118 A comparison of intravaginal progesterone devices for fixed-time artificial insemination in beef cattle

Intravaginal progesterone (P4) devices used for ovarian synchronization before fixed-time AI (FTAI) differ in drug release, which may influence fertility outcome. A 2×2 study was designed to determine the effects of different intravaginal devices (PRID Delta, 1.55g of P4 vs. CIDR, 1.38g of P4) and parity (heifers vs. cows) on follicular dynamics, expression of oestrus, and pregnancy per AI (P/AI). At random stages of the oestrous cycle, nulliparous beef heifers and lactating cows were given 100µg of gonadorelin (gonadotrophin-releasing hormone, GnRH) intramuscularly (IM) and assigned randomly to either the PRID (n=76 heifers, 76 multiparous, 27 primiparous) or CIDR (n=76 heifers, 73 multiparous, 32 primiparous) group. Devices were removed 5 days later, an oestrus-detection patch was applied just cranial to the tail head, and 500µg of cloprostenol was given IM at the time of device removal and again 24h later. At 72h after device removal, cattle were inseminated and given 100µg of GnRH IM. Transrectal ultrasonography was used to determine the diameter of the largest follicle on the day of device removal and at FTAI, ovulation time, and pregnancy status 30 days after FTAI. A colour change of ≥50% of the oestrus-detection patch at FTAI was taken as expression of oestrus. Data were compared among groups by 2-way ANOVA using MIXED and GLIMMIX procedures. There were no interactions between P4 device and parity for any endpoint. The diameter of the largest follicle (mean±s.e.m.) was not different between PRID and CIDR groups on either the day of device removal (10.6±0.1 vs. 10.9±0.1mm) or the day of FTAI (13.7±0.1 vs. 13.9±0.1mm). The proportion displaying oestrus did not differ between P4 device groups, but was greater in heifers than in cows [121/152 (79.6%) vs. 135/207 (65.2%); P<0.01], and the interval from FTAI to ovulation was shorter in heifers than in cows (27.8±1.2 vs. 32.0±1.1 h; P=0.01). The P/AI was not different between P4 device groups or parity groups (overall 67.0%, 238/355). However, among lactating cows, the P/AI tended to be greater in the PRID vs. CIDR group [75/102 (73.5%) vs. 64/105 (61.0%); P=0.10], and was greater in multiparous vs. primiparous cows [106/148 (71.6%) vs. 33/59 (55.9%); P=0.04]. Among cattle that displayed oestrus, the P/AI tended to be greater in the PRID vs. CIDR group [92/123 (74.8%) vs. 85/131 (64.9%); P=0.09]. Among lactating cows that displayed oestrus, the P/AI was greater in multiparous vs. primiparous cows [74/94 (78.2%) vs. 24/42 (57.1%); P<0.01]. In summary, follicular dynamics and expression of oestrus did not differ between PRID and CIDR groups, but the P/AI tended to be greater in PRID-treated lactating cows and in cattle that displayed oestrus. This research was supported by CEVA Animal Health, Saskatchewan ADF, Agriculture and Agri-Foods Canada, and Rockway Inc.

27 Cryopreservation of bovine semen using cell-permeating antioxidant and protein-free extender

Effective semen extenders are those with defined composition that promote sperm longevity. Generation of reactive oxygen species during semen cryopreservation results in sperm membrane lipid peroxidation and reduced longevity. Recent studies demonstrated that small cell permeating dimethyl tyrosine conjugated peptides, such as SS-31, translocate to the mitochondria and scavenge excess reactive oxygen species. The present study was conducted to test the hypothesis that the addition of SS-31 improves the post-thaw quality and fertility potential of bovine semen. The effect of SS-31 was tested in combination with two extenders: (1) conventional tris-egg yolk-glycerol (TEYG, control) and (2) cholesterol-cyclodextrin+tris-glycerol (CC+TG, a defined protein-free extender). Fifteen ejaculates were collected from 5 Black Angus bulls. Ejaculates were diluted to 400×106 spermmL−1 with tris-citric acid buffer, and treated with 0, 50, or 100 µmolmL−1 SS-31 for 15min at 32°C. Semen aliquots were diluted further with TEYG, 0.5mgmL−1 CC+TG, or 1mgmL−1 CC+TG extender to a final concentration of 50×106 spermmL−1. Semen was then cooled to 4°C and frozen in a programmable freezer. Post-thaw sperm motion parameters were evaluated at 0, 2, 4, 6 and 24h with CASA. Semen fertility was determined by fixed-time AI using Hereford-cross cows (n=100). Synchronized cows were inseminated once with semen extended in TEYG, 1mgmL−1 CC+TG, or 1mgmL−1 CC+TG + 100 µmolmL−1 SS-31. Pregnancy was diagnosed by ultrasonography at 27 days post-insemination. Post-thaw sperm motion parameters were compared by ANOVA for repeated-measures, and pregnancy rates were compared using binomial linear mixed-model ANOVA. No differences in sperm motion parameters were detected among SS-31 treatments within extenders. Semen extended in TEYG or 1mgmL−1 CC+TG had greater total and progressive motilities at 0 and 2h post-thaw than semen extended in 0.5mgmL−1 CC+TG (P<0.05). Pregnancy rates after fixed-time insemination did not differ among semen extender groups [TEYG: 15/25 (60%), 1mgmL−1 CC+TG: 19/34 (56%), 100 µmolmL−1 SS-31+1mgmL−1 CC+TG: 21/37 (57%)]. Addition of the cell permeating antioxidant SS-31 did not improve post-thaw semen quality or fertility. The CC+TG extender was as robust as conventional egg yolk extender in protecting bovine sperm during cryopreservation. This research was supported by NSERC Canada, the Government of Saskatchewan, and Agriculture and Agri-Food Canada.

