Free-access acidified milk feeding is increasingly being adopted to feed dairy and veal calves. Acidification is used to preserve milk and facilitate free-access feeding. There is, however, little controlled research to support the adoption of free-access acidified milk feeding over traditional feeding programs. The objectives of this thesis were to describe the preweaned calf management and feeding practices used on dairy farms in Ontario, Canada, and to investigate the effects of milk replacer acidification and free-access feeding on the productivity and welfare of calves. A total of 140 Ontario dairy producers participated in a cross-sectional study and were surveyed about on-farm calf management and feeding practices. Results from this study documented that there are currently a range of management practices and several different feeding programs being used on farms. Colostrum and milk feeding management are the areas where the most progress has been made in recent years; however, several other aspects of calf management and feeding still warrant improvement. A pilot study was conducted to examine the effects of milk replacer acidification and free-access feeding on the nutrient intake, growth, rumen papillary development and behaviour of calves. A field study was designed to evaluate the effects of a free-access acidified milk replacer feeding program on the pre and postweaning health and growth of dairy and veal calves. A randomized controlled study was completed to investigate how milk replacer acidification, under free-access feeding conditions, affects the pre and postweaning performance and health of veal calves. Results from these studies demonstrated that milk replacer acidification limited calves’ intake of milk replacer by approximately 1 L/d, resulted in more fragmented feeding behaviour, promoted earlier solid feed intake and tended to support improved respiratory health, but had little impact on rumen development or long-term calf performance. Moreover, free-access feeding facilitated larger intakes of milk, resulted in fewer signs of hunger or frustration, and supported greater preweaning growth, but delayed the onset of solid feed consumption and appeared to negatively affect rumen development, compared to restricted feeding. Collectively, these results demonstrate that free-access acidified milk feeding promotes greater early life productivity and enhances calf welfare. / Ontario Ministry of Agriculture, Food and Rural Affairs, Dairy Farmers of Ontario, Ontario Veal Association, National Sciences and Engineering Research Council, Grober Nutrition and 3M Canada

Le desserrage des tiges est une complication fréquente des plâtres avec tiges transcorticales (TP) chez les grands animaux, nécessitant souvent leur retrait prématuré avant la guérison des fractures. Les charges excessives centrées sur le cortex à l’interface os-tige proximo-externe et disto-interne causent de l'ostéolyse. En utilisant un modèle de veau nouveau-né, ce projet a évalué un nouveau système de tige-manchon et anneau integré dans un plâtre (PS) optimisé pour réduire la contrainte péri-implant et le stress à l'interface os-implant. On a émis l'hypothèse que les PS se traduiraient par une ostéolyse péri-implant moindre par rapport aux TP. Dix veaux en bonne santé, de 3 semaines d'âge, ont été implantés avec les TP ou PS dans le métacarpe droit, à raison de 2 implants par veau. Les veaux ont été observés quotidiennement pour le confort et la boiterie et ont été euthanasiés à 28 jours. Les données recueillies comprenaient les radiographies à la chirurgie et à l'euthanasie et les mesures histomorphométriques de contact os-implant sur des échantillons non-décalcifiés avec les implants in situ. Les données ont été analysées en utilisant le test de Cochran-Mantel-Haenszel, une valeur de P <0,05 a été considérée comme significative. L'épaisseur corticale était plus importante pour les implants distaux que proximaux pour les deux groupes lors de la chirurgie (P = 0,03), mais était similaire entre les groupes (P > 0,3). Les veaux avec TP ont développé une boiterie plus tôt (au jour 21) que les veaux avec PS (P = 0,04). Histologiquement, il y avait plus de contact direct os-implant cortical pour les implants PS distaux que les implants TP (P = 0,04). La jonction métaphyso-diaphysaire osseuse où les implants proximaux étaient situés est impropre aux deux systèmes; chacun a un minimum de contact os-implant et de l'ostéolyse extensive. Le système PS n'ayant pas causé une ostéolyse importante lorsque implantés dans l'os diaphysaire et peut-être une alternative convenable aux TP pour des