Animal performance
Final body weight was highest (P < 0.036) for bulls fed MOVI (558.7 kg) and MOMY (554.6 kg) diets, intermediate for bulls fed MONE (529.3 kg) diet, and lowest for bulls fed CONT (514.6 kg; Table 2).
Table 2
Performance and feed intake of beef cattle finished in feedlot and fed high-grain diets with monensin, virginiamycin and micro minerals mixture and yeast
Parameters | | | Diets | | | |
CONT1 | MONE2 | MOVI3 | MOMY4 | SEM5 | P-value |
Initial body weight, kg | 382.9 | 385.0 | 389.3 | 384.9 | 3.84 | 0.673 |
Final body weight, kg | 514.6c | 529.3b | 558.7a | 554.6a | 6.32 | 0.036 |
Average daily gain, kg/d | 1.57c | 1.72b | 2.02a | 2.02a | 0.06 | 0.032 |
Dry matter intake, kg/d | 8.79 | 8.61 | 8.94 | 8.99 | 0.14 | 0.583 |
Dry matter intake, % BW | 1.96 | 1.84 | 1.89 | 1.91 | 0.19 | 0.055 |
Feed conversion, DMI/ADG | 5.61c | 5.01b | 4.43a | 4.45a | 0.03 | 0.031 |
1CONT – without additives; 2MONE – inclusion of 30 mg/kg of monensin (DM basis); 3MOVI – inclusion of 30 mg/kg of monensin (DM basis) + 30 mg/kg of virginiamycin (DM basis); 4MOMY – inclusion of 30 mg/kg of monensin (DM basis) + 3 g/kg of BW of minerals traces and yeast; 5Standard error of means. Means followed by different letters differ. |
The ADG was similar and higher (P < 0.032) for bulls fed MOVI (2.02 kg) and MOMY (2.02 kg) diets, intermediate for bulls fed MONE (1.72 kg) diet, and lower for bulls fed CONT (1.57 kg; Table 2). The inclusion of monensin alone in the diet increased ADG by 9.6% when compared to CONT diet. On the other hand, MOVI or MOMY diets increased the ADG by 28.7% when compared to CONT diet and 17.5% when compared to the MONE diet. Thus, the inclusion of monensin with either virginiamycin or the mineral trace and yeast had a positive synergism resulting in improved animal performance. Overall, the inclusion of monensin in the diet of cattle finished in feedlot improves animal performance by ~ 12% (Duffield et al., 2012; Goodrich et al., 1984). Similarly, virginiamycin improves animal performance by ~ 6% (Montano et al., 2015; Rogers et al., 1995). Castagnino et al. (2018) observed 14% improved weight gain in Nellore bulls fed a high grain diet and supplemented with virginiamycin (25 mg/kg DM).
The observed ADG for bulls from diets MOVI or MOMY (2.02 kg/day) can be considered high when compared to the other studies realized in similar conditions (Fugita et al., 2018; Ornaghi et al., 2017; Souza et al., 2018; Valero et al., 2016). Similarly, the ADG for MONE diet (1.72 kg/day) can also be considered high when compared to the same studies. The increased animal performance observed in this study is likely due to the high concentrate:corn silage fed to the bulls. High-energy diets determine higher animal performance (Dian et al., 2010; Fugita et al., 2012; Rivaroli et al., 2017).
Feed intake and feed efficiency
Dry matter intake (DMI, 8.83 kg/d) and the intake of other nutrients were similar (P > 0.05) among treatments (Table 2). Several factors influence DMI, such as the animal body weight (DMI/kg BW ratio). Therefore, DMI and BW ratio are usually employed to compare the DMI of cattle finished in the feedlot. DMI/BW ratio was similar (P > 0.05) among bulls fed the four diets (1.90%). Therefore, the inclusion of monensin, monensin + virginiamycin, or monensin + mineral trace and yeast did not alter feed intake. Feed intake was low when compared to studies conducted under similar concentrate:forage ratio diets, which usually ranges from 2.0 to 2.5% BW (Fugita et al., 2018; Ornaghi et al., 2017; Valero et al., 2016). In some studies, the DMI expressed as % of BW was greater than 2.5% (Eiras et al., 2017; Prado et al., 2015) and few had values below 2.0% (Souza et al., 2019; Zawadzki et al., 2011). These results could be explained in part by the concentrate and corn silage ratio (85% vs. 15%), which reduces the DMI (Rivaroli et al., 2017; Souza et al., 2019).
