Prohibition of hormones in animal reproduction: what to expect and what to do?

As our understanding of ovarian function in cattle has improved, our ability to control it has also increased. The development of Fixed-Time Artificial Insemination (FTAI) protocols at the end of the 20th century has increased exponentially the number of animals inseminated over the last 20 years. The main reasons for this growth were the possibility of obtaining acceptable pregnancy rates without heat detection and, above all, the induction of cyclicity in suckled cows in postpartum anestrus and prepubertal heifers at the beginning of the breeding season. Most FTAI treatments in South America have been based on the use of progesterone (P4) releasing devices and estradiol to synchronize both follicular wave emergence and ovulation, with pregnancy rates ranging from 40 to 60%. These protocols are implemented on a regular basis, allowing producers access to high-quality genetics, and increasing the overall pregnancy rates during the breeding season. In addition, it provided the professionals involved in these programs with a new source of income and the diversification of their practices into activities other than their usual clinical work. Many of these practices are now apparently at risk from restrictions on the use of estradiol by the European Union (EU) and other countries. However, the development of alternative protocols based on GnRH, with P4 devices and eCG and other new products that are not in the market yet will allow us to adapt to the new times that are coming. Logically, the challenge has already been raised and we must learn to use alternative protocols to try to continue increasing the use of this technology in beef and dairy herds. The objective of the present review is to describe the main aspects of banning estradiol in livestock production, the negative impacts on reproductive efficiency, and to present some alternative FTAI protocols for dairy and beef cattle.(AU)

Effect of GnRH administration on pregnancy-associated glycoproteins in dairy sheep with different reproductive status

Background: Measurement of pregnancy-associated glycoproteins (PAGs) by radioimmunoassay or enzyme-linked immunosorbent assay has been commonly used for early pregnancy diagnosis in ruminants. However, an accurately pregnancy detection depends on test antibody, breed and number of embryos. Only few studies have conducted to detect or predict animals at risk of late embrionic mortality (LEM) and to use hormonal interventions for embryo losses reducing, but this area is still open in sheep. The current study aimed to evaluate the effect of gonadotropin releasing hormone (GnRH) administration on Day 4 after artificial insemination on the pregnancy-associated glycoproteins in dairy sheep with different reproductive status in relation to pregnancy and late embrionic mortality detection. Materials, Methods & Results: Sixty-five East Friesian sheep were divided in 2 groups - I (Control group, n = 35) and II (GnRH group, n = 30) and sublected to estrus synchronization and artificial insemination (AI). Group I was not treated and Group II received 50 µg GnRH on Day 4 after AI. PAGs in blood serum were measured by Alertys Ruminant Pregnancy test on Days 4, 12, 20, 25 and 35 after AI and ultrasound pregnancy test was conducted on Days 20, 25, 35 and 60. Reproductive status (non-pregnant, pregnant and animals with LEM) was determined by ultrasound and the results between different groups were compared. The PAGs mean values according to reproductive status and Day after AI were analysed. Accuracy, sensitivity and specificity of the PAGs test for pregnancy diagnosis on Day 35 were calculated. On Day 20 after AI the pregnat sheep (83.3%) in group I tended to be higher than those (77.1%) in group II with decrease of 25.7% and 20% for the same groups on Day 25. On day 25 LEM was recorded in 33.3% and 24% in group I and II, respectively. The ultrasound exams on Day 60 confirmed the results from Day 25 after AI. A total value of non-pegnant, pregnant animals and LEM was 20%, 56.9% and 28.8%, respectively. The mean values of PAGs in animals with the same reproductive status in group I and II no differed statistically between Days 4 and 35 after AI. On Day 25 the PAGs values in LEM groups (0.126 ± 0.072 and 0.179 ± 0.029) were higher than those (0.062 ± 0.038 and 0.083 ± 0.023) in the non-pregnant groups, but no significan difference was deternined. On Day 35 after AI the mean values of PAGs (0.414 ± 0.125 and 0.421 ± 0.121) for the pregnant groups were significantly (P < 0.05) higher than those (0.078 ± 0.053 and 0.093 ± 0.034) for the non-pregnant groups. The values of PAGs in LEM groups on Day 25 (0.099 ± 0.062 and 0.113 ± 0.058) were decreased and close to the mean values in non-pregnant sheep. A significant effect of the day after AI on the PAGs values was evidenced in pregnant animals only (control r = 0.97 and GnRH r = 0.98; P < 0.05). The PAGs started to rise rapidly between Days 25 and 35 after AI. On Day 35 the accuracy (98%), the sensitivity (97.3%) and the specificity (100%) of the PAG test for pregnancy diagnosis were similar to the values (100%) for ultrasound method. Discussion: The gonadotropin treatment on Day 4 after AI tended to improve the reproductive performance in the sheep, but no significant effect of GnRH on the PAGs values in the animals with different reproductive status was found. The PAGs profiles in non-pregnant and LEM sheep were close and distinguishing between non-pregnant and LEM ewes on Day 35 was impossible. The PAGs values in pregnant sheep showed significantly (P < 0.05) increase between Days 25 and 35 after AI with higher mean values in pregnant than non-pregnant groups on Day 35 (P < 0.05). Alertys Ruminant Pregnancy test was a reliable for pregnancy detection in sheep on Day 35 after artificial insemination.

