Transvaginal ultrasound-guided oocyte retrieval in cattle: State-of-the-art and its impact on the in vitro fertilization embryo production outcome

Transvaginal ultrasound-guided oocyte retrieval (commonly called OPU) and in vitro embryo production (IVP) in cattle has shown significant progress in recent years, in part, as a result of a better understanding of the full potential of these tools by end users. The combination of OPU and IVP (OPU-IVP) has been successfully and widely commercially used worldwide. The main advantages are a greater number of embryos and pregnancies per unit of time, faster genetic progress due to donor quick turn around and more elite sires mating combinations, larger spectrum of female age (calves, prepuberal, heifer, cow) and condition (open, pregnant) from which to retrieve oocytes, a reduced number of sperm (even sexed) required to fertilize the oocytes, among other benefits. OPU-IVP requires significant less donor preparation in comparison to conventional embryo transfer (<50% of usual FSH injections needed) to the extent of no stimulating hormones (FSH) are necessary. Donor synchronization, stimulation, OPU technique, oocyte competence, embryo performance, and its impact on cryopreservation and pregnancy are discussed.

A Reference Genome Assembly of Simmental Cattle, Bos taurus taurus

Genomics research has relied principally on the establishment and curation of a reference genome for the species. However, it is increasingly recognized that a single reference genome cannot fully describe the extent of genetic variation within many widely distributed species. Pangenome representations are based on high-quality genome assemblies of multiple individuals and intended to represent the broadest possible diversity within a species. A Bovine Pangenome Consortium (BPC) has recently been established to begin assembling genomes from more than 600 recognized breeds of cattle, together with other related species to provide information on ancestral alleles and haplotypes. Previously reported de novo genome assemblies for Angus, Brahman, Hereford, and Highland breeds of cattle are part of the initial BPC effort. The present report describes a complete single haplotype assembly at chromosome-scale for a fullblood Simmental cow from an F1 bison-cattle hybrid fetus by trio binning. Simmental cattle, also known as Fleckvieh due to their red and white spots, originated in central Europe in the 1830s as a triple-purpose breed selected for draught, meat, and dairy production. There are over 50 million Simmental cattle in the world, known today for their fast growth and beef yields. This assembly (ARS_Simm1.0) is similar in length to the other bovine assemblies at 2.86 Gb, with a scaffold N50 of 102 Mb (max scaffold 156.8 Mb) and meets or exceeds the continuity of the best Bos taurus reference assemblies to date.

A Reference Genome Assembly of American Bison, Bison bison bison

Bison are an icon of the American West and an ecologically, commercially, and culturally important species. Despite numbering in the hundreds of thousands today, conservation concerns remain for the species, including the impact on genetic diversity of a severe bottleneck around the turn of the 20th century and genetic introgression from domestic cattle. Genetic diversity and admixture are best evaluated at genome-wide scale, for which a high-quality reference is necessary. Here, we use trio binning of long reads from a bison-Simmental cattle (Bos taurus taurus) male F1 hybrid to sequence and assemble the genome of the American plains bison (Bison bison bison). The male haplotype genome is chromosome-scale, with a total length of 2.65 Gb across 775 scaffolds (839 contigs) and a scaffold N50 of 87.8 Mb. Our bison genome is ~13× more contiguous overall and ~3400× more contiguous at the contig level than the current bison reference genome. The bison genome sequence presented here (ARS-UCSC_bison1.0) will enable new research into the evolutionary history of this iconic megafauna species and provide a new tool for the management of bison populations in federal and commercial herds.

Clinical and genetic spectrum of SCN2A-associated episodic ataxia

BACKGROUND

Pathogenic variants in SCN2A are associated with various neurological disorders including epilepsy, autism spectrum disorder and intellectual disability. Few reports have recently described SCN2A-associated episodic ataxia (EA). Our study identifies its broader clinical and genetic spectrum, and describes pharmacological approaches.

