Rumen pH as a Factor for Controlling Feed Intake in Ruminants

Four rumen fistulated steers, in a -t 4 Latin-square design, received intrarmninal infusions of a) water, b) phosphoric acid, e) lactic acid, or d) citric acid, to study the effect of rumen pH on daily ha?" consumption. Steers were fed chopped hay ad libitum for a 6-hr period daily. To lower and maintain the rumen pH at about 6.0, the dilute acid solutions were infused on the day of the experiment with a prime dose 30 rain before feeding, followed by successive infusions during feeding. Daily air-dI3" hay intake dropped (P < 0.01) from 12.3 kg in the control animals (water infused) to 6.0, 6.3, and 8.0 kg in the animals receiving phosphoric acid, lactic acid, and citric acid solutions, respectively. In control animals, hourly tureen pH fell gradually through the hours of feeding from 7.03 before infusion to 6.58, 6 hr later. In acid-infused animals, rmncn pit dropped from 7.08 to about 6.0, where it was maintained during the feedh~g period. Blood urea values showed a nonsignificant drop in the acid-infused groups. Blood glucose levels remained constant. Blood ammonia made slight shifts dm'ing acid infusion. Blood volatile fatty acids were lower in the acid-infused group.