Seminal plasma nerve growth factor signaling on the reproductive physiology of female llamas

The ovulation mechanism is one of the fascinating physiological processes in reproductive biology in mammals. From the reproductive point of view, the species have been classified as spontaneous or induced ovulators. Although the release of GnRH followed by the preovulatory LH surge is shared between both types of ovulation, the stimulus to initiate GnRH release varies between both categories. In spontaneous ovulators, ovulation depends on the systemic concentration of ovarian steroids, however, in induced ovulators, different stimuli such as copulation, environmental, and social cues can facilitate or induce ovulation regardless of the increases in systemic estradiol concentration. In this review, we document evidence that a male-derived protein is the main factor responsible for inducing ovulation and also modulating the ovarian function in the domestic South American camelid, the llama. The neurotrophin beta-Nerve Growth Factor (β-NGF) is the principal factor present in the semen of llamas responsible for inducing ovulation in this species. After the intrauterine deposit of semen during mating, β-NGF is absorbed through the endometrium to reach the circulatory system, where it reaches the hypothalamus and stimulates GnRH release. The potential site of action of this neurotrophin at the brain has not been elucidated, however, hypotheses are raised that the factor may cross the blood-brain barrier and stimulate upstream neuronal networks that lead to the stimulation of GnRH-secreting neurons. It is possible that β-NGF could be sensed at the median eminence without crossing the blood-brain barrier. Finally, it has been observed that this factor is not only a powerful stimulator of ovulation but also has a luteotrophic effect, resulting in the development of a corpus luteum capable of secreting more progesterone when compared to other ovulation-stimulating analogues.(AU)

Three superovulation protocols for in vivo embryo production in Santa Inês sheep / Três protocolos para produção in vivo de embriões em ovelhas Santa Inês

There is still no consensus regarding the best protocol for in vivo embryo production in sheep despite increasing studies in this area. Moreover, there is variability in the response of ewes to superovulation (SOV). An approach to mitigate this inconsistency is to initiate gonadotropin administration under favorable ovarian conditions. The present study compared three treatments in a crossover design: a traditional SOV protocol (TRAD) and "Day 0" D0 SOV protocol with (D0+GnRH), or without Lecilerin (D0-GnRH). Fifteen Santa Inês ewes received 200 mg of FSH at six decreasing doses and PGF2α with the fifth dose of FSH. They were naturally mated with fertile rams and subjected to surgical embryo collection. The number of viable embryos was similar among the different treatments (TRAD = 6.0 ± 4.7; D0-GnRH = 3.8 ± 6.4; D0+GnRH = 7.5 ± 6.5). Regardless of the treatment method, ewes with follicles ≤ 4 mm, at the first FSH dose, produced more viable embryos (9.6 ± 6.0, P < 0.05) compared to ewes that had follicles > 4 mm at the beginning of the SOV (2.9 ± 3.1, viable embryos). Both the TRAD and D0+GnRH groups had fewer animals with large follicles (> 4 mm) at the first FSH dose than the D0-GnRH group (P < 0.05). In conclusion, both the TRAD and D0+GnRH treatments induced a more favorable ovarian condition (follicles ≤ 4 mm) for adequate SOV; although, all three treatments exhibited similar efficacies in Santa Inês sheep.

Ainda não há consenso sobre qual é o protocolo mais apropriado para a produção in vivo de embriões em ovinos, apesar do crescente conhecimento. Uma abordagem para mitigar a variabilidade de resposta de ovelhas à superovulação (SOV) é iniciar a aplicação de gonadotrofinas em uma condição ovariana favorável. O presente estudo comparou três tratamentos em delineamento do tipo crossover: protocolo de SOV tradicional (TRAD) e "Dia 0" D0 SOV sem (D0-GnRH) ou com GnRH (D0+GnRH). Quinze ovelhas Santa Inês foram superovuladas com 200 mg de FSH em seis doses decrescentes e receberam PGF2α na quinta dose de FSH. As ovelhas foram submetidas a monta natural com carneiros férteis e os embriões colhidos por via cirúrgica. O número de embriões viáveis não diferiu entre os tratamentos (TRAD = 6,0 ± 4,7; D0-GnRH = 3,8 ± 6,4; D0+GnRH = 7,5 ± 6,5). Independentemente do tratamento, ovelhas com folículos ≤ 4 mm na primeira dose de FSH produziram mais embriões viáveis (9,6 ± 6,0; P < 0.05) quando comparadas aos animais que apresentavam folículos > 4 mm no início da SOV (2,9 ± 3,1 embriões viáveis). Os grupos TRAD e D0+GnRH apresentaram menor número de animais com folículos grandes (> 4 mm), no momento da primeira dose de FSH, quando comparados ao grupo D0-GnRH (P < 0,05). Em conclusão, os protocolos TRAD e D0+GnRH induziram uma condição ovariana mais favorável (folículos ≤ 4 mm) para a SOV. No entanto, os três tratamentos apresentaram eficiência semelhante em ovelhas Santa Inês.

