Effect of dietary potassium percent for lactating dairy cows.

Three groups of Holstein cows (four cows per group) past the peak of lactation were fed dietary potassium as percent of dry matter as follows: .45% for 20 days to all groups; .45, .55, and .66% to the respective groups for 12 wk; and .66% to all groups for 19 days. Dietary potassium had no significant effect on milk fat and solids-not-fat contents of milk, milk production, or milk and blood serum cations (potassium, sodium, magnesium, calcium). However, body weights were affected. Symptoms common in potassium deficiency were not apparent. Average daily milk production, feed intake, and body weight gains for the 12 wk in kilograms were: 21.9, 15.8, and 15.7; 23.4, 16.4, and 54.5; and 22.8, 19.9, and 92.9 for the .45, .55, and .66% rations. When .66% potassium was fed to groups previously fed .45 and .55% potassium, feed intake increased by 3.6 kg and 1.3 kg but increased only .2 kg in the group previously fed .66%.