Forage evaluation indices are available to assist farmer decision‐making on the most appropriate ryegrass cultivars to grow. However, these indices currently take no account of any feeding value ...trait that reflects the interaction between the animal and the structural and morphological characteristics of the pasture. Information on the feeding value of ryegrass cultivars can be confounded by nutritive value, arising from the relationship between nutritive value and heading date. The objective of this study was to determine the milk production response of dairy cows grazing four perennial ryegrass diploid cultivars: two morphologies within two different heading dates and on three occasions during lactation across two years: late spring, summer and autumn. No consistent phenotypic effect occurred on milk production across the two years. Milk production responses were more closely aligned to energy intake. The sward structure changed physiologically from year 1 to year 2, with a reduction in the ratio of leaf to stem and subsequent increase in stem mass in year 2. Despite this, the relative difference in leaf to stem between mid‐season and late‐season heading dates remained consistent between years and had no effect on milk production. In one year, the apparent dry‐matter intake was higher but it was not possible to determine which sward structure traits or group of traits contributed to this response. We conclude that, at this time, the evidence is insufficient to support inclusion of a phenotypic trait as represented by “feeding value” in forage evaluation indices.
Highly digestible forages are associated with an
in vitro
low-methane (CH
4
) rumen fermentation profile and thus the possibility of reducing CH
4
emissions from forage-based systems. We aimed to ...assess the
in vitro
ruminal fermentation profile, including CH
4
production, of the top stratum of Kikuyu grass (
Cenchrus clandestinus - Hochst. ex Chiov
) harvested at different sward heights (10, 15, 20, 25, and 30 cm). Herbage samples (incubating substrate) were analyzed for their chemical composition,
in vitro
organic matter digestibility (IVOMD), and morphological components.
In vitro
incubations were performed under a randomized complete block design with four independent runs of each treatment. Gas production (GP),
in vitro
dry matter digestibility (IVDMD), CH
4
production, total volatile fatty acid (VFA) concentration, and their acetate, propionate, and butyrate proportions were measured following 24 and 48 h of incubation. Herbage samples had similar contents of organic matter, neutral detergent fiber, and crude protein for all treatments. However, a higher acid detergent fiber (ADF) content in taller sward heights than in smaller sward heights and a tendency for metabolizable energy (ME) and IVOMD to decrease as sward height increased were found. Similarly, the stem + sheath mass tended to increase with increasing sward height. Amongst the nutrients, ME (
r
= −0.65) and IVDMD (
r
= −0.64) were negatively correlated with sward height (
p
< 0.001) and ADF was positively correlated with sward height (
r
= 0.73,
p
< 0.001). Both the GP and IVDMD were negatively related to the sward height at both incubation times. Sward heights of Kikuyu grass below 30 cm display an
in vitro
profile of VFAs high in propionate and low in acetate, with a trend toward lower methane production of CH
4
per unit of IVDMD. These findings are important to aid decision-making on the optimal sward height of Kikuyu grass and manage animal grazing with the opportunity to reduce CH
4
production.
Thus study was conducted with the objective of evaluating production and forage characteristics of Signalgrass (Brachiaria decumbens cv. Basilisk) deferred at different initial heights and nitrogen ...doses. Three initial sward heights (low - 10 cm, medium - 20 cm and high - 30 cm), three nitrogen doses (40, 80 and 120 kg/ha) and a control treatment, of no fertilization were evaluated. The experimental design utilized was of completely randomized blocks with three replications, in a subdivided-plot arrangement. There was no interaction between sward initial height and nitrogen dose for the variables analyzed. The Signalgrass deferred at an elevated initial height presented greater masses of forage, live stem, dead stem and dead leaves; higher percentage of dead stem and falling rate; and lower number of vegetative tillers, percentage of live leaves and live leaf/live stem ratio. Elevation in the nitrogen dose increase along with the number of live and vegetative tillers; masses of forage, live stem, dead stem, dead leaves and live leaves; percentage of live stem; and live tissue/dead tissue ratio; and reduced the percentage of dead leaves and the live leaf/live stem ratio. Signalgrass can be deferred at low and medium initial heights and varied nitrogen doses, according to the objectives and possibilities of the farmer.
