Two experiments were conducted to examine the interrelationships between body composition at parturition, herbage allowance during lactation and milk production. Detailed measurements of feed intake and changes in body composition allowed estimates of maintenance energy requirement and efficiency of use of energy for milk production. Dorset ewes were offered low (L-) or high (H-) herbage allowances during pregnancy to achieve post-partum body weights, respectively, of about 50 and 60-65 kg. During the first 6 weeks of lactation herbage allowances were approximately 2 (-L), 5 (-M and -Mm) and 8 (-H) kg DM/ewe/d and feed intake was determined using chromic oxide dilution. In the first experiment (Expt.A) ewes were machine-milked and in the second (Expt.B) they were suckled by twin lambs with a further group (-Mm) machine-milked. Samples of ewes were slaughtered during early pregnancy, post-partum, and after 6 weeks of lactation. Body weight differences post-partum between L- and H- groups were 10 and 15 kg in Expts.A and B respectively. During lactation body weight changes appeared erratic, particularly in Expt.B, owing to the effects of variation in gut fill. Daily feed intake of machine-milked ewes on -M and -H allowances reached a maximum (1.9-2.2 kg OM/ewe/d) 2-3 weeks after parturition but ewes rearing lambs on similar allowances showed maximum intake (2.5-2.8 kg OM/ewe/d) during the first week. Mean intakes during lactation were 58, 69 and 73 g DOM/kg W•⁷⁵/d respectively for -L, -M and -H groups machine-milked and 51, 75 and 83 g DOM/kg W•⁷⁵/d respectively for -L, -M and -H groups rearing twin lambs. In both experiments ewes in L- groups had approximately 14% greater mean intake (g DOM/kg W•⁷⁵/d) during lactation compared with those in H- groups. Mean daily milk production of ewes rearing lambs was 2.0, 2.5 and 2.7 kg/d respectively in -L, -M and -H groups and was 33-52% greater than that for machine-milked ewes offered similar herbage allowances. In both experiments L- ewes had 14% greater milk yield (g/kg W•⁷⁵/d) compared with H- ewes. Mean lamb growth rates in Expt.B averaged 209, 254 and 268 g/lamb/d in -L, -M and -H groups, respectively. Lambs in the H- group were approximately 11% heavier at birth than those in the L- group and their mean growth rate was 20 g/d greater. Body fat and energy content of live ewes at the start of lactation was predicted using regression relationships from ewes slaughtered post-partum. There was large variation in the energy content of body weight loss during lactation (-37 to +140 MJ/kg) owing to variation in weight of gut fill and changes in chemical composition of the empty body. In Expt.A the body fat content of ewes during early pregnancy was 16.9 kg. Predicted values post-partum were 10.0 and 15.7 kg in L- and H- groups, respectively. During lactation all groups showed body fat losses which ranged from 53 (LH) to 120 g/d (HL). Body fat content during early pregnancy in Expt.B was slightly greater (19.0 kg) than in Expt.A and predicted values post-partum were 11.5 (L-) and 19.7 kg (H-). Fat mobilization during lactation was greater than in Expt.A, and ranged from 157 (LH) to 287 g/d (HL). In both experiments there were losses in body protein during pregnancy in L- ewes (5 and 15 g/d in Expts.A and B respectively). During lactation, protein losses were most evident in H- ewes, being greatest in HL groups (26 and 43 g/d in Expts.A and B respectively). Water: protein ratio in the empty body showed a progressive increase during pregnancy and lactation in both experiments. Estimated maintenance energy requirement for machine-milked ewes tended to be greater for H- (.236 MJ ME/kg W/d) compared with L- ewes (.205 MJ ME/kg W/d) but was similar for both groups of ewe rearing lambs (average of.238 MJ ME/kg W/d). Efficiency of use of ME above maintenance for milk production (K₁) in L- and H- groups was, respectively, .69 and .95 in machine-milked, and .69 and .64 in suckled ewes. Energy from mobilized body tissues was utilized for milk production with respective efficiencies in L- and H- ewes of .23 and .35 in machine-milked, and .40 and .50 in suckled ewes. Efficiency of conversion of total energy available (i.e. ME above maintenance and mobilized tissue energy) to milk energy (K₁(t)) when compared among all groups in both experiments, tended to decrease (from .84 to .51) with increasing body energy mobilization. There was a positive relationship, however, between K₁(t) and the proportion of mobilized energy derived from body protein. Metabolizable energy intakes in the present experiments appeared to be 10-15% greater than calculated requirements from ARC (1980). Estimates of ME requirements for lactating ewes at pasture, in relation to body weight, level of milk production and body energy change, have been calculated based on the present data.

