Virginiamycin Research Articles

Investigation of virginiamycin to improve health of growing and finishing steers: I. Effects on ruminal acidosis and liver health*

ObjectiveOur objective was to observe the effects of the interrelationship among virginiamycin (VM) inclusion (240 mg/d), ruminal pH dynamics, and hepatic plasma metabolites on rumen and animal health during a 150-d feeding trial. Materials and MethodsSteers (304 ± 27 kg; n = 120) were assigned randomly to 1 of 6 dietary treatments: no VM (T000); VM for the last 50 d (T001); VM for the last 100 d (T011); VM for the first 50 d (T100); VM for the first 100 d (T110); and VM for 150 d (T111). All animals were orally administered 2 indwelling rumen pH and temperature recording boli on d 0 and 84. Blood samples were collected via jugular venipuncture on d −7, 28, 56, 84, 112, and 140, and plasma was analyzed for concentrations of albumin, alkaline phosphatase, direct bilirubin, total bilirubin, gamma-glutamyl transferase, and total protein using an automated blood analyzer. Concurrently, haptoglobin (HPT) was measured following a colorimetric method based on peroxidase activity. A random coefficients model with pen and animals within treatment as a random effect was used. Results and DiscussionAnimals that received VM for the first 100 d (T110 and T111) had greater mean ruminal pH during d 50 to 100 when compared with animals that did not receive VM (T000 and T001; 6.12 vs. 6.00, respectively). Moreover, T111 tended to have less time under pH 5.8 (3.01 h/d) when compared with T100 and T001 (5.83 and 6.45 h/d, respectively). At slaughter, overall, 3.36% of cattle in the study were identified with liver abscesses (A and A−), and 24.3% had lung lesions. Plasma metabolite concentrations before slaughter did not predict the presence of liver abscesses (P ≥ 0.182). Based on acute phase responses, HPT was notably lower on d 84 after diet transition in VM-treated animals (46.1 vs. 68.9 mg/L). Additionally, VM inclusion boosted indicators of overall health with greater alkaline phosphatase levels and albumin-toglobulin ratios. Implications and ApplicationsVirginiamycin has practical implications for rumen health and overall cattle health, where supplementation during the whole growing to finishing phases was more effective in capturing its full potential.

Impact of combined management strategies of monensin and virginiamycin in high energy diets on ruminal fermentation and nutrients utilization.

Feed additives such as monensin (MON) and virginiamycin (VM) are commonly utilized in feedlot diets to enhance rumen fermentation. Nevertheless, the precise effects of combining MON and VM during specific feedlot periods and the advantages of this combination remain unclear. This study was designed to investigate the effects of withdrawal of MON when associated with VM during the adaptation and finishing periods on ruminal metabolism, feeding behavior, and nutrient digestibility in Nellore cattle. The experimental design was a 5 × 5 Latin square, where each period lasted 28 days. Five rumen-cannulated Nellore yearling bulls were used (414,86 ± 21,71 kg of body weight), which were assigned to five treatments: (1) MON during the entire feeding period; (2) VM during the entire feeding period; (3) MON + VM during the adaptation period and only VM during the finishing period 1 and 2; (4) MON + VM during the entire feeding period; (5) MON + VM during the adaptation and finishing period 1 and only VM during the finishing period 2. For the finishing period 1, animals fed T3 had improved potential degradability of dry matter (p = 0.02). Cattle fed T3 and T5 had the highest crude protein degradability when compared to animals receiving T2 (p = 0.01). Animals fed T2 and T3 had reduced the time (p < 0.01) and area under pH 6.2 (p = 0.02). Moreover, animals fed T4 had greater population of protozoa from the genus Diplodinium (p = 0.04) when compared to those from animals fed T2, T3 and T5. For the finishing period 2, animals fed T3 had greater starch degradability when compared to animals receiving T4 and T5 (p = 0.04). Animals fed T3, T4 and T5 had increased the duration of time in which pH was below 5.6 (p = 0.03). The area under the curve for ruminal pH 5.2 and pH 5.6 was higher for the animals fed T3 (p = 0.01), and the area under pH 6.2 was higher for the animals fed T3 and T5 (p < 0.01) when compared to animals receiving T2. There is no substantial improvement on the rumen fermentation parameters by the concurrent utilization of MON and VM molecules, where the higher starch and protein degradability did not improve the rumen fermentation.

The influence of virginiamycin on digestion and ruminal parameters under feedlot conditions.

