Sperm quality variables of sex-sorted bull semen produced by magnetic-activated cell sorting coupled with recombinant antibodies targeting Y-chromosome-bearing sperm.

The immunological sexing method using antibodies offers cost-effective, high-volume production but faces challenges in terms of X-sperm purity in sexed semen. This research aimed to produce sexed bull semen using highly specific recombinant antibodies in magnetic-activated cell sorting (MACS), evaluate sperm quality and kinematic parameters, and verify the sex ratio of sperm, embryos, and live calves. Fresh semen from two Angus bulls was separated into two equal groups: conventional (CONV) semen and semen sexed using MACS with Y-scFv antibody conjugation to separate two fractions, i.e., the X-enriched and Y-enriched fractions. Then, computer assisted semen analysis and imaging flow cytometry were used to evaluate sperm motility and kinematic variables, acrosomal integrity, sperm viability, and sperm sex ratios. The results showed that sperm motility and quality did not differ between X-enriched and CONV semen. However, the Y-enriched fraction showed significantly lower sperm quality than the X-enriched fraction and CONV semen. The sperm ratio revealed that X-sperm accounted for up to 79.50% of the X-enriched fraction, while Y-sperm accounted for up to 78.56% of the Y-enriched fraction. The sex ratio of embryos was examined using in vitro fertilization. The cleavage rates using CONV and X-enriched semen were significantly higher than that using Y-enriched semen. Accordingly, 88.26% female blastocysts were obtained by using X-enriched semen, and 83.58% male blastocysts were obtained by using Y-enriched semen. In farm trials, 304 cows were subjected to AI using X-enriched and CONV semen. The pregnancy rate did not differ between the X-enriched and CONV semen groups. On the other hand, X-enriched semen generated significantly more live female calves (83.64%) than CONV semen (47.00%). The MACS sexing method significantly enhanced the X-sperm purity in sexed semen, producing high-quality sperm, a high percentage of female blastocytes, and a high percentage of live female calves.

New insights from poly-lactic acid and ionomer films coupled with recombinant antibodies for processing sexed-sorting bovine sperm.

In this study, the efficacy of ionomers and poly-lactic acid (PLA) as an alternative solid material combined with scFv antibodies specific to bovine Y-sperm (Y-scFv) was studied to create a novel method of sexing technology. The coupling efficiency of Y-scFv to the surface of PLA, Na+ and Zn2+ ionomer film was between 2 and 8 mg/mL. Fourier transform infrared spectra confirm that Y-scFv was bound with a carboxylic acid group in each film. Therefore, Na+, Zn2+ ionomers and PLA films conjugated with 4 and 8 mg/mL Y-scFv showed the highest concentration of Y-sperm in the eluted fraction. Considering that the elute fraction was enriched Y-sperm fraction, it contained 67.70-77.94 % of the Y-sperm ratio related to the produced supernatant fraction, which contained up to 69.31-76.01 % enriched X-sperm. In addition, the sperm quality after the sexing process was analyzed by CASA and imaging flow cytometry, which showed that each polymer did not have a negative effect on sperm motility and acrosome integrity for X-sperm. The capacity of ionomer and PLA combined with Y-scFv are used for bovine sperm sexing.

Evaluation of sexed semen-based artificial insemination in Tharparkar cattle under organized farm condition.

Sexed semen facilitates additional female calf production for the expansion of a herd at a faster rate and also curtails the surplus production of unwanted male calves. A study was conducted to evaluate the performance of sexed semen in indigenous Tharparkar cows based on 114 artificial inseminations (AI) performed at natural oestrus using two protocols i.e., single AI (n = 48) and double AI (n = 66). Overall, the first service conception rate (CR) was significantly higher in double (53.0%) than single (33.3%) AI protocol. The odds ratio of conception rate in double AI was 2.26 (χ2 = 4.4, df = 1, p = .04) with respect to single AI. The time that elapsed since the detection of oestrus to insemination was also analysed. In a single AI protocol, the CR was higher (p < .05) at 16 h (54.6%) than insemination at 8 h (27.0%) following the onset of oestrus. Yet, the CR using double AI protocol did not differ (p = .73) significantly when AIs were performed either at 8 h and 24 h (51.9%) or 16 h and 24 h (57.1%) post onset of oestrus. Besides, like the single AI protocol, the parity of the animals also influenced the CR, being higher in heifers (n = 22) than those of parous (n = 92) cows (72.73 vs. 40.43%, χ2 = 7.48, df = 1, p = .006) in the present study. The odds ratio of conception in heifers was 3.93 with respect to parous cows. Overall, the birth of female calf was 91.7%. In conclusion, the present study indicates a future promise of the sexed semen for the production of more female offspring from Tharparkar cattle.

