The objective was to evaluate the reproductive performance of frozen sex-sorted sperm at 4 × 10 6 sperm per dose (SexedULTRA 4M, Sexing Technologies, Navasota, TX) relative to frozen conventional sperm in seasonal-calving pasture-based dairy cows. Semen from Holstein-Friesian (n = 8) and Jersey (n = 2) bulls was used. Four of the Holstein bulls used were resident at or near a sex-sorting laboratory (Cogent, UK, or ST Benelux, the Netherlands). The remaining 6 bulls were located at studs in Ireland. For these 6 bulls, ejaculates were collected, diluted with transport medium, and couriered to Cogent in parcel shippers. Transit time from ejaculation to arrival at the sorting laboratory was 6 to 7 h. For all bulls, ejaculates were split and processed to provide frozen conventional sperm (CONV) at 15 × 10 6 sperm per straw and frozen sex-sorted (SS) sperm at 4 × 10 6 sperm per straw and used to inseminate lactating dairy cows after spontaneous estrus. Pregnancy diagnosis was performed by ultrasound scanning (n = 7,246 records available for analysis). Generalized linear mixed models were used to examine effects on pregnancy per AI (P/AI) at first artificial insemination, with sperm treatment (CONV vs. SS), bull (n = 10), and treatment × bull interaction as the fixed effects, and herd (n = 142) as a random effect. Overall, P/ AI was greater for cows inseminated with CONV than for those inseminated with SS (59.9% vs. 45.5%; 76.0% relative to CONV). This study was not designed to compare resident bulls vs. shipped ejaculates, but the magnitude of the difference between P/AI achieved by CONV and SS was apparently less for resident bulls (60.3% vs. 50.2%) than for shipped ejaculates (58.6% vs. 40.7%). We discovered a treatment × bull interaction for shipped ejaculates (P/AI ranged from 45 to 86% relative to CONV) but not for the resident bulls (P/AI ranged from 81 to 87% relative to CONV). Relative P/AI of SS compared with CONV was greater in cows with high or average fertility potential (76.1% and 78.3%, respectively) than in cows with low fertility potential (58.1%). In 33.1% of the enrolled herds, the P/AI achieved with SS was 90% or more of the P/ AI achieved with CONV; this was mainly explained by herds in which SS performed exceptionally well but CONV performed poorly. In conclusion, SS had lower overall P/AI compared with CONV; however, P/AI achieved with SS was dependent on the bull, fertility potential of the cow, and herd. Strategies to improve the P/AI with SS in seasonal-calving pasture-based lactating dairy cows require further research.

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The aims of this study were (i) to investigate changes in the global transcriptome of bovine endometrial explants induced by exposure to blastocysts, (ii) to investigate if male and female blastocysts elicit a differential response in the endometrial transcriptome in vitro and (iii) to determine whether bovine endometrium responds to the presence of murine embryos. In Experiment 1, endometrial explants from the same uterus were cultured for 6 h with or without 20 in vitro-produced bovine blastocysts. In Experiment 2, endometrial explants were cultured with male or female bovine blastocysts produced in vitro by IVF either using sex-sorted semen or conventional unsorted semen followed by embryo sexing based on a biopsy. In Experiment 3, endometrial explants were cultured alone or in the presence of bovine blastocysts (n = 25) or murine blastocysts (n = 25). Following culture, explants were snap frozen and stored at −80°C until RNA extraction, qPCR or RNA-Seq. Culture with bovine blastocysts increased endometrial expression of 40 transcripts, all of which were interferon-tau induced. Culture with male or female bovine blastocysts increased transcript abundance of five classic interferon-stimulated genes (MX1, MX2, ISG15, OASY1, RSAD2) in explants; however, there was no difference in abundance of transcripts previously reported to be related to embryonic sex (IFNAR1, IFNAR2, CTGF, ARTN, SLC2A1, SLC2A5). Exposure to murine blastocysts did not elicit any detectable change in transcript abundance. These findings, coupled with our previous data, indicate that very local, interferon-tau-induced changes in endometrial gene expression occur in response to blastocysts; whether such changes play any role in subsequent pregnancy recognition remains to be established.