F. Deresz

Influência do período de descanso da pastagem de capim-elefante na produção de leite de vacas mestiças Holandês x Zebu

The objective of this trial was to study the effect of three grazing intervals (T30 = 30 days, T36 = 36 days and T45 = 45 days) on milk yield and live weight changes of crossbred Holstein x Zebu cows grazing elephantgrass pasture rotationally managed. The experiment was conducted during the rainy season using 18 crossbred cows averaging 30 days of lactation and 488 kg of average live weight. The cows were allocated to experimental treatments according to a completely randomized block design, with six blocks, two series of paddocks and three cows/paddock, based on milk yield and body weight of cows at the beginning of lactation. The stocking rate was fixed at 4.5 cows/ha and no concentrate was fed. Each paddock was grazed for three days in each grazing cycle. The pasture was fertilized with 200 kg/ha of N and K2O, divided in three applications during the rainy season. It was also applied 40 kg of P2O5 and 1,000 kg of dolomite limestone at the same time of the first application of N and K. The average fat corrected (4%) milk yield was 11.4; 10.6 and 10.3 kg/cow. day and the average liveweight gain during the experimental period was 114, 160 and 116 g/cow. day for the T30, T36 and T45 treatments, respectively. No difference was observed either for milk yield or liveweight gain.

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.

Produção de leite de vacas mestiças Holandês x Zebu em pastagem de capim-elefante, manejada em sistema rotativo com e sem suplementação durante a época das chuvas

The objectives of this trial were to study the effect of supplementation with concentrate on elephant grass pasture rotationally managed on milk yield and composition and live weight changes of crossbred Holstein x Zebu cows. The treatments were: no concentrate (NC) and 2 kg concentrate/cow/day (WC). The experiment was carried out during the rainy season. The area was divided in 44 paddocks of 606 m2 each, with 22 for each treatment, with two areas replication of 11 paddocks each. Twelve crossbred cows were utilized (six cows/treatment), with 30 days of lactation and 488 kg of live weight on average. The cows were allocated to the treatments according to a completely randomized block design. The blocks were based on milk yield and body weight of cows at the beginning of lactation. The pasture was managed in a rotational system with 30 days grazing interval and three days of grazing in each paddock. The stocking rate was established at 4.5 cows/ha. The pasture was fertilized with 200 kg/ha/yr of N and K2O, divided in three equal applications. It was also applied 40 kg/ha/yr of P2O5 and 1,000 kg/ha/yr of dolomite limestone. The average fat corrected (4%) milk yield was 11.4 and 12.6 kg/cow/day and the average daily gain during the experimental period was 114 and 180 g per cow for treatments NC and WC, respectively. There was a significant treatment effect for milk yield, but no effect on live weight gain.

Disponibilidade de matéria seca, composição química e consumo de forragem em pastagem de capim-elefante nas estações do ano

The study was carried out on elephantgrass (Pennisetum purpureum Schum.) pasture, from February 1999 to November 2001, in order to evaluate the dry matter (DM) availability, observing the height of the stubble; chemical composition; in vitro dry matter digestibility (IVDMD), and dry matter intake (DMI), using Holstein x Zebu lactating cows, during different seasons of the year. The paddocks were managed in a rotational grazing system, with 30 days of resting period and three days of occupation. Nutritive value and DM availability were monthly evaluated and the DMI was measured ten times during the experimental period. During dry season, cows were supplemented with corn silage during the milking intervals. The highest DM availability was estimated in December (3,402kg/ha). From May to September, values ranged from 558 to 1,122kg/ha, showing the strong seasonality on DM production. Means of crude protein and IVDMD did not differ among summer, autumn, and spring, but were lower during the winter. Means of neutral detergent fiber were lower in summer, autumn, and spring and higher during the winter. The pasture DMI were higher in summer, autumn, and spring and lower in the winter, due to low availability of elephantgrass. However, total DMI did not differ among seasons due to the corn silage supplementation during the winter season.

