Brown-Midrib Corn Silage for Lactating Dairy Cows

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Abstract
Brown midrib-3 mutant (low lignin) corn silage and its normal genetic counter-part were fed to more cows longer than in most trials. Lactating Holstein cows (20), (10 per ration group), were group fed corn silage (brown midrib-3 or normal) ad lib, 2.25 kg alfalfa hay/head and grain at 1 kg/3 kg milk produced daily through 12 wk. Cows averaged 6 wk postpartum at the start of the trial. Chemical composition was similar for the 2 silages. Silage and total intakes of dry matter were similar although intakes tended to be larger for cows fed the mutant corn silage. Milk production and its composition were similar (25.0 and 25.5 kg milk/day, 3.79 and 3.88% fat, 2.99 and 3.03% protein and 12.44 and 12.42% total solids for cows fed brown midrib-3 and normal silages). Cows fed the ration of mutant corn gained more weight than those fed the normal corn silage ration. Apparent digestibilities of nutrient constituents were 1-10 percentage units higher for the brown midrib-3 ration. Utilization of N from the 2 rations was similar. Concentrations of total volatile fatty acids and butyrate were greater in rumen contents of cows fed the normal ration. Rumen pH and ammonia were similar. Glucose and urea N concentrations in serum did not differ between treatments. The slightly greater consumption and digestibility of silage made from the brown midrib-3 mutant of corn were reflected in increased weight gains rather than in increased milk production.