133 In Vitro Embryo Production from Oocytes Collected from Non-Supertimulated Wood Bison (Bison bison athabascae) Following Maturation In Vitro Using Portable Incubators

This study was done to determine the feasibility of in vitro embryo production in wood bison during the anovulatory season, without ovarian superstimulation or follicle wave synchronization, to simulate collection conditions in a wild or field setting. The experiment provided the opportunity to compare embryo development using 2 different maturation media and incubator systems. The cumulus-oocyte complexes (COC) were collected by transvaginal ultrasound-guided follicle aspiration during May from non-superstimulated bison. Compact COC were allocated to 2 groups and matured in standard maturation medium using a portable gassed incubator, or in commercial medium using a portable non-gassed incubator. In the former (Standard), the COC were placed in a round-bottomed tube containing TCM-199 medium with 5% calf serum, 5 μg mL−1 LH, 0.5 μg mL−1 FSH, and 0.05 μg mL−1 gentamicin, and the tube was placed in a portable incubator with 5% CO2. In the latter (Commercial), COC were placed in a round-bottom tube containing the commercial medium (Boviteq, Saint-Hyacinthe, QC, Canada), and placed in a portable incubator without CO2. After 24 h of maturation, oocytes were fertilized in vitro (Day 0) in Brackett-Oliphant medium at 38.5°C in a conventional incubator with 5% CO2 humidified atmosphere. Presumptive zygotes were cultured in CR1aa plus 5% calf serum, at 38.5°C and in 5% CO2, 5% O2, and 90% N2 and high humidity. Cleavage was recorded on Day 3 and embryo development was recorded on Day 7. Cleavage and transferable embryo rates (calculated from the total number of oocytes submitted to IVF) were compared between groups by chi-squared test. No difference in cleavage rates was observed between Standard and Commercial treatment groups [68.1 (32/47) v. 79.2% (57/72), respectively; P = 0.25], nor in morula plus blastocyst rates on Day 7 (36.2 v. 45.8%, respectively; P = 0.39). However, the rate of transferable embryos (grade 1 and grade 2) on Day 7 was higher in the Commercial group (38.9 v. 12.8%; P < 0.01). Of the COC in the Commercial group, a higher number of morula plus blastocyst were observed to be compact good COC (>3 layers of cumulus cells) than compact regular COC (1-3 layers of cumulus cells) (66.7 v. 31.0% respectively; P < 0.05), along with a higher number of transferable embryos on Day 7 (60.0 v. 23.8%, respectively; P < 0.05). In conclusion, wood bison oocytes collected during the anovulatory season from non-superstimulated, non-synchronized bison and matured in vitro using portable incubators were competent to develop to the morula and blastocyst stages following IVF and culture. These results are important for future plans that require transporting oocytes from remote collection sites to the IVF laboratory, particularly with respect to the effectiveness of commercial maturation media which does not require CO2 supplementation. Research was supported by the Natural Sciences and Engineering Research Council of Canada.

3 Animal Protein-Free Semen Extender for Fixed-Time Insemination of Beef Cows

Current semen cryopreservation protocols include the use of animal products, such as egg yolk, in semen extenders, which raises important biosecurity concerns related to the transmission of infectious agents. Therefore, there is a need for alternatives to animal proteins in semen extenders. Cholesterol-cyclodextrin (CC) has been used as an adjunct in semen extenders to facilitate the delivery of exogenous cholesterol into sperm plasma membranes. The purpose of this study was to determine the fertility potential of semen extended with cholesterol of plant origin (PhytoChol, Wilshire Technologies, NJ, USA) in a fixed-time insemination program for beef cows. Semen was collected by electroejaculation from mature Simmentals bulls (n = 4 bulls, 4 replicates/bull) and analysed using computer-assisted semen analysis (CASA). Ejaculates from different bulls with ≥200 × 106 sperm mL−1 and ≥60% total motility were pooled. The pooled ejaculates were distributed into 3 treatments and diluted to 50 × 106 mL−1 in Tris-citric-acid base extenders containing either egg yolk (20% vol/vol egg yolk, control), 0.5 mg of CC per mL of semen, or 1.0 mg of CC per mL of semen. Glycerol (7% vol/vol) was added to each extender. Extended semen was loaded into 0.5-mL straws and frozen to –196°C. Post-thaw sperm motility was analysed using CASA. Ovulation was synchronized among multiparous beef cows using 1 of 3 protocols: (1) 5-day intravaginal progesterone-releasing device (PRID) and prostaglandin F2α PGF2α) treatment on the day of PRID removal (n = 37 on random days of cycle); (2) oestradiol + progesterone treatment and 7-day PRID followed by PGF2α on the day of PRID removal (n = 37 on random days of cycle); or (3) PGF2α alone (n = 19 on Day 7 to 9 from ovulation). Cows were treated with gonadotropin-releasing hormone (GnRH) and assigned randomly to be inseminated with 1 of the 3 semen treatments 72 h after PGF2α treatment. Ovulations were confirmed and pregnancies were diagnosed 28 to 35 days after insemination by ultrasonography. Post-thaw sperm motility was compared among extenders by analysis of variance. Pregnancy rates were compared among groups by generalized linear mixed model. Total motility (52 ± 3%, 59 ± 3%, and 62 ± 7%) and progressive motility (47 ± 3%, 54 ± 3%, and 58 ± 6%) did not differ among the egg yolk, 0.5 mg CC, and 1.0 mg CC extenders, respectively. There were no differences in pregnancy rates among synchronization groups; therefore, data were combined to compare the effects of semen extender. Four cows were excluded due to improper synchronization treatment. Pregnancy rates of cows inseminated with egg yolk (n = 31), 0.5 mg CC (n = 31), and 1.0 mg CC (n = 27) semen were 32, 74, and 52%, respectively (P < 0.05). Fertility in cattle inseminated using semen extended with cholesterol of plant origin has not been previously reported. We conclude that plant cholesterol may be used to replace animal proteins (egg yolk or milk origin) in bovine semen cryopreservation. Research supported by grants from the Saskatchewan Agricultural Development Fund, Agriculture and Agri-Food Canada, and Alberta Livestock and Meat Agency.

