Davi Teixeira dos Santos

Sistema de integração lavoura-pecuária: efeito do manejo da altura em pastagem de aveia preta e azevém anual sobre o rendimento da cultura da soja

This trial aimed to evaluate the effects of sward height management of pastures composed by black oat and Italian ryegrass upon soybean establishment and yield. The treatments were four sward management heights: 10, 20, 30 and 40cm; and no grazing control. Pasture (sward height, herbage allowance, herbage mass, stocking rate and post grazing herbage mass) and soybean (initial stand of plants and yield) attributes were evaluated. The observed sward heights were very similar to those previously intended. There was a linear increase in herbage allowance and herbage mass with increasing sward height management. Forage accumulation rate was not influenced by treatments. Stocking rate decreased linearly with increasing sward height. Post grazing herbage mass increased with increasing sward height. Treatments had effect on initial soybean stand, but soybean yield was not affected. Results suggest grazing animals do not damage succeeding crop, allowing farmers profitability enhancement by using those areas during soybean intercropping.

Produção de novilhos superprecoces em pastagem de aveia e azevém submetida a diferentes alturas de manejo

The objective of this trial was to evaluate production and carcass characteristics of young steers grazing a mixture of black oat and Italian ryegrass pasture. Treatments were four different pasture heights (10, 20, 30, and 40 cm) that were obtained with different stocking rates. Fifty-five beef steers averaging 210 kg of body weight and 10 months of age at the beginning of the trial were used in a randomized complete block design with three replicates. The observed increase in the average daily weight gain (ADG) was associated with the quality and/or amount of available forage because herbage allowance increased from 6 to 51 kg DM/100 kg BW when pasture height was enhanced from 10 to 40 cm. Therefore, the ADG was 0.73 and 1.14 kg/animal/day for the treatments with the lowest and highest ADG, which corresponds to 10 and 30 cm pasture height. Considering the low ADG, the greatest gain/area observed on the 10 cm treatment may be explained by a greater stocking rate; both ADG and stocking rate decreased linearly by increasing pasture height. Body weight and hot carcass weight increased until 30 cm of pasture height but decreased at 40 cm because of poorer pasture quality. There was no difference on carcass yield, which averaged 51% among treatments. The body condition score and carcass fat thickness followed the ADG in this trial.

Sistema de integração lavoura-pecuária: desempenho e qualidade da carcaça de novilhos superprecoces terminados em pastagem de aveia e azevém manejada sob diferentes alturas

O objetivo do experimento foi avaliar o desempenho e a qualidade da carcaca de novilhos superprecoces submetidos a alturas de manejo do pasto de aveia e azevem (10, 20, 30 e 40cm), suplementado no terco final do ciclo de pastejo. Animais jovens com idade media de dez meses e peso inicial de 190kg foram distribuidos num delineamento experimental de blocos ao acaso, com tres repeticoes. As ofertas de forragem para os tratamentos 10, 20, 30 e 40cm foram respectivamente, 8,8, 14,7, 29,0 e 48,9kg de materia seca 100kg de peso vivo-1 (PV). O ganho de peso por hectare foi superior nos tratamentos com menor altura, em decorrencia da maior carga animal, sendo obtidos para 10, 20, 30 e 40cm de altura ganhos por area de 529,7, 489,5, 320,9 e 201,6kg de PV ha-1, respectivamente. O ganho medio diario e peso ao abate apresentaram resposta quadratica (P 0,05). Novilhos superprecoces atingiram peso de abate e grau de acabamento adequados quando terminados em pastagem cultivada de inverno e suplementados no terco final do ciclo de pastejo. O melhor ganho medio diario foi obtido em altura entre 25 a 30cm, e maior producao por area quando a pastagem foi manejada a 10cm de altura.

Padrões de uso do tempo por novilhos em pastagem consorciada de azevém anual e aveia-preta

Aiming to assess the steer grazing behavior, an experiment was carried out with pastures composed by italian ryegrass (Lolium multiflorum Lam.) and black oat (Avena Strigosa Schreb) submitted to different sward heights (10, 20, 30, and 40 cm). The sward heights were distributed in an experimental randomized block design with three replicates. Data was recorded by visual assessment, from sunrise until sundown, in three evaluation dates, two in the vegetative stage and one in the reproductive stage. The evaluated variables were grazing time, rumination time, idling time, number and length of meals, and number and length of meals intervals. Results indicated that with increasing sward height the animals reduced grazing time and the meal length as well, however, the ruminating time increased. The variables such as idling time, number of meals and number/length of intervals were not influenced by the sward surface height. The results showed changes in the animal grazing behavior due to the variations in sward height management.

