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This review elucidates the physiological and endocrinological processes intrinsic to puberty and ovulation induction protocols in Bos indicus and Bos taurus beef heifers. Puberty is a complex physiological event involving gonadotropic and metabolic changes that lead to sexual maturity, first ovulation, and regular reproductive cycles, enabling females to reproduce. Exposure to progesterone-based hormonal protocols, with or without additional hormones, can reduce the age at first ovulation and improve sexual maturity through stimuli in the hypothalamus-pituitary-gonadal (HPG) axis and uterine development. However, inducing puberty differs from inducing ovulation, as it does not ensure the heifer will continue cycling or be ready to establish and maintain pregnancy after hormonal exposure. Regardless of the pharmacological basis, studies consistently report that beef heifers that had a corpus luteum (CL) prior to the timed-artificial insemination (TAI) protocol, have greater expression of estrus in response to synchronization and greater pregnancy per AI compared to heifers without a CL. The combination of P4 and E2 significantly impacts uterine development, increasing reproductive efficiency. Exposure to P4 causes a positive effect on inducing ovulation. However, studies indicate that the addition of E2 esters at the time of P4 device removal increases the ovulation rate. In general, the studies showed that fertility varied according to the type of the ovulation induction protocol used, but with inconsistent results. Although ovulation induction protocols are strategic tools to accelerate sexual maturity, a holistic view of the entire system is extremely important, combining integration with genetics and nutrition to enhance the reproductive outcomes of beef heifers. Future research is needed to understand and refine these protocols, driving the efficiency of beef cattle production systems.(AU)

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A inseminação artificial em tempo fixo (IATF) é uma estratégia revolucionária, capaz de otimizar os índices reprodutivos e a logística de fazendas leiteiras, impactando diretamente na rentabilidade do sistema produtivo. A IATF possibilita a intensificação do manejo reprodutivo, por garantir que um maior número de vacas receba a primeira inseminação pós-parto logo após o período de espera voluntário, sem a necessidade da detecção de estro. De modo semelhante, essa estratégia também permite intensificar as re-inseminações de vacas que não ficaram gestantes após o último serviço, garantindo um menor intervalo entre inseminações. Desta forma, a IATF impacta positivamente na taxa de serviço do rebanho, aumentando as chances de emprenhar as vacas mais cedo durante a lactação, o que está diretamente associado à eficiência reprodutiva e rentabilidade da fazenda. Além disso, programas otimizados de IATF garantem maior prenhez/IA, ou seja, maior fertilidade se comparados a estratégias de inseminação em estro. Isso se deve à capacidade do protocolo de IATF ajustado de otimizar a sincronização das fêmeas, garantindo um ambiente endócrino adequado durante o desenvolvimento e ovulação do folículo, resultando em maior fertilidade. Em suma, por aumentar a taxa de serviço e a fertilidade, programas ajustados de IATF proporcionam maior taxa de prenhez a cada 21 dias, principal indicador de eficiência reprodutiva do rebanho. Portanto, implementação sistemática de programas reprodutivos ajustados, baseados na utilização da IATF, é imprescindível para o sucesso das fazendas leiteiras.

