Behavioural mechanisms of intake rate by heifers grazing swards of contrasting structures

Ecophysiology of C4 Forage Grasses—Understanding Plant Growth for Optimising Their Use and Management

“…For Cynodon spp. the decrease occurs at a faster rate because succeeding layers of herbage are more restrictive to bite formation than for Sorghum bicolor [128]. Similar results were reported for Brachiaria brizantha cv.…”

“…As grazing progresses and herbage mass decreases towards the end of grazing, the proportions of stem and dead material increase in the consumed herbage as the consequence of the changing plant-part composition of the sward vertical profile [129][130][131]. This pattern of variation in the short-term rate of intake in relation to the decreasing sward height during grazing was formally described by Fonseca et al [127,132] and corroborated by Mezzalira et al [128], indicating the potential for manipulating pre-and post-grazing conditions as a means of optimising herbage production and intake in rotationally managed pastures. In general, more frequent defoliations (at 95% canopy light interception) than traditionally used, associated with moderate grazing severity (post-grazing heights around 50% of the pre-grazing height), result in greater leaf dry matter production [84,93,96,124], higher nutritive value [89,90] and intake rate of animals [127][128][129]132], augmenting animal performance and productivity [133], indicating that rational intensification of grassland use could be an effective way of ensuring sustainability of tropical pastoral systems of animal production.…”

“…This pattern of variation in the short-term rate of intake in relation to the decreasing sward height during grazing was formally described by Fonseca et al [127,132] and corroborated by Mezzalira et al [128], indicating the potential for manipulating pre-and post-grazing conditions as a means of optimising herbage production and intake in rotationally managed pastures. In general, more frequent defoliations (at 95% canopy light interception) than traditionally used, associated with moderate grazing severity (post-grazing heights around 50% of the pre-grazing height), result in greater leaf dry matter production [84,93,96,124], higher nutritive value [89,90] and intake rate of animals [127][128][129]132], augmenting animal performance and productivity [133], indicating that rational intensification of grassland use could be an effective way of ensuring sustainability of tropical pastoral systems of animal production. These results are in line with the findings of Knoke et al [134] and provide feasible options for recovering degraded areas, reducing pressure on forest lands and releasing additional area for cropping and food production.…”

Acúmulo De Forragem Durante O Período De Ocupação Dos Animais Em Pastos Sob Lotação Intermitente

“…colmos ao longo do processo de rebaixamento da pastagem (9) , estrutura que impõe dificuldades ao processo de forrageamento pelos animais (10)(11)(12)(13)(14) e que podem ter sido inadvertidamente tocados durante a leitura das alturas, gerando valores subestimados da profundidade de pastejo. Adicionalmente, um fator interessante que pode ter contribuído para esse problema foi o comportamento dos animais, que pastejaram principalmente áreas próximas as cercas divisórias, deixando áreas rejeitadas (por fezes, urina e pisoteio) na área central das faixas.…”

A grazing height target to minimize tiller stem elongation rate in annual ryegrass swards

“…Thus, the stem elongation process might be an inevitable condition, even under low herbage mass conditions (low forage volumetric density, as observed by MIGUEL et al, 2012), without the occurrence of high levels of competition for light. Moreover, recent studies have shown that instantaneous herbage intake rate is maximized when pastures are grazing down at levels of defoliation of 40% of initial height (FONSECA et al, 2012;MEZZALIRA et al, 2014), regardless of grass specie. Thus, despite of leaf production being relatively constant from 15 to 25cm, it seems that sward heights targets around 20cm in annual ryegrass would be a compromise between high leaf production with high herbage intake rates, since on using higher pre-grazing heights ----------------------Height (cm)-----------------------------------Effects---------------------------15 1 ------------------------25 1 ---------- Ciência Rural, v.46, n.1, jan, 2016. the remaining stubble after grazing would present a great amount of stems that will become progressively larger in subsequent regrowth, which could lead to a deterioration in sward structure with negative impact for herbage intake and production.…”