Sex ratio of offspring is not statistically altered following pre-implantation genetic testing under a specific sex selection policy.

PURPOSE: To determine whether the use of pre-implantation genetic testing (PGT) under a specific sex selection policy is associated with alterations in offspring sex ratio. METHODS: This was a single-center retrospective cohort study of singleton live births from January 2018-December 2020 achieved via single blastocyst non-PGT or PGT frozen embryo transfer (FET). Per institutional policy, sex may be disclosed following PGT. If both sexes are available and morphologic grade is similar, patients may select the sex of the embryo to be transferred. Demographics and cycle characteristics were compared between non-PGT vs. PGT cycles with Mann-Whitney U or χ2. Poisson regression with robust variance estimates was used to model the probability of female vs. male offspring among non-PGT vs. PGT cycles, reported as risk ratio (RR) and 95% confidence interval (CI). RESULTS(S): Among 541 live births, 350 (64.7%) were achieved with PGT and 191 (35.3%) without PGT. In both groups, female sex was more common, representing 59.4% of PGT-offspring and 55.0% of non-PGT offspring. After adjusting for potential confounders, the use of PGT was not significantly associated with an increased likelihood of female offspring (RR 1.04, 95% CI 0.98-1.11, p = 0.22). CONCLUSION(S): Singletons born following FET had a higher rate of female sex than male. Allowing sex selection per institutional policy did not increase this ratio. These results contrast with those of prior publications and should motivate individual centers to monitor their own sex ratios. As utilization of PGT increases, local, regional, and national monitoring will become increasingly important.

How does congenital cervicothoracic scoliosis bring about early trunk tilt and coronal imbalance during curve progression: a radiographic analysis to dissect the mechanism of proximal takeoff phenomenon.

PURPOSE: To dissect the mechanism of how congenital cervicothoracic scoliosis (CTS) drive the occurrence of early trunk tilt, namely proximal takeoff phenomenon (PTO) during curve progression. METHODS: CTS patients were stratified into case and control groups according to the presence of PTO. The radiographic deformity parameters of head-neck-shoulder complex were measured and compared between the two groups. The main risk factors for PTO were identified through multiple linear regression analysis. RESULTS: 16 CTS patients with PTO were recruited, and the non-PTO group consisted of 19 CTS patients without PTO. The average Cobb angle was 64.9 ± 19.8° in PTO group and 57.7 ± 21.9° in control group (p > 0.05). Significant difference could be observed for head shift, neck tilt, trunk inclination, apex-C7 deformity angular ratio (DAR), apex translation ratio, C6 tilt, clavicle angle (CA), radiographic shoulder height (RSH), head-neck translation and coronal balance distance (CBD) (All p < 0.05) but not head tilt (p > 0.05). Multiple linear regression analysis revealed that head shift, but not neck tilt correlated significantly with the severity of trunk inclination (β = 0.106, p = 0.003), while apex-C7 DAR and apex translation ratio were the two factors contributing significantly to the severity of head shift (β = 0.620, p = 0.020; β = - 0.371, p = 0.004). CONCLUSIONS: Development and progression of head shift rather than neck tilt is a significant causative factor initiating the occurrence of trunk tilt and proximal takeoff in CTS. A higher apex-C7 DAR representing a short angular upper hemi curve and a lower apex translation ratio representing poor proximal coronal compensation are key risk factors predisposing to head shift.