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Selection of a single dominant follicle from a cohort of growing follicles is a unique biological process, a key step in female reproductive function in monovular species, and lies at the core of reproductive technologies in cattle. Follicle growth and the number of follicles that ovulate are regulated by precise endocrine, paracrine, and autocrine mechanisms. Most of our current understanding about follicle selection focuses on the role of FSH, LH, and the IGF family in follicle growth and selection of the dominant follicle. However, more recently the role of members of the TGF-ß family has been highlighted, particularly in high fecundity genotypes in sheep. Intercellular signaling between the oocyte and granulosa cells (GC) regulates proliferation and differentiation due to actions of bone morphogenetic protein 15 (BMP15) and growth and differentiation factor 9 (GDF9) within the follicle. Mutations that either knockout or reduce the activity of BMP15 or GDF9 have been found to increase ovulation rate in heterozygotes and generally cause severe follicle abnormalities in homozygotes. A mutation in the intracellular kinase domain of the BMPR1B receptor (Booroola fecundity gene) increases ovulation rate in heterozygotes with further increases in ovulation in homozygotes. The physiological mechanisms linking these mutations to increased ovulation rates are still not well defined. A recently identified high fecundity bovine genotype, Trio, causes increased expression of SMAD6, an intracellular inhibitor of the BMP15/GDF9 signalling pathways. This bovine model has provided insights into the mechanisms associated with selection of multiple dominant follicles and multiple ovulations in carriers of fecundity alleles. The present review focuses on the mechanisms involved in follicle selection in ruminants with a special emphasis on the contribution made by multiple ovulation models in both cattle and sheep. The evaluation of multiple ovulation models in ruminants has allowed us to construct a new physiological model that relates changes in the BMP15/GDF9 signalling pathways to the physiological changes that result in selection of multiple dominant follicles. This model is characterized by acquisition of dominance at a smaller follicle size but at a similar time in the follicular wave with multiple follicles acquiring dominance in a hierarchal sequence, delaying FSH suppression and, thus allowing additional follicles to continue to grow and acquire dominance.

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As our understanding of ovarian function in cattle has improved, our ability to control it has also increased. Luteal function in cattle has been studied in detail, and prostaglandin F2α has been used for several years for the elective induction of luteal regression. More recently, follicle wave dynamics has been studied and protocols designed to induce follicular wave emergence and ovulation have reduced, and even eliminated, the need for estrus detection. The addition of progestin-releasing devices, estradiol, GnRH and equine chorionic gonadotropin (eCG) have provided opportunities for fixed-time AI (FTAI) and possibilities for increased pregnancy rates. In embryo transfer programs, these same treatments have eliminated the need for estrus detection, permitting fixed-time embryo transfer and the initiation of superstimulatory treatments without regard to day of the estrous cycle. Collectively, new treatment protocols have facilitated the application of assisted reproductive technologies, and this is especially true in South America. Over the last 20 years, the use of AI in South America has increased, due largely to the use of FTAI. There has been more than a 10-fold increase in the use of FTAI in Brazil with more than 11 million treatments in 2016, representing 85% of all AI. Similar trends are occurring in Argentina and Uruguay. Production of in vivo-derived (IVD) embryos has remained relatively stable over the years, but in vitro embryo production (IVP) has increased dramatically over the past 10 to 15 years, especially in Brazil where more than 300,000 IVP embryos were produced in 2010. World-wide, more than 666,000 bovine IVP embryos were produced in 2016, of which more than 57% were produced in South America. The use of assisted reproductive technologies has facilitated the dissemination of improved genetics and increased reproductive performance; other South American countries are now following suit.

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Maintenance of the corpus luteum (CL) during pregnancy is essential for continuing the elevated circulating progesterone (P4) that is required to maintain pregnancy. The mechanisms that protect the CL during early pregnancy when the non-pregnant animal would typically undergo CL regression have been extensively investigated. It is clear uterine prostaglandin F2α (PGF) causes regression of the CL in non-pregnant ruminants and that maintenance of the CL during early pregnancy is dependent upon secretion of interferon-tau (IFNT) from the elongating embryo. A number of specific mechanisms appear to be activated by IFNT. Most studies indicate that there is an inhibition of oxytocin-induced secretion of uterine PGF. There is also evidence for increased resistance to PGF action, perhaps due to secretion of PGE2 and PGE1 or direct endocrine actions of circulating IFNT. These mechanisms occur concurrently and each may help to maintain the CL during the first month of pregnancy. However, during the second month of pregnancy, IFNT is no longer secreted by the embryo. Attachment of the embryo to the uterus and subsequent placentome development have been linked to silencing of expression from the IFNT gene. In addition, there is some evidence that oxytocin responsiveness of the uterus returns during the second month of pregnancy leading to substantial basal secretion of PGF and perhaps PGF pulses. There is also no evidence that the CL during the second month of pregnancy is resistant to the actions of PGF as observed during the first month. Thus, this manuscript attempts to compare the mechanisms that maintain the CL during the first and second months of pregnancy in ruminants and provides a new, speculative, physiological model for maintenance of the CL during month two of pregnancy that is distinct from the previously-described mechanisms that maintain the CL during the first month of pregnancy.

