A necessidade da redução do custo de produção animal nas propriedades rurais está se tornando crucial para a sobrevivência destes no mercado. Para a geração de alternativas viáveis de redução de custo é necessária a intensificação das pesquisas nos pontos de estrangulamento dos sistemas de produção animal baseados em pastagens. O uso de espécies de alto potencial forrageiro como a alfafa (Medicago sativa L.), pode ser uma opção para melhorar a produtividade de forragem e o desempenho animal, pois estes são capazes de associar elevada produção ao alto valor nutritivo. De março de 2001 a fevereiro de 2002, foi estudado o efeito do método de pastejo sobre a produtividade e o valor nutritivo de cinco genótipos de alfafa com aptidões contrastantes. O experimento do tipo “mob-grazing” foi realizado em área do Departamento de Zootecnia da ESALQ/USP, em Piracicaba, SP. O delineamento experimental foi o de blocos completos casualizados, com parcelas subdivididas (split-plot), com 10 tratamentos e seis repetições. Nas parcelas foi alocado o fator de tratamento relativo ao método de pastejo (“lotação contínua”, simulada por desfolhas semanais, e “lotação rotacionada” com desfolha a cada 4 semanas na primavera-verão e a cada 6 semanas no outono-inverno). Nas sub-parcelas foram alocados os cinco genótipos de alfafa com diferentes aptidões agronômicas em termos de dormência, procedência e tolerância ao pastejo (ABT-805, Alfagraze, Crioula, CUF-101 e Pioneer 5432), submetidos a 295 dias de pastejo e sob irrigação. ABT-805 foi o genótipo mais produtivo sob lotação contínua (26,6 Mg MS ha -1 ) e no pastejo rotacionado (18 Mg MS ha -1 ). Alfagraze, apesar de ser um dos menos produtivos no pastejo rotacionado (13,3 Mg MS ha -1 ) apresentou semelhante produtividade ao ABT-805 no pastejo sob lotação contínua (26,3 Mg MS ha -1 ano -1 ). Pioneer 5432 situou-se numa condição intermediária, com uma produção total de forragem de 24,3 e 15,3 Mg MS ha -1 sob lotação contínua e rotacionada, respectivamente. O valor nutritivo da planta inteira mostrou variação em função ao método de pastejo, enquanto que entre os genótipos que não se verificou diferença. O método de lotação contínua apresentou valores superiores de proteína bruta (PB) e digestibilidade in vitro da matéria seca (DIVMS) (349 e 810 g kg -1 , respectivamente) em comparação a lotação rotacionada (238,5 e 757,8 g kg -1 , respectivamente). Os teores de fibra apresentaram comportamento inverso, sendo que a lotação continua foi inferior (240 g kg -1 fibra em detergente neutro, FDN, 182 g kg -1 fibra em detergente ácido, FDA e 34,9 g kg -1 lignina) à lotação rotacionada (325 g kg -1 FDN, 255 g kg -1 FDA e 50,6 g kg -1 lignina). A haste apresentou o mesmo padrão na composição químico-bromatológica que a planta inteira, onde o método de lotação contínua apresentou respostas superiores às da lotação rotacionada. A folha foi a fração que apresentou maiores variações nos teores de PB, FDA e lignina além da DIVMS em função dos parâmetros experimentais estudados (método de pastejo, estação e genótipo). ABT-805 e Alfagraze são os que apresentaram maiores produtividades com adaptação moderada ao pastejo nas latitudes tropicais do Brasil Central, mas para o seu sucesso deve-ser relevar as condições climáticas e do método do manejo do pastejo. / The need for reduction in animal production costs on farms has become crucial to their survival in the market. In order to generate new alternatives research is needed on the factors that limit the success of pasture-based animal production systems. The adoption of species with high forage potential such as alfalfa (Medicago sativa L.), may be a viable option to improve forage productivity and animal performance, associating high production with high nutritive value. From March 2001 to February 2002 the effect of grazing method and genotype on forage productivity and nutritive value was studied. A mob-grazing experiment was carried out at ESALQ/USP in Piracicaba, SP. The