Ana Clara Rodrigues Cavalcante

Dietas contendo silagem de milho (Zea maiz L.) e feno de capim-tifton 85 (Cynodon spp.) em diferentes proporções para bovinos

The intake, digestibility, ruminal pH and ammonia concentrations and passage rate were evaluated in steers fed corn silage (CS) and Tifton 85 bermudagrass hay (T85H)-based diets, at different forage proportions. Four rumen fistulated steers with 523 kg of live weight were used in a 4x4 latin square design, and fed diets containing 60:40 forage:concentrate proportions in dry matter basis. The forage portion consisted of: 100 T85H:0 CS; 67 T85H:33 CS; 33 T85H:67 CS and 0 T85H:100 CS. The dry matter (DM), organic matter (OM), digestible organic matter (DOM), crude protein (CP), neutral detergent fiber (NDF), total carbohydrates (TC) and total digestible carbohydrates (TDC) intakes were not affected by different T85H: CS proportions and averaged 9.2, 8.7, 6.4, 1.1, 3.7, 7.3 and 5.4 kg/day, respectively. The ethereal extract (EE) intake increased with increasing on corn silage proportion of the diets. The DM, OM, CP, EE and TC apparent digestibilities were not affected by increasing percentage of corn silage on rations and averaged 71.8, 73.0, 69.5, 69.2 and 73,9%, respectively. There was a quadratic effect for NDF digestibility, with maximum value of 65.2% for diets with 30.98% of CS. The N-ammonia maximum content (12.0 mg/100 ml) and minimum value of pH (5.98) were estimated 2.44 and 6.82 hours after feeding, respectively. The passage rate, which was not affected by changing T85H:CS proportions in the forage, averaged 4.2 %/hour.

Resíduo agroindustrial da carnaúba como fonte de volumoso para a terminação de ovinos

The objective of this work was to evaluate the effects of ammonization with different levels of urea and the use of soybean grains as a urease source, for the improving of the chemical composition of carnauba (Copernicia prunifera) agroindustrial residue (BC). The levels of urea were 0, 2.5, 5, 7.5 and 10% in relation to the percentage of total dry matter of BC and the levels of toasted soybean grains were 0 and 20%. Evaluations were also made for forage intake and performance of confined sheep subjected to diets with increasing levels of replacement of Tifton 85 grass (Cynodon spp.) hay (FT) by BC: 100% FT, 25% BC plus 75% FT, 50% BC plus 50% FT, 75% BC plus 25% FT, and 100% BC. Thirty crossbred 80-day old weaned sheep with 17 kg initial average weight were used. Crude protein in the forage increased with the increasing doses of urea. Increases were also observed for neutral detergent fiber and cellulose contents and reductions were observed for roughage digestibility. The highest daily intake of dry matter, organic matter, crude protein, ethereal extract and neutral detergent fiber were observed in animals fed only FT. Animal performance decreased with increase of BC in the diet.

Soil carbon and nitrogen stocks in traditional agricultural and agroforestry systems in the semiarid region of Brazil

SUMMARY In the semiarid region of Brazil, inadequate management of cropping systems and low plant biomass production can contribute to reduce soil carbon (C) and nitrogen (N) stocks; therefore, management systems that preserve C and N must be adopted. This study aimed to evaluate the changes in soil C and N stocks that were promoted by agroforestry (agrosilvopastoral and silvopastoral) and traditional agricultural systems (slash-and-burn clearing and cultivation for two and three years) and to compare these systems with the natural Caatinga vegetation after 13 years of cultivation. The experiment was carried out on a typical Ortic Chromic Luvisol in the municipality of Sobral, Ceara, Brazil. Soil samples were collected (layers 0-6, 6-12, 12-20, 20-40 and 40-60 cm) with four replications. The plain, convex and concave landforms in each study situation were analyzed, and the total organic C, total N and densities of the soil samples were assessed. The silvopastoral system promoted the greatest long-term reductions in C and N stocks, while the agrosilvopastoral system promoted the smallest losses and therefore represents a sustainable alternative for soil C and N sequestration in these semiarid conditions. The traditional agricultural system produced reductions of 58.87 and 9.57 Mg ha-1

Mudanças Climáticas Globais e a Pecuária: Cenários Futuros para o Semiárido Brasileiro (Global Climatic Changes and Animal Production: Future Scenarios for the Brazilian Tropical Semiarid)

