Ruminal fermentative parameters and blood acido-basic balance changes during the onset and recovery of induced latent acidosis in sheep

• Main Authors: Brossard, Ludovic, Martin, Cécile, Michalet-Doreau, Brigitte
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2003
• Subjects: acidosis;rumen fermentation; protozoa;blood;acid-base status;équilibre acido-basique;sheep;ruminant; ovin; ruminant; acidose; fermentation ruminale; régime alimentaire; nutrition; sang; Carbonic acid
• Online Access: http://prodinra.inra.fr/ft/2A0B8A1C-8C9A-4915-BB1B-406CE646CFBF; http://prodinra.inra.fr/record/73625; https://doi.org/10.1051/animres:2003036

Four ruminal cannulated Texel wethers were used to study the long-term effects of an acidotic diet on ruminal parameters and blood acid-base status. The short-term events around feeding and the recovery of the animals were followed after this nutritional disturbance. Sheep were limit-fed consecutively a control diet H (100% hay) (one week), an acidotic diet W (60% wheat + 40% hay) (2 weeks), and again the control diet (2 weeks). Mean, minimum and maximum ruminal pH were lower, and the time and area under pH 6.0 were higher (P < 0.001) with the W diet than with the H diet. These pH parameters indicate a latent acidosis defined here as a subacute and maintained acidosis. Before feeding, the drop in ruminal pH with the W diet was correlated with an increase in the VFA buffering capacity (BC) (R 2 = 0.70) and with a decrease in the BC of both carbonic acid functions (R 2 = 0.52 for H 2 CO 3 and 0.55 for HCO 3 –). After feeding, the acidotic diet effect on ruminal pH was not explained by variations in the BC of either of these chemical species. Ruminal lactate concentration was higher with the W diet compared to the H diet (P < 0.001) but remained low (< 2 mmol/L). Total VFA concentration (P < 0.001), acetate (P < 0.001) and propionate (P < 0.01) proportions in the rumen decreased with the W diet, while the butyrate proportion increased (P < 0.001). The number of Entodiniomorphs increased with the W diet (P < 0.001). Most parameters showed no significant variation between the 2 weeks with the W diet (P > 0.05). All ruminal parameters, except for ammonia, recovered to initial levels during the H diet redistribution (P < 0.05) while blood parameters decreased (pH, P < 0.05; bicarbonates (HCO 3 –), total CO 2 content (TCO 2), base excess in whole blood (Beb) and in extra cellular fluid (Beecf), P < 0.01). This decrease, initiated during the distribution of the acidotic diet, suggests a mobilization of body alkaline reserves and a longer recovery time in blood than in the rumen. We observed a non-lactic but butyric latent acidosis, linked to Entodiniomorph proliferation, suggesting an intermediate stage before the onset of acute lactic acidosis.