The effect of buffering dairy cow diets with limestone, Acid Buf or sodium bicarbonate on production response and rumen metabolism

[摘要] ENGLISH ABSTRACT: The objective of this study was to evaluate the effect of different buffers in dairy cow diets onmilk production and composition and on sefocted rumen metabolism parameters. A highconcentrate TMR, formulated to be potentially acidotic, was used to construct three dietarytreatments in which Acid Buf (the skeleton remains of the sea weed Lithothamniumcalcareum) was compared against limestone (control) and sodium bicarbonate plus limestone.One basal diet was formulated and treatment diets contained either 4 g/kg DM of Acid Buf,3.7g/kg DM of limestone+ 8 g /kg of sodium bicarbonate or 3.5 g/kg DM limestone (control),respectively. The response to treatment- was measured using 6 ruminally cannulated lactatingHolstein cows allocated to treatments according' to a 3 x 3 (n=2) balanced Latin square design,with three treatments and three periods. The total experiment period was 66 days in which·every cow received each diet for a period of 15 days prior to the data collection period of 7days. Rumen fluid was collected for volatile fatty acid (VF A), lactic acid and ammoniaconcentration. Rumen pH was monitored continuously every 10 minutes for two days using aportable data logging system and in-dwelling electrodes. During each data collection period,milk was collected and analyzed for its solid and mineral contents. Feed consumption wasrecorded individually. The impact of acidity was clearly visible, especially from the periodfrom mid:..day to mid-night when rumen pH dropped below 5.5 for a longer period (13 h) inthe control (limestone) treatment than in the sodium bicarbonate (7.7 h) and· Acid Buf (4 h)treatments. The minimum rumen pH was lower for the control (5.14) than for the Acid Buftreatment (5.42), while the pH in the sodium bicarbonate treatment (5.37) did not differ fromother treatments. The dietary buffers did not have a significant irppact on rumen VF A,lacticacid and ammonia concentrations. Daily milk yield was higher for the Acid Buf (31.8kg) treatment than for the sodium bicarbonate (29.l kg) and control (27.6 kg), treatments.Milk fat content was higher for the Acid Buf ( 42.1 g/kg) and sodium bicarbonate ( 41.8 g/kg)treatments and control (38.6 g/kg) treatments. Treatment had no effect on milk crude proteincontent (34.7 g/kg, 33.8 g/kg and 34.3 g/kg for the Acid Buf, sodium bicarbonate and controltreatments, respectively). The trial indicated that supplementing high concentrate diets forlactating dairy cows with Acid Buf at a level of 90 g/cow per day has a greater impact onrumen pH, milk production and milk composition than 180 g/cow per day of sodiumbicarbonate and that sub-clinical acidosis could reduce daily milk input by 4 kg/cow.Key words: Acid Buf, Buffer, Rumen metabolism, Milk production

[发布机构] Stellenbosch University