Aspectos morfofisiológicos e biotécnicas aplicadas à reprodução de novilhas bovinas e búfalas pré-púberes / Morphophysiological aspects and biotechnologies applied to the reproduction of prepubertal bovine and buffalo heifers

A puberdade corresponde ao momento da primeira ovulação, que culmina com o desenvolvimento final dos órgãos e estruturas envolvidas no controle neuro-endócrino reprodutivo. É um fenômeno multifatorial com grande impacto na vida produtiva das futuras matrizes e em sua eficiência econômica, ocorrendo muitas interações entre os fatores internos e externos. A idade da puberdade está relacionada ao peso corporal, que possui grandes efeitos da genética do animal e sua interação com o ambiente, especialmente a nutrição e interação social com machos. Algumas espécies, como os bubalinos, sofrem efeito de outros elementos ambientais, como a luminosidade e o fotoperíodo. A puberdade novilhas búfalas ou bovinas pode ser adiantada por meio do emprego de biotécnicas: indução da puberdade ou inseminação artificial em tempo fixo (IATF). Em ambas, os protocolos baseiam-se, principalmente, em aplicação de progestágeno associado com fonte de estradiol; mas a indução também pode ser realizada utilizando outros hormônios, como hormônio liberador de gonadotrofinas, prostaglandinas e gonadotrofina coriônica equina. No emprego da IATF, novilhas pré-púberes podem ser induzidas e inseminadas com outro protocolo de sincronização ou podem ser inseminadas com o mesmo protocolo de IATF, podendo aumentar as taxas de prenhez e diminuir os custos. Adiantando a puberdade, ocorre incremento na produção, melhorando a eficiência econômica da atividade pecuária.(AU)

Puberty corresponds to the moment of the first ovulation, which culminates in the final development of the organs and structures involved in the neuro-endocrine control of reproduction. It is a multifactorial phenomenon with a great impact on the productive life of future matrices and their economic efficiency, with many interactions between internal and external factors. The age of puberty is related to body weight, which has great effects on the animal's genetics and its interaction with the environment, especially nutrition and social interaction with males. Some species, such as buffalo, are affected by other environmental elements, such as luminosity and photoperiod. Puberty in buffaloes and bovine heifers can be advanced through the use of biotechniques: induction of puberty or timed artificial insemination (TAI). In both, the protocols are mainly based on the application of progestogen associated with a source of estradiol; but induction can also be performed using other hormones, such as gonadotropin-releasing hormone, prostaglandins and equine chorionic gonadotropin. In the employment of the TAI, prepubertal heifers can be induced and inseminated with another synchronization protocol or they can be inseminated with the same TAI protocol, which can increase pregnancy rates and decrease costs. Advancing puberty, there is an increase in production, improving the economic efficiency of livestock activity.(AU)

Papel da nutrição sobre a reprodução ovina / The role of nutrition on reproduction of sheep

A nutrição exerce grande influência na eficiência reprodutiva tanto de forma direta, no fornecimento de nutrientes para as funções fisiológicas, quanto indireta na síntese de hormônios e na quantidade de receptores nas células e suas interações metabólicas. O monitoramento do escore de condição corporal ainda é a ferramenta de diagnóstico nutricional mais utilizada. No entanto, os trabalhos feitos no Brasil têm demonstrado que a escala de escore ainda carece de avaliação com adaptação para ovinos deslanados criados no Brasil. Além desta influência dita estática, a nutrição exerce um efeito agudo ou imediato que também é explorado em condições de ambiente produtivo, com é o caso do flushing, que consiste em uma suplementação em níveis elevados, acima da exigência dos animais com o objetivo de estimular a taxa de ovulação, tamanho dos folículos ovarianos e a sobrevivência embrionária. O efeito do flushing já é bastante documentado, assim como suas limitações. Os avanços nesta linha são o flushing de nutrientes com reconhecido papel na reprodução como os ácidos graxos, que devem ser mais explorados pela pesquisa. Por fim, um dos campos mais estudados atualmente é o de programação fetal, ou seja, o impacto da nutrição durante a gestação sobre os aspectos produtivos e reprodutivos da nova geração. O conhecimento nesta área tem demonstrado cada vez mais que o sucesso na produção animal começa muito antes do nascimento e que mesmo o desenvolvimento embrionário pode impactar em toda a vida produtiva do animal.(AU)

