Luiz Januário Magalhães Aroeira

Estimativas de Consumo do Capim-Elefante (Pennisetum purpureum Schum), Fornecido Picado para Vacas Lactantes Utilizando a Técnica do Óxido Crômico

O consumo de materia seca (CMS) de vacas mesticas Holandes-Zebu, fistuladas no rumen, em lactacao, foi medido pela diferenca de peso do alimento oferecido e das sobras e estimado com auxilio do oxido cromico (Cr2O3) pela producao fecal (PF) e indigestibilidade do alimento. O delineamento experimental foi em tres quadrados latinos (3x3) e os tratamentos consistiram de capim-elefante cortado nas idades de 30, 45 e 60 dias. A digestibilidade in vitro da materia seca (DIVMS) foi determinada nas amostras do capim-elefante e estimada a partir do consumo medido diretamente e pela producao fecal obtida com o Cr2O3. A producao fecal foi tambem calculada (PFc) a partir dos valores do consumo (direto) e da DIVMS e foi estimada pela relacao do indicador administrado/indicador excretado. Foram observadas diferencas entre os CMS obtidos nas tres idades de corte do capim-elefante pelos dois metodos avaliados. Os CMS medios obtidos pelo metodo direto foram de 8,00; 10,00 e 11,02 kg/vaca/dia, respectivamente, para o capim cortado com 30, 45 e 60 dias. Os CMS estimados com auxilio do Cr2O3 foram de 9,00; 11,10 e 12,00 kg/vaca/dia, para os mesmos tratamentos. As estimativas de consumo utilizando o Cr2O3 foram superestimadas em 9,25% em relacao aos resultados obtidos pelo metodo direto.

Capim-elefante (Pennisetum purpureum Schum.), sob duas doses de nitrogênio. Consumo e produção de leite

The milk production, the dry matter intake (DMI) and the NDF passage rate in the gastrointestinal tract in four seasons (July, October, January and March), of crossbred cows, under grazing of elephant grass, submitted to two levels of nitrogen (300 and 700 kg N/ha•year) were estimated. The rotation grazing with three days of occupation and 30 days of resting, using 36 crossbred Holstein Zebu milking cows, in a stocking rate of 6 cows/ha, was used. The estimates of the intake and passage rate were determined only in 24 animals. For the extrusa collection, two esophageal fistulated cows were used. The intake was estimated using the fecal output: feed indigestibility ratio. The fecal output was estimated using the NDF of the extrusa marked with sodium dichromium fed in an unique dose. The total dry matter intake was not affected by the N levels and the year seasons, with average values of 10.9 and 10.5 kg DM/cow, for the levels of 300 and 700kg N/ha•year, respectively. However, the DM intake of the elephant grass was affected by N levels and year seasons, with reported values of 6.55 e 5.63 kg/cow•day, for the above described N levels, respectively. The elephant grass contributed with 26% of the total DM intake during the dry season (July/October) and its contribution increased up to 84% in the rainy season (January/March). The milk production was not affected by N levels, with reported average production of 11.6 and 12.3 kg/cow•day, for the levels of 300 and 700 kg N/ha•year, respectively.

Sward characteristics and performance of dairy cows in organic grass-legume pastures shaded by tropical trees.

The silvopastoral system (SPS) has been suggested to ensure sustainability in animal production systems in tropical ecosystems. The objective of this study was to evaluate pasture characteristics, herbage intake, grazing activity and milk yield of Holstein×Zebu cows managed in two grazing systems (treatments): SPS dominated by a graminaceous forage (Brachiaria decumbens) intercropped with different leguminous herbaceous forages (Stylosanthes spp., Pueraria phaseoloides and Calopogonium mucunoides) and legume trees (Acacia mangium, Gliricidia sepium and Leucaena leucocephala), and open pasture (OP) of B. decumbens intercropped only with Stylosanthes spp. Pastures were managed according to the rules for organic cattle production. The study was carried out by following a switch back format with 12 cows, 6 for each treatment, over 3 experimental years. Herbage mass was similar (P>0.05) for both treatments, supporting an average stocking rate of 1.23 AU/ha. Daily dry matter intake did not vary (P>0.05) between treatments (average of 11.3±1.02 kg/cow per day, corresponding to 2.23±0.2% BW). Milk yield was higher (P0.05) in subsequent years. The highest (P0.05) milk yields. Low persistence of Stylosanthes guianensis was observed over the experimental period, indicating that the persistence of forage legumes under grazing could be improved using adapted cultivars that have higher annual seed production. The SPS and a diversified botanical composition of the pasture using legume species mixed with grasses are recommended for organic milk production.