RESULTS

We report 21 patients with SCN2A-associated EA, of which 9 are unpublished cases. The large majority of patients present with epileptic seizures (18/21, 86%), often starting within the first three months of life (12/18, 67%). In contrast, onset of episodic ataxia ranged from 10 months to 14 years of age. The frequency of EA episodes ranged from brief, daily events up to 1-2 episodes per year each lasting several weeks. Potential triggers include minor head traumas and sleep deprivation. Cognitive outcome is favorable in most patients with normal or mildly impaired cognitive development in 17/21 patients (81%). No clear genotype-phenotype correlations were identified in this cohort. However, two mutational hotspots were identified, i.e. 7/21 patients (33%) harbor the identical pathogenic variant p.A263V, whereas 5/21 (24%) carry pathogenic variants that affect the S4 segment and its cytoplasmic loop within the domain IV. In addition, we identified six novel pathogenic variants in SCN2A. While acetazolamide was previously reported as beneficial in SCN2A-associated EA in one case, our data show a conflicting response in 8 additional patients treated with acetazolamide: three of them profited from acetazolamide treatment, while 5/8 did not.

CONCLUSIONS

Our study describes the heterogeneous clinical spectrum of SCN2A-associated EA, identifies two mutational hotspots and shows positive effects of acetazolamide in about 50%.

170 POST-THAW VIABILITY OF IN VITRO-PRODUCED BOVINE EMBRYOS CULTURED EITHER IN HOST CAPRINE REPRODUCTIVE TRACTS OR IN VITRO

In vitro culture of bovine embryos is usually associated with poor pregnancy rate following cryopreservation. The objective of this study was to compare the post-thaw viability of in vitro-produced bovine zygotes, cultured in vitro or in the reproductive tract of a host goat. Cumulus-oocyte complexes were matured in vitro, and in vitro fertilization was carried out with frozen-thawed semen as per standard laboratory procedures. At 18-20 h post-fertilization, zygotes were stripped of remaining cumulus cells and randomly separated into culture treatments. In three replicates, a total of 606 embryos were surgically transferred 12 to 24 h post-ovulation to the oviducts of an estrous-synchronized goat (VIVO) and 550 embryos were cultured in G1.3 for 72 h and then moved to G2.3 medium for 96 h and in a humidified atmosphere of 5% CO2, 5% O2, and 90% N2 (IVC). On Day 7, embryos were flushed from the excised tract with a 69.5% recovery rate or removed from culture. Embryos were classified according to IETS criteria with grades and stages recorded. All data were analyzed using the one-way analysis of variance and means were compared using Student's t-test. No differences were seen in the percentage of freezable quality embryos per total recovered between the two groups (34.3% vs. 32.3% for IVC and VIVO, respectively). However, there was a significant difference in the pre-freezing stage between the two culture groups (Stage 5.5 � 0.22 vs. Stage 4.8 � 0.26 for IVC and VIVO, respectively; P < 0.05), but no difference in the quality grade. All embryos greater than Stage 4, Grade 2 were frozen in groups of 5-10 in ethylene glycol with sucrose (Vigro Ethylene Glycol Freeze Plus; Bioniche Animal Health, Belleville, Ontario, Canada) in 0.25-mL straws. After thawing, embryo groups were washed, rehydrated, and incubated in G2.3 as above. Morphology was assessed by assigning grade and stage objectively at 24 h and 48 h post-thaw. Post-thaw viability in vitro was not different between groups (73.4% vs. 72.7% for IVC and VIVO, respectively). The average changes in morphology post-thaw from pre-freezing to 24 h and from 24 h to 48 h within each freezing group were determined. There was no significant difference in the mean change in stage (0.67 � 0.15 vs. 0.82 � 0.17 at 24 h and 0.31 � 0.09 vs. 0.37 � 0.10 at 48 h for IVC and VIVO, respectively) or grade (0.60 � 0.15 vs. 0.41 � 0.17 at 24 h and 0.03 � 0.06 vs. 0.14 � 0.07 at 48 h for IVC and VIVO, respectively) at either observation point. These results suggest that culture of in vitro-fertilized bovine embryos in the caprine reproductive tract did not alter post-thaw development or improve post thaw viability compared to in vitro cultured controls. However, morphological evaluation is too subjective to successfully predict pregnancy rate after transfer; therefore, further study is needed to determine if there are differences in pregnancy rates between these culture methods.