Reproductive parameters of lambs immunocastrated with anti-GnRH vaccine

Abstract The objective of this study was to evaluate the testicular biometric, seminal, and plasma testosterone levels in lambs subjected to an anti-GnRH vaccine as a method of castration. Thirty entire, crossbred Santa Inês male lambs were randomly distributed into three treatment (T): T1 was the control group, with the administration of 1 mL of saline solution subcutaneously (SC); 1.0 and 0.5 mL of an anti-GnRH vaccine were administered SC in T2 and T3, respectively. Testicular biometric variables, physical and morphological variables of semen, and plasma testosterone concentrations were evaluated. At D60, there was a reduction in testicular length, width, thickness, and scrotal circumference of the immunocastrated animals regardless of the vaccine dose used (P < 0.05). A reduction in semen physical variables at both dosages (P < 0.05) was observed, with azoospermia, in 80% and 70% of animals in the T2 and T3 groups, respectively. At D60, the immunocastrated animals also showed an increase in spermatozoa defects (P < 0.05), whereas plasma testosterone concentration decreased (P < 0.05). Immunocastration of lambs using the Bopriva vaccine at doses of 1.0 and 0.5 mL is efficient in inducing azoospermia in up to 80% of animals, although two doses in a 30-day interval are necessary for it to be an effective and safe method. Efficacy was demonstrated through a reduction in serum testosterone levels, testicular biometry, and seminal fluid analysis. Considering the efficacy of both doses in this study, we recommend using the lower dose (0.5 mL), which will allow for a 50% reduction in vaccine costs.

The effect of Gonadotropin releasing hormone administration on fertility and embryonic loss in goats during the anoestrus period

Following the induction of oestrus out of season in small ruminants, low fertility and variations in fertility rates are associated with embryonic losses. One of the main causes of embryonic loss is luteal dysfunction. Gonadotropin Releasing Hormone (GnRH) supports the luteal structure, and increasing progesterone levels may be beneficial in terms of promoting embryonic life. The main objective of the present study was to evaluate the efficacy of GnRH administration following an oestrus induction protocol in the anoestrus season for preventing embryonic loss in goats having failure to conceive during the season. In the study, 106 Damascus goats aged 3-5 years and weighing 45-60 kg were used. The oestrus of 106 goats in the anoestrous group was stimulated with progesterone and pregnant mare serum gonadotropin (PMSG) treatment. Out of breeding season, goats were divided into the 4 following groups: GnRH0 (n = 27), GnRH7 (n = 26), GnRH0+7 (n = 27) and control (n = 26). In each goat, an intravaginal sponge (IS) containing 20 mg of fluorogestone acetate (FGA) was placed into the vagina and left for 9 days. With the withdrawal of the sponge, 550IU PMSG and 125 µg of d-cloprostenol were injected intramuscularly. Oestrus detection was made via teaser bucks for 3 days starting 24 h after withdrawal of the IS. Eighteen bucks known to be fertile were used for breeding. Goats in the oestrus period were mated via natural breeding. The GnRH analogue lecirelin was injected intramuscularly at breeding in the GnRH0 group, on day 7 post-breeding in the GnRH7 group, and both at breeding and on day 7 post-breeding in the GnRH0+7 group. No injections were given to the control group. Blood samples for progesterone measurement were taken by jugular vena puncturing on days 3, 6, 7, 10, 13, 16, and 19 after breeding from 10 randomly chosen goats in all groups. The goats with a level of > 3.5 ng/mL of progesterone on day 21 post-breeding were evaluated as pregnant. Pregnancy was also viewed on day 50 after breeding by real-time ultrasonography (USG) with a 5-7.5 MHz convex probe. The oestrus rate was 96.23% (102/106) in the goats. The rates of onset of oestrus between 36-48 h, 48-60 h and 60 h and beyond were 38.7% (41/106), 21.7% (23/106) and 35.8% (38/106), respectively. The total pregnancy rate was 35.8% (38/106). There were no statistically significant differences (P > 0.05) found for the pregnancy rate, embryonic death rate or progesterone concentration of the groups. However, serum progesterone levels were statistically different in the GnRH7 group compared with the control group (P < 0.05). After synchronisation, various anti-luteolytic strategies can be used to support corpus luteum development and elevate progesterone concentration in the luteal phase to decrease embryonic loss and increase reproductive performance. Therefore, application of GnRH to support the luteal structure and to increase progesterone levels may be beneficial in terms of supporting embryonic life. The results showed that GnRH treatment on the day 7 post-breeding following oestrus induction, including FGA and PMSG, can increase serum progesterone levels in Damascus goats in the anoestrus period. However, following oestrus induction in the anoestrus period, it was seen that GnRH treatment at breeding or on day 7 after breeding did not have any positive effect on embryonic loss or reproductive performance. In conclusion, it was considered that this protocol could be implemented successfully, yielding a 35% pregnancy rate in Damascus goats in the anoestrus period, but embryonic loss must be deeply studied in detail.(AU)