Feed conversion (kg DM/kg ADG) was similar (P > 0.05) for bulls fed MOVI (4.43) and MOMY (4.45) diets, with both being more efficient than bulls fed MONE (5.01) and CONT (5.61) diets (Table 2). The highest feed conversion was observed for bulls fed CONT diet. Thus, the inclusion of monensin in the diet improved feed conversion efficiency by 12.0%. On the other hand, the inclusion of monensin + virginiamycin or monensin + Advantage mineral trace and yeast improved feed efficiency by 26.7%. Generally, under similar feeding conditions, animal genetic characteristics, feedlot period, and concentrate:corn silage ratio the feed conversion ranged from 5.0 to 6.5 kg DM/kg ADG (Cruz et al., 2014; Fugita et al., 2018; Ornaghi et al., 2017; Souza et al., 2018; Valero et al., 2015). High-grain diet supplemented with monensin, monensin + virginiamycin, or monensin + mineral trace and yeast during 84 days of feedlot resulted in good feed conversion (below 5.0 kg DM/kg ADG).
Carcass characteristics
The HCW and CCW were highest for bulls fed MOMY and MOVI diets, intermediate for bulls fed MONE, and lowest for bulls fed diet (Table 3).
Table 3
Carcass characteristics of beef cattle finished in feedlot and fed high-grain diets with monensin, virginiamycin and micro minerals mixture and yeast
Parameters | | | Diets | | | |
| CONT1 | MONE2 | MOVI3 | MOMY4 | SME5 | P-value |
Hot carcass weight, kg | 295.7c | 301.8b | 311.2a | 317.2a | 2.61 | 0.045 |
Cold carcass weight, kg | 286.6c | 291.6b | 303.2a | 309.9a | 2.54 | 0.039 |
Hot carcass dressing, % | 57.45 | 57.01 | 55.71 | 57.20 | 0.62 | 0.343 |
Cold carcass dressing, % | 55.67 | 55.05 | 54.22 | 55.83 | 0.57 | 0.355 |
Carcass chilling loss, % | 1.78b | 1.94b | 1.44a | 1.35a | 0.26 | 0.046 |
Liver, kg | 6.46a | 5.53b | 6.48a | 5.42b | 1.04 | 0.045 |
1CONT – without additives; 2MONE – inclusion of 30 mg/kg of monensin (DM basis); 3MOVI – inclusion of 30 mg/kg of monensin (DM basis) + 30 mg/kg of virginiamycin (DM basis); 4MOMY – inclusion of 30 mg/kg of monensin (DM basis) + 3 g/kg of BW of minerals traces and yeast; 5Standard means error. Means followed by different letters differ. |
The largest differences between HCW and CCW were observed for bulls fed MOMY diet compared to bulls fed CONT diet, + 21.5 and + 23.3 kg, respectively (P < 0.05). The differences between HCW and CCW for bulls fed MOMY diet compared to bulls fed MONE diet were + 15.4 and + 18.3 kg, respectively. The differences in HCW and CCH between bulls fed MOVI and CONT diets were + 15.5 and + 16.6 kg, respectively. Thus, the inclusion of monensin + virginiamycin or monensin + mineral trace and yeast resulted in a positive synergism between HCW and CCW. Greater HCW and CCW for bulls fed on MOMY and MOVI diets are due to the greater FBW and carcass dressing.
Hot carcass dressing and CCD were similar (P > 0.05) among the diets; with means of 56.8% and 55.2%, respectively (Table 3). Thus, the inclusion of monensin, virginiamycin, or micro mineral mixture with yeast does not influence HCD and CCD. Goodrich (1984) conducted a comprehensive review of studies using monensin in diets of feedlot-finished cattle and found no effect of the inclusion of monensin on carcass traits. However, the carcass dressing observed in this experiment (56.8%) was high for crossbred bulls (European vs. Nellore). In general, HCD of crossbred European vs. Zebu bulls finished in the feedlot is below 55% (Eiras et al., 2017; Fugita et al., 2012; Fugita et al., 2018; Ornaghi et al., 2017; Souza et al., 2019).