The use of forage legumes has been proposed as a means of generating sustainable grazing environments. Their limited use, particularly in tropical pastures, is partially due to the limited knowledge ...regarding the efficiency of utilization by animals. The present study characterized the sward structure, nutritive value and ingestive behaviour of dairy heifers in pastures of peanut cv. Belmonte under continuous stocking management. Treatments corresponded to sward heights of 5, 10, 15 and 20 cm, according to a randomized complete block design, with four replications. The following response variables were evaluated: vertical distribution of the morphological components within the sward, forage mass, nutritive value (simulated grazing), bite rate (BR), bite mass (BM) and short-term herbage intake rate (STIR). The top half of the sward height was mainly composed of leaves and the bottom half mainly of stolon and dead material regardless of management height. Greater values of neutral detergent fibre and acid detergent fibre were recorded during autumn, while higher values of in-vitro dry matter (DM) digestibility (0·85) occurred during spring regardless of management height for the grazed stratum. In relation to treatments, greater values of crude protein were recorded on swards managed at 5 cm (0·27) and 10 cm (0·26). Bite rate, BM and STIR varied with sward height, but not with a season of the year. The STIR followed a broken line response to sward height, with increasing values up to 13·1 cm (106 g DM/kg body weight). Sward structure played an important role in determining the STIR. To maximize the STIR of dairy heifers under continuous stocking management, swards should be managed at heights of not <13·1 cm.
Despite all the biotic and abiotic factors affecting foraging by ruminants, there is a common and fundamental process, which is bite gathering. We hypothesised that because the mechanics of bite ...formation dominate the foraging process, changes in short-term bite mass are reflected in longer-term animal performance across a wide range of sward conditions. We focus at the meal level of foraging, using experiments in which the effect of abiotic factors and digestive constrains are minimised, making intake rate the main currency. We estimated bite mass across a wide range of structural challenges to large-herbivore foraging in a long-term experiment with heterogeneous native grasslands. A conceptual model was developed for average daily gain, where energy gain and energy costs were proximate causal variables. Energy gain was a function of diet quality and components of daily intake rate, where bite mass was the main component estimated. In turn, components of intake rate were determined by sward structure and bodyweight. Energy costs were a function of bodyweight and abiotic conditions. Finally, sward structure, bodyweight and abiotic conditions were determined by experimental treatments, seasons and years. Then, the conceptual model was translated into statistical models that included variables measured or estimated, and coefficients representing all links in the conceptual model. Weight gain was a function of bite mass, forage characteristics, and animal and abiotic conditions. Models were set up to test whether forage and stocking conditions affected monthly gain beyond the effects through bite mass, after correcting for abiotic factors. Forage mass, height and disappearance did help predict monthly gain after bite mass was included in the model, which supported our hypothesis. However, stocking treatments and season had significant effects not incorporated in bite mass. Although the model explained 77.9% of liveweight gain variation, only 35.2% was due to fixed effects, with 10.8% accounted by bite mass and its interactions. Concomitant experiments showed that sward structure (first with sward height and the second with tussock cover) does determine bite mass and short-term intake rate in the complex native grasslands we studied. Yet, other temporal varying components of monthly gain not correlated with bite mass, temperature or wind, added most of the observed variation in monthly animal performance. Part of the model failure to account for variation in performance may be related to a significant and temporally variable grazing of tussocks. We used a bite mass model that assumed no tussock grazing. In light of these results and a parallel experiment, we conclude that tussock grazing must be incorporated in future versions of the model.