fractures comminutives des membres distaux. / Pin loosening is a common complication of transfixation pincasts (TP) in large animals, often necessitating premature removal before fracture healing. The excessive loads centered on the proximo-external and disto-internal cortices of the bone-pin interface cause osteolysis. Using a neonatal calf model, this project evaluated a novel pin-sleeve and ring cast system (PS) optimized to decrease peri-implant strain and evenly share stress at the bone-implant interface. It was hypothesized that PS would result in less peri-implant osteolysis compared to TP. Ten, 3-week-old, healthy calves were implanted with either TP or PS in the right metacarpus, 2 implants per calf. Calves were scored daily for lameness and were euthanized at day 28. Collected data included radiographs at surgery and euthanasia and histomorphometric measures of bone-implant contact on non-decalcified specimens with the implants in situ. Data was analyzed using Cochran-Mantel-Haenszel test; a P-value <.05 was considered significant. The cortical thickness was larger for distal implants than proximal implants for both groups at surgery (P = 0.03), but were similar between groups (P > 0.3). TP calves developed lameness sooner, at day 21, than PS calves (P = 0.04). Histologically, there was more direct cortical bone-implant contact for PS distal implants than TP implants (P = 0.04). The metaphyseal-diaphyseal junction where the proximal implants were situated is unsuitable bone for either system; each had minimal bone-implant contact and extensive osteolysis. The PS system did not cause significant osteolysis when instrumented in diaphyseal bone and is a suitable alternative to TP for comminuted distal limb fractures.

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.

Using the E. coli vaccine as a case study, this thesis examines the factors affecting the adoption of technologies with positive spillover (externality) effects related to food safety. Positive spillovers occur when the benefits from a technological innovation extend beyond the firm (farm) adopting the technology or they do not flow to the adopter. If there are insufficient incentives for the firm to adopt the new technology, adoption levels are sub-optimal, resulting in forgone benefits to society. These benefits include the avoidance of potential health costs, productivity loss and premature death costs as a result to exposure to E. coli O157:H7. Therefore, if the market incentives to adopt the technology are strengthened, adoption levels of the technology could reach socially optimal levels resulting in an improvement in food safety. This has been the case in the Canadian cattle industry, where the uptake of the E. coli vaccine by cow-calf producers has been very low. As such, a number of potential incentives to increase adoption of the vaccine were identified and assessed through a survey of cow-calf producers on the Prairies. Data from the survey were analyzed using a stated preference methodology, Best-Worst Scaling, and Latent Class cluster analysis. A Binary Probit Model was also used to examine the factors affecting willingness to adopt the vaccine. The results suggest that a significant number of producers were not aware of the existence of the E. coli vaccine. In addition, producers were most likely to be influenced in their adoption decisions by market/supply chain oriented incentives and government intervention incentives in the form of subsidies. On the other hand, incentives that were least likely to influence cow-calf producers’ decisions to adopt included government intervention through recommending use of vaccine and neighbours (other cow-calf producers) adopting the vaccine. The Latent Class cluster analysis revealed the existence of three unique producer clusters with different attitudes towards these incentives. Several socio-demographic variables and individual characteristics utilized in the Probit analysis were found to be determinants of a producer’s willingness to adopt an E. coli vaccine. The implications of this research are such that producer education and awareness campaigns may be utilized as tools for disseminating information on food safety technologies such as the E. coli vaccine. Furthermore, the market/supply chain incentives may be used to form potential market-based solutions to address the current low adoption rates. The existence of three unique producer clusters suggest that a one-size fits all strategy to encourage the adoption of the E. coli vaccine might be difficult to implement and thus a more targeted approach may be a feasible alternative.