Disponibilidade, composição bromatológica e consumo de matéria seca em pastagem consorciada de Brachiaria decumbens com Stylosanthes guianensis

The objective of this work was to evaluate the herbage availability, nutritive value, dry matter intake and grass and legume percentage in diet of crossbred Holstein-Zebu cows, in pasture with Brachiaria decumbens cv. Basilisk, Stylosanthes guianensis var. vulgaris cv. Mineirao and tree legumes. To estimate the fecal output, it was used 10 g cow -1 day -1 of chromium oxide during ten consecutive days. Extrusa samples were used to determine the chemical composition and in vitro dry matter digestibility. B. decumbens availability varied with climatic conditions, while S. guianensis availability decreased linearly along the experimental period. Dry matter intake was higher in May/2001 (1.9% body weight) and did not differ among other months (1.5% body weight). Low dry matter intake values were related to low in vitro dry matter digestibility coefficients (42.1% to 48.0%) and high neutral detergent fiber content (70.2% to 79.4%). Dry matter intake was directly related to legume percentage in the pasture. This observation could indicate the potential of mixed pasture for improving nutritive value in dairy cattle diet.

Estimativa do Consumo Voluntário do Capim-Tanzânia (Panicum maximum, Jacq. cv. Tanzânia) por Vacas em Lactação sob Pastejo Rotacionado

The trial was carried out in a Tanzania grass (Panicum maximum) pasture, rotationally grazed by lactating cows, to estimate the dry matter intake. Three treatments were tested: crossbred cows fed 3 kg per day of concentrate and crossbred and Zebu cows (Gyr) without concentrate supplementation. The forage availability was 7,340.2 kg of dry matter (DM) /ha before and 5,639.5 after the 3rd grazing day. The Tanzania grass DM intake was 8.26 ± 5.66, 11.01 ± 5.37 and 9.55 ± 2.31 kg of DM/cow/day per day or 2.15, 2.37 and 2.34% of live weight, respectively, for the supplemented crossbred cows and non supplemented crossbred and Zebu cows. The average milk production was higher for the supplemented group (11.98 kg/cow/day). The milk production observed by the non supplemented cows was similar. Milk yield of 6.53 was obtained for non supplemented crossbred cows and 5.46 kg per cow/day was performed for the Zebu cows.

Efeito da suplementação e do intervalo de pastejo sobre a qualidade da forragem e consumo voluntário de vacas Holandês × Zebu em lactação em pastagem de capim-elefante

Mean daily dry matter intake of elephantgrass (DMI) (Pennisetum purpureum, Schumack) in a rotational grazing with lactating Holstein × Zebu cows was estimated in a trial carried out from February to September. The pasture was divided into paddocks and grazed for three days by 24 cows randomly allotted to four treatments. The treatments consisted on grazing intervals of 30 days, and concentrate (2kg/cow/day) and grazing intervals of 30, 36 or 45 days without concentrate. From February to May the elephantgrass was the only roughage, but from June to September (dry season) the cows were fed on chopped sugarcane plus 1% urea. DMI was estimated monthly using the extrusa in vitro dry matter digestibility (IVDMD) and the fecal output (chromium oxide). The average chemical composition of extrusa was generally similar (P>.05) among grazing intervals (6.1 to 18.2% of CP; 63.5 to 81.4% of NDF; 32.7 to 47.6% of ADF and 43.7 to 72.9% of IVDMD). The CP content of extrusas decreased and the NDF and ADF contents increased (P .05) among grazing intervals. During the dry season cows fed on treatments without concentrate the DMI varied from .39 to 2.2%BW and its contribution to total DM intake decresead from 52% in the first to 43% in the third day of paddock occupation. Sugarcane intake effectively minimized the effects of the low pasture intake in the dry season.

Óxido de cromo e n-alcanos na estimativa do consumo de forragem de vacas em lactação em condições de pastejo

Foram avaliadas as tecnicas do oxido de cromo/digestibilidade in vitro e dos pares de n-alcanos (C31:C32 e C33:C32) na estimativa do consumo de materia seca (CMS) por vacas Holandes x Zebu em lactacao em pastagem de capim-elefante cv. Napier. As extrusas foram obtidas utilizando-se uma vaca com fistula esofagica. Realizaram-se coletas de fezes duas vezes ao dia, diretamente no reto dos animais, durante nove dias em cada periodo experimental. O delineamento utilizado foi o de blocos casualizados, em esquema de parcelas divididas. Ambos os pares de n-alcanos possibilitaram estimativas de consumos semelhantes, independentemente do horario de coleta (manha e tarde), sugerindo que uma unica coleta de fezes por dia seria suficiente. Quando o estudo foi realizado utilizando-se o valor medio das duas coletas, todas as metodologias diferiram entre si. O Cr2O3/DIVMS forneceu valores de CMS que podem ser considerados mais adequados, pois foram mais proximos daqueles estimados para forragem consumivel (2,6% PV) e dos valores das tabelas de exigencias do NRC (2001) (2,7% PV). Alem disso, essa tecnica apresentou vantagens quanto a simplicidade dos procedimentos analiticos e ao baixo custo.

