Pinchasov, Y., Division of Dairy Science, Agricultural Research Organization, Volcani Center, P. O. B. 6, Bet-Dagan, Israel
Hasdai, A., Division of Dairy Science, Agricultural Research Organization, Volcani Center, P. O. B. 6, Bet-Dagan, Israel
Gordin, S., Division of Dairy Science, Agricultural Research Organization, Volcani Center, P. O. B. 6, Bet-Dagan, Israel
Katznelson, D., Division of Dairy Science, Agricultural Research Organization, Volcani Center, P. O. B. 6, Bet-Dagan, Israel
Volcani, R., Division of Dairy Science, Agricultural Research Organization, Volcani Center, P. O. B. 6, Bet-Dagan, Israel

The nutritive value of liquid acid whey and that whey's effect on milk yield and composition, rumen, and blood metabolites were studied with 36 high-yielding cows from 1 to 147 days postpartum. Average dry matter of whey was 4.5% and pH 4.0. Intake rose from 35 to 55 liters/cow per day during the experiment. Cows balanced the reduction in concentrate intake by increasing intake of whey dry matter. There was a tendency by the whey group toward a lower milk yield during most of the lactation but a higher production of 3.5% fat corrected milk during lactation. Between 15 and 69 days postpartum the 3.5% milk yield was significantly higher for the whey-fed group. The whey-fed group had higher milk total solids, fat yield, and percentage. Protein was not different. Rumen metabolites were affected by cows drinking whey; pH and acetic and propionic acids were lower, but butyric, valeric, and lactic acids and ammonia-nitrogen were higher. Whey fed to mature dairy cows enters the rumen and not the abomasum directly. There were no differences in body weight fluctuations, conception, pregnancy, mastitis, or digestive disturbances between groups. Under conditions in Israel, feeding of liquid whey is most economical. © 1982, American Dairy Science Association. All rights reserved.