39 FERTILITY POTENTIAL OF FROZEN-THAWED WOOD BISON SEMEN USING EXTENDER WITHOUT EXOGENOUS PROTEIN

Cryopreservation of semen free of infectious agents is critical for the recovery and preservation of genetic diversity in Canada’s threatened wood bison populations. Egg yolk is a common constituent of conventional semen extenders, but it raises biosafety concerns related to transmission of infectious agents. The purpose of this experiment was to determine the fertility potential, both in vitro and in vivo, of semen frozen without the use of exogenous protein but with addition of cholesterol loaded cyclodextrin (CLC). Semen was collected by electro ejaculation from 4 wood bison bulls. Fresh sperm total motility and concentration were analysed using a computer-assisted sperm analyzer. Ejaculates with total sperm motility of >60% and a concentration of >200 × 106 sperm mL–1 were selected and pooled among bulls. For the control group, pooled semen was diluted to 50 × 106 sperm mL–1 with conventional extender containing 20% egg yolk and 7% glycerol. For the test group, pooled semen was diluted to 100 × 106 sperm mL–1 in Tris-citric acid buffer and incubated with 2 mg mL–1 CLC for 15 min before 1 : 1 dilution with 14% glycerol extender. Extended semen was placed in 0.5-mL straws, cooled, and frozen. Post-thaw motility analysis was conducted using a computer-assisted sperm analyzer, and the 2 collections with highest post-thaw motility were selected for fertility testing. Heterologous IVF was conducted using bovine oocytes obtained from an abattoir. After 20 to 22 h of in vitro maturation, the cumulus-oocyte complexes were placed into drops with either control or test semen. After 18 h, potential zygotes were denuded and moved to culture media. Cleavage and blastocyst rates were assessed on Day 4 and 8, respectively, from oocyte collection. The fertility potential of the semen was also tested in vivo using synchronized wood bison cows. At 24 h after hCG treatment, bison cows were assigned randomly to 2 groups and inseminated twice, 12 h apart, with frozen-thawed control semen (n = 23) or test semen (n = 23). Pregnancy was assessed 34 to 36 days after insemination by transrectal ultrasonography. Total sperm motility (mean ± standard error of the mean) of fresh semen was 80.2 ± 3.3%. The post-thaw motility was 41.7 ± 2.9% and 44.6 ± 3.3% for control and test semen, respectively. The cleavage rates of bovine oocytes fertilized in vitro with bison semen from the control group (n = 278) and test group (n = 299) were 49.9 ± 2.1% and 41.3 ± 4.5%, respectively, and the blastocyst rates were 17.7 ± 1.7% and 17.3 ± 2.5%, respectively. Pregnancy rates of wood bison artificially inseminated with control and test semen were 39 and 0%, respectively. In conclusion, wood bison semen frozen with CLC (without exogenous protein) resulted in post-thaw motility and in vitro fertility potential comparable to that of conventional egg yolk extender. However, CLC semen failed to fertilize in vivo, perhaps because of disruption of the processes of capacitation. The dichotomy between in vivo and in vitro results was surprising. It may be necessary to exercise caution when using IVF as a tool to assess fertility in vivo.

122 TIMED ARTIFICIAL INSEMINATION IN WOOD BISON USING FROZEN-THAWED SEMEN

Recent progress with methods to control ovulation and semen cryopreservation in Wood Bison was the impetus to test the feasibility of timed AI to facilitate reclamation of this threatened species. A 2 × 2 design was used to compare the efficacy of 2 ovulation synchronization techniques and 2 semen cryopreservation protocols. Female Wood Bison were assigned randomly to 2 groups (n = 24/group) in which ovarian synchronization was induced by ultrasound-guided ablation of follicles >5 mm or intramuscular treatment with 2.5 mg of estradiol 17B + 50 mg of progesterone (E+P) in canola oil. A progesterone-releasing intravaginal device (PRID) was placed at the time of follicle ablation (for 5 days) or E+P treatment (for 8 days) in the respective groups. A luteolytic dose of prostaglandin was given at the time of PRID removal, and 2500 IU of hCG was given IM 3 days later. Bison were inseminated 24 and 36 h after hCG treatment using frozen-thawed semen. The semen was collected by electro-ejaculation from 4 Wood Bison bulls, pooled, and divided into aliquots diluted in either egg-yolk extender (EY) or cholesterol-loaded cyclodextrin extender (CLC). Half the bison in each synchronization group were inseminated with either EY- or CLC-extended semen. Bison were examined by ultrasonography every 12 h beginning on the day of hCG treatment for 3 days or until ovulation was detected, whichever occurred first. Pregnancy diagnosis was made by ultrasonography 34–36 days after insemination. Two bison were excluded during the experiment because of handling difficulty; therefore, the total number of bison used was 46. Ovulation rate and interval to ovulation were compared between synchronization groups by chi-square and t-test, respectively. Pregnancy rates were compared among groups by 2-way ANOVA after transforming data to arcsin. The ovulation rate was not different between synchronization groups [combined mean, 37/46 (80%)], nor was the degree of synchrony, as assessed by the residuals (variation from the mean) in the respective groups. However, the diameter (mean ± standard error of the mean) of the dominant follicle at the time of hCG treatment was smaller in the follicle ablation group than in the E+P group (10.5 ± 0.6 v. 13.9 ± 0.6; P < 0.04), and the interval from hCG treatment to ovulation tended to be longer (35.3 ± 1.6 v. 31.8 ± 1.3 h; P ≤ 0.10). Pregnancy rate was not affected by synchronization procedure, but pregnancy was detected only in the EY-inseminated group (9/23 v. 0/23; P < 0.01). Despite that post-thaw sperm motility was similar for EY and CLC semen (41.7 ± 2.9 and 44.6 ± 3.3%; respectively), CLC-treated semen failed to impregnate bison in vivo. We concluded that synchronization and timed insemination with frozen-thawed semen is feasible in Wood Bison. Of the 23 bison inseminated with EY-extended semen, 21 ovulated (91%), and of those that ovulated 9 became pregnant (43%). Both synchronization schemes were effective, but the ablation protocol may be improved by an additional day between ablation and hCG treatment. We thank Vetoquinol Canada and Merck Animal Health for providing hormone treatments.

183 IN VITRO EMBRYO PRODUCTION: A TOOL TO PRESERVE THE THREATENED WOOD BISON (BISON BISON ATHABASCAE)

In vitro embryo production is being developed as a tool to restore genetic diversity and eliminate endemic disease in wood bison. In a recent study in wood bison, we found that more oocytes reached maturity after 30 h v. 24 h of in vivo maturation following hCG treatment (Cervantes et al. 2014 Reprod. Fertil. Dev. 26, 199). An additional 4 h of in vitro maturation after an in vivo maturation period of 30 h also had a positive effect on developmental competence. The present study was designed to test the hypothesis that extending the in vivo maturation time (i.e. extending the interval between hCG treatment and cumulus-oocyte complex (COC) collection) from 30 to 34 h will improve in vitro embryo production in wood bison. Follicular wave development was synchronised among female wood bison (n = 28, 6 to 10 years old) by transvaginal follicular ablation. The study was done in 4 replicates (n = 7 bison per replicate). Bison were given FSH 1 day (300 mg) and 3 days (100 mg) after ablation for ovarian superstimulation, and hCG (2500 IU) 5 days after ablation to induce COC maturation in vivo. Bison were divided randomly into 2 groups (n = 14/group) in which COC were collected transvaginally at either 30 h or 34 h after hCG treatment. Expanded COC from the 30 h group were fertilised after 4 h of in vitro maturation, while expanded COC from the 34 h group were fertilised immediately. Oocytes and sperm were co-incubated (Day 0 = day of fertilization) for 18 h at 38.5°C in 5% CO2 in air and high humidity. Presumptive zygotes were cultured in 4-well dishes containing 500 μL well–1 of CR1aa medium at 38.5°C, 5% CO2, 5% O2, 90% N2 and high humidity, and assessed on Days 3, 7, and 8 (Day 0 = day of fertilization). Data were compared between groups by Chi-squared analysis. No effect of replicate was found. Compared to the 30 h group, the 34 h group had a greater cleavage rate [55/74 (74%) v. 49/86 (57%); (P < 0.05)], and a greater blastocyst rate on Day 7 [25/74 (34%) v. 9/86 (10%); (P < 0.05)] and Day 8 [(40/74 (54.1%) v. 32/86 (37.2%); (P < 0.05)]. We concluded that an extended period of in vivo maturation is beneficial for embryo production after in vitro fertilization in wood bison. We thank Vetoquinol Canada for providing FSH (Folltropin-V) and hyaluronan (MAP-5) and thank Merck Animal Health for hCG (Chorulon).

