Comparison of various semen extenders and addition of prostaglandin F2α on pregnancy rate in cows.

This investigation comprises three trials. Trial 1 consists of an in vitro comparison of three semen extenders: two egg yolk based (customized Tris-egg yolk-glycerol and Triladyl®), the third (AndroMed®) soybean lecithin based. With regard to post-thaw motility, the phytoextender AndroMed® proved to be superior (59±3% v. 53±2% and 53±2%, P<0.05). It had earlier been shown that addition of the commercial prostaglandin F2α preparation Dinolytic® before freezing compromises post-thaw motility; therefore, in Trial 2, Dinolytic® was added after thawing. Frozen-thawed spermatozoa tolerated addition of Dinolytic® at a concentration of 30% (v/v). In Trial 3, cows were inseminated using straws in which diluted semen and Dinolytic® were frozen in the same straw, separated by an air bubble, so intermingling could only take place in the course of insemination. Pregnancy rates at Dinolytic® dosages of 0%, 30% or 60% amounted to 44%, 41% and 56%, respectively (P>0.05), a result that encourages a large-scale field study, which is envisioned.

Fixed-time Insemination in Pasture-based Medium-sized Dairy Operations of Northern Germany and an Attempt to Replace GnRH by hCG.

A field study was conducted aimed at (i) evaluating the practicability of a fixed-time insemination regime for medium-sized dairy operations of north-western Germany, representative for many regions of Central Europe and (ii) substituting hCG for GnRH as ovulation-inducing agent at the end of a presynch or ovsynch protocol in an attempt to reduce the incidence of premature luteal regression. Cows of two herds synchronized by presynch and two herds synchronized by ovsynch protocol were randomly allotted to three subgroups; in one group ovulation was induced by the GnRH analog buserelin, in another by hCG, whereas a third group remained untreated. The synchronized groups were fixed-time inseminated; the untreated group bred to observed oestrus. Relative to untreated herd mates, pregnancy rate in cows subjected to a presynch protocol with buserelin as ovulation-inducing agent was 74%; for hCG it was 60%. In cows subjected to an ovsynch protocol, the corresponding relative pregnancy rates reached 138% in the case of buserelin and 95% in the case of hCG. Average service interval was shortened by 1 week in the presynch and delayed by 2 weeks in the ovsynch group. It may be concluded that fixed-time insemination of cows synchronized via ovsynch protocol with buserelin as ovulation-inducing agent is practicable and may help improve efficiency and reduce the work load involved with herd management in medium-sized dairy operations. The substitution of hCG for buserelin was found to be not advisable.

Detection of bovine herpesvirus type 1 in blood from naturally infected cattle by using a sensitive PCR that discriminates between wild-type virus and virus lacking glycoprotein E.

In the present study, we report for the first time on the detection of bovine herpesvirus type 1 (BHV-1) in whole-blood samples derived from naturally infected cattle. Sensitive PCR assays specific for glycoprotein B (gB), gC, and gE of BHV-1 allow the detection of one BHV-1 DNA copy in 10(5) to 10(7) peripheral blood leukocytes (PBLs). The incidence of BHV-1-positive PBLs in naturally infected cattle appears to be quite high (92.2% positive PBLs among all samples tested), although in most cases only between 10(-5) and 10(-7) positive leukocytes were present. The results demonstrate that the viral DNA is detectable not only in the peripheral blood of acutely infected animals but, more importantly, also in the peripheral blood of subclinically infected cattle. The gE-specific PCR described in the report allows discrimination between wild-type (WT) virus-infected and vaccinated animals, which is of importance for control programs that use the recently introduced vaccination strategy with a gE-negative virus. The results further show that doubtful serological results can be verified or falsified and that individual animals can be monitored for the presence or absence of WT BHV-1 or gE-negative virus in cattle herds. The PCR protocols allow the detection of BHV-1 prior to seroconversion or in BHV-1-seronegative cattle. Finally, the results indicate the simultaneous presence of WT and gE-negative vaccine virus in the PBLs of several cattle. Therefore, investigations of viremia in naturally and experimentally infected cattle and on the identification of infected cell types of bovine PBLs can be now performed.