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Abstract: 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 5g/d (equivalent to 1010 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 3kg/d of concentrate during milking at the robotic milking unit. During the last 8d of each period, rumen pH was monitored every 15min. 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 300g 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. [Copyright &y& Elsevier]

Abstract: Effects of a docosahexaenoic acid (DHA)-edible algae product, Aquagrow-DHA, on lipolysis and biohydrogenation of linoleic acid (C18:2 n-6) was studied in 24h in vitro incubations with buffer (20ml), sheep rumen contents (5ml), hay (0.4g) and sunflower oil (20mg). Four Aquagrow-DHA levels (0, 20.8, 41.6, 83.3mg) were tested and addition of lard ensured that the total fat content was constant. Increasing Aquagrow-DHA proportionally inhibited hydrogenation of C18:2 n-6, provoking an accumulation of C18:1 trans fatty acids (mainly C18:1 t10+t11). Analogous incubations for 6 and 24h with linseed oil (20mg) instead of sunflower oil, resulted in the accumulation of C18:2 t11c15 and, to a lower extent, C18:1 t10+t11 and showed that Aquagrow-DHA reduced the rate of lipolysis of linolenic acid (C18:3 n-3). Comparison of these results with incubations with the individual constituents of Aquagrow-DHA and whole algae biomass revealed that the observed effects were related to the presence of DHA. Finally, incubations under a 50:50 H2:CO2 atmosphere suggested a direct inhibitory effect of unesterified DHA on hydrogenating bacteria involved in the conversion of C18:2 t11c15 and C18:1 trans isomers, rather than on H2 availability. [Copyright &y& Elsevier]

Abstract: In 24h in vitro incubations with 25ml of buffered rumen fluid, four doses (0, 20.8, 41.6 and 83.3mg) of a DHA-edible algae product, Aquagrow-DHA, were examined in combination with sunflower (20mg) or linseed oil (20mg). One treatment contained no Aquagrow-DHA, linseed or sunflower oil and one was supplemented with Aquagrow-DHA (166.6mg) only. Addition of lard ensured that total fat content was constant among incubations. Increasing amounts of Aquagrow-DHA progressively inhibited CH4 to a maximum of 80% (P<0.001). Increased CH4 inhibition was accompanied by decreased acetate (P<0.001) and butyrate (P<0.001), and increased propionate (P<0.001) proportions, but also by depression of the short chain fatty acid (SCFA) production by 30% at the highest Aquagrow-DHA level (P<0.001). However, SCFA inhibition only occurred when the Aquagrow-DHA dose exceeded 41.6mg and CH4 production was reduced by about 30% (P<0.05) at this dose. Inhibitory effects were linked to the amount of unesterified polyunsaturated fatty acids, particularly docosahexaenoic acid. Incubations under partial H2 atmosphere suggested that a direct toxic effect to rumen methanogens was caused by higher amounts of unesterified DHA (>41.6mgAquagrow-DHA/incubation) only, whereas suppression of rumen methanogenesis at lower doses seemed to be indirect through a lack of substrate. This indicates bacteria providing H2 to the rumen methanogens to be more sensitive to unesterified DHA than rumen methanogens. [Copyright &y& Elsevier]