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Combined Effects of Type of Forage Fed, of Concentrate Ingredients, and of Pelleting Concentrates on Rumen Fermentations, Milk Yield, and Milk Composition of Dairy Cattle

Department of Dairy Science, Auburn University Agricultural Experiment Station, Auburn, Alabama

ABSTRACT

A study was made to determine if differences in responses of dairy cattle to oat vs. corn silage, corn grain + cottonseed meal vs. corn distillers dried grains with solubles (CDDGS), and pelleted vs. nonpelleted concentrates were accumulative. Responses measured were a) concentrations and molar percentages of VFA in rumen fluid, b) milk yield, c) milk energy yield, d) milk-fat per cent, e) milk protein per cent, f) energy per kilogram of milk, and g) milk energy produced daily as a percentage of gross energy in concentrates eaten. Oat pasture increased concentration and molar per cent of propionic acid and concentration of total VFA over corn silage; whereas, CDDGS depressed the concentration and molar per cent of acetic acid and the concentration of total VFA, as compared with the corn concentrates. Pelleting the corn concentrate increased the molar per cent of propionic acid and decreased that of acetic acid, with differences being significant only within the oat pasture forage; whereas, pelleting of the CDDGS concentrate had no effect on these responses. Within the corn concentrates, pelleting decreased energy per kilogram of milk and milk fat per cent and increased milk yield, with responses being magnified on oat pasture as compared with corn silage. The data suggest that the effects of grazing oat pasture and of feeding pelleted corn on the molar percentages of acetic and propionic acids and on milk fat per cent, energy per kilogram of milk, and total milk yield were essentially additive.

In relation to the concentrate energy consumed, cows fed CDDGS concentrates produced more milk energy than those fed the corn concentrates.