Edna Nunes Gonçalves

Relações planta-animal em ambiente pastoril heterogêneo: processo de ingestão de forragem

Com o objetivo de avaliar o efeito da estrutura de uma pastagem nativa nos parâmetros que compoem o processo de ingestao de forragem de ovelhas e bezerras em pastejo, foram estabelecidas quatro alturas de pasto (4, 8, 12 e 16 cm), em delineamento estatistico inteiramente casualizado, com quatro tratamentos e duas repeticoes no tempo e no espaco. A massa do bocado e a taxa de ingestao foram estimados por diferenca de peso vivo corrigido para a perda de peso metabolico, durante 45 minutos. Os movimentos mandibulares de apreensao e mastigacao foram registrados pelo aparelho IGER Behaviour Recorder. A profundidade do bocado foi obtida em 40 perfilhos marcados por unidade experimental, em medicoes realizadas antes e apos o pastejo. Observou-se correlacao positiva entre a altura do pasto e a massa de forragem, e negativa com a densidade de forragem. A profundidade de bocados apresentou relacao linear e positiva com o aumento da altura do pasto e nao diferiu entre especies animais. Acima de 9,5 cm de altura do pasto, a profundidade do bocado das ovelhas nao compensou a pouca densidade de forragem nos estratos mais superiores, o que reduziu a massa do bocado. A mesma resposta foi observada a partir da altura do pasto de 11,4 cm para as bezerras. Com o aumento da massa do bocado, houve diminuicao na taxa de bocados e aumento na taxa de mastigacao. A taxa de ingestao foi maior nas alturas em que a massa de bocados foi tambem superior, o que evidencia a correlacao positiva entre as duas variaveis. Nessas condicoes, para aumentar o consumo de ovelhas e bezerras em campo nativo, a estrutura ideal de manejo requer manutencao de altura do pasto entre 9,5 e 11,4 cm, respectivamente.

Relações planta-animal em ambiente pastoril heterogêneo: padrões de deslocamento e uso de estações alimentares

This study assessed how the displacement patterns and feeding station used can be affected by sward heights of 4, 8, 12 and 16 cm. A randomized complete design was used with two replication in time and space. The animals were evaluated by 45- minute grazing tests, to determine the number of bites, number of feeding stations and number of steps using counters, except for number of bites, which was registered by the IGER Behaviour Recorder device. A positive correlation was observed between sward height and herbage mass, and negative correlation between sward height and herbage bulk density. Differences between female calves and ewes were observed in all variables evaluated. The number of feeding station per minute decreased quadratically with increasing sward height. The number of bites per feeding station and time per feeding station increased quadratically with increasing sward height and were affected negatively by the lower herbage bulk density in the upper strata of the higher sward heights. Female calves, at 12 cm sward height, carried out more bites per feeding station and remained longer at each feeding station. The same behaviour was observed for ewes at 8 cm sward height. As less feeding stations were used, as a response to the previous variables, the animals walked more with slower steps. Thus, at sward heights between 8 and 12 cm the animals remained more time grazing each feeding station and covered longer distances searching for new grazing sites.

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.

Variáveis morfogênicas e estruturais de azevém anual (Lolium multiflorum Lam.) manejado sob diferentes intensidades e métodos de pastejo

Um experimento foi conduzido com o objetivo de avaliar a influencia de intensidades e metodos de pastejo nas caracteristicas morfogenicas (taxa de elongacao de folhas, taxa de surgimento de folhas, tempo de vida da folha) e estruturais (numero de folhas verdes, comprimento de folhas e densidade populacional de perfilhos) de azevem em dois ciclos de avaliacao. Os tratamentos experimentais consistiram de duas intensidades e dois metodos de pastejo (continuo e rotacionado), em um delineamento em blocos completamente casualizados, em arranjo fatorial com quatro repeticoes. Foram marcados 30 perfilhos por unidade experimental. As intensidades de pastejo foram responsaveis pelas diferencas encontradas na taxa de elongacao de folhas (intensidade baixa resultou em maior taxa de elongacao) e nas caracteristicas estruturais (intensidade baixa resultou em menor densidade populacional de perfilhos, maior comprimento e maior numero de folhas vivas por perfilho). Os metodos de pastejo influenciaram as caracteristicas morfogenicas (o pastejo continuo resultou em maior taxa de elongacao de folhas, mais alta taxa de surgimento e maior tempo de vida das folhas no primeiro ciclo de observacao) e estruturais (o pastejo continuo resultou em maior densidade populacional de perfilhos). Observou-se interacao intensidades de pastejo x ciclos de avaliacao. A forma de conducao do processo de desfolhacao, por meio do controle de intensidades e metodos de pastejo, afeta as caracteristicas morfogenicas e estruturais da pastagem.

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.

Manejo do milheto em pastoreio rotativo para maximizar a taxa de ingestão por vacas leiteiras

This study aimed to evaluate the effects of rotational grazing strategies on the dynamics of the grazing pastures of millet (Pennisetum glaucum (L.) R. Br.) grazed by dairy cows. Treatments consisted of two pre-grazing heights (60 and 40cm) and two post-grazing heights (20 and 10cm) allocated in a randomized block design with four replications. The sward height was evaluated during grazing every 10 minutes. The rate of grazing down of the sward height of the pasture on the 40-20 grazing strategy was relatively constant throughout the grazing down. Treatment 60-10 showed the largest decline in the rate of grazing down. The rate of grazing down in the 40-10 treatment decreased with a slower intensity when compared to the treatments with 60cm of pre-grazing sward height. The major intake rates were observed in treatments with pre-grazing sward height of 60cm. The best management strategy was considered the combination of 60-20cm of sward height.

Componentes do processo de pastejo de cordeiros em azevém sob diferentes intensidades e métodos

The aim of this study was to evaluate the components of lamb grazing process in ryegrass pastures (Lolium multiflorum Lam.). The treatments were two grazing intensities: moderate and low (forage suply: 2.5 and 5-fold the animal intake potential, respectively) in rotational and continuous stocking. The experimental design was a randomized complete block arranged in a factorial with three replicates (2 intensities x 2 methods x 3 replicates). There was no interaction among grazing intensities and methods, and its effects were analyzed separately. There was no difference of herbage allowance between grazing methods (p= 0.3393), and so, the basic conditions to compare all treatments were reached. Herbage mass during the experiment were: 3159 and 2327 kg of DM/ha for rotational and continuous stocking; and 1971 and 3514 kg of DM/ha for moderate and low grazing intensities, respectively. There was no significant differences for number of meals (M), meal duration (MD), inter meals intervals (IMI), duration of intervals (DI), grazing time (GT), ruminating time (RT) and idling time (IT) (p>0.1) for grazing methods. There was no statistical difference for RT, M, MD and IMI (p>0.1) regarding grazing intensities. DI, GT, IT, bite rate (BR) and time for feeding station (TFS) were affected by grazing intensity (p<0.1). Grazing methods affected just BR and TFS (p<0.1) due to the higher herbage mass under rotational stocking. The use of correct grazing intensities for the animals, more than the choice between grazing methods, is capital to built sustainable grazing environments aiming the production of high quality lambs.