This experiment aimed to assess the impact of virginiamycin on in vitro gas production dynamics, rumen kinetics, and nutrient digestibility in beef steers fed a grain-based diet. Nine ruminally cannulated British-crossbred steers (596 ± 49kg) were assigned to this experiment. Animals were housed in three pens (n = 3/pen) equipped with a Calan gate feed system and water troughs. Pens were enrolled in a 3 × 3 Latin square design containing three periods of 16 d, and a 5-d washout interval between periods. Dietary treatments consisted of virginiamycin (VM) administration at 0 (VM0), 180 (VM180), or 240mg/d (VM240). During days 15 and 16 of each period, about 600mL of rumen fluid and urine samples were collected before (0h), and at 4, 8, 12, and 16h after the morning feed (0730 hours), rumen inoculum was used to take pH and redox potential measurements immediately after collection using a portable pH and redox meter, and subsamples were taken for volatile fatty acids (VFA) and NH3-N analyses, and urine samples were composited daily and analyzed for creatinine and purine derivatives (PD) content to estimate microbial crude protein flow. During the 4-h post-morning feed rumen collection, rumen inoculum was utilized to perform in vitro gas production measurements. Fecal samples were collected on day 16 of each period to estimate nutrient digestibility using acid detergent insoluble ash as an internal marker. Animals were considered the experimental unit for the statistical analyses, and periods and squares were included as random variables. The total and rate of gas production were similar among treatments (P ≥ 0.17). The second-pool (i.e., fiber) gas production increased linearly as VM inclusion increased (P = 0.01), with VM240 being greater compared to VM180 and VM0 (7.84, 6.94, and 6.89mL, respectively). Ruminal pH linearly increased as VM increased, with VM240 being greater than VM0 and VM180 intermediate (5.90, 5.82, and 5.86, respectively; P = 0.03). The VFA concentrations did not differ (P ≥ 0.13), but the acetate-to-propionate ratio was the highest in VM240 (P = 0.005). Branched-chain VFA increased (P ≤ 0.03) while lactate concentrations decreased (P = 0.005) linearly with VM. The ruminal NH3-N concentration was the lowest in the VM0 (P = 0.006). The estimated absorbed PD, purine derivative to creatinine index, and microbial N flow increased linearly with VM (P ≤ 0.07). The provision of VM influenced rumen dynamics in a dose-dependent manner.

Substituição de virginiamicina por produtos à base de levadura (Saccharomyces cerevisiae) em dietas de bovinos: Digestibilidade e parâmetros ruminais

Abstract The aim of this study was to evaluate the effect of substituting virginiamycin with yeastbased products in high-energy diets containing monensin on the nutrient digestibility and ruminal parameters of cattle. Five crossbred Nellore × Holstein steers (initial body weight 281 kg ± 9.2 kg) were allotted to a 5 × 5 Latin square design. The diets were composed in dry matter basis of corn silage (355 g kg-1), and concentrate composed of ground corn, soybean meal, soybean hulls,mineral mix, limestone, salt and urea (645 g kg-1). The treatments were: 1 - control, 18 mg kg-1 dry matter (DM) virginiamycin (VM); 2 - enriched yeast culture (Saccharomyces cerevisiae) at 7 g animal day-1 (EYC 7); 3 - enriched yeast culture (S. cerevisiae) at 14 g animal day-1 (EYC 14); 4 - autolyzed yeast (S. cerevisiae) at 7 g animal day-1 (AY 7); and 5 - autolyzed yeast (S. cerevisiae) at 14 g animal day-1 (AY 14). Monensin (18 mg kg-1 DM) was added to the mineral mix in all treatments. No significant differences (P &gt; 0.05) were found for DM intake (mean 8.36 kg DM), organic matter (OM) digestibility (average of 58.39%), or mean ruminal pH (mean 6.75) among treatments. Moreover, the treatment did not have a significant effect on the short-chain fatty acid or ammonia nitrogen concentrations. These results indicated the possibility of replacing virginiamycin with yeast-based products at the lowest level (7 g of enriched yeast culture or autolyzed yeast per animal day-1) in high-energy diets containing monensin.

366 Effects of Acidosis Bout Events on Animal Growth and Development, and the Effectiveness of Liver Abscess-Controlling Antibiotic on Diminishing Its Incidence

