Controlled Ruminal Infusion of Sodium Bicarbonate. 1. Influence of Postfeeding Infusion Interval on Ruminal Milieu

Abstract

Four ruminally cannulated, lactating Holstein cows were assigned to a 4 x 4 Latin square to monitor the effects of intraruminal NaHCO3 infusion on changes in the rumen environment. Sodium bicarbonate (110 g), dissolved in 3.8 L of water, was infused twice daily at a constant rate for 2 h starting at 0, 2, or 4 h postfeeding. All cows had access to their diet containing sorghum silage and concentrate in a 35:65 ration (DM basis) for 45 min twice daily. Ruminal fluid was collected at feeding and every 30 min postfeeding for 12 h on the last day of each 7-d period. Dry matter intake was lower for buffer infusion at 2 to 4 h than for water-infused control but was not affected by the other NaHCO3 infusions. Although total milk yield was not affected, milk fat percentage and fat yield tended to be lower for the NaHCO3 treatments. Compared with the water infusion, the NaHCO3 infusion from 2 to 4 h postfeeding most effectively prevented the postfeeding increase in ruminal free proton concentration. Additionally, volume of ruminal liquid was increased for the NaHCO3 infusions from 0 to 2 h and 4 to 6 h; ruminal liquid turnover time was increased for the NaHCO3 infusion at 4 to 6 h, but ruminal kinetics otherwise were not affected by NaHCO3. Although infusion of NaHCO3 from 2 to 4 h prevented severe alterations in ruminal acid-base status, it did not increase total VFA concentration or the acetate:propionate ratio. Although total VFA concentrations were not affected by NaHCO3 infusion, acetate:propionate ratio was higher for the NaHCO3 infusion from 0 to 2 h than for the control. Based upon alterations in ruminal acid-base status, exogenous buffer ideally should be provided to the rumen from 2 to 4 h postfeeding; however, our results indicate that the effectiveness of this regimen might be improved if buffer is combined with a rapidly released or unprotected dietary buffer.

Controlled Ruminal Infusion of Sodium Bicarbonate. 2. Effects of Dietary and Infused Buffer on Ruminal Milieu

“…The 4-6Bic infusion resulted in a higher [H+] than for Ctrl at 0 and 2 h, but ~educed [H+] after NaHco 3 infusion began (5.5 h) and again at 7.5 h postfeeding. Hogue et al (1991) also reported that the effects of intra-ruminal infusion of NaHco 3 on [H+] were most dramatic during the infusion interval. As compared to Ctrl, mean rumina!…”

“…An increase in ruminal turnover time was observed for 0 to 2 and 4 to 6 h postfeeding intraruminal infusion of sodium bicarbonate (Hogue et al, 1991). The acid-base status of an animal is associated with environmental temperature;…”

“…environment should include the provision of buffering capacity several hours postfeeding. Hogue et al (1991) observed that intraruminal infusion of NaHco 3 increased rumina! pH and buffering capacity; however, they also reported that these effects were transient, diminishing soon after cessation of infusion.…”

“…Several scientists have observed increases in DM intake with the addition of sodium bicarbonate when high concentrate diets were fed (Kilmer et al, 1980;Erdman et al, 1980;Schneider et al, 1986). In some studies, no increase in DM intake was reported with dietary addition of sodium bicarbonate (Hogue et al, 1991;Denker et al, 1980).…”

“…Others (Erdman et al, 1982; concluded that up to 2% exogenous NaHC0 3 in DM intake does not increase liquid dilution rate or rumen fluid volume in early lactating cows. Hogue et al (1991), using sorghum silage and concentrate (35:65 ratio; DM basis), observed the effects of intraruminal infusion of 110g NaHC0 3 dissolved in 3.8 L of water in lactating cows; they demonstrated an increase in ruminal liquid volume for o to 2 and 4 to 6 h NaHco 3 infusion and an increase in rumina! liquid turnover time for 4 to 6 h NaHco 3 infusion.…”