Composição química, digestibilidade e disponibilidade de capim-elefante cv. Napier manejado sob pastejo rotativo

One experiment was run to study the chemical composition, in vitro dry matter digestibility and the dry matter mass of elephantgrass pasture cv. Napier. Estimates of forage mass were accomplished monthly according to the hand plucking technique with samples being taken one day before the cows were turned into the paddocks. Forage samples were taken observing the stubble height of the pasture in the former grazing cycle. Six samples per treatment were collected from high, medium and low representative tuffs in the sampled paddocks. Samples were weighted in order to obtain the average forage yield per treatment on each grazing cycle. Forage subsamples were analyzed for chemical composition (DM, CP, NDF e ADF) and in vitro dry matter digestibility (IVDMD). Pasture was managed in a rotational grazing system of 33 days grazing cycle with three days grazing period and 30 days rest period. There were two replication units per treatment. Twenty four crossbred Holstein x Zebu cows were used, there being eight per treatment. The following treatments were studied: Elephantgrass pasture with no concentrate (T0); Elephantgrass supplemented with concentrate during the first 60 days of lactation (T60) and a 120 days of lactation (T120). Cows on treatments T60 and T120 received 1 kg of concentrate (20% CP and 70% TDN) for each 2 kg of milk above 10 kg, daily. Pasture was fertilized with 1,000 kg/ha/year of a 20:05:20 formula. There was no treatment effect on the forage chemical composition and IVDMD figures. Mean values for CP, NDF, ADF and IVDMD were: 13.6, 69.1, 39.5, and 63.8% for CP, NDF, ADF and IVDMD, respectively. There was no treatment effect on forage mass (1,480; 1,760 and 1,870 kg DM/ha) and daily forage allowance per cow (12.4; 14.7 and 15.6 kg DM/day). There was no treatment effect for milk yield averaging 11.65 kg/cow/day. However there was treatment effect for stage of lactation, which averaged 15.1, 11.6, and 8.2 kg/cow/day for 1 to 60, 60 to 120 and over 120 days, respectively.

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.

Dinâmica do perfilhamento em capim-elefante sob influência da altura do resíduo pós-pastejo

The objective of this work was to evaluate the effects of two stubble heights (50 and 100 cm) on tiller dynamics, dry mass for tiller and dry mass herbage accumulation of basal and aerial tillers in elephantgrass pastures managed under grazing. A complete randomized block design with split plot arrangement and four replications were used. The stubble heights did not influence the population density, tiller mortality and birth percentage, dry mass per tiller and herbage accumulation of basal and aerial tillers. Basal and aerial tillers showed increase of 47% and reduction of 16% on population density between spring and summer, respectively. Tillers with leaves were 92% of aerial tillers and 52% of basal tillers. Tiller birth percentage was the highest determinant of population density variations. The dry mass herbage accumulation was larger for basal tillers during spring, and the aerial tillers increased it during summer.

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 (%).

Milk yield and composition, feed intake and stocking rate of crossbread cows in tropical grasses managed in a rotational grazing system

The objective of this study was to evaluate milk yield and composition, dry matter intake, and stocking rate in pastures with tanzania grass (Panicum maximum cv. Tanzânia), star grass (Cynodon nlemfuensis cv. Estrela-Africana), and marandu grass (Brachiaria brizantha cv. Marandu). The grasses were managed in a rotational grazing system with Holstein x Zebu crossbreed cows, with a 30-day resting period and three days of paddock occupation. The pastures were fertilized with 1,000 kg/ha/year using the 20:05:20 (NPK) formula, split in three applications during the rainy season. It was used a complete random block experimental design with three factors being studied and two replications. In the experiment, four cows/paddock were used and, when it was necessary, regulator animals were added in order to obtain a supply of 7% body weight green forage dry matter. The animals were individually fed concentrate at 2 kg/day during the experimental period. Milk yield did not differ among the three grasses, with values of 9.1; 9.1; and 8.7 kg/cow/day for pastures with tanzania grass, star grass and marandu grass, respectively. Similarly, grass did not affect milk chemical composition. Stocking rate was similar among the three grasses, with values of 4.6; 4.5 and 5.0 UA/ha for tanzania grass, star grass and marandu grass, respectively. The highest dry matter intake was observed for tanzania grass with 2.6% of the body weight while stargrass (2.3%) and marandu grass (2.4%) did not differ among each other. The highest dry matter intake on tanzania grass pasture was not reflected on milk yield per animal. Milk yield and composition and stocking rate are similar among the evaluated grasses.