Reproductive parameters of lambs immunocastrated with anti-GnRH vaccine

The objective of this study was to evaluate the testicular biometric, seminal, and plasma testosterone levels in lambs subjected to an anti-GnRH vaccine as a method of castration. Thirty entire, crossbred Santa Inês male lambs were randomly distributed into three treatment (T): T1 was the control group, with the administration of 1 mL of saline solution subcutaneously (SC); 1.0 and 0.5 mL of an anti-GnRH vaccine were administered SC in T2 and T3, respectively. Testicular biometric variables, physical and morphological variables of semen, and plasma testosterone concentrations were evaluated. At D60, there was a reduction in testicular length, width, thickness, and scrotal circumference of the immunocastrated animals regardless of the vaccine dose used (P < 0.05). A reduction in semen physical variables at both dosages (P < 0.05) was observed, with azoospermia, in 80% and 70% of animals in the T2 and T3 groups, respectively. At D60, the immunocastrated animals also showed an increase in spermatozoa defects (P < 0.05), whereas plasma testosterone concentration decreased (P < 0.05). Immunocastration of lambs using the Bopriva vaccine at doses of 1.0 and 0.5 mL is efficient in inducing azoospermia in up to 80% of animals, although two doses in a 30-day interval are necessary for it to be an effective and safe method. Efficacy was demonstrated through a reduction in serum testosterone levels, testicular biometry, and seminal fluid analysis. Considering the efficacy of both doses in this study, we recommend using the lower dose (0.5 mL), which will allow for a 50% reduction in vaccine costs.(AU)

The neuroendocrine pathways and mechanisms for the control of the reproduction in female pigs

Abstract Within the hypothalamic-pituitary-gonad (HPG) axis, the major hierarchical component is gonadotropin-releasing hormone (GnRH) neurons, which directly or indirectly receive regulatory inputs from a wide array of regulatory signals and pathways, involving numerous circulating hormones, neuropeptides, and neurotransmitters, and which operate as a final output for the brain control of reproduction. In recent years, there has been an increasing interest in neuropeptides that have the potential to stimulate or inhibit GnRH in the hypothalamus of pigs. Among them, Kisspeptin is a key component in the precise regulation of GnRH neuron secretion activity. Besides, other neuropeptides, including neurokinin B (NKB), neuromedin B (NMB), neuromedin S (NMS), α-melanocyte-stimulating hormone (α-MSH), Phoenixin (PNX), show potential for having a stimulating effect on GnRH neurons. On the contrary, RFamide-related peptide-3 (RFRP-3), endogenous opioid peptides (EOP), neuropeptide Y (NPY), and Galanin (GAL) may play an inhibitory role in the regulation of porcine reproductive nerves and may directly or indirectly regulate GnRH neurons. By combining data from suitable model species and pigs, we aim to provide a comprehensive summary of our current understanding of the neuropeptides acting on GnRH neurons, with a particular focus on their central regulatory pathways and underlying molecular basis.

The neuroendocrine pathways and mechanisms for the control of the reproduction in female pigs

Within the hypothalamic-pituitary-gonad (HPG) axis, the major hierarchical component is gonadotropin-releasing hormone (GnRH) neurons, which directly or indirectly receive regulatory inputs from a wide array of regulatory signals and pathways, involving numerous circulating hormones, neuropeptides, and neurotransmitters, and which operate as a final output for the brain control of reproduction. In recent years, there has been an increasing interest in neuropeptides that have the potential to stimulate or inhibit GnRH in the hypothalamus of pigs. Among them, Kisspeptin is a key component in the precise regulation of GnRH neuron secretion activity. Besides, other neuropeptides, including neurokinin B (NKB), neuromedin B (NMB), neuromedin S (NMS), α-melanocyte-stimulating hormone (α-MSH), Phoenixin (PNX), show potential for having a stimulating effect on GnRH neurons. On the contrary, RFamide-related peptide-3 (RFRP-3), endogenous opioid peptides (EOP), neuropeptide Y (NPY), and Galanin (GAL) may play an inhibitory role in the regulation of porcine reproductive nerves and may directly or indirectly regulate GnRH neurons. By combining data from suitable model species and pigs, we aim to provide a comprehensive summary of our current understanding of the neuropeptides acting on GnRH neurons, with a particular focus on their central regulatory pathways and underlying molecular basis.(AU)

Non surgical contraception in cats: what’s new? / Contracepção não-cirúrgica em gatos: o que há de novo?

In the feline species, progestins, GnRH agonist implants and melatonin implants are the three main non-surgical contraceptive approaches that are important to discuss today. When available, those can actually come handy in many clinical situations when surgery cannot be performed or should be avoided. To date though, those only offer short to medium term options. Research using gene therapy is however on its way, with encouraging preliminary results. A long term alternative using this technology might become available in the future, changing how we approach contraception in cats in our veterinary clinics.