Abstract Ruminal acidosis is a common metabolic disorder that affects feedlot and dairy cattle and occurs when the supply of organic acids from fermentation exceeds its absorption, accumulating acid content in the rumen. Virginiamycin (VM) has inhibitory effects on primary liver abscess-causing bacteria. In feedlot animals, dietary VM has been shown to reduce rumen acidosis and improve feed conversion actively. This study evaluated ruminal pH over 150 days on feed (DOF) of growing and finishing beef cattle and investigated the relationships between ruminal pH and growth and development outcomes and the effectiveness of the continuous or intermittent provision of VM in 120 Angus-crossbred steers. Steers received VM (240 mg/d) as follows: no VM (T000); VM in the last 50 d (T001); VM for the last 100 d (T011); VM in the first 50 d (T100); VM in the first 100 d (T110); and VM for 150 d (T111). Animals were fed a grower-type diet (metabolizable energy [ME]: 2.45 Mcal/kg; crude protein [CP]: 12.2 % dry matter basis [DM]) for 50 d before the adaptation of a finisher-type diet (ME: 2.60 Mcal/kg; CP: 10.6% DM) over a 17-d period. The finisher-type diet was fed for the remaining 84 days. On d -1 and d 82 each animal received an indwelling pH bolus to record ruminal pH at 10-min intervals. Acidosis bout event was categorized as if the pH stayed below 5.6 for 3 hours. Data were analyzed using a random coefficient statistical model, binary data was analyzed using the logit link function and correlations were analyzed using PROC CORR in SAS (Table 1). Duration under pH 5.8 and 5.6 tended to have a negative correlation with gain to feed (G/F; P ≤ 0.080), and % of the time that pH remained below 5.6 when under 5.8 was negatively correlated with G/F (P = 0.007) and tended to have a negative correlation with average daily gain (ADG; P = 0.081). Similarly, acidosis bouts event and duration of bout event (DURB) tended (P ≤ 0.074) to have a negative correlation with G/F, while ADG was negatively correlated (P = 0.035). The number of acidosis bout events and probability of acidosis bout events to occur increase linearly (R2 = 0.89, P &amp;lt; 0.001, and R2 = 0.77; P &amp;lt; 0.001, respectively) as DOF progressed. The probability of an acidosis bout event decreased by 46% for the T111 treatment compared with T000 (35.43% vs. 18.82%; P = 0.049). Acidosis bout event seems to affect the growth and development of beef steers negatively, and it appears to be more critical as DOF progress. Administration of VM at 240 mg/d throughout the whole feeding period seems to reduce the incidence of acidosis bout events.

Label-free electrochemical immunosensor based on staphylococcal protein a and AgNPs-rGO-Nf for sensitive detection of virginiamycin M1

Virginiamycin (VIR), a feed additive, is used to promote pig and poultry growth. However, it is hazardous to human health. This work described a label-free electrochemical immunosensor based on silver nanoparticles-reduced graphene oxide (AgNPs-rGO) nanocomposites and staphylococcal protein A (SPA) for the first time to directly detect the residual marker VIR M1. Good catalytic currents for oxygen reduction reaction were apparently obtained after the modification of nanocomposites on gold electrode. Nanocomposites were characterized using UV–Vis, X-ray diffraction (XRD) patterns, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). SPA was targeted to immobilize VIR M1 monoclonal antibody (mAb) by binding to Fc region of antibody. The proposed immunosensor showed a wide linear range from 0.25 ng mL−1 to 100 ng mL−1, providing detection limit (LOD) of 0.18 ng mL−1 of VIR M1. Recovery rates ranged from 92.27% to 98.84%, and relative standard deviation (RSD) was not above 6.6%, indicating the immunosensor could detect VIR M1 in actual samples with high accuracy. The sensor showed good selectivity, reproducibility and stability and could be considered as a potential tool for detection of VIR M1 in feed and animal derived food.

Shortening the adaptation of Nellore cattle to high-concentrate diets using only virginiamycin as sole feed additive negatively impacts ruminal fermentation and nutrient utilization.

Feedlot cattle are usually adapted to high-concentrate diets containing sodium monensin (MON) in more than 14 days. However, considering that the dry matter intake DMI is usually lower during adaptation when compared to the finishing period, the use of MON during adaptation may decrease even further the DMI, and virginiamycin (VM) may be an alternative. This study was designed to investigate the effects of shortening the adaptation length from 14 to 9 or 6 days on ruminal metabolism, feeding behavior, and nutrient digestibility of Nellore cattle fed high-concentrate diets containing only VM as the sole feed additive. The experimental design was a 5 × 5 Latin square, where each period lasted 21 days. Five 17 mo-old Nellore yearling bulls were used (415 ± 22 kg of body weight), which were assigned to five treatments: (1) MON (30 mg/kg) and adaptation for 14 days; (2) MON (30 mg/kg) + VM (25 mg/kg) and adaptation for 14 days; (3) VM (25 mg/kg) and adaptation for 14 days; (4) VM (25 mg/kg) and adaptation for 9 days, and (5) VM (25 mg/kg) and adaptation for 6 days. A quadratic effect for adaptation length when only VM was fed was observed for mean pH (P = 0.03), duration of pH below 5.2 (P = 0.01) and 6.2 (P = 0.01), where cattle consuming VM adapted for 9 days had higher mean pH and shorter period of pH below 5.2 and 6.2. Cattle that consumed only MON had a lower concentration of butyrate (P = 0.02) and a higher concentration of propionate (P = 0.04) when compared to those consuming VM and adapted for 14 days. As the adaptation length decreased for animals consuming only VM, the rumen degradability of dry matter (P < 0.01), neutral detergent fiber (P < 0.01), and starch (P < 0.01) decreased; however, protozoa numbers of Entodinium and total protozoa increased. It is not recommended to shorten the adaptation length of these animals to either 6 or 9 days without negatively impacting nutrient disappearance and ruminal fermentation patterns.