experimental design was a randomized complete block with six field replications in a split-plot arrangement. The grazing method factor (continuous stocking, simulated by defoliation every seven days, and rotational stocking, simulated by defoliation every four weeks during the summer season and every six weeks during the winter season) was allocated at random to main plots which were grazed down to 7 cm at every grazing event. The alfalfa genotypes were allocated to the sub-plots, each of which representing a specific combination among agronomic characteristics regarding dormancy class, origin, and grazing tolerance (ABT-805, Alfagraze, Crioula, CUF-101, and Pioneer 5432). Plots were grazed over 295 days without water deficits, as sprinkler irrigation was provided as needed. ABT-805 was the most productive genotype under continuous (26,6 Mg DM ha -1 ) and rotational (18 Mg DM ha -1 ) stocking. Although, Alfagraze showed the lowest production under rotational stocking (13,3 Mg DM ha -1 ) it was the same as that of ABT-805, under continuous stocking (26,3 Mg DM ha -1 ). Pioneer 5432 showed intermediate productivity, with total accumulation of 24,3 (continuous) and 15,3 Mg DM ha -1 (rotational). The nutritive value of whole plant showed significant variation between grazing methods, although no difference among genotypes was found. Forage produced under continuous stocking had higher concentrations of crude protein (CP; 349 g kg -1 ) and in vitro digestible dry matter (IVDDM; 810 g kg -1 ) compared to rotational socking (238,5 and 757,8 g kg -1 , respectively). Fiber concentrations were the opposite of CP and IVDDM as they were lower for under continuous stocking (240 g kg -1 neutral detergent fiber, NDF; 182 g kg -1 acid detergent fiber, ADF; and 34,9 g kg -1 lignin) than under rotational stocking (325, 255, and 50,6 g kg -1 for the same three fractions, respectively). Both the stem fraction and the whole plant samples had better chemical composition and digestibility under continuous than under rotational stocking. The leaf fraction was more variable in terms of nutritive value (CP, IVDDM, ADF, and lignin concentrations) and was affected by genotype, grazing method, and season. ABT-805 and Alfagraze appear to be the most promising genotypes for grazing systems in central Brazil because of their yield performance and nutritive value. Their success, however, will depend on climatic conditions and choice of grazing management.

Estudos foram conduzidos com o objetivo de caracterizar a composição morfológica e química, as frações de carboidratos e proteínas e as taxas de degradação em amostras de estrato pastejável de capim Colonião, Marandu e Mulato manejados com altas taxas de lotação e com intervalos de desfolhas variáveis (95% de IL) durante a primavera, verão e outono. Foi realizada avaliação comparativa dos capins quanto a sua composição morfológica, produção de massa de forragem (kg MS.ha-1), composição química, frações protéicas e de carboidratos, assim como o fracionamento in situ e as taxas de degradação da PB, FDN e MS e ainda as taxas de degradação in vitro das frações protéicas entre as estações da primavera, verão e outono. No primeiro experimento, a massa de forragem e componentes morfológicos variaram com a estação do ano (P<0,05). A composição química do capim variou (P<0,05) entre as estações do ano, para teores de MS, FDN, EE, PB, NIDN, NIDA e MM. As frações de carboidratos (CHOT, frações A, B1 e B2) e as frações protéicas (A, B1, B2 e B3) foram afetadas pelas estações do ano (P<0,1). Os valores das taxas de degradação da proteína (B1, B2, B3 e B1+B2) e os valores estimados pelo método in situ para MS, FDN e PB não variaram (P<0,1) entre as estações do ano. No entanto, os valores de degradabilidade efetiva (DE) da MS e FDN foram significativos. No segundo experimento a estação do ano causou variação (P<0,05) para a massa de forragem, para os teores de MS, FDN, FDA, EE, MM e para as frações A+B1 e CHOT. Apenas