Nutrition plays a major influence on reproductive efficiency directly, through supply of nutrients to the physiological functions, and indirectly in the synthesis of hormones and the amount of receptors on cells and their metabolic interactions. The monitoring of body condition score is still the most widely used tool to nutritional monitoring. However, works done in Brazil have shown that the scale score still lacks evaluation and adapted to hair sheep raised in Brazil. Besides this influence, nutrition plays an acute or immediate effect which is also explored in the production system, as the flushing o nutrients, which consists of a supplementation at levels above the requirement of the animals aiming stimulate ovulation rate, size of ovarian follicles and embryo survival. The effect of flushing is already well documented, as well as its limitations. Advances in this issue are the flushing of nutrients with recognized role in reproduction such as fatty acid which must be more studied. Finally, one of the most studied fields currently is the fetal programming or the impact of nutrition during pregnancy on productive and reproductive aspects of the new generation. The increasing knowledge in this area has demonstrated that the success in animal production begins before birth and even in the early embryonic development impacting the entire productive life of the animal.(AU)

Papel da nutrição sobre a reprodução ovina / The role of nutrition on reproduction of sheep

A nutrição exerce grande influência na eficiência reprodutiva tanto de forma direta, no fornecimento de nutrientes para as funções fisiológicas, quanto indireta na síntese de hormônios e na quantidade de receptores nas células e suas interações metabólicas. O monitoramento do escore de condição corporal ainda é a ferramenta de diagnóstico nutricional mais utilizada. No entanto, os trabalhos feitos no Brasil têm demonstrado que a escala de escore ainda carece de avaliação com adaptação para ovinos deslanados criados no Brasil. Além desta influência dita estática, a nutrição exerce um efeito agudo ou imediato que também é explorado em condições de ambiente produtivo, com é o caso do flushing, que consiste em uma suplementação em níveis elevados, acima da exigência dos animais com o objetivo de estimular a taxa de ovulação, tamanho dos folículos ovarianos e a sobrevivência embrionária. O efeito do flushing já é bastante documentado, assim como suas limitações. Os avanços nesta linha são o flushing de nutrientes com reconhecido papel na reprodução como os ácidos graxos, que devem ser mais explorados pela pesquisa. Por fim, um dos campos mais estudados atualmente é o de programação fetal, ou seja, o impacto da nutrição durante a gestação sobre os aspectos produtivos e reprodutivos da nova geração. O conhecimento nesta área tem demonstrado cada vez mais que o sucesso na produção animal começa muito antes do nascimento e que mesmo o desenvolvimento embrionário pode impactar em toda a vida produtiva do animal.

Nutrition plays a major influence on reproductive efficiency directly, through supply of nutrients to the physiological functions, and indirectly in the synthesis of hormones and the amount of receptors on cells and their metabolic interactions. The monitoring of body condition score is still the most widely used tool to nutritional monitoring. However, works done in Brazil have shown that the scale score still lacks evaluation and adapted to hair sheep raised in Brazil. Besides this influence, nutrition plays an acute or immediate effect which is also explored in the production system, as the flushing o nutrients, which consists of a supplementation at levels above the requirement of the animals aiming stimulate ovulation rate, size of ovarian follicles and embryo survival. The effect of flushing is already well documented, as well as its limitations. Advances in this issue are the flushing of nutrients with recognized role in reproduction such as fatty acid which must be more studied. Finally, one of the most studied fields currently is thefetal programming or the impact of nutrition during pregnancy on productive and reproductive aspects of the new generation. The increasing knowledge in this area has demonstrated that the success in animal production begins before birth and even in the early embryonic development impacting the entire productive life of the animal.

