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<p>O objetivo foi avaliar a substituição dos níveis de proteína do farelo de soja pela proteína do farelo de algodão (FA) de alta energia em suplementos múltiplos para bovinos de corte em pastejo no período seco do ano sobre o ganho médio diário (GMD) e viabilidade econômica. Foram utilizados 20 novilhos Nelores com peso médio inicial de 351,25±35,38 kg e idade média de 24±0,8 meses, distribuídos em quatro piquetes de <em>Brachiaria brizantha </em>cv. Marandu com 1,6 ha cada em delineamento inteiramente casualizado com quatro suplementos e cinco animais para avaliar os seguintes suplementos: 0FA, 25FA e 50FA correspondentes ao nível de 0, 25 e 50% de farelo de algodão de alta energia em substituição ao farelo de soja, fornecidos na quantidade de 2 kg/animal/dia, além do suplemento exclusivo com mistura mineral <em>ad libitum </em>(MM). Verificou-se maior ganho de peso médio diário (GMD) (P&lt;0,0001) para animais recebendo suplementação concentrada (0,62 kg/animal/dia) em comparação aqueles do grupo controle (-0,020 kg/animal/dia). O suplemento 25FA proporcionou maior (P&lt;0,0001) GMD (0,75kg/ animal/dia-1) em relação ao suplemento 50FA (0,60kg/animal/dia-1). O GMD dos animais suplementados com 0FA (0,53kg/animal/dia-1) não diferiu (P&gt;0,0001) do GMD dos novilhos que receberam suplemento com 25FA (0,75kg/animal/dia-1) e com 50FA (0,60kg/animal/dia-1). O suplemento 25FA apresentou maior retorno econômico sobre o capital investido no período. A utilização de farelo de algodão de alta energia em nível de substituição de 25% do farelo de soja em suplementos múltiplos proporcionou maior ganho de peso de bovinos e melhor viabilidade econômica.</p>

The objective of this study was to evaluate the effects of tannins versus Monensin on in vitro ruminal fermentation of a feedlot diet. The treatments were: control (no additives); low tannin (2 mg g DM-1); medium tannin (4 mg g DM-1), high tannin (6 mg g DM-1), and Monensin (0.02 mg g DM-1). The substrate was a feedlot diet composed by hay and concentrate (15:85 w/w; DM basis). Ruminal fluid was obtained from three rumen-cannulated male Santa Inês sheep. In vitro incubations were carried out during four consecutive weeks (run). Gas production (GP) was recorded at 1, 2, 3, 4, 5, 6, 8, 10, 12, 18, 24, 30, 36, 42, 48, 60, 72, 84, and 96 h of incubation. At 48 and 96 h, two bottles per treatment were withdrawn to measure pH, ammonia concentration (NH3), volatile fatty acid (VFA), in vitro dry matter digestibility (IVDMD), and in vitro neutral detergent fiber digestibility (IVNDFD). Addition of tannin or Monensin did not affect (P > 0.05) the kinetics parameters. Tannin supplementation reduced (P < 0.05) the GP at 24 h compared to Monensin. Addition of Monensin decreased (P < 0.05) IVDMD at 96 h and IVNDFD at 48 and 96 h compared to the control. The IVNDFD was lower (P < 0.05) with Monensin than with tannin at 48 and 96 h. The NH3 was lower (P < 0.05) with tannin compared with Monensin. By increasing tannin dosage, NH3 levels changed quadratically (P < 0.05). The inclusion of tannin in vitro reduced the NH3 concentration considerably when used in low dose.

The objective was to evaluate performance and economic viability of protein supplementation of grazing beef cattle in the wet and dry-wet transition season. Eighty non-castrated Nellore steers, body weight of 371 ± 11.3 kg were used in the experiment. The treatments were the following: SM – Mineral supplement; Protein mineral supplements (SMP 20% FS - soybean meal: 410 g/animal; SMP 40% UR - urea: 223 g/animal; and SMP 40% UP - protect urea: 236 g/animal). It was used a complete random design with 20 replicates per treatment. There was a difference in the results (P<0.05) of PMS 40% UP compared with SM, with average daily gain (ADG) of 1.06 kg/animal for SMP 40% UP and 0.95 kg/ animal for SM, respectively. There was difference (P<0.10) in the fat accumulation rate in longissimus dorsi muscle (Tx.EGLD) between treatments. The PMS 40% UP supplement showed an accumulation of fat 0.018 mm/day while the SMP 40% UR had a lower rate of fat 0.011 mm/day. There was no effect (P> 0.10) of treatments on the rate of accumulation of fat in the rump region. All treatments presented a positive net margin. The best net margin was observed for treatment PMS 40% UP, that is, R$123.92 per animal/period, whereas the smallest was observed in treatment PMS 20% FS, that is, R$98.91 per animal/period. Protein supplementation with a source of protected nitrogen can be used as a strategy to increase the performance of beef cattle on pasture of Brachiaria brizantha cv. Xaraés during the wet and dry-wet transition.

