Effect of cortisol in vitro and in vivo on production of bovine interleukin 2

The influence of cortisol in vitro and in vivo on lymphocyte proliferative responses and interleukin 2 (IL2) production was evaluated in Hereford feeder calves. Cortisol, added to bovine mononuclear cell cultures, reduced (P less than 0.05) mitogen-stimulated lymphocyte proliferative responses and IL2 production. Lower IL2 activity from cortisol-treated cell cultures was not caused by a cortisol-mediated cytotoxicity or a residual cortisol effect on the IL2-indicator cell line. Calves given ACTH (1.0 IU/kg of body weight, IM) twice daily for 2 days had increased (P less than 0.001) plasma cortisol concentrations when compared with those of saline-treated controls. Leukocytosis (P less than 0.002), characterized mainly by a neutrophilia (P less than 0.007), was evident in ACTH-treated calves. Lymphocyte proliferative responses to the phytomitogens, concanavalin A, phytohemagglutinin, and pokeweed mitogen were decreased (P less than 0.05) in calves with increased plasma cortisol concentrations. Interleukin 2 production was lower (P less than 0.05) in concanavalin A-stimulated lymphocyte cultures from ACTH-treated calves. Seemingly, lower lymphocyte proliferative responses in cortisol-treated mononuclear cell cultures and in ACTH-treated calves were caused partly by lower IL2 production.     

Replication of bovine viral diarrhoea virus in the bovine reproductive tract and excretion of virus in semen during acute and chronic infections.

Five mature bulls were studied during an acute transient infection with bovine viral diarrhoea virus (BVDV). The bulls had been infected experimentally by the intranasal instillation of blood and serum from a cow which was a persistent carrier of the virus. Infection was confirmed by the demonstration of a low titred viraemia in four of the five animals and by the seroconversion of all five. Semen samples were collected from each bull on four occasions between seven and 14 days after infection. The virus was isolated from the semen of three of the five bulls and from nine of 12 batches of semen from them. In contrast to other studies of the infection of semen, BVDV was isolated with similar efficiency from raw, unprocessed semen and from diluted, extended semen. The titres of virus in the semen ranged from 5 to 75 TCID50/ml. The infection did not appear to affect the quality of the semen. Shedding of virus continued after the end of the period of viraemia and appeared to be a consequence of the replication of the virus in the reproductive tract and its subsequent excretion in the seminal fluid. Virological studies of the reproductive tracts of these bulls suggested that the most productive sites of virus replication were the seminal vesicles and the prostate gland. Concurrent studies in a persistently infected bull supported these findings.     

Effect of progesterone on the immune system in consideration of bovine placental retention

Effects of progesterone on the immune system of different species are presented by a literature study. Elevated progesterone concentrations in blood result in more severe course and longer persistence of bacteria in infectious diseases and decrease of the clearance of antibody-coated erythrocytes in vivo. Progesterone suppresses specific components of the immune system and natural killer (NK) cell activity while it has a mainly positive influence on other nonspecific components. It suppresses blastogenesis and cytotoxicity of lymphocytes and increases synthesis of asymmetric antibodies without effector function to block fetal antigens. Progesterone increases the concentration of leucocytes in blood, random migration and chemotactic ability, synthesis of reactive oxygen intermediates (ROI) and antibody-dependent cellular cytotoxicity of polymorphonuclear leucocytes (PMN) and expression of complement receptors, synthesis of ROI and phagocytosis of peritoneal macrophages. In the uterus mainly immunosuppressive effects of progesterone are described (decreased migration of PMN into the gravid uterus, persistence of bacteria or transplants, synthesis of immunosuppressive uterine milk proteins, decreased random migration of PMN) except for an increased content of IgA in the secretory products indicating a significance of progesterone in the pathogenesis of endometritis mainly in the cow and bitch. No correlation could be found between blood concentrations of progesterone and placental retention in cattle. Progesterone takes part in avoiding immunologic aggression of the maternal organism against the semiallogenic conceptus by suppressing specific components of the immune system and NK cell activity. Positive effects on nonspecific components of the immune system could be regarded as compensatory mechanisms to maintain the efficiency of the complete immune system.     

Observations on histamine, serotonin, cortisol and cortisol binding globulins in bovine anaplasmosis

Changes in histamine, serotonin, cortisol and cortisol binding globulin (CBG) levels were observed in Anaplasma marginale-infected bovine calves. In addition, packed cell volume (PCV), platelet number and percentage parasitaemia were also recorded. The whole blood histamine and serotonin values rose significantly (P less than 0.01 and P less than 0.025, respectively) during the acute stage of Anaplasma infection. Higher serum cortisol and CBG levels (P less than 0.05) were observed in acute and carrier infections, respectively. A sharp drop in thrombocyte count (59%) and PCV (33%) was also noticed in clinical anaplasmosis. The results suggest that the higher levels of biogenic amines which are known to produce increased vasodilation, capillary permeability and tissue anoxia and hypercortisolaemia to protect animals from stress and cell damage may play a similar role in the pathogenesis of acute anaplasmosis.     

