Browsing by Author "Mubiayi Beya, Michel"

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    The effect of buffering dairy cow diets with limestone, Acid Buf or sodium bicarbonate on production response and rumen metabolism
    (Stellenbosch : Stellenbosch University, 2007-12) Mubiayi Beya, Michel; Cruywagen, C. W.; Stellenbosch University. Faculty of Agriscience. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: The objective of this study was to evaluate the effect of different buffers in dairy cow diets on milk production and composition and on sefocted rumen metabolism parameters. A high concentrate TMR, formulated to be potentially acidotic, was used to construct three dietary treatments in which Acid Buf (the skeleton remains of the sea weed Lithothamnium calcareum) 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 lactating Holstein 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 7 days. Rumen fluid was collected for volatile fatty acid (VF A), lactic acid and ammonia concentration. Rumen pH was monitored continuously every 10 minutes for two days using a portable 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 was recorded individually. The impact of acidity was clearly visible, especially from the period from mid:..day to mid-night when rumen pH dropped below 5.5 for a longer period (13 h) in the 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 Buf treatment (5.42), while the pH in the sodium bicarbonate treatment (5.37) did not differ from other 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 protein content (34.7 g/kg, 33.8 g/kg and 34.3 g/kg for the Acid Buf, sodium bicarbonate and control treatments, respectively). The trial indicated that supplementing high concentrate diets for lactating dairy cows with Acid Buf at a level of 90 g/cow per day has a greater impact on rumen pH, milk production and milk composition than 180 g/cow per day of sodium bicarbonate and that sub-clinical acidosis could reduce daily milk input by 4 kg/cow. Key words: Acid Buf, Buffer, Rumen metabolism, Milk production