Two experiments were conducted to evaluate the performance responses of finishing feedlot cattle to dietary addition of essential oils and exogenous enzymes. The treatments in each experiment consisted of (DM basis): MONsodium monensin (26 mg/kg); BEO-a blend of essential oils (90 mg/kg); BEO+MON-a blend of essential oils plus monensin (90 mg/kg + 26 mg/ kg, respectively); BEO+AM-a blend of essential oils plus exogenous α-amylase (90 mg/kg + 560 mg/kg, respectively); and BEO+AM+PRO-a blend of essential oils plus exogenous α-amylase and exogenous protease (90 mg/kg + 560 mg/kg + 840 mg/kg, respectively). Exp. 1 consisted of a 93-d finishing period using 300 Nellore bulls in a randomized complete block design. Animals fed BEO had higher DMI (P < 0.001) but similar feed efficiency to animals fed MON (P ≥ 0.98). Compared with MON, the combination of BEO+AM resulted in 810 g greater DMI (P = 0.001), 190 g greater average daily gain (P = 0.04), 18 kg heavier final body weight (P = 0.04), and 12 kg heavier hot carcass weight (P = 0.02), although feed efficiency was not significantly different between BEO+AM and MON (P = 0.89). Combining BEO+MON tended to decrease hot carcass weight compared with BEO alone (P = 0.08) but not compared with MON (P = 0.98). Treatments did not impact observed dietary net energy values (P ≥ 0.74) or the observed:expected net energy ratio (P ≥ 0.11). In Exp. 2, five ruminally cannulated Nellore steers were used to evaluate intake, apparent total tract digestibility of nutrients, and ruminal parameters in a 5 × 5 Latin square design. Feeding BEO increased the total tract digestibility of CP compared to MON (P = 0.03). Compared to MON, feeding the combination of BEO+MON increased the intake of CP (P = 0.04) and NDF (P = 0.05), with no effects on total tract digestibility of nutrients (P ≥ 0.56), except for a tendency (P = 0.09) to increase CP digestibility. Intakes of all nutrients measured, except for ether extract (P = 0.16) were greater in animals fed BEO+AM when compared with MON (P ≤ 0.03), with no differences on total tract nutrient digestibilities (P ≥ 0.11) between these two treatments. In summary, diets containing the BEO used herein enhanced DMI of growing-finishing feedlot cattle compared with a basal diet containing MON without impair feed efficiency. A synergism between BEO and AM was detected, further increasing cattle performance and carcass production compared to MON.

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The current study evaluated growth performance and digestion responses of finishing bulls fed diets containing 825 g/kg flint maize [dry matter (DM) basis] ground to medium (1.66 mm; MG) or coarse particle sizes (2.12 mm; CG), with added monensin (26 mg/kg; DM basis; MON) or a blend of essential oils (BEO) + exogenous α-amylase (AM; 90 mg/kg + 560 mg/kg commercial product, respectively, DM basis). In Expt 1, 256 Nellore bulls were blocked by initial body weight (BW) (360 ± 11.7 kg) and assigned to 48 pens in a 2 × 2 factorial arrangement of treatments. Effect of a maize particle size × feed additive interaction was not detected for final BW, DM intake (DMI), average daily gain (ADG) and feed efficiency. The DMI was greater for bulls fed BEO + AM v. MON. Final BW and ADG tended to be greater for bulls fed CG than MG maize. An interaction was detected for hot carcass weight which was 11 kg heavier for bulls fed BEO + AM v. MON in diets containing CG, but not MG particle size. In Expt 2, four ruminally cannulated Nellore steers were offered the same treatments as Expt 1, in a 4 × 4 Latin Square design. Intake of most nutrients was greater for steers fed CG than steers fed MG maize. In summary, feeding bulls CG maize increased growth performance and carcass characteristics compared with MG. The combination of BEO + AM resulted in heavier carcass weights compared with MON supplementation when included in diets containing CG maize.