a fração B1 das frações protéicas foi afetada (P<0,1) entre as estações do ano. Os valores das taxas de degradação da proteína (B1, B2 e B3) não variaram (P<0,1) entre as estações do ano. As variáveis estimadas pelo método in situ para MS, PB e FDN não variaram (P<0,1) entre as estações do ano. No terceiro experimento houve efeito (P<0,05) para massa de forragem, entre as estações do ano. Quanto a composição morfológica houve variação (P<0,05) na proporção de colmos, sendo maior no outono. A composição química apresentou efeito significativo (P<0,05) para os teores de MS, FDN, FDA, PB e MM. As frações A+B1 e B2 de carboidratos variaram (P<0,05), da mesma forma que as frações de proteína (P<0,1) também variaram conforme as estações do ano. Os valores das taxas de degradação da proteína (B1, B2 e B3) não variaram (P<0,1) entre as estações do ano. As variáveis estimadas pelo método in situ para MS, PB e FDN variaram (P<0,1) para Lambda, taxa de degradação (kdNRC) e degradabilidade efetiva (DE), entre as estações do ano. As forrageiras estudadas apresentaram-se pobre em frações de carboidratos de alta fermentabilidade ruminal (A+B1), enquanto que o teor de proteína prontamente degradada no rúmen foi elevado (A, B1 e B2). Isto pode limitar a eficiência de uso da proteína degradável no rúmen das forragens, especialmente quando adubadas intensamente com N para a obtenção de altas taxas de lotação animal. / Studies were conducted in order to characterize the morphological and chemical composition, carbohydrate and protein fractions and the degradation rate of potentially degradable CP in samples of grazed stratum of Colonião, Marandu and Mulato grasses intensively grazed at high stocking rates and variable defoliation intervals ( 95% LI) during spring, summer and autumn. Comparative analyses for grasses chemical and morphological composition forage mass production (kg MS.ha-1), protein and carbohydrates fractions, in situ fractionation and CP, NDF and MS degradation rates, and protein fractions in vitro degradation rates during seasons. On first trial, statistical effects among seasons were found for forage mass and morphological components (P<0.05), DM, NDF, fat, CP, NDIN, NIDA and ash chemical contents (P<0.05), and for carbohydrates (TC, A, B1 and B2) and protein (A, B1, B2 and B3) (P<0.1) fractions. Protein degradation rates (B1, B2, B3 and B1+B2) and the values estimated by in situ degradation method for DM, NDF and CP did not differ (P<0.1) among seasons. However, statistical effects were found for effective degradability (ED) of DM and NDF (P<0.1). On second trial statistical effects were found among season for forage mass yield, DM, NDF, ADF, fat and ash, A+B1 and TC fractions (P<0.05). Only B1 protein fraction was affected (P<0.1) by seasons. Values of protein fractions degradation rates (B1, B2 and B3) did not differ (P<0.1) among seasons. Estimation of in situ degradability of DM, CP and NDF did not differ (P<0.1) among seasons. On third trial, statistical effects were not observed for forage mass yield among seasons. In relation to morphological composition, stems proportion presented the higher values in autumn (P<0.05). Statistical effects were found among seasons for DM, NDF, ADF, fat and ash, A+B1 and B2 carbohydrate fractions (P<0.05) and for A, B1 and B2 protein fractions (P<0.1). The values of protein fraction degradation rates (B1, B2, B3 and B1 + B2) did not differ (P <0.1) among seasons. The estimation of in situ degradability of DM, CP and NDF showed statistical effects (P <0.1) for Lambda, degradation rate (kdNRC) and effective degradability (ED) among seasons. The grasses evaluated have low proportion of high ruminal degradability carbohidrates (A+B1), while the values for rapidly degraded protein fractions (A, B1 e B2) was high. As consequence, a limitation on efficiency of use of degradable protein on rumen may occur, especially when pastures were intensively fertilized with N to elevate stocking rate.