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Nutrition is one of the main factors affecting reproductive efficiency by influencing the growth, maturation and ovulatory capacity of the follicle and metabolic status of the animal, leading to scenarios that impair or corroborate the development and establishment of pregnancy. Different levels of dry matter intake (DMI, providing gain, loss or maintenance of body weight, for example) greatly affect the physiology of the estrous cycle and reproductive performance. The DMI level is also correlated with hepatic blood flow, resulting in a greater or lower metabolization of steroid hormones, which explains part of the reproductive problems that affects high-producing dairy cows. Insulin is one of the main factors that mediate the relationship between nutrition and reproduction. Thus, this review aims to clarify the key points of the relationship between nutrition and reproduction in relation to DMI and insulin action.

A nutrição é um dos principais fatores que afetam a eficiência reprodutiva por influenciar o crescimento, maturação e capacidade ovulatória do folículo bem como o perfil e estado metabólico do animal, gerando cenários que prejudicam ou corroboram o desenvolvimento e estabelecimento da prenhez. Diferentes níveis de ingestão de matéria seca (IMS; proporcionando ganho, perda ou manutenção de peso corporal, por exemplo) afetam consideravelmente a fisio-logia do ciclo estral e o desempenho reprodutivo. O nível de IMS também está correlacionado com o fluxo sanguíneo hepático, determinando maior ou menor metabolização de hormônios esteroides, fato que explica parte dos problemas reprodutivos apresentados por vacas leiteiras de alta produção. A insulina é um dos principais fatores que medeiam a relação da nutrição com a reprodução. Assim, essa revisão tem como objetivo esclarecer os pontos-chave da relação entre a nutrição e reprodução no que diz respeito aos níveis de ingestão de alimento e a ação da insulina.

Resumo

In dairy herds, since the 70s, it has been observed that with the increase in milk production has also been associated with increased number of services per conception. This decreased fertility of dairy cows is associated with several factors such as the greater metabolism of steroid hormones, consequently inadequate circulating hormones to promote optimal endocrine environment for follicle growth and conceptus development. Furthermore, the increase in milk production is associated with an increased incidence of diseases related to dairy herds, increased susceptibility to heat stress and higher incidence of anovulation. Accordingly, hormone treatments may be used in order to increase the fertility of dairy herds. Thus, this article discusses particular aspects of the reproductive physiology of dairy cows, as well as factors affecting the reproductive efficiency of dairy herds.

Em rebanhos leiteiros, desde a década de 70, tem se observado que o aumento gradativo da produção de leite vem acompanhado do aumento do número de serviços por concepção. Essa queda da fertilidade está associada a diversos fatores como maior velocidade da metabolização de hormônios esteroides e, consequentemente, concentrações hormonais inadequadas para promover um ambiente endócrino ideal para o crescimento folicular e uterino para o desenvolvimento do concepto. Além disso, o aumento de produção de leite está associado a maiores incidências de doenças e condição anovulatória, bem como à maior susceptibilidade das vacas ao estresse calórico. Com isso, tratamentos hormonais podem ser utilizados visando aumentar a fertilidade de rebanhos leiteiros. Desta forma, o presente artigo discorre sobre aspectos envolvendo à fisiologia reprodutiva e dos fatores que afetam a eficiência reprodutiva de vacas leiteiras.

