Factors that interfere with oocyte quality for in vitro production of cattle embryos: effects of different developmental & reproductive stages

The success of IVP is ultimately dependent on the number and quality of the cumulus-oocyte complexes (COC) harvested during the OPU procedure. Several factors appear to be critical to oocyte quality including follicle size, environment factors such as heatstress, genetic background, age and lactation status of donor animals, all having a remarkable influence on the results of IVP. The aim of this review is to highlight some critical areas that can help veterinary practitioners to enhance OPU efficiency and successfully implement IVP into their routine practice. Focus will be given to recent findings in the literature and underlying physiological aspects that may be interfering with the quality of oocytes addressed to IVP in cattle at younger ages (calves and prepubertal heifers), pregnant vs nonpregnant status, and possible interactions with lactation and days postpartum during OPU.

Factors that interfere with oocyte quality for in vitro production of cattle embryos: effects of different developmental & reproductive stages

The success of IVP is ultimately dependent on the number and quality of the cumulus-oocyte complexes (COC) harvested during the OPU procedure. Several factors appear to be critical to oocyte quality including follicle size, environment factors such as heatstress, genetic background, age and lactation status of donor animals, all having a remarkable influence on the results of IVP. The aim of this review is to highlight some critical areas that can help veterinary practitioners to enhance OPU efficiency and successfully implement IVP into their routine practice. Focus will be given to recent findings in the literature and underlying physiological aspects that may be interfering with the quality of oocytes addressed to IVP in cattle at younger ages (calves and prepubertal heifers), pregnant vs nonpregnant status, and possible interactions with lactation and days postpartum during OPU.(AU)

Relationship between follicle population, AMH concentration and fertility in cattle

The size of ovarian follicular population evaluated by direct antral follicular count or endocrine markers can help determine the success of reproductive biotechnologies in cattle. However, although highly repeatable within animal, the antral follicular population (AFP) appears to be greatly variable across individuals. Therefore, laboratory methods that reliably predict AFP could have a significant value to select donor-cows for use in reprodutive biotechnology and for genomic selection of animals with greater reproductive potential. Accordingly, the circulating levels of anti-Müllerian hormone (AMH) have been found to be associated with AFP and, thereby, identified as an important endocrinemarker of superovulation response and in vitro embryo production in cattle. Moreover, a number of recent publications and ongoing studies are trying to determine whether circulating levels of AMH are correlated with fertility. This review summarizes recent information concerning AFP and its association with AMH, and the possibility of utilizing AMH as a marker for reproductive technologies and ultimately to enhance cattle fertility.(AU)

Relationship between follicle population, AMH concentration and fertility in cattle

The size of ovarian follicular population evaluated by direct antral follicular count or endocrine markers can help determine the success of reproductive biotechnologies in cattle. However, although highly repeatable within animal, the antral follicular population (AFP) appears to be greatly variable across individuals. Therefore, laboratory methods that reliably predict AFP could have a significant value to select donor-cows for use in reprodutive biotechnology and for genomic selection of animals with greater reproductive potential. Accordingly, the circulating levels of anti-Müllerian hormone (AMH) have been found to be associated with AFP and, thereby, identified as an important endocrinemarker of superovulation response and in vitro embryo production in cattle. Moreover, a number of recent publications and ongoing studies are trying to determine whether circulating levels of AMH are correlated with fertility. This review summarizes recent information concerning AFP and its association with AMH, and the possibility of utilizing AMH as a marker for reproductive technologies and ultimately to enhance cattle fertility.

Effect of uterine environment on embryo production and fertility in cows

Oocyte fertilization rates in bovines following artificial insemination or natural mating are generally good (~90%). Curiously, only about one third of these pregnancies remain until 30 days post-AI in dairy cows. Thus, most pregnancies are lost between fertilization and early embryonic growth. Although classical pathways describing that lower progesterone post-AI is the main culprit to these early embryonic losses, a number of environmental factors such as heat-stress as well as novel concepts in bovine physiology including the effects of excessive negative energy balanced (NEB) and the insulin-resistant state experienced by high producing cows during the postpartum period can help explain the poor reproductive performance, generally observed in dairy herds world-wide. Thus, expanding the scientific knowledge in these critical areas in bovine fertility related to the evident impact of NEB and/or altered circulating and uterine metabolites in the postpartum period on oocyte quality; gamete transport, uterine environment, and early embryonic growth are of major importance to improve reproductive efficiency in modern high producing dairy cows.