50 BOVINE SPERM DEATH KINETICS: TEMPORAL CHANGES IN PRODUCTION OF REACTIVE OXYGEN SPECIES AND PLASMA MEMBRANE INJURY OF DAIRY AND BEEF FROZEN&ndash;THAWED SEMEN

The extent of changes in sperm structure and function affect the success of fertilization ultimately during the pathway to ovum in the female reproductive tract. The success of AI with frozen-thawed semen varies in dairy and beef breeds of bovine because of differed alterations in sperm during transport in female tract after insemination. To our knowledge, no report is available comparing the changes in dairy and beef sperm leading to death in female tract. Therefore, this study was aimed to investigate the changes in motility, generation of reactive oxygen species (superoxide and hydrogen peroxide), and their relation to sperm death [asymmetry (apoptosis) and rupture of plasma membrane] of dairy and beef frozen-thawed semen during incubation at 37°C for 24 h. This incubation was aimed to mimic the environment of female reproductive tract. Frozen dairy semen (n = 4 bulls) was procured from a Canadian breeding station, whereas beef semen was collected from breeding beef bulls (n = 3; 5 replicates), diluted with Tris-based extender (composition was same as used in dairy semen), cooled to +4°C over 90 min, and cryopreserved by programmable freezer using standard rate as used in dairy semen. Two straws per replicate were thawed at 37°C from both types of semen, pooled separately, and incubated at 37°C for 24 h in capped tubes. Each pooled semen sample was evaluated for motility with CASA, superoxide (O2–, and hydrogen peroxide (H2O2) radical using HE/YoPRO and H2DCFDA/PI assay, respectively, and asymmetry of plasma membrane using YoPRO/PI assay through flow cytometric analysis at 0, 2, 4, 6, 12, and 24 h of incubation. The MIXED procedure of SAS (SAS Institute Inc., Cary, NC, USA) was used to analyse the data as 2 × 6 factorial model for 2 types of semen (dairy and beef) and 6 time points using time as repeated measure. A threshold limit of 30% was considered for motility and live sperm to get optimum fertility. Sperm motility remained higher (P < 0.05) than threshold limit till 6 h in dairy (50.95 ± 2.62%) and 2 h in beef semen (30.28 ± 6.95%). Dairy semen possessed more (P < 0.05) nonapoptotic sperm without O2– (HE–/YoPRO–) till 6 h of incubation than beef semen. The increase in apoptotic sperm containing superoxide radical (HE+/YoPRO+) over time was more (P < 0.05) in beef semen till 6 h of incubation. The rise in dead sperm containing H2O2 (H2DCFDA+/PI+) was recorded more in beef than in dairy semen until 6 h of incubation. Live sperm without apoptosis (YoPRO–/PI–) were higher until 24 h in dairy (49.36 ± 4.56%) compared with beef semen (24.89 ± 3.85%), whereas viable sperm with apoptosis (YoPRO+/PI–) were found similar in both types of semen over time. In conclusion, dairy frozen-thawed semen possessed more live sperm without reactive oxygen species (superoxide and hydrogen peroxide) until 6 h of incubation than did beef semen. The decrease in superoxide radical was more in dairy than in beef semen. Dead and apoptotic sperm increased more in beef frozen-thawed semen over time during incubation. This inference suggests performing the insemination late near ovulation with beef frozen-thawed semen because of less viable life than dairy semen.

248 IN VITRO EMBRYO PRODUCTION USING IN VIVO-MATURED OOCYTES COLLECTED TRANSVAGINALLY FROM WOOD BISON (BISON BISON ATHABASCAE)

Reproductive technologies are being developed to help conserve the genetic diversity of wood bison, a threatened species. To date, the efficiency of in vitro embryo production in bison is very low and appears to be related to inadequate in vitro conditions for oocyte maturation. Recently, we have attempted to circumvent the problem by inducing oocyte maturation in vivo and found that more than one-third of superstimulated oocytes collected 30 h after administration of hCG were at metaphase II (Cervantes et al. 2013 Reprod. Fertil. Dev. 25, 283; Cervantes et al. 2014 Reprod. Fertil. Dev. 26, 199). We hypothesise that additional maturation time in vitro, after in vivo maturation, will allow the remaining oocytes to reach the MII stage, and thus improve in vitro embryo production in wood bison. The objective of this study was to determine the effect of an additional 4 h of in vitro maturation on the developmental competence of oocytes collected 30 h after hCG treatment. Wood bison cows (n = 24) were superstimulated by the administration of 300 mg of FSH (Folltropin-V) diluted in 0.05% hyaluronan on the day of follicular wave emergence and 100 mg of FSH in hyaluronan 2 days later. Bison were administered 2500 IU of hCG (Chorulon) IM 2 days after the last dose of FSH. Transvaginal ultrasound-guided follicle aspiration was performed 30 h after hCG treatment to collect cumulus-oocyte complexes (COC). Expanded COC (with no evidence of degeneration) were selected and assigned randomly to 2 groups (n = 38 COC/group) in which IVF was done immediately, or after 4 h of in vitro maturation in TCM 199 with 5% calf serum, 5 μg mL–1 pLH, 0.5 μg mL–1 pFSH, and 0.05 μg mL–1 gentamicin, at 38.5°C, 5% CO2 and high humidity. In vitro fertilization (Day 0) was done with frozen-thawed wood bison semen (dose 5 × 106 sperm mL–1) in Brackett-Oliphant medium at 38.5°C, 5% CO2, and high humidity. Presumptive zygotes were cultured in CR1aa plus 5% calf serum, at 38.5°C and in 5% CO2, 5% O2, and 90% N2 and high humidity. Cleavage was recorded on Day 3, and blastocyst formation was recorded on Days 7 and 8. Cleavage and blastocyst rates (calculated from the total number of oocytes submitted to IVF) were compared between groups by chi-square analysis. No difference was detected between groups (immediate fertilization v. after an additional 4 h in vitro) in cleavage rate on Day 3 (55.3 v. 60.5%, respectively, P = 0.82), or blastocyst rate on Day 7 (13.2 v. 23.7%, respectively, P = 0.37). However, the blastocyst rate on Day 8 was higher in the COC group exposed to an additional 4 h of in vitro maturation (18.4 v. 44.7%, respectively, P = 0.03). Results support the hypothesis that an additional short period of in vitro maturation improves the developmental competence of oocytes collected after 30 h of in vivo maturation.We thank Bioniche Animal Health for providing FSH (Folltropin-V) and hyaluronan (MAP-5), and Merck Animal Health for hCG (Chorulon).

