The effect of acid buf and combinations of acid buf and socium bicarbonate in dairy cow diets on production response and rumen parameters

[摘要] ENGLISH ABSTRACT: The effect of Acid Buf and combinations of Acid Buf and Sodium bicarbonate in dairy cowdiets on production response and rumen parametersThe objective of this study was to determine the effect of Acid Buf alone, or in combination with sodiumbicarbonate, on milk production, milk composition and selected rumen parameters. A high concentrateTMR, formulated to be potentially acidotic, was used to construct four dietary treatments in which Acid Buf(AB), the skeletal remains of the seaweed Lithothamnium calcareum, was used alone or in combination withsodium bicarbonate (BC). The diets contained 3.5 g/kg of AB (Treatment 1) or 1.75 g/kg of AB and 1.75g/kg of BC (Treatment 2) or 3.5 g/kg of AB and 3.5 g/kg of BC (Treatment 3) or 3.5 g/kg of AB and 5.2 g/kgof BC (Treatment 4). The response to treatment was determined using eight ruminally cannulated lactatingHolstein cows randomly allocated to treatments according to a 4 x 4 (n=2) Latin square design, with fourtreatments and four periods. The total experimental period was 100 days in which every cow received eachdiet for a period of 18 days prior to a data collection period of 7 days. Rumen pH was monitoredcontinuously over 2 days using a portable data logging system and in-dwelling electrodes. Samples of rumenfluid were collected for volatile fatty acid (VFA) analyses. During each data collection period, milkproduction was recorded twice daily for 7 days, whereas milk was sampled twice daily for five consecutivedays for component analysis. Cows were fed ad libitum and dry matter intake was recorded individually.Treatment had no significant effect on milk production, milk composition or feed intake. Ruminal pHprofiles of all the treatments indicated that the diets were well buffered. Average pH over 24 hours was 6.0,6.1, 6.1 and 6.2 for Treatments 1, 2, 3 and 4, respectively. The pH did not go below 5.8 for any of thetreatments and increasing levels of sodium bicarbonate increased the diurnal profile such that at the highestlevel (Treatment 4), the pH profile ranged from 6.1 to 6.5. Although not significant, Treatment 1 (Acid Bufalone) numerically resulted in the highest milk output without compromising milk quality. It is proposedthat high rumen pH may impact negatively on milk output by increasing the acetate:propionate ratio to thedetriment of rumen efficiency. Treatment had no significant effect on total VFA concentration, but thereseemed to be a tendency for increased total VFA concentration as the level of sodium bicarbonate increased.The acetate:propionate ratio of Treatment 1 (2.91) was significantly lower than Treatment 4 (3.65) (P<0.05).The use of buffers which react to increasing acidity in the rumen may therefore provide an efficient, safesolution to rumen acidosis. This study confirmed previous results indicating that a daily intake of 80 g ofAcid Buf by cows receiving high concentrate diets would support high milk production withoutcompromising milk solids contents.

[发布机构] Stellenbosch University