This experiment was conducted to test a hypothesis that lactating dairy cows fed 35 percent brown midrib (BMR) corn silage and 25 percent alfalfa hay (dry matter basis) would consume more DM around peak lactation compared with those fed conventional corn silage, resulting in longer peak milk production.
Twenty-eight multiparous Holstein cows were used starting at the onset of lactation through 180days in milk (DIM). Treatments were formulated to maintain a forage-to-concentrate ratio of 60:40, differing only in the CS hybrids used. Two dietary treatments were assessed in a completely randomized design: total mixed ration based on conventional corn silage and total mixed ration based on BMR silage.
Through peak lactation (1–60DIM), DM intake was not different between dietary treatments, whereas DM intake post-peak lactation (61–180DIM) tended to increase by feeding the BMR diet compared with the conventional corn silage diet (25.8 vs. 24.7kg/d). Cows fed the BMR diet tended to lose less body weight through peak lactation compared with those fed the conventional corn silage diet (−0.22 vs. −0.52kg/d). Although milk yield was not different between dietary treatments through peak lactation, milk yield post-peak lactation increased by feeding the BMR diet compared with the conventional corn silage diet (41.0 vs. 38.8kg/d). Yield of 3.5 percent fat-corrected milk was similar between dietary treatments throughout the experiment (41.4kg/d, on average), but milk fat concentration decreased by feeding the BMR diet compared with the conventional corn silage diet post-peak lactation (3.47 vs. 3.80 percent).
Overall milk protein concentration was similar between dietary treatments throughout the experiment (2.96 percent, on average), whereas milk protein yield tended to be higher for the BMR diet post-peak lactation compared with the conventional corn silage diet (1.19 vs.1.13kg/d). Feeding BMR silage with a high dietary concentration of alfalfa hay maintained more body weight, but did not affect milk production through peak lactation; however, cows fed the BMR diet post-peak lactation consumed more feed and maintained longer peak milk yield, leading to greater overall milk production and milk protein yield.
Source: M.S. Holt, J.-S. Eun, C.R. Thacker, A.J. Young, X. Dai, K.E. Nestor Jr./Journal of Dairy Science