Association Analysis Between Polymorphism of Gonadotrophin Releasing Hormone Genes and Growth Traits of Quail (Coturnix Coturnix)

This study investigated SNP mutation sites of Gonadotrophin releasing hormone (GnRH) gene in China yellow quail, Beijing white quail and Korean quail through PCR amplification and DNA sequencing technologies. Moreover, polymorphism of GnRH gene and its association with growth traits of quail were analyzed, aiming to get molecular markers associated to growth traits of quail, which could provide references for breeding of new quail species. According to research results, a total of 14 SNP mutation sites of GnRH were detected in China yellow quail, Beijing white quail and Korean quail, which were C71T, C108T, C168T, C178T, A184G, C206T, A209C, C215T, A252G, A279T, C281T, C293G, C339T and C458T. Except that only 2 genotypes were detected for A209C and C281T in China yellow quail and Beijing white quail, 3 genotypes were detected for all of the remaining 12 SNP mutation sites in three quail species. Of the 14 SNP sites, C71T, A209C, C215T, C281T, C293G, C339T and C458T were significantly associated with body weight (p 0.05), C71T, C108T, C168T, C178T, A184G, C206T, C215T, A252G, C293G, C339T and C458T were significantly associated with shank length (p 0.05), C71T, C215T, C293G and C458T were significantly associated with breastbone length (p 0.05), A209C and C281T were significantly associated with shank circumference (p 0.05).(AU)

Association Analysis Between Polymorphism of Gonadotrophin Releasing Hormone Genes and Growth Traits of Quail (Coturnix Coturnix)

This study investigated SNP mutation sites of Gonadotrophin releasing hormone (GnRH) gene in China yellow quail, Beijing white quail and Korean quail through PCR amplification and DNA sequencing technologies. Moreover, polymorphism of GnRH gene and its association with growth traits of quail were analyzed, aiming to get molecular markers associated to growth traits of quail, which could provide references for breeding of new quail species. According to research results, a total of 14 SNP mutation sites of GnRH were detected in China yellow quail, Beijing white quail and Korean quail, which were C71T, C108T, C168T, C178T, A184G, C206T, A209C, C215T, A252G, A279T, C281T, C293G, C339T and C458T. Except that only 2 genotypes were detected for A209C and C281T in China yellow quail and Beijing white quail, 3 genotypes were detected for all of the remaining 12 SNP mutation sites in three quail species. Of the 14 SNP sites, C71T, A209C, C215T, C281T, C293G, C339T and C458T were significantly associated with body weight (p 0.05), C71T, C108T, C168T, C178T, A184G, C206T, C215T, A252G, C293G, C339T and C458T were significantly associated with shank length (p 0.05), C71T, C215T, C293G and C458T were significantly associated with breastbone length (p 0.05), A209C and C281T were significantly associated with shank circumference (p 0.05).

Understanding the trade-off between the environment and fertility in cows and ewes

The environment contributes to production diseases that in turn badly affect cow performance, fertility and culling. Oestrus intensity is lower in lame cows, and in all cows 26% potential oestrus events are not expressed (to avoid getting pregnant). To understand these trade-offs, we need to know how animals react to their environment and how the environment influences hypothalamus-pituitary-adrenal axis (HPA) interactions with the hypothalamus-pituitary-ovarian axis (HPO). Neurotransmitters control secretion of GnRH into hypophyseal portal blood. GnRH/LH pulse amplitude and frequency drive oestradiol production, culminating in oestrus behaviour and a precisely-timed GnRH/LH surge, all of which are disrupted by poor environments. Responses to peripheral neuronal agents give clues about mechanisms, but do these drugs alter perception of stimuli, or suppress consequent responses? In vitro studies confirm some neuronal interactions between the HPA and HPO; and immuno-histochemistry clarifies the location and sequence of inter-neurone activity within the brain. In both species, exogenous corticoids, ACTH and/or CRH act at the pituitary (reduce LH release by GnRH), and hypothalamus (lower GnRH pulse frequency and delay surge release). This requires inter-neurones as GnRH cells do not have receptors for HPA compounds. There are two (simultaneous, therefore fail-safe?) pathways for CRH suppression of GnRH release via CRH-Receptors: one being the regulation of kisspeptin/dynorphin and other cell types in the hypothalamus, and the other being the direct contact between CRH and GnRH cell terminals in the median eminence. When we domesticate animals, we must provide the best possible environment otherwise animals trade-off with lower production, less intense oestrus behaviour, and impaired fertility. Avoiding life-time peri-parturient problems by managing persistent lactations in cows may be a worthy trade-off on both welfare and economic terms – better than the camouflage use of drugs/hormones/feed additives/intricate technologies? In the long term, getting animals and environment in a more harmonious balance is the ultimate strategy.

Understanding the trade-off between the environment and fertility in cows and ewes

