Raquel Rolim Cardoso

Atributos físicos do solo sob intensidades de pastejo e métodos de pastoreio com cordeiros em integração lavoura‑pecuária

The objective of this work was to evaluate possible alterations in the soil bulk density and total porosity due to lamb trampling, under different grazing management after no-tillage summer crop. The experiment was carried out in the layers 0-2.5, 2.5-5 e 5-10 cm of an arenic Ultisol, in an annual ryegrass pasture with forage allowance of 2.5 and 5.0 of animal potential consumption, under continuous and rotational stocking. An ungrazed area was used as check. Grazing intensities and methods did not affect soil bulk density and total porosity. It is possible to use areas with this kind of soil texture, with cover crops for lamb grazing in the winter, without alterations on soil physical attributes, caused by animal trampling, reach harmful levels for subsequent crops.

Quality of the forage apparently consumed by beef calves in natural grassland under fertilization and oversown with cool season forage species

The objective of this study was to evaluate the chemical composition of the forage apparently consumed by steers in a natural grassland on region of Campanha, in Rio Grande do Sul, Brazil, subjected or not to different inputs: NP - natural pasture without inputs; FNP - fertilized natural pasture and INP - improved natural grassland with fertilization and over-seeded with cultivated winter species. Three Angus steers testers and a variable number of regulator animals per experimental unit were utilized in order to maintain 13 kg of DM/100 kg of live weight (LW) as forage allowance. One time at each season, hand plucking samples were performed along the daily grazing time simulating forage harvested by the animals. The collected samples after drying and grind were submitted to chemical analysis to determine the forage quality. Except in winter and spring, the values of neutral detergent fiber were higher than the critical value of 550 g/kg of DM, which could limit forage intake, demonstrating that the values of forage on offer provided (15.6; 13.7; 13.5; 15.8 kg of DM/100 kg of LW/day in summer, autumn, winter and spring, respectively) were not restrictive to intake. The oversowing of winter cultivated species or fertilization positively alter the degradable fiber content. The seasons had marked influence on the chemical composition of forage apparently consumed; positively increasing some fractions of forage chemical composition in the seasons in which native or cultivated winter species increased their participation. The forage chemical composition is the determining factor in animal performance in natural pasture.

Recria de cordeiras em pastagem nativa melhorada submetida à fertilização nitrogenada: 2. Produção animal

Avaliou-se o desempenho de cordeiras de corte para o acasalamento no outono em pastagem nativa melhorada fertilizada com adubo mineral formula 5-20-20 (250 kg/ha). Utilizaram-se duas doses de nitrogenio (100 e 200 kg/ha na forma de ureia), fracionadas em duas aplicacoes (70% em 3 de fevereiro e 30% em 17 de marco de 2005) considerando controle piquetes sem aplicacao de nitrogenio. Os tratamentos foram distribuidos em blocos completos com duas repeticoes. O metodo de pastejo foi continuo com lotacao variavel e oferta de forragem de 16% (16 kg MS/100 kg peso vivo [PV]). O periodo de avaliacao foi de 21 de janeiro a 31 de maio. As variaveis estudadas foram taxa de lotacao, carga animal, desaparecimento de MS em %PV, ganho de peso medio diario, escore de condicao corporal, ganho de peso por area e taxa de prenhez. O desaparecimento de MS em %PV nao diferiu entre as doses de nitrogenio e os periodos de avaliacao e apresentou valores limitantes em relacao ao provavel consumo potencial. As doses de nitrogenio tiveram efeito positivo sobre a taxa de lotacao e a carga animal, que nao diferiram no decorrer das avaliacoes. O escore de condicao corporal, o ganho medio diario e o ganho de peso por area apresentaram variacoes significativas entre os periodos de avaliacao, como resultado da influencia do deficit hidrico registrado durante o periodo experimental. A taxa de prenhez nao foi influenciada pelas doses de nitrogenio. Apesar do deficit hidrico, que comprometeu negativamente as variaveis produtivas da pastagem e a resposta animal as doses de nitrogenio aplicadas, a pastagem nativa melhorada por meio de adubacao pode suportar elevadas taxas de lotacao.