Dairy cows fed equivalent concentrations of forage neutral detergent fiber from corn silage, alfalfa hay, wheat straw, and corn stover had similar milk yield and total tract digestibility

The aim for this research was to determine if corn stover and wheat straw can be efficiently added to lactating dairy cow diets as physically effective neutral detergent fiber (peNDF) sources. A 5 × 5 Latin square design was used with 5 multiparous rumen cannulated Holstein cows. The treatments were: 1) corn silage as sole forage source [441 g/kg of total-mixed ration (TMR); CS], 2) corn silage and 115 g/kg alfalfa hay (455 g/kg of forage in TMR; ALF), 3) corn silage and 50 g/kg wheat straw (390 g/kg of forage in TMR; STW-5), 4) corn silage and 100 g/kg straw (462 g/kg of forage in TMR; STW-10), and 5) corn silage and 55 g/kg corn stover (395 g/kg of forage in TMR; STV). All diets were formulated to contain 180 g/kg forage aNDF except that the diet with 100 g/kg straw contained 230 g/kg forage aNDF. Dry matter intake (DMI) was highest for STW-5, except for it being similar with ALF. Body weight (734 kg) and body condition score (3.18) were similar among treatments. Milk (35.6 kg/d), milk fat (35.6 g/kg), milk protein (28.7 g/kg), and milk urea nitrogen (17.4 mg/dL) also were similar among treatments. The different forage sources resulted in similar total tract digestibilities of dry matter (0.757), organic matter (0.769), and aNDF (0.635). Rumen pH (6.12), acetate:propionate (3.10), and ruminal concentrations of total volatile fatty acids and proportions of acetate, propionate, butyrate, and valerate were similar among treatments. Proportion of isovalerate and isobutyrate were highest for STW-10 compared to the other diets, and isovalerate was lower for ALF than for STW-5 and STW-10. Feeding 5% wheat straw resulted in the highest DMI, but increasing wheat straw to 10% lowered DMI, possibly caused by rumen fill. Feeding similar forage aNDF concentrations with corn silage based diets using corn stover, alfalfa hay, and wheat straw can result in similar animal performance and ruminal fermentation with adequate formulation of dietary non-fiber carbohydrates and peNDF.