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During a 2-year study, yearling beef bulls were used to determine the effects of grazing on endophyte-infected tall fescue on endocrine profiles, semen quality and fertilisation potential. Bulls were allotted to graze tall fescue pastures infected with Neotyphodium coenophialum (E+; n = 20 per year) or Jesup/MaxQ (Pennington Seed, Atlanta, GA, USA; NTE; n = 10 per year). Bulls were grouped by scrotal circumference (SC), bodyweight (BW), breed composites and age to graze tall fescue pastures from mid-November until the end of June (within each year). Blood samples, BW, SC and rectal temperatures (RT) were collected every 14 days. Semen was collected from bulls every 60 days by electroejaculation and evaluated for motility and morphology. The developmental competence of oocytes fertilised in vitro with semen from respective treatments was determined. Bulls grazing E+ pastures had decreased BW gain (P < 0.01), increased overall RT (P < 0.01) and decreased prolactin (P < 0.01) compared with animals grazing NTE pastures. Neither percentage of normal sperm morphology nor motility differed between bulls grazed on the two pasture types. Semen from E+ bulls demonstrated decreased cleavage rates (P = 0.02) compared with semen from NTE bulls. However, development of cleaved embryos to the eight-cell and blastocyst stages did not differ between the two groups. In conclusion, semen from bulls grazing E+ tall fescue resulted in decreased cleavage rates in vitro, which may lower reproductive performance owing to reduced fertilisation ability.

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Hormonal estrus synchronization followed by heat detection of recipient animals is a widely used technique in embryo transfer (ET) programs around the world. However, the successful outcomes of ET rely heavily on appropriate heat detection of recipient animals. Additionally, limited availability of personnel and time to detect heat makes ET impractical at times. Therefore, pregnancy rates (PR) following a timed embryo transfer (TET) program were evaluated taking into account different variables of recipient cows, donor embryos, and season of transfer under field conditions in Argentina. Recipient cows were synchronized utilizing a progesterone (P4) intravaginal device (DIB, Syntex, Argentina) for 7 days. On Day 0 (day of DIB insertion) 2 mg of estradiol benzoate (EB) i.m. was administered and immediately after DIB removal on Day 7, 500 μg of D(+) Cloprostenol i.m. (PG, Ciclase, Syntex), 400 IU of eCG i.m. (Novormon, Syntex) plus 1 mg of cypionate estradiol i.m. (ECP; König, Agentina) were administered to all recipient cows. Fresh (n = 1746) and frozen (n = 2047) beef bovine embryos were nonsurgically transferred into recipient cows on Day 9 after PG. The effects of body condition score (1–9, BCS I: ≤5, n = 804 and BCS II: ≥6, n = 2989), corpus luteum (CL) score (CL1: prominent papilla, n = 932, CL2: small papilla, n = 2028, and CL3: asymmetric, n = 833), location of embryo placement in uterine horn (upper, n = 3566, and lower, n = 227), and type of recipient such as heifer (n = 487), lactating (n = 1010), or dry cows (n = 2296) on PR were evaluated. Additionally, stage of embryo development (4–7), quality (1–3), and season of transfer (spring, summer, fall, and winter) were included in the analysis. Pregnancy rate was confirmed by rectal palpation 60 days after ET. Data were first screened by chi square and then analyzed by Proc Logistic of SAS (SAS Institute Inc., Cary, NC). Overall PR was 54.7%. body condition score, CL, type of recipients, stage of embryo development, and year were not significantly (P > 0.05) associated with PR. As expected, cows that received direct fresh embryos had 1.49 times greater odds of conceiving (odds ratio, OR = 1.49, 95% CI: 1.22 to 1.82) than those receiving frozen embryos. Additionally, cows receiving embryos graded as quality 1 had greater probability to conceive (OR = 1.62, 95% CI: 1.34 to 1.95, or OR = 1.64, 95% CI: 1.25 to 2.21) compared to quality 2 or 3 respectively. Moreover, embryos placed into the upper portion of uterine horn were more likely (OR = 1.48) to conceive than those placed in the lower uterine portion. Regardless of embryos and recipient cow variables analyzed, there was a greater probability for cows to conceive during winter (OR = 1.41, 95% CI: 1.13 to 1.95) as compared with summer. In conclusion, synchronized recipient animals for a TET program resulted in acceptable PR for both fresh and frozen embryos. Results suggested that the quality and location of embryos (upper portion) in uterine horn were the most important variables associated with PR in recipient cows. Therefore, TET is a viable and practical option allowing a successful outcome for many beef operations where availability of personnel is limited.