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This study compares two methods for seminal plasma removal by evaluating sperm recovery rates, and motility and morphology of cooled-stored semen. Ejaculates were divided into three groups: control, filtration and cushioned centrifugation. Semen was extended to 25 million sperm/ml using a skim-milk-based extender and stored at 5°C for all groups. Sperm motility (total motility (%TM) and progressive motility (%PM)) was determined at 0, 24, 48 and 72 hours by a computer-assisted sperm analyser. Sperm morphology was assessed using differential interference microscopy. Overall, %TM of the centrifugation group was significantly higher than the filter group, but not significantly different than the control. No significant difference in %TM or %PM was detected for the control group and filter. Cushioned centrifugation was a superior method to obtain progressively motile sperm compared with control (P=0.03) and filter groups (P<0.001). No significant difference was found for the per cent of normal sperm cells and detached heads between the groups. This study demonstrated that cushioned centrifugation was a superior method to remove seminal plasma while preserving %TM and enhancing %PM for stallions under cooled storage over three days. However, as the differences appear to be negligible, the SpermFilter may represent an alternative for farms lacking a centrifuge.

SummaryReasons for performing study: Mares diagnosed with twin vesicles at 13-17 days after ovulation commonly have one of 2 vesicles manually reduced. It is not known whether vesicle location (adjacent vs. nonadjacent), mare age, mare reproductive status, parity, month of breeding or mare plasma progesterone concentration affects live foal rates. Objectives: To determine factors associated with a positive outcome (live foal) in mares undergoing manual twin reduction between 13 and 17 days post ovulation when performed by a single operator. Study design: Retrospective case-control study. Methods: Breeding records and the Jockey Club records of registered Thoroughbreds were used to evaluate factors affecting the outcome of pregnancies in mares undergoing twin elimination and mares with singleton pregnancies. Thoroughbred mares with twin pregnancies (n = 129) were matched by age, parity, farm location and month bred with mares diagnosed with a singleton pregnancy (n = 127). The effects of location of embryonic vesicles, mare age, reproductive status, parity, month of breeding, vesicle size and plasma progesterone concentration at pregnancy diagnosis on live foal rate were examined. Results: Position of embryonic vesicles at time of manual elimination, parity and month bred had no effect on live foal rate. Live foal rates in mares >9 years of age were lower (71.8%) than in all mares Յ9 years (87.1%; P<0.05). Mares >9 years of age that had a twin reduced lost more pregnancies (34.8%) than age-matched control mares (20.0%; P<0.005). Mean plasma progesterone concentration of twin-reduced mares was greater than in control mares when compared on the same day post ovulation. Plasma progesterone concentrations did not differ between mares that lost their pregnancy and those that delivered a live foal. Conclusions: Mare age of >9 years is associated with decreased pregnancy rate after twin reduction. Potential relevance: Furthering the understanding of factors that affect live foal outcome following manual twin elimination in mares.

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