RESUMO -Avaliaram-se o consumo e as digestibilidades aparentes totais dos nutrientes e o ganho de peso de bovinos de corte recebendo dietas contendo concentrado e silagem de Brachiaria brizantha cv. Marandu nas seguintes proporções: 20:80, 35:65, 50:50 e 65:35, com base na matéria seca. Foram utilizados vinte e quatro animais castrados Holandês x Zebu, com peso vivo inicial médio de 364 kg, distribuídos em um delineamento em blocos casualizados. Por ocasião da ensilagem, procedeu-se o tratamento do capim com o inoculante enzimo-bacteriano Nutroeste 50 t. Para o cálculo da matéria seca fecal, utilizou-se a fibra em detergente ácido indigestível (FDAI) como indicador. Os animais foram alojados em baias individuais e alimentados ad libitum. O ensaio teve duração de 84 dias, divididos em três períodos de 28 dias após 15 dias de adaptação. Os consumos médios de matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE) e carboidratos totais (CHO) e as digestibilidades aparentes totais de MS, MO, CHO e carboidratos não-fibrosos (CNF) elevaram linearmente com o aumento dos níveis de concentrado nas dietas. Comportamento semelhante foi observado para o ganho de peso médio diário, estimando-se incrementos de 0,0184 kg/unidade de concentrado adicionado. Contudo, as digestibilidades aparentes de PB, EE e fibra em detergente neutro (FDN) não foram influenciadas pelas dietas, registrando-se, respectivamente, valores médios de 77, 88 e 60%. Silagem de Brachiaria brizantha não-emurchecida, constituindo 50% da dieta de bovinos H x Z, promoveu ganhos de peso em torno de 1,0 kg/dia. Palavras-chave: confinamento, desempenho, matéria seca, proteína bruta, silagem de capim Intake and Apparent Digestibility of the Nutrients and Weight Gain of Beef Cattle Fed Diets with Different Proportions of Brachiaria brizantha Silage and ConcentrateABSTRACT -Intake and total apparent digestibilities of the nutrients and average daily gains (ADG) by beef cattle fed diets based on concentrate and Brachiaria brizantha cv. Marandu silage in the following proportions: 20:80, 35:65, 50:50 and 65:35, in dry matter basis were evaluated. Twenty-four crossbred (Holstein x Zebu) steers, with initial live weight of 364 kg were allotted to a randomized blocks design. At the ensiling process, an enzyme-bacterial inoculant Nutroeste 50 t was applied to the forage. For the determination of fecal dry matter, indigestible acid detergent fiber was used as a marker. The animals were housed in individual pens and fed ad libitum. The experiment lasted 84 days, divided in three periods of 28 days after 15 days of adaptation. The dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE) and total carbohydrates (CHO) average intakes increased linearly with the increment of the concentrate in the diets. The total apparent digestibility of DM, OM, CHO and non fiber carbohydrates also increased linearly with the increment of the concentrate levels in the diets. Similar behavior was observed for ADG, with increments of 0.0184 kg/uni...

Avaliaram-se os índices de crescimento taxa de crescimento relativo (TCR), taxa assimilatória líquida (TAL), razão de área foliar (RAF), índice de área foliar (IAF) e a interceptação luminosa do capim-elefante 'Napier' após pastejo. O trabalho consistiu de dois experimentos, com quatro tratamentos de adubação de N e K, em kg/ha (T1: 100 kg de N e 80 kg de K, T2: 200 kg de N e 160 kg de K, T3: 300 kg de N e 240 kg de K e T4: 400 kg de N e 320 kg de K), sendo um irrigado e outro sem irrigação, segundo o delineamento de blocos ao acaso com três repetições. A análise estatística observou um esquema de parcela subdividida, tendo nas parcelas as doses de N e K e nas sub-parcelas as idades de rebrotação após pastejo (2, 8, 15, 45 e 123 dias), para IAF e interceptação de luz. O IAF na área irrigada aumentou de 0,28 para 8,27, média dos quatro tratamentos de N e K, entre a menor e maior idade de rebrotação. Na área não irrigada, também ocorreu um aumento no IAF, embora de menor magnitude que na área irrigada, de 0,16 para 7,76. Os valores médios de TCR, TAL e RAF foram 0,0083 g/g.dia, 3,57 g/cm².dia e 0,0021 m²/g, respectivamente. A interceptação de luz aumentou com o aumento do IAF, estabilizando-se no 51,5º dia. Já a penetração de luz no interior do dossel diminuiu assintoticamente em função do IAF. O coeficiente de extinção variou de 0,29 na maior combinação de N e K, para 0,53 nas doses de 200 kg/ha de N e 160 kg/ha de K.