Resumo

Este trabalho teve o objetivo de avaliar, em búfalas Murrah, a interferência da manipulação diária dos animais para exame ginecológico em parâmetros reprodutivos e produtivos. Vinte e quatro búfalas, paridas no outono, ordenhadas uma vez ao dia, mantidas a pasto foram distribuídas nos grupos: Pesquisa (GP; n=13); e Controle (GC; n=11). As fêmeas do GP, após a ordenha, foram diariamente, desde o 7º dia pós-parto até o primeiro estro e cobertura, conduzidas até o curral e submetidas a exame ginecológico e coleta de sangue. Os animais do GC, após a ordenha, foram liberados diretamente para o pasto sem nenhuma manipulação. O GP apresentou intervalo parto-primeiro estro menor (40,4±9,0 dias) que o GC (59,2±24,4 dias; P0,05), bem como na produção de leite. O número de coberturas por concepção foi maior no GP (2,1±0,9) do que no GC (1,5±0,5; P<0,05). Conclui-se que a manipulação diária dos animais para pesquisa empregada neste experimento afeta alguns parâmetros reprodutivos, comprometendo o número de coberturas por concepção, mas não interfere no intervalo parto-concepção, na taxa de prenhez ao final da estação e na produção leiteira, considerando-se o sistema de manejo e os índices de produção do experimento.

This study aimed to evaluate the interference of daily gynecological exam on reproductive and productive parameters in Murrah buffaloes. Twenty-four buffaloes, which have calved in the autumn season, were milked once a day and kept on pasture, were divided into two groups: Research (RG; n=13) and Control (CG; n=11). The animals in RG were daily taken to the corral and submitted to gynecological examination and blood collection immediately after milking, from the 7th day postpartum until the first estrus and breeding day. Animals in CG were released directly to pasture after milking without any manipulation. The RG had smaller calving-first estrus interval (40.4±9.0 days) than CG (59.2±24.4 days; P0.05), as well as in milk production. The number of mating per conception was higher in RG (2.1±0.9) than in CG (1.5±0.5; P<0.05). We concluded that the daily management of animals used for research in this experiment affects some reproductive parameters, such as the number of mating per conception, but it does not affect calving-conception interval nor the pregnancy rate at the end of the season, as well as milk production, considering the management system and the production indices of the experiment.

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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.

Resumo

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. [...]

Resumo

Background: Although there is some information in the literature discussing differences of the estrous cycle of Bos taurus and Bos indicus cattle, most of the data derive from studies performed in temperate climate countries, under environmental and nutritional conditions very different than those found in tropical countries. Moreover, the physiological basis for understanding the differences between Bos taurus and Bos indicus estrous cycles are still unknown. This review explores the physiological and metabolic bases for understanding the key differences between the Bos taurus and Bos indicus estrous cycle. Moreover, it presents recent results of studies that have directly compared reproductive variables between Zebu and European cattle. Review: The knowledge of reproductive physiology, especially the differences between Bos taurus and Bos indicus, is important for the development and application of different techniques of reproductive management in cattle. In this regard, overall, Bos indicus have a greater number of small ovarian follicles and ovulatory follicles are smaller as compared to Bos taurus. Consequently, Zebu cattle also have smaller corpus luteum (CL). Nevertheless, circulating concentrations of steroid and metabolic hormones are not necessarily higher in European cattle. In fact, some studies have shown that despite ovulating smaller follicles and having smaller CL, Bos indicus cows or heifers have higher circulating concentrations of estradiol, progesterone, insulin and IGF-I compared to Bos taurus females. In addition, there are also substantial differences between Bos indicus and Bos taurus cattle in relation to follicle size at the time of selection of the dominant follicle. Conclusion: Data from very recent studies performed in Brazil have corroborated results from previous reports that have observed substantial differences in the estrous cycle variables of Bos indicus versus Bos taurus cattle. Those differences are probably related to distinct metabolism and metabolic hormone concentrations between Zebu and European cattle. This increased knowledge will allow for the establishment of more adequate reproductive management protocols in both breeds of cattle.

