Seasonal Patterns of Herbage Accumulation Dynamics in Marandu Palisadegrass Subjected to Intensities of Continuous Stocking Management

It is relatively well reported in the literature that pastures can have similar forage net accumulation when managed with contrasting structures. However, we hypothesized that the patterns of forage accumulation dynamics of pastures managed at different canopy heights is dependent on environmental conditions. The experimental treatments were four canopy heights (10, 20, 30, and 40 cm), allocated to experimental units according to a randomized complete block design with four replicates and evaluated throughout four contrasting environmental seasons (Summer, Autumn, Winter-Early Spring, and Late Spring). Under favourable growing conditions greater forage accumulation was observed in pastures maintained taller; on the contrary, under more stressful conditions, net forage accumulation rate reduced as canopy height increased. Such patterns of responses were related to compensations between tiller population density and tissue flows during summer and late spring and the reduced capacity of taller canopies to compensate lower population with greater growth rates during autumn and winter-early spring. Pastures subjected to intensities of continuous stocking management change their patterns of forage growth as they transitioned from favourable to more abiotic stressful conditions suggesting that warm-season perennial grasses demand seasonal adjustments in grazing heights in order to maximize herbage production

Morphophysiological Adaptations of \u3cem\u3eBrachiaria humidicola\u3c/em\u3e Cultivars under Grazing

Pastures of Brachiaria humidicola are broadly used in Brazil, especially in soils with low fertility and poor drain-age (Valle et al. 2010). Currently, 3 cultivars are commercially available: Tully, Llanero and BRS Tupi (available since 2012). Despite the extensive use of this species, research has focused primarily on aspects related to herbage and animal production, while only a few studies aimed at understanding morphological adaptations of the plants when subjected to grazing and contrasting environmental conditions. Therefore, the aim of this work was to evaluate some morphological traits of 2 B. humidicola cultivars when continuously stocked during 2 seasons of the year

State of Knowledge in Tiller Dynamics

Persistence of sown pastures is a concern for pastoral production worldwide. Fundamentally, when a pasture does not persist the problem can be expressed in terms of inadequate new tiller production or excessive tiller death. However, the collection of data to build an understanding of sward dynamics at this level is time consuming. Tiller survival diagrams are presented for a range of temperate and tropical grass species including Lolium perenne, Lolium multiflorum, Festuca arundinacea, Festuca pratensis, Phleum pratense, Bromus willdenowii, Cynodon dactylon, Brachiaria brizantha, Panicum maximum, Chloris gayana and Paspalum notatum. It is shown that each grass has a unique perennation strategy and accordingly unique strengths and weaknesses that confer persistence or lack of persistence in different situations. There is also confusion in extension circles about the trade-off between tiller size and tiller density and how to detect a suboptimal tiller density. Grass swards respond to high herbage mass by increase of tiller size and reduction in tiller density, but reduction in tiller density is often mistaken for sward decline. A distinctionmust be made between size/density compensation and sward decline. Increased understanding of sward dynamics at this level should help in the evolution of management practices that improve persistence on a range of grassland types

Short-Term Herbage Intake Rate in Temperate Pastures Grasses Grown in Pure or in Intercropping Stands

Oat and ryegrass pastures grown in intercropping systems are the most common forages used during the fall and winter in subtropical and in some temperate climate regions. Nevertheless, it must be taken into account that the way in which the different species of plants are presented to the animals may lead to consequences for the efficiency of the grazing process (Prache and Damasceno 2006). Moreover, in hetero-geneous environments, animals may reduce intake rate due to a partial preference for a specific species (Gonçalves et al. 2009). Regarding the pasture development stage, it is known that the decrease of the leaf/stem ratio causes the animal to reduce the instantaneous herbage intake rate due to the reduction of the bite depth because of the physical barrier imposed by the stem (Benvenutti et al. 2006; Drescher et al. 2006) and/or the search for a higher food quality, in this case, leaf lamina (Soder et al. 2009). However, the dynamics of changes in temperate sward structures grown in pure stands compared to inter-cropping systems and its consequence in heifers\u27 short-term herbage intake rate (STHIR) are scarce. The objective of this work was to assess the changes in the STHIR in pastures of oat, ryegrass and their intercrop during the growing season. The hypothesis tested was that cattle reduce the STHIR in intercropping pastures compared to pure stands, and as the grazing season progress