Withdrawal of sodium monensin when associated with virginiamycin during adaptation and finishing periods on feedlot performance, feeding behavior, carcass, rumen, and cecum morphometrics characteristics of Nellore cattle.

Feed additives such as monensin (MON) and virginiamycin (VM) are widely used in feedlots diets to maximize rumen fermentation. However, the knowledge about the effects of MON and VM combinations in specifics feedlot periods and the benefits of this association are still unclear. This study aimed to evaluate the effects of withdrawal of MON when associated with VM during the adaptation and finishing periods on feedlot performance of Nellore cattle. The experiment was designed as a completely randomized block replicated six times (four animals/pen) in which 120 Nellore bulls (378.4 ± 24.4 kg) were allocated in 30 pens and fed for 112 days according to the following treatments: (T1) MON during the entire feeding period; (T2) VM during the entire feeding period; (T3) MON+VM during the adaptation period and only VM during the finishing period 1 and 2; (T4) MON+VM during the entire feeding period; (T5) MON+VM during the adaptation and finishing period 1 and only VM during the finishing period 2. After 112 days on feed, no treatment effect was observed for DMI (P ≥ 0.12). However, bulls fed T5 had greater (P = 0.05) final BW and ADG when compared to T1, T2, and T4. Cattle from T3 and T5 groups presented heavier HCW (P = 0.05) than that fed T1, T2, and T4. Nellore bulls fed T1 and T5 had lower (P < 0.01) DMI variation than those receiving T2. The withdrawal of MON when associated with VM during the final third of the feedlot period improved overall final BW, ADG, and HCW when compared to bulls fed either MON or VM, but did not positively impact feedlot performance when compared to cattle that had MON withdrawn at the end of the adaptation period.

Effects of lasalocid, narasin, or virginiamycin supplementation on rumen parameters and performance of beef cattle fed forage-based diet.

Two experiments were designed to evaluate the impacts of supplementing lasalocid (LAS), narasin (NAR), or virginiamycin (VRM) on rumen fermentation parameters, apparent nutrient digestibility, and blood parameters (Exp. 1), as well as feed intake and performance (Exp. 2) of Nellore cattle consuming a forage-based diet. In Exp. 1, 32 rumen-fistulated Nellore steers (initial shrunk body weight [BW] = 355 ± 4.4 kg) were assigned to a randomized complete block design. Within block, animals were randomly assigned to one of four treatments: 1) forage-based diet without feed additives (CON), 2) CON diet plus 13 mg/kg of dry matter (DM) of NAR, 3) CON diet plus 20 mg/kg of DM of sodium LAS, or 4) CON diet plus 20 mg/kg of DM of VRM. No treatment effects were detected (P ≥ 0.32) for intake and apparent digestibility of nutrients. Steers fed NAR had the lowest (P ≤ 0.01) molar proportion of acetate on day 28, 56, and 112 vs. CON, LAS, and VRM steers, whereas acetate did not differ (P ≥ 0.25) between LAS, VRM, and CON steers from day 28 to 84. On day 112, steers fed LAS had a lower (P < 0.02) molar proportion of acetate vs. VRM and CON, whereas it did not differ between CON and VRM (P > 0.33). Steers receiving NAR had a greater (P ≤ 0.04) ruminal propionate vs. CON, LAS, and VRM, whereas LAS steers had greater (P < 0.04) propionate vs. CON and VRM steers on day 28 and 112, and it did not differ (P > 0.22) between CON and VRM. In Exp. 2, 160 Nellore bulls were blocked by initial shrunk BW (212 ± 3.1 kg) in a 140-d feedlot trial. Diets contained the same treatments used in Exp. 1. Bulls fed NAR had greater (P < 0.02) average daily gain (ADG) vs. CON and VRM, and similar (P = 0.17) ADG between NAR and LAS, whereas ADG did not differ (P > 0.28) between LAS, VRM, and CON bulls. A treatment effect was detected (P = 0.03) for dry matter intake, being greater in NAR vs. CON, LAS, and VRM bulls, and similar (P > 0.48) between CON, LAS, and VRM bulls. A tendency was detected (P = 0.09) for feed efficiency, which was greater (P < 0.02) in NAR bulls vs. CON and VRM, and similar (P = 0.36) between NAR and LAS bulls. From day 112 to 140, bulls receiving NAR were heavier (P < 0.03) vs. CON, LAS, and VRM bulls, but no differences were observed (P > 0.51) between CON, LAS, and VRM bulls. Collectively, ruminal fermentation profile and intake were impacted by NAR supplementation, which partially contributed to the enhanced performance of Nellore bulls receiving a forage-based diet.

Combined use of monensin and virginiamycin to improve rumen and liver health and performance of feedlot-finished steers.

