The aim of this study was to investigate the relationship between thigh intramuscular fat (intraMF) and intermuscular fat (IMF) with quadriceps and hamstrings power and physical performance in women (n=20) with clinical, radiographic knee osteoarthritis (OA). Secondarily, we investigated the correlation between thigh and calf fat volumes, and the agreement between 3.0T and 1.0T MRI for quantifying fat. The thigh and calf of the symptomatic leg were scanned using 3.0T MRI with the IDEAL sequence, and fat separated images were analyzed using semi-automated software to quantify intraMF, IMF and muscle. The calf was also scanned using 1.0T MRI with a Fast Spin Echo (FSE) sequence. Knee extensor and flexor isokinetic power was measured at 20% and 40% of individuals’ maximum voluntary isometric contraction (MVIC) torque, and surface electromyography (EMG) measured activation. We found no relationship between quadriceps or hamstrings intraMF and knee extensor or flexor power, respectively. In addition, there were no relationships between intraMF and performance-based tests. There was a correlation between thigh and calf intraMF (r=0.759; p=0.001) and a trend toward a correlation in IMF (r=0.436; p=0.055). There was agreement and a correlation between calf intraMF (r=0.779; p=0.001) and IMF (r=0.956; p=0.001) using 3.0T and 1.0T MRI. There is disagreement about the relationship of intraMF and quadriceps strength, although studies have found that intraMF is related to decreased physical performance. The importance of calf fat subsets in physical performance of individuals with OA should be further investigated. Power analysis demonstrated a sample size (n=91) is recommended for future investigations of intraMF and power in OA. / Thesis / Master of Science in Medical Sciences (MSMS)

Présentement, le diagnostic d’otite moyenne-interne chez le veau est basé sur la présence de signes cliniques appropriés ainsi que les tests diagnostiques tels que la radiographie et la tomodensitométrie. L’objectif de cette étude prospective était d’évaluer les valeurs prédictives de l’examen neurologique, l’examen otoscopique et le test des potentiels auditifs évoqués (PAE) dans le diagnostic d’otite moyenne-interne chez le veau, en utilisant la tomodensitométrie comme test standard. Le deuxième objectif était de définir les valeurs de référence pour le PAE chez le veau normal et d’en décrire les anomalies chez des veaux atteints d’otite moyenne-interne. Dix-sept veaux de race Holstein entre 5-7 semaines d’âge ont été inclus. Tous les veaux ont eu un examen neurologique, un examen otoscopique et une évaluation des PAEs. Les veaux ont été tranquillisés avec de la xylazine intraveineuse (0,05-0,15mg/kg) pour la tomodensitométrie des bulles tympaniques afin d’évaluer pour la présence d’otite moyenne-interne. Selon les résultats de la tomodensitométrie, 11 des 17 veaux étaient atteints avec otite moyenne, 4 de façon unilatérale et 7 bilatéralement. Cinq ondes ont été identifiées de façon constante sur les tracés des PAEs des 6 veaux normaux. Les valeurs positives prédictives pour le PAE, l’examen neurologique et l’examen otoscopique étaient 94,7%, 91,7% et 66,7% respectivement. D’un point de vue clinique, le test le plus fiable dans le diagnostic d’otite moyenne-interne chez le veau est le PAE. Les anomalies ont été observées au PAE avant le développement des signes neurologiques chez certains veaux. / Currently, the antemortem diagnosis of otitis media-interna is based upon the presence of appropriate clinical signs and adjunctive diagnostic imaging including radiography and computed tomography. The purpose of this prospective study was to evaluate predictive values of neurological examination, otoscopic examination and BAER in calves for the diagnosis of otitis media-interna using computed tomography as the gold standard. The second objective was to define BAER reference values in normal calves and to describe BAER abnormalities in calves affected with otitis media-interna. Seventeen Holstein calves between 5 and 7 weeks of age were included. All calves had a neurological examination, otoscopic examination and BAER. Calves were sedated with intravenous xylazine (0.05-0.15 mg/kg [0.02-0.07 mg/lb]) for computed tomography of the tympanic bullae to evaluate for the presence of otitis media-interna. Based upon computed tomographic results, 11 of 17 calves were affected with otitis media, 4 unilaterally and 7 bilaterally. Five waveforms were consistently identified on BAER traces from 6 normal calves. The positive predictive value of BAER, neurological examination and otoscopic examination were 94.7%, 91.7% and 66.7% respectively. Clinically, the most reliable non-invasive diagnostic test to diagnose otitis media-interna in the calf is the BAER. Abnormalities were observed on BAER before the development of neurological deficits in approximately 40% of calves allowing earlier diagnosis.