Silagens são fontes abundantes de compostos orgânicos voláteis. Durante o processo de secagem de amostras em estufas de ventilação forçada, grande parte destes compostos é perdida. Não se conhece, entretanto, a magnitude de participação destes produtos de fermentação no conteúdo energético de silagens e seus efeitos no desempenho de animais. O objetivo deste trabalho foi dimensionar a contribuição da fração volátil no valor nutricional de silagens. No primeiro experimento, avaliaram-se os efeitos do etanol e do ácido lático no consumo de matéria seca e no processo de digestão de novilhos canulados alimentados com rações contendo silagem de milho. A maior concentração ruminal de amônia foi a única alteração noticiada para o tratamento etanol. O enriquecimento da ração com ácido lático elevou o pH ruminal e diminuiu a razão acetato/propionato. Quando o teor de matéria seca foi determinado em estufa, os valores de NDT foram, em média, 1,5 a 1,6 unidades percentuais inferiores àqueles obtidos pelos cálculos utilizando a matéria seca determinada por destilação com tolueno. O segundo experimento determinou os efeitos da fração volátil da silagem de cana-de-açúcar e da proporção de forragem no consumo de matéria seca e no processo de digestão de novilhos canulados. Cerca de 21% da matéria seca da silagem de cana constituiu-se de compostos voláteis. A presença destes compostos na ração não alterou o consumo de matéria seca, mas aumentou as taxas fracionais de absorção de valerato e etanol com o ruminorretículo evacuado. O menor teor de forragem alterou a maior parte das variáveis tradicionalmente associadas aos acréscimos de concentrados na dieta. A fração volátil representou contribuição equivalente a 10% do valor energético da silagem de cana-de-açúcar determinado por digestibilidade. O terceiro ensaio foi delineado para verificar os efeitos do etanol na cinética de degradação ruminal in vitro. A inclusão de etanol nas doses 0, 5, 10, 15 ou 20% da MS diminuiu linearmente a degradação da cana-de-açúcar. No quarto experimento, avaliaram-se os efeitos do etanol e do ácido acético no desempenho de vacas leiteiras de alta produção. As vacas suplementadas com etanol produziram mais leite que àquelas alimentadas com as rações controle e ácido acético, por causa do maior consumo de MS. A razão ELl leite/CMS (Mcal/kg) foi similar entre os tratamentos. A composição química e a qualidade sensorial do leite não foram alteradas pelos compostos voláteis suplementados. A fração volátil representou 11 a 21 % da matéria seca das silagens estudadas e pode ser responsável por até 10% do valor nutricional, com base nas respostas de animais. / Silages are abundant sources of volatile organic compounds. At drying of samples by using forced ventilated oven, most of those compounds disappear. There is no agreement on the contribution of these fermentation end-products on energy content of silage and its effects on animal performance. The objective of this work was to rescale the contribution of the volatile fraction to the nutritional value of silages. In the first trial, the effects of ethanol and lactic acid on dry matter intake and digestion were studied in cannulated steers fed corn silage based diets. The highest concentration of rumen ammonia was the only change reported for the ethanol treatment. Diet enrichment with lactic acid increased the rumen pH and decreased acetate/propionate ratio. When the dry matter content was determined by oven, the TDN value averaged 1.5 to 1.6 units lower than those obtained by toluene distillation. In the second trial, the effects of the volatile fraction from sugarcane silage and forage proportion were determined. About 21% of dry matter of sugarcane silage consisted of volatile compounds. The fate of these compounds did not alter the DM intake but increased the fractional absorption rate of valerate and ethanol within empty reticulorumen. The lower content of forage changed most of variables traditionally associated with high concentrate diets. The contribution of volatile fraction represented 10% of the energy value of sugarcane silage determined by digestibility. The third trial was designed to determine the effects of ethanol on the rumen degradation kinetics in vitro. The addition of 0, 5, 10, 15 or 20% of ethanol (DM bases) linearly decreased the sugarcane degradation. In the fourth experiment, we evaluated the effects of ethanol and acetic acid on performance of high producing dairy cows. Cows supplemented with ethanol yielded more milk per day than that fed acetic acid and control diets, due to the higher DM intake. The NEl milk/ DMI (Mcal/kg) was similar across treatments. The chemical composition and sensory quality of milk were not altered by the compounds. Volatile compounds represented a range from a 11 a 21% of the DM from the studied silge sources and they might be responsable for additional 10% on the nutritional value based on animal performance.