Biochemical Features of X or Y Chromosome-Bearing Spermatozoa for Sperm Sexing.

This review presents information on biochemical features of spermatozoa bearing X or Y chromosome, enabling production of a sperm fraction with pre-defined sex chromosome. The almost only technology currently used for such separation (called sexing) is based on the fluorescence-activated cell sorting of sperm depending on DNA content. In addition to the applied aspects, this technology made it possible to analyze properties of the isolated populations of spermatozoa bearing X or Y chromosome. In recent years, existence of the differences between these populations at the transcriptome and proteome level have been reported in a number of studies. It is noteworthy that these differences are primarily related to the energy metabolism and flagellar structural proteins. New methods of sperm enrichment with X or Y chromosome cells are based on the differences in motility between the spermatozoa with different sex chromosomes. Sperm sexing is a part of the widespread protocol of artificial insemination of cows with cryopreserved semen, it allows to increase proportion of the offspring with the required sex. In addition, advances in the separation of X and Y spermatozoa may allow this approach to be applied in clinical practice to avoid sex-linked diseases.

Between reproductive rights and sex selection in New Zealand's abortion reforms: practitioner dilemma in institutionalising 'choice' and 'agency'.

In 2020, the New Zealand (NZ) Parliament voted to decriminalise abortion. Although NZ's abortion law formally opposes sex selective abortions, there is considerable complexity in the gender politics of 'choice' and 'agency' in multi-ethnic societies, and interpretations of reproductive rights for ethnic minority women and for the girl child, respectively. This paper explores these complexities through the perspectives of reproductive and maternity care practitioners who are situated at the interface of legal systems, health service provision, and delivery of culturally sensitive care. Thirteen practitioners were interviewed as part of this study. The analysis highlights strains in framings of 'reproductive choice' (underpinned by western liberal notions of rights) and 'gender equality' (abortion rights that acknowledge the complexity of cultural son-preference) for ethnic minority women. These tensions are played out in three aspects of the post-reform landscape: (a) everyday practice and accountability; (b) consumerism and choice; (c) custodianship and gender rights. The findings point to the limitations in operationalising choices for ethnic women in health systems wherein trust deficit prevails, and cultural dynamics render complex responses to abortion. They also highlight reconfigurations of client-expert relationships that may have implications for practitioners' abilities to advocate for ethnic women's rights against cultural influences.

A balancing act: sex selection after pre-implantation genetic testing for aneuploidy for first versus second baby.

STUDY QUESTION: How often do patients undergoing frozen embryo transfer (FET) after preimplantation genetic testing for aneuploidy (PGT-A) choose to select for sex and do sex selection rates differ before and after successful delivery of a first baby? SUMMARY ANSWER: When a choice was available between male and female embryos, patients selected the sex more frequently when trying to conceive the second child (62%) as compared to the first child (32.4%) and most commonly selected for the opposite sex of the first child. WHAT IS KNOWN ALREADY: Sex selection is widely available in US fertility clinics. However, the rate of sex selection for patients undergoing FET after PGT-A is unknown. STUDY DESIGN, SIZE, DURATION: This is a retrospective cohort study of 585 patients that took place between January 2013 and February 2021. PARTICIPANTS/MATERIALS, SETTING, METHODS: The study took place at a single, urban academic fertility center in the USA. Patients were included if they had a live birth after single euploid FET and returned for at least one subsequent euploid FET. The primary outcomes were the rates of sex selection for first versus second baby. Secondary outcomes were rate of selection for same versus opposite sex as first live birth and overall rate of selection for males versus females. MAIN RESULTS AND THE ROLE OF CHANCE: Five hundred and eighty-five patients underwent a total of 1560 single euploid FETs resulting in either one or two live births. A choice between male and female euploid embryos was available for 919 FETs (first child: 67.5% (519/769) versus second child: 50.6% (400/791), P < 0.01). When a choice was available, patients selected the sex more frequently when trying to conceive the second child (first child: 32.4% (168/519) versus second child: 62.0% (248/400), P < 0.01). When sex was selected after first live birth, the opposite sex of the first child was selected 81.8% (203/248 FETs) of the time. Of transfers that involved sex selection, rates of male and female selection were similar for the first child, but selection for females was greater for the second child (first child: 51.2% (86/168) male versus 48.9% (82/168) female, second child: 41.1% (102/248) male versus 58.9% (146/248) female, P < 0.04). LIMITATIONS, REASONS FOR CAUTION: The study was performed at one urban academic medical center in the Northeastern US, which may limit generalizability to other settings where PGT-A may be performed less frequently, or sex selection may be limited or not permitted. In addition, we could not reliably account for whether patients or their partners had prior children and if so, of what sex. WIDER IMPLICATIONS OF THE FINDINGS: Patients undergoing PGT-A with both male and female euploid embryos were more likely to select for sex when attempting a second child and usually selected for the opposite sex of their first child. These findings highlight the potential for family balancing for patients who undergo PGT-A in settings where sex selection is permitted. STUDY FUNDING/COMPETING INTEREST(S): This study received no funding. The authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: N/A.