The environment contributes to production diseases that in turn badly affect cow performance, fertility and culling. Oestrus intensity is lower in lame cows, and in all cows 26% potential oestrus events are not expressed (to avoid getting pregnant). To understand these trade-offs, we need to know how animals react to their environment and how the environment influences hypothalamus-pituitary-adrenal axis (HPA) interactions with the hypothalamus-pituitary-ovarian axis (HPO). Neurotransmitters control secretion of GnRH into hypophyseal portal blood. GnRH/LH pulse amplitude and frequency drive oestradiol production, culminating in oestrus behaviour and a precisely-timed GnRH/LH surge, all of which are disrupted by poor environments. Responses to peripheral neuronal agents give clues about mechanisms, but do these drugs alter perception of stimuli, or suppress consequent responses? In vitro studies confirm some neuronal interactions between the HPA and HPO; and immuno-histochemistry clarifies the location and sequence of inter-neurone activity within the brain. In both species, exogenous corticoids, ACTH and/or CRH act at the pituitary (reduce LH release by GnRH), and hypothalamus (lower GnRH pulse frequency and delay surge release). This requires inter-neurones as GnRH cells do not have receptors for HPA compounds. There are two (simultaneous, therefore fail-safe?) pathways for CRH suppression of GnRH release via CRH-Receptors: one being the regulation of kisspeptin/dynorphin and other cell types in the hypothalamus, and the other being the direct contact between CRH and GnRH cell terminals in the median eminence. When we domesticate animals, we must provide the best possible environment otherwise animals trade-off with lower production, less intense oestrus behaviour, and impaired fertility. Avoiding life-time peri-parturient problems by managing persistent lactations in cows may be a worthy trade-off on both welfare and economic terms better than the camouflage use of drugs/hormones/feed additives/intricate technologies? In the long term, getting animals and environment in a more harmonious balance is the ultimate strategy.(AU)

Indução do estro e métodos para controle das fases do ciclo estral em cadelas / Induction of estrus and methods for control of estrous cycle in bitches

Os estudos referentes à manipulação do ciclo estral em cadelas aumentaram significativamente ao longo dos anos. Com a criação comercial de cães ganhando destaque a nível internacional, há uma busca por incrementação no manejo reprodutivo desses animais, bem como o tratamento de condições prejudiciais à fertilidade na cadela, outro motivo é o fato dos cães domésticos também poderem atuar como modelos experimentais para várias espécies de canídeos silvestres e para o homem. Isso tem sido associado a uma maior disponibilidade de fármacos indutores de estro, como agonistas dopaminérgicos, análogos do GnRH e protocolos com gonadotrofinas, a exemplo do eCG. A manipulação eficiente do ciclo estral é de grande valia para o aperfeiçoamento das biotecnologias da reprodução nessa espécie e, mesmo com o avanço das pesquisas, os fármacos ainda não foram suficientemente testados para se obter o conhecimento das suas completas ações, bem como para apontar seus pontos fortes e fracos. Essa revisão de literatura tem como objetivo ampliar as informações a respeito do assunto, abordando aspectos relacionados à fisiologia e endocrinologia reprodutiva na cadela, as particularidades do ciclo estral canino, descrevendo as alterações anatômicas, citológicas e hormonais, bem como os principais moduladores do ciclo estral de cadelas, apontando seus efeitos e controvérsias e proporcionando o surgimento de protocolos eficientes para a indução do estro nesses animais.

Studies on the manipulation of estrous cycle in bitches have increased significantly over the years. With the commercial breeding of dogs gaining prominence internationally, there has been a need for improvement of the reproductive management of these animals, as well as the treatment of conditions which are detrimental to bitches’ fertility. Another reason is that domestic dogs can also act as experimental models to several species of wild dogs and to man. This has been associated with a greater availability of estrus-induction pharmacological drugs, such as dopamine agonists, GnRH analogue and protocols with gonadotropin, such as eCG. Efficient manipulation of the estrous cycles is of great importance for the improvement of the reproductive biotechnology in this species. Notwithstanding the advances in research, the drugs have not yet been sufficiently tested in order to have their action fully understood, nor to identify their strengths and weakness. This literature review aims to expand the information on subject, addressing aspects related to the reproductive physiology and endocrinology in bitches, as well as the main modulators of the estrous cycle, pointing out their effects and differences and providing information for the creation of new efficient protocols for induction of estrus in those animals.

Indução do estro e métodos para controle das fases do ciclo estral em cadelas / Induction of estrus and methods for control of estrous cycle in bitches

Os estudos referentes à manipulação do ciclo estral em cadelas aumentaram significativamente ao longo dos anos. Com a criação comercial de cães ganhando destaque a nível internacional, há uma busca por incrementação no manejo reprodutivo desses animais, bem como o tratamento de condições prejudiciais à fertilidade na cadela, outro motivo é o fato dos cães domésticos também poderem atuar como modelos experimentais para várias espécies de canídeos silvestres e para o homem. Isso tem sido associado a uma maior disponibilidade de fármacos indutores de estro, como agonistas dopaminérgicos, análogos do GnRH e protocolos com gonadotrofinas, a exemplo do eCG. A manipulação eficiente do ciclo estral é de grande valia para o aperfeiçoamento das biotecnologias da reprodução nessa espécie e, mesmo com o avanço das pesquisas, os fármacos ainda não foram suficientemente testados para se obter o conhecimento das suas completas ações, bem como para apontar seus pontos fortes e fracos. Essa revisão de literatura tem como objetivo ampliar as informações a respeito do assunto, abordando aspectos relacionados à fisiologia e endocrinologia reprodutiva na cadela, as particularidades do ciclo estral canino, descrevendo as alterações anatômicas, citológicas e hormonais, bem como os principais moduladores do ciclo estral de cadelas, apontando seus efeitos e controvérsias e proporcionando o surgimento de protocolos eficientes para a indução do estro nesses animais.(AU)