Monensin and virginiamycin are included in beef cattle finishing diets as prophylaxis to minimize the incidence of ruminal acidosis and liver abscesses. Due to different and probably complementary modes of action, this study aimed to determine the effects of a combination of monensin and virginiamycin, both included in the diet at recommended doses, on ruminal health, the occurrence of liver abscesses, and growth performance of feedlot-finished cattle. One hundred and forty-four steers (6 animals/pen) were fed 1 of 3 corn-based finishing diets containing 30 mg of monensin (MN), 25 mg of virginiamycin (VM), or 30 and 25 mg of monensin and virginiamycin (MN + VM), respectively, per kilogram of dry matter. Ruminal pH probes were inserted into two animals per pen and set to record pH every 10 min. On d 100, animals were slaughtered, and rumens and livers were recovered, on which occurrence and degree of ruminal damage, prevalence and number of liver abscesses, and liver scores (A-: livers with no more than two small abscesses; A+: livers with at least one large abscess or more than four medium abscesses; A: any other abscessed liver) were determined. Simultaneous inclusion of monensin and virginiamycin resulted in a 4.3% decrease (P < 0.04) in dry matter intake (DMI; 8.8, 9.2, and 9.2 ± 0.19 kg/d for MN + VM, MN, and VM-fed animals, respectively) and similar (P > 0.13) average daily body weight gain (ADG; 1.49 ± 0.021 kg/d) and hot carcass weight (HCW; 269 ± 1.7 kg), compared with feeding diets containing one additive or the other. Therefore, in terms of ADG, a 9.4% improvement (P < 0.01) in feed efficiency was observed in MN + VM-fed animals. Backfat thickness (5.6 ± 0.08 mm) and ribeye area (69.9 ± 0.53 cm2) remained unaffected (P ≥ 0.74), as well as the minimum (4.98 ± 0.047), mean (6.11 ± 0.037), and maximum ruminal pH (7.23 ± 0.033) values and the time (125 ± 22.3 min/d), area (57.67 ± 12.383 pH × h), and episodes (22 ± 3.8 bouts) of pH below 5.6 (P ≥ 0.12). Overall, prevalence (24 ± 3.4%) and the number of liver abscesses (1.6 ± 0.14 abscesses/abscessed liver), liver scores (20 ± 3.1% of A- and 4 ± 1.8% of A livers), and prevalence (67 ± 3.5%) and degree of damage to the ruminal epithelium (2.5 ± 0.22% affected surface) were similar (P ≥ 0.18) across treatments; however, the occurrence of ruminal lesions tended (P ≤ 0.07) to be associated with that of liver abscesses and reduced ADG when feeding monensin alone.

PSVIII-7 Impact of Virginiamycin on Rumen Fermentation and Methane Production in a Lactation Diet

Abstract To further understand the mode of action of virginiamycin (VM), an in vitro rumen fermentation study was conducted to determine the effects of VM on rumen fermentation and methane production using lactation diets. VM is approved for the control of liver abscesses in the United States and in preventing or treating ruminal acidosis in other countries. Three ruminally cannulated Jersey heifers were adapted to 53:47 forage to concentrate ratio diet for two weeks before use as rumen fluid donors. The treatments were control (CON) and VM (25 ppm). Diet was dried, ground to 1mm and used as substrate. Rumen fluid was collected two hours after feeding. Substrate (0.5 g) was inoculated with 100 mL of a 3:1 McDougall’s buffer:ruminal fluid mixture for 24 h at 39°C and constant agitation. Each treatment was run in triplicate and in three runs. Data were analyzed with a mixed model including treatment as the fixed effect and experimental run as a random effect using SAS software 9.4. Statistical significance was set when P≤0.05. Maximum gas production was less (P &amp;lt; 0.01) in VM compared with CON (100 vs. 130 mL/g incubated DM). VM tended to reduce methane production per unit digested DM (6.71 vs. 9.88 mg/g digested DM; P=0.07) and per unit incubated DM (4.40 vs. 7.16 mg/g incubated DM; P=0.06). VM increased propionate molar % compared to CON (21.4 vs. 16.2%, P&amp;lt; 0.01). VM reduced acetate:propionate compared to CON (2.84 vs. 3.85, P = 0.01). VM reduced DMD (65.5 vs. 72.5%, P=0.02) without reducing total VFA concentration compared with CON. VM tended to increase pH compared with CON (6.73 vs. 6.68, P=0.07). VM reduced methane production, increased propionate proportion, and maintained rumen pH in an in vitro fermentation system using an early lactation diet.

