Milk composition as affected by intra‐ruminal infusion of volatile fatty acids to cows on a restricted ration

Dilute solutions of acetic, propionic, and butyric acids were infused into the rumens of six lactating cows receiving a restricted hay and concentrate ration. Milk yield and composition. characteristics of the butterfat, and concentration of individual volatile fatty acids in the rumen liquor were determined. All three acids raised milk yield (P < 0.05). Increased yields of butterfat (P < 0.10) and solids‐not‐fat (P < 0.05) were obtained with acetic acid, but the percentage composition was not changed significantly. Propionic acid lowered the daily butterfat yield (P < 0.10) and butterfat percentage (P < 0.05). but increased the protein yield (P < 0.05) and percentage (P < 0.01), and hence increased the level of solids‐not‐fat in the milk. Butyric acid increased (P < 0.05) the yield and the percentage of butterfat (P < 0.05) and decreased (P < 0.05) the solids‐not‐fat percentage in the milk. The three acids lowered the iodine values of the butterfat. Butyric acid increased the Reichert value of the butterfat, whereas acetic and propionic acids led to slightly lower values.