Progesterone production and metabolism and its role before, during and after artificial insemination influencing the fertility of high producing dairy cows / Produção e metabolismo da progesterona e seu papel antes, durante e depois da inseminação artificial influenciando a fertilidade de vacas leiteiras de alta produção

Background: Efficient reproduction performance is important for optimal profitability on dairy operations. Unfortunately, most dairy farms do not attain optimal reproduction due to many factors including management, health, and physiology of high-producing dairy cows. The physiology limitations involved in reproduction of lactating dairy cows are complex and becoming worse as milk production increases. But many variables related to the interactions between nutrition, the complexity of some hormonal systems, and altered reproductive patterns in dairy cattle have been elucidated. This review will focus on the role of progesterone (P4) in reproduction of the lactating dairy cow. Review: Progesterone is a steroid hormone primarily secreted by the corpus luteum (CL) and placenta. Adequate circulating P4 concentrations are essential for establishment and maintenance of pregnancy. Thus, because of the central role of progesterone on fertility, this manuscript reviews the effect of progesterone (P4) during timed AI protocols in lactating dairy cows. Two sections summarize how P4 is produced and a model attempts to explain how P4 is metabolized in high producing dairy cows. Circulating P4 is determined by a balance between P4 production and P4 metabolism and stimulatory and inhibitory pathways regulating this balance are complex. However in dairy cattle, the volume of luteal tissue is a

A concentração circulante de P4 no organismo é determinada pela razão entre sua produção pelo CL, e, por outro lado, pelo seu metabolismo nas células hepáticas. Nas vacas leiteiras de alta produção existe um desbalanço nesta equação, pois a P4 produzida é rapidamente metabolizada por uma taxa extremamente alta de fluxo sanguíneo que passa através do fígado. Diferentes abordagens para manipular a concentração circulante de P4, e em momentos diferentes em relação a IA, têm sido realizadas no intuito de compreender e, então, de compensar este desbalanço na P4 circulante causado pelos altos níveis de produção de leite. [...]

Produção e metabolismo da progesterona e seu papel antes, durante e depois da inseminação artificial influenciando a fertilidade de vacas leiteiras de alta produção / Progesterone Production and Metabolism and Its Role Before, during and after Artificial Insemination Influencing the Fertility of High Producing Dairy Cows

Background: Efficient reproduction performance is important for optimal profitability on dairy operations. Unfortunately, most dairy farms do not attain optimal reproduction due to many factors including management, health, and physiology of high-producing dairy cows. The physiology limitations involved in reproduction of lactating dairy cows are complex and becoming worse as milk production increases. But many variables related to the interactions between nutrition, the complexity of some hormonal systems, and altered reproductive patterns in dairy cattle have been elucidated. This review will focus on the role of progesterone (P4) in reproduction of the lactating dairy cow. Review: Progesterone is a steroid hormone primarily secreted by the corpus luteum (CL) and placenta. Adequate circulating P4 concentrations are essential for establishment and maintenance of pregnancy. Thus, because of the central role of progesterone on fertility, this manuscript reviews the effect of progesterone (P4) during timed AI protocols in lactating dairy cows. Two sections summarize how P4 is produced and a model attempts to explain how P4 is metabolized in high producing dairy cows. Circulating P4 is determined by a balance between P4 production and P4 metabolism and stimulatory and inhibitory pathways regulating this balance are complex. However in dairy cattle, the volume of luteal tissue is a primary factor regulating P4 production; although, inadequate P4 is generally due to high metabolism of P4 resulting from extremely elevated liver blood flow. If P4 production is increased by an increase in luteal tissue without a change in liver blood flow, then circulating P4 will increase. Conversely, if there is an increase in liver blood fl ow then there will be a corresponding decrease in circulating P4 even though P4 production has not been altered. Thus, an understanding of regulation of circulating P4 must carefully consider the factors regulating P4 production and its metabolism. As will be discussed below, over 80% of P4 production during the estrous cycle of the cow is due to constitutive P4 production by the large luteal cell. Regulation of constitutive P4 production by the CL does not appear to require stimulatory pathways but can be dramatically decreased during luteolysis induced by exogenous or endogenous prostaglandin F2α (PGF2α). Conversely, although liver enzymes involved in P4 metabolism can be regulated, we speculate in this model that the primary determinant of P4 metabolism in the lactating cow is related to the rate of liver blood flow. These concepts are more fully discussed below. Three sections summarize the role of P4 concentrations prior to breeding, near the time of breeding, and after breeding. During timed AI protocols, elevations in P4 are achieved by increasing number of CL by ovulation of accessory CL or by supplementation with exogenous P4. Elevating P4 prior to the timed AI generally decreases double ovulation and can increase fertility to the timed AI. Near the time of AI, slight elevations in circulating P4 can dramatically reduce fertility with inadequate luteolysis to the PGF2α treatment prior to timed AI, being the underlying cause of this problem. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI with primarily marginal elevations (<5%). Conclusion: Previous research has provided substantial insight into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future studies on P4 manipulation to improve timed AI protocols.