Dissecting why superovulation and embryo transfer usually work on some farms but not on others

Bovine embryo transfer is a well-established commercial industry that is often associated with veterinary practices. Practitioners offering embryo transfer services may possess a very high standard of technical expertise; however, success in the production of embryos and the impregnation of recipients cannot be achieved unless the cattle are healthy and maintained in a well-managed cattle operation. In addition to appropriate gonadotropin treatments of donor cattle, the use of highly fertile semen, known to have been properly stored and handled is required for success. Recipient cattle must be managed with the same attention to detail as donors. Traditionally, PGF has been used for the synchronization of recipients. However, PGF is limited in its effectiveness early and late in the bovine estrus cycle. Recipient estrus synchronization with progesterone releasing intravaginal inserts has been successful and high pregnancy rates have resulted following embryo transfer.

Radiotelemetry temperature responses of mammary gland and body to intramammary injection of Escherichia coli endotoxin or Streptococcus agalactiae in lactating dairy cows

To investigate the feasibility of using changes in body or mammary temperature to detect mastitis, radiotransmitters were implanted midway between rear udder quarters and in the peritoneal cavity of 5 Holstein cows (1 to 3 months in lactation) housed in an environmental chamber (16 +/- 2 C; lights on 7:00 AM to 11:00 PM). After a 6-week control period, Escherichia coli endotoxin (0.5 mg) was injected after the morning milking into left rear teat cisterns via the teat canal. Wisconsin mastitis test score and somatic cell count in all quarters increased significantly (P < 0.01) by the next milking. Effects were greatest in the endotoxin-exposed quarters. Milk yields for all quarters decreased significantly (P < 0.01) by the first milking after endotoxin injection. Udder and body temperatures at milkings were similar and were not affected by treatment. When temperatures were averaged for the 5 cows for each of 120 time points/d, average temperatures, relative to time of injection of endotoxin, were increased by 0.5 C above baseline at 2.75 hours, peaked at +2.9 C at 6.50 hours, and remained high through 9.25 hours after injection. Power spectra calculated for individual cows on a daily basis universally indicated an increase in power at low frequencies on the day of injection. Subsequently, Streptococcus agalactiae (200 colony-forming units) was injected into right rear teat cisterns. Wisconsin mastitis test score increased at the second milking after injection. Cell count and quarter milk yield decreased by the third milking. As with endotoxin, injection of S agalactiae could not be detected via a change in temperature at milkings.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiotelemetry system for continuously monitoring temperature in cows

Deep body temperature is an important index of the physiological status of an animal. A radiotelemetry system was developed to monitor continuously udder and body temperatures in cows under normal housing conditions. Radiotransmitters were crystal controlled blocking oscillators operating in the 27 MHz band. Functionally, the transmitters turned on and off in a pulsatile fashion with temperature encoded as the time interval between two pulses (nominally .5 s at 38 degrees C). Transmitters were powered by lithium batteries (6-mo lifespan) and were encapsulated in paraffin/Elvax (cylinder 6 cm X 3 cm diameter). Signals were detected using a radio receiver in the AM mode. Reception frequency was selected by computer. Each audio pulse was electronically converted to a digital pulse. A PDP 11/23 computer converted intervals between digital pulses to temperature values. As finally configured, the computer collected data from 12 transmitters every 1.4 min (1024 readings/transmitter/d). Temperatures were graphed continuously and stored on magnetic media for future analyses.

Circadian and ultradian temperature rhythms of lactating dairy cows

Thermistors were implanted in the right front quarter of udder and peritoneal cavity of six lactating Holstein cows to investigate whether udder temperature is regulated independently of deep body temperature. Sequential measurements of udder, body, chamber, and outdoor temperatures were every 1.4 min (1024 readings/probe per 24 h) by digital computer. Cows were housed (except for short exercise periods) in a chamber at 16.7 +/- .3 degrees C, lights on 0730 to 1630 and 2100 to 0200 h. Temperature was monitored continuously for 5 days in three cows in early lactation and in three cows in late lactation. Udder temperature was closely correlated with body temperature (body and udder temperatures were 38.8 +/- .1 degree C). Five of six cows showed two patterns of temperature variation: a 24-h pattern with two troughs each day--minimum at 0930 to 1100 h, increase 1.0 degree C by 1200 to 1300 h, decline 1 degree C from 2000 to 2200 h, second minimum by 2100 to 2200 h, and constant elevation from 2300 to 0800 h (peak to trough, 1.23 +/- .09 degrees C); and superimposed upon the 24-h rhythm was an ultradian rhythm with an approximate 90 min period (peak to trough, .5 +/- .03 degrees C). Rhythmicity of udder and body temperatures should be considered in research on the chronobiology of milk secretion and mastitis.