The influence of beef cattle pasture on the composition of pasture herbage was studied in Šumava region (Kaplice, 550 {--} 850 m a.s.l) from 2005 to 2006. Also was studied the effect of different nanagement of permanent grassland on its composition plantation form and non-producing functions. On the pasture herbage dominated grass and leguminous species. On the fallow land prevailed herb species. On the combined management site (pasture and harvest) was established higher frequency of Taraxacum officinale, Trifolium pratense and Dactylis glomerata

Na natureza, durante milhares de anos de convivência, gramíneas forrageiras e herbívoros passaram por um processo de co-evolução desenvolvendo múltiplas estratégias de sobrevivência e de adaptação. Práticas de manejo que interferem na forma como a forragem é disponibilizada aos animais (estrutura do dossel forrageiro) podem causar mudanças dos padrões de procura e ingestão de forragem e interferir com o desempenho animal. Nesse contexto, o objetivo deste estudo foi avaliar a estrutura do dossel forrageiro e a taxa de consumo de forragem em pastos de capim-elefante cv. Napier (Pennisetum purpureum Schum.) submetidos a estratégias de pastejo rotativo. O experimento foi conduzido em área da Escola Superior de Agricultura \"Luiz de Queiroz\", Piracicaba, SP, de janeiro de 2011 a abril de 2012. Os tratamentos corresponderam a combinações entre duas condições pós- (alturas pós-pastejo de 35 e 45 cm) e duas condições pré-pastejo (95% e máxima interceptação de luz pelo dossel forrageiro - IL), alocados às unidades experimentais (piquetes de 870 m²) segundo arranjo fatorial 2x2 e delineamento de blocos completos casualizados, com quatro repetições. Foram avaliadas em pré- e em pós-pastejo as seguintes variáveis-resposta: distribuição vertical dos componentes morfológicos da massa de forragem dos pastos, taxa de bocados, massa do bocado, taxa de consumo e valor nutritivo da forragem consumida (composição morfológica e bromatológica de amostras de extrusa).A estrutura do dossel influenciou fortemente a massa do bocado, a taxa de bocados e a taxa de consumo independente de tratamento e época do ano. Em pré-pastejo, apesar de a massa do bocado ter sido maior nos pastos manejados com a meta ILMáx, não houve diferença em taxa de consumo entre as metas de IL avaliadas, resultado da maior taxa de bocados registrada nos pastos manejados com a meta IL95%. Em pós-pastejo a taxa de consumo também não variou entre as metas de IL avaliadas, sendo observados ajustes na taxa de bocados como forma decompensar as variações em massa do bocado. As metas de altura pós-pastejo modificaram a composição morfológica e bromatológica da forragem consumida, as quais variaram também em função da época do ano. De maneira geral, pastos manejados com a meta IL95% e altura pós-pastejo de 45 cm resultaram em maior porcentagem de folhas na extrusa, o que conferiu melhor taxa de consumo e valor nutritivo da forragem consumida pelos animais em pastejo. / In nature, during thousands of year of co-existence, forage grasses and herbivores underwent a co-evolution process that resulted in multiple survival strategies and adaptations. Management practices that interfere with the way forage is presented to animals (sward structure) may cause changes in patterns of search and consumption of herbage, affecting animal performance. The objective of this experiment was to evaluate sward structure and rate of herbage intake of rotationally stocked elephant grass (Pennisetum purpureumSchum., cv. Napier). The experiment was carried out at Escola Superior de Agricultura \"Luiz de Queiroz\", Piracicaba, SP, Brazil, from January 2011 to April 2012. Treatments corresponded to combinations between two post- (post-grazing heights of 35 and 45 cm) and two pre-grazing swards conditions (95% and maximum canopy light interception - LI), and were allocated to experimental units (870 m2 paddocks) according to a 2x2 factorial arrangement in a complete randomised block design, with four replications. The following response variables were evaluated in both pre- and post-grazing conditions: vertical distribution of morphological components of sward herbage mass, bite rate, bite mass, rate of intake and nutritive