The Salado region of Argentina covers 9.5 million ha, is located in the centre-East of the Buenos Aires Province, and concentrates about 6.9 million cattle. Cow-calf systems are predominant in the area. A simulation model was developed with the purpose of assisting in the design and evaluation of cow-calf systems in the Salado Region. The model was designed to produce long term simulations of the dynamic interactions between herd structure, climatic variation and farm management over periods of several decades using daily weather data, real or simulated. Existing models were used to describe soil, pasture and animal components of the farm, linked with management actions in a dynamic framework. The model was driven by decision rules entered by the user, which allowed the representation of management options that respond to changing farm conditions according to a predetermined policy. An object-oriented approach (OOA) was used in the design and implementation of the model. In the OOA, objects in the real world (e.g. cows, paddocks) are represented as objects in the computer program. The simulation of individual cows and individual paddocks made it possible to distribute feed resources flexibly among animals and provided many other points of flexibility in management strategies. The management strategies simulated in trying to improve cow-calf systems in the Salado region were based on Reserva 6, an experimental cow-calf farm located at the INTA-Balcarce Experimental Station. Every spring-summer, 30% of the area is devoted to make low quality hay (by cutting at high herbage mass), most of which is destined to provide maintenance feed for pregnant adult cows in winter. Cows are kept on a small paddock from weaning (March) to calving (August-September), during which time they receive 6-9kg DM of hay per day. A set of decision rules was developed to represent (on a 100ha farm) the management applied in Reserva 6 and, using this as a base system, a series of simulation experiments was conducted. Firstly, three preliminary experiments, aimed at gaining insight into the system and testing the model, were carried out. In the first of these, the effect of delaying the breeding season 15 and 30 days was analysed. The model was run over 30 consecutive years using a real weather sequence, 1970-2000, from INTA-Balcarce, for each scenario. It was found that, when the appropriate management variables (i.e. weaning and sale dates) were adjusted accordingly, changing the calving period had little effect on the productivity of a cow-calf system. In the second experiment, the dynamic consequences of three different heifer replacement policies on the production outcomes of the system were explored. The policies produced different patterns of oscillations in key farm outputs as a result of periodic behaviour in the age structure of the herd, and the differences between strategies were shown to be dependent on the environmental variability being simulated. The third experiment analysed different policies for hay use during the autumn-winter period, including a control strategy in which no hay was harvested or used. The results suggested that, provided hay was utilized on the farm, the pattern of use did not make much difference to liveweight production. Secondly, the long term performance, in terms of annual liveweight sold, of a range of hay quantity-quality combinations was compared. Each policy was simulated across a range of cow numbers (170 to 350, cows plus heifers in a 100ha farm) and was replicated 20 times. Each replication consisted of 50 years of random weather sampled from the real sequence (1970-2000). The benefit of using hay and the contrasts between the effects of different haymaking strategies on animal outputs increased as the cow numbers increased. The long term analysis suggested that the liveweight production of cow-calf farms, under a calendar-based haymaking policy like that followed in Reserva 6, would be maximized by harvesting 40-50% (but not more) of the total farm area and aiming to harvest hay at medium herbage mass (therefore medium quality). Therefore, the policy currently followed in Reserva 6 of allocating 30% of the farm to haymaking could be considered as conservative, and its productivity might be increased by making hay at lower herbage mass. Thirdly, the possible advantages of incorporating flexibility into the haymaking policy used in Reserva 6 were evaluated using the same experimental design. The results indicated that controlling haymaking in a flexible fashion, basing the decisions of closing, releasing and cutting paddocks on a simple pasture budget, would give the system productive advantages (i.e. increases in productivity and reductions in variability) in relation to a calendar-based approach. Using a flexible haymaking policy allows the manager to make more hay than required for the next winter, providing a buffer for the system. A flexible haymaking policy permitted significantly greater levels of herbage utilization by making large amounts of hay without negative effects on the carrying capacity of the system. A preliminary analysis of risk and costs highlighted major advantages in using hay in cow-calf systems, especially when a flexible approach to haymaking is implemented.