Adoption of silvopasture is increasing, but proper design and management of pasture–tree associations is required to sustain pasture productivity. Our objective was to compare agronomic and physiological characteristics of Brachiaria brizantha (Hochst. Ex A.Rich.) Stapf. (palisade grass) cv. Marandu growing in monoculture, or in silvopasture with Eucalyptus urograndis, in the Brazilian Amazon biome. Trees were planted in triple rows (intra-row spacing 3 m, inter-row spacing 3.5 m), referred to as a grove, with three groves per 2-ha silvopasture experimental unit. Space between groves was 30 m, and tree density was 270 ha–1. From October 2015 to September 2016, all experimental units were stocked continuously with cattle by using a variable stocking rate to maintain a Marandu canopy height of 30 cm. In the silvopasture, sampling occurred at 4, 7.5 and 15 m into the non-treed area from the outer tree row in a grove. Photosynthetically active radiation (PAR) reaching the Marandu canopy averaged 21% less for silvopasture than for grass monoculture; however, forage accumulation was not different between systems, nor were Marandu stomatal conductance, water-use efficiency (WUE), transpiration rate, transpiration ratio and leaf temperature. In silvopasture, PAR and forage accumulation were 33% and 29% less, respectively, at the 4-m distance than the 15-m distance from the edge row of trees, associated with lower transpiration rate and transpiration rate and greater WUE. We conclude that Marandu palisade grass can tolerate PAR reduction in silvopasture up to ~20% without reduction in forage accumulation, supporting its potential use in agroforestry systems for cattle production in the Brazilian Amazon Biome.

The understanding of plant morphological and physiological responses to shading can contribute to developing sustainable silvopastoral systems (SPS). Our objective was to evaluate the shading effect on herbage accumulation (HA), plant‐part composition, physiology, and canopy structural characteristics of Marandu palisadegrass {Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster [syn. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf]} under intermittent defoliation in a SPS with Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden and Eucalyptus urophylla S.T. Blake) in Sinop, Mato Grosso, Brazil. The experimental design was a randomized complete block arranged under a strip‐split‐plot, where the plots were allocated to four distances from the Eucalyptus grove (3, 6, 10, and 15‐m) in the SPS, on both faces (north and south), with four replications. The evaluations were done during two summer rainy seasons (RS1 and RS2) and one dry season (DS). The herbage accumulation (HA) in RS1 (4290 kg DM ha–1) was 51% greater than in RS2. The greatest canopy height, light interception, and leaf area index (LAI) values were measured during RS1 (25 cm, 91%, and 3.5 cm2 cm–2, respectively). Leaf photosynthesis rate was less at the 3‐m distance (12.5 μmol CO2 m–2 s–1) than at other distances (17.3 μmol CO2 m–2 s–1). We conclude that Marandu palisadegrass has the ability to physiologically adapt to shaded environments, although the dynamics along the whole tree growing cycle needs to be considered so that grass productivity can be sustained in the long‐term. Core Ideas Longer shading impacted canopy structure and forage accumulation at 3‐m distance. Physiological responses shows reduced light effects on the forage growth pattern. Morphologic composition and sward characteristics were only affected at 3‐m distance. Leaf photosynthesis rate was lesser close to the grove. Silvopastoral systems is an option for livestock production in the Brazilian Amazon.

New forage cultivars require defoliation studies for recommending proper grazing management. Our objective was to characterize herbage accumulation (HA), plantpart composition and nutritive value of guineagrass [Megathyrsus maximus (Jacq.) B. K. Simon & S. W. L. Jacobs] rotationally stocked under two grazing intensities. The experimental design was a randomized complete block with three replicates of a 2 × 2 factorial arrangement of two guineagrass cultivars ('BRS Quênia' and 'BRS Tamani') and two grazing intensities. Heavy (HGI) and lax (LGI) grazing intensities were imposed as post-grazing stubble heights: 15 and 25 cm for Tamani, and 20 and 35 cm for Quênia, respectively. The experimental period was from -grazing HM was sampled as two strata above the stubble height, each comprising 50% of the sampled height (upper and lower stratum). Total herbage accumulation was similar across years, cultivars, and intensities (16,810 kg DM ha −1 ). Quênia and Tamani had the greatest HA during summer. The leaf proportion was least in the HGI pastures. Under HGI, the lower stratum of both cultivars had the greatest stem proportion and the least nutritive value. The greatest herbage CP concentration and the least NDF, ADF, iNDF and LIG concentrations occurred in the upper stratum. Based on these results, 35 and 55 cm are recommended as target heights for initiation of grazing, and 25 and 35 cm as post-grazing stubble heights for Tamani and Quênia, respectively.