Epigenetics and reproduction and the developmental origins of health and disease

Over the past century, studies of development and reproductive biology have transcended our understandings of what constitutes heritability and the acquisition of phenotypic traits from one generation to the next. While our early research defined “particulate genetic inheritance” as a primary mechanism for the heritability of traits, more recent work in past decades in lower eukaryotes and early mammalian species have included “epigenetic” (or “upon the genome”) modifications to the genomic backbone as a primary mechanism in the complex series of molecular interactions which ultimately enabling coordinate regulation of development. In recent years such investigations have evolved to focus on the role of epigenetic modifications to DNA and core histones in higher mammalian developmental processes. What are epigenetic modifications? While almost all cells of an individual bear near identical genomic constitutions, phenotype is ultimately determined by the gene expression profile. Gene expression is maintained by two major mechanisms: (1) transcription factors and post-transcriptional modifiers, and (2) epigenetic modifications, in particular DNA and core-histone modifications, that can be inherited during mitosis from one cell generation to another. This epigenetic code is essential in directing the tremendous number of gene expression changes that must occur for a cell to leave its pluripotent state and become fully differentiated to then function in adaptive homeostasis processes of the organism. It may therefore be stated that one’s epigenetic signatures are the net outcome of genotype, developmental lineage, and environmental exposures. These epigenetic signatures are stable and/or heritable patterns of gene activity and expression that do not result from changes in the genomic sequence. Covalent modifications to histones (i.e., histone H3 acetylation and methylation) and DNA methylation (meCpG) are examples of such epigenetic events which collectively...

Epigenetics and reproduction and the developmental origins of health and disease

Over the past century, studies of development and reproductive biology have transcended our understandings of what constitutes heritability and the acquisition of phenotypic traits from one generation to the next. While our early research defined “particulate genetic inheritance” as a primary mechanism for the heritability of traits, more recent work in past decades in lower eukaryotes and early mammalian species have included “epigenetic” (or “upon the genome”) modifications to the genomic backbone as a primary mechanism in the complex series of molecular interactions which ultimately enabling coordinate regulation of development. In recent years such investigations have evolved to focus on the role of epigenetic modifications to DNA and core histones in higher mammalian developmental processes. What are epigenetic modifications? While almost all cells of an individual bear near identical genomic constitutions, phenotype is ultimately determined by the gene expression profile. Gene expression is maintained by two major mechanisms: (1) transcription factors and post-transcriptional modifiers, and (2) epigenetic modifications, in particular DNA and core-histone modifications, that can be inherited during mitosis from one cell generation to another. This epigenetic code is essential in directing the tremendous number of gene expression changes that must occur for a cell to leave its pluripotent state and become fully differentiated to then function in adaptive homeostasis processes of the organism. It may therefore be stated that ones epigenetic signatures are the net outcome of genotype, developmental lineage, and environmental exposures. These epigenetic signatures are stable and/or heritable patterns of gene activity and expression that do not result from changes in the genomic sequence. Covalent modifications to histones (i.e., histone H3 acetylation and methylation) and DNA methylation (meCpG) are examples of such epigenetic events which collectively...(AU)

Efeitos da suplementação lipídica no aumento da eficiência reprodutiva de fêmeas bovinas / Effects of fat supplementation on reproductive efficiency in bovine females

