Bovine herpesvirus-1 (BoHV-1) is a pathogen of cattle, which most commonly affects the upper respiratory tract to cause infectious bovine rhinotracheitis (IBR). It can also spread systemically to cause fatalities in calves and abortion in pregnant cattle. The virally encoded mechanisms of this systemic spread are poorly understood and therefore have been addressed by comparing isolates from the respiratory form of disease with isolates that have previously demonstrated systemic spread. A survey of 400 bovine abortions in Scotland from 2007-2009 demonstrated a BoHV-1 prevalence of 2.5%. It also demonstrated the importance of real-time PCR as a diagnostic technique when analysing samples from natural cases. The study of BoHV-1 distribution in the placenta and foetal tissue provided support for a haematogenous route of viral spread. Whole genome sequencing of 11 BoHV-1 isolates using Illumina Solexa technology was completed and added significantly to the sequencing data of BoHV-1. In terms of identifying genetic variation between isolates causing respiratory infection and those causing systemic infection, no differences were observed by SNP or phylogenetic analysis. However, there were significant differences in the extent of variation between essential and non-essential genes, which may reflect the evolution of BoHV-1. An in vivo challenge of the natural host to compare two isolates representing the respiratory and systemic forms of infection showed differences in clinical presentation, histopathological analysis, viral distribution and viral transcript expression, measured throughout the infection period. In particular, it was noted that a more severe ocular infection, rather than respiratory based infection was caused by infection with the ‘systemic’ isolate. Differences in the tropism of the virus were observed early in the infection with the ‘systemic’ isolate showing more association with the nasal mucosa than the trachea. The tonsils demonstrated different responses to the virus and differences in viral transcript expression. However, this may simply represent different stages of virus infection. Both isolates demonstrated spread to the brain at day 10 post infection. In vitro methods were used to study the differences in transcript expression in more detail. In a bovine turbinate cell infection faster replication of the respiratory isolate was observed by a significantly faster development of cytopathic effect. This was also reflected in the higher gene expression levels of the respiratory isolate in the first 12 hours of infection. More isolates were studied to investigate whether these differences were consistent, or as suggested by the sequencing, random differences between isolates. Six isolates were used to infect bovine lung slices. Differences in transcript expression were minimal between the two isolate groups. Immunofluorescence did not provide the sensitivity to detect virus in all samples where PCR showed replication. This compromised the study of co-localization but did show promise as a model to study the tropism of respiratory viruses. Overall, this work has showed that systemic spread of BoHV-1 does not appear to be controlled by virally encoded mechanisms. The in vivo experimental infection suggested host factors may play a large part. Further work is also needed to consider any differences that may exist between reactivated virus and the original infecting isolate.

Um dos grandes problemas que afetam a produção in vitro de embriões é a variação entre touros em relação à fertilidade e o maior nascimento de embriões do sexo masculino. Muitos fatores podem alterar a razão de 1:1 entre os gêneros tanto na produção in vitro de embriões, como no método de Inseminação Artificial. No sentido de tentar alterar esta proporção sexual in vitro, estudamos em um primeiro momento, a variação entre touros no desenvolvimento de embriões machos e fêmeas, distribuídos nas fases de blastocisto jovem, blastocisto, blastocisto expandido e blastocisto eclodido, bem como, a proporção macho: fêmea em relação a fase do blastocisto. Para tanto, oócitos foram coletados de ovários oriundos de matadouro e maturados em meio de maturação em incubadora por 24h. Espermatozóides viáveis de 17 touros do Programa de Melhoramento Genético da Raça Nelore, obtidos por centrifugação em gradiente de Percoll, foram utilizados para Fecundação in vitro. Após 12h, os supostos zigotos foram cultivados em meio de cultivo e células do cumulus em incubadora. Ao sétimo dia após a fertilização in vitro foi feita a seleção dos blastocistos viáveis que foram sexados com a utilização de primers Y-específico bovino e autossômico bovino, com visualização dos fragmentos amplificados em gel de agarose. Posteriormente, para obtenção de maior conhecimento a respeito dos animais testados, coletamos dados de progênie a campo destes animais e verificamos a proporção sexual de seus filhos nascidos pelo método da inseminação artificial, monta natural e possíveis correlações com características quantitativas. Diferenças entre touros foram observadas em relação à proporção dos sexos para as fases de blastocisto inicial e blastocisto expandido. Não foi observado desvio da proporção sexual em relação ao touro utilizado na produção in vitro de embriões e progênie a campo. Nosso dados sugerem que é possível alterar a proporção macho:fêmea em sistemas de produção in vitro de embriões pela seleção do estágio do blastocisto para transferência, e ainda, sugerem que touros apresentam variação em relação ao desenvolvimento in vitro de embriões machos e fêmeas de acordo com o estágio do blastocisto. / Some of the main problems that affect the in vitro production of embryos is the variation among bulls in relation to fertility and the greater birth of male embryos. Many factors can change the ratio 1:1 between the genders, both in the in vitro production of embryos and in the method of artificial insemination. To try to change this sex ratio in vitro, we studied at first, the variation among bulls in the development of female and male embryos, the blastocyst-stage distributed in young blastocyst, blastocyst, expanded blastocyst and hatched blastocyst and the proportion male: female in relation to the blastocyst stage. For this, oocytes were collected from slaughterhouse ovaries and matured in maturation medium in an incubator for 24h. Viable sperm from 17 bulls belonging to the Breeding Program of Nellore, obtained by Percoll gradient centrifugation were used for in vitro fertilization. After 12 hours, the presumptive zygotes were cultured in culture medium and cumulus cells in an incubator. After 168 hours of in vitro fertilization the viable embryos in the blastocyst stage were classified. The determination of the sex of the blastocysts was performed by Polymerase Chain Reaction (PCR) using a Y-specific sequence and bovine autosomal sequence visualized in agarose gel. Data analysis was conducted using the Statistical Analysis System software. Later, to obtain more knowledge about the animals tested, data was collected from the field progeny of these animals and established the sex ratio of the offspring produced by the method of artificial insemination, natural mating and possible correlations with quantitative traits. Differences between bulls were observed relating to the proportion of genders at the initial stages of blastocyst and expanded blastocyst. No deviation was observed in the sex ratio in relation to the bull used for in vitro production of embryos and offspring in the field. Our data suggest that it is possible to change the male to female proportion in production systems of in vitro embryos through the selection of the blastocyst stage for transfer, and also suggest that bulls show variation in relation to the in vitro development of male and female embryos, depending on the blastocyst stage.