57 Evaluation of Virginiamycin Inclusion in the Diets of Feedlot Steers: Interplay between Rumen pH and Liver Health

Abstract In the beef cattle system, liver abscesses are the most common liver abnormality and are the leading cause for condemnations at slaughter. Virginiamycin (VM) has been used to prevent sub-acute ruminal acidosis (SARA) and subsequently control liver abscess incidence. This study observed the interrelationship between VM inclusion (240 mg/hd/d), ruminal pH dynamics, and hepatic blood metabolites over a 150-d feeding trial. Housed in a Calan gate system, 120 Angus crossbred steers (291 ± 28 kg) were randomly assigned to 1 of 6 dietary treatments: no VM (T000); VM for the last 50 d (T001); VM for the last 100 d (T011); VM for the first 50 d (T100); VM for the first 100 d (T110); and VM for 150 d (T111). Steers were orally administered 2 indwelling smaXtec rumen pH and temperature recording boluses on d -4 and d 84. On d -7, 28, 56, 84, 112 and 140, blood samples were collected via jugular venipuncture and all plasma samples were analyzed for concentrations of albumin, alkaline phosphatase, direct bilirubin, total bilirubin, gamma-glutamyl transferase, and total protein using an automated blood analyzer (Carysta High Volume Chemistry Analyzer; Zoetis). Haptoglobin (HPT) was measured following a colorimetric method based on peroxidase activity. Data were analyzed using a random coefficients model with the pen as a random effect and animals within treatment as the subject. Results indicated that VM did not convalesce hepatic function (P &amp;gt; 0.05), but HPT had increased concentrations on d 84 for VM excluded treatments (42.75 vs. 93.25 mg/L). Comparatively, T111 tended to have less time under pH 5.8 (2.50 h/d) when compared with T001, T100, and T000 (5.27; 4.94; and 4.23 h/d, respectively; P = 0.107). Therefore, VM should be fed from the growing phase to slaughter to capture the full potential of the product on animal health status.

Residual concentrations of antimicrobial growth promoters in poultry litter favour plasmid conjugation among Escherichia coli.

Considering that plasmid conjugation is a major driver for the dissemination of antimicrobial resistance in bacteria, this study aimed to investigate the effects of residual concentrations of antimicrobial growth promoters (AGPs) in poultry litter on the frequencies of IncFII-FIB plasmid conjugation among Escherichia coli organisms. A 2 × 5 factorial trial was performed invitro, using two types of litter materials (sugarcane bagasse and wood shavings) and five treatments of litter: non-treated (CON), herbal alkaloid sanguinarine (SANG), AGPs monensin (MON), lincomycin (LCM) and virginiamycin (VIR). E.coli H2332 and E.coli J62 were used as donor and recipient strains, respectively. The presence of residues of monensin, lincomycin and virginiamycin increased the frequency of plasmid conjugation among E.coli in both types of litter materials. On the contrary, sanguinarine significantly reduced the frequency of conjugation among E.coli in sugarcane bagasse litter. The conjugation frequencies were significantly higher in wood shavings compared with sugarcane bagasse only in the presence of AGPs. Considering that the presence of AGPs in the litter can increase the conjugation of IncFII-FIB plasmids carrying antimicrobial resistance genes, the real impact of this phenomenon on the dissemination of antimicrobial resistant bacteria in the poultry production chain must be investigated.

Efeitos de antibióticos promotores de crescimento e do concentrado sobre o consumo, digestibilidade, degradabilidade e variáveis ruminais de novilhos de corte

ABSTRACT The objective of this study was to evaluate the addition of antibiotic growth promoters to concentrate on intake, digestibility, in situ degradability and ruminal variables in steers. Four steers in a Latin square design were fed hay (ad libitum), concentrate [10g kg-1 of body weight (BW)] and mineral mix (0.272g kg-1 of BW). The additives (0.75mg kg-1 of BW) were incorporated in the mineral mix as follows: Control (no antibiotics), lasalocid (LASA), salinomycin (SALI) or virginiamycin (VIRG). Antibiotic did not affect intake, pH, volatile fatty acids (VFA) and digestibility of dry matter (DM), organic matter, crude protein, ethereal extract, and non-fibrous carbohydrates. The LASA and SALI tended (P=0.09) to reduce the digestibility of neutral detergent fiber (NDF). The SALI and VIRG tended (P=0.09) to reduce the DM disappearance, and VIRG tended (P=0.06) to reduce the NDF disappearance in the rumen. The SALI and VIRG reduced the effective degradation and only SALI reduced the concentration of N-NH3 in the rumen. Thus, the antibiotics did not affect intake, pH, VFA and digestibility, but decreased the degradation of fiber and only SALI reduced the concentration of ammonia nitrogen (N-NH3) in the rumen.

Interaction of early metabolizable protein supplementation and virginiamycin on feedlot growth performance and carcass characteristics of calf-fed Holstein steers.

