to 150 days in milk (DIM) compared with the isogenic control silage but was similar from 0 to 50 and from 150 to 300 DIM.
This variability in response to BMR diets led several universities and research institutions to investigate when cows were most responsive in milk production by feeding BMR at different stages of the transition and lactation cycle. The economic and agronomic merits of this approach of targeted BMR feeding is based on these research studies. The full studies can be found in the references but only the overall conclusions of the effect of selective feeding of BMR on DMI, FE and milk production will be presented in this paper.