Made available in DSpace on 2014-06-11T19:26:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-28Bitstream added on 2014-06-13T20:33:50Z : No. of bitstreams: 1 monsalves_fm_me_jabo.pdf: 241550 bytes, checksum: 6693d5417f93dcd0ccd8d78b3166fcd2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os objetivos do presente trabalho foram calcular o valor econômico (VE) da característica taxa de prenhez de novilhas precoces e não precoces, em sistemas de produção de carne, com diferentes idades à primeira cobertura (14, 18 e 24 meses), supondo-se diferentes taxas de prenhez (20%, 30% e 40%) e diferentes épocas de descarte, além de, mediante a metodologia do fluxo de genes, avaliar o impacto do melhoramento desta característica em um rebanho, na obtenção de ganho genético para outras características. Foi utilizado um modelo bio-econômico para o cálculo do desempenho do rebanho, das receitas e custos de um sistema de produção utilizando animais da raça Nelore. O VE foi obtido aumentando-se em 1% a taxa de prenhez das novilhas precoces e não precoces, mantendo-se os níveis das demais características constantes. O fluxo gênico foi calculado considerando que a) as fêmeas entraram em reprodução entre 24 e 36 meses de idade e b) as fêmeas entraram em reprodução entre 12 e 24 meses de idade. Expressos com base no rebanho, os VE para a taxa de prenhez de novilhas variou de - R$ 3.652,17 a R$ 7.353,33. O VE foi maior quando as novilhas foram expostas aos touros aos 14 meses, indicando que a adoção desse manejo reprodutivo pode ser financeiramente compensadora. Quando as fêmeas entraram em reprodução entre 12 e 24 meses, a estabilização da proporção dos genes oriundos das fêmeas selecionadas ocorreu após 34 anos, fixando-se em 0,1322, enquanto que, se estas fêmeas tivessem iniciado a reprodução entre 24 e 36 meses, este tempo aumentaria para 44 anos fixando-se em 0,1045... / The aim of the present work was to calculate economic values for the pregnancy rate of Nellore heifers (precocious and not precocious), for cowcalf production systems, starting reproductive life at 14, 18 and 24 months, assuming differents pregnancy rates (20%, 30% and 40%) and differents culling periods. It was also evaluated the impact of improvement of this trait on the genetic and economic gain of other hipothetical traits in a population, using the gene flow methodology. A bio-economic model was used to calculate herd performance, revenues and costs of the beef production system. The economic values (EV) were obtained by increasing in 1% the original pregnancy rate of precocious and not precocious heifers, keeping the level of the other traits constant. The gene flow were calculaded considering the precocious and non precocious heifer production systems. When expressed on herd basis, the EV ranged from - R$ 3652.17 to R$ 7353.33. The highest EV was obtained when heifers were exposed to sires at 14 months of age. This result suggests that the adoption of such reproductive management may be economically compensating. The gene flow study showed that when females entered in reproduction between 12 and 24 months, gene proportions were estabilized after 34 years, fixing in 0.1322. If these females had started reproduction between 24 and 36 months, this estabilization period would be increased to 44 years, fixing in 0.1045. Assuming a genetic-economical superiority for a given trait of interest, expressed in both males and female of R$ 30.00, the genetic economical gain would be obtained in a shorter time and the expected response after one round of selection would have a greater magnitude in the first case (R$ 3.97) when compared with the second case (R$ 3.13)... (Complete abstract, click electronic access below)