Characterization of semen type prevalence and allocation in Holstein and Jersey females in the United States.

Our objective was to characterize semen type prevalence and allocation to inseminate US Holstein and Jersey females by year, parity, service number, and herd size. A secondary objective was to identify the prevalence of beef breed sires selected to create beef × Holstein and beef × Jersey crossbred calves. The final data set included 8,244,653 total inseminations of 4,880,752 Holstein females across 9,155 herds, and 435,267 total inseminations of 266,058 Jersey females across 2,759 herds from October 2019 to July 2021. This data set represents approximately 42 and 27% of the total dairy cows and heifers, respectively, across approximately 40% of the total licensed dairy herds in the continental United States. Holstein and Jersey females were inseminated with 1 of 4 semen types: (1) beef, (2) conventional, (3) sexed, or (4) other dairy. The top 4 beef breeds used to produce beef × Holstein and beef × Jersey crossbred calves, respectively, were Angus (55.1 and 39.1%), Limousin (13.9, and 23.5%), Simmental (11.7 and 20.5%), and Crossbreed Beef (11.3 and 4.8%). From 2019 to 2021, the use of sexed semen to inseminate Holstein and Jersey females increased from 11.0 and 24.5% to 17.7 and 32.1%, respectively, and the use of beef semen to inseminate Holstein and Jersey females increased from 18.2 and 11.4% to 26.1 and 21.2%, respectively. The use of beef semen to inseminate Holstein and Jersey females increased with increasing parity and service number, whereas the use of sexed semen decreased with increasing parity and service number supporting that farmers used sexed semen more aggressively in higher fertility and younger females with greater genetic merit. Overall, the increase in sexed and beef semen inseminations was driven primarily by larger herds. In conclusion, sexed and beef semen inseminations in US Holstein and Jersey females increased from 2019 to 2021 and was allocated differentially based on parity and service number. This increase was driven primarily by larger dairy herds possibly due to differences in reproductive performance and economies of scale.

A non-randomized clinical trial to determine the safety and efficacy of a novel sperm sex selection technique.