One hundred sixty-eight Holstein steer calves (133.4 ± 7.9 kg) were used to evaluate the influence of virginiamycin (VM) supplementation on cattle growth performance and liver abscess incidence, and the effect of feeding 100% vs. 87% of metabolizable protein (MP) requirements during the initial 112 d on growth performance, efficiency of energy utilization, and carcass characteristics. Steers were balanced by weight and assigned to 28 pens (6 steers/pen). During the initial 112-d feeding period, dietary treatments consisted of two levels of MP (100% vs. 87% of expected requirements) supplemented with or without 22.5 mg/kg VM in a 2 × 2 factorial arrangement. There were no VM × MP supplementation interactions (P ≥ 0.14) on any of the parameters measured in both experiments. Calf-fed Holstein steers supplemented with VM increased (P ≤ 0.03) overall average daily gain (ADG), feed efficiency (G:F), observed/expected net energy (NE) values for maintenance and gain, and final body weight (BW). Cattle fed VM also increased (P ≤ 0.04) carcass weight, dressing percent, and longissimus muscle area. However, there was no effect (P ≥ 0.22) of VM supplementation on any other carcass characteristics. Calf-fed Holstein steers fed 100% MP requirements during the initial 112-d feeding period had greater (P ≤ 0.02) ADG, G:F, observed/expected NE values for maintenance and gain, and live BW compared with steers fed 87% of the expected MP requirements. However, there was no effect (P ≥ 0.17) of MP supply during the initial 112-d period on overall (342 d) growth performance measurements. The incidence of liver abscesses was low (averaging 7.7%) and not affected by dietary treatments. We conclude that, independent of MP supplies, supplemental VM enhances overall growth performance and efficiency of energy utilization of calf-fed Holstein steers.

Use of virginiamycin improves performance of high-prolific sows during gestation and lactation over two cycles

Feed additives can be used as potential strategies to enhance the efficiency of nutrient utilization by the sow can impact on the reduction of feed costs and in addition improve sow and litter health. The objective of this study was to evaluate the impact of the supplementation of virginiamycin (VM) in diets for gestating and lactating sows over two consecutive productive cycles on the animals productive and reproductive performance. Sows that received VM showed a lower BW, body protein and energy losses during both lactations when compared to control sows (P = 0.001). VM treatment increased (+6%; P = 0.001) piglet weaning weight. The litter daily gain was also influenced (P = 0.001) by the treatments were litters from VM fed sows showed an improved daily gain when compared to control sows (2.61 vs. 2.24 kg d-1 respectively). Average daily milk production improved by 17% (P = 0.001) in the VM sows when compared with the control. Also, an improvement in milk fatty acid profiles were found in sows fed VM. As a conclusion, we can infer that the constant use of VM in the diets of sows during gestation and lactation improves both sow and litter performance.

Feed intake, nutrient digestibility, and selected rumen parameters in feedlot bulls fed diets with different feed additives.

An experiment was conducted to evaluate the feed intake, nutrient digestibility and selected rumen parameters in feedlot bulls fed diets containing different feed additives. Six rumen-cannulated Nellore bulls (age = 8 ± 1.0 months; initial BW = 225 ± 13.2 kg) were distributed in a 6 × 6 Latin square design. Six experimental diets based on 30% corn silage and 70% concentrate on a dry matter (DM) basis were evaluated. Diets differed in feed additive on a DM basis, as follows: 1.4% bicarbonate and magnesium oxide in 3:1 ratio (BOX); 36 ppm lasalocid sodium (LAS); 30 ppm monensin sodium (MON); 25 ppm virginiamycin (VIR); 30 ppm monensin sodium plus 25 ppm virginiamycin (MV); and 3.15% commercial mineral supplement containing D-limonene and exogenous α-amylase (EOA). The experiment lasted 144 d, with six periods of 24 d. Each period consisted of 14 d for dietary adaptation, 3 d for feces and urine collection, and 7 d for omasal and ruminal digesta collection. Bulls fed the BOX diet showed greater (P < 0.05) intake of DM, organic matter (OM), neutral detergent fiber (apNDF), crude protein (CP), and starch compared to the other diets. Diets with LAS, MON, VIR, MV, or EOA did not influence (P > 0.05) the DM, OM, apNDF, CP, or starch intake of feedlot bulls. Bulls fed the EOA diet showed greater (trend; P = 0.09) ruminal digestibility of starch compared to the other diets. The feed additives did not affect (P > 0.05) the intestinal or total tract digestibility of starch, rumen pH, microbial efficiency, total rumen fluid, dilution rate, rate of intake, rate of degradation, or passage rate of the DM, OM, apNDF, and starch. In conclusion, LAS, MON, VIR, MV, and EOA diets reduced nutrient intake compared to BOX. Although all feed additives presented similar effects on rumen pH, temperature, and kinetics the presence of exogenous α-amylase in the EOA diet may increase ruminal starch digestibility and apparent total tract digestibility of DM and OM.

Monensin associated or not with virginiamycin or functional oil for feedlot beef cattle.