Tiller Size/Density Compensation in Temperate Climate Grasses Grown in Monoculture or Intercropping Systems under Rotational Grazing

From the standpoint of tiller population dynamics, it is well known that the size and numbers of tillers in forage grasses are inversely related, where a greater tiller population density (TPD) is associated with smaller tillers and vice versa (Sbrissia et al. 2003; Hernandez-Garay et al. 1999; Matthew et al. 1995). This relationship has traditionally been made with the self-thinning power law described by Yoda et al. (1963), which considers the leaf area index (LAI) of the pasture constant when the slope of the relationship between numbers and size of tillers, on a logarithmic scale, is approximately -3/2 (Matthew et al. 1995). Notably few studies have assessed this relationship in intercropping systems. Moreover, although studies that evaluated intercrops showed relationships that were nearly -3/2 for the individually analysed species (Yu et al. 2008; Nie et al. 1997;White and Harper 1970), Nie et al. (1997) suggested that all plants that occur in the grass field should be used to properly estimate self-thinning in mixed species pastures. Thus, the aim of the present study was to test the main hypothesis that the tiller size/density compensation mechanisms operate in the same way in mixed pastures of oat and Italian ryegrass under rotational grazing and that the plant communities adapt their population to maintain a relatively constant LAI

State of knowledge in tiller dynamics

Persistence of sown pastures is a concern for pastoral production worldwide. Fundamentally, when a pasture does not persist the problem can be expressed in terms of inadequate new tiller production or excessive tiller death. However, the collection of data to build an understanding of sward dynamics at this level is time consuming. Tiller survival diagrams are presented for a range of temperate and tropical grass species including Lolium perenne, Lolium multiflorum, Festuca arundinacea, Festuca pratensis, Phleum pratense, Bromus willdenowii, Cynodon dactylon, Brachiaria brizantha, Panicum maximum, Chloris gayana and Paspalum notatum. It is shown that each grass has a unique perennation strategy and accordingly unique strengths and weaknesses that confer persistence or lack of persistence in different situations. There is also confusion in extension circles about the trade-off between tiller size and tiller density and how to detect a suboptimal tiller density. Grass swards respond to high herbage mass by increase of tiller size and reduction in tiller density, but reduction in tiller density is often mistaken for sward decline. A distinctionmust be made between size/density compensation and sward decline. Increased understanding of sward dynamics at this level should help in the evolution of management practices that improve persistence on a range of grassland types.La persistencia de los pastos sembrados es una preocupación para la producción pastoril a nivel mundial. Fundamentalmente, cuando una pastura no persiste, el problema puede expresarse en términos de producción inadecuada de nuevos macollos o muerte excesiva de macollos. Sin embargo, la recopilación de datos para comprender la dinámica de los céspedes a este nivel requiere mucho tiempo. Se presentan diagramas de supervivencia de macollos para una variedad de especies de pastos templados y tropicales que incluyen Lolium perenne, Lolium multiflorum, Festuca arundinacea, Festuca pratensis, Phleum pratense, Bromus willdenowii, Cynodon dactylon, Brachiaria brizantha, Panicum maximum, Chloris gayana y Paspalum notatum. Se muestra que cada pasto tiene una estrategia de perennación única y, en consecuencia, fortalezas y debilidades únicas que le confieren persistencia o falta de persistencia en diferentes situaciones. También existe confusión en los círculos de extensión acerca de la compensación entre el tamaño de los retoños y la densidad de los retoños y cómo detectar una densidad de retoños subóptima. Las praderas de hierba responden a una gran masa de forraje mediante el aumento del tamaño de los macollos y la reducción de la densidad de los macollos, pero la reducción de la densidad de los macollos a menudo se confunde con la disminución del césped. Se debe hacer una distinción entre la compensación de tamaño/densidad y la disminución del césped. Una mayor comprensión de la dinámica de los pastos a este nivel debería ayudar en la evolución de las prácticas de gestión que mejoran la persistencia en una variedad de tipos de pastizales.Estación Experimental Agropecuaria PergaminoFil: Matthew, Cory. Massey University. Institute of Agriculture and Environment; Nueva ZelandiaFil: Agnusdei, Monica Graciela. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; ArgentinaFil: Assuero, Silvia G. Universidad Nacional de Mar del Plata; ArgentinaFil: Sbrissia, André F. Santa Catarina State University; BrasilFil: Scheneiter, Jorge Omar. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Silva, Sila C. da. Universidade de Sao Paulo; Brasi