The desire to have offspring of a specific sex has a long history but has been particularly present with the appearance of assisted reproduction. However, embryo selection raises ethical concerns. Thus, several techniques to select sex-specific spermatozoa have been proposed but carry limitations. There are many variations of each technique, and some are time consuming and costly. Concerns about effectiveness and safety have also rendered many of them unappealing. Therefore, we propose a novel sperm sex selection technique (SST) that appears to be consistently safe and effective. A single-center, non-randomized clinical trial was designed. We included 1,317 couples, who were assigned to one of two groups: ICSI/PGTA or ICSI/PGTA+GS. Ejaculates from male partners of couples in the ICSI/PGTA+GS group (n = 105) were processed using SST to enrich spermatozoa for their desired sex. Standard sperm processing was carried out for couples undergoing PGT-A solely for aneuploidy (n = 1,212), comprising the ICSI/PGTA control group. To validate the efficacy of our technique, we performed an analysis on spermatozoa pre- and post-selection, followed by an assessment of the proportion of the conceptuses' sex to confirm clinical reliability. We also followed up on ICSI clinical outcomes and child/newborn health to establish the safety of our method. Our main outcome measures included the proportion of spermatozoa and embryos enriched for female and male sex, as well as embryo euploidy rates and ICSI clinical outcomes. These outcomes were compared between the two groups. For the ICSI/PGTA group (n = 1,212) (maternal age, 37.0±4yrs; paternal age, 39.1±6yrs), with ejaculated spermatozoa processed in the standard fashion, 2,303 ICSI cycles (1.2±1) yielded an 81.0% (14,375/17,737) fertilization. PGT-A results indicated a euploidy rate of 73.1% (n = 3,718) for female and 72.4% (n = 3,054) for male embryos. These couples achieved a 76.4% (699/915) implantation and 65.2% (597/915) clinical pregnancy rate, with 551 deliveries (48.5% female, 51.5% male). All 105 men in the ICSI/PGTA+GS group had sperm specimens with an equal sex distribution at baseline. Of them, 59 (paternal age, 40.9±6yrs) who desired female offspring obtained an 81.6% enrichment after SST. They underwent 73 ICSI cycles with their partners (maternal age, 37.9±4yrs), achieving a 77.3% (583/754) fertilization. This resulted in 79.1% (231/292) female embryos that generated a 79.3% (23/29) implantation rate, with 16 singleton deliveries of the desired female sex without major or minor congenital malformations. Forty-six couples (maternal age, 37.3±4yrs; paternal age, 40.7±6yrs) desiring male offspring obtained an 80.8% sperm sex enrichment. They underwent 50 ICSI cycles, achieving a 75.4% (462/613) fertilization and equivalent proportion of male embryos (223/280, 79.6%). Their implantation was 90.5% (19/21), with 13 singleton deliveries of healthy male offspring. Furthermore, 78.8% (182/231) of female and 66.4% (148/223) of male embryos from the ICSI/PGTA+GS cohort were euploid. These euploid rates were comparable to those from the ICSI/PGTA group. In couples undergoing ICSI with PGT-A, SST consistently enriched spermatozoa, resulting in a higher proportion of embryos and thus offspring of the desired sex. Moreover, SST did not impair the fertilization or embryo developmental competence of spermatozoa, nor did it affect offspring health. Trial registration: Clinicaltrials.gov NCT05500573.

Sorted Bulls' X-Chromosome-Bearing Spermatozoa Show Increased GAPDHS Activity Correlating with Motility.

Sperm sexing is a technique for spermatozoa sorting into populations enriched with X- or Y-chromosome-bearing cells and is widely used in the dairy industry. Investigation of the characteristics of sorted semen is of practical interest, because it could contribute to the enhancement of sexed semen fertility characteristics, which are currently lower than those of conventional semen. Comparison of a spermatozoa population enriched with X-chromosome-bearing cells to a mixed population is also intriguing in the context of potential differences that drive the mechanisms of primary sex-ratio determination. In this work, sexed (X spermatozoa) and conventional spermatozoa of Holstein bulls were analyzed for the content and enzymatic activity of GAPDHS, a sperm-specific isoform of glyceraldehyde-3-phosphate dehydrogenase that plays a significant role in the regulation of flagellar activity. No difference in the amount of this glycolysis enzyme per cell was revealed, but, notably, GAPDHS enzymatic activity in the sexed samples was significantly higher. Enzymatic activity among the group of sexed but not conventional sperm samples positively correlated with spermatozoa motility, which indicates the significant role of this enzyme for the sorted cells population.

Relationship between the timing of insemination based on estrus detected by the automatic activity monitoring system and conception rates using sex-sorted semen in Holstein dairy cattle.

