Recipient Organization
UNIV OF THE VIRGIN ISLANDS
(N/A)
ST. CROIX,VI 00850
Performing Department
Agricultural Experiment Station
Non Technical Summary
Semen will be collected from bulls using electroejaculation. Methods to store extended semen at 5 ºC will be evaluated in the lab. Once the best preservation procedure is determined, cooled, liquid semen will be used for artificial insemination to evaluate fertility. Cows estrous cycles will be synchronized using a standard protocol and inseminated transcervically with liquid, cooled semen.
Animal Health Component
60%
Research Effort Categories
Basic
30%
Applied
60%
Developmental
10%
Goals / Objectives
The project will address two objectives to establish a viable liquid semen AI system for use in cattle production in the USVI:Evaluate the in vitro quality of liquid extended semen stored at 5°CEvaluate fertility of liquid-stored semen using artificial insemination (AI)
Project Methods
ProceduresAll procedures in this project will be approved by the UVI Institutional Animal Care and Use Committee prior to initiation of the experiments.Objective 1:Experiments will be conducted using semen collected by electro-ejaculation from bulls at the UVI-AES Beef Cattle Research Facility. All bulls used will be sexually mature (> 20 mo of age) Senepol (n =9). Bulls will be placed in a squeeze chute and semen collected by electro-ejaculation. Semen samples will be evaluated on site for gross motility and volume. Only samples with volume > 3.0 mL and >70% motile sperm (subjective evaluation) will be used for processing. Concentration will be determined in PBS- glutaraldehyde diluted sperm, using a hemocytometer counting chamber. Samples will be maintained at 37°C following initial evaluation, and extended and processed at this temperature.Semen will be extended in two extenders for liquid storage. One extender will consist of 5% egg yolk and 95% skim UHT milk by volume (Wildeus, 2012, 2013; Jacques et al., 2013; Wildeus, 2014; Wildeus and O'Brien, 2016, Wildeus et al., 2017) which has been used successfully in our lab for extending ram semen. This extender is being evaluated because it is easily prepared using off-the-shelf ingredients that a producer would have access to and does not entail a high level of expertise to prepare. A second extender will be a 20% egg yolk and sodium citrate solution (1.856 g sodium citrate/100 mL extender) that is reflective of a commercially used extender for frozen semen storage. Pre-prepared, commercially available extenders (AndroMed and Bovidyl; Minitube USA) will also be utilized following the manufacturer's instructions.No antibiotics will be added to the extender because the extended semen will be cooled and only stored for 96 h. Semen of satisfactory quality (> 3.0 mL volume; >70% motile) will be extended to a final concentration of 2.5 x 106 sperm/mL (resulting in 1.25 x 106 sperm/AI dose) in a one-step dilution with the extender, and packaged into 0.5 ml straws and stored in a water insulated container (37°C) in a Styrofoam box in a refrigerator at 5°C. In-vitro semen analysis of processed semen will be conducted immediately after packaging and at 24, 48, 72 and 96 h after storage. Analysis will include motility and viability (eosin-nigrosin; Jorgensen Labs, CO, USA) immediately after warming to 37°C in a water bath.A second method of cooling the semen will be evaluated using an Equitainer device designed for transporting liquid, cooled equine semen. Samples will be prepared as previously described and placed in the Equitainer for cool down. At 24 h samples will be removed and placed in the refrigerator at 5°C. Samples will be evaluated as previously described at 0, 24, 48, 72 and 96 h post dilution.Temperature data loggers (Stowaway TidBit, Onset Computer Corp, MA, USA) will be used to monitor the temperature in the refrigerator, the Styrofoam box and the Equitainer during the time from sample placement until the final sample evaluation at 96 h.Objective 2:Each year multiparous Senepol cows (n = 20-30) will be synchronized for estrus and timed AI (TAI) using either the 5 or 7-day CO-Synch + CIDR protocol. The remaining cows (n = 20-30) in the herd will not be synchronized prior to breeding and be bred by natural service (NS).The TAI cows will be inseminated with semen collected, evaluated, extended and stored according to the results obtained under Objective 1. Bulls to be used will be the ones that are selected for natural breeding that year based on performance and pedigree. Cows will be synchronized so that AI takes place at the start of the breeding season in June. One week after AI the TAI cows will be placed in breeding groups on pasture with the same bulls they were bred to by AI. The NS cows will be paced with the bulls on pasture on the day that the TAI group is inseminated.Inseminations will be carried out using standard AI procedure and equipment by one or two trained inseminators with equal representation across bulls and days. Semen will be transported from the on-campus lab to the UVI-AES Beef Cattle Research Facility in an insulated container at the cooled temperature and warmed to 37°C prior to insemination.Fertility to AI, measured as conception and pregnancy, will be evaluated by transrectal ultrasound at 30-45 d post-AI, transrectal palpation at weaning and confirmed at calving.