The objective of this study was to evaluate the effects of the daily supplementation with a low dosage of a blend of condensed and hydrolysable tannins on the in vitro and in situ digestibility of protein and fibrous feedstuffs. In situ ruminal incubation assays were conducted on seven protein and five roughage feedstuffs with and without tannin supplementation (1 g/kg DM intake). From these same cattle, rumen fluid was collected for in vitro incubations of the same feedstuffs. In vitro assays we evaluated the gas production (GP) up to 24 h and, sequentially, digestibility of dry matter (IVDMD), crude protein (IVCPD), fiber (IVNDFD), and ammonia nitrogen (NH3-N). For in situ assays, the disappearance curves were modeled and then the potentially degradable (), digestion rate (), and undegradable () fractions were estimated. Of all the variables studied, only IVCPD of soybean meal showed effect (P<0.05) with the addition of dose of tannins. The supplementation of tannin affected only of the DM and CP of the cottonseed meal. The of DM and CP increased with the supplementation of the tannin blend only for Marandu (dry season), soybean and cottonseed meal. Additionally, the of the DM of corn silage was reduced. The of CP was affected by the increase of tannin supplementation for soybean and cottonseed meal. Daily supplementation with a low dose of tannin blend for grazing cattle affects for grazing cattle affects the ruminal digestibility of some of the evaluated feedstuffs, which are soybean and cottonseed meal.
The objective of this study was to evaluate the effects of the daily supplementation with a low dosage of a blend of condensed and hydrolysable tannins on the in vitro and in situ digestibility of protein and fibrous feedstuffs. In situ ruminal incubation assays were conducted on seven protein and five roughage feedstuffs with and without tannin supplementation (1 g/kg DM intake). From these same cattle, rumen fluid was collected for in vitro incubations of the same feedstuffs. In vitro assays we evaluated the gas production (GP) up to 24 h and, sequentially, digestibility of dry matter (IVDMD), crude protein (IVCPD), fiber (IVNDFD), and ammonia nitrogen (NH3-N). For in situ assays, the disappearance curves were modeled and then the potentially degradable (), digestion rate (), and undegradable () fractions were estimated. Of all the variables studied, only IVCPD of soybean meal showed effect (P<0.05) with the addition of dose of tannins. The supplementation of tannin affected only of the DM and CP of the cottonseed meal. The of DM and CP increased with the supplementation of the tannin blend only for Marandu (dry season), soybean and cottonseed meal. Additionally, the of the DM of corn silage was reduced. The of CP was affected by the increase of tannin supplementation for soybean and cottonseed meal. Daily supplementation with a low dose of tannin blend for grazing cattle affects for grazing cattle affects the ruminal digestibility of some of the evaluated feedstuffs, which are soybean and cottonseed meal.

This study was designed to evaluate the effects of different supplementation plans on the nutrient intake, apparent total-tract digestibility, grazing behavior, growth performance, and carcass characteristics of beef cattle under grazing conditions from ages 4 to 18 months old. The beef calves grazed Brachiaria decumbens in four seasons: rainy-dry transition, dry, dry-rainy transition, and rainy. Forty-four animals (11 per treatment) were randomly assigned to one of four nutritional plans of supplementation defined by the quantity of supplement offered: control, low, medium, and high supplementation. There was no difference (P > 0.10) in dry matter intake (DMI). However, animals receiving medium and high supplementation had decreased (P < 0.10) forage dry matter intake (FDMI) compared with those under non- and low supplementation. The DMI and FDMI were lower (P < 0.10) in the dry season. During the rainy season, the grazing time decreased (P < 0.10) for animals receiving supplementation compared with non-supplemented ones, but was similar between medium and high supplementation. The performance and carcass characteristics were greater (P < 0.10) for high and medium supplementation compared with low and control. In conclusion, increasing the supplementation plans for beef cattle in tropical pastures increases the nutrient intake but decreases FDMI. The performance also increases with the supplementation plan; however, the growth rate is affected by the grazing season.

