| A series of three experiments were conducted to: (i) evaluate the acidogenic value (AV) of feedstuffs and its relationship with rumen fluid pH changes; (ii) evaluate the effect of feed AV on ruminal pH, fibre degradability, dry matter intake (DMI), and milk production and composition; and (iii) evaluate the effects of feed AV and forage particle size (FPS) on ruminal pH, DMI and milk production and composition. The first experiment indicated that the highest value of AV was for non-fiber carbohydrate-rich feeds, forages were intermediate and high protein feeds were the lowest. The rumen fluid pH changes were correlated with AV (R 2 = 0.74). In the second experiment, isoenergetic and isonitrogenous concentrate diets with either a low AV (LAV) or high AV ( HAV) were formulated. High dietary AV depressed ruminal pH, and decreased in situ fiber digestibility. However, the ruminal pH depression did not affect DMI, fat content or 4% fat corrected milk (FCM). In experiment 3, low AV ( LA) or high AV (HA) concentrates were formulated and fed along with either course or finely chopped corn silage and alfalfa. High dietary AV depressed ruminal pH. Ruminal pH was not affected by FPS. However, longer FPS attenuated the pH depression more in the HA treatment than the LA treatment, as indicated by a decreased time spent at suboptimum ruminal pH (5.8). In conclusion, the AV of feeds can be used to formulate rations to mitigate subacute rumen acidosis in dairy cows. |
