ABSTRACT. To evaluate the bromatological composition and ruminal degradability of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) of Xaraés palisade grass (Urochloa brizantha ‘Xaraes’ syn Brachiaria brizantha) under grazing in integrated crop, livestock (ICL), and forest (ICLF) systems, we conducted an in situ degradability trial in randomized blocks with three non-lactating 3/4 Gyr × 1/4 Holstein cows, provided with ruminal cannula. The management of Xaraés palisade grass was similar in both systems, differing only regarding shading in the ICLF system provided by eucalyptus trees (average 65% crown cover). Grass samples were incubated for 0, 3, 6, 9, 12, 24, 36, 48, 72, and 96 hours. Considering the passage rate 2% h-1, the Xaraés palisade grass of ICL system had greater NDF effective degradability in relation to ICLF (46.38 vs 44.98%). However, the palisade grass CP potential degradability was greater in the ICLF than in the ICL system (68.92% vs. 65.40%). The presence of trees in the pasture has effect on nutritional traits of the Xaraés palisade grass, increasing its protein content and degradability and reducing its fiber degradability.

ABSTRACT. To compare the integrated crop-livestock-forest (ICLF) and crop-livestock (ICL) systems in relation to thermal comfort and grazing behavior of Girolando heifers, a 2 × 2 crossover trial (two system and two periods) was carried out with eight – Holstein × ¼ Gyr heifers in Xaraés-palisade grass pasture under intermittent stocking with 10 days of occupation period and 20 days of resting. In ICLF, crown cover of eucalyptus planted in rows was 65% at the beginning of the experiment. Animal behavior was assessed through bioacoustics by recording heifers’ sounds for 48 hours. Concomitantly, heifers’ internal temperature (IT, °C) was recorded every 10 min using data logger thermometers adapted to hormone-free intravaginal devices. Air temperature and humidity data were collected by thermohygrometers located in the center of ICLF and ICL for calculating Temperature-Humidity Index (THI). According to THI values, ICLF and ICL did not vary in terms of thermal comfort. However, THI indicated moderate stress (82.26±4.40) during day (06:00 to 17:59h) and mild stress (75.76±4.38) at night (18:00 to 05:59h) in both systems. During day, heifers from ICL had significantly (p < 0.05) higher IT (39.51±0.56oC) than those from ICLF (39.41±0.56oC); the former spent more time grazing and less time drinking water in ICLF (581.35±30.1 and 4.87±1.09 min, respectively) when compared with those from ICL (436.88±28.1 and 10.25±1.09 min, respectively). Therefore, although thermal comfort index did not vary between the systems, under moderate stress, crossbred heifers have lower internal temperatures, resulting in longer diurnal grazing and shorter water drinking time in Eucalyptus-shaded pastures.

RESUMO A relação entre índices de conforto térmico com a temperatura interna de vacas lactantes foi avaliada em Rondônia, na Amazônia Ocidental, em um ensaio crossover 2x2 utilizando oito vacas Girolando, ½ Holandês x ½ Gir (n=4) e – Holandês x ¼ Gir (n=4) pastejando capim-marandu suplementadas com concentrados contendo ou não óleo de soja. A temperatura interna (TI) dos animais foi aferida com termômetros eletrônicos adaptados em dispositivos intravaginais (livres de hormônio) a cada 10 minutos durante 48h. Concomitantemente, dados climáticos (temperatura do ar, umidade relativa do ar, velocidade do vento e radiação solar) foram coletados para cálculo dos índices de temperatura e umidade (ITU), índice de temperatura equivalente (ITE) e o índice de frequência respiratória predita (PFR). A suplementação com óleo de soja não afetou a temperatura interna das vacas. A TI variou significativamente entre os grupos genéticos, com a maior média observada à noite nas vacas – Holandês × ¼ Gir em relação às ½ Holandês × ½ Gir (39,54 °C vs 39,06 °C, respectivamente). ITU, ITE e PFR tiveram correlação significativa e positiva com a TI de vacas Girolando, mas o PFR não foi adequado para indicar estresse térmico em vacas no período da noite.

ABSTRACT The relationship between the indices of thermal comfort and internal temperature in lactating cows was evaluated inRondônia, western Amazonia in a 2 × 2 crossover trial carried out with eight Girolando cows, ½ Holstein × ½ Gyr (n=4) and – Holstein × ¼ Gyr (n=4), grazing palisade grass supplemented with or without soybean oil concentrates. Data logger thermometers adapted to intravaginal devices (hormone free) were used to measure internal temperatures (IT) every 10 min over 48 h. Concomitantly, environmental parameters (air temperature, relative humidity, wind speed, and solar radiation) were collected for the estimation of the temperature-humidity index (THI), equivalent temperature index (ETI), and predicted respiratory rate (PRR). Supplementation with soybean oil did not affect the internal temperature of the cows. IT varied significantly between the genetic groups, with the highest mean observed at night in the – Holstein × ¼ Gyr cows, compared with that in the ½ Holstein × ½ Gyr cows (39.54 °C vs 39.06 °C, respectively). THI, ETI, and PRR were significantly and positively correlated with the IT of the Girolando cows; however, the PRR was not found to be adequate in indicating the night-time heat stress in cows.

