Interactions of monensin with dietary fat and carbohydrate components on ruminal fermentation and production responses by dairy cows

Abstract

Variation in milk fat percentage resulting from monensin supplementation to lactating dairy cows could be due to altered ruminal fermentation with interactions of monensin with ruminal biohydrogenation of fat and ruminal carbohydrate availability. The objective of the study was to determine the effects of feeding monensin as Rumensin (R) in diets differing in starch availability (ground or steam-flaked corn), effective fiber (long or short alfalfa hay, LAH or SAH), and 4% fat (F) from distillers grains, roasted soybeans, and an animal-vegetable blend on ruminal fermentation characteristics and milk production in lactating dairy cows. Six ruminally cannulated lactating Holstein cows were used in a balanced 6×6 Latin square design with 21-d periods. The cows were fed 6 diets: (1) C=control diet with ground corn and LAH, (2) CR=C plus R, (3) CRFL=CR plus F, (4) CRFS=ground corn, R, F, and SAH, (5) SRFL=steam-flaked corn, R, F, and LAH, and (6) SRFS=steam-flaked corn, R, F, and SAH. Mean particle size of LAH was 5.00 mm and 1.36 mm for SAH. All diets were formulated to have 21% forage NDF and 40% NFC. The R tended to decrease DMI, decreased milk fat yield, and numerically lowered milk fat percentage (3.41 vs. 2.98%). Addition of F to R diets did not affect milk fat percentage. By feeding diets containing R and F, SAH tended to increase milk fat percentage for the ground-corn diet, but SAH tended to decrease milk fat percentage with steam-flaked corn (CRFL+SRFS vs. CRFS+SRFL). The steam-flaked corn increased total-tract NDF digestibility (CRFL + CRFS vs. SRFL+SRFS; 51.1 vs. 56%). Addition of F with R decreased total VFA concentration and increased rumen pH. Fat addition with R decreased rumen NH3N and MUN (12.8 vs. 13.9 mg/dL), and SFC decreased NH3N concentration compared with ground corn. Although R caused milk fat depression, addition of F did not further exacerbate milk fat depression. Fatty acid analysis did not implicate any particular biohydrogenation intermediate as the causative factor for the milk fat depression.

Diet supplementation with cinnamon oil, cinnamaldehyde, or monensin does not reduce enteric methane production of dairy cows

“…With the exception of isobutyrate and isovalerate molar proportions which were higher (P < 0.01) for cows fed MON compared with cows fed CTL, the molar proportions of the other VFA and the acetate : propionate were unaffected by dietary addition of MON. Previous (Benchaar et al, 2006) and recent (Mathew et al, 2011) studies also observed no change in the acetate : propionate ratio in dairy cows supplemented with MON. In contrast, Sauer et al (1998) reported that feeding MON decreased the acetate : propionate ratio in dairy cows.…”

“…In agreement with our findings, Grainger et al (2010) also reported no change in DMI of cows fed MON at a feeding rate similar to that used in our study. Likewise, Mathew et al (2011) observed no effect of MON on nutrient digestibility in dairy cows. In contrast, Benchaar et al (2006) reported increased CP digestibility in cows supplemented with MON.…”

“…Protozoa counts were unaffected by the addition of MON to the diet (Table 4). Recently, Mathew et al (2011) also reported no MON effect on total numbers and the generic distribution of protozoa in ruminal fluid. A study by Guan et al (2006) demonstrated the capacity of protozoa to adapt to ionophores, thus explaining the lack of MON effect on ruminal protozoa numbers observed in the current study.…”

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

“…Another study has reported that the supplementation of lactating Holstein cows with monensin decreased VFA (5). Furthermore, Mathew et al (23) have reported that the supplementation of cows with monensin and tallow together results in a decrease in total VFA. In contrast with the current study, Lewis et al (21) have reported that cows fed tallow did not have a significant change in total VFA production compared to controls, but they did have a significant increase in propionic acid content as well as decreases in acetic acid content and the acetate:propionate ratio.…”

Anti-methanogenic effects of monensin in dairy and beef cattle: A meta-analysis

“…The mechanism through which lipid could specifically enhance monensin is not clear. Clary et al (1993) and Mathew et al (2011), who tested effects of dietary lipid on monensin, did not find any significant change in acetic to propionic ratios or protozoan numbers in the rumen in response to addition of lipid over monensin. However, drawing a sensible conclusion about the interaction between dietary lipid and monensin is difficult because half of the dairy cow studies were based on fresh forages (Table 1) and about half of the forage EE comprises undegradable cuticular waxes.…”