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Este estudo teve por objetivo comparar o uso de um análogo da PGF2alfa à associação de progestágeno (MAP) com gonadotrofina coriônica equina (eCG) na sincronização do estro em ovelhas da raça Santa Inês. Foram utilizadas 38 fêmeas ovinas submetidas a dois protocolos de sincronização de estro, com os seguintes protocolos: PGF2alfa (duas doses de 0,53 mg de D-cloprostenol com nove dias de intervalo) e protocolo MAP+eCG (pessário intravaginal com 50 mg de acetato de medroxiprogesterona por doze dias e no momento da remoção do dispositivo aplicação de 250 UI de eCG, IM). Submeteram-se as ovelhas aos diferentes protocolos, com intervalo de dois ciclos estrais. Procedeu-se a uma ultrassonografia transretal no último dia do protocolo, para avaliação do diâmetro do maior e do segundo maior folículo, e à coleta de sangue no dia sete do ciclo estral, para avaliação da concentração sérica de P4. Exame laparoscópico foi realizado no dia 11, após o fim dos protocolos, para contagem de corpos lúteos. Para os parâmetros taxa de sincronização, diâmetro do maior e do segundo maior folículo, período do final do protocolo ao estro e taxa de ovulação, não se observaram diferenças entre os mesmos. Foi observado que o protocolo MAP+eCG produziu concentrações séricas de P4 maiores do que o protocolo PGF2alfa (3,9 e 2,8 ng/ mL, respectivamente, P<0,05). Nas condições do presente estudo, embora o protocolo MAP+eCG tenha apresentado superioridade em relação à concentração sérica de P4, o protocolo PGF2alfa foi tão eficiente quanto aquele em sincronizar o estro.

The aim of this study was to compare two protocols of estrus synchronization in Santa Inês ewes. Thirty-eight ewes were randomly divided into two groups of estrus synchronization: protocol PGF2alpha (two doses of 0.530 mg of PGF2alpha, nine days apart) and protocol MAP+eCG (intravaginal sponge impregnated with medroxyprogesterone acetate, for 12 days, and then an injection of 250 IU of eCG). The experiment was in a cross-over design, two estrous cycles apart. On the final day of protocol, a transrectal ultrasound examination was carried out to measure the size of the largest and second largest ovarian follicles and on day 7 of estrous cycle blood was collected to measure serum P4 concentration. Laparoscopy was carried out on day 11 after the end of protocols to count corpora lutea. Synchronization rate, size of largest and second largest ovarian follicles, interval between the end of the protocol to estrus and ovulation rate did not differ between protocols. Ewes synchronized with MAP+eCG had greater serum P4 concentrations than ewes synchronized with PGF2alpha (3.9 and 2.8 ng/mL, respectively, P<0.05). Based on the results, it may be concluded that, although the protocol MAP+eCG was superior in inducing higher serum concentration of P4, the protocol PGF2alpha was equivalent regarding estrus synchronization.

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O experimento teve como objetivo avaliar e comparar dois eletroejaculadores (EEr): um automático (A – Biocom Ltda., Uberaba, MG) e outro manual (M – Duboi, Campo Grande, MS), utilizando dois métodos de contenção: estação (E) e decúbito lateral (D). Foram utilizados doze carneiros: Santa-Inês (n=9), Ile-de-France (n=2) e Texel (n=1). O sêmen foi coletado duas vezes por semana e as coletas realizadas três vezes em cada grupo (AD – automático em decúbito; AE – automático em estação; MD – manual em decúbito e ME – manual em estação) resultando em doze coletas. Antes e depois das coletas de sêmen, amostras de sangue foram coletadas para análise dos níveis plasmáticos de cortisol com objetivo de verificação do estresse entre os grupos e indivíduos. Procedeu-se à avaliação das coletas pelo tempo em segundos para obtenção da fração seminal, tempo de duração da fração seminal e porcentagem de carneiros que expuseram o pênis. Os parâmetros avaliados referentes ao sêmen foram: volume, aspecto, motilidade espermática progressiva, turbilhonamento, vigor espermático, número total de espermatozoides no ejaculado e morfologia espermática. Em 7,1% de todas as coletas não houve ejaculação, sendo que o grupo submetido ao tratamento AD (20%) foi responsável pela maior fração das coletas sem ejaculação (P0,05). No entanto, houve diferença entre indivíduos (P<0,05). As coletas de sêmen nos animais em decúbito demandaram menor tempo para atingir a fração seminal e também proporcionaram maior duração da fração seminal (P<0,05). O grupo MD obteve menor tempo em atingir a fração seminal e produziu um maior volume de sêmen quando comparado ao grupo AE (P<0,05). Os dados do experimento permitem concluir que o EEr automático e manual apresentaram resultados semelhantes, assim como as posições de coleta, decúbito ou estação.