L'otite moyenne est une condition fréquente chez le veau et peut parfois être subclinique, rendant difficile son diagnostic à la ferme. L'objectif de cette étude est d’estimer la sensibilité et la spécificité de l'échographie des bulles tympaniques pour le diagnostic d'otite moyenne clinique et subclinique et de déterminer sa répétabilité. Quarante veaux âgés entre 19 et 50 jours ont été sélectionnés dans une ferme de veaux de grain, en fonction des résultats de l'échographie réalisée à la ferme (A). L'échographie a été réalisée une seconde fois par le même échographiste (A') et par un second échographiste (B), et le diagnostic noté pour chaque bulle tympanique comme étant négatif, suspect ou positif. Les images ont été enregistrées pour relecture et le diagnostic noté. Les veaux ont été euthanasiés, soumis en nécropsie et l'histologie a été utilisée comme méthode de référence. À l'histologie, 45 bulles tympaniques étaient atteintes d'otite moyenne et 35 bulles tympaniques étaient saines. Selon l'échographiste et la classification des bulles tympaniques suspectes, la sensibilité de l'échographie variait de 32% à 63% et la spécificité variait de 84% à 100%. La répétabilité était modérée, avec des valeurs de kappa de 0,53 entre A' et B, de 0,48 entre A et A', et de 0,58 et 0,75 pour la relecture de leurs images par A' et B respectivement. / Otitis media is a common disease in calves but can remain subclinical, making diagnosis challenging on the farm. The objective of this study is to estimate the sensitivity and specificity of the ultrasound imaging technique of tympanic bulla for the diagnosis of clinical and subclinical otitis media, and to determine its repeatability. Forty calves 19-50 days of age were selected from a veal calf farm, on the basis of results of ultrasound examination performed on the farm (A). Ultrasound examination was performed a second time by the same ultrasonographer (A') and by another ultrasonographer (B), and diagnosis was recorded for both tympanic bulla as negative, suspicious or positive. Images were recorded for further re-reading. Calves were euthanized and submitted for necropsy, and histopathologic diagnosis was used as gold standard. Based upon histology, 45 bullae were affected with otitis media and 35 bullae were unaffected. Depending on ultrasonographer and on classification of suspicious bullae, sensitivity varies from 32% to 63% and specificity varies from 84% to 100%. Repeatability is moderate, with kappa values of 0.53 for A'-B, 0.48 for A-A', and 0.58 and 0.75 for re-reading of A' and B, respectively.