value of the consumed herbage (morphological and chemical composition of extrusa samples). Sward structure strongly influenced bite mass, bite rate and rate of intake regardless of treatment and season of the year. At pre-grazing, in spite of the larger bite mass on swards managed with the pre-grazing target LIMax, there was no difference in rate of intake between LI targets, consequence of the higher bite rate recorded on swards managed with the pre-grazing target LI95%. At post-grazing, there was no difference in rate of intake between LI targets, with variations in bite rate used to compensate variations in bite mass. Post-grazing targets altered the morphological and chemical composition of the consumed herbage, which also varied with season of the year. Overall, swards managed with the pre-grazing target LI95% and the 45 cm post-grazing height resulted in larger percentage of leaves in the extrusa, favouring higher rates of intake and nutritive value of the herbage consumed.

Sistemas integrados têm sido apontados como alternativas ecologicamente apropriadas para recuperar a produtividade de pastagens tropicais degradadas, gerando benefícios tanto para o meio ambiente como para os animais. Apesar das diversas vantagens atribuídas aos sistemas integrados, existem ainda limitações técnicas que dificultam a otimização do processo produtivo, função da natureza complexa e multidisciplinar das interações entre seus componentes bióticos e abióticos. Existem, portanto, aspectos importantes que podem comprometer a produtividade do sistema, entre eles, as alterações na estrutura do dossel forrageiro e a menor produção de forragem, principalmente pela diminuição da radiação luminosa que chega ao sub-bosque. Partindo da hipótese que o dossel arbóreo irá determinar a quantidade e a qualidade de luz disponível para o sub-bosque e, assim, influenciar a estrutura do dossel forrageiro e a produção de forragem do capim-piatã manejado sob pastejo rotativo utilizando metas de interceptação luminosa (IL) prépastejo, o objetivo deste trabalho foi avaliar as características estruturais e o acúmulo de forragem de Brachiaria brizantha cv Piatã em sistema ILPF de dezembro de 2013 a julho de 2014. O estudo foi desenvolvido por meio de três experimentos realizados de forma concomitante para avaliar três regimes de luz: (1) capim-piatã cultivado em área livre de árvores (pleno sol; PS); (2) sombreamento gerado por meio de fileiras duplas de Eucalipto nas bordaduras dos piquetes (S1); e (3) sombreamento gerado por meio de quatro renques de fileiras triplas de Eucalipto dispostos dentro dos piquetes de forma alternada com porções de pasto (S2). Os regimes de luz S1 e S2 foram divididos em duas faixas de sombra (central e lateral) para descrição da variação da luz dentro dos piquetes e sua implicação sobre o padrão de crescimento das plantas. O período experimental foi dividido em três períodos de avaliação em função do índice pluviométrico registrado. Para estudar a influência das árvores sobre a medição de IL e sua implicação sobre o crescimento das plantas, o regime S2 foi manejado utilizando-se dois métodos de tomada da leitura de referência da luz incidente: leitura dentro (sob a copa das árvores) e fora (luz natural na ausência de árvores) da área experimental. Foram avaliadas as seguintes variáveis-resposta: altura, massa de forragem e sua composição morfológica, índice de área foliar, ângulo da folhagem, interceptação luminosa do dossel forrageiro, umidade do solo, índice de nutrição nitrogenada, taxa de acúmulo e produção de forragem. Os resultados indicaram que pastos sombreados possuíam altura 30% maior que pastos não sombreados, com colmos mais longos e delgados. A massa de forragem em pré-pastejo diminuiu com o aumento do nível de sombreamento e a composição morfológica se manteve praticamente estável entre os regimes luz. As mudanças morfológicas e estruturais resultaram em redução das taxas de acúmulo e da produção de forragem em torno de 50% no regime S1 e de 65% no regime S2 relativamente ao regime PS. O conjunto de resultados obtidos revela claramente que as metas de altura pré-pastejo desenvolvidas com base na condição de 95% de IL em pleno sol não podem e não devem ser utilizadas em