We investigated the optimal timing of artificial insemination (AI) for achieving pregnancy according to the onset/end of estrus detected by an accelerometer system in Holstein cattle. The conception rates of conventional semen were used as a reference. The conception rate from AI of sex-sorted semen was higher at -4 to 4 h (57.1%) from the end of estrus than those at -12 to -4 h (37.7%) and 12-20 h (30.3%), whereas AI at 4-12 h showed an intermediate conception rate (47.4%). Conversely, conception rates were similar in AI performed between 0 and 32 h from the onset of estrus. Regarding conventional semen, the interval from the onset and end of estrus did not affect conception rates. The present results suggest that the time of the end of estrus is the better indicator of optimal AI timing for sex-sorted semen than the onset of estrus.

Perceptions towards sex selection among Jordanian population: A survey study.

Sex selection is becoming a more common practice in the society and worldwide. The current study aimed to examine the perceptions about sex selection options and possible association with sociodemographic factors and relevant characteristics. The study was a cross-sectional survey of adults in Jordan in January and February 2020 using a self-administered questionnaire. Results showed that 40.1% of respondents preferred male gender when having a child, 22.4% of respondents preferred the male gender when having a child, even if they have had children of both genders, and 71.3% preferred having children from both genders. On the other hand, 58.8% of participants preferred a male gender when there is one chance to conceive via assisted reproduction technologies. Also, among participants, 66% thought that sex selection is religiously acceptable, yet 78.0% did not support of the sex selection idea. The above factors were significantly associated with several sociodemographic variables such as gender, marital status, education, career, and place of residence, but not income. In conclusion, the current study shed a light on preferences towards sex selection in a large cohort to better understand the perception and attitude of the population towards this practice.

Learning to Value Girls: Balanced Infant Sex Ratios at Higher Parental Education in the United States, 1969-2018.

Infant sex ratios that differ from the biological norm provide a measure of gender status inequality that is not susceptible to social desirability bias. Ratios may become less biased with educational expansion through reduced preference for male children. Alternatively, bias could increase with education through more access to sex-selective medical technologies. Using National Vital Statistics data on the population of live births in the United States for 1969-2018, we examine trends in infant sex ratios by parental race/ethnicity, education, and birth parity over five decades. We find son-biased infant sex ratios among Chinese and Asian Indian births that have persisted in recent years, and regressions suggest son-biased ratios among births to Filipino and Japanese mothers with less than a high school education. Infant sex ratios are more balanced at higher levels of maternal education, particularly when both parents are college educated. Results suggest greater equality of gender status with higher education in the United States.

A decade of molecular preimplantation genetic diagnosis of 350 blastomeres for beta-thalassemia combined with HLA typing, aneuploidy screening and sex selection in Iran.

BACKGROUND: Preimplantation genetic diagnosis (PGD) has been developed to detect genetic disorders before pregnancy which is usually done on blastomeres biopsied from 8-cell stage embryos obtained from in vitro fertilization method (IVF). Here we report molecular PGD results for diagnosing of beta thalassemia (beta-thal) which are usually accompanied with evaluating chromosomal aneuploidies, HLA typing and sex selection. METHODS: In this study, haplotype analysis was performed using short tandem repeats (STRs) in a multiplex nested PCR and the causative mutation was detected by Sanger sequencing. RESULTS: We have performed PGDs on 350 blastomeres from 55 carrier couples; 142 blastomeres for beta-thal only, 75 for beta-thal and HLA typing, 76 for beta-thal in combination with sex selection, and 57 for beta-thal and aneuploidy screening. 150 blastomeres were transferable, 15 pregnancies were happened, and 11 babies born. We used 6 markers for beta-thal, 36 for aneuploidy screening, 32 for sex selection, and 35 for HLA typing. To our knowledge combining all these markers together and the number of STR markers are much more than any other studies which have ever done. CONCLUSIONS: PGD is a powerful diagnostic tool for carrier couples who desire to have a healthy child and wish to avoid medical abortion.

Economics of timed artificial insemination with unsorted or sexed semen in a high-producing, pasture-based dairy production system.