Chilling losses (24 hours at 4° C after slaughter) were lower for carcasses of bulls fed MOMY (1.35%) or MOVI (1.44%) compared to chilling losses of carcasses from bulls fed MONE (1.94%) and CONT (1.78%) diets (Table 3). Thus, the MOMY and MOVI showed a positive synergism in carcass chilling losses. The reduction in chilling losses of the carcasses of the bulls fed MOVI diet was 31.9% lower when compared to the chilling losses of bulls fed CONT diet. The reduction of chilling losses of bulls fed MOMY diet compared to bulls fed CONT diet chilling losses was 27.1%. The combination of monensin + virginiamycin or monensin + mineral trace and yeast possibly reduced chilling losses in the first 24 hours after slaughter because of a greater backfat thickness (Table 4).
Table 4
Nutrients apparent digestibility of beef cattle finished in feedlot and fed high-grain diets with monensin, virginiamycin and micro minerals mixture and yeast
Parameters | | | Diets | | | |
CONT1 | MONE2 | MOVI3 | MOMY4 | SME5 | P-value |
Dry matter | 75.29b | 74.41b | 78.97a | 78.37a | 2.14 | 0.009 |
Organic matter | 74.90b | 74.11b | 78.56a | 78.01a | 1.78 | 0.011 |
Crude protein | 72.58 | 71.11 | 76.58 | 74.56 | 1.91 | 0.231 |
Ether extract | 71.42b | 77.95a | 76.77a | 81.09a | 5.30 | 0.023 |
Neutral detergent fiber | 58.51b | 56.04b | 61.00a | 59.6ab | 3.40 | 0.032 |
Total carbohydrates | 75.30b | 74.42b | 78.98a | 78.38a | 4.30 | 0.028 |
Total digestible nutrients | 72.81b | 72.04b | 75.50a | 74.80a | 4.25 | 0.013 |
1CONT – without additives; 2MONE – inclusion of 30 mg/kg of monensin (DM basis); 3MOVI – inclusion of 30 mg/kg of monensin (DM basis) + 30 mg/kg of virginiamycin (DM basis); 4MOMY – inclusion of 30 mg/kg of monensin (DM basis) + 3 g/kg of BW of minerals traces and yeast; 5Standard means error. Means followed by different letters differ. |
The inclusion of MONE or MOMY resulted in lower (P < 0.05) liver weight (5.53 and 5.42 kg, respectively) when compared to the liver from bulls fed CONT (6.46 kg) and MOVI (6.48 kg) diets. The inclusion of virginiamycin in the diet (diet MOVI) did not change the liver weight compared to the weight of bulls fed the CONT diet. However, there was no abscess in the liver of bulls from any of the diets. Monensin did not affect liver abscess incidence, while tylosin reduced abscess incidence from 27 to 9% (Potter et al., 1985), while virginiamycin may help to stabilize feed intake and prevent liver abscesses in bovine fed on high-grain diets (Rogers et al., 1995).
Digestibility assay
The apparent digestibility of DM, OM, NDF, and total carbohydrates was higher (P < 0.05) for bulls fed MOVI and MOMY diets when compared to bulls fed CONT and MONE diets (Table 4). No difference (P > 0.05) was observed in apparent digestibility of DM, OM, NDF, and total carbohydrates between bulls fed CONT and MONE diets or between bulls fed MOVI and MOMY diets, respectively (Table 4). The apparent digestibility of ether extract was higher (P < 0.05) for bulls receiving diets with additives in comparison with bulls fed the CONT diet. The apparent digestibility of ether extract was similar (P > 0.05) for bulls fed MONE, MOVI, and MOMY diets (Table 4). On the other hand, the apparent digestibility of crude protein was similar (P > 0.023) among bulls fed four diets (Table 4). Total digestible nutrients concentration was higher (P < 0.05) in the MOVI and MOMY diets in comparison to CONT and MONE diets (Table 4). However, total digestible nutrient concentration was similar (P > 0.05) between CONT and MONE and between MOVI and MOMY diets (Table 4). Thus, the addition of an ionophore mix (monensin) + an antibiotic (virginiamycin) and a mix of ionophores (monensin) + mineral trace and yeast improved the digestibility when compared to a diet without additives.
The inclusion of monensin and/or virginiamycin does not usually alter the apparent digestibility of nutrients (Fonseca et al., 2016; Jesus et al., 2016; Montano et al., 2015; Vendramini et al., 2016). Few studies have obtained positive effects of ionophores inclusion in diets on nutrient digestibility, as observed in this study. In the test performed by (Goodrich & Thompson, 1980), greater digestibility of dry matter (72%) and crude protein (62%) was observed for animals fed with monensin inclusion in the diet.