sistemas integrados com árvores, especialmente aqueles em que a densidade de árvores é elevada, necessitando que metas específicas sejam produzidas para o manejo do pastejo naquelas condições. / Integrated production systems, such as the agrosilvopastoral systems, have been considered ecologically adequate alternatives in restoring the productivity of degraded tropical grasslands, as they generate benefits for both the environment and the grazing animals. Despite several advantages associated with the integrated systems, there are technical constraints that limit their optimization, due to the complex and multidisciplinary nature of the interactions between its biotic and abiotic components. In this context, there are important aspects that must be considered and that might influence the system\'s productivity, including changes in sward structure and herbage production due to decreased light availability under the trees. Based on the hypothesis that in a silvopastoral pastoral system the tree canopy determines the quantity and the quality of the light available for forages growing under the trees, and that this affects sward structural characteristics and herbage accumulation of rotationally grazed Piatã brachiariagrass managed using pre-grazing targets of canopy light interception during regrowth, the objective of this study was to evaluate the structural characteristics and the herbage accumulation of Brachiaria brizantha cv. Piatã in a crop-livestock-forest integration area from December 2013 to July 2014. The study comprised three simultaneous experiments to evaluate three light regimes: (1) Piatã brachiariagrass cultivated in the absence of trees (full natural light; PS); (2) shade produced by a double row of Eucaliptus trees on the edges of the paddocks (S1); and (3) shade produced by four triple rows of Eucaliptus with pasture in between them (S2). The S1 and S2 light regimes were divided into two shade strips (central and lateral) in order to describe the variation in light availability within the paddocks and its implications to plant growth. The experimental period was divided in three evaluation periods according to rainfall. In order to evaluate the influence of the trees on the measurement of sward canopy light interception and its implications on grass growth, paddocks under the S2 light regime were managed using two methods for taking the reference readings of the incident light: reading inside (under the tree canopy) and outside (full natural light) the experimental area. The following response variables were analyzed: sward height, herbage mass and plant-part composition, sward leaf area index, foliage angle, canopy light interception, soil moisture, grass nitrogen nutrition index, herbage accumulation rates and total herbage yield. The results indicate that shading, results in taller swards (30% increase in sward height pre-grazing) with longer and thinner stems. Pre-grazing herbage mass decreased with increasing shade levels and plant-part composition remained relatively constant across light regimes. Morphological and structural changes resulted in approximately 50 and 65% decrease in herbage accumulation rates and herbage yield under the S1 and S2 light regimes, respectively, in relation to PS. Pre-grazing target sward height recommendations based on the 95% canopy light interception under full light conditions are not suitable for integrated systems with trees, particularly those where tree density is high, emphasizing the need to devise specific management targets for use under those conditions.

Fodder from lasting grass growths serves from 80% to fed ruminants. Therefore is setting high emphasis on quality fodder from trifolium, grass and trifolium-grass growths. On this account fit itrodukcion try in these growths imply at full blast useful kinds plants (trifolium), which have improving effects on fodder. Once of these improving products is also Lathyrus pratensis. His introduction increases substitution legumin in lasting meadow growths and share rhizobial nitrogen on production knows - nose fodder and nutritive valuable degestible nitrogen factory materials. Occurrence Lathyrus pratensis is impressed with type herbal growth and his differential management.