Eficiência bioeconômica da adubação de pastagem natural no sul do Brasil

O objetivo deste trabalho foi avaliar as producoes vegetal e animal e a resposta economica de uma pastagem natural submetida a adubacao de correcao e doses de nitrogenio durante a estacao de crescimento 1998/99. O experimento foi conduzido em area da Estacao Experimental Agronomica da Universidade Federal do Rio Grande do Sul (EEA - UFRGS). Em 1996 foram aplicados 3000kg ha-1 de calcario e adubacao correspondente a 500kg ha-1 da formula 5-20-20. Na analise economica, considerou-se um terco destas quantidades como referente a utilizacao na estacao de crescimento 1998/99. Os tratamentos foram doses de nitrogenio (N) na forma de ureia (zero, 100 e 200kg ha-1 de N), em um delineamento de blocos ao acaso com duas repeticoes de area por tratamento. Os animais experimentais foram novilhas de corte com um ano de idade e peso medio inicial de 160kg. A massa de forragem, a taxa de acumulo diario de materia seca, a producao total de materia seca verde e a eficiencia de transformacao do N em producao primaria foram maiores (P<0,1) quanto maior foi a dose de N aplicado. As aplicacoes de 100 e 200kg ha-1 de N elevaram os custos em 104,1 e 208,2%, respectivamente. A aplicacao de 200kg ha-1 de N em pastagem natural apresentou maior producao de peso vivo, margem bruta e eficiencia de conversao do N em produto animal. Quando foram utilizados apenas o calcario e a adubacao N-P-K de correcao, obteve-se o maior retorno financeiro direto. A pastagem natural mostrou resposta positiva a aplicacao de fertilizantes, dentro da amplitude de quantidade destes insumos aplicadas no presente trabalho.

Relações planta-animal em ambiente pastoril heterogêneo: padrões de desfolhação e seleção de dietas

The experiment was conduced to evaluate the effect of different native pasture structures, represented by four sward heights (4, 8 12 and 16 cm) on defoliation and selectivity patterns of calves and ewes, in 45-minute grazing tests. A completely randomized design with four treatments and two replicates in time and space were used. Sward structure was characterized by sward height, herbage mass, leaf blade mass, herbage bulk density, leaf blade bulk density, and number and length of fully-emerged and emerging leaves. Forty tillers were marked in each experimental unit to determine the number and length of leaf blade. Defoliation and selectivity patterns were evaluated by defoliation probability and by passive selectively (PS) and active selectively (AS) indexes. A positive correlation between sward height and herbage mass, and negative between sward height and herbage bulk density were observed. Above 4 cm, leaf blade was almost exclusive, meaning optimal conditions for herbage intake by the animals. A reduction in the defoliation probability was observed with increasing sward height due to a lower stocking rate/available forage relationship. PS and AS were negatively affected by sward height. PS did not differ between calves and ewes, and above 6.7 cm, animals consumed less emerging leaf blade in relation to fully-emerged leaf blade. However, it did not mean that animals fail to select leaf blade, since AS remained above reference value 1 for both animal species. Ewes differed from calves in terms of AS. The increase in sward height affects the opportunity of animals to find emerging leaf blade, however, they selected younger leaf blade in the attempt to obtain a better food quality. Ewes selected emerging leaf blade more effectively than calves.

Ganho de peso de novilhas em pastagem nativa da Serra do Sudeste do RS submetida ao controle de plantas indesejáveis e intensidades de pastejo

This work aimed to evaluate the effect of different undesirable plants controlling methods and grazing intensities on animal production in native pastures. The treatments were no control (T), spring clipping (P), autumn clipping (O) and chemical control (Q), under two levels of forage allowance, medium (8%) and high (14%), expressed in kg of dry matter offered daily per each 100kg of liveweight. The experimental design was a completely randomized block arranged in a factorial with two repetitions. Statistical analysis showed no interaction among treatments nor differences among control methods for variables concerning primary and secondary production (P>0.1). Animal performance in both forage allowances was not different (P>0.1). High forage allowances increased animal performance per unit area (P<0.1).

