Interaction of unsaturated fat or coconut oil with monensin in lactating dairy cows fed 12 times daily. I. Protozoal abundance, nutrient digestibility, and microbial protein flow to the omasum

Abstract

Monensin (tradename: Rumensin) should reduce the extent of amino acid deamination in the rumen, and supplemental fat should decrease protozoal abundance and intraruminal N recycling. Because animal-vegetable (AV) fat can be biohydrogenated in the rumen and decrease its effectiveness as an anti-protozoal agent, we included diets supplemented with coconut oil (CNO) to inhibit protozoa. In a 6 × 6 Latin square design with a 2 × 3 factorial arrangement of treatments, 6 rumen-cannulated cows were fed diets without or with Rumensin (12 g/909 kg) and either no fat (control), 5% AV fat, or 5% CNO. The log10 concentrations (cells/mL) of total protozoa were not different between control (5.97) and AV fat (5.95) but were decreased by CNO (4.79; main effect of fat source). Entodinium and Dasytricha decreased as a proportion of total cells from feeding CNO, whereas Epidinium was unchanged in total abundance and thus increased proportionately. Total volatile fatty acid concentration was not affected by diet, but the acetate:propionate ratio decreased for CNO (1.85) versus control (2.95) or AV fat (2.58). Feeding CNO (23.8%) decreased ruminal neutral detergent fiber digestibility compared with control (31.1%) and AV fat (30.5%). The total-tract digestibility of NDF was lower for CNO (45.8%) versus control (57.0%) and AV fat (54.6%), with no difference in apparent organic matter digestibility (averaging 69.8%). The omasal flows of microbial N and non-ammonia N were lower for CNO versus control and AV fat, but efficiency of microbial protein synthesis was not affected. The dry matter intake was 4.5 kg/d lower with CNO, which decreased milk production by 3.1 kg/d. Main effect means of dry matter intake and milk yield tended to decrease by 0.7 and 1.2 kg/d, respectively, when Rumensin was added. Both percentage and production of milk fat decreased for CNO (main effect of fat source). An interaction was observed such that AV decreased milk fat yield more when combined with Rumensin. Using large amounts of supplemental fat, especially CNO, to decrease abundance of protozoa requires further research to characterize benefits versus risks, especiallywhen combined with Rumensin.

Effect of supplementing coconut or krabok oil, rich in medium-chain fatty acids on ruminal fermentation, protozoa and archaeal population of bulls

“…Another study from the same group reported a 0.59 log unit decrease in protozoal numbers when sheep were fed CO at a concentration of 56 g/kg DM, which is 1.5 times more than the amount used in our study. A similar supplementation rate (50 g/kg DM) to dairy cows, provoked a decrease of 1.05 log units in total protozoa, with a shift in the protozoal community towards Epidinium and Isotricha, whereas Entodinium and Dasytricha seemed more sensitive to CO (Reveneau et al, 2012).…”

Interaction of unsaturated fat or coconut oil with monensin in lactating dairy cows fed 12 times daily. II. Fatty acid flow to the omasum and milk fatty acid profile

“…Omasal flow of FA, milk FA profile, and FA digestibility data were analyzed as a 6 × 6 Latin square using PROC MIXED of SAS (v9.1; SAS Institute Inc., Cary, NC) as described in the companion article (Reveneau et al, 2012). Treatment means were compared using 5 preplanned orthogonal contrasts, with 6 coefficients shown in brackets respectively for control, AV fat, CNO, control + R, AV fat + R, and CNO + R: 1) the main effect of R [1 1 1 −1 −1 −1], 2) the main effect of control versus fat (i.e., the average of AV fat and CNO) [−2 1 1 −2 1 1], 3) the main effect of the fat source (i.e., AV fat vs. CNO) [0 −1 1 0 −1 1], 4) the interaction between R and fat [−2 1 1 2 −1 −1], and 5) the interaction between R and the fat source [0 −1 1 0 1 −1].…”

“…Animals, treatments, and the experimental design were described in the companion article (Reveneau et al, 2012). Feed, omasal, and fecal samples were collected and analyzed as described previously, except for FA analysis, which was conducted with one of the procedures reviewed by Palmquist and Jenkins (2003) as modified by Mathew et al (2011).…”

“…Milk was sampled from 4 consecutive milkings during d 17 to 19 and composited per period, with one aliquot being preserved and used for milk composition (Reveneau et al, 2012) and the other aliquot frozen and stored at −20°C for FA analysis. Whole omasal samples and the frozen aliquot of milk were analyzed for FA profile by GLC.…”

Relationships between ruminal Gram-positive bacteria and methane from lactating dairy cows supplemented with monensin and tallow, alone or in combination

“…In addition, a significant shift in fermentation from acetate, butyrate, and isovalerate toward propionate and valerate has been reported with the addition of fat (37). Because propionate is an important hydrogen sink, propionate is expected to result in decreased methane production per unit of fermentable matter (33).…”