The physiology and impact on fertility of the period of proestrus in lactating dairy cows

In cattle, proestrus begins with the initiation of luteolysis and ends with initiation of estrus and the GnRH/LH surge. This period is marked by a dramatic decrease in circulating progesterone (P4 ) that reaches a nadir by about 36-48 h in cows undergoing natural or prostaglandin F2α (PGF )-induced luteolysis. Inadequate luteolysis is a cause of reduced fertility particularly in timed AI programs with small elevations in circulating P4 reducing fertility. Increasing circulating estradiol ( E2 ) during proestrus is dependent on presence, size, and function of the dominant follicle and this varies during natural proestrus, due to whether animals have two or three follicular waves, and during PGF-induced proestrus, according to stage of the follicular wave at time of PGF treatment. Inadequate circulating E2 can limit fertility and increase pregnancy loss in some specific circumstances such as in cows with low BCS and in cows during heat stress. Thus, studies to optimize the length of proestrus and the concentrations of E2 and P4 during proestrus could produce substantial improvements in fertility and reductions in pregnancy loss.

The physiology and impact on fertility of the period of proestrus in lactating dairy cows

In cattle, proestrus begins with the initiation of luteolysis and ends with initiation of estrus and the GnRH/LH surge. This period is marked by a dramatic decrease in circulating progesterone (P4 ) that reaches a nadir by about 36-48 h in cows undergoing natural or prostaglandin F2α (PGF )-induced luteolysis. Inadequate luteolysis is a cause of reduced fertility particularly in timed AI programs with small elevations in circulating P4 reducing fertility. Increasing circulating estradiol ( E2 ) during proestrus is dependent on presence, size, and function of the dominant follicle and this varies during natural proestrus, due to whether animals have two or three follicular waves, and during PGF-induced proestrus, according to stage of the follicular wave at time of PGF treatment. Inadequate circulating E2 can limit fertility and increase pregnancy loss in some specific circumstances such as in cows with low BCS and in cows during heat stress. Thus, studies to optimize the length of proestrus and the concentrations of E2 and P4 during proestrus could produce substantial improvements in fertility and reductions in pregnancy loss.(AU)

Effect of uterine environment on embryo production and fertility in cows

Oocyte fertilization rates in bovines following artificial insemination or natural mating are generally good (~90%). Curiously, only about one third of these pregnancies remain until 30 days post-AI in dairy cows. Thus, most pregnancies are lost between fertilization and early embryonic growth. Although classical pathways describing that lower progesterone post-AI is the main culprit to these early embryonic losses, a number of environmental factors such as heat-stress as well as novel concepts in bovine physiology including the effects of excessive negative energy balanced (NEB) and the insulin-resistant state experienced by high producing cows during the postpartum period can help explain the poor reproductive performance, generally observed in dairy herds world-wide. Thus, expanding the scientific knowledge in these critical areas in bovine fertility related to the evident impact of NEB and/or altered circulating and uterine metabolites in the postpartum period on oocyte quality; gamete transport, uterine environment, and early embryonic growth are of major importance to improve reproductive efficiency in modern high producing dairy cows. (AU)

Effects of energy and protein nutritionin the dam on embryonic development

This review highlights the importance of energy and protein nutrition of the dam on embryo production and embryo development. Fertility is reduced by greater negative energy balance post-partum as manifest by reductions in fertility and embryo quality associated with lower body condition score (BCS) but particularly with greater postpartum loss of BCS. In addition, excessive energy intake, particularly from high carbohydrate diets can reduce fertilization and embryo quality in some but not all circumstances. High protein diet s have been found to reduce embryo quality by day 7 after breeding, possibly due to greater blood urea nitrogen, however this negative effect is not observed in all studies. Sufficient circulating concentrations of amino acids, particularly rate-limiting amino acids such as methionine and lysine are critical for optimal milk production. The rate-limiting amino acids may also impact embryonic development, perhaps through improved amino acid profiles in the uterine lumen. Methionine may also have direct epigenetic effects in the embryo by methylation of DNA. Future studies are needed to replicate previously observed positive and negative effects of energy, excess protein, and amino acid supplementation in order to provide further insight into how embryonic development can be rationally manipulated using nutritional strategies.

