Approaches to biosecurity in bovine embryo transfer programs

Although transfer of bovine embryos is much less likely to result in transmission of pathogens than transport of postnatal cattle, the epidemiologic risk associated with bovine embryo transfer merits examination. Much research has validated the efficacy of internationally approved processing protocols to render bovine in vivo-derived embryos free of specified pathogens. The purpose of this review is to summarize current sanitary recommendations for bovine embryo transfer, while emphasizing recent research to develop and validate novel approaches to biosecurity. Continued research will enable the development and validation of novel embryo treatments and culture reagents to minimize requirements for testing of embryo or oocyte donors, and testing of embryo recipients.     

Near infrared reflectance spectroscopy (NIRS) to predict biological parameters of maize silage: effects of particle comminution, oven drying temperature and the presence of residual moisture

Maize silage nutritive quality is routinely determined by near infrared reflectance spectroscopy (NIRS). However, little is known about the impact of sample preparation on the accuracy of the calibration to predict biological traits. A sample population of 48 maize silages representing a wide range of physiological maturities was used in a study to determine the impact of different sample preparation procedures (i.e., drying regimes; the presence or absence of residual moisture; the degree of particle comminution) on resultant NIR prediction statistics. All silages were scanned using a total of 12 combinations of sample pre-treatments. Each sample preparation combination was subjected to three multivariate regression techniques to give a total of 36 predictions per biological trait. Increased sample preparations procedure, relative to scanning the unprocessed whole plant (WP) material, always resulted in a numerical minimisation of model statistics. However, the ability of each of the treatments to significantly minimise the model statistics differed. Particle comminution was the most important factor, oven-drying regime was intermediate, and residual moisture presence was the least important. Models to predict various biological parameters of maize silage will be improved if material is subjected to a high degree of particle comminution (i.e., having been passed through a 1 mm screen) and developed on plant material previously dried at 60 °C. The extra effort in terms of time and cost required to remove sample residual moisture cannot be justified.     

Normal reproductive capacity of heifers that originated from in vitro fertilized embryos cultured with an antiviral compound

Bovine viral diarrhea virus (BVDV) can associate with in vitro fertilized (IVF) bovine embryos despite washing and trypsin treatment. An antiviral compound, DB606 (2-(4-[2-imidazolinyl]phenyl)-5-(4-methoxyphenyl)furan), inhibits the replication of BVDV in bovine uterine tubal epithelial cells, Madin Darby bovine kidney cells, and fetal fibroblast cells. As well, DB606 in in vitro culture medium does not affect embryonic development. Antiviral-treated-IVF embryos placed into recipients developed into clinically normal calves. The objective of this project was to determine if these resultant heifer calves were capable of reproducing. Seven heifers from each of the treatment groups (natural breeding, IVF embryo, and IVF embryo cultured in DB606) of the previous study were used. At 20-27 months of age, the heifers were exposed to a fertile bull in a single pasture during a 63 d breeding season. Five of the seven heifers originating from natural breeding were pregnant 35 d after removal of the bull and calved. All of the heifers resulting from transfer of untreated IVF embryos were pregnant at 35 d; however, one aborted the fetus at 5-7 months of gestation. All of the heifers derived from transfer of IVF embryos cultured in DB606 were pregnant and calved. Offspring from dams of all treatment groups were clinically normal at birth. Adjusted 205 d weaning weights were not significantly different among the offspring of the treated and untreated dams. These results indicate that culture of bovine-IVF embryos in DB606 does not impair future reproductive capacity of resulting heifers.     

Bovine viral diarrhea virus (BVDV) associated with single in vivo-derived and in vitro-produced preimplantation bovine embryos following artificial exposure

The objective was to determine the average amount of bovine viral diarrhea virus (BVDV) associated with single in vivo-derived and in vitro-produced bovine embryos following recommended processing procedures for embryos. In vivo-derived and in vitro-produced bovine embryos at 7 d post-fertilization were exposed (for 2 h) to 2 × 10^5-7 cell culture infective dose (CCID₅₀)/mL of SD-1 (a noncytopathic, Type 1a strain of BVDV), and then washed according to International Embryo Transfer Society (IETS) guidelines prior to testing. Of the 87 in vivo-derived embryos tested, 27% were positive for virus by quantitative polymerase chain reaction (qPCR). The range in amount of virus associated with 99% of the contaminated embryos was ≤6.62 ± 1.57 copies/5 μL; 90% of the contaminated embryos had ≤4.64 ± 1.57 viral copies/5 μL of embryo-associated virus, using tolerance intervals (P < 0.05). The SEM was 0.33 and the mean of averages was 1.12/5 μL. Of the 87 in vitro-produced embryos, 42% were positive for virus. The range in amount of virus associated with 99% of the contaminated embryos was ≤3.44 ± 0.89 copies/5 μL; 90% of the contaminated embryos had ≤2.40 ± 0.89 viral copies/5 μL of embryo-associated virus using tolerance intervals (P < 0.05; S.E.M. was 0.14 and the mean of averages was 0.55/5 μL). Therefore, although many embryos were positive for virus, there were limited numbers of copies, thereby posing doubt regarding their potential for contamination following embryo transfer.