Fatty Acid Profile of Elephant Grass Pastures with Different Grazing Heights

Ruminant milk and meat are a source of CLA and omega-3 in the human diet and these fatty acids (FAs) have a beneficial effect on human health (Mcguire and Mcguire 2000). The increase in CLA and omega-3 in ruminant products is mainly related to proportion of C18:2 and C18:3 in the animal feed, like forage and to incomplete ruminal biohydrogenation (Bauman et al. 2000). Evaluation of FAs have been performed in temperate forage pastures, without the interaction of animal grazing, and presenting samples collected at ground level and at fixed re-growth intervals or seasons as the main sampling criteria. Therefore, the objective of this study was to evaluate the proportion of fatty acid in strata of elephant grass cv. Pioneiro with different grazing heights

Tiller Population Density and Sward Stability of Brachiaria brizantha Continuously Stocked by Cattle

Tiller population density is one the most important parameters of sward structure and its evaluation is normally included in studies of sward dynamics. Moreover, a greater level of understanding is achieved when the survival of successive tiller generations is monitored. (Matthew et al., 2000). This would help to explain seasonal variation in tiller populations based on tiller appearance and death rates. While Brachiaria brizantha c.v. Marandu occupies up to 70 million hectares of cultivated grassland in Brazil, little is known of its ecophysiology. The objective of this work was to calculate survival probability of B. brizantha tillers and identify seasonal variation on sward stability

Herbage Intake and Animal Performance of Cattle Grazing \u3cem\u3eBrachiaria brizantha\u3c/em\u3e cv. Marandu Under Continuous Stocking

Grazing management affects sward structure, which in turn influences plant and animal responses. With the objective of understanding causal relationship between sward structure and animal responses, the present experiment evaluated the daily herbage intake and live weight gain of growing cattle on Brachiaria brizantha cv. Marandu pasture during summer (Dec. 2001 to Mar. 2002)

Grazing Management Flexibility in Pastures Subjected to Rotational Stocking Management: Herbage Production and Chemical Composition of Kikuyu-Grass Swards

Several recent papers published on tropical pastures have pointed out that under rotational stocking management regrowth should be interrupted when canopy light interception is 95% (LI). Further, these studies have revealed a positive and high correlation between LI and sward height, allowing LI management targets to be defined in terms of sward height. However, there are some indications that lower pre-grazing heights relative to those targets would result in similar leaf accumulation without interfering with sward persistence. The objective of this paper was to verify a possible flexibility of such pre-grazing height targets. A replicated experiment was conducted with treatments corresponding to four pre-grazing height targets (25 cm, corresponding to a canopy light interception of 95%; 20; 15 and 10 cm), which were associated with a single severity of grazing equivalent to removal of 50% of initial height, leaving four post-grazing heights (12.5, 10.0, 7.5 and 5 cm, respectively). Preliminary results indicated that there were no differences in rate of herbage accumulation, herbage yield and crude protein, NDF and ADF contents on swards managed with the pre-grazing targets of 15, 20 and 25 cm. Swards managed with the 10 cm pre-grazing target had the highest contents of CP and lowest contents of NDF and ADF, but herbage accumulation was reduced. Overall, the findings indicate that there may be some flexibility in targets of pre-grazing sward height, provided that defoliation severity is moderate and does not interfere with herbage yield and quality. In that context, targets of pre-grazing sward height defined in terms of canopy light interception would correspond to the maximum value of the possible range of values to be used