Effect of different buffer and biological compounds on milk production and composition, ruminal fermentation parameters and blood metabolites of subclinical acidosis condition in lactating Holstein dairy cows

Background and Objectives :Modern dairy cow feeding strategies focus on meeting the energy requirements for high levels of milk production by encouraging maximum intake of energy-dense, low-fiber diets with highly fermentable carbohydrates. Despite this management system having an immediate positive effect on milk yield, but long-term there are potentially many negative effects on dairy cow health, welfare, and performance. At high levels concentrate, a reduction in ruminal pH might occur due to high levels of rapidly fermentable carbohydrates and depressed saliva production; this in turn depresses fiber digestion and leads to subacute ruminal acidosis and other acidosis-related metabolic disturbances. Thus, buffers inorganic and biologic are often used in high-energy rations to control the acidity of the rumen and to avoid reductions in dry matter intake (DMI) and milk fat depression.

Materials and Methods: In this study, 18 multiparous Holstein dairy cows were used in a completely randomized block design in 3 treatments with 6 replications. Experimental treatments included: 1) total mixed ration (TMR) + sodium bicarbonate, 2) TMR + combined buffer, 3) TMR + combined buffer containing live yeast. The experimental period lasted 28 days, 14 days were the adaptation period along with receiving the experimental diets with food supplements, 4 days were the subacute acidosis challenge induction phase, and 10 days were the recovery period. In different periods of the experiment, were measured dry matter intake, production and composition of milk, rumen parameters and blood metabolites.

Results: Experimental treatments had no significant effect on DMI during the adaptation and subacute acidosis period. Milk production and 3.5% fat corrected milk (FCM) yield were not affected by treatments at any of the feeding period. Milk fat in the adaptation period (P=0.08) and subacute acidosis period (P=0.09) was higher in the combined buffer containing live yeast compared to other treatments. In this study, it was shown that due to the challenge of ruminal acidosis, DMI, milk production and 3.5% FCM yield tended to decrease compared to the adaptation period(P<0.01). pH, ruminal NH3-N concentration, molar proportions of acetate and ratio of acetate to propionate were higher in the adaptation period compared to sub-acute acidosis(P<0.01), while the molar proportions propionate and lactate in the induction phase of acidosis was significantly increased compared to the adaptation period(P<0.01). Glucose, cholesterol, blood urea nitrogen (BUN) were affected by the experimental period, so that the level of cholesterol and BUN was higher in the adaptation period compared to the acidosis challenge(P<0.01), on the other hand, the glucose level increased significantly in the acidosis phase(P<0.01).

Conclusion: This experiment showed that subacute acidosis can have negative effects on the performance of dairy cows. The use of buffer compounds with live yeast during this period can have beneficial effects on the performance of dairy cows.