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Recent studies have indicated that nanofluids that combine silica nanoparticles and low salinity water have a promising character as Enhanced Oil Recovery agents for application in sandstones. In view of that, this work aimed to investigate the stabilization mechanism of silica nanoparticles in aqueous medium and the effects that low-salinity silica nanofluids induce on fluid/fluid and rock/fluid interactions in order to generate contributions to the understanding of the oil recovery mechanisms of this potential injection fluid. Therefore, experiments were carried out with nanofluids containing silica nanoparticles at concentrations between 0.01 and 0.2 wt% dispersed both in deionized water (DW) and in a low salinity water (LSW) containing a Total Dissolved Solids of 1343.4 mg/L. The results showed that the dynamic viscosity of the nanofluids exceeds that of DW by, at most, only about 4.23%. The size of the silica nanoparticles in the nanofluids did not increase over 200 nm and was not consistently affected by factors such as nanoparticle concentration, dispersing fluid or time elapsed after sonication of the nanofluids. In general, the interfacial tension between the crude oil and DW was not substantially changed when the aqueous phase was replaced by the nanofluids. On the other hand, the zeta potential of silica nanoparticles was significantly decreased when they were dispersed in LSW in comparison to DW. The contact angle analyzes evidenced the ability of the nanofluids in altering the wettability of crude-oil aged sandstone surfaces towards more water-wet conditions, notably the nanofluids with higher concentrations of silica nanoparticles and prepared with LSW.

Narasin is a coccidiostatic and antibacterial agent and may change rumen fermentation. The objective in this trial was to determine the effects of monensin or narasin on rumen metabolism of steers during the period of adaptation after abrupt transition from high-forage to high-concentrate diet. Eight Nellore steers (BW 475.7 ± 3.7 kg), cannulated in the rumen, were used in a replicated 4x4 Latin Square design. The trial lasted 96 days, divided in 4 periods of 24 days each. Steers were fed daily with coastcross haylage during the first 8 d of each period. From day 9 to 24, steers were fed with the experimental diets, which were composed by 90% of concentrate. The experimental diets were: C (Control: no additives added), Mon (25 mg of monensin/kg of DM), N10 (10 mg of narasin/kg of DM) and N20 (20 mg of narasin/kg of DM). The rumen fluid was collected every four hours (starting prior feeding, 4, 8 and 12 hours after feeding), from days 8 to 14 of each period. Short chain fatty acid (SCFA) and rumen pH were analyzed as repeated measures over time using MIXED procedure. The effect of the experimental diets was evaluated using the Tukey test. There was no effect of experimental diets for acetate (59.86 ± 0.86 mM/100 mM, P = 0.20), propionate (22.15 ± 0.77 mM/100 mM, P = 0.14), butyrate (13.14 ± 0.67 mM/100 mM, P = 0.38), isovalerate (2.43 ± 0.16 mM/100 mM, P = 0.36) and acetate-to-propionate ratio (2.77 ± 0.12, P = 0.19). However, steers fed Mon had a greater molar proportion of isobutyrate (C: 1.03b; Mon: 1.11a; N10: 1.01b; N20: 1.07ab± 0.05 mM/100 mM, P = 0.03) than C and N10. The Mon and N10 experimental diets decreased molar proportion of valerate (C: 1.18a; Mon: 1.01b; N10: 1.05b; N20: 1.11ab± 0.06 mM/100 mM, P = 0.02). Diet containing monensin decreased total SCFA (C: 143.9a; Mon: 132.6b; N10: 145.8a; N20: 140.4ab± 6.70 mM/L, P = 0.03) than C and N10. Steers submitted to Mon and N20 diets had a greater ruminal pH than steers fed C and N10 diets (C: 6.18b; Mon 6.36a; N10: 6.18b; N20: 6.30a± 0.12, P = 0.01). The inclusion of 20 mg of narasin or 25 mg of monensin/kg of DM had a promising effect by increasing the ruminal pH during adaptation to high-concentrate diets.