This study used a stochastic simulation model to estimate the potential economic benefit of using timed artificial insemination (TAI) in combination with conventional unsorted (TCONV) and sexed (TSEX) semen in heifers only (TCONV-H, TSEX-H) and in both heifers and lactating cows (TCONV-HC, TSEX-HC) in a high-producing, pasture-based production system. The scenarios were compared with a conventional reproductive policy (CONV) in which heifers and cows were inseminated with conventional unsorted semen after estrus detection. Sensitivity analysis was also used to estimate the effect of hormone costs from TAI use on the profitability of each program relative to CONV. The mean annual (± standard deviation) profit advantage (ΔPROF) over CONV for TCONV-H, TCONV-HC, TSEX-H, and TSEX-HC scenarios were €3.90/cow ± 4.65, €34.11/cow ± 25.69, €13.96/cow ± 6.83, and €41.52/cow ± 42.86, respectively. Combined application of both technologies was shown to return a greater annual ΔPROF on average compared with that achievable from TAI alone. However, the risk of not returning a positive annual ΔPROF varied across the scenarios with higher risk in TCONV-H and TSEX-HC. Specifically, TCONV-H and TSEX-HC had a 24 and 18% chance, respectively, of not returning a positive annual ΔPROF. Sensitivity analysis showed that when hormone costs increased by €10/cow TCONV-H and TSEX-HC had a 38 and 23% chance, respectively, of not returning a positive annual ΔPROF. The range in ΔPROF for TCONV policies was most sensitive to the TAI pregnancy rate and TSEX policies were most sensitive to the relative fertility achieved with sexed compared with unsorted semen. This study has shown TAI and sexed semen are complementary technologies that can increase genetic gain and profitability in a pasture-based, dairy production system.

Use of reproductive technology for sex selection for nonmedical reasons: an Ethics Committee opinion.

Because the practice of preimplantation sex selection is ethically controversial, clinics are encouraged to develop and make available their policies regarding its use. Practitioners offering assisted reproductive services are under no ethical obligation to provide or refuse to provide nonmedically-indicated methods of sex selection. This document replaces the document of the same name, last published in 2015.

Applications and world-wide use of sexed semen in cattle.

Successful sorting of sperm based on presence of the X- or Y-chromosome was first reported in the early 1980's with the first live births reported in rabbits in 1988. Subsequent development of technological efficiencies resulted in commercialization of sex-sorted semen to cattle producers in 2003-2005. At product launch, low throughput dictated that reasonable prices to the producer could only be accomplished with extremely low sperm number dosages (2 × 106). Furthermore, conception rates were 70%-75% of those achieved by conventional unsorted product. Refinements in sorting equipment have enhanced the number of sperm that can be sorted from a semen sample and (or) aliquot of time, which translates into reduced production costs, while modifications to other aspects of sperm processing and freezing have facilitated maintenance of a conception potential more similar to that of conventional semen. More recently, strategic use of sex-sorted semen coupled with genomic technologies to identify superior females to satisfy replacement female needs has, by default, led to identification of a population of dairy cows from which replacements are not desired, leading to a tremendous increase in use of beef semen in dairy herds. Though exact numbers are unavailable, estimates indicate sex-sorted semen is rapidly approaching 30% of the total AI market share in North America. Though the primary application of sex-sorted semen is to accelerate genetic progress while enhancing biosecurity through in-house production of replacement animals, numerous other potential applications are evolving or are under consideration.

Exploiting a Y chromosome-linked Cas9 for sex selection and gene drive.

CRISPR-based genetic engineering tools aimed to bias sex ratios, or drive effector genes into animal populations, often integrate the transgenes into autosomal chromosomes. However, in species with heterogametic sex chromsomes (e.g. XY, ZW), sex linkage of endonucleases could be beneficial to drive the expression in a sex-specific manner to produce genetic sexing systems, sex ratio distorters, or even sex-specific gene drives, for example. To explore this possibility, here we develop a transgenic line of Drosophila melanogaster expressing Cas9 from the Y chromosome. We functionally characterize the utility of this strain for both sex selection and gene drive finding it to be quite effective. To explore its utility for population control, we built mathematical models illustrating its dynamics as compared to other state-of-the-art systems designed for both population modification and suppression. Taken together, our results contribute to the development of current CRISPR genetic control tools and demonstrate the utility of using sex-linked Cas9 strains for genetic control of animals.