The aim of this study was to evaluate the effect of buffering agents on performance of lactating cows fed pineapple peel as main roughage. Four mid-lactation primiparous crossbred Holstein dairy cows averaging 443.5 ± 10.6 kg BW were assigned in a 4 x 4 Latin square design. Each cow was fed one of four experimental diets including: T1) control, pineapple peel (PP) to commercial pellet (CL) ratio of 70:30 without added buffer; T2) PP to CL ratio of 70:30 with 1.2 % sodium bicarbonate (NaHCO3 ); T3) PP to CL ratio of 52.5: 30 with mixture of 17.5 % rice bran and 1.2 % calcium carbonate (CaCO3 ); and T4) PP to CL ratio of 50:30 with 20 % rice straw (RS). The results revealed that feed intake, digestion coefficient, digestible nutrient intake were unaffected by supplementation of NaHCO3 , CaCO3 , and RS in diets (P > 0.05). The daily quantities of ME and NEL intake were not altered by treatments (P > 0.05), but PDIE and PDIN were increased by supplementing CaCO3 in the diet (P < 0.05). Weight gain was higher for cows supplemented with NaHCO3 and RS compared with other groups (P < 0.05). Cows receiving supplemental NaHCO3 , CaCO3 and RS had the same concentration of volatile fatty acids (P > 0.05). Acetate to propionate ratio ranged between 2.18 to 2.96 (P > 0.05) with the highest (2.96) in the RS supplement group. The NaHCO3 , CaCO3 , and RS supplement did not influence blood metabolites, blood electrolytes, milk yield and milk composition (P > 0.05). No sign of acidosis was observed. Therefore, it could be concluded that NaHCO3 , CaCO3 , or RS supplementation had no significant impact on performance of lactating cows fed PP as main roughage. Further research should be conducted to test the influence of such diets on milk production with larger number of animals in longer period of time.