Os sistemas de producao animal no Semiarido brasileiro podem ser vulneraveis as mudancas climaticas. Cenarios futuros para a producao de Brachiaria brizantha, Panicum maximum, Cenchrus ciliaris e Opuntia ficus indica foram analisados para a identificacao de areas mais vulneraveis. A partir dos modelos ja disponiveis, foram identificadas algumas areas de maior vulnerabilidade, o que possibilitou a indicacao de alternativas de adaptacao dos sistemas de producao para mitigacao de possiveis impactos negativos das mudancas climaticas globais sobre a producao animal do Semiarido brasileiro. O desenvolvimento de tecnicas para o uso sustentavel da Caatinga como pasto nativo contribuira para reduzir a degradacao deste bioma e os riscos de desertificacao da regiao. Novas variedades de plantas forrageiras, tanto de exoticas quanto de especies nativas, melhor adaptadas para as condicoes de cenarios climaticos futuros poderao ser desenvolvidos atraves do melhoramento vegetal. O uso de irrigacao de pastagens e o aproveitamento de co-produtos na alimentacao dos animais contribuirao para o aumento de produtividade e para a reducao da pressao sobre a vegetacao nativa. Diversos grupos de pesquisa tem desenvolvido modelos melhores para projecao regionalizada de chuva e de temperatura. O desenvolvimento desses modelos permitira uma investigacao mais precisa dos possiveis impactos das mudancas climaticas globais sobre a pecuaria no semiarido brasileiro.

Goat milk production and quality on Tanzania-grass pastures, with supplementation

It was evaluated the production and quality of milk produced by goats grazing Panicum maximum Jacq cv. Tanzania (Guineagrass) and receiving four levels of concentrate supplementation. Eight Anglo Nubian goats, aged between two and four years, 43.6 kg in average body weight and between the 2 and 4 lactation were distributed into two 4 x 4 balanced Latin square design. The supplementation levels were: 0.0, 0.5, 1.0 and 1.5% of body weight. The concentrate was composed of corn and soybean meal. The intake of dry matter and nutrients, and the daily production of milk, 4% fat-corrected milk, fat, protein, lactose and total solids had increased (p < 0.05) with supplementation, whereas fat and total solids percentage were reduced (p < 0.05). The concentrate supplementation up to 1.5% of live weight in Tanzania-grass pasture raises the intake of dry matter and nutrients, resulting in a linear increase in milk production and of its components.

Níveis críticos para atributos do solo pela distribuição normal reduzida em culturas anuais de subsistência

This study aimed to propose critical levels for soil chemical properties using the reduced normal distribution in areas of family subsistence farming under maize and cowpea crops in the Brazilian semiarid. Soil samples were collected on family farms in the region of Inhamuns-Crateus. To obtain the critical levels the reduced normal distribution was used which uses the productivity data and the relationship between productivity and soil chemical attributes and assigning the critical level for 90% of the maximum. Critical levels obtained for areas cultivated with maize and cowpea in the semiarid region are: OM (g kg-1): 7.3 and 7.5; pH: 6.6 and 6.5; P (mg dm-3): 8.6 and 8.2; K (mmolc dm-3): 2.8 and 2.7; Ca (mmolc dm-3): 33.3 and 22.4; Mg (mmolc dm-3): 11.2 and 9.9; and base saturation (%): 73 and 71, respectively. The critical level for reduced normal distribution can be used to obtain critical levels for soil chemical properties. The attributes most frequently for negative index over estimated critical level (NCRIz) are Ca > V > pH > Mg > K = OM > P and V > pH > P > OM > Mg > K > Ca areas for corn and cowpea, respectively.

Biomass flow in Tifton-85 bermudagrass canopy subjected to different management strategies under rotational grazing with dairy goats

Biomass flow characteristics and forage accumulation were evaluated in Bermudagrass (Tifton 85) pasture managed under intermittent stocking with different management strategies. The management levels utilized were conventional (10 cm residual height and unfertilized), light (20 cm residual height and unfertilized), moderate (20 cm residual height with fertilization of 300 kg N/ha.year) and intensive (10 cm residual height with fertilization of 600 kg N/ha.year). A randomized design was used with repeated measurements over time, in two periods of the year, with four replicates. There was significant effect of management × period of the year on the leaf elongation rate (LER). The management levels under fertilization (0.59 and 0.60 cm/tiller.day for the intensive and moderate management, respectively) and the rainy season (0.49 cm/tiller.day) showed the greatest stem elongation rate. Leaf senescence rate (LSR) before and after and total LSR were modified by the management × period of the year interaction. The intensive management, with 0.38 leaves/tiller.day, as well as the dry period, with 0.27 leaves/tiller.day, showed higher leaf appearance rate. The lowest phyllochron was observed in intensive management and dry periods, as well as an interaction with the management of the same periods of the year. There was management × period of year interaction effect on leaf lifespan; the highest value was found under conventional management and dry period. Both production and forage accumulation rates were higher in the intensive and moderate management levels and dry season, and there was interaction of the intensive management system with the seasons. Managing pastures under moderate and intensive rotational stocking, which occurred mainly in the rainy and dry seasons, respectively, maximizes the flow of tissues and consequently production and accumulation of forage.