Animal behavior
The addition of monensin alone or in combination with virginiamycin or mineral trace and yeast in the diet had a significant effect (P < 0.05) on animal behavior during feedlot finishing (Table 5).
Table 5
Behavior of beef cattle finished in feedlot and fed high-grain diets with monensin, virginiamycin and micro minerals mixture and yeast
Parameters | | | Diets | | | |
| CONT1 | MONE2 | MOVI3 | MOMY4 | SME5 | P-value |
Drinking, min | 37.8a | 29.4b | 34.4ab | 23.3b | 2.31 | 0.041 |
Feeding, min | 151.7b | 173.3a | 170.6a | 164.4a | 7.22 | 0.035 |
Ruminating, min | 247.8b | 233.9b | 260.0a | 300.6a | 14.14 | 0.034 |
Idle, min | 1002.7a | 1003.4a | 975.0b | 951.7b | 34.71 | 0.035 |
1CONT – without additives; 2MONE – inclusion of 30 mg/kg of monensin (DM basis); 3MOVI – inclusion of 30 mg/kg of monensin (DM basis) + 30 mg/kg of virginiamycin (DM basis); 4MOMY – inclusion of 30 mg/kg of monensin (DM basis) + 3 g/kg of BW of minerals traces and yeast; 5Standard means error. Means followed by different letters differ. |
The water ingestion time was longer (P < 0.05) for bulls fed CONT (37.8 min) and MOVI (34.4 min) diets and shorter for those fed MONE (29.4 min) and MOMY (23.3 min) diets (Table 5). Water ingestion can be affected by DMI, diet ingredients, temperature, and the animal physiological state.
However, the period of feeding intake time was similar (P > 0.05) for bulls fed MONE (173.3 min), MOVI (170.6 min), and MOMY (164.4 min) diets and shorter (P < 0.05) for bulls fed CONT (151.7 min) diet. Thus, the inclusion of additives in the diets increased the time spent on feeding but did not increase the total DMI (Tables 2 and 5). The feeding time of bulls finished in the feedlot varies from 200 minutes per day or more (Eiras et al., 2014; Farias et al., 2012; Ornaghi et al., 2017; Silva et al., 2014). However, in this study, the feeding time was low (165 min/1440 min) because the diet had a high concentrate:corn silage ratio. The total feeding intake (concentrates + corn silage) time can be affected by the amount, physical form, fiber content, and additives included in the diets (Eiras et al., 2014; Silva et al., 2014; Silva et al., 2010).
The rumination time of bulls finished in the feedlot varies from 400 to 600 minutes per day (Eiras et al., 2014; Silva et al., 2014; Silva et al., 2010). The rumination period was similar (P < 0.05) between bulls fed MOMY (300.6 min) and MOVI (260.0 min) diets; with both groups spending more time ruminating compared to bulls fed CONT (247.8 min) and MONE (247.8 min) diets (Table 5). The high-grain ratio negatively affects the production of saliva flow due low fiber content and consequently reduces rumination time.
The idle period was longer (P < 0.05) for bulls fed CONT (1002.7 min) and MONE (1003.4 min) treatments and shorter for bulls fed MOVI (975.0 min) and MOMY (951.7 min) treatments (Table 5). The idle time can affect animal performance since energy is expended for activities such as locomotion. In this work the idle time observed was normal (983.3/1.440 min) for bulls finished in a feedlot and fed high-grains diets (Eiras et al., 2017; Eiras et al., 2014; Ornaghi et al., 2017).
Meat characteristics
The backfat thickness was greater (P < 0.05) for bulls fed MOVI (4.98 mm) and MOMY (4.87 mm) compared to the backfat thickness for bulls fed MONE (3.69 mm) and CONT (3.27 mm) diets (Table 6). The average backfat thickness of carcasses from bulls fed MOVI and MOMY diets (4.93 mm) was 33.6% greater than those from bulls fed MONE diet and 50.8% from bulls fed CONT diet. Thus, the inclusion of monensin + virginiamycin or monensin + trace mineral and yeast had a positive synergistic effect on carcass backfat thickness.