O experimento foi desenvolvido em casa de vegetação na Embrapa Pecuária Sudeste, utilizando acessos de Brachiaria brizantha. O delineamento experimental foi o de blocos ao acaso, com arranjo fatorial 2 X 4, sendo dois tratamentos (com e sem déficit hídrico) e quatro genótipos. O grupo de genótipos avaliado foi formado pelas cultivares 'BRS Piatã', 'Marandú', 'Xaraés' e 'BRS Paiaguás', sendo o experimento realizado durante o mês de julho de 2008. As variáveis analisadas foram massa seca total, massa seca de parte aérea, massa seca de raiz, massa seca de colmo, massa seca de folha, taxa de alongamento foliar, área foliar, área foliar específica. O estresse por deficiência hídrica exerceu efeito negativo em todas as características estudadas e em todos os acessos avaliados. A cultivar 'BRS Piatã' foi o genótipo que menos apresentou alteração entre os tratamentos com e sem déficit hídrico, indicando portanto, tolerância dessa cultivar em relação ao estresse por falta de água no solo nessas condições experimentais

The experiment was conducted in a greenhouse at Embrapa Southeast Livestock, using Brachiaria brizantha accessions. The experimental design was fully randomized blocks with a 2 x 4 factorial arrangement, with two treatments (with and without water deficit) and four genotypes. The group evaluated was formed by genotypes 'BRS Piatã', 'Marandu', 'Xaraés' and 'BRS Paiaguás'. The experiment was conducted during the month of July 2008. The variables analyzed were dry mass of total plant, shoot mass, leaves, stems and roots, leaf elongation rate, leaf area and specific leaf area. The water deficit stress exerted negative effect on all characteristics studied and in all accessions. 'BRS Piatã' was the genotype that showed less change between treatments with and without water deficit, thus indicating tolerance of this cultivar in relation to water stress in the soil under these experimental conditions

In this study, the microclimate changes in silvopastoral systems are quantified at different time and spatial scales and compared with single-pasture systems. The study was conducted in a silvopastoral system in São Carlos, Brazil (22°01' South and 47°53' West). The silvopastoral system consisted of grass pastures [Urochloa (sin. Brachiaria) decumbens cv. Basilik] lined with strips of native trees spaced at 17 m. Continuous microclimate measurements (air temperature, relative humidity, wind speed, and incident photosynthetically active radiation) were carried out from September 2010 to September 2012 at two positions of the silvopastoral system (2.0 and 8.5 m from the rows of trees) and at a pasture under full sunlight, located in an adjacent area. The soil moisture was monitored weekly from 24 March 2010 to 1 April 2012 at distances of 0.0, 2.0, 4.75, and 8.5 m from the rows of trees. The rows of native trees reduced wind speeds (46% reduction) and changed the photosynthetically active radiation incidence pattern on the pasture (up to 40% reduction of incidence at the point nearest to the trees). The combined action of these factors promoted thermal and air humidity changes on the pasture at the different points measured. With respect to soil moisture, there was greater soil moisture removal at the sampling points near the rows of native trees under the silvopastoral system, mainly due to enhanced exploration by tree roots at greater depths in dry spells or early dry periods, when compared with the midpoints between the rows.

Two cultivars of Brachiaria brizantha (Hochst ex. A. Rich) Stapf. (Syn. Urochloa) were evaluated for their adaptation to water deficit and the stress response mechanisms in a greenhouse experiment. The experimental design was in completely randomized blocks with a 2 × 2 × 4 factorial arrangement. The Marandu and BRS Piatã cultivars were evaluated under two water availability conditions, with or without water restriction. The harvests were carried out 0, 7, 14 and 28 days after the start of water restriction. For both cultivars, the water deficit stress caused a reduction in shoot biomass and leaf area and an increase in the percentage of roots in the deeper soil layers. The B. brizantha cv. Marandu reached critical levels of leaf water potential in a shorter period of water restriction than did the B. brizantha cv. BRS Piatã. The osmoregulation and deepening of the root system are mechanisms of adaptation to water stress observed in both Marandu and BRS Piatã cultivars. Besides that, the Marandu cultivar also increases its leaf senescence and, consequentially, decreases its leaf area, as a response to water deficit.