Recria de cordeiras em pastagem nativa melhorada submetida à fertilização nitrogenada: 1. Dinâmica da pastagem

It was evaluated the effect of nitrogen fertilization (100 and 200 kg/ha of N as urea) on the components of forage production of an improved native pasture with 3.12 ha (paddocks - 0.52 ha). Control areas without application of N were used, using a complete block design with two replications. Paddocks were grazed by lambs in a continuous stocking and variable stocking rate to keep forage allowance of 16% LW. In spring of 2004, pasture was uniformly fertilized with 250 kg/ha of 5-20-20 and N doses were applied during experimental period (summer 2005). Total forage on offer and rate of forage disappearance were not affected by treatments nor the periods of evaluation. Total herbage mass diminished significantly with time and was affected by N doses as function of the accumulation verified prior to the experimental period. All other studied variables showed no significant effect of N due to water deficit. There was no herbage accumulation during the first part of experimental period and accumulation rate only became positive in the last half period. As consequence, herbage height and herbage mass diminished significantly with time. Green forage mass showed inverse behaviour in relation to dead material percentage. The quadratic response of this later component was initially characterized by high values that diminished by the final period with the reestablishment of normal rainfall. By this reason, the green forage allowance was very low and interacted in time with N doses. Volumetric density presented low values when compared to values previously observed in this kind of pasture. However, a tendency for higher values was verified at the end of the observations period. The herbage height and herbage mass presented high correlation (r = 0.87) indicating that herbage height can be a good estimator of herbage mass, in these conditions. In the situation of water deficit, nitrogen fertilization does not contribute to the expression of more intense responses of the studied variables.

Fluxo de biomassa aérea em azevém anual manejado sob duas intensidades e dois métodos de pastejo

The trial was conducted to evaluate the influence of two grazing intensities (moderate and low) and two stocking methods (continuous and rotational stocking) in the aerial biomass fluxes of an Italian ryegrass measured by the fluxes of growth, senescence, and intake, using the marked tillers technique. It was used a factorial arrangement in a complete randomized block design with four replicates per treatment. Treatments and their interactions affected the fluxes of growth and senescence. Rotational stocking at low intensity favored the growth flux of the pasture. Senescence flux was greater at continuous stocking and low intensity and the intake flux was not affected by the treatments.

Caracterização da estrutura da vegetação numa pastagem natural do Bioma Pampa submetida a diferentes estratégias de manejo da oferta de forragem

Os objetivos neste trabalho foram descrever e investigar a dinâmica espaco-temporal de sitios alimentares em diferentes faixas de massa de forragem e altura do pasto, assim como o percentual de area efetivamente pastejada, a taxa de acumulo de forragem e a producao de materia seca de uma pastagem natural do Bioma Pampa. O delineamento utilizado foi o de blocos ao acaso com duas repeticoes, com tres ofertas de forragem fixas (8, 12 e 16%) e tres ofertas de forragem variaveis ao longo do ano (8-12%, 12-8% e 16-12%), com o primeiro valor correspondendo a primavera. Na oferta fixa de forragem de 8%, observou-se maior percentual de area efetivamente pastejada, porem os valores medios de altura e massa de forragem foram inferiores aos das demais ofertas. As maiores ofertas de forragem, 16 e 16-12%, apresentaram altura media do pasto superior, 9,0 cm e massa de forragem de 2.000 kg/ha de materia seca, porem, com area efetivamente pastejada inferior as observadas nas ofertas de 8 e 8-12%. Mesmo estrategias de manejo tao distintas, aproximadamente 60 a 70% dos sitios alimentares ocorreram em faixas consideradas limitantes ao potencial de ingestao de forragem por bovinos, com excecao dos tratamentos 16% e 16-12%, nos quais se observou menor frequencia de sitios alimentares na faixa inferior a 6,0 cm de altura. Os sitios alimentares, em geral, se concentraram em faixas com altura <6 cm e massas de forragem <1000 e 1000-1500 kg/ha de materia seca em todas as ofertas de forragem avaliadas, porem, nas ofertas de 16-12% e 8-12%, ocorreu uma melhor distribuicao dos sitios alimentares nas demais faixas de massa de forragem e altura do pasto.