ABSTRACT The objective of this study was to evaluate the effects of Brachiaria brizantha cv. Marandu syn. Urochloa brizantha cv. Marandu (Marandu palisadegrass) in late winter on pasture structure, ...apparent selectivity, and sheep production during spring and early summer. The conditions of deferred pastures at the end of winter were: low (15.1cm and 4600kg/ha of DM), medium (23.2cm and 5940kg/ha of DM), high (31.4cm and 7640kg/ha of DM) and high/mowed (31.3cm and 7200kg/ha of DM, mowed to 8cm). The experiment was conducted in split plot design (sward conditions at the end of winter: low, medium, tall and tall/lowered) during time (early, middle and late spring/summer) and completely randomized design with three replications. The percentages of live leaf laminae in available forage and in simulated grazing samples were higher in tall/lowered sward and lower in high sward, oppositely to percentage of dead tissue. Only at the beginning of the grazing period the high/lowered sward had lower forage mass and bulk density. This remained high in high sward during all the grazing period. The sheep performance and the animal production per area were higher in low sward and lower in tall swards. The low sward has better structure and higher sheep production starting at spring. The lower of the marandu palisade grass at late winter improves this structure and increases sheep production during spring and early summer.
RESUMO Objetivou-se avaliar os efeitos da condição do pasto diferido de Brachiaria brizantha cv. Marandu syn. Urochloa brizantha cv. Marandu (capim-marandu) no fim do inverno sobre a estrutura do pasto, a seletividade aparente e a produção de ovinos durante a primavera e o início do verão. As condições dos pastos diferidos no fim do inverno foram: baixo (15,1cm e 4.600kg/ha de MS), médio (23,2cm e 5.940kg/ha de MS), alto (31,4cm e 7.640kg/ha de MS) e alto/roçado (31,3cm e 7.200kg/ha de MS, rebaixado para 8cm). O experimento foi conduzido em esquema de parcela (condições dos pastos ao fim do inverno: baixo, médio, alto e alto/roçado) subdividida no tempo (início, meio e fim da primavera/verão) e delineamento inteiramente ao acaso, com três repetições. Os percentuais de lâmina foliar viva na forragem disponível e na amostra de simulação de pastejo foram maiores no pasto alto/roçado e menores no pasto alto, contrariamente ao percentual de tecido morto. Apenas no início do período de pastejo, o pasto alto/roçado apresentou menores massa e densidade volumétrica de forragem. Esta se manteve alta no pasto alto durante todo o período de pastejo. No início do período de pastejo, os pastos apresentaram pior composição morfológica na FD. O desempenho dos ovinos e a produção animal por área foram maiores no pasto baixo e menores no pasto alto. O pasto baixo, no fim do inverno, apresenta melhor estrutura e maior produção de ovinos a partir da primavera. A roçada do pasto de capim-marandu no fim do inverno melhora sua estrutura e aumenta a produção animal durante a primavera e o início do verão.
The objective was to evaluate the grazing behavior and the spatial distribution of feces of F1 young bulls from the cross between Nellore and Guzera on pastures of Urochloa brizantha cv. Marandu in ...silvopastoral systems composed of babassu palm (Attalea speciosa) and Marandu monoculture in the Pre-Amazon region of the state of Maranhão. Animals were evaluated in four systems consisting of 0, 80, 131, 160 palms ha-1, characterizing monoculture (mono), low density of palm trees (LD), medium density of palm trees (MD) and high density of palm trees (HD) during the rainy (RE) and dry (DE) periods. Five animals (repetitions) were used in each system, with 231-303 days of age and 180±15 kg body weight. Determinations of behavioral patterns were made by instant sampling, at 10 min intervals. In each system, we demarcated 50 squares of 100 m2, which served as useful area to evaluate the dispersion of feces. The grazing behavior was influenced by the sward structure, which, in turn, was influenced by densities of palm trees, due to shading. The distribution of feces was affected by both the presence of babassu plantations and periods. The silvopastoral systems made the environment more pleasant to animals, since activities considered more stressful and avoided during the daytime were performed by animals of these environments, unlike animals in the monoculture system.
