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In the present study, 638 embryo transfers conducted over 3 yr were retrospectively examined to determine which factors (recipient, embryo and transfer) significantly influenced pregnancy and embryo loss rates and to determine how rates could be improved. On Day 7 or 8 after ovulation, embryos (fresh or cooled/transported) were transferred by surgical or nonsurgical techniques into recipients ovulating from 5 to 9 d before transfer. At 12 and 50 d of gestation (Day 0 = day of ovulation), pregnancy rates were 65.7% (419 of 638) and 55.5% (354 of 638). Pregnancy rates on Day 50 were significantly higher for recipients that had excellent to good uterine tone or were graded as "acceptable" during a pretransfer examination, usually performed 5 d after ovulation, versus recipients that had fair to poor uterine tone or were graded "marginally acceptable." Embryonic factors that significantly affected pregnancy rates were morphology grade, diameter and stage of development. The incidence of early embryonic death was 15.5% (65 of 419) from Days 12 to 50. Embryo loss rates were significantly higher in recipients used 7 or 9 d vs 5 or 6 d after ovulation. Embryos with minor morphological changes (Grade 2) resulted in more (P

Summary The physiological effect on the equine respiratory tract of recycled phone book paper vs. sawdust bedding was investigated in 12 mares with no clinical signs of respiratory disease. Mares were housed in a 20-stall barn and randomly assigned to one of two treatment groups (Group 1=sawdust; Group 2=phone book paper) for 14 days. After a 14-day turnout, Group 1 was assigned to phone book paper and Group 2 was assigned to sawdust for 14 days using a crossover experimental design. Endoscopic examinations of the upper respiratory tract and trachea along with tracheal washes (TW) were performed on days 0 and 14 of each trial. Cytologic examinations were performed on TW samples. Cell type and laboratory interpretation of TW samples were noted. There was no difference (P>0.05) in cell type between treatment groups within or across trials. Laboratory interpretation indicated no abnormalities in 30 of 48 TW samples. Stall conditions were visually rated and graded daily for drinking water cleanliness, depth of bedding and absorbency, overall cleanliness, ammonia odor, and aerial ammonia levels. The phone book paper bedding was more absorbent (P

Tremendous progress has been made in the development of assisted reproductive techniques that may enhance the reproductive efficiency of the horse. However, techniques that involve the manipulation of oocytes and/or embryos may themselves be detrimental to embryo viability and subsequent development. Therefore, an objective method of assessing viability of embryos before and/or after oocyte/embryo manipulation is desirable. At this time, morphologic evaluation is the most widely used method of determining the viability of equine embryos. Although morphologic assessment of embryo quality will not always accurately predict the survival of individual embryos, it is very useful for predicting the survival of groups of embryos. Other tests that have been used to evaluate equine embryo viability include (1) development during culture in vitro; (2) quantitating metabolism of the fluorescent substrate fluorescein diacetate; (3) quantitating uptake of the fluorescent stain DAPI; and (4) quantitating embryo metabolism. Although these tests offer potential advantages over morphologic assessment alone, their current limitations have prevented their routine use for embryo evaluation. It is likely that as improvements are made in these evaluation methods, they may offer advantages for use alone or in combination to more accurately assess the viability of equine embryos.