Effect of In Vitro Docosahexaenoic Acid Supplementation to Marine Algae-Adapted and Unadapted Rumen Inoculum on the Biohydrogenation of Unsaturated Fatty Acids in Freeze-Dried Grass

Abstract

The objective of this study was to examine the ruminal biohydrogenation of linoleic (18:2n-6) and linolenic (18:3n-3) acid during in vitro incubations with rumen inoculum from dairy cattle adapted or not to marine algae and with or without additional in vitro docosahexaenoic acid (DHA, 22:6n-3) supplementation. Treatments were incubated in 100-mL flasks containing 400 mg of freeze-dried grass, 5 mL of strained ruminal fluid, and 20 mL of phosphate buffer. Ruminal fluid was collected just before the morning feeding from 3 cows receiving a control diet (49% ryegrass silage, 39% corn silage, 1% straw, and 11% concentrate, fresh-weight basis) supplemented with marine algae for 21 d (adapted rumen fluid, aRF) or from the same cows receiving the control diet only for 14 d after marine algae supplementation was stopped (unadapted rumen fluid, uRF). In half of the incubation flasks, pure DHA (5 mg) was added as an oil-ethanol solution (100 mL). Incubations were carried out during 0, 0.5, 1, 2, 4, 6, and 24 h. After 24 h, in vitro addition of DHA resulted in greater amounts (mg/incubation) of 18:3n-3 (0.23, 0.43, 0.26, and 0.34 for aRF, aRF+DHA, uRF, and uRF+DHA), 18:2n-6 (0.14, 0.22, 0.15, and 0.20 for aRF, aRF+DHA, uRF, and uRF+DHA) and trans-11, cis-15-18:2 (0.27, 2.40, 0.06, and 2.21 for aRF, aRF+DHA, uRF, and uRF+DHA), whereas no effect of inoculum source was observed. Trans-11-18:1 accumulated after 24 h when aRF was incubated irrespective of in vitro DHA supplementation, whereas in incubations with uRF, accumulation of trans-11-18:1 only occurred when DHA was added (6.40, 4.35, 1.06, and 3.91 for aRF, aRF+DHA, uRF, and uRF+DHA). The increased amounts of trans-11-18:1 were due to the strong inhibition of the reduction to 18:0 because no 18:0 was formed when trans-11-18:1 accumulated after 24 h. The results of the current experiment shows hydrogenation of trans-11, cis-15-18:2 occurred in the absence of in vitro DHA only, whereas substantial hydrogenation of trans-11-18:1 to 18:0 only took place in incubations without DHA and with unadapted rumen inoculum, confirming the higher sensitivity of the latter process to DHA.

Lipid metabolism in the rumen: New insights on lipolysis and biohydrogenation with an emphasis on the role of endogenous plant factors

“…Shingfield et al (2008) showed that milk from cows fed diets supplemented with sunflower oils, with a high level of LA, linearly increased OBCFA levels (iso C15:0, C15:0 and anteiso C17:0) compared with milk from the unsupplemented group. The same results occurred in vitro, where bacterial synthesis of OBCFA increased with DHA supplement feeding level (Vlaeminck et al, 2008).…”

The effect of lipid supplements on ruminal bacteria in continuous culture fermenters varies with the fatty acid composition

“…The increase in propionate and the decrease in butyrate concentrations with the FO diet were also reported in other studies Lee et al, 2008;Vlaeminck et al, 2008) with the use of FO or algae. These changes may be linked to the alterations in the bacterial community seen in this study with the FO diet (discussed below).…”

Detailed Dimethylacetal and Fatty Acid Composition of Rumen Content from Lambs Fed Lucerne or Concentrate Supplemented with Soybean Oil

“…However, this later octadecatrienoic isomer was not detected in our samples. The 18∶2 trans -11, trans -15 have been previously reported in milk [50], omasal digesta [45], rumen fluid [51], lamb meat [52] and beef [53], and it is also associated with dietary intakes of 18∶3n−3. The occurrence of the 18∶2 cis -9, cis -15 and cis -12, cis -15 in lamb meat was already described by our group [46], furthermore these BI were proposed to be products of the ruminal biohydrogenation of the 18∶3n−3, resulting from the reduction of the cis -12 or cis -9 double bonds, respectively.…”