Whey Components in Restricted-Roughage Rations, Milk Composition, and Rumen Volatile Fatty Acids

Abstract

After a 3-wk standardization ration of alfalfa hay and corn silage ad libitum and concentrate at 1 kg/3kg milk, 30 lactating Holstein cows were fed 2.3kg hay/day and one of five concentrate rations ad libitum for a 6-wk experimental period. Concentrate rations were: (1) control, (2) dried whole whey, (3) high mineral whey product, (4) demineralized whey, and (5) lactose. Ration 3 contained the same amount of minerals from whey as ration 2 while rations 4 and 5 contained the same amounts of lactose as ration 2.Changes in milk fat compared to the standardization period for the rations in sequence were (percentage units): −1.26, −.58, −.47, −1.32, and −.64. This indicated whey minerals were most effective in preventing milk fat depression on high-concentrate rations although lactose also was partially effective. High-concentrate (experimental) rations increased milk protein .2 percentage units as compared to the standardization period. Milk yields and concentrate intake were not altered by treatment. Ruminal propionate concentrations (μM/ml) on control and demineralized whey rations increased over standardization values. Butyrate concentrations were elevated most by the rations containing the highest lactose (i.e., rations 2, 4, and 5) while acetate was not affected by any treatments.