O objetivo deste trabalho foi desenvolver e validar modelos de regressão linear para a estimativa de produção de matéria seca de capim‑tanzânia (Megathyrsus maximus, cultivar Tanzania) em função de variáveis agrometeorológicas. Para tanto, dados de períodos de crescimento da forragem entre 2000 e 2005, em condições de sequeiro em São Carlos, SP, foram correlacionados aos seguintes parâmetros climáticos: temperaturas mínima e média, graus‑dia, evapotranspiração potencial e atual. Foram realizadas regressões lineares simples entre as variáveis agrometeorológicas (independentes) e a taxa média de acúmulo (dependente). As estimativas foram validadas com dados independentes obtidos em São Carlos e Piracicaba, SP. Os melhores resultados estatísticos observados no desenvolvimento e na validação dos modelos foram obtidos para parâmetros agrometeorológicos que levem em consideração o efeito térmico e hídrico conjuntamente, como evapotranspiração real, acúmulo de graus‑dia corrigido pela disponibilidade hídrica e índice climático de crescimento, baseado na temperatura média, na radiação solar e na disponibilidade hídrica. Essas variáveis podem ser utilizadas em simulações e modelos para prever a produção do capim‑tanzânia.

The objective of this work was to develop and validate linear regression models to estimate the production of dry matter by Tanzania grass (Megathyrsus maximus, cultivar Tanzania) as a function of agrometeorological variables. For this purpose, data on the growth of this forage grass from 2000 to 2005, under dry‑field conditions in São Carlos, SP, Brazil, were correlated to the following climatic parameters: minimum and mean temperatures, degree‑days, and potential and actual evapotranspiration. Simple linear regressions were performed between agrometeorological variables (independent) and the dry matter accumulation rate (dependent). The estimates were validated with independent data obtained in São Carlos and Piracicaba, SP, Brazil. The best statistical results in the development and validation of the models were obtained with the agrometeorological parameters that consider thermal and water availability effects together, such as actual evapotranspiration, accumulation of degree‑days corrected by water availability, and the climatic growth index, based on average temperature, solar radiation, and water availability. These variables can be used in simulations and models to predict the production of Tanzania grass.

O objetivo deste estudo foi testar modelos empíricos de regressão linear, para a predição do acúmulo de matéria seca (TAMS) de Urochloa brizantha cv. Marandu, em função de variáveis agrometeorológicas. Para gerar os modelos, foi utilizada a taxa média de acúmulo de matéria seca, em condições de sequeiro, entre 1998 e 2002. As variáveis avaliadas foram: temperaturas mínima, máxima e média, radiação global (Rg), graus-dia, evapotranspiração real (ETR) e potencial (ETP) obtidas a partir do balanço hídrico, unidades fototérmicas (UF) e índice climático de crescimento (ICC). As regressões univariada e multivariada mostraram boa capacidade de predição, com exceção para as que utilizam a UF. Os melhores resultados foram para a regressão multivariada, com Tmín, Rg e ETR: R², 0,84; raiz do quadrado médio do resíduo (RQMR), 14,72; e critério de informação de Akaike (CIA), 222,5. Na regressão linear univariada, destacaram-se as variáveis: graus-dia corrigido (R², 0,75; RQMR,17,84; e CIA, 242,6), temperatura mínima corrigida (R², 0,75; RQMR, 17,82; CIA, 244,1), e ICC (R², 0,74; RQMR, 17,85; CIA, 236,9). A correção das variáveis agrometeorológicas pela relação entre evapotranspiração real e potencial (ETR/ETP), em geral, melhora a predição da TAMS pelos modelos.

The objective of this work was to test empirical linear regression models, to predict dry matter accumulation rates (DMAR) of Urochloa brizantha cv. Marandu, using agrometeorological variables. To generate the models, the average dry matter accumulation under rainfed conditions, between 1998 and 2002, was used. The evaluated variables were: minimum, maximum and average temperatures, global radiation (GR), degree-days, actual (AET) and potential evapotranspiration (PET) obtained from the water balance, photothermal units (PU) and the climatic growth index (CGI). Except for the PU, the univariate and multivariate regressions showed good predictive ability. The best results were for the multivariate regression, with Tmín, GR and AET: R², 0.84; root mean square residual (RMSR), 14.72; and Akaike's information criterium (AIC), 222.5. In the univariate regression, the following variables stood out: corrected degree-days (R², 0.75; RMSR, 17.84; CIA, 242.6), corrected minimum temperature (R², 0.75; RMSR, 17.82; AIC, 244.1); and CGI (R², 0.74; RMSR, 17.85; AIC, 236.9). The correction of the agrometeorological variables using the relation between real and potential evapotranspiration (AET/PET) enhances, in general, the model prediction of DMAR.