Ecophysiology of deciduous plants grown at different densities in the semiarid region of Brazil

Physiological differences in the Cordia oncocalyx tree growing at different densities in two distinct areas were investigated. An agrosilvopastoral system (AGP) and a secondary forest (SF) were studied. Under both types of land-use, C. oncocalyx presented a relative frequency of approximately 50%, and absolute densities of 670 and 80 individuals per hectare, respectively. Net photosynthesis (A), stomatal conductance (gs), and transpiration (E) were measured, and the SPAD index was recorded in sun leaves from the canopy and shade leaves from the lower canopy, in both the wet and dry seasons. We quantified the dry biomass of leaves and fruit on a per-tree basis at the end of the wet season. Net photosynthesis was higher in shaded leaves in the AGP in the wet season, reaching an average of 4.8 μmol m-2 s-1 against 3.2 μmol m-2 s-1 under SF. As trees began to shed their leaves at the beginning of the dry season and more radiation reached the shaded leaves, there was an increase in SF for A, depending on the intensity of light reaching the leaves. In the sun leaves, gas exchange was similar for the land-use systems during the wet season, but stronger in AGP than under SF during the dry season. This happened when the leaves in AGP retained more relative water content during a period of low gravimetric levels of the soil water. The lower tree density in AGP promoted a higher SPAD index and dry biomass in both the sun and shaded leaves, and allowed greater A, E and gs rates in the sun leaves at the beginning of the dry period.

Environmental parameters and tree physiology in two semiarid land use systems in Brazil

To determine if reduced tree densities (number of trees per unit area) lead to changes in micro-meteorological and tree physiological characteristics, two areas with different tree densities were assessed. One was an agrosilvopastoral system (AGP) with low tree density, and the other, a secondary forest (SF) with greater tree numbers, both located in a semiarid region of Brazil. Data were collected simultaneously by two automated weather stations: rainfall, air (Ta) and soil temperatures (Ts5cm), relative humidity (RHair), photosynthetically active radiation (PAR), soil moisture at two depths (Ms30cm and Ms50cm), and wind velocity (Vw). Net photosynthesis in Cordia oncocalyx Allemão trees was measured with an infrared gas analyzer in February, March, May, July, August and September 2011, which encompasses a rainy period followed by a dry period. Average values of Ta, Ts5cm, Vw and PAR were greater and average values of RHair and Ms50cm were lesser in the AGP. Photosynthetic rates were greater in plants growing under the AGP at the onset of the dry season when Vw, PAR and Ts5cm were greater and Ms50cm was lesser. Photosynthetic rates correlated strongly with physical parameters during the dry season, especially under SF. Differences in tree numbers between AGP and SF led to differences in physical environmental parameters; however, the latter had less influence on photosynthetic rates in C. oncocalyx during the rainy season. During the dry season, all physical parameters had an impact on net photosynthesis under SF but not under AGP. This indicates a certain independence of plants in AGP.

APTIDÃO AGROCLIMÁTICA E NECESSIDADE HÍDRICA PARA O CULTIVO DO CAPIM TANZÂNIA NO ESTADO DO CEARÁ

This study aimed to define areas suitable, and the irrigation water requirement for, cultivation of Tanzania guineagrass in the state of Ceará, Brazil. Tanzania guineagrass yield was estimated by a mathematical model, which considers the crop actual evapotranspiration, resulting from the crop climatological water balance. The water requirement throughout the year was estimated for soils with a water holding capacity of 20 (shallow soils), 40 (sandy soils), 60 (soils with medium texture) and 100 mm (clay soils). The relative frequency of occurrence of monthly productions greater than 2,750 kg DM ha month was obtained for different areas in Ceará, representative of most of the states economic mesoregions. Tanzania guineagrass annual yields in the state of Ceará were between 20,000-30,000 kg DM ha year. During the rainy season, the productive potential varies with the economic mesoregion, which presents different climatic conditions. The state of Ceará is only suitable for the rainfed production of Tanzania guineagrass for 4 months each year, predominantly from February to May, while weather conditions do not favor the development of this grass in the remaining months.