Feeding behaviour is controlled by the integration of both perceived cues from the plant and postingestive signals received by the animal. In general practice, dairy cattle are presented with a variety of feedstuffs throughout each day, in addition to changing feedstuffs over time. In the Australian context, the feeds generally include fodder (usually hay) and pasture whilst grazing, as well as various concentrates. For horses that are stabled for prolonged periods, their diet consists of fodder (again usually hay or chaff) and concentrates, in addition to the pasture consumed whilst allowed access to graze. In such situations, where animals are presented with a range of feedstuffs, some of them novel and for discrete periods of time, it is important that they readily accept the feeds when they are first presented to them. For both lactating dairy cows and performance horses, for example, it is important to avoid periods of low intake, as this can have immediate and sometimes longer-term consequences to animal performance. The daily rate of food intake is the single most important factor affecting animal performance and productivity (Illius et al. 2000) and an animal‟s responses to a feedstuff can be considered the ultimate measure of its quality. The animal‟s first response to the presentation of a new feed, which in this particular study was oaten or lucerne hay, is its level of voluntary intake, which depends in part on palatability. Palatability is an integrative term (Provenza 1995); to provide a quantitative measure of the acceptability of a feedstuff, a „preference value’ can be obtained by describing the preference of one hay relative to an alternate hay also on offer. The Australian fodder industry is increasingly adopting more objective measures of hay quality to improve marketing opportunities, especially in the export industry, and to meet the demands and expectations of local and overseas purchasers of hay. Being able to efficiently and reliably predict the preference value of any particular hay would be beneficial to processors, exporters, users (purchasers) of hay, and possibly plant breeders, to make more informed decisions. This thesis describes a comprehensive analysis of the chemical and physical characteristics of a selected number of oaten and lucerne hays and their relationship to the acceptability or „preference value‟ of the hays for lactating Holstein Friesian cows and Thoroughbred horses. The project aimed to (i) quantify preference values for a large number of oaten hays with dairy cows and horses and a similarly large number of lucerne hays with horses only, and (ii) develop predictive equations for animal preferences based on the chemical and physical properties of the hays and the animal‟s short-term rate of consuming the hays. A total of approximately 8,500 preference tests were conducted with 85 oaten hays offered to lactating Holstein Friesian cows and Thoroughbred horses, and 70 lucerne hays offered to Thoroughbred horses. The hays were selected to cover a range of nutritive values. The intake rate and preferences for all the hays were quantified in a series of tests replicated over time and with different animals. Each „trial‟ hay was offered with four „standard‟ hays (in separate tests). A suite of chemical (nutritive value) traits and physical traits were quantified for the hays. An assessment of the „odour profile‟ was also included in the characterisation of the hays. The nutritive, physical and volatile traits were then related to hay preference values in multiple and simple linear regression models and equations generated to predict hay preference values. A prediction of hay preference made directly from the spectra obtained by near infrared reflectance spectroscopy (NIRS) was also developed. Overall, the average preference value of an oaten hay (i.e., that obtained using the comparisons with all four standard hays) could be predicted from a range of nutritive value traits, typically the contents of acid detergent fibre (ADF), hemicellulose, crude protein (CP) and water soluble carbohydrates (WSC) - with a correlation co-efficient of about 79% with cows and 61% for horses. Acid detergent fibre and CP contents tended to have the biggest influence on preference value for both cows and horses, followed by WSC and hemicellulose content. Examination of lucerne hays offered to horses increased the correlation co-efficient to 74%, with ADF, hemicellulose and CP each having a similar magnitude of effect. This means that these traits, with an appropriate weighting for each, could account for up to about three-quarters of the variation in hay preference values for cows and horses. The in vitro digestibility of dry matter (IVD) of oaten and lucerne hay was nearly