190 SexedULTRA™, A NEW METHOD OF PROCESSING SEX-SORTED BOVINE SPERM IMPROVES CONCEPTION RATES

Abstract

The gap in fertility between conventional and sex-sorted bovine sperm, known to be on the order of 10 percentage points, has never been bridged, even by increasing the number of sex-sorted sperm per inseminate. A concerted effort in the last few years has resulted in substantial changes in all stages of the sex-sorting process to develop an improved sex-sorted product called SexedULTRA™ (Sexing Technologies, Navasota, TX, USA). In vitro tests show that SexedULTRA™ maintained sperm integrity better than the previous XY method, and field trials were conducted to determine if this translated into improved bovine field fertility. The initial field trial was performed using ejaculates from 8 Holstein bulls located at Select Sires in Plain City (OH, USA). Each ejaculate was split in 2 aliquots that were then processed following the 2 methods (XY method or SexedULTRA™). A total of 6,930 Holstein heifers were inseminated across 41 commercial herds in the United States. Conception rate data were analysed using mixed model ANOVA (JMP 10.0.0; SAS Institute Inc., Cary, NC) with fixed effects of treatment, bull, bull by treatment interaction, and the random effect of herd. Sex-sorted bull sperm following the SexedULTRA™ method resulted in a greater (P < 0.001) conception rate compared with the XY method sperm (45.7 ± 1.7 v. 41.2 ± 1.6%). This is the first report of an improvement in conception rates using sex-sorted bovine semen in a decade since it became commercially available. A second field trial to investigate dose rate effects and compare against conventional semen was performed using 5 dairy bulls located at German Genetics International GmbH in Cloppenburg (Germany). Each ejaculate was split 4 ways, sex-sorted, and frozen in 0.25-mL straws as follows: XY 2.1 million/straw, SexedULTRA™ 2.1 million/straw, SexedULTRA™ 3.0 million/straw, and SexedULTRA™ 4.0 million/straw. A total of 7,855 heifers were inseminated with these sex-sorted straws, whereas 62,398 heifers were inseminated with conventional straws (15 million/straw) produced using contemporary ejaculates from the same bulls. The 56-day nonreturn rate was calculated by sire and treatment combination, and assigned a weight based on the total number of AI for each combination thereof. Table 1 contains the nonreturn rate weighted means and the relative fertility compared to conventional sperm. Data were analysed using a mixed model ANOVA (JMP 10.0.0; SAS Institute Inc.) with treatment and bull as fixed effects. SexedULTRA™ 4.0 sperm presented the greatest (P < 0.001) 56-day nonreturn rate followed by conventional 15.0 (66.73 v. 65.66%); XY 2.1 presented the lowest (P < 0.001) nonreturn rate. This is the first time a dose response effect with sex-sorted bovine sperm and parity in conception rates with conventional semen has been demonstrated. Table 1. Field trial results for number of inseminations, 56-day nonreturn rate (NRR) weighted means, and relative fertility1 compared with conventional sperm

Fertility of fresh and frozen sex-sorted semen in dairy cows and heifers in seasonal-calving pasture-based herds

“…Moreover, SS-FRZ had a better P/AI relative to conventional (>84%) in heifers and lactating cows than found in previous studies (DeJarnette et al, 2009(DeJarnette et al, , 2010(DeJarnette et al, , 2011Chebel et al, 2010;Norman et al, 2010;Sales et al, 2011;Healy et al, 2013;Djedović et al, 2016). To our knowledge, only 2 studies have reported greater P/AI relative to conventional semen (≥90%) than the current study with frozen SS at 2 × 10 6 sperm per straw (Borchersen and Peacock, 2009;Lenz et al, 2016), and both studies were conducted using heifers only. It is important to note, however, that since the current study was conducted, Sexing Technologies Inc.…”

“…Indeed, in some studies, different bulls were used for the SS and conventional treatments (Chebel et al, 2010;Xu, 2014); in others, different ejaculates from the same bull were used (De-Jarnette et al, 2009Norman et al, 2010). A recent trial in Germany (Lenz et al, 2016) aliquotted the ejaculate for the different SS treatments (n = 4), but used different contemporaneous ejaculates for the Figure 3. Effect of bull on pregnancy per AI (P/AI; LSM ± SEM) of lactating cows across the 4 semen treatments (a) and by semen treatment (b).…”

“…has increased the number of sperm in its commercially available SS from 2 × 10 6 to 4 × 10 6 sperm per straw. Nonreturn rates equivalent to conventional semen have been reported in dairy heifers when the sex-sorted sperm dose was increased to 4 × 10 6 sperm per straw (Lenz et al, 2016). Additional split-ejaculate studies are needed to examine the effects of the higher sperm dose in seasonal-calving pasture-based dairy cows and heifers.…”

Bovine sperm sex‐selection technology in Japan

“…Other research indicates that sexed sperm was associated with a lower fertility rate in comparison with unsorted sperm when an equal number of sperm were used, and suggested that a 5‐fold increase in sperm numbers is required to achieve a fertility rate comparable to that of control semen . A recent study reported that the conception rate of a branded sexed semen packaged at 4 million sperm per straw, SexedULTRA 4 M™ developed by STgenetics™, reached that of conventional semen packaged at 15 million per straw . The branded sexed semen is made using improved media during sorting .…”

Bovine Sperm Sexing Alters Sperm Morphokinetics and Subsequent Early Embryonic Development

“…One reason is that the conception rate after the use of sexed-sperm in AI is typically 25% lower across bulls/ inseminations compared to conventional sperm 15,16 . Pregnancy rates are 60 to 80% of the conventional sperm range or higher 17,18 , especially with the use of the recently developed SexedULTRA TM technology which included increasing the number of sperm per insemination from 2 to 4 million 19,20 . However, increasing the number of sexed-sperm per insemination dose is unable to fully compensate and restore the reduced conception rate [20][21][22] .…”