Title: The effect of menstrual cycle phases on muscle tone Goals and methods: The aim of this thesis is to prove the effect of menstrual cycle phases and participating hormons on the viscoelastic properties of the sceletal calf muscle via the non-invasive myotonometer device. The research part of this thesis is a pilot study in which participated seven female probands aged inbetween 24 to 28. Each proband participated in four weekly tests. Only probands who had not used hormonal contraception for at least six months were selected. Results: The results of the tests are represented in graphs picturing parts of curves representing the force caused by the tip of the myotonometer. The muscle soleus tension is changing throughout the menstrual cycle but its impossible to eliminate other endogenous and exogenous factors. The measured relative values of muscle tension are different for each proband. The menstrual phase has the highest average value of muscle tension. However, it is not possible to make a generally valid conclusion. Key words: Menstrual cycle, menstrual phase, muscle tone, calf muscle, biomechanical properties, myotonometry, contraception 5

Title: The effect of menstrual cycle phases on muscle tone Goals and methods: The aim of this thesis is to prove the effect of menstrual cycle phases and participating hormons on the viscoelastic properties of the sceletal calf muscle via the non-invasive myotonometer device. The experimental part of this thesis is a pilot study in which participated seven female probands aged inbetween 24 to 28. Each proband participated in four weekly tests. Only probands who had not used hormonal contraception for at least six months were selected. Results: The results of the tests are represented in graphs picturing parts of curves representing the force caused by the tip of the myotonometer. The muscle soleus tension is changing throughout the menstrual cycle but its impossible to eliminate other endogenous and exogenous factors. The measured relative values of muscle tension are different for each proband. The menstrual phase has the highest average value of muscle tension. It is not possible to make a generally valid conclusion. Key words: Menstrual cycle, menstrual phase, muscle tone, calf muscle, biomechanical properties, myotonometry, contraception

Call number: LD2668 .T4 1986 H54 / Master of Science / Agricultural Economics

L’étiologie des bronchopneumonies infectieuses (BPI) des jeunes bovins est multifactorielle, mettant en cause des agents infectieux comme des bactéries, virus ou parasites, et également des facteurs de risques liés à la conduite d’élevage et à l’environnement. Dans cette thèse nous nous sommes intéressés aux virus respiratoires bovins. Nous avons étudié le virome de l’appareil respiratoire superficiel et profond des jeunes veaux atteints de BPI par des approches de séquençage à haut débit pour mieux caractériser les co-infections virales et identifier de nouveaux virus. Par ailleurs nous nous sommes intéressés au contexte dans lequel les virus opèrent en analysant la structure, la diversité, et le dynamisme du bactériote respiratoire chez des veaux sains et atteints de BPI. Les résultats suggèrent que de nombreux virus agissent en interactions et montrent une prédominance du coronavirus bovin (BCoV) dans les cavités nasopharyngées et également dans les poumons des veaux atteints de BPI. L’étude phylogénétique des BCoV isolés indique une ségrégation entre souches européennes d’une part et américaines et asiatiques d’autre part qui semble résulter d’un phénomène de recombinaison dans les années 1960-70. Par ailleurs un astrovirus bovin a été clairement détecté pour la première fois principalement dans les poumons de veaux atteints de BPI. L’analyse du microbiote indique, elle, une disparité écologique entre cavités superficielles et profondes et des interactions possibles entre agents pathogènes connus et différentes communautés bactériennes de la flore résidente. Enfin une partie des travaux a concerné le virus influenza D (IDV), un nouveau virus respiratoire bovin émergent récemment identifié en France. Lors d’une infection expérimentale chez des veaux nous avons démontré que IDV possède un pouvoir pathogène respiratoire modéré et qu’il module la réponse immunitaire innée du veau. Nous avons aussi confirmé le caractère ubiquiste d’IDV en démontrant sa circulation sur le continent africain. En conclusion, grâce à des méthodes de séquençages à haut débit ce travail a permis une meilleure description et caractérisation des virus respiratoires bovins et de leur environnement immédiat. Il ouvre des perspectives pour mieux comprendre le rôle des interactions virales dans la genèse des signes cliniques respiratoires. / Bovine infectious bronchopneumonia (BIP) is a complex syndrome that affects young bovines, with a multifactorial etiology often involving one or several viruses and bacteria favored by altered host immunity and disturbed environmental factors. First, using viral metagenomics sequencing tools, we explored the upper (URT) and lower (LRT) respiratory tract viromes of calves with BPI and identified unexpected viruses. In addition, in the same calves, we characterized the structure, diversities and dynamism of the bacterial communities. Results showed different patterns of interactions between the different components of the microbiomes. Among the many detected viruses, the bovine coronavirus (BCoV), showed the highest prevalence in both nasal and pulmonary cavities. Evolutionary and phylogenic analysis of the isolated BCoV strains indicated a clear segregation between European and American/Asian strains, which seems to have resulted from a recombination event during the 1960-70’s. Furthermore, a bovine astrovirus was detected for the first time in the lungs of BIP affected calves. A disparity was noticed in the bacterial community structures between the upper and lower respiratory cavities. Also, there were associations between the presences of certain bacterial taxa and known respiratory pathogens. Finally, a part of the work focused on the emerging influenza D virus (IDV) recently identified in France. Carrying an experimental infection, we showed that IDV has a moderate respiratory pathogenicity and can modulate the innate immune response of the calf. We also showed that IDV circulates in Africa thus confirming its global distribution. In conclusion, thanks to high throughput sequencing methods, this piece of work allowed for a detailed characterization of the bovine respiratory virome and its interacting environment, and further opened new perspectives for a better understanding of viral interactions in bovine BIP.