47 THE AVIAN CHORIO-ALLANTOIC MEMBRANE: A SUITABLE SHORT-TERM CULTURE SYSTEM FOR BOVINE OVARIAN TISSUE

Successful cryopreservation of bovine ovarian tissue holds enormous potential for long-term maintenance of female gametes to preserve genetic diversity by tissue banking. Traditionally, in vitro culture followed by histopathological examination has been used to assess the post-thaw viability of cryopreserved tissues. Recently, in ovo transplantation of mammalian tissues on the chorio-allantoic membrane (CAM) of a growing chicken embryo has emerged as an alternative method for short-term culture. The purpose of this experiment was to compare CAM culture of bovine ovarian tissue over a 5-day period with the in vitro culture system. Fertilized White Leghorn eggs were incubated at 37°C and 62% relative humidity. A window (1 × 2 cm) was cut into the eggshell on Day 3 of incubation. Ovaries were retrieved from a local abattoir and brought to the laboratory within 6 h. Ovarian cortex pieces (1–2 mm3) were randomly assigned to control, CAM-culture, or in vitro-culture groups. Control-group tissues were fixed immediately in 4% paraformaldehyde. The CAM was traumatized on Day 10 of incubation to expose the underlying blood vessels, and tissue pieces were grafted at the site (one graft per egg). For in vitro culture, the ovarian cortex pieces were placed on tissue culture inserts within 6-well plates containing TCM199 with 1% insulin-transferrin-selenium, 100 mIU mL–1 of FSH, 100 IU mL–1 of penicillin, and 50 μg mL–1 of streptomycin and incubated at 38°C in 5% CO2. Ovarian tissues from the CAM and in vitro culture group were removed on Day 1, 3, and 5 of grafting/culture, fixed, embedded in paraffin, sectioned at 5 μm, stained with hematoxylin-eosin, and analysed under a light microscope. The numbers of normal and degenerated follicles (indicating follicle survival) and number of blood vessels containing bovine and avian red blood cells (indicating angiogenesis) were counted using standard stereological procedures. All ovarian cortex grafts from surviving chick embryos showed adhesion with the CAM and a marked neo-vascularization in the graft areas. Gross and histological examination revealed the circulation of avian blood cells in ovarian stromal vessels with a concomitant decrease in the number of bovine blood vessels over the incubation period. Total follicle densities (mean ± s.e.m.) on Day 1, 3, and 5 were 13.3 ± 5.9, 27.9 ± 6.7, and 36.9 ± 7.3 in the in vitro-cultured group and 36.7 ± 13.0, 73.6 ± 24.0, and 44.02 ± 12.67 per millimeter cubed in the CAM-cultured group, respectively. Overall, total follicle density was higher in the CAM-cultured group (P < 0.05). Likewise, the normal follicle densities on Day 1, 3, and 5 were 10.4 ± 4.9, 15.5 ± 3.6, and 20.7 ± 6.3 in the in vitro-cultured group and 30.5 ± 8.5, 45.7 ± 18.4, and 22.7 ± 7.3 per millimeter cubed in the CAM-cultured group (P > 0.05). In conclusion, in ovo CAM grafting system was as successful as the in vitro-culture system and may be considered an acceptable alternative to the traditional in vitro-culture system for bovine ovarian tissue.

171 IN VIVO AND IN VITRO MATURATION OF WOOD BISON (BISON BISON ATHABASCAE) CUMULUS–OOCYTE COMPLEXES DURING THE OVULATORY SEASON

Technologies are being developed to conserve the genetic diversity of wood bison. Knowledge of the characteristics of in vivo and in vitro maturation of the cumulus–oocyte complex (COC) are needed in wood bison to design efficient in vitro embryo production protocols. The objectives were to (1) determine the optimal interval after hCG treatment for in vivo maturation of COC in superstimulated wood bison, and (2) compare the characteristics of COC after in vitro and in vivo maturation. Ovarian synchronization was induced in 25 bison during October and November by giving a luteolytic dose of prostaglandin followed 8 days later by follicular ablation (Day –1). Ovarian superstimulation was induced with FSH (Folltropin-V) given i.m. on Day 0 (300 mg) and Day 2 (100 mg). A second luteolytic dose of prostaglandin was given on Day 3. Bison were assigned randomly to 5 groups (n = 5/group). The COC were collected by transvaginal follicle aspiration on Day 4 and were either assessed immediately (0 h, control), or matured in vitro for 24 or 30 h (in vitro maturation), or collected on Day 5 (in vivo maturation), 24 or 30 h after bison were given 2000 IU of hCG i.m. on Day 4. In vitro maturation was done in TCM-199 with 5% calf serum, 5 μg mL–1 LH, 0.5 μg mL–1 FSH, and 0.05 μg mL–1 gentamicin, at 38.5°C and in a 5% CO2 humidified atmosphere. Nuclear maturation was classified as germinal vesicle (GV), germinal vesicle breakdown (GVBD), metaphase I (MI), or metaphase II (MII) with anti-lamin AC/DAPI staining. Groups were compared by analysis of variance and Fisher's exact test (Table 1). A mean (±s.e.m.) of 7.3 ± 1.7 COC were collected per bison, with no difference among groups. The COC in the control (0 h) group were at the nonexpanded GV stage. Cumulus cells were more expanded after in vivo than in vitro maturation, and the percentage of fully expanded COC was the highest in the 30-h in vivo maturation group (87%; P < 0.05). The greatest number of oocytes reached MII stage after 24 h of in vitro maturation, and 30 h of in vivo maturation. In conclusion, nuclear maturation occurred more quickly in vitro compared with in vivo, but the degree and incidence of cumulus expansion was greater after in vivo maturation. The competence of oocytes to undergo fertilization and develop into embryos remains to be investigated. Table 1.Cumulus expansion and nuclear maturation of wood bison oocytes

310 DOES PROGESTERONE OR EQUINE CHORIONIC GONADOTROPIN IMPROVE THE SUPEROVULATORY RESPONSE AND EMBRYO QUALITY IN WOOD BISON DURING THE ANOVULATORY SEASON?