The aim of this study was to compare the length and intensity of oestrus in nonlactating Bos taurus (Holstein; n = 11) v. nonlactating Bos indicus (Nelore; n = 13) cows. The cows were kept in a single pen to allow interaction between them and were daily fed a maintenance diet according to the NRC (2000), containing 42.8% sugarcane bagasse, 45.7% corn, 3.2% soybean meal, 1.2% urea, 5.7% molasses, and 1.4% mineral salt, totaling 71% dry matter (DM) in the diet. The intake of DM per kg of body weight (BW) was 1.45%. Body condition score and BW were 3.5 ± 0.1 and 3.0 ± 0.2 (range 1 to 5), and 549.5 ± 14.3 and 625.5 ± 20.5 kg for Nelore and Holstein cows, respectively. All females had the emergence of follicular wave synchronized with an intravaginal progesterone device (Sincrogest, Ourofino Agronegócio, São Paulo, Brazil), 2 mg of oestradiol benzoate (Sincrodiol, Ourofino; IM) and 0.150 mg PGF2α (Sincrocio, Ourofino; IM). Ten days after initiation of the protocol, the intravaginal device was removed and another treatment with 0.150 mg PGF2α was given. Thereafter, cows were evaluated for oestrus by continuous visual observation 24 h a day for 5 days. The number of the cow that was mounting and the number of the cow that was standing was recorded for each event, as well as the time of the event. To confirm ovulation, ultrasound examination was performed between 5 and 7 days after oestrus detection. Data were analysed by Student’s t-test and Fisher’s exact test or Chi-square and data are presented as mean ± SE or percentage. Ten of 13 (76.9%) and 11 of 11 (100%) Nelore and Holstein cows, respectively, were detected in standing oestrus and ovulated (P > 0.10). On average, Holstein cows tended to start oestrus earlier than Nelore cows after device removal (40.4 ± 2.9 v. 47.7 ± 2.8 h; P = 0.09). There was no difference in intensity and duration of oestrus between Bos taurus and Bos indicus cows. Oestrus length was 14.7 ± 1.0 h (range 8.3 to 19.0 h) in Holstein cows and 12.4 ± 0.8 h (range 8.6 to 17.1 h) in Nelore cows (P > 0.10). Moreover, the average number of times that cows accepted mounts was 32.2 ± 6.1 and 36.3 ± 5.3 for Holstein and Nelore cows, respectively (P > 0.10). Only 9.1% of the mounts accepted by Nelore cows were performed by Holstein cows and only 3.8% of the mounts accepted by Holstein cows were done by Nelore cows (P < 0.05). We concluded that Bos taurus and Bos indicus cows managed under similar environment and nutritional conditions exhibit oestrus with the same intensity and duration. However, there was very little interaction during oestrus between Nelore and Holstein cows, showing a breed segregation pattern. This work was financially supported by CNPq, FAPESP, and Ourofino Agronegócio of Brazil.

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The objective of this study was to evaluate the growth performance and carcass traits of finishing bulls fed diets containing, on dietary dry matter basis, different levels of corn wet distillers bran plus solubles (WDBS; 0, 15, 30 or 45%) added with or without corn oil (CO; 0 and 3%). A total of 205 Nellore bulls (390 ± 25 kg initial BW) were blocked by initial body weight, distributed in 40 pens and pens within weight block were randomly assigned to treatments in a 2 × 4 factorial arrangement. Diets were isonitrogenous and contained 8.5% sugarcane bagasse and 91.5% concentrate (ground corn, soybean meal, pelleted citrus pulp, urea, mineral). The WDBS (FlexyDDG®) and the corn oil were from SJC Bioenergia (Quirinópolis, Goiás, Brazil). Data were analyzed using the PROC MIXED procedure of SAS. An interaction between CO × WDBS levels was observed for dry matter intake (DMI; P = 0.032). In diets without CO, increasing levels of WDBS linearly (P = 0.004) reduced the DMI, but in diets containing 3% CO, increasing levels of WDBS quadraticaly affected the DMI (P = 0.002). No effects of CO, WDBSF levels or CO × WDBS levels were observed for final body weight, average daily gain, hot carcass weight and dressing percentage. Feed efficiency tended (P = 0.07) to be greater for bulls fed diets containing CO (0.154 vs. 0.144). Increasing levels of WDBS tended (P = 0.09) to increase the feed efficiency. In summary, increasing levels of WDBS in finishing diets linearly (in diets without CO) or quadratically (in diets with CO) reduces the dry matter intake. Adding CO and WDBS tend to increase feed efficiency.