Quarenta vacas lactantes e não gestantes, com idade aproximada de quatro anos e seus respectivos bezerros foram distribuídos em blocos, de acordo com a data do parto, e avaliadas dos 15 aos 180 dias de lactação. As vacas pertenciam a quatro grupos genéticos: 10 da raça Nelore (NE) com bezerros de touros Nelore; e 10 Canchim x Nelore (CN), 10 Angus x Nelore (AN) e 10 Simental x Nelore (SN) com bezerros filhos de touros da raça Canchim. As vacas cruzadas e as Nelore eram de origem do mesmo rebanho Nelore. As vacas foram alimentadas com uma única dieta peletizada contendo 50% de feno (15% de alfafa e 35% de Coastcross) e 50% de concentrado, com 16,1% PB e 2,24 Mcal EM, com base na MS. A quantidade de alimento fornecida foi ajustada a cada 14 dias para que o peso vivo em jejum (PVj) e o escore de condição corporal (ECC) da vaca ficassem inalterados. O PVj e ECC para as vacas NE, CN, AN e SN foram: 430 e 4,7; 449 e 4,8; 496 e 5,0; 507 e 5,1; respectivamente. Os bezerros receberam a mesma dieta a partir dos 40 dias de idade. A produção de leite das vacas foi determinada pelo método de pesagem dos bezerros antes e após a mamada aos 52, 66, 94, 122 e 178 dias de lactação, em média. Foi realizada ordenha manual aos 80 e 150 dias, para se estimar a composição do leite. As vacas NE consumiram menos energia metabolizável (19,7 Mcal/d; P<0,05) do que as vacas CN (20,6 Mcal/d), AN (23,1 Mcal/d) e SN (23,7 Mcal/d), valores positivamente correlacionados à produção de leite (P<0,05). Bezerros Nelore apresentaram menor peso ao desmame (P<0,05) do que os bezerros ¾Canchim¼Nelore (¾C¼N), ½Canchim¼Angus¼Nelore (½C¼A¼N) e ½Canchim¼Simental¼Nelore (½C¼S¼N) (165,8 vs. 205,5; 216,4 e 215,4 kg, respectivamente). Associado ao menor ganho de peso durante o aleitamento, os bezerros Nelore apresentaram menor (P<0,05) ingestão de energia metabolizável (Mcal de leite + Mcal de ração). Os bezerros foram abatidos ao desmame e a composição química do corpo vazio estimada utilizando a 9- 10- 11a costelas. A energia no corpo vazio foi maior (P<0,05) para os bezerros ½C¼A¼N (462,6 Mcal) em relação aos ¾C¼N (384,0 Mcal) e Nelore (321,8 Mcal); a quantidade de energia no corpo vazio para os bezerros ½C¼S¼N foi intermediária; 429,8 Mcal. A eficiência energética da unidade vaca/bezerro foi maior (P<0,05) para o grupo materno AN (124,4 kcal de bezerro desmamado/Mcal EM ingerida por vaca e bezerro) comparada ao par NE/Nelore (95,8 kcal/Mcal). Os pares Canchim e Simental foram intermediários, 105,2 e 107,0 kcal/Mcal, respectivamente. Portanto, a maior energia no corpo vazio e maior ganho de peso dos bezerros ½C¼A¼N mais do que compensou a ingestão mais elevada de energia metabolizável da unidade vaca/bezerro em comparação ao Nelore. Pode-se considerar que para as condições estabelecidas neste experimento, cujo delineamento não apresentava limitação nutricional, o cruzamento melhorou a eficiência da vaca, quando considerada a proporção de energia total consumida que foi depositada nos bezerros. Entretanto, não houve avaliação de parâmetros reprodutivos, e o menor consumo e exigência de MS e EM estabelecido para a vaca Nelore sugere que em ambiente nutricional desfavorável este genótipo poderia apresentar melhor produtividade. / Forty mature, lactating and non-pregnant cows (10 Nellore - NL; 10 Canchim x Nellore - CN; 10 Angus