Studies on the manipulation of estrous cycle in bitches have increased significantly over the years. With the commercial breeding of dogs gaining prominence internationally, there has been a need for improvement of the reproductive management of these animals, as well as the treatment of conditions which are detrimental to bitches fertility. Another reason is that domestic dogs can also act as experimental models to several species of wild dogs and to man. This has been associated with a greater availability of estrus-induction pharmacological drugs, such as dopamine agonists, GnRH analogue and protocols with gonadotropin, such as eCG. Efficient manipulation of the estrous cycles is of great importance for the improvement of the reproductive biotechnology in this species. Notwithstanding the advances in research, the drugs have not yet been sufficiently tested in order to have their action fully understood, nor to identify their strengths and weakness. This literature review aims to expand the information on subject, addressing aspects related to the reproductive physiology and endocrinology in bitches, as well as the main modulators of the estrous cycle, pointing out their effects and differences and providing information for the creation of new efficient protocols for induction of estrus in those animals.(AU)

Indução do estro em cutias (Dasyprocta leporina) utilizando-se protocolos à base de prostaglandina isolada ou em associação com análogo de GnRH / Estrus induction in agoutis (Dasyprocta leporina) using protocols based on prostaglandin isolated or in association to GnRH analogue

Comparou-se a eficiência de protocolos para indução de estro em cutias. Em cinco fêmeas, foram administradas duas doses de cloprostenol (5µg) com intervalo de nove dias, via intraperitoneal; em outras cinco, administraram-se 30µg de análogo do hormônio liberador de gonadotrofinas (GnRH), via intravulvar, seguidos de 5µg de cloprostenol, via intraperitoneal, após sete dias e, após mais dois dias, nova dose do análogo de GnRH. A cada três dias, a ciclicidade reprodutiva dos animais foi monitorada, por meio de coleta de sangue, para dosagem hormonal, ultrassonografia ovariana e citologia vaginal. Duas das fêmeas que receberam apenas prostaglandina, as quais estavam em fase luteal no início do tratamento, manifestaram o estro aos três e seis dias após a segunda administração da droga. Já nas fêmeas que receberam a prostaglandina associada ao análogo do GnRH, duas que originalmente estavam em fase luteal apresentaram estro aos quatro dias após o tratamento, e uma outra apenas após 10 dias. Não foram evidenciadas diferenças estatísticas quanto à eficiência dos tratamentos (P>0,05). Conclui-se que, de acordo com os protocolos utilizados, o uso da prostaglandina isolada ou em associação com análogo do GnRH para a indução do estro em cutias D. leporina apresenta eficiência limitada às fêmeas que estejam em fase luteal por ocasião do início do tratamento.(AU)

We compared the efficiency of protocols for estrus induction in agoutis. Five females received double intraperitoneal administration of cloprostenol (5µg) on a 2-days interval; other five females were treated with intravulvar administration of 30µg gonadotrophin release hormone analogue (GnRH associated to intraperitoneal administration of 5µg cloprostenol after seven days and a new administration of GnRH analogue after two days. Every 3 days, the agoutis' reproductive cycle was monitored by blood collection for hormonal analysis, ovarian ultrasound and vaginal cytology. Two females, originally in luteal phase, that received isolated prostaglandin presented estrous signs at 3 and 6 days after the second drug administration. From the females that received the association, two that were originally in luteal phase presented estrus at 4 days after treatment, and one other presented estrus only after 10 days. There was no significant statistical difference regarding the efficiency of treatments for estrus induction (P>0.05). We conclude that, according to the protocols tested in the study, the use of isolated prostaglandin or its association to GnRH analogue for estrus induction in D. leporine shows an efficiency limited to the females that were in luteal phase in the beginning of the treatment.(AU)

Indução do estro em cutias (Dasyprocta leporina) utilizando-se protocolos à base de prostaglandina isolada ou em associação com análogo de GnRH / Estrus induction in agoutis (Dasyprocta leporina) using protocols based on prostaglandin isolated or in association to GnRH analogue

Comparou-se a eficiência de protocolos para indução de estro em cutias. Em cinco fêmeas, foram administradas duas doses de cloprostenol (5µg) com intervalo de nove dias, via intraperitoneal; em outras cinco, administraram-se 30µg de análogo do hormônio liberador de gonadotrofinas (GnRH), via intravulvar, seguidos de 5µg de cloprostenol, via intraperitoneal, após sete dias e, após mais dois dias, nova dose do análogo de GnRH. A cada três dias, a ciclicidade reprodutiva dos animais foi monitorada, por meio de coleta de sangue, para dosagem hormonal, ultrassonografia ovariana e citologia vaginal. Duas das fêmeas que receberam apenas prostaglandina, as quais estavam em fase luteal no início do tratamento, manifestaram o estro aos três e seis dias após a segunda administração da droga. Já nas fêmeas que receberam a prostaglandina associada ao análogo do GnRH, duas que originalmente estavam em fase luteal apresentaram estro aos quatro dias após o tratamento, e uma outra apenas após 10 dias. Não foram evidenciadas diferenças estatísticas quanto à eficiência dos tratamentos (P>0,05). Conclui-se que, de acordo com os protocolos utilizados, o uso da prostaglandina isolada ou em associação com análogo do GnRH para a indução do estro em cutias D. leporina apresenta eficiência limitada às fêmeas que estejam em fase luteal por ocasião do início do tratamento.(AU)

