New research in the Journal of Dairy Science, shows that increasing the supply of metabolizable protein and adding rumen protected methionine to the transition diet boosts dry matter intake before and after calving.
Cardoso et al. (2021) evaluated 3 diet strategies for transition cows: (1) 14% crude protein, (2) 16% crude protein and (3) 16% crude protein plus rumen protected methionine (RPM). To create the 16% protein diets, a high RUP soybean meal was used, which resulted in greater levels of metabolizable protein in the high protein diets. The high protein plus RPM diet was formulated to deliver a 3:1 ratio of lysine to methionine.
Cows were assigned to 1 of 3 diets 18 days before the expected calving date. After calving, the cows were switched to a lactation diet that maintained the difference in protein levels. The treatment period extended through 45 days in milk.
During the prepartum period, all cows fed the higher protein diets ate more feed than cows fed the low protein diet, 29.1 lbs, 25.6 lbs and 22.9 lbs per day for high protein plus RPM, high protein and low protein diets, respectively. Postpartum intake was greater for cows fed the high protein diets, too; 40.3 lbs, 38.6 lbs and 36.6 lbs per day for high protein plus RPM, high protein and low protein diets, respectively. Both greater protein supply and RPM supplementation had a positive effect on DMI.
While there was a slight increase in milk yield, 74.3 lbs, 70.9 lbs and 68.8 lbs per day for cows fed the high protein, high protein plus RPM and low protein diets, it lacked statistical significance (P = 0.10). RPM supplementation did increase milk fat and total solids concentrations of milk and improve cows’ insulin concentration prepartum. Cows fed high protein diets also had decreased IL-1 at calving (inflammatory cytokines) compared to cows fed the low protein diet.