Eating and resting salivation in early lactation dairy cows.

Salivation rates were measured by cardial collection in four ruminally fistulated, early lactation cows. Complete diets of 70% concentrate: 30% hay crop silage (dry matter) or an isonitrogenous, isocaloric mixture of 60% concentrate: 40% corn silage were fed ad libitum once daily in a replicated 2 X 2 Latin square design. Thirty-day periods, beginning 2 d postpartum, consisted of 22 d adaptation and 8 d for determination of eating behavior, eating and resting salivation rates, and rumen liquid turnover rate. Diet did not affect eating behavior, salivation rates, saliva volumes produced while eating or resting, or saliva composition, but degree of feed ensalivation (fresh basis) and volume of saliva per bolus were higher for the hay crop silage diet due to its higher dry matter content. Resting salivation rate and volume produced while resting were greater at wk 8 than wk 4 of lactation even when corrected to constant dry matter intake, indicating that adaptation to diet postpartum involved increased basal resting salivation rate. Rumen pH was lower for the hay crop silage diet, but rumen fluid kinetic measurements did not differ with diet or week of lactation.