Daily rumen pH pattern of loose-housed dairy cattle as affected by feeding pattern and live yeast supplementation

The aim of this study was to continuously monitor rumen pH of loose-housed dairy cattle as affected by feeding pattern and live yeast supplementation. Three multiparous lactating rumen-cannulated cows receiving the same basal ration once daily were supplemented with 5 g/d (equivalent to 10(10) CFU/d) of Saccharomyces cerevisiae strain CNCM I-1077 (Levucell SC2, Lallemand, Toulouse, France) alternately for periods of 2 weeks following a cross-over design. The three cows were maintained in loose-house conditions and milked with a robotic milking system. Cows consumed a fraction of their ration in the feed bunk as a mixed ration and about 3 kg/d of concentrate during milking at the robotic milking unit. During the last 8 d of each period, rumen pH was monitored every 15 min. However, the rumen was accessed only once every 3 days, These pH measurements were recorded with a pH meter capable of storing pH values automatically that was placed inside a custom-made polyvinyl cylinder with about 300 g of lead to ensure that the device remained in the ventral part of the rumen throughout all readings. Individual feed intake and feeding patterns were also recorded. The data were analyzed using a mixed-effects model with repeated measures. Average rumen pH was greater (P < 0.01) when yeast was supplemented than when no yeast was provided. Ruminal pH decreased (P < 0.001) as time since last basal ration bout increased, and this decrease was more (P < 0.05) pronounced when no yeast was supplemented. Yeast-supplemented cows had a greater (P < 0.05) meal frequency than the unsupplemented cows. The results indicate that live yeasts have a beneficial effect on ruminal pH of cows kept in loose-house conditions. Furthermore, yeast effects on rumen pH may be evident starting 1 week after supplementation. (c) 2006 Elsevier B.V. All rights reserved.