x Nellore - AN; and 10 Simmental x Nellore - SN) were randomized in blocks by calving date. Calves out of crossbred cows were sired by Canchim bulls, while calves out of NL cows were sired by Nellore bulls. Cows were individually fed from postpartum to weaning (15-180 d) a pelleted diet made of 50% hay (15% alfalfa and 35% Coastcross) and 50% concentrate. Diet had 16.1% CP and 2.24 Mcal of metabolizable energy (ME) on a DM basis. Amount offered to each individual cow was adjusted every 14 days to maintain shrunk body weight (SBW) and body condition score (BCS). SBW and BCS were 430 and 4.7, 449 and 4.8, 496 and 5.0, and 507 and 5.1 for NL, CN, AN and SN, respectively. At 40 days of age calves had access to the same diet of their dams ad libitum. Milk yields were determined at 52, 66, 94, 122 and 178 days postpartum by weighting calves before and after suckling. Cows were milked at 80 and 150 days postpartum and the samples analyzed for fat, protein, and lactose. Daily ME intake by NL cows (19.7 Mcal/d) was lower (P<0.05) compared to CN (20.6Mcal/d), AN (23.1 Mcal/d) and SN (23.7 Mcal/d). These results were positively correlated with milk yield (P<0.05). Nellore calves had lower weaning weight than crossbreds (P<0.05): 165.8 vs. 205.5 for ¾Canchim¼Nellore (¾C¼N), 216.4 for ½Canchim¼Angus¼Nellore (½C¼A¼N) and 215.4 kg for ½Canchim¼Simmental¼Nellore (½C¼S¼N). In association with the lowest weight gain, Nellore calves had lower (P<0.05) metabolizable energy intake (ME from milk plus ration, Mcal). Calves were slaughtered at weaning and body composition estimated using the 9-10-11th rib section. Body energy at weaning (Mcal) was higher (P<0.05) for ½C¼A¼N than ¾C¼N and Nellore calves: 462.6 vs. 384.0 and 321.8 Mcal, respectively. Calves ½C¼S¼N had intermediate body energy at weaning: 429.8 Mcal. Cow/calf energetic efficiency was higher (P<0.05) for AN compared to NL cow/calf pairs: 124.4 vs. 95.8 kcal deposited/Mcal of ME consumed by cow and calf. Results for Canchim and Simmental were intermediate: 105.2 and 107.0 kcal/Mcal, respectively. The higher ME intakes by Angus cow/calf pairs were more than compensated by the higher energy retention and body weight gain compared to NL. In an unrestricted nutritional setting, crossbreeding improved cow efficiency as measured by body energy/total feed energy input to cow and calf. Reproduction was not evaluated, and the lower intakes and daily energy requirements demonstrated for Nellore could be beneficial in a nutritionally limited environment.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-10-25T13:39:22Z No. of bitstreams: 1 2015 - Carine Cristina Gon?alves Galv?o.pdf: 2315391 bytes, checksum: 154e1cdd3a9bb2de5fd18d636c4a6543 (MD5) / Made available in DSpace on 2016-10-25T13:39:22Z (GMT). No. of bitstreams: 1 2015 - Carine Cristina Gon?alves Galv?o.pdf: 2315391 bytes, checksum: 154e1cdd3a9bb2de5fd18d636c4a6543 (MD5) Previous issue date: 2015-02-24 / Funda??o Carlos Chagas Filho de Amparo ? Pesquisa do Estado do RJ - FAPERJ / Some animals have extremely complex relationships including the formation of matriarchal societies, alliances and communities, specific long-term relationships, and formation of flexible groups, such as dolphins. Ilha Grande Bay, along with Sepetiba Bay, have the largest population of Sotalia guianensis throughout