Superovulation protocols are being developed in wood bison (Bison bison athabascae), a threatened Canadian species. In initial studies, 2 doses of FSH diluted in hyaluronan given 48 h apart were successful for inducing ovarian superstimulation in wood bison, and ovulation rate was improved by final treatment with hCG instead of LH (Palomino et al. 2012 Reprod. Fertil. Dev. 24, 226). In that study, exogenous progesterone had no effect on the number of ovulations, but embryo quality could not be evaluated because of the low number of embryos collected. In beef cattle, replacement of the final doses of FSH with eCG has resulted in the recovery of a greater number of ova/embryos. The objective of the present study was to evaluate the effect of exogenous progesterone (PRID) on embryo quality and to determine if the addition of eCG increases the ovulation rate in superstimulated wood bison. Follicular ablation was done to synchronize follicular wave emergence in 26 wood bison cows during the anovulatory season (May). Cows were assigned randomly to 3 groups: PRID/no eCG (n = 8), PRID/eCG (n = 9), and no PRID/eCG (n = 9). A PRID was inserted on the day of follicular ablation (Day –1) in respective groups. In all bison, FSH diluted in hyaluronan (5 mg mL–1, MAP-5, Bioniche Animal Health Inc., Belleville, Ontario, Canada) was given intramuscularly on Day 0 (300 mg) and Day 2 (100 mg). On Day 3, a single dose of 450 IU of eCG (Pregnecol, Bioniche Animal Health Inc.) was given intramuscularly and the PRID were removed in the corresponding groups. On Day 5, all bison were given 2500 IU of hCG (Chorulon, Merck, Whitehouse Station, NJ, USA) intramuscularly to induce ovulation. Bison were inseminated with chilled semen 12 and 24 h later. Nonsurgical embryo collection was performed on Day 14. Transrectal ultrasonography was done to record the ovarian response, ovulation rate, and number of corpora lutea (CL). Results were compared by ANOVA and Chi-squared test (Table 1). The number of ovulatory-sized follicles (≥9 mm) on Day 5 did not differ among groups. Ovulation rate was lowest in bison treated with both a PRID and eCG (P < 0.05). There were no differences among groups in the number of CL on Day 14, the number of ova/embryos collected, or the number of transferable embryos. The superovulatory response and embryo collection rate in the present study were higher than in any previous reports in bison. The ovulation rate was not improved by the addition of eCG treatment, and exogenous progesterone had no effect on embryo quality. Table 1.Response of superstimulated wood bison (mean ± SEM) to treatment with exogenous progesterone (PRID) and/or eCG

271 NUCLEAR MATURATION OF WOOD BISON (BISON BISON ATHABASCAE) CUMULUS - OOCYTE COMPLEXES

Methods of producing wood bison embryos in vivo and in vitro are being developed in an effort to preserve the genetic diversity of this threatened species. Previous data from our laboratory suggest that oocytes collected 24 h after LH treatment had not yet achieved nuclear maturation. The objectives of this study were (1) to determine the optimal interval of time after hCG treatment required for in vivo maturation of cumulus–oocyte complexes (COC) in wood bison, and (2) to compare the maturational characteristics of COC after in vitro v. in vivo maturation. Follicular wave emergence was synchronized among bison cows (n = 25) by follicular ablation (Day –1) from May to June. Ovarian superstimulation was induced with FSH IM diluted in 5 mg mL–1 of hyaluronan (MAP-5, Bioniche, Belleville, Ontario, Canada) given on Day 0 (300 mg) and Day 2 (100 mg). Superstimulated cows were assigned randomly to 5 groups (n = 5/group): COC collected on Day 4 with no maturation (control), or matured in vitro for 24 or 30 h, or collected 24 or 30 h after treatment with 2000 IU of hCG IM on Day 4. The COC were collected by transvaginal ultrasound-guided follicle aspiration. In vitro maturation was done in TCM-199 with 5% calf serum, 5 µg mL–1 of LH, 0.5 µg mL–1 of FSH, and 0.05 µg mL–1 of gentamicin, at 38.5°C and in 5% CO2. To assess nuclear maturation, oocytes were stained with anti-lamin AC/DAPI (4′,6-diamidino-2-phenylindole). Nuclear stages were classified as germinal vesicle (GV), GV breakdown (GVBD), metaphase I (MI), or metaphase II (MII). Comparisons among groups were made by ANOVA and Fisher’s exact test (Table 1). A mean (± SEM) of 7.6 ± 0.6 COC was collected per bison; no differences were observed among groups (P = 0.37). Cumulus cell expansion was more extensive after in vivo than in vitro maturation, and the percentage of fully expanded COC was highest in the in vivo 30-h group (97%; P < 0.05). No COC were expanded in the control (0 h) group, and none reached MI. Maximal nuclear maturation was achieved in vitro by 24 h; that is, there was no difference in the proportion of MII-stage COC at 24 versus 30 h. However, between 24 and 30 h of in vivo maturation, the percentage of nuclear stages GV + GVBD decreased from 54 to 24% (P < 0.05), whereas nuclear stages MI + MII increased from 39 to 74% (P < 0.05). In conclusion, nuclear maturation occurred earlier in vitro versus in vivo, but the consequences of this difference are unknown. Although more than one-third of oocytes matured in vivo for 30 h were mature enough to permit immediate IVF, whether additional in vivo maturation time would be beneficial to fertilization rates remains to be tested. Table 1.Nuclear status of wood bison oocytes after in vitro or in vivo maturation Thanks to Bioniche Canada.