A energia é o nutriente que mais afeta a reprodução, e seu fornecimento inadequado tem efeitos deletérios sobre a eficiência reprodutiva nas fêmeas bovinas, por mediar alterações metabólicas e endócrinas, que resultam em mudanças na atividade ovariana. Fontes concentradas de energia, como gorduras animal ou vegetal, têm sido utilizadas com diferentes resultados em vacas de leite e de corte, uma vez que os ácidos graxos podem modificar algumas vias específicas e influenciar o metabolismo de alguns hormônios que modulam os processos metabólicos nos ovários. Desta forma, a suplementação de gordura pode ser considerada como uma estratégia para o aumento do desempenho reprodutivo.(AU)

The energy is the nutrient that most affects reproduction, and its inadequate supply has harmful effects on reproductive efficiency in bovine females, by mediating metabolic and endocrine alterations, which result in changes in ovarian activity. Sources of concentrated energy, as animal fats or plant oils, have been used with different results in reproduction and production of dairy and beef cows. The use of fats in diets of cows can improve the reproductive performance because fatty acids can modify some specific pathways and influence the metabolism of some hormones that modulate the metabolic processes in the ovaries. By this mean, fat supplementation for cows can be considered as strategic for improving reproductive performance.(AU)

Efeitos da suplementação lipídica no aumento da eficiência reprodutiva de fêmeas bovinas / Effects of fat supplementation on reproductive efficiency in bovine females

A energia é o nutriente que mais afeta a reprodução, e seu fornecimento inadequado tem efeitos deletérios sobre a eficiência reprodutiva nas fêmeas bovinas, por mediar alterações metabólicas e endócrinas, que resultam em mudanças na atividade ovariana. Fontes concentradas de energia, como gorduras animal ou vegetal, têm sido utilizadas com diferentes resultados em vacas de leite e de corte, uma vez que os ácidos graxos podem modificar algumas vias específicas e influenciar o metabolismo de alguns hormônios que modulam os processos metabólicos nos ovários. Desta forma, a suplementação de gordura pode ser considerada como uma estratégia para o aumento do desempenho reprodutivo.

The energy is the nutrient that most affects reproduction, and its inadequate supply has harmful effects on reproductive efficiency in bovine females, by mediating metabolic and endocrine alterations, which result in changes in ovarian activity. Sources of concentrated energy, as animal fats or plant oils, have been used with different results in reproduction and production of dairy and beef cows. The use of fats in diets of cows can improve the reproductive performance because fatty acids can modify some specific pathways and influence the metabolism of some hormones that modulate the metabolic processes in the ovaries. By this mean, fat supplementation for cows can be considered as strategic for improving reproductive performance.

Progesterone production and metabolism and its role before, during and after artificial insemination influencing the fertility of high producing dairy cows / Produção e metabolismo da progesterona e seu papel antes, durante e depois da inseminação artificial influenciando a fertilidade de vacas leiteiras de alta produção

Background: Efficient reproduction performance is important for optimal profitability on dairy operations. Unfortunately, most dairy farms do not attain optimal reproduction due to many factors including management, health, and physiology of high-producing dairy cows. The physiology limitations involved in reproduction of lactating dairy cows are complex and becoming worse as milk production increases. But many variables related to the interactions between nutrition, the complexity of some hormonal systems, and altered reproductive patterns in dairy cattle have been elucidated. This review will focus on the role of progesterone (P4) in reproduction of the lactating dairy cow. Review: Progesterone is a steroid hormone primarily secreted by the corpus luteum (CL) and placenta. Adequate circulating P4 concentrations are essential for establishment and maintenance of pregnancy. Thus, because of the central role of progesterone on fertility, this manuscript reviews the effect of progesterone (P4) during timed AI protocols in lactating dairy cows. Two sections summarize how P4 is produced and a model attempts to explain how P4 is metabolized in high producing dairy cows. Circulating P4 is determined by a balance between P4 production and P4 metabolism and stimulatory and inhibitory pathways regulating this balance are complex. However in dairy cattle, the volume of luteal tissue is a

A concentração circulante de P4 no organismo é determinada pela razão entre sua produção pelo CL, e, por outro lado, pelo seu metabolismo nas células hepáticas. Nas vacas leiteiras de alta produção existe um desbalanço nesta equação, pois a P4 produzida é rapidamente metabolizada por uma taxa extremamente alta de fluxo sanguíneo que passa através do fígado. Diferentes abordagens para manipular a concentração circulante de P4, e em momentos diferentes em relação a IA, têm sido realizadas no intuito de compreender e, então, de compensar este desbalanço na P4 circulante causado pelos altos níveis de produção de leite. [...]