as accurate in predicting preference values as using the four nutritive value traits of ADF, hemicellulose, CP and WSC, which was anticipated as digestibility is a function of these chemical traits. Hay physical traits could also be used to predict preference values, although not as accurately as the nutritive value traits or IVD. Of the physical traits, shear energy had the largest effect (co-efficient approximately -1.15 compared to an average of -0.35 for the other traits in the equation). The use of NIRS to directly predict preference values was also encouraging, with the best calibration model yielding a correlation co-efficient of 61 to 81%, depending on the hay (oaten or lucerne) and the animal (cows or horses). Of the total 120 volatile compounds isolated from the oaten hays, six had some relationship with cow preferences and there were also six oaten hay volatiles related to horse preferences. Of the oaten hay volatiles significantly related to preference, four were positively related to cow preference whilst two were negatively related to cow preference. Similarly there were four volatiles positively related to horse preference and two consistently negatively related. Of the six oaten hay volatiles found to influence the preferences of dairy cows and horses, four were common to both species. Of the total of 147 volatile compounds isolated from the lucerne hays, 15 had some relationship with horse preference, with nine positively related to horse preference and six negatively related. The data reported here suggest that a predicted preference value for a hay can be generated using commonly measured quality traits, which would improve a buyer‟s confidence of animals responding favourably when first offered the hay. More specifically, for an average preference value, the most reliable prediction equation was based on nutritive value traits: ADF, hemicellulose, crude protein and water soluble carbohydrates solely. Alternatively a combination of nutritive and physical traits can be used to predict preference: in vitro digestibility, crude protein, water soluble carbohydrates and shear energy. The visible and near infrared spectra obtained by NIRS was also a promising method of prediction, and given the speed and affordability of NIRS, this technology could be further refined and used for routine measurement of predicted hay preference values. The volatile compounds shown to influence preference value of the hay should be identified and further research undertaken to investigate novel approaches to manipulate the preference of hays. Caution should be taken when attempting to use these prediction equations on a single specific hay in a single specific situation. The predictions and relationships investigated in this thesis are based on populations of hays and preferences of a group of animals and therefore some care should be taken when applying them to a particular situation with difference circumstances. Other factors that can influence feed preferences include an animal‟s feeding experiences, basal diet and diet history and various environmental factors unaccounted for here. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349258 / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008

Feeding behaviour is controlled by the integration of both perceived cues from the plant and postingestive signals received by the animal. In general practice, dairy cattle are presented with a variety of feedstuffs throughout each day, in addition to changing feedstuffs over time. In the Australian context, the feeds generally include fodder (usually hay) and pasture whilst grazing, as well as various concentrates. For horses that are stabled for prolonged periods, their diet consists of fodder (again usually hay or chaff) and concentrates, in addition to the pasture consumed whilst allowed access to graze. In such situations, where animals are presented with a range of feedstuffs, some of them novel and for discrete periods of time, it is important that they readily accept the feeds when they are first presented to them. For both lactating dairy cows and performance horses, for example, it is important to avoid periods of low intake, as this can have immediate and sometimes longer-term consequences to animal performance. The daily rate of food intake is the single most important factor affecting animal performance and productivity (Illius et al. 2000) and an animal‟s responses to a feedstuff can be considered the ultimate measure of its quality. The animal‟s first response to the presentation of a new feed, which in this particular study was oaten or lucerne hay, is its level of voluntary intake, which depends in part on palatability. Palatability is an integrative term (Provenza 1995); to provide a