Effects of Body Condition and Protein on Milk Fat Depression in Early Lactation Dairy Cows

Twenty muhiparous and 16 primiparous Holstein cows were fed either a high energy or low energy diet during the dry period to achieve different degrees of body condition.Three weeks postpartum, cows were randomly assigned to either a high protein (23% CP) or a low protein (14.5% CP) diet.The diet contained 21% ADF during wk 3 through 6 postpartum and lowered to 9% ADF during wk 7 through 14 postpartum to depress fat test.Cows fed the low energy prepartum diet had less fat depression when fed the high protein postpartum diet compared with the low protein diet.Milk fat depression was more severe for all cows fed the high energy prepartum diet.Depression in milk fat percentage for multiparous cows was 30.8, 10.2, 34.5, and 26.0% for high energy-high protein, low energy-high protein, high energylow protein, and low energy-low protein groups, respectively.For primiparous cows, milk fat depression was 37.3,24.1,37.0, and 34.6%.After the fiber change, depression in acetate to propionate ratio was less for muhiparous cows fed high protein than for those fed low protein.Prepartum energy did not influence acetate to propionate ratio depression that resulted from the fiber change.