O experimento foi conduzido na FZEA/USP – Pirassununga/SP de dezembro de 2002 a março de 2003, em uma área de 26,7 ha formada de capim-braquiarão. O objetivo foi avaliar as características morfofisiológicas durante a fase recuperação da planta forrageira após o pastejo. A pastagem foi submetida a quatro intensidades de pastejo representadas por níveis de oferta de forragem (5, 10, 15 e 20% - kg MS/100 kg peso animal.dia), utilizando-se o método de lotação rotacionada, sendo sete dias de ocupação e vinte e oito dias de descanso. O delineamento experimental foi em blocos completos e casualizados, com quatro repetições. Foram avaliadas as seguintes respostas: (1) características morfogênicas: intervalo de aparecimento foliar (IApF), taxa de aparecimento foliar (TApF), taxa de alongamento foliar (TAlF), taxa de senescência foliar (TSenF), taxa de alongamento de colmo (TAlC); e (2) características estruturais: número de folhas vivas por perfilho (NFVP), comprimento de folhas verdes por perfilhos (CFVP), comprimento médio de folhas verdes por perfilho (CMFVP) e comprimento de colmo (CC), dinâmica de perfilhamento, englobando, percentagem de perfilhos decapitados (PPD), número de perfilhos basais remanescentes (NPBR), número de perfilhos aéreos remanescentes (NPAR), número de perfilhos basais novos (NPBN), número de perfilhos aéreos novos (NPAN), densidade populacional de perfilhos (DPP), peso médio de perfilho seco, (PMPS) e peso médio de perfilho verde (PMVP). Pastagens submetidas a menor intensidade de pastejo apresentam maior TSenF. As condições climáticas que favorecem o processo de florescimento foram determinantes nessa TSenF. O avanço na estação de crescimento interferiu de forma negativa na TApF, aumentando automaticamente o IApF. A TAlF teve pouca influência dos tratamentos de OF, exceto na condição inicial de manejo, período de avaliação 1 (PAv.1). Nos PAv. o aumento do NFVP esteve relacionado com a diminuição de seu comprimento médio. O CC aumentou com o avançar dos PAv. A maior intensidade de pastejo condicionou o aumento na PPD, a maior DPP e o menor PMPS e PMPV. As condições climáticas tiveram papel importante na sobrevivência e aumento dos NPBR nos PAv.. A sobrevivência dos NPAR esteve condicionada aos efeitos da OF. Condições de maior intensidade de pastejo favoreceu o aparecimento de NPBN e NPAN. No avançar dos PAv., o pastejo leniente provocou diminuição do surgimento do NPAN, embora tenham aumentado durante o período de rebrotação. / The experiment was conducted in the FZEA/USP - Pirassununga/SP from December/2002 to March/2003, in a pasture of signal grass of 26.7 ha. The objective was evaluated the morphophysiological characteristics during regrowth of the plant after grazing. The pasture was submitted at grazing intensities represented by four levels of herbage allowance (5, 10, 15 and 20% - kg DM/100 kg weight animal.day), using rotational stocking method, being seven days of occupation and twenty and eight days of interval of grazing. The experimental design was in complete randomised block, with four replications. The evaluated responses were: (1) morphogenetics characteristics: leaf appearance interval (LApI), leaf appearance rate (LApR), leaf elongation rate (LElR), leaf senescence rate (LSenR), stem elongation rate (SElR); e (2) structural characteristics: number of live leaves (NLL), length of green leaf (LGL), length average green leaf (LAGL) and length of stems (LS), dynamics of tillering, percentage of decapitated tiller (PDT), number of remaining basal tiller (NRBT), number of remaining aerial tiller (NRAT), number of new basal tiller (NNBT), number of new aerial tiller (NNAT), population density of tiller (PDT), dry average weight for tiller, (DAWT) and green average weight for tiller (GAWT). Pasture submitted to lenient grazing presented higher LSenR. The climatic conditions that favour flowering process were determinant in LSenR. The advance in growth station influenced negatively in the LApR and increased automatically the LApI. The HA had little influence on the LAIR, except in the initial condition of management, period of evaluation 1 (PAv.1). In the PAv. the increase of the NLL was related with the reduction of its average length. The LS increased with advancing of the PAv.. The highest grazing intensity conditioned the increase in the PDT, the biggest PDT and lowest DAWT and GAWT. The climatic conditions were important in the survival and increase of the NRBT in the PAv.. The survival of the NRAT was conditioned to the effect of the HA. The highest grazing intensity favoured the appearance of NNBT and NNAT. With the advance of the PAv., the lenient grazing provoked reduction of the NNAT emergence, even so has increased during regrowth period.