Produção de leite de vacas mestiças Holandês ´ Zebu em pastagem de capim-elefante, com e sem suplementação de concentrado durante a época das chuvas

This work aimed to study the effect of concentrate supplementation of elephantgrass pasture during the rainy season and at the beginning of the dry season, on milk yield, milk composition and weight gain of crossbred Holstein ´ Zebu cows. The treatments were: elephantgrass pasture with no concentrate supplementation (NC) and with 2kg concentrate supplementation cow/day (WC). The experimental area was divided in 44 paddocks with 606m2 each, corresponding to 22 paddocks per replication and six cows per treatment. The cows were alloted to the treatments according to a completely randomized block design. The pasture was managed in a rotational system with 30 days resting period and three days grazing per paddock. The stocking rate was 4.5 cows/ha. The pasture was fertilized with 200kg/ha/yr of N and K2O. The average fat corrected (4%) milk yield was 11.6± 0.3 and 12.5± 0.3kg/cow/day and the average daily weight gain during the total experimental period was 211 and 244g per cow for the NC and WC treatments, respectively. There were differences (P<0.05) between treatments for milk yield and milk protein (%), but no treatment effects were observed on weight gain, milk fat (%) and milk total solids (%).

Influência de estratégias de manejo em pastagem de capim-elefante na produção de leite de vacas Holandês x Zebu

The objective of this trial was to study the effect of different strategies of grazing management on milk production of cows on elephantgrass pastures. The treatments were: 30 days of grazing interval (GI) and fertilized monthly (30MF); 30 days GI and fertilized every two months (30BM); 45 days GI and a stubble height of 90-100cm (45HS); 45 days GI and a stubble height of 40-50cm (45LS). In treatments 30MF and 30BM the stubble height was 90-100cm. Each paddock was grazed for three days. Twenty four Holstein ´ Zebu cows were allocated to treatments (six/treatment). The area was divided into 108 paddocks, 64 of 417m2 each for the two 45 days GI treatments (16 paddocks/area replication). Others 44 paddocks of 606m2 each, were allocated for the two 30 days GI treatments (11paddocks/area replication). The stocking rate was 4.5 cows/ha. The pasture was fertilized with 200kg/ha/year of N and K2O, 40kg/ha of P2O5 and 1,000kg/ha of limestone. The average fat corrected (4%) milk yields were 10.3, 10.5, 9.3 and 9.2kg/cow/day for treatments 30MF, 30BM, 45HS and 45LS, respectively. There was a significant milk yield difference (P<0.05) between the 30 and 45 day-resting periods.

Estimativas do Consumo e da Taxa de Passagem do Capim-Elefante (Pennisetum purpureum Schum.) sob Pastejo de Vacas em Lactação

The voluntary dry matter intake (DMI), rate of passage and mean retention time in the rumen and gastrointestinal tract were estimated using 18 crossbred Holstein-Zebu lactating cows grazing elephantgrass. The voluntary DMI and fecal output estimations the models proposed by QUIROZ et al. (1988) and POND et al. (1989) were used. The data of rate of passage and those of retention time in the rumen the model suggested by GROVUM and WILLIAMS (1973) was chosen. The elephantgrass pasture were fertilized and managed in a rotational system with three days paddock occupation and 30 days resting. The stocking rate was 6 cows/ha. The DMI was estimated using the relation fecal output/forage indigestibility of extrusa samples. For the fecal production calculations, neutral detergent fiber was chromium mordanted. Using the models of POND et al. (1989) and QUIROZ et al. (1988) to compare the total diet DMI (12.5 and 13.9 kg/cow/day) and elephantgrass DMI (7.7 and 9.2 kg/cow/day) they did not differ, respectively. However, the rate of passage and the mean retention time in the gastrointestinal tract did differ among the three used models. The results of this trial showed that the model proposed by QUIROZ et al. (1988) was the one that better describes the DMI data.