Um dos grandes problemas que afetam a produção in vitro de embriões é a variação entre touros em relação à fertilidade e o maior nascimento de embriões do sexo masculino. Muitos fatores podem alterar a razão de 1:1 entre os gêneros tanto na produção in vitro de embriões, como no método de Inseminação Artificial. No sentido de tentar alterar esta proporção sexual in vitro, estudamos em um primeiro momento, a variação entre touros no desenvolvimento de embriões machos e fêmeas, distribuídos nas fases de blastocisto jovem, blastocisto, blastocisto expandido e blastocisto eclodido, bem como, a proporção macho: fêmea em relação a fase do blastocisto. Para tanto, oócitos foram coletados de ovários oriundos de matadouro e maturados em meio de maturação em incubadora por 24h. Espermatozóides viáveis de 17 touros do Programa de Melhoramento Genético da Raça Nelore, obtidos por centrifugação em gradiente de Percoll, foram utilizados para Fecundação in vitro. Após 12h, os supostos zigotos foram cultivados em meio de cultivo e células do cumulus em incubadora. Ao sétimo dia após a fertilização in vitro foi feita a seleção dos blastocistos viáveis que foram sexados com a utilização de primers Y-específico bovino e autossômico bovino, com visualização dos fragmentos amplificados em gel de agarose. Posteriormente, para obtenção de maior conhecimento a respeito dos animais testados, coletamos dados de progênie a campo destes animais e verificamos a proporção sexual de seus filhos nascidos pelo método da inseminação artificial, monta natural e possíveis correlações com características quantitativas. Diferenças entre touros foram observadas em relação à proporção dos sexos para as fases de blastocisto inicial e blastocisto expandido. Não foi observado desvio da proporção sexual em relação ao touro utilizado na produção in vitro de embriões e progênie a campo. Nosso dados sugerem que é possível alterar a proporção macho:fêmea em sistemas de produção in vitro de embriões pela seleção do estágio do blastocisto para transferência, e ainda, sugerem que touros apresentam variação em relação ao desenvolvimento in vitro de embriões machos e fêmeas de acordo com o estágio do blastocisto. / Some of the main problems that affect the in vitro production of embryos is the variation among bulls in relation to fertility and the greater birth of male embryos. Many factors can change the ratio 1:1 between the genders, both in the in vitro production of embryos and in the method of artificial insemination. To try to change this sex ratio in vitro, we studied at first, the variation among bulls in the development of female and male embryos, the blastocyst-stage distributed in young blastocyst, blastocyst, expanded blastocyst and hatched blastocyst and the proportion male: female in relation to the blastocyst stage. For this, oocytes were collected from slaughterhouse ovaries and matured in maturation medium in an incubator for 24h. Viable sperm from 17 bulls belonging to the Breeding Program of Nellore, obtained by Percoll gradient centrifugation were used for in vitro fertilization. After 12 hours, the presumptive zygotes were cultured in culture medium and cumulus cells in an incubator. After 168 hours of in vitro fertilization the viable embryos in the blastocyst stage were classified. The determination of the sex of the blastocysts was performed by Polymerase Chain Reaction (PCR) using a Y-specific sequence and bovine autosomal sequence visualized in agarose gel. Data analysis was conducted using the Statistical Analysis System software. Later, to obtain more knowledge about the animals tested, data was collected from the field progeny of these animals and established the sex ratio of the offspring produced by the method of artificial insemination, natural mating and possible correlations with quantitative traits. Differences between bulls were observed relating to the proportion of genders at the initial stages of blastocyst and expanded blastocyst. No deviation was observed in the sex ratio in relation to the bull used for in vitro production of embryos and offspring in the field. Our data suggest that it is possible to change the male to female proportion in production systems of in vitro embryos through the selection of the blastocyst stage for transfer, and also suggest that bulls show variation in relation to the in vitro development of male and female embryos, depending on the blastocyst stage.