A definição dos princípios adequados de manejo do pastejo capazes de possibilitar que as pastagens mantenham-se produtivas e persistentes tem sido uma preocupação constante dos pesquisadores ...brasileiros. No entanto, foi durante as duas últimas décadas que ocorreram grandes mudanças e um avanço significativo na compreensão dos processos determinantes da correta utilização das plantas forrageiras tropicais em pastagens. Este texto tem por objetivo apresentar e discutir os principais resultados obtidos sobre o manejo do pastejo de alguns cultivares de Panicum maximum e de Brachiaria brizantha, bem como a importância da utilização de metas de pasto como guia de campo para o monitoramento e controle do processo de pastejo para planejar e recomendar práticas de manejo eficientes.
Sward architecture mediates ruminant grazing behavior in temperate grazing lands. Temperate grasses differ in their sward structure, which may influence the grazing behavior of cattle. We determined ...relationships between the grazing behavior of dairy heifers and the sward structure of the following temperate grasses: meadow fescue (Schedonorus pratensis (Huds.) P. Beauv.), orchardgrass (Dactylis glomerata L.), quackgrass (Elymus repens (L.) Gould), and reed canarygrass (Phalaris arundinacea L.). Vegetative-stage grasses were rotationally grazed by Holstein heifers (average initial body weight of 460 kg) during 5 day periods in the spring, summer, and fall of 2007 and 2008. The herbage dry matter (DM) allowance was twice the expected daily intake (11 kg DM animal−1 d−1). The sward characteristics were measured before grazing (e.g., the herbage height and mass, vertical distribution of leaf and stem fraction, and nutritive value). The grazing behavior of the heifers was quantified using automatic jaw movement recorders. In this study, the grass species had little effect on the grazing behavior. However, the bite rate was negatively correlated with the herbage mass, while the number of bites was positively correlated with the sward height and herbage mass. These results suggest that when herbage availability is not limited, grazing dairy heifers exhibit similar ingestive and rumination behavior across grass species and seasons, yet jaw movement dynamics may respond to the different characteristics of the swards. The results of this study provide the following benefits: (1) they inform managers about the jaw movement mechanics that can be expected of dairy heifers in temperate forage systems, showing that they are not limited by herbage allowance, and (2) they provide insight for future studies that employ on-animal sensors to evaluate foraging dynamics and animal performance outcomes in temperate forage pasture systems.
RESUMO Objetivou-se compreender o efeito do período de diferimento sobre a seletividade aparente de bovinos pelos componentes morfológicos e de valor nutritivo do pasto de Brachiaria decumbens cv. ...Basilisk. Adotaram-se o esquema de parcela subdividida e o delineamento em blocos ao acaso com duas repetições. Foram estudados quatro períodos de diferimento (73, 103, 131 e 163 dias) e duas amostras de forragem (disponível na pastagem (DP) e obtida pela simulação de pastejo (SP)). As percentagens de lâmina foliar viva (LFV), matéria seca potencialmente digestível (MSPD) e proteína bruta (PB) foram maiores na amostra de SP, quando esta foi comparada à forragem DP. Padrão de resposta contrário ocorreu com os percentuais de colmo vivo (CV), colmo morto (CM) e fibra em detergente neutro (FDN). De modo geral, o maior período de diferimento resultou em pior composição morfológica e valor nutritivo das forragens. Os índices de seletividade aparente (ISA) da LFV, do CV e da lâmina foliar morta (LFM) aumentaram linearmente com o período de diferimento. O ISA do CM apresentou maiores valores em pastos sob períodos intermediários de diferimento. Com o aumento do período de diferimento, os ISA da FDN e da MSPD permaneceram constantes, os ISP da FDN potencialmente digestível e da PB reduziram linearmente, e o ISP da FDN indigestível incrementou de maneira linear. O ISA permite a compreensão da seletividade dos componentes morfológicos e das entidades nutricionais do pasto pelos bovinos. A redução do período de diferimento melhora a estrutura do pasto e otimiza a seletividade dos bovinos.
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