Análise da interação vitamina A e o ambiente em reprodutores suínos / Assessment of interaction between vitamin A and environment on boars

Os objetivos do estudo foram: (a) avaliar a influência da suplementação de vitamina A na dieta de cachaços nos parâmetros seminais: volume, motilidade, vigor espermático, pH, concentração espermática, número total de espermatozóides, percentual de espermatozóides vivos e anormalidades morfológicas ao longo do ano; (b) averiguar a variabilidade das características, em animais suplementados com vitamina A na dieta, frente às variações da temperatura nas estações do ano. A pesquisa foi desenvolvida no Laboratório de Pesquisa em Suínos, da FMVZ-USP, utilizando-se 10 machos de linhagem híbrida e distribuídos em dois tratamentos, controle (nível de 25.000 UI de vitamina A/animal/dia) e suplementado com a vitamina A (nível de 40.000 UI de vitamina A/animal/dia). O delineamento foi inteiramente casualizado, com medidas repetidas no tempo, sendo os dados analisados utilizando o programa estatístico Statistical Analysis System (SAS). As probabilidades de interações com o tempo foram determinadas pelo teste de Greenhouse-Geisser Epsilon, considerando o nível de significância de 5%. Em relação aos efeitos da vitamina A durante o período de 1 ano, verificou-se que não houve diferença entre os tratamentos para os parâmetros seminais, não encontrando-se efeito de interação tempo e tratamento. Detectou-se efeito de tempo para os parâmetros pH, concentração espermática, número total de espermatozóides, percentual de espermatozóides vivos e anormalidades morfológicas. Já na averiguação da variabilidade também não foi constatado efeito de tratamento, porém houve efeito de estação do ano para todos os parâmetros e de temperatura para o percentual de espermatozóides vivos, pH e anormalidades morfológicas, não sendo verificado efeito para os demais parâmetros. Inferiuse com o estudo que, dada à condição metabólica diferencial dos animais híbridas, novas averiguações devem ser perseguidas para a relação nutrição e reprodução, uma vez que, os efeitos positivos da suplementação da vitamina A na espermatogênese foram evidenciados, principalmente nas características que mais se relacionam com a formação da célula espermática, as anormalidades morfológicas, percentual de espermatozóides vivos e número total de espermatozóides no ejaculado

The objectives of the study were: (a) to evaluate the effect of vitamin A supplementation on boars? diet considering the parameters: volume, motility, spermatic vigor, seminal pH, spermatic concentration, total number of spermatozoa, percentage of living sperm cells and morphologic abnormalities during one year; (b) to investigate the variability founded against the temperature and seasons of the year on vitamin A supplemented animals seminal parameters. The research was developed in the Laboratory of Research in Swines, the FMVZUSP, using 10 boars of hybrid lineages. Two treatments were used having the control (level of 25.000 UI of vitamin A/animal/day) and vitamin A supplemented group (level of 40.000 UI of vitamin A/animal/day). The statistical design was random, with repeated measured in time. The analyzed data used was the statistical program Statistical Analysis System (SAS). The probabilities of the interactions in time were determined by Greenhouse-Geisser Epsilon test, considering the significant level 5%. None of the evaluated parameters was significantly different and no detected interaction in time was found treatment. In relation to the effects of the vitamin A on supplementation in one year period it wasn?t have differences among treatments on seminal parameters, and also there wasn?t interaction in time and at treatment, however for pH, spermatic concentration, total number of spermatozoa, percentage of living sperm cells and morphologic abnormalities it was detected effect on time. In relation to the variability there wasn?t treatment effect, however there was for all the parameters studied effect of the season. The effect of temperature was only for the percentage of living sperm cells, pH and morphologic abnormalities. It was concluded that at a given metabolic condition of the hybrid animals, new ascertainments must be inquired for the relation nutrition and reproduction, a time that, the positive effect of the suplementation of the vitamin in spermatogenesis had been evidenced, mainly in the characteristics that more become related with the formation of the espermática cell