its distribution, with about 1311 individuals in the first one, and 1043 individuals in the second, where it has been registered groups with up to 450 individuals. This study aimed to analyze the social organization of the mothers of S. guianensis from Ilha Grande Bay. The mothers were considered those dolphins observed at least five times in high proximity of a calf; all its associates were also classified as females and included in the analysis. The analysis of these mothers? social structure was carried out in SOCPROG? software (2.5 version) using a Half Weight Index (HWI). It was performed an analysis of the community division by modularity which indicated that individuals do not form independent clusters. A Monte Carlo permutation test was done and showed the presence of preferred associations among some dyads. Finally, a temporal analysis was performed with the use of mathematical models fitted to the Lagged Association Rate to try to explain how associations behave over time. The social structure of the 25 mothers identified in Ilha Grande Bay seems to be poorly differentiated, forming a large social network with weak associations between dyads, and following a fission-fusion dynamics. There was no statistical difference in the associations between and within classes (mothers X females). This work is a contribution to the understanding of the species? social dynamics, which are still poorly known, and highlights the need for more research in the area. / Alguns animais possuem rela??es extremamente complexas, incluindo forma??o de sociedades matriarcais, alian?as e comunidades, relacionamentos espec?ficos de longa dura??o, e forma??o de grupos flex?veis, como ? o caso dos golfinhos. A Ba?a da Ilha Grande, juntamente com a Ba?a de Sepetiba, possui a maior popula??o de Sotalia guianensis em toda a sua distribui??o, com estimativa de 1311 indiv?duos na primeira, e 1043 indiv?duos na segunda, onde j? foram registrados grupos com at? 450 indiv?duos. Este trabalho teve como objetivo analisar a organiza??o social das m?es de S. guianensis da Ba?a da Ilha Grande. Foram consideradas m?es aqueles golfinhos vistos no m?nimo cinco vezes em forte proximidade de um filhote, e todos os seus associados foram classificados como f?meas e inclu?dos nas an?lises. A an?lise da estrutura social destas m?es foi feito no programa SOCPROG? (vers?o 2.5) atrav?s do ?ndice Half Weight (HWI). Foi feita uma an?lise de divis?o de comunidades por modularidade que indicou que os indiv?duos n?o formam agrega??es independentes. Um teste de permuta??o de Monte Carlo foi realizado e mostrou a presen?a de associa??es preferidas entre algumas duplas. Por fim, uma an?lise temporal foi realizada com a utiliza??o de modelos matem?ticos ajustados ? Lagged Association Rate para tentar explicar como as associa??es se comportam no decorrer do tempo. A estrutura social das 25 m?es identificadas de S. guianensis na Ba?a da Ilha Grande se mostrou pouco diferenciada, formando uma grande rede com fracas associa??es entre duplas, seguindo uma din?mica de fiss?o-fus?o. N?o houve diferen?a estat?stica nas associa??es entre e dentro das classes (m?es X f?meas). Este trabalho ? uma contribui??o para o entendimento das din?micas sociais da esp?cie, que ainda s?o pouco conhecidas, e ressalta a necessidade de mais pesquisas na ?rea.