Table 6
Meat characteristics of beef cattle finished in feedlot and fed high-grain diets with monensin, virginiamycin and micro minerals mixture and yeast
Characteristics | | | Diets | | | |
| CONT1 | MONE2 | MOVI3 | MOMY4 | SME5 | P-value |
Backfat thickness, mm | 3.27b | 3.69b | 4.98a | 4.87a | 0.244 | 0.022 |
Marbling, from 1 to 3 scale | 1.50b | 1.50b | 1.60b | 1.83a | 0.144 | 0.032 |
Longissimus muscle area, cm2 | 75.83c | 75.83c | 79.17b | 86.67a | 2.24 | 0.025 |
Ratio6 | 0.48c | 0.52b | 0.53b | 0.58a | 0.017 | 0.022 |
Muscle, % | 60.02a | 55.21b | 55.19b | 57.42ab | 2.65 | 0.044 |
Fat, % | 20.99b | 23.38a | 24.95a | 24.25a | 4.84 | 0.043 |
Bone, % | 16.10 | 18.59 | 17.75 | 16.02 | 2.65 | 0.122 |
Others7, % | 2.89 | 2.82 | 2.19 | 2.32 | 0.24 | 0.255 |
1CONT – without additives; 2MONE – inclusion of 30 mg/kg of monensin (DM basis); 3MOVI – inclusion of 30 mg/kg of monensin (DM basis) + 30 mg/kg of virginiamycin (DM basis); 4MOMY – inclusion of 30 mg/kg of monensin (DM basis) + 3 g/kg of BW of minerals traces and yeast; 5Standard means error. 6Ratio between muscle width and muscle length. 7Lymph + fasciae + blood + water vapor. Means followed by different letters differ. |
Marbling was higher (P < 0.05) for meat from bulls fed MOMY diet (1.83 points) when compared to meat from bulls fed CONT (1.50 points), MONE (1.50 points) and MOVI (1.60 points) diets (Table 6). Possibly, the energy surplus in the MOMY treatment was used for fat deposition, which favors meat with improved quality.
The LMA area was greater (P = 0.025) for bulls fed MOMY (86.67 cm2) diet compared to those fed MOVI (79.17 cm2), MONE (75.85 cm2), and CONT (75.83 cm2) diets (Table 6). Muscle area was larger (P = 0.025) for bulls fed MOVI diet compared to those fed MONE and CONT diets. The MA was similar (P > 0.05) between bulls from CONT and MONE diets.
The ratio between the muscle width and muscle length of the LMA at the 12th rib was greater (P = 0.022) for bulls fed MOMY (0.58), intermediate for bulls fed MOVI (0.53) and MONE (0.52), and lower for bulls fed CONT diets. Meat with a high ratio between width and length is better evaluated and desired by consumers. The ratio between the width and length of Longissimus, in bulls very well evaluated on meat quality score, is close to 0.50 (Rivaroli et al., 2017). Thus, the inclusion of monensin + mineral trace and yeast provides meat that is likely to be preferred by consumers.
The muscle percentage was greater (P < 0.05) in meat from bulls fed CONT diet (60.0%) compared to those fed MONE (55.2%) and MOVI (55.2%), but similar (P > 0.05) in the meat from bulls fed MO + AD (57.4%) diet (Table 6). However, the muscle percentage in meat for bulls fed MONE, MOVI and MOMY diets were similar (P > 0.05). On the other hand, the fat percentage was lower (P = 0.043) in the meat from bulls fed CONT diet (21.0%) compared to the other treatments (Table 6). The muscle percentage varied from 55 to 60% and the fat percentage varied from 20 to 25%. The percentage of bone was similar for all the treatments (P > 0.05). Under similar conditions of feedlot time, feeding, and management, the percentages of muscle, fat, and bone in the carcass of European vs. Zebu cattle range from 55 to 65%, 16 to 24%, and 15 to 18% (Ornaghi et al., 2017; Prado et al., 2015; Prado et al., 2015; Rivaroli et al., 2017; Souza et al., 2019; Valero et al., 2015) Slaughtered animals with higher weights (over 550 kg) typically have higher fat percentages and lower muscle percentages, and bone percentages are always more constant (Prado et al., 2015; Prado et al., 2015; Souza et al., 2019). The deposition of fat in the animal's body occurs mainly in the final period of termination, therefore, in heavier animals.