Previous studies have demonstrated that narasin, a coccidiostatic and antibacterial agent, may improve performance of forage-fed cattle due to rumen fermentation changes. The objective of this trial was to determine the effects of narasin inclusion into a mineral mixture (MM) on performance of grazing steers. Two hundred and forty Nellore steers (12 ± 1 mo of age) were blocked by initial BW (177 ± 0.21 kg), and assigned to 30 lots (8 steers/lot and 10 lots/treatment). Sixty paddocks ofBrachiaria brizanthawith 1 ha each were used and each paddock was continuously grazed by 28 d, followed by 28 d of rest. A paddock rotation among treatments was designed every 28 d to minimize the effect of variation among pastures. Paddocks were assigned to receive 1 of 3 treatments: a control (no narasin; 0N), and an intake of 71.5 (13N) and 110 (20N) mg of narasin (Zimprova®; Elanco, São Paulo, Brazil) per day, corresponding to 13 and 20 ppm considering 2.5% the DMI of steers. Narasin was added in the MM by adjusting their concentration in each period, according to MM intake (MMI) in the previous period. The MMI was evaluated on a weekly basis, starting 28 d before the beginning of the experiment. Forage mass in the paddocks was measured by choosing two points upon entry and exit of the lot from each pasture. All data were analyzed using the PROC MIXED procedure of SAS and evaluated by period (every 28-d) and overall (d 0 to 84). No treatment × period (P= 0.85) or treatment (P= 0.23) effects were observed for daily MMI (64, 61, and 58 g for 0, 13, and 20N, respectively; SEM = 2.19). Conversely, a treatment × period interaction was observed (P= 0.002) for ADG, because ADG was greater (P≤ 0.01) for 13N and 20N in the 1st and 2nd periods and also greater (P= 0.03) for 20N vs 13N in the first 28 d of the study, whereas no differences (P≥ 0.18) were observed in the last 28 d. Moreover, overall ADG was also greater (P≤0.01) for 13N and 20N when compared with cohorts receiving 0N, without differences between 13 and 20N (P= 0.65; 0.493, 0.575, and 0.585 kg/d, respectively; SEM = 0.0150). In summary, narasin inclusion into the mineral mixture did not impact mineral intake and improved overall steers performance during an 84-day period.

Narasin, an ionophore used in poultry, improved BW gain and feed efficiency in cattle fed high forage. However, there is little information about the effect of narasin for cattle fed a high-grain diet. The objective of this study was to determine the effect of adding narasin in the mineral mixture (MM) on gain and intake of feedlot Nellore heifers fed a high-grain diet. Sixty heifers at 12 ± 1 mo of age were assigned to a randomized complete block design, defined by initial BW (244 ± 4 kg), and housed in 20 pens (3 per pen). The experimental treatments were either a control, with no narasin added, or Narasin, with 1,300 mg of narasin per kilogram of MM. The diet was composed of 15.8% (DM basis) sugar cane bagasse, 70.8% ground corn, 12.9% soybean meal, and 0.5% urea. Treatments were arranged in a crossover design (all pens underwent all treatments) with 2 experimental periods of 28 d each, and between periods, there was a 7-d washout. Heifers were weighed at the beginning and at the end of each experimental period to calculate ADG. All days, MM was offered and orts were collected to calculate the MM intake (MMI). The ADG and feed efficiency were submitted to ANOVA by the MIXED procedure (SAS 9.3). The DMI and MMI were analyzed as repeated measures over time using the same procedure. The statistical model was composed by effect of treatments, periods, and pens. The addition of narasin in MM did not affect DMI (6.59 for the control and 6.55 kg/d for the Narasin treatment [SEM 0.25,P= 0.56]), MMI (57.6 for the control and 55.6 g/d for the Narasin treatment [SEM 11.9,P= 0.33]), and ADG (1.09 for the control and 1.17 kg for the Narasin treatment [SEM 0.04,P= 0.06]). However, the addition of 1,300 mg of narasin/kg of MM increased feed efficiency compared with the control treatment (0.165 for the control and 0.179 for the Narasin treatment [SEM 0.01,P= 0.05]). Based on DMI and MMI, the narasin intake was 10.6 mg/kg. The inclusion of narasin in MM increased feed efficiency in feedlot Nellore heifers fed a high-grain diet without affecting MMI and DMI.