Made available in DSpace on 2016-12-08T16:24:16Z (GMT). No. of bitstreams: 1 PGCA14MA127.pdf: 678955 bytes, checksum: 695ebbffb3866d730546c6e564f98286 (MD5) Previous issue date: 2014-02-21 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The access to an exclusive area of legumes is an alternative to reduce of nitrogen fertilizers and improve animal performance. The aim of this study was to assess the animal performance of steers grazing dwarf elephant grass (Pennisetum purpureum Schum. cv. BRS Kurumi) mixed peanut (Arachis pintoi cv. Amarillo ) with two times in the exclusive area of peanut (Arachis pintoi cv. Amarillo ): two (7:00 9:00 pm) and six hours (7:00 to 13:00 ) by day. Twelve steers (219 ± 28.8 kg of LW) were assigned in a completely randomized design and data were submitted to analysis of variance considering repeated measures. Average daily gain was similar (average = 1.16 kg/day) between treatments and grazing time in the morning and total grazing time were higher (P < 0.01) in animals with two hours of access to an exclusively peanut area compared to animals with six hours of access to legume. Two hours by day of access to a tropical legume area is enough to improve the animal performance / O pastejo horário em área exclusiva de amendoim forrageiro é uma alternativa para diminuir o uso de fertilizantes nitrogenados e aumentar o desempenho animal. O objetivo do trabalho foi avaliar o desempenho de novilhos pastejando capim-elefante anão (Pennisetum purpureum Schum. BRS Kurumi) consorciado com amendoim forrageiro (Arachis pintoi cv. Amarillo) com dois tempos de permanência em área exclusiva de amendoim forrageiro (Arachis pintoi cv. Amarillo): duas (7:00 às 9:00 h) e seis horas (7:00 às 13:00 h). Foram utilizados 12 novilhos machos oriundos de cruza industrial, com peso vivo médio de 219 ± 28,8 kg. Foi utilizado um delineamento experimental completamente casualizado e os dados foram submetidos à análise de variância considerando as medidas repetidas no tempo por intermédio do procedimento MIXED do SAS versão 9.2. O ganho médio diário não diferiu entre os tratamentos (média = 1,16 kg/dia). O tempo de pastejo pela manhã (horário do pastejo na leguminosa) e o tempo total de pastejo foram maiores (P<0,01) nos animais que tiveram duas horas/dia de acesso ao amendoim forrageiro. A permanência de bovinos em área de amendoim forrageiro por duas horas possibilita o mesmo desempenho que animais com seis horas de acesso a mesma leguminosa forrageira

Resumo: Os objetivos do presente trabalho foram calcular o valor econômico (VE) da característica taxa de prenhez de novilhas precoces e não precoces, em sistemas de produção de carne, com diferentes idades à primeira cobertura (14, 18 e 24 meses), supondo-se diferentes taxas de prenhez (20%, 30% e 40%) e diferentes épocas de descarte, além de, mediante a metodologia do fluxo de genes, avaliar o impacto do melhoramento desta característica em um rebanho, na obtenção de ganho genético para outras características. Foi utilizado um modelo bio-econômico para o cálculo do desempenho do rebanho, das receitas e custos de um sistema de produção utilizando animais da raça Nelore. O VE foi obtido aumentando-se em 1% a taxa de prenhez das novilhas precoces e não precoces, mantendo-se os níveis das demais características constantes. O fluxo gênico foi calculado considerando que a) as fêmeas entraram em reprodução entre 24 e 36 meses de idade e b) as fêmeas entraram em reprodução entre 12 e 24 meses de idade. Expressos com base no rebanho, os VE para a taxa de prenhez de novilhas variou de - R$ 3.652,17 a R$ 7.353,33. O VE foi maior quando as novilhas foram expostas aos touros aos 14 meses, indicando que a adoção desse manejo reprodutivo pode ser financeiramente compensadora. Quando as fêmeas entraram em reprodução entre 12 e 24 meses, a estabilização da proporção dos genes oriundos das fêmeas selecionadas ocorreu após 34 anos, fixando-se em 0,1322, enquanto que, se estas fêmeas tivessem iniciado a reprodução entre 24 e 36 meses, este tempo aumentaria para 44 anos fixando-se em 0,1045...