Effects of energy and protein nutritionin the dam on embryonic development

This review highlights the importance of energy and protein nutrition of the dam on embryo production and embryo development. Fertility is reduced by greater negative energy balance post-partum as manifest by reductions in fertility and embryo quality associated with lower body condition score (BCS) but particularly with greater postpartum loss of BCS. In addition, excessive energy intake, particularly from high carbohydrate diets can reduce fertilization and embryo quality in some but not all circumstances. High protein diet s have been found to reduce embryo quality by day 7 after breeding, possibly due to greater blood urea nitrogen, however this negative effect is not observed in all studies. Sufficient circulating concentrations of amino acids, particularly rate-limiting amino acids such as methionine and lysine are critical for optimal milk production. The rate-limiting amino acids may also impact embryonic development, perhaps through improved amino acid profiles in the uterine lumen. Methionine may also have direct epigenetic effects in the embryo by methylation of DNA. Future studies are needed to replicate previously observed positive and negative effects of energy, excess protein, and amino acid supplementation in order to provide further insight into how embryonic development can be rationally manipulated using nutritional strategies.(AU)

Positive and negative effects of proges terone during timed AI protocols in lactating dairy cattle

Circulating concentration of progesterone (P4) is determined by a balance between P4 production, primarily by corpus luteum (CL), and P4 metabolism, primarily by liver. The volume of large luteal cells in the CL is a primary factor regulating P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in dairy cattle. 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. Dietary manipulations, such as fat supplementation, can also be used to alter circulating P4. Elevating P4 prior to the timed AI generally decreases double ovulation an d can increase fertility to the timed AI. This appears to be an effect of P4 during the follicular wave that produces the future ovulatory follicle, possibly by altering the oocyte and subsequent embryo. Near the time of AI, slight elevations in circulating P4 can dramatically reduce fertility. The etiology of slight elevations in P4 near AI is inadequate luteolysis to the prostaglandin F2 α (PGF) treatment prior to timed AI. 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. Combining results of these studies indicated only marginal fertility benefits of <5%. In conclusion, previous research has provided substantial insight into the effects of supplemental P4 on fertility and there is increasing insight into the mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future re search on P4 manipulation to improve timed AI protocols.

Positive and negative effects of proges terone during timed AI protocols in lactating dairy cattle

Circulating concentration of progesterone (P4) is determined by a balance between P4 production, primarily by corpus luteum (CL), and P4 metabolism, primarily by liver. The volume of large luteal cells in the CL is a primary factor regulating P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in dairy cattle. 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. Dietary manipulations, such as fat supplementation, can also be used to alter circulating P4. Elevating P4 prior to the timed AI generally decreases double ovulation an d can increase fertility to the timed AI. This appears to be an effect of P4 during the follicular wave that produces the future ovulatory follicle, possibly by altering the oocyte and subsequent embryo. Near the time of AI, slight elevations in circulating P4 can dramatically reduce fertility. The etiology of slight elevations in P4 near AI is inadequate luteolysis to the prostaglandin F2 α (PGF) treatment prior to timed AI. 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. Combining results of these studies indicated only marginal fertility benefits of <5%. In conclusion, previous research has provided substantial insight into the effects of supplemental P4 on fertility and there is increasing insight into the mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future re search on P4 manipulation to improve timed AI protocols.(AU)

Morphological abnormalities and apoptosis in lamellar tissue of equines after intestinal obstruction and treatment with hydrocortisone / Alterações morfológicas e apoptose em tecido laminar de equinos após obstrução intestinal e tratamento com hidrocortisona