O presente experimento foi conduzido na Unidade Experimental de Plantas Forrageiras (UEPF) em área do Departamento de Produção Animal da ESALQ/USP, em Piracicaba (SP), entre 01/07/98 e 31/12/98. Os tratamentos consistiram de combinações entre três cultivares de Cynodon spp. (Tifton-85, Florakirk e Coastcross) e quatro intensidades de pastejo (5, 10, 15 e 20 cm) estabelecidas por ovinos em regime de lotação contínua. O delineamento experimental foi o de blocos completos casualizados com quatro repetições e parcelas sub-divididas, onde na parcela foram alocados os cultivares e na sub-parcela as intensidades de pastejo. Foram analisadas as seguintes variáveis: índice de área foliar, interceptação luminosa, acúmulo de matéria seca e composição botânica/morfológica dos pastos. Tifton 85 mostrou os maiores valores de IAF para qualquer das intensidades de pastejo estudadas. As taxas de acúmulo de matéria seca foram semelhantes em todos os tratamentos. Tifton 85 apresentou como faixa ótima de uso condições de pasto que variaram de 5 a 15 cm. Já para Florakirk essa faixa foi até 20 cm e para Coastcross o limite superior deve ser maior que 20 cm. De maneira geral os diferentes cultivares devem possuir requerimentos variados de manejo de desfolha quando o objetivo é o uso eficiente da luz e demais fatores de crescimento associado a elevados índices de utilização da forragem produzida. / The present trial was carried out at the Pasture and Grazing Studies Unit, Animal Production Department, ESALQ/USP, Piracicaba, State of São Paulo, from July 1 until December 31, 1998. Treatments comprised the possible combinations between three Cynodon spp. cultivars (Tifton-85, Florakirk and Coastcross) and four grazing intensities (5, 10, 15 and 20 cm) imposed by sheep under a continuous stocking management. Treatments allocation to experimental units followed a completely randomised block design with four replications and a split-plot arrangement. Grass cultivars were allocated to plots and grazing intensities to sub-plots. The responses studied were leaf area index (LAI), light interception, herbage dry matter accumulation and swards' botanical composition. Tifton-85 showed the highest LAI for any of the grazing intensities used. Herbage dry matter accumulation rates were similar for all treatments. Tifton-85 presented a narrower range of sward conditions for grazing management (5 to 15 cm) when compared to Florakirk (5 to 20 cm) and Coastcross (5 to > 20 cm). Overall, different grass cultivars presented different grazing management requirements in situations where efficient use of light and high levels of herbage utilisation are targeted.

