The effect of supplementing red deer (Cervus elaphus) with different forms of ascorbic acid upon the concentration of ascorbic acid in rumen fluid and blood plasma

Abstract

Two indoor experiments were conducted at the Massey University Deer Research Unit to study whether the blood plasma ascorbic acid (AA) concentration in farmed red deer (Cervus elaphus) could be raised, using a single large intraruminal administration of AA (2.7 g kg−1 live weight) prior to a simulated slaughter situation. Deer fistulated in the rumen were individually fed chaffed lucerne hay ad libitum at 30 min intervals; feed was then withdrawn 8 h before AA was administered, and fasting continued during the period of rumen fluid and blood sampling (30 h of fasting in total). Blood (jugular vein) and rumen fluid samples were taken 15 min before and at various intervals after dosing with AA. Rumen fluid pH values were also recorded. In Experiment 1 the effects of administration of pure ascorbic acid (AA), ethyl cellulose-coated ascorbic acid (EC) and silicone-coated ascorbic acid (SC) were compared. All three types increased rumen fluid and blood plasma AA concentrations to a desirable level (500 µg ml−1 blood plasma or greater), with the maximum concentrations in both sites occurring 1 h after administration. The area under the concentration versus time curve (AUC), the area under the curve corrected for baseline concentration (AUCB) and the maximum concentration (MAX) of AA in both rumen fluid and blood plasma were not significantly different among the three formulations of AA, indicating that all three were degraded at similar rates in the rumen and that their bioavailabilities were similar. Rumen pH decreased from approximately 7.0 to 5.0 within 1 h of administering each compound, increased to 6.0 after 4 h and then progressively increased to approximately 7.0 after 22 h. Experiment 2 was conducted to investigate the rumen-buffering effect after dosing with AA with and without added sodium bicarbonate. Including NaHCO3 increased rumen pH by approximately 1 unit during the first hour after dosing and by 0.7–0.4 units thereafter. AUC and AUCB for rumen fluid were significantly lower for the AA + NaHCO3 group of deer than for the AA group (p < 0.05), indicating that increasing rumen pH increased the rate of ruminal destruction of AA. AUC, AUCB and MAX of AA in blood plasma were not statistically different between the two treatments (p > 0.05). It was concluded that the single large intraruminal AA dose technique could be used to consistently increase AUC, AUCB and MAX of AA in both rumen fluid and blood plasma. Methods for improving the efficiency of the technique are discussed. © 2002 Society of Chemical Industry