Four experimental groups of equines were used in order to study morphological abnormalities and apoptosis in lamellar tissue. Group Cg (control) was composed of animals without any surgical procedure; group Ig (instrumented), animals that underwent enterotomy; group Tg (treated), animals that were subjected to intestinal obstruction and were treated with hydrocortisone; and group Ug (untreated), animals that were subjected to intestinal obstruction without treatment. The lamellar tissue was analyzed regarding the presence of tissue abnormalities and apoptosis. No morphological abnormalities were observed in animals of surgical groups, and no difference in apoptosis was observed between groups. It was concluded that intestinal obstruction allowed laminitis to develop, probably by systemic activation, and that the maneuvers performed in the enterotomy aggravated the process. Hydrocortisone did not aggravate the lesions of the lamellar tissue.(AU)

Foram utilizados quatro grupos de equinos para estudar alterações morfológicas e apoptose no tecido lamelar. O grupo CG (controle) foi composto por animais sem o procedimento cirúrgico; o grupo Ig (instrumentado), por animais submetidos à enterotomia; o grupo Tg (tratado), por animais submetidos à obstrução intestinal e tratados com hidrocortisona; e o grupo Ug (não tratado), por animais submetidos à obstrução intestinal, sem tratamento. O tecido laminar foi analisado quanto à presença de alterações morfológicas e de apoptose. Foram observadas alterações morfológicas nos equinos submetidos a procedimento cirúrgico, mas não houve diferença entre os grupos com relação às células apoptóticas. Conclui-se que a obstrução intestinal permite o desenvolvimento da laminite provavelmente por ativação sistêmica e que as manobras realizadas na enterotomia podem ser consideradas como agravantes no processo. A hidrocortisona não agravou as lesões do tecido laminar.(AU)

Dimethyl sulfoxide effects on the febrile response to lipopolysaccharide injection in rabbits / Efeitos do dimetil sulfóxido sobre a resposta febril induzida pela injeção de lipopolissacarídeo em coelhos

The present study was designed to determine whether DMSO causes an inhibition on the development of fever in rabbits. The intravenous administration of LPS (1.5µg.kg-1 body weight) caused fever in both saline+LPS and DMSO+LPS group, but the onset and magnitude of the induced fever were significantly different. The saline+LPS group presented a prototypic biphasic fever whereas the DMSO+LPS group presented an attenuated febrile response, but it was not abolished. These results suggest that DMSO may provide a protective mechanism against pyrogen LPS, probably through the modulation of NF-kB mediated events, such as fever.(AU)

Estudaram-se os efeitos do DMSO na resposta febril induzida pela administração intravenosa de LPS em coelhos. A administração intravenosa de LPS (1,5µg.kg-1 peso vivo) causou febre mesmo na presença do DMSO. No entanto, o início e a magnitude da febre induzida foram significativamente menores no grupo tratado com DMSO enquanto o LPS isolado induziu resposta febril bifásica. Estes resultados sugerem que o DMSO pode exercer um mecanismo protetor contra a ação pirogênica do LPS, provavelmente por meio da modulação dos eventos mediados pelo NF-kB, entre eles, a febre.(AU)

Efeitos da administração epidural de amitraz, xilazina ou dimetil sulfóxido em vacas / Effects of epidural injection of amitraz, xylazine or dimethyl sulfoxide in cows

Avaliaram-se os efeitos da injeção epidural de amitraz (0,4mg/kg), xilazina (0,05mg/kg) ou dimetil sulfóxido 10% (5,0ml) sobre a freqüência cardíaca (FC), pressão arterial sistólica (PAS), freqüência respiratória (FR), motilidade ruminal (MR), temperatura retal (TR), altura de cabeça (AC) e latência das respostas a estímulos nociceptivos nas regiões da coxa (LECC) e coroa do casco (LRRM) de vacas. Houve diminuição da FC e da MR nos grupos xilazina e amitraz. O tratamento com xilazina resultou em alterações na FR, PAS e AC. LECC e LRRM foram maiores nos tratamentos com agonistas a-2. Nas doses utilizadas, o amitraz aumentou a latência de resposta a estímulo nociceptivo em menor grau que a xilazina, sem induzir efeitos colaterais sistêmicos severos, em vacas.(AU)