quantitative measure of the acceptability of a feedstuff, a „preference value’ can be obtained by describing the preference of one hay relative to an alternate hay also on offer. The Australian fodder industry is increasingly adopting more objective measures of hay quality to improve marketing opportunities, especially in the export industry, and to meet the demands and expectations of local and overseas purchasers of hay. Being able to efficiently and reliably predict the preference value of any particular hay would be beneficial to processors, exporters, users (purchasers) of hay, and possibly plant breeders, to make more informed decisions. This thesis describes a comprehensive analysis of the chemical and physical characteristics of a selected number of oaten and lucerne hays and their relationship to the acceptability or „preference value‟ of the hays for lactating Holstein Friesian cows and Thoroughbred horses. The project aimed to (i) quantify preference values for a large number of oaten hays with dairy cows and horses and a similarly large number of lucerne hays with horses only, and (ii) develop predictive equations for animal preferences based on the chemical and physical properties of the hays and the animal‟s short-term rate of consuming the hays. A total of approximately 8,500 preference tests were conducted with 85 oaten hays offered to lactating Holstein Friesian cows and Thoroughbred horses, and 70 lucerne hays offered to Thoroughbred horses. The hays were selected to cover a range of nutritive values. The intake rate and preferences for all the hays were quantified in a series of tests replicated over time and with different animals. Each „trial‟ hay was offered with four „standard‟ hays (in separate tests). A suite of chemical (nutritive value) traits and physical traits were quantified for the hays. An assessment of the „odour profile‟ was also included in the characterisation of the hays. The nutritive, physical and volatile traits were then related to hay preference values in multiple and simple linear regression models and equations generated to predict hay preference values. A prediction of hay preference made directly from the spectra obtained by near infrared reflectance spectroscopy (NIRS) was also developed. Overall, the average preference value of an oaten hay (i.e., that obtained using the comparisons with all four standard hays) could be predicted from a range of nutritive value traits, typically the contents of acid detergent fibre (ADF), hemicellulose, crude protein (CP) and water soluble carbohydrates (WSC) - with a correlation co-efficient of about 79% with cows and 61% for horses. Acid detergent fibre and CP contents tended to have the biggest influence on preference value for both cows and horses, followed by WSC and hemicellulose content. Examination of lucerne hays offered to horses increased the correlation co-efficient to 74%, with ADF, hemicellulose and CP each having a similar magnitude of effect. This means that these traits, with an appropriate weighting for each, could account for up to about three-quarters of the variation in hay preference values for cows and horses. The in vitro digestibility of dry matter (IVD) of oaten and lucerne hay was nearly as accurate in predicting preference values as using the four nutritive value traits of ADF, hemicellulose, CP and WSC, which was anticipated as digestibility is a function of these chemical traits. Hay physical traits could also be used to predict preference values, although not as accurately as the nutritive value traits or IVD. Of the physical traits, shear energy had the largest effect (co-efficient approximately -1.15 compared to an average of -0.35 for the other traits in the equation). The use of NIRS to directly predict preference values was also encouraging, with the best calibration model yielding a correlation co-efficient of 61 to 81%, depending on the hay (oaten or lucerne) and the animal (cows or horses). Of the total 120 volatile compounds isolated from the oaten hays, six had some relationship with cow preferences and there were also six oaten hay volatiles related to horse preferences. Of the oaten hay volatiles significantly related to preference, four were positively related to cow preference whilst two were negatively related to cow preference. Similarly there were four volatiles positively related to horse preference and two consistently negatively related. Of the six oaten hay volatiles found to influence the preferences of dairy cows and horses, four were common to both species. Of the total of 147 volatile compounds isolated from the lucerne hays, 15 had some relationship with horse preference, with nine positively related to horse preference and six negatively related. The data