Survival of infectious bovine rhinotracheitis virus in stored bovine semen

No loss in the titre of infectious bovine rhinotracheitis virus was found during storage in semen at –196°C for 1 year.     

Effect of chemotherapy on elevated ejaculation time and deteriorated semen characteristics consequent to bovine trypanosomiasis

The effect of the trypanocidal drug Novidium on elevated ejaculation time and deteriorated semen characteristics was studied in Zebu cattle infected with T. vivax and T. congolense. Two groups, comprising six bulls per group, were infected with Trypanosoma vivax or Trypanosoma congolense while three bulls served as controls. Chemotherapy was carried out 12 weeks post-infection on three bulls from each group, leaving three bulls untreated while three bulls served as uninfected controls. Blood samples from treated bulls were all negative for trypanosomes 3 days post-chemotherapy. The animals also had normal body temperature. As the study progressed, clinical signs associated with trypanosomiasis, such as anaemia and cachexia, disappeared gradually in treated bulls. There was some improvement in semen characteristics of some of the bulls at 10 weeks post-chemotherapy with Novidium. However, all bulls infected with T. vivax or T. congolense irrespective of Novidium chemotherapy still had poor semen characteristics manifested by all or some of the following: decreased volume of semen, oligospermia, azoospermia and elevated incidence of spermatozoa morphological abnormalities. They were thus unsuitable for breeding.     

Evidence of excretion of Schmallenberg virus in bull semen

Schmallenberg virus (SBV) is a novel orthobunyavirus, discovered in Germany in late 2011. It mainly infects cattle, sheep and goats and could lead to congenital infection, causing abortion and fetal abnormalities. SBV is transmitted by biting midges from the Culicoides genus and there is no evidence that natural infection occurs directly between ruminants. Here, we could detect SBV RNA in infected bull semen using qRT-PCR (three bulls out of seven tested positive; 29 positive semen batches out of 136). We also found that highly positive semen batches from SBV infected bulls can provoke an acute infection in IFNAR^-/- mice, suggesting the potential presence of infectious virus in the semen of SBV infected bulls.     

Effect of the preovulatory LH surge on bovine follicular progesterone receptor mRNA expression

A growing body of evidence indicates that intrafollicular progesterone receptor signaling pathways are obligatory for follicle rupture. However, the intrafollicular localization and regulation of progesterone receptor expression during the periovulatory period in cattle are not known. In this study, we determined the effect of the preovulatory gonadotropin surge on localization and expression of progesterone receptor mRNA in bovine periovulatory follicular and luteal tissue. Ovaries containing preovulatory follicles or new corpora lutea (CL) were collected at approximately 0, 6, 12, 18, 24 (preovulatory follicles) and 48 h (CL) after a GnRH-induced LH surge (n=5-8 per timepoint). Expression of progesterone receptor mRNA was detected in periovulatory follicular and luteal tissue at all timepoints examined. Relative levels of progesterone receptor mRNA were dramatically upregulated within 6h after the LH surge compared to all other time points (P<0.0001). In situ hybridization analysis revealed that the significant increase in progesterone receptor mRNA expression was localized to the granulosal layer of preovulatory follicles. Our results indicate that progesterone receptor mRNA expression is upregulated specifically in the granulosal layer of bovine preovulatory follicles following the LH surge. Progesterone receptor signaling pathways may help mediate the effects of the preovulatory LH surge on follicle rupture in cattle.     

The value of sexed bovine semen

Semen sexing may be used in a variety of practical situations, where part (or all) of the herd may be inseminated with X‐ and Y‐chromosome‐enriched semen. Expressions are presented to calculate the net present value of progeny derived from a semen dose, dependent on the values of females and males, and on the efficiency of sexing. Sexed semen allows selling a higher proportion of the more valuable sex and also increases the value of animals retained for breeding through more intense selection. The expressions to economically evaluate sexed semen are quite general but numerical examples are presented for several practical situations of interest in Brazil.     

Evaluation of semen collected by electroejaculation from captive lesser Malay chevrotain (Tragulus javanicus).

Thirteen sexually mature captive male lesser Malay chevrotains (Tragulus javanicus) were each anesthetized twice with tiletamine-zolazepam for electroejaculation. Viable spermatozoa were collected from all animals. The semen was creamy, milky, pale yellowish, or watery. The mean values for ejaculate volume, sperm concentration, and percentages of sperm motility, normality and viability were 23.7 +/- 2.5 microl, 366.9 +/- 127.8 x 10(6) spermatozoa/ml, 40.0% +/- 3.1%, 71.4% +/- 1.6%, and 59.6% +/- 2.1%, respectively. Semen pH was 7-8. No adverse effects of electroejaculation were noted. These are the first reported values for semen of lesser Malay chevrotain. Electroejaculation should be usable for routine semen collection in this species.