The objective of this study was to evaluate diets containing monensin (MON) associated or not with virginiamycin (VM) or functional oil based on cashew nut shell and castor beans (FOcc) for beef cattle in feedlots on nutritional (intake and digestibility) and productive parameters. A total of 1410 non-castrated Nellore cattle were selected, with an average age of 18months and with an initial mean body weight (BW) of 305 ± 41.52kg. The diet showed a roughage to concentrate ratio of 23:77, with the supply of corn silage as a source of roughage. The following additive inclusions in the diet were evaluated: (1) MON: 27mg MON/kg dry matter (DM); (2) MON + VM: 22mg MON/kg DM + 19mg VM/kg DM; and (3) MON + FOcc: 22mg MON/kg DM + 500mg FOcc/kg DM. Statistical analyses were obtained through a linear model using initial BW and days of feedlot as covariables and comparisons between treatments using mutually orthogonal linear contrasts with a 5% significance level. The association or not of MON with VM or FOcc does not affect any of the nutritional and productive parameters evaluated. Animals that receive diets with MON + VM have higher average daily gain and feed efficiency (FE) than those that receive MON + FOcc without showing differences in nutritional parameters. The supply of MON associated with VM or FOcc does not increase intake and productive performance and, consequently, efficiency of feedlot beef cattle. However, in the case of use associated with MON, the VM provides greater performance than FOcc without changing food intake.

Supplement levels and functional oils to replace virginiamycin for young bulls during early dry season on grasslands and finishing phase in feedlot systems

Aim of study: To assess the effects of replacing virginiamycin (VM) by functional oils (FO) from castor beans and cashew nut on beef cattle system during the early dry season (Experiment I) and during the finishing phase were evaluated the historical effect, keeping the treatments and methods intact (Experiment II).Area of study: These experiments were conducted at the Forage Crops and Grasslands section of São Paulo State University, “Julio de Mesquita Filho” (Unesp–Jaboticabal, São Paulo, Brazil).Material and methods: Two supplementation levels combined with two additives (four treatments in total) were evaluated: LSVM, low supplementation (0.3% body weight [BW]) with VM; LSFO, low supplementation (0.3% BW) with FO, HSVM, high supplementation (0.6% BW) with VM, and HSFO, high supplementation (0.6% BW) with FO. In both experiments, the experimental design was completely randomized with a 2 × 2 factorial arrangement (supplementation levels × additives).Main results: In Exp. I, the additive effect of VM provided greater average daily gain (ADG, p=0.02), higher supplementation level resulted in higher ADG (p=0.04) and the greatest crude protein apparent digestibility (p=0.002). However, no effects were observed between supplementation levels, additives, and interactions (p≥0.11) on voluntary intake and ruminal parameters. In Exp. II, LSVM treatment resulted in lower dry matter intake (p=0.04). Animals maintained on LSFO during the early dry season exhibited lower carcass yield (p=0.004).Research highlights: FO can be used to replace VM in beef cattle diet during the finishing phase in the feedlot without altering animal performance.

The Potential of Shortening the Adaptation of Nellore Cattle to High-Concentrate Diets Using Only Virginiamycin as Sole Feed Additive.

Feedlot cattle are usually adapted to high-concentrate diets containing sodium monensin (MON) in more than 14 days. However, for finishing diets with lower energy content, the use of MON during adaptation may hold dry matter intake (DMI), and virginiamycin (VM) may be an alternative. This study was designed to determine the potential of shortening the adaptation of Nellore cattle to high-concentrate diets using only VM as a sole feed additive relative to feedlot performance, feeding behavior, and ruminal and cecum morphometrics. The experiment was designed as a completely randomized block replicated six times (four animals/pen) in which 120 Nellore bulls (390.4 ± 19.0 kg) were fed in 30 pens for 111 days according to the following treatments: (1) MON and adaptation for 14 days (MON14), (2) MON + VM and adaptation for 14 days (MONVM14), (3) VM and adaptation for 14 days (VM14), (4) VM and adaptation for 9 days (VM9), and (5) VM and adaptation for 6 days (VM6). At the end of the adaptation, 30 animals (n = 1 per pen) were randomly slaughtered for rumen and cecum evaluations. The remaining 90 bulls were harvested at the end of the study. No effects of treatments were observed (P < 0.10) for final body weight, average daily gain (ADG), and hot carcass weight (HCW). Cattle fed VM14 presented a greater (P ≤ 0.03) DMI, expressed as percent of body weight (BW), than animals fed either MON14 or MONVM14; however, cattle fed either MON14 or MONVM14 improved (P ≤ 0.02) the gain-to-feed ratio (G/F) by 10.4 or 8.1%, respectively, when compared to bulls fed VM14. Bulls fed VM14 had smaller (P < 0.05) papillae area (0.34 vs. 0.42 cm2) and rumen absorptive surface area (28.9 vs. 33.8 cm2) than those fed MON14. The shortening of the adaptation period linearly decreased the 12th rib fat (P = 0.02) and biceps femoris fat daily gain (P = 0.02) of Nellore bulls fed only VM, which linearly decreased the final biceps femoris fat thickness (P < 0.01). Feedlot cattle fed VM as a sole feed additive should not be adapted to high-concentrate diets in less than 14 days. Regardless of either adaptation length or feed additive, feedlot cattle need at least 14 days to adapt to finishing diets.