We compared the efficiency of protocols for estrus induction in agoutis. Five females received double intraperitoneal administration of cloprostenol (5µg) on a 2-days interval; other five females were treated with intravulvar administration of 30µg gonadotrophin release hormone analogue (GnRH associated to intraperitoneal administration of 5µg cloprostenol after seven days and a new administration of GnRH analogue after two days. Every 3 days, the agoutis' reproductive cycle was monitored by blood collection for hormonal analysis, ovarian ultrasound and vaginal cytology. Two females, originally in luteal phase, that received isolated prostaglandin presented estrous signs at 3 and 6 days after the second drug administration. From the females that received the association, two that were originally in luteal phase presented estrus at 4 days after treatment, and one other presented estrus only after 10 days. There was no significant statistical difference regarding the efficiency of treatments for estrus induction (P>0.05). We conclude that, according to the protocols tested in the study, the use of isolated prostaglandin or its association to GnRH analogue for estrus induction in D. leporine shows an efficiency limited to the females that were in luteal phase in the beginning of the treatment.(AU)

The effects of separate and combined use of PGF2α and GnRH hormones and the addition of beta-carotene on fertility parameters in dairy cows with ovarian cysts

Background: Ovarian cysts are commonly observed pathologies, which interfere with normal cyclic activity and adversely affect fertility in cows. Beta-carotene is effective in the reduction of reproductive problems by inducing the natural defence mechanisms of the body. There are several methods that can be used for the treatment of ovarian cysts. The separate and combined use of GnRH and PGF2α commonly uses in the treatment of ovarian cysts. Therefore, in the presented study the effects of Beta-carotene (βC) addition for the treatment of ovarian cysts either with GnRH solely or GnRH and PGF2α in combination on the fertility parameters of dairy cows were investigated.Materials, Methods & Results: Seventy-six Holstein Friesian cows having ovarian cysts diagnosed by ultrasonography (USG) were divided into three groups. Cows in Group I (GI, n = 27), were injected with GnRH (Buserelin acetate, 5 mL, im), PGF2α (Tiaprost-trometamol, 5 mL, im) and βC (20 mL/cow, into 4 regions by im route). In Group II (GII, n = 25) GnRH (Buserelin acetate, 5 mL, im) and PGF2α (Tiaprost-trometamol, 5mL, im) were administrated while GnRH (Buserelin acetate, 5 mL, im) solely in Group III (GIII, n = 24). Cysts were monitored via USG, and blood samples were collected on the on day of treatment (day 0) and on the 7th and 14th days following the administrations. Cows shoving oestrous were inseminated and pregnancy diagnoses were performed on the 40th day following insemination. Treatment results showed that there were statistically no significant differences between GI and GII (P > 0.05). Only numerical difference obtained in time from therapy to pregnancy and overall pregnancy index (P > 0.05). Overall pregnancy rate (85 %), first service pregnancy rates (40 %) and overall pregnancy index (2.11) in GI were found significantly higher than GIII (53.3 %; 20 %; 4.12) [P 0.05).[...]

The effects of separate and combined use of PGF2α and GnRH hormones and the addition of beta-carotene on fertility parameters in dairy cows with ovarian cysts

Background: Ovarian cysts are commonly observed pathologies, which interfere with normal cyclic activity and adversely affect fertility in cows. Beta-carotene is effective in the reduction of reproductive problems by inducing the natural defence mechanisms of the body. There are several methods that can be used for the treatment of ovarian cysts. The separate and combined use of GnRH and PGF2α commonly uses in the treatment of ovarian cysts. Therefore, in the presented study the effects of Beta-carotene (βC) addition for the treatment of ovarian cysts either with GnRH solely or GnRH and PGF2α in combination on the fertility parameters of dairy cows were investigated.Materials, Methods & Results: Seventy-six Holstein Friesian cows having ovarian cysts diagnosed by ultrasonography (USG) were divided into three groups. Cows in Group I (GI, n = 27), were injected with GnRH (Buserelin acetate, 5 mL, im), PGF2α (Tiaprost-trometamol, 5 mL, im) and βC (20 mL/cow, into 4 regions by im route). In Group II (GII, n = 25) GnRH (Buserelin acetate, 5 mL, im) and PGF2α (Tiaprost-trometamol, 5mL, im) were administrated while GnRH (Buserelin acetate, 5 mL, im) solely in Group III (GIII, n = 24). Cysts were monitored via USG, and blood samples were collected on the on day of treatment (day 0) and on the 7th and 14th days following the administrations. Cows shoving oestrous were inseminated and pregnancy diagnoses were performed on the 40th day following insemination. Treatment results showed that there were statistically no significant differences between GI and GII (P > 0.05). Only numerical difference obtained in time from therapy to pregnancy and overall pregnancy index (P > 0.05). Overall pregnancy rate (85 %), first service pregnancy rates (40 %) and overall pregnancy index (2.11) in GI were found significantly higher than GIII (53.3 %; 20 %; 4.12) [P < 0.05]. No significant difference was observed in progesterone (P4) levels between the groups (P > 0.05).[...](AU)