Effect of monensin inclusion on intake, digestion, and ruminal fermentation parameters by Bos taurus indicus and Bos taurus taurus steers consuming bermudagrass hay

Abstract

Effects of monensin inclusion and cattle subspecies on utilization of bermudagrass hay (13.7% CP, 77.3% NDF, and 38.8% ADF) were evaluated using ruminally cannulated steers (5 [BI] and 5 [BT]; 398 kg BW). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments were 0 (CON) or 200 mg·steer·d monensin (MON) in 0.91 kg dried distillers' grains with solubles. Periods were 70 d in length: 20 d of adaptation, 22 d of sample collection, and 28 d for withdrawal of treatment. Steers were group housed during adaptation and moved to individual covered pens for sampling. Hay, ort, and fecal grab samples were collected d 21 through 25 for determination of intake and digestion. Ruminal fluid was collected with a suction strainer 0, 2, 4, 8, and 12 h after feeding on d 42 for pH, VFA, and ruminal NH-N (RAN) analysis. Additionally, at h 2, ruminal fluid and contents were collected for determination of rate of NH production and CH production rate. No subspecies × monensin interactions were observed ( ≥ 0.12). Monensin had no effect ( ≥ 0.16) on intake or digestibility parameters. No subspecies effect ( ≥ 0.11) was observed for forage OM intake, total OM intake, or OM digestion. Total digestible OM intake tended to be greater ( = 0.06) for BT steers than for BI steers (14.0 vs. 12.2 g/kg BW). There was an effect of hour after feeding ( ≤ 0.01) on pH, total VFA, acetate:propionate ratio, and molar percent acetate and propionate. Total VFA concentration was greater ( = 0.01) in CON steers than in MON steers (66.5 vs. 62.0 m). Monensin decreased molar percent acetate ( = 0.02) from 72.5 to 71.2% and increased molar percent propionate ( < 0.01) from 16.9 to 18.7%, resulting in a reduced ( < 0.01) acetate:propionate ratio (from 4.34 to 3.85). Although not significantly ( = 0.19), monensin numerically reduced the CH production rate by 15.8%. Greater ( = 0.07) CH production rate tended to be observed in BI steers than in BT steers (21.4 vs. 16.6 μmol CH·mL·h, respectively). Monensin had no effect ( ≥ 0.32) on pH, RAN, or rate of NH production. A subspecies × hour after feeding interaction was observed for RAN, with BT having greater RAN at h 0 and 4, whereas BI had greater RAN at h 2, 8, and 12. Overall, monensin decreased the acetate:propionate ratio and total VFA concentration but had no effect on forage utilization. steers consumed less digestible OM and had a greater CH production rate compared with BT steers, suggesting BT were better able to utilize the available forage resource than BI.

Monensin Alters the Functional and Metabolomic Profile of Rumen Microbiota in Beef Cattle

“…Similar to the results of this study, several studies have reported the effectiveness of dietary monensin at altering the production and proportion of rumen fermentation acids. A recent study reported increased propionate concentrations in forage-fed beef steers consuming 200 mg d −1 of monensin [ 46 ]. Similarly, beef cattle consuming low-quality dry winter range grass fed 200 mg d −1 of monensin had a decrease in the molar percentage of acetate and an increase in the molar percentage of propionate in [ 47 ].…”

>b<Long-term use of narasin, salinomycin and flavomycin for Nellore steers fed with high-forage diets:>/b< ruminal parameters, apparent nutrient digestibility, and performance

“…In agreement with our data, Bell et al (2017) reported no differences in nutrient digestibility of beef steers receiving a forage-based diet with or without monensin.…”

Narasin inclusion for feedlot lambs fed a diet containing high amounts of ground flint corn

“…In a literature review containing 20 studies evaluating the use of lasalocid and monensin, Spears (1990) reported an increase of approximately 2 % in the digestible energy of the diets when these ionophores were used. Recent studies reported no differences in DM, OM, and NDF digestibility for beef steers fed with monensin (Bell et al, 2017) or narasin (Polizel et al, 2020). Bacteria that reduce succinate to propionate are resistant to the effects of ionophores; therefore, when these additives are used, propionate production tends to increase during ruminal fermentation (McGuffey et al, 2001).…”