The effects of epidurally amitraz (0.4mg/kg), xylazine (0.05mg/kg) or 10% dimethyl sulfoxide (5.0ml) over heart rate (HR), systolic arterial pressure (SAP), respiratory rate (RR), ruminal motility (RM), rectal temperature (RT), head height (HH), and latency to heat-evoked reflexes (LSPR skin of perineal region; LHWR hoof withdrawal reflex) were evaluated in cows. HR and RM decreased in amitraz and xylazine groups. Only xylazine group showed statistical difference over RR, SAP and HH. LSPR and LHWR were prolonged in both a-2 agonist groups. Amitraz epidural administration does not induce severe systemic effects, and induces prolongation of the latency to heat-evoked reflexes in a minor degree than xylazine, at the used dosages, in cows.(AU)

Modified E-test by the addition of EDTA-Tris and dimethyl sulfoxide on the potentiation of the effects of some antimicrobials in Pseudomonas aeruginosa strains isolated from bovine mastitis / E-test modificado pela adição de Tris-EDTA e dimetilsulfóxido na potencialização do efeito de antimicrobianos em linhagens de Pseudomonas aeruginosa isoladas de mastite bovina

A concentração inibitória mínima-MIC em 30 estirpes de Pseudomonas aeruginosa isoladas de mastite bovina foi avaliada utilizando o E-test padrão e o método modificado, pela adição de Tris-EDTA e DMSO. Os métodos modificados apresentaram redução significativa da MIC das estirpes utilizando a gentamicina, a ciprofloxacina e a norfloxacina.(AU)

Efeito da aplicação de prostaglandina (PGF2alfa) no pós-parto imediato sobre a incidência de retenção de placenta em vacas de leite / The effect of Prostaglandins (PGF2alpha) injection in the early post partum period on the incidence of retained placenta in dairy cows

Este trabalho teve como objetivo avaliar o efeito da aplicação de prostaglandina na primeira hora pós-parto sobre a incidência de retenção de placenta 8 e 12 horas pós-parto. Foram utilizadas 82 vacas como controle e 82 vacas tratadas com 25mg de prostaglandina (LUTALYSEr, 5ml). Vacas tratadas com PGF2a liberaram a placenta mais rápido (P<0,10) do que as não tratadas (7,72ñ0,84 vs. 10,07ñ1,09h). A incidência de retenção de placenta com mais de oito horas foi 30,5 por cento no grupo-controle e 17,1 por cento no grupo-tratado (P<0,05) e com mais de 12 horas, 19,5 por cento no grupo-controle e 12,2 por cento no grupo-tratado (P<0,10). Verificou-se também que fazenda, índice de condição corporal e ordem de lactação tiveram influência na ocorrência de retenção de placenta, mas não se verificou efeito do sexo do bezerro nem da ajuda ao parto. Estes dados mostram que o tratamento com prostaglandina na primeira hora pós-parto pode ser usado como preventivo da retenção de placenta.(AU)

The purpose of this study was to evaluate the effect of an intramuscular injection of prostaglandin, within the first hour post partum, on the incidence of retained fetal membranes in cows, at 8 and 12 hours post-partum. Eighty-two cows were used as controls and 82 were treated with 25mg of prostaglandin (LUTALYSE®, 5ml), in two different farms. Cows treated with PGF2a released the placenta faster (P<0.10) than cows in the control group (7.72±0.84 vs. 10.07±1.09h). The incidence of retained placenta with more than 8h post partum was 30.5% in the control group and 17.1% in the treated group (P<0.05), and with more than 12h was 19.5% in the control group and 12.2% in the treated group (P<0.10). Farm, body condition score and parity showed influence on retained placenta rates, whereas sex of calf and help during calving did not have influence. These data showed that prostaglandin treatment within the first hour post-partum is capable of reduce the incidence of retained placenta and may work as a preventive treatment.(AU)