71 BOVINE SPERM DEATH KINETICS: CHANGES IN MOTILITY, ACROSOMES, AND PLASMA MEMBRANE

Extent and timing of alterations in structures and functions of sperm after its placement in the female reproductive tract are important for successful fertilization. To our knowledge, the few reports are available on the kinetics of alterations in bovine sperm structures and functions during pathway to their death. Therefore, the present study was conducted to determine the changes in motility, acrosome and plasma membrane asymmetry in fresh and frozen–thawed semen during incubation at 37°C over the period of 24 h. Semen was collected from 3 breeding beef bulls, pooled, and considered as one replicate (total replicates = 5). Each pooled semen sample was diluted in Tris-citric acid egg yolk glycerol extender (pH 6.8), cooled to +4°C over 90 min, and then cryopreserved by a programmable cell freezer. Fresh (pooled semen) and frozen–thawed semen were incubated at 37°C for 24 h. Each semen sample was evaluated for sperm motility with computer-assisted semen analysis and acrosomal integrity and plasma membrane asymmetry using fluorescein isothiocyanate-peanut agglutinin/propidium iodide and Annexin V/propidium iodide assays, respectively, at 0, 2, 4, 6, 12, and 24 h of incubation at 37°C, with a flow cytometer. Statistical analysis was conducted using PROC MIXED model in statistical analysis system as 2 (semen types) × 6 (times) factorial model, using time as repeated measure. Progressive motility was higher (P < 0.05) in fresh than in frozen–thawed semen until 6 h. Progressive motility declined (P < 0.05) below the threshold level (i.e. 30%) much later (12 h) in fresh as compared with frozen–thawed semen (2 h). However, acrosomal integrity and plasma membrane asymmetry deteriorated (P < 0.05) below threshold at the same time interval (2 h) in both fresh and frozen–thawed semen. Viable sperm (AN–/PI–) remained higher (P < 0.05) during the first 6 h in fresh than in frozen–thawed semen and declined (P < 0.05) below the threshold at 12 h in fresh and at 6 h in frozen–thawed semen. In fresh semen, the necrotic sperm (AN–/PI+) population increased (P < 0.05) over time and reached maximum (97%) at 24 h. In frozen–thawed semen, a mixed population of late apoptotic (53%) and necrotic (34%) sperm was found at 24 h. In conclusion, the alterations in sperm motility, acrosomes, plasma membrane integrity, and asymmetry were slower in fresh than in frozen–thawed semen. Fresh sperm followed necrosis and frozen–thawed sperm underwent necrosis and apoptosis-like pathways, respectively. This study was supported by the Canadian Commonwealth Scholarship Program by the Canadian Bureau for International Education (CBIE), and Agriculture and Agri-Food Canada.

227 SUPEROVULATION AND EMBRYO COLLECTION IN WOOD BISON DURING THE ANOVULATORY SEASON

Brucellosis and tuberculosis are endemic in Wood Buffalo National Park, the largest reserve of wood bison (Bison bison athabascae) in Canada. Our goal is to produce and preserve disease-free embryos for the purpose of wood bison repopulation. This study was designed to determine if embryo collection is feasible in wood bison during the anovulatory season (May–July) and to test if progesterone priming is required for superovulation. A 2-by-2 design was used to determine the effectiveness of LH (Lutropin) or hCG (Chorulon) for induction of ovulation with or without intravaginal progesterone releasing device (PRID) in 32 wood bison cows. Follicular wave emergence was synchronized among bison by transvaginal ultrasound-guided follicle ablation. Synchronized bison were assigned to 4 groups: PRID+LH (n = 12), PRID+hCG (n = 4), no-PRID+LH (n = 12) and no-PRID+hCG (n = 4). A PRID was inserted on the day of follicular ablation in the respective groups. A single SC dose of 400 mg FSH (Folltropin) in a slow-release formulation was given the day after follicular ablation (i.e. on the expected day of a new follicular wave emergence, Day 0). The PRID was removed on Day 4 and either 25 mg LH or 2000 IU hCG was given IM on Day 5. Artificial insemination was done at 24, 36 and 48 h after LH or hCG treatment. Embryos were collected nonsurgically on Day 13 using commercial bovine equipment. Transrectal ultrasonography was done on Days 0, 5, 6, 7, 8 and 13 to record follicular and ovulatory responses. Count data (mean ± SEM) were analysed by two-way ANOVA and proportions by chi square. The number of ovulatory-sized follicles (≥10 mm) on Day 5 did not differ among groups (P = 0.33; Table 1). Ovulation rate (number of ovulations/number of follicles ≥10 mm) was greater in bison treated with hCG (P < 0.05; Table 1). The number of corpora lutea (CL) on Day 13 was greater in bison treated with hCG without a PRID (P < 0.05; Table 1). No differences in number of ova/embryos and transferable embryos were found among groups (P = 0.36 and P = 0.52, respectively; Table 1). In conclusion, progesterone priming (PRID) had no effect on ovarian superstimulation in wood bison in the anovulatory season. The ovulatory response was satisfactory only in bison treated with hCG. Embryo collection is feasible in wood bison, but the reasons for a low embryo collection rate in all groups remain unclear. Table 1.Response to superovulation and embryo collection in wood bison Funded by Advancing Canadian Agriculture and Agri-Food and Agri-Food Innovation.

45 THE EFFECT OF MEIOTIC STAGE OF BOVINE OOCYTES ON THE SURVIVAL OF VITRIFIED CUMULUS–OOCYTE COMPLEXES

Vitrification is a rapid freezing method in which cells/tissues are frozen in a glass state without ice crystal formation. However, vitrification of bovine oocytes is challenging due to their complex structure and sensitivity to chilling. Oocytes at the germinal vesicle (GV) stage of maturation are thought to be less prone to chromosomal and microtubular damage during cryopreservation because no spindle is present and genetic material is contained within the nucleus. However, immature oocytes are thought to be more sensitive to osmotic stress and have lower cell membrane stability than mature, metaphase II (MII) stage oocytes. The present studies aimed to validate the in vitro culture system used in our laboratory and to evaluate the effect of vitrification of bovine cumulus-oocyte complexes (COC) at different meiotic stages on their in vitro maturation (IVM), cleavage and early embryo development. Analyses were conducted on each dataset with PROC GLIMMIX in SAS using binary distribution (for yes/no response variable) and considering replicate as a random factor. In Experiment 1, meiotic progression of oocytes was evaluated at different time intervals during IVM. The following COC stages were predominantly found at different IVM time intervals: GV (89%) at 0 h, GV (47%) and germinal vesicle breakdown (GVBD; 44%) at 6 h, metaphase I (MI; 90%) at 12 h and MII (84%) at 22 h (n > 62 oocytes at each time group). In Experiment 2, bovine COC at 0, 6, 12 and 22 h of IVM were exposed to vitrification solution (15% dimethyl sulfoxide + 15% ethylene glycol + 0.5 M sucrose + 20% CS in TCM-199), loaded onto a cryotop device and vitrified by plunging in liquid nitrogen. Following warming (1 min in 0.5 M sucrose + 20% CS in TCM-199), COC completed 22 h of IVM and the nuclear stage was evaluated with lamin A/C-4′6-diamidino-2-phenylindole staining. Upon completion of 22 h of IVM, 23, 23, 35 and 89% of oocytes from 0-, 6-, 12- and 22-h groups, respectively were detected at MII (P < 0.0001). In Experiment 3, cleavage and embryo development of oocytes vitrified at 0, 12 and 22 h of IVM were evaluated. The cleavage rate did not differ among vitrification groups (i.e. 14% at 0 h, 17% at 12 h and 14% at 22 h; P = 0.825). Cleavage and blastocyst rates were higher (P < 0.0001) in the non-vitrified (control) group than in vitrified groups (i.e. 73 vs 15% and 22 vs 0.3%, respectively). In conclusion, the maturation kinetics validated our in vitro culture system and vitrification adversely affected the ability of bovine oocytes to undergo in vitro maturation to the MII stage, in vitro fertilization and early embryo development. Vitrification of oocytes at GV, MI and MII stages of nuclear maturation did not differ in their subsequent survivability. This study was supported by the Canadian Animal Genetic Resources Program, Agriculture and Agri-Food Canada.

