Search

Abstract: This study determined impacts of a commercial blend of microencapsulated essential oils (EO), fed at increasing dose levels to high yielding primiparous dairy cows, on milk yield and composition. Eight pregnant Holstein heifers, selected to have their parturition within a period of 30d, were kept in tie stalls equipped for individual feeding, and with free access to water, from the 7th month of gestation. At an average of 40d postpartum, cows were assigned to one of four dietary EO levels in a replicated 4×4 Latin square design. The experimental diets (i.e., corn silage, fescue hay and a compound feed, 6.5, 4.4 and 8.7kg DM/d respectively) differed only in the addition level of a microencapsulated EO supplement (RumaXol Feed) mixed at different levels into the compound feed (fed at 1kg/cow day) in order to provide 0, 0.32, 0.64 and 0.96g/d of the EO mixture. The experiment had four experimental periods of 21d, with the last 5d used for collection of faeces and urine, for milk yield and composition recording and measurement of cow biometric data. The dietary EO supplementation had no effect on dry matter (DM) intake, water consumptions or faecal DM, while urine density was (P=0.01) lower at the intermediate EO dosages. Digestibility and biometric measures of cows were not modified by EO feeding. The protein content of milk tended (P=0.06) to be higher at the intermediate EO dosages, as did (P=0.05) the milk energy concentration. However milk and milk component yields were not affected by EO feeding level. [Copyright &y& Elsevier]

Abstract: This study was designed to evaluate effects of increasing doses of a blend of essential oils (EO; oregano, cinnamon, thyme, orange peel) on in vitro rumen fermentation in rumen liquor from dairy cows and fattening bulls, as influenced by acidity at the start of the fermentation. Two in vitro fermentation experiments, which differed only in the origin of rumen liquor (i.e., dairy cows [DC] or fattening bulls [FB]), were conducted in duplicate runs in 100ml glass tubes containing 50ml of diluted rumen fluid and 500mg of a mixed ration substrate. The pH of the diluted rumen liquor at the beginning of each fermentation was adjusted to 7.0 with 5N NaOH or 5.5 with 3N HCl. The EO blend was added to each fermentation tube at doses of 8, 16, 24 and 32μl/tube, equivalent to 160, 320, 480 and 640μl/l, using 3 tubes for each dosage level plus 3 tubes without EO as controls (i.e., 30 tubes in total/run). After 24h of incubation, fermentation liquor was collected and analyzed for volatile fatty acids (VFA), ammonia N and pH. In both experiments, pH and ammonia N concentration of the fermentation liquor were lower (P<0.01) at the initial pH of 5.5. The reduction of initial pH from 7.0 to 5.5 depressed VFA yield (138mM versus 120mM and 132mM versus 111mM, P<0.01, respectively, for DC and FB rumen liquors), and modified end products of fermentation by lowering the acetate:propionate ratio (4.3 versus 3.6 and 3.2 versus 2.5, P<0.01, respectively, for DC and FB rumen liquors). Butyrate concentration was higher at the lower pH in the DC rumen liquor fermentation (22.4mM/100mM versus 16.2mM/100mM, P<0.01), but not in the FB fermentation. In both experiments, addition of the EO blend did not depress total VFA concentrations, except at the highest dose in the experiment with rumen fluid from DC (122mM versus 128mM, P<0.01). In both experiments, there was an interaction (P<0.01) between EO addition and initial pH on acetate proportion; at the initial pH of 5.5, EO addition decreased acetate from 65.0 to 63.9 and from 62.6 to 61.8mM/100mM, respectively, for DC and FB rumen liquors, while there were no effects of EO at the initial pH of 7.0. In the experiment with DC rumen liquid, EO addition tended (P<0.08) to increase propionate proportion (from 16.1 to 16.6mM/100mM), while there was no effect in FB rumen liquid. In the FB experiment, EO decreased (P<0.05) the acetate:propionate ratio, while in the DC experiment it decreased only at low pH (interaction ‘EO addition×initial pH’: P<0.01). A moderate shift in end products of fermentation occurred with both types of rumen liquor, but mainly at low ruminal pH (i.e., 5.5), suggesting a selective toxicity of these EO against rumen bacterial strains that grow at low rumen pH. [Copyright &y& Elsevier]