This study aimed to evaluate performance and behaviour of Nellore steers (Bos taurus indicus) in integrated systems. Treatments consisted of three different systems: livestock; crop-livestock; and livestock-forestry, with triple rows of eucalyptus trees. The experiment was carried out in Sinop, MT, Brazil, in a randomised complete block design with four replicates, during two seasons (dry-rainy transition and rainy). The experimental period was from 19 September 2015 to 10 January 2016. Nellore steers used in the experiment had an average initial weight of 344 kg ± 11 kg, in continuous stocking and variable stocking rate. Forage mass accumulation rate was evaluated and, independently of the system, had the highest values recorded during the rainy season. Microclimate was evaluated through temperature and humidity index, black globe temperature and humidity index and radiant heat load. Highest values were obtained from 11:00 a.m. to 3:00 p.m. at the dry-rainy transition period for all systems. Animal behaviour was assessed every 10 min from 7:00 a.m. to 5:00 p.m., and averages were calculated for every 2 h. The longest grazing period was recorded from 9:00 a.m. to 1:00 p.m., and then after 3:00 p.m., regardless of the system. Rumination occurred more frequently from 1:00 p.m. to 3:00 p.m. during the rainy season, and also in the shade for the livestock-forestry system. Highest weight gains per area were recorded during the rainy season and for the crop-livestock system. It is concluded that the highest yields can be achieved with the inclusion of the crop component in livestock production systems, and that Nellore steers in silvopastoral systems prefer to ruminate and stay idle in the shade.

The intake and total apparent and partial digestibility of nutrients, ruminal pH and ammonia concentrations and efficiency of microbial synthesis were evaluated in beef cattle fed diets containing sorghum silage and concentrate in the following ratios: 800:200, 650:350, 500:500 and 350:650 g/kg, in a total dry matter basis. Four crossbred Holstein x Zebu rumen and abomasum fistulated steers, 224 ± 23 kg-average initial live weight, were assigned to a 4 × 4 Latin square design. Chromic oxide was used as marker to estimate fecal and abomasal dry matter flows, and microbial efficiency was determined from purine basis. The intakes and total apparent digestibilities of DM, OM, CP and NFC and TDN intakes increased linearly (P b 0.01) with the increase of concentrate in the diet. NDF intake and total apparent digestibility decreased linearly (P b 0.05). The apparent ruminal and intestinal digestibilities of DM, OM, CP, NDF and NFC were not influenced (P N 0.05) by increasing the concentrate in the diet, and the mean values were 619 and 381 (g/kg); 656 and 349; 391 and 498; 902 and 79 and 600 and 399 (g/kg DM), respectively. There was a quadratic effect of collection time (P b 0.01) on the concentration of ruminal NH 3 -N and pH, considering maximum and minimum values of 14.89 mg/dL and 6.16 at 2.39 and 4.28 h after feeding, respectively. The efficiency of microbial synthesis, expressed in different ways was not influenced (P N 0.05) by treatments, with 11.39 g CPmic/100 gTDN on average. Although increasing concentrate levels in the diets resulted in higher intakes of almost all nutrients, this did not result in alterations in the ruminal variables evaluated. Livestock Science 107 (2007) 53 -61 www.elsevier.com/locate/livsciAbbreviations: DM, dry matter; OM, organic matter; CP, crude protein; NFC, non-fibrous carbohydrates; TDN, total digestible nutrients; NDF, neutral detergent fiber assayed with a heat stable amylase and expressed inclusive of residual ash; gCPmic/100 gTDN, grams of crude protein microbial per 100 g of total digestible nutrients; NH 3 -N, ammonia nitrogenous; NDIN, neutral detergent insoluble nitrogen; ADIN, acid detergent insoluble nitrogen; CHODR, total carbohydrates degraded in the rumen; TN, total nitrogen compounds; MicN, microbial nitrogen.

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