Herbage and cattle production in semi-arid regions are primarily controlled by climate variation particularly rainfall variability and secondarily by disturbances such as drought, grazing and fire. These factors interact at different spatial and temporal scales in a complex manner difficult to observe or comprehend and, reduce availability and quality of herbage and cattle productivity. Variables for quantifying rangeland productivity are thus rarely available and unreliable yet options for sustainable management are limited. Grazing experiments have provided useful insight about ecological and management factors involved in rangeland functioning, but they have limited scope to deal with high environmental variation. This highlights the need for a systems approach for monitoring rangeland and cattle productivity at the appropriate spatial and temporal scales to enable productivity to be maximised whilst risk to climate variation is minimised. This study explored two broad objectives: to determine the ranch-scale impacts of rainfall variability and drought on herbaceous aboveground biomass (AGB) using optical remote sensing; and to parameterise, evaluate and apply a systems model, the Sustainable Grazing Systems (SGS) whole farm model to complement grazing experiments in assessing the effects of grazing strategies on beef cattle production. To determine rainfall variability impacts, twenty regression models were firstly developed between measured herbaceous AGB and, classical and extended multispectral vegetation indices (MVIs) derived from a Landsat 8 image. End-of-season herbaceous AGB was predicted with high accuracy (r2 range = 0.55 to 0.71; RMSE range = 840 to 1480 kgha-1). The most accurate model was used to construct a regression between rainfall and AGB derived from peak-season Landsat images available between 1992 and 2017. Standardised precipitation index and standardised anomalies of herbaceous AGB production were then used in a convergence of evidence approach to determine the response of AGB to rainfall variability and drought intensity. Total wet season rainfall revealed high variability (33 to 41 % CV) and subsequent herbaceous AGB production were 18 to 35 % more variable. Spatial heterogeneity of AGB production across herbaceous communities were high and deviated from mean AGB by 51 to 69 %. Landscape-level temporal variation of AGB production remained stable despite the increase of climate variability experienced in the region in the past 50 years. Climate inputs and parameter sets for upper-, mid- and foot- slope land types and key grass species, Urochloa mosambicensis and Eragrostis curvula were developed by integrating spatial data with previous soil surveys and extensive reviews of published experiments. A simulation experiment was conducted between 1992 and 2017 for all combinations of land types and grass species to analyse the extent of improvement resulting from parameter adjustments. The SGS model predicted the growth pattern known for grasses native to dry regions of southern Africa. The model represented measured herbaceous biomass moderately well (r2 = 0.57), at low average error (RMSE, 820 kg DM ha-1) despite huge discrepancies in summary statistics for measured (mean, 3877 kg DM ha-1) and simulated (mean, 3071 kg DM ha-1) biomass and residuals. Model predictions were also significantly correlated with remotely sensed AGB (r2 = 0.46) at reasonable overall performance error (RMSE, 981 kg DM ha-1). The integrated workflow developed for parameterising and calibrating the SGS pasture-simulation model can benefit model users in data-constrained environments. Animal growth parameters specific to Brahman weaner steers were defined in the SGS model to enable evaluation of impacts of recommended (10 haLU-1) and other three stocking rates (7, 15 and 20 haLU-1) and multi-paddock grazing systems (2-, 3- and 4- paddocks per herd) on rangeland productivity. Overall, there were no observable differences in herbage production and dry matter intake irrespective of stocking rate and multi-paddock grazing system. But stocking rate effects on animal production were more pronounced compared to multi-paddock grazing systems. To maximise cattle productivity in semi-arid rangelands, management should be emphasised on manipulation of stocking rates over multi-paddock grazing systems. Keywords Rangeland monitoring, climate risk, sustainability, animal productivity, grazing strategies / Thesis (PhD (Animal Production Management))--University of Pretoria, 2020. / National Research Foundation of South Africa / University of Pretoria Department of Research and Innovation Support / Animal and Wildlife Sciences / PhD / Unrestricted

This study compares insect and cattle consumption of crested wheatgrass (Agropycon spp.) on a site in Sterling Ranch, Utah County, Utah. The hypothesis tested is that insect consumption in general, and specifically consumption by Labops hesperius Uhler, significantly reduces total available cattle forage. Labops and grasshoppers were probably the major cause of secondary damage at the study site, while the impact of thrips is unknown. A detrimental impact on range was suggested by the data, as insects consumed forage equivalent to 2.8 animal units per month, while cattle consumed forage equivalent to 2.1 animal units per month at the study site. Based on a grazing fee of $1.60 per animal unit per month, this represents a loss of $3.50 per acre. Although a low level Labops population was present at the time of the study, potential exists for this population to reach higher level s that would cause much higher levels of damage. Crested wheatgrass, the major vegetation at the study site, is capable of resuming growth in the fall if there is sufficient moisture. Because there is only one generation of Labops per year, fall herbage production would not suffer Labops damage, but may suffer damage by other insects that are present in the fall.

No description available.