O rebanho brasileiro de bovinos leiteiros é composto predominantemente por vacas mestiças criadas em condições tropicais. Os principais modelos usados no Brasil para a formulação e avaliação de dietas são norte-americanos e baseados nas exigências de vacas Holandesas em clima temperado. A principal contribuição do primeiro capítulo deste estudo foi o desenvolvimento e avaliação de um novo modelo para estimar a ingestão de matéria seca (IMS) de vacas mestiças. A nova equação de predição da IMS foi desenvolvida e avaliada usando um banco de dados com 161 médias de tratamentos provenientes de 38 estudos brasileiros publicados com vacas mestiças [n = 446 vacas, 16,60 ± 5,70 (DP) kg leite/dia]. O modelo proposto foi: IMS (kg/dia): [0,5552 (± 0,06636 EP) × LC4%G + 0,06332 (± 0,009455) × PV0,75] × [1 - e (- 0,7732 (± 0,7019) × (SEM - 1,629 (± 1,9313))) ]. O novo modelo apresentou maior acurácia (QMEP = 1,64, r2 = 0,88) na predição da IMS quando comparado com modelos norte-americanos. O novo modelo de predição da IMS pode ser aplicado na formulação de dietas para vacas leiteiras mestiças em condições tropicais. No capítulo 2, um estudo avaliou as novas atualizações das exigências nutricionais de bezerras leiteiras sugeridas por Van Amburgh e Drackley (2005) e inseridas em programa comercial (AMTS, Agricultural Modeling and Training Systems, AMTS.Cattle.ProTM Calf Model versão 3.5.8.0, 2015). Dados de 16 estudos brasileiros envolvendo 51 dietas para bezerros leiteiros (n = 485, peso ao desmane de 62,02 ± 10,16 kg) foram usados para avaliar os modelos do NRC (2001) e o AMTS. Nas condições do conjunto de dados do presente estudo, ambos os sistemas superestimaram o ganho calculado a partir da proteína disponível. O ganho de peso estimado pela energia disponível da dieta, foi superestimado em 19 g/dia quando calculado pelo NRC e subestimado em 68 g/dia quando calculado pelo AMTS. O ganho de peso possível a partir da energia disponível foi menor quando calculado pelo AMTS em relação ao NRC (2001). Para o conjunto de dados experimentais brasileiros, os ganhos de peso de bezerros foram 32% inferiores aos descritos na literatura para sistemas norte-americanos. As razões para esta discrepância precisam ser compreendidas, pois somente assim novos modelos poderão ser desenvolvidos e parametrizados para estimar o desempenho animal de forma mais acurada e precisa. / The Brazilian dairy herd is mainly made up of crossbred cows fed under tropical conditions. The main models in use to formulate and evaluate diets in Brazil are from North America. These models are based on the requirements of Holstein dairy cows under temperate climate. Therefore, the main contribution of this first Chapter was the development and evaluation of a new model to estimate dry matter intake (DMI) of crossbred dairy cows. The new DMI equation was developed and evaluated using a database with 161 treatment means from 38 published studies of Brazilian crossbred cows [n = 446 dairy cows, mean milk production of 16.60 ± 5.70 (SD) kg/day]. The new model showed higher DMI prediction accuracy (MSEP = 1.64, r2 = 0.88) than American models. Therefore, this model can be used in the formulation of diets for crossbred dairy cows under tropical conditions. In Chapter 2, we evaluated the updates on the nutritional requirements of dairy calves suggested by Van Amburgh and Drackley (2005) and inputted into Agricultural Modeling and Training Systems (AMTS, AMTS.Cattle.ProTM Calf Model version 3.5.8.0, 2015). Data from 16 previous Brazilian studies involving 51 diets for dairy calves (n = 485 calves, weaning weight of 62.02 ± 10.16 kg) were used to evaluate the Nutrient Requirements of Dairy Cattle - NRC (2001) and AMTS models. According to the data set from this study, both systems overestimated the gain calculated from the available protein. The weight gain estimated by the energy available from the diet was overestimated by 19 g/day when calculated by the NRC and underestimated by 68 g/day when calculated by AMTS. Weight gain estimated by the dietary energy of the AMTS system was lower than the NRC (2001). The Brazilian data set showed a calf gain around 32% lower than those described in U.S. dairy farms. The reasons for this discrepancy need to be understood, for only then can new models be developed and parameterized to estimate animal performance more accurately and precisely.