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of the present work was to calculate economic values for the pregnancy rate of Nellore heifers (precocious and not precocious), for cowcalf production systems, starting reproductive life at 14, 18 and 24 months, assuming differents pregnancy rates (20%, 30% and 40%) and differents culling periods. It was also evaluated the impact of improvement of this trait on the genetic and economic gain of other hipothetical traits in a population, using the gene flow methodology. A bio-economic model was used to calculate herd performance, revenues and costs of the beef production system. The economic values (EV) were obtained by increasing in 1% the original pregnancy rate of precocious and not precocious heifers, keeping the level of the other traits constant. The gene flow were calculaded considering the precocious and non precocious heifer production systems. When expressed on herd basis, the EV ranged from - R$ 3652.17 to R$ 7353.33. The highest EV was obtained when heifers were exposed to sires at 14 months of age. This result suggests that the adoption of such reproductive management may be economically compensating. The gene flow study showed that when females entered in reproduction between 12 and 24 months, gene proportions were estabilized after 34 years, fixing in 0.1322. If these females had started reproduction between 24 and 36 months, this estabilization period would be increased to 44 years, fixing in 0.1045. Assuming a genetic-economical superiority for a given trait of interest, expressed in both males and female of R$ 30.00, the genetic economical gain would be obtained in a shorter time and the expected response after one round of selection would have a greater magnitude in the first case (R$ 3.97) when compared with the second case (R$ 3.13)... (Complete abstract, click electronic access below) / Orientadora: Lúcia galvão de Albuquerque / Coorientadora: Vera Lúcia Cardoso / Banca: Henrique Nunes de Oliveira / Banca: Maria Eugênia Zerlotti Mercadante / Mestre

Made available in DSpace on 2014-07-29T15:13:50Z (GMT). No. of bitstreams: 1 Tese_Marcelo_Godoy.pdf: 524217 bytes, checksum: a994c2910234ccd5ab66b87e967a3bbf (MD5) Previous issue date: 2009-02-26 / Were used primiparous cows, zebuine, calved than received in the postpartum period, low intake isoenergetic supplements, in pasture of Brachiaria brizantha cv. Marandu, with twenty cows per treatment in a randomized design, where FA: the low intake supplement (LIS) with inclusion of protected fat, CO: LIS with the inclusion of meal corn and MS: only mineral supplement. Evaluated the body weight of cows (BW) of calves (BWC) and body condition score (BCS) of cows inthe postpartum period, at every 28 days, effect of sex of calf in the BW medium (BWm) and in the BCS medium (BCSm) of cows, the average daily weight gain of cows (ADWG) and calves (ADWGC) and pregnancy rate (PR). The supplementation increased the BW of the cows in FA and CO without difference between them (P> 0.05), already the MI did not differ from SM de108 to 136 days postpartum (P> 0.05). The BWC of FA and CO did not differ (P> 0.05) among them and were higher (P <0.05) than the MS 108 until 192 days postpartum, and heavier at weaning. The cows of FA had BCS higher (P <0.05) than the other treatments from 80 to 192 days postpartum. The ADWG of FA and CO did not differ among them (P> 0.05) and were higher than SM (P <0.05). The ADWGC of FA and CO were similar (P> 0.06), and higher than SM (P <0.06). Cows that nursing males had lower BWm and BCSm that those nursing females (P <0.05). The cows of FA had higher PR (P <0.01) / Foram utilizadas sessenta vacas de corte, primíparas, zebuínas, paridas, com 48 do grupo genético Guzonel e 12 da raça Nelore, que receberam no pós-parto, suplementos isoenergéticos de baixo consumo à vontade e mantidas em pastagem de Brachiaria brizantha cv. Marandu, sendo vinte animais por tratamento, distribuídos uniformemente de acordo com o grupo genético, peso