The effects of increasing doses of three exogenous enzymes preparations with fibrolytic activity (FIB - 0, 0.6, 1.2, 1.8, and 2.4 mg mL-1liquid volume incubated), amylolytic activity (AMZ - 0, 0.05, 0.10, 0.15, and 0.20 mg mL-1liquid volume incubated), and proteolytic activity (PRO - 0, 0.05, 0.10, 0.15, and 0.20 mg mL-1 liquid volume incubated ) on gas production (GP), kinetic parameters, and fermentation profile of Brachiaria brizantha cv. Marandu were evaluated using the in vitro gas production technique. Ruminal liquid was obtained from two rumen-cannulated Santa Inês sheep maintained on pasture. Accumulated gas production was measured during 96 hours of incubation, measured at 18 different time points. The determined parameters were pH, asymptotic gas production (mL g-1), rate of gas production (h-1), lag time (h), organic matter digestibility (OMD, g g-1 DM), metabolizable energy (ME, MJ kg-1 DM), and neutral detergent fiber digestibility (NDFD, mg g-1 DM). Increasing the FIB dose linearly increased (P < 0.05) the asymptotic gas production. However, the rate of gas production and the lag time showed linear decreases (P < 0.05). Addition of FIB also linearly increased (P < 0.05) the GP at all incubation times, as well as the OMD, NDFD and ME. Addition of AMZ linearly increased (P < 0.05) the asymptotic gas production, but GP linear increased (P < 0.05) only at the 6-hour and 12-hour time points. The rate of gas production and the lag time decreased linearly (P < 0.05) in response to increasing AMZ addition. Inclusion of PRO did not affect (P > 0.05) asymptotic gas production, but there was quadratic effect (P < 0.05) on the rate of gas production, the lag time, and the GP at the 6-hour and 12-hour time points. The OMD, NDFD and ME were not affected by PRO addition. Thus, fibrolytic, amylolytic and proteolytic enzymes are effective in reducing the lag time and increasing the in vitro gas production from Brachiaria Brizantha cv. Marandu forage, and fibrolytic enzymes improve the in vitro fermentation profile.

The study was carried out in a greenhouse with a 4X4 factorial arrangement randomized block design in order to evaluate the effects of nitrogen rates (0, 50, 100 and 150 mg dm-3) associated with cutting heights (10, 15, 20 and 25 cm) on dry matter production and the chemical composition of Massai grass. The seeding was done in pots with 11 kg of soil. 10 plants were kept per pot, and there were two cuts every 35 days. Nitrogen fertilization was split between the two cuts, where the first N application occurred after the uniformity cut and the second after the first cut. In each cut the plants were separated and weighed for botanical component evaluation: leaf blade and stem + sheath. After this, the samples were homogenized and analysed for dry matter (DM), crude protein (CP) and neutral detergent fibre (NDF) content. In the first cut, the N fertilization caused a linear increase in DM production of 0.058 g pot-1 per each 1 mg dm-3 of N applied, as well as causing an increase of 0.549% in CP percentage, a 0.0124 pot-1 g increase in CP production and a reduction of 0.055% in NDF. In the second cut, N rates promoted a quadratic effect on DM production. A maximum DM production of 16.48 g pot-1 with 107.27 mg dm-3 of N was observed while CP production content was increased by 0.0092 g pot-1 for each 1 mg dm-3 N applied. In terms of linear responses to DM and PB, as well as the use efficiency calculated for Massai grass, recommended N doses range between 50 and 100 g dm-3.

Diets composed of whole flint corn grain (WCG) without any roughage source are often used in South American countries. The primary source of protein in theses diets is soybean meal. We hypothesized that the combination of different protein sources improves ruminal fermentation and nutrient digestibility. This study was carried out to assess the impacts of replacing 50% of the soybean meal by other protein sources on voluntary dry matter intake (DMI), digestibility, efficiency of N utilization, efficiency of grain use, metabolic characteristics, and ingestive behavior of Nellore cattle fed WCG diets. Five rumen-cannulated Nellore Bulls (average BW = 651.6 ± 31.83 kg) were used in a 5 x 5 Latin square design, randomly assigned to five diets consisting of 85% of WCG and 15% of pellet supplement with combination of different protein sources: SM - pellet supplement with soybean meal only; CM - soybean meal and cottonseed meal; SFM - soybean meal and sunflower meal; DDG - soybean meal and DDG; DDGS - soybean meal and DDGS. The replacement of 50% of soybean meal by DDG increased (P<0.05) DMI and organic matter intake (OMI), both DMI and OMI were lower with CM. Digestibility, ruminal pH (mean = 5.7), efficiency of N utilization, and diurnal ingestive behavior were not affected (P>0.05) by protein sources. Protein sources also did not affect the grain-use efficiency (P>0.05), with an average value of 96.6% and only 3.4% of the corn grains recovered in the feces. The concentration of GGT enzyme was greatest (P<0.05) for CM and DDGS. The inclusion of DDG increased the DMI but did not improve the nutrients' digestibility or N metabolism. The results suggest that 50% of the [1]soybean meal can be replaced by sunflower meal, DDG, and DDGS without affecting the nutritional and metabolic parameters of Nellore cattle fed whole flint corn grain diets, providing opportunities for reducing costs in feedlot systems.