reported here suggest that a predicted preference value for a hay can be generated using commonly measured quality traits, which would improve a buyer‟s confidence of animals responding favourably when first offered the hay. More specifically, for an average preference value, the most reliable prediction equation was based on nutritive value traits: ADF, hemicellulose, crude protein and water soluble carbohydrates solely. Alternatively a combination of nutritive and physical traits can be used to predict preference: in vitro digestibility, crude protein, water soluble carbohydrates and shear energy. The visible and near infrared spectra obtained by NIRS was also a promising method of prediction, and given the speed and affordability of NIRS, this technology could be further refined and used for routine measurement of predicted hay preference values. The volatile compounds shown to influence preference value of the hay should be identified and further research undertaken to investigate novel approaches to manipulate the preference of hays. Caution should be taken when attempting to use these prediction equations on a single specific hay in a single specific situation. The predictions and relationships investigated in this thesis are based on populations of hays and preferences of a group of animals and therefore some care should be taken when applying them to a particular situation with difference circumstances. Other factors that can influence feed preferences include an animal‟s feeding experiences, basal diet and diet history and various environmental factors unaccounted for here. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349258 / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2008. / Härtill 4 uppsatser.

Orientador: Rafael Silvio Bonilha Pinheiro / Resumo: Na busca por minimizar a sazonalidade da produção de forragens e manter a qualidade nutricional, o uso da consorciação de culturas de inverno é uma alternativa que promove a disponibilidade de forragem de alta qualidade no período em que há pouco crescimento das pastagens tropicais, visando suprir a baixa oferta alimentar de qualidade ocasionada no período de outono e inverno com baixo custo de implantação. Portanto, objetivou-se, com o presente estudo, avaliar métodos de sobressemeadura da aveia preta em pastagem irrigada de Tifton-85 em cerrado de baixa altitude, sob pastejo de ovinos durante dois anos, analisando os índices de produtividade, custos de produção e composição bromatológica da consorciação forrageira da pastagem. Os tratamentos experimentais utilizados foram: controle (pastagem de Tifton-85), sobressemeaduras realizada na pastagem de Tifton-85 da aveia antes do pastejo dos ovinos; aveia durante o pastejo dos ovinos; aveia com compactação com trator; aveia com gradagem superficial; e aveia com gradagem superficial e compactação com trator. O delineamento experimental foi conduzido em blocos completos casualizados com seis tratamentos (métodos de sobressemeadura e o controle) e quatro repetições (24 unidades experimentais). Recomenda-se de acordo com os resultados obtidos, o método de sobressemeadura de aveia preta no capim Tifton-85 antes do pastejo, por apresentar participação efetiva na composição botânica do pasto, aumentando a disponibilidade de forragem, c... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In order to minimize the seasonality of forage production and maintain nutritional quality, the use of intercropping in winter crops is an alternative that promotes the availability of high quality fodder in the period when there is little growth of tropical pastures, aiming to supply the low quality food supply in the autumn and winter with low implementation costs. Therefore, the objective of this study was to evaluate the methods of overgrazing of black oats in Tifton-85 irrigated pasture in low-lying cerrado, under grazing of sheep for two years, analyzing productivity, production costs and composition of grassland forage consortium. The experimental treatments used were: control (Tifton-85 pasture), rearing performed on the Tifton-85 pasture of oats before grazing of sheep; oats during grazing of sheep; oats with compaction with tractor; oats with surface sorting; and oats with surface sorting and tractor compaction. The experimental design was conducted in randomized complete blocks with six treatments (overpressure and control methods) and four replicates (24 experimental units). According to the results obtained, the method of overwintering of black oats in the Tifton-85 grass before grazing is recommended, since it presents an effective participation in the botanical composition of the pasture, increasing the availability of forage, with nutritional quality and low implantation cost. / Mestre