Effects of narasin supplementation on dry matter intake and rumen fermentation characteristics of Bos indicus steers fed a high-forage diet

Abstract

This study evaluated the effects of narasin on intake and rumen fermentation characteristics of Bos indicus steers offered a high-forage diet for 140 d. On day 0 of the study, 30 rumen-fistulated Nellore steers [initial body weight (BW) = 281 ± 21 kg] were assigned to 30 individual pens in a randomized complete block design according to their initial BW. Animals were randomly assigned to 1 of the 3 treatments: 1) forage-based diet without narasin (CONT; n = 10), 2) CONT diet plus 13 ppm of narasin (13NAR; n = 10), and 3) CONT diet plus 20 ppm of narasin (20NAR; n = 10). The forage used was Tifton-85 (Cynodon dactylon spp.), whereas the carrier for narasin was a 50:50 mixture of soybean hull:corn. The experimental period was divided into 5 periods of 28 d each. Throughout the experimental period, total dry matter intake (DMI) was recorded daily, whereas mineral salt intake was recorded weekly. Blood and ruminal fluid samples were collected on day 0 (prior to treatment feeding), 28, 56, 84, 112, and 140 of the study. Moreover, total tract apparent nutrient digestibility was performed for a 5-d period every 28 d. No treatment effects were observed on forage, mineral, concentrate, or total DMI (P ≥ 0.22). Nonetheless, 13NAR tended to have a greater mineral intake vs. 20NAR cohorts (P = 0.08) Narasin-supplemented animals had reduced rumen acetate, Ac:Pr ratio, as well as greater (P ≤ 0.02) rumen propionate concentrations vs. CONT cohorts. Moreover, 13NAR increased rumen propionate and decreased butyrate, Ac:Pr vs. 20NAR cohorts (P ≤ 0.01). Throughout the experimental period, narasin-supplemented animals had reduced ammonia concentrations vs. CONT cohorts (P < 0.01), whereas no differences were observed between 13NAR and 20NAR (P = 0.80). No treatment or dose effects were observed (P ≥ 0.23) on DM, organic matter (OM), protein, neutral detergent fiber (NDF), acid detergent fiber (ADF), and mineral digestibility. Animals fed 13NAR had a reduced mean plasma urea concentration vs. CONT cohorts (P = 0.03), whereas no further differences were observed (P ≥ 0.12). In summary, narasin supplementation to beef steers offered a high-forage diet did not impact forage, mineral, and total DMI, as well as nutrient digestibility, whereas rumen fermentation characteristics, rumen ammonia, and plasma urea concentrations were positively impacted and lasted throughout the experimental period. Additionally, 13 ppm of narasin resulted in a reduced Ac:Pr ratio and rumen ammonia when compared to animals supplemented with 20 ppm.

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

“…In addition, the authors observed a decrease in the production of lactic acid when compared to other additives. As previously described, Polizel et al (2020) reported a reduction in the Ac:pr ratio and an increase in the total VFA concentration in cattle fed diets containing narasin, results that demonstrate an increase in the energy efficiency of the fermentation process. Therefore, further studies are needed to evaluate the effects of narasin on the ruminal environment, especially to identify the microorganisms affected by narasin inclusion.…”

“…Few studies have evaluated the effect of narasin on N metabolism in ruminants. Polizel et al (2020) reported lower ammonia concentration on rumen fluid and blood urea in steers fed high-forage diets with the inclusion of narasin; however, the authors did not evaluate N balance. In the present study, N had the capacity to decrease ammonia concentration; however, the decrease was lower than that promoted by M. Experiment 2.…”

“…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).…”

“…However, response level to supplementation of feed additives could be affected by grain processing (Meyer et al, 2013). Recent studies have shown that narasin does not affect the dry matter intake (DMI), but it does increase concentration of propionate (Pasqualino et al, 2020) and volatile fatty acids (VFA) (Polizel et al, 2020). In addition, the use of narasin increased the total milk production (Assis et al, 2020) and the plasma glucose concentration in sheep at the end of lactation (Sardinha et al, 2020).…”

>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

“…Narasin is an ionophore that alters rumen fermentation dynamics (Miszura et al, 2018), plasma metabolites (Sardinha et al, 2020;Polizel et al, 2020) and improves animal performance (Silva et al, 2015;Polizel et al, 2020). Salinomycin is also an ionophore that improves animal production by favorably altering molar acetate:propionate ratio (McClure et al 1980;Bagley et al, 1988).…”