The objective of the experiment was to evaluate and compare two electroejaculators: an automatic one (A – Biocom Ltda., Uberaba, MG) and a manual one (M – Duboi, Campo Grande, MS), using two methods of physical restrain: standing (E) or lateral recumbency (D). Twelve rams were used: Santa Inês (n=9), Ile-de-France (n=2) and Texel (n=1). Semen were collected twice a week and each animal had the semen collected three times in each group (AD – automatic in recumbency, AE – automatic in station, MD – manual in recumbency, and ME – manual in station) resulting in 12 collections. Blood samples were obtained before and after the semen collections to measure changes in circulating cortisol in order to measure stress among groups and individuals. The collections were evaluated per the time in seconds to obtain seminal fraction, time of seminal fraction and percentage of rams that exposed the penis. The collected semen parameters evaluated were: volume, aspect, progressive motility, wave motion, sperm vigor, total number of spermatozoa and sperm morphology. In 7.1% of the collections, there was no ejaculation, moreover, group AD was responsible for most of the collections without ejaculation (20%)(P0.05) relating to cortisol level after collections. However, there was difference among individuals (P<0.05). The collections in lateral recumbency were faster regarding achievement of seminal fraction and provided more time length for seminal fraction. The MD group required a shorter time length to achieve the seminal fraction and produced a greater volume of ejaculate in comparison to the AS group. It can be concluded by these results that both eletroejaculators (automatic and manual) had similar results as well as both methods of physical restrain (standing and lateral recumbency).

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This study investigated the effect of high dry matter intake (Flushing) on the superovulatory response of crossbred Nelore x Simmental cows. Fourteen non-lactating cows, with a mean body condition score (BCS) of 4.0 (scale from 1 to 5) were randomly assigned into two groups (Maintenance=M or Flushing=F). Seven days prior to onset of superovulation (SOV) until the last day of treatment with FSH, group F cows were fed a diet to achieve 180% of maintenance. Group M cows were fed a maintenance diet. Seven days after AI, embryos were collected and evaluated. Forty days later, the treatment groups were inverted and another SOV was realized. Variables were compared by paired t test and data are presented as mean ± SEM. The number of recruited (19.6±1.8 and 16.4±2.0) and ovulated (15.0±1.6 and 13.0±1.6) follicles detected by ultrasonography did not differ between the M and F groups, respectively (P>0.10). However, the total number of embryos/ova (14.1±2.3 and 9.5±1.5) and the number of viable embryos (10.1±2.1 and 6.7±1.5) recovered were greater in group M (P

Objetivou-se avaliar o efeito da alta ingestão de matéria seca (AIMS) sobre a resposta superovulatória de vacas mestiças Nelore x Simental. Quatorze vacas não lactantes, com escore de condição corporal (ECC) igual a 4,0 (escala de 1 a 5), foram divididas aleatoriamente em dois grupos (Manutenção=M ou alta ingestão de matéria seca=AIMS). De sete dias antes do início da superovulação (SOV) até o final das aplicações de FSH, as vacas do grupo AIMS receberam dieta com 180% da manutenção. O grupo M recebeu dieta de manutenção. Sete dias após a IA, os embriões foram colhidos e avaliados. Quarenta dias após, inverteram-se os tratamentos e realizou-se uma nova SOV. Para comparação entre os grupos, utilizou-se o teste t pareado. Os resultados estão apresentados em média ± erro-padrão. O número de folículos recrutados detectados por ultrassonografia (19,6±1,8 e 16,4±2,0) e ovulados (15,0±1,6 e 13,0±1,6) não diferiu entre os grupos M e AIMS, respectivamente (P>0,10). Entretanto, os números de estruturas totais (14,1±2,3 e 9,5±1,5) e embriões viáveis (10,1±2,1 e 6,7±1,5) colhidos foram maiores no grupo M (P