corporal, escore de condição corporal e número de dias pós-parto, onde AG: suplemento de baixo consumo com a inclusão de sabões de cálcio de ácidos graxos (gordura protegida), MI: suplemento de baixo consumo com a inclusão de quirera de milho e SM: somente suplemento mineral. Foi incluído quirera de milho, no tratamento MI, com o intuito de deixar o suplemento isoenergético em relação à quantidade de gordura protegida no tratamento AG. Avaliou-se o peso corporal das vacas (PCV) e dos bezerros (PCB) e escore de condição corporal (ECC) das vacas no período pós-parto, obtidos a cada 28 dias, além do efeito do sexo do bezerro sobre o peso corporal (PCm) e o escore de condição corporal (ECCm) médios das vacas e os ganhos médios diários de peso das vacas (GMDV) e bezerros (GMDB) e o índice de prenhez. Para aferir a produção de leite total (PLT), produção média diária de leite (PLm), produção de leite (PL) no período pós-parto, composição do leite e o efeito do sexo do bezerro na PL, foram utilizadas somente dez vacas de cada tratamento com menor período de dias pós-parto, com seis vacas do grupo genético Guzonel e quatro da raça Nelore (média de 24 dias) ordenhadas a cada 28 dias até 80 dias pós-parto e a cada 56 dias pós-parto dos 80 até 192 dias pós-parto. A suplementação conseguiu aumentar o PC no período pós-parto das vacas dos tratamentos AG e MI os quais não diferiram entre si (P>0,05), sendo que o MI não diferiu do SM de108 a 136 dias pós-parto. O GMDV do AG e MI não diferiram entre si (P>0,01), mas foram superiores ao SM (P<0,01) (0,352 e 0,321 vs. 0,143 kg/dia, respectivamente). O PCB dos tratamentos AG e MI foram semelhantes (P>0,05), no entanto, foram superiores (P<0,05) ao SM dos 108 até 192 dias pós-parto e, consequentemente, mais pesados ao desmame (192 dias de idade) (182,36, 175,23 e 148,68 kg, respectivamente). O GMDB dos bezerros do AG e MI, não diferiram entre si (P>0,06), mas foram maiores que o SM (P<0,06) (0,736 e 0,688 vs. 0,655 kg/dia, respectivamente). Aos 192 dias pós-parto as vacas do tratamento AG tiveram ECC superior (P<0,05) aos demais tratamentos. Já o PC das vacas do tratamento MI não diferiu do AG (P>0,05) e foi maior que o SM (P<0,05). Vacas que amamentaram machos tiveram menores PCV e ECC em comparação aquelas que amamentavam fêmeas (P<0,05) (321,48 vs. 337,22 kg e 2,04 vs. 2,14, respectivamente). As vacas dos tratamentos AG e MI tiveram maiores índices de prenhez que as vacas do SM (P<0,05) (68,48, 42,11 vs. 5,00%, respectivamente). As vacas que ingeriram sabões cálcio de ácidos graxos insaturados no suplemento alcançaram maior índice de prenhez (P<0,01). A suplementação de baixo consumo (AG e MI) proporcionou maior PLT (295,05 e 311,03 vs. 179,21, respectivamente) e PLm (1,52 e 1,61 vs. 1,11, respectivamente) quando comparado ao SM (P<0,05). A PL no período pós-parto teve diminuição linear em todos os tratamentos. A porcentagem de lactose (LAC), gordura (G), estrato seco total (EST) e estrato seco desengordurado (ESD) no leite se mantiveram constantes (P>0,05) no período pós-parto, ao contrário da proteína (PROT) que aumentou (P<0,05). O teor de G no tratamento SM foi superior aos demais tratamentos aos 80 dias pós-parto. Já em AG encontrou-se G menor em relação aos demais tratamentos aos 136 dias pós-parto (P<0,05), e MI e SM diferiram entre si. Dos 136 dias pós-parto em diante os teores de gordura não diferiram entre os tratamentos (P>0,05). A inclusão de gordura protegida afetou apenas os teores médios de G com 1,73% vs. 1,95% e 1,95%, respectivamente, para AG, MI e SM, mas não alterou os demais componentes do leite analisados. A produção e composição do leite não foram afetadas pelo sexo do bezerro (P>0,05). Concluise com este estudo que a suplementação de baixo consumo melhorou o PC, ECC, PCB, GMDV, GMDB, PLT e PLm, já a inclusão de ácidos graxos insaturados no suplemento diminuiu os teores médios de G e proporcionou maior ECC e índice de prenhez