86 EFFECT OF CRYOPROTECTANT EXPOSURE, VITRIFICATION, AND WARMING TIME OF BOVINE CUMULUS OOCYTE COMPLEXES ON IN VITRO FERTILIZATION AND EMBRYONIC DEVELOPMENT

Despite the importance of cryoprotectants for avoiding ice crystal formation, the high concentrations required for vitrification may be toxic to bovine oocytes. During warming (thawing), the removal of permeating cryoprotectants from cells can lead to osmotic injury, and the most appropriate time interval for warming and cryoprotectant removal from vitrified oocytes is currently uncertain. The present study aimed to evaluate the effect of cryoprotectant exposure, vitrification, and warming time of bovine cumulus oocyte complexes (COC) on fertilization and ability to develop as embryos in vitro. Follicles <8 mm in diameter were aspirated from slaughterhouse-derived bovine ovaries. Cumulus oocyte complexes with ≥3 layers of cumulus cells and a uniform cytoplasm were selected, washed 3 times in Dulbecco’s PBS + 5% newborn calf serum (CS), and randomly divided into 4 groups: 1) control group: no treatment; 2) VS1 group: COC were exposed to vitrification solution 1 [VS1: 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) in TCM-199 + 20% CS] for 5 min; 3) VS1+VS2 group: COC were exposed to VS1 for 5 min followed by vitrification solution 2 (VS2: 15% EG, 15% DMSO, and 0.5 M sucrose in TCM-199 + 20% CS) for 30 s; and 4) vitrified group: COC were exposed to VS1 and VS2, and then vitrified in liquid nitrogen using cryotops. The COC in VS1, VS1+VS2, and vitrified groups were exposed to a warming solution (0.5 M sucrose in TCM-199) for 1 or 5 min. The COC from all groups were in vitro matured (IVM) for 22 h in TCM-199 containing 5% CS, 5 μg mL–1 LH, 0.5 μg mL–1 FSH, and 0.05 μg mL–1 gentamicin at 38.5°C, 5% CO2, and high humidity, incubated with frozen–thawed sperm in Brackett-Oliphant capacitating medium for 18 h, and the presumptive zygotes were cultured in Charles Rosenkrans 1 amino acids (CR1aa) + 5% CS for 9 days. Data were analysed using Proc Glimmix in SAS® 9.2 (SAS Institute Inc., Cary, NC, USA). Cleavage and blastocyst rates in the vitrified group (25 and 2%, respectively) were significantly lower (P < 0.0001) than in control (75 and 27%), VS1 (68 and 19%), or VS1+VS2 (63 and 22%) groups. Cleavage and blastocyst rates did not differ among non-vitrified groups (P > 0.05). In VS1, VS1+VS2, and vitrified groups, warming time had no effect on cleavage or blastocyst rates (P > 0.05). In conclusion, although cryoprotectant exposure and warming times had no apparent adverse effect, vitrification of bovine COC drastically reduced cleavage and blastocyst rates. Further studies are required to understand how vitrification of bovine COC affects subsequent fertilization and embryo development. This study was supported by the Canadian Animal Genetic Resources Program, Agriculture and Agri-Food Canada.

233 EFFECTS OF A LONG-ACTING TRANQUILIZER ON SPERM MOTILITY OF NORTH AMERICAN BISON BULLS

Handling induces stress in North American bison that can lead to injuries for both handlers and animals. Moreover, this induced stress may result in variations in collection and quality of the semen. The objective of this study was to investigate if a long-acting neuroleptic (LAN) can lower the stress on bison bulls, allowing for safer handling and improvement in the quantity and quality of the collected semen. For this study, 6 mature bison bulls (3 Bison bison bison and 3 Bison bison athabascae) housed at the Native Hoofstock Centre, near Saskatoon, SK, Canada, were used. For each trial, bison bulls were randomly separated into 2 groups: LAN-treated (n = 3) and nontreated control (n = 3). In the treatment group, each bull was injected with 100 mg of Piportil L4® (piperodine phenothiazine, a LAN with antipsychotic properties and weak sedative activity that has a prolonged duration of action ≈2 wk). After injection, both groups were given a 5-day rest period before semen collection. All bison were collected by electroejaculation, twice a week for 2 wk with a minimum 48 h of rest between collections (total of 3 trials; 4 collections per trial). Between each trial, a rest period of 1 wk was given to the bulls. To evaluate the stress level of the animal, the bull’s heart and respiration rates were recorded before and after each collection. Electroejaculated semen was kept at 37°C and transported to the laboratory for further semen analysis (≈2 h). Semen was analysed using computer assisted sperm analyzer. Several parameters including volume, concentration, total motility, progressive motility, velocity curvilinear (VCL), velocity average path (VAP), and velocity straight line (VSL) were recorded. The data were analysed using two-way ANOVA (SAS 9.2; SAS Institute, inc., Cary, NC, USA). Data are presented as mean ± SD and P < 0.05 level of significance. Results for the stress level revealed that the heart rate (beats/min) before semen collection (control: 65.8 ± 14.6, treated: 65.3 ± 9.4) and heart rate after semen collection (control: 67. 9 ± 14.4, treated: 62.9 ± 9.1) showed no differences between control and treatment. Both respiration rates (breaths/min) before and after collection did not show difference due to treatment (control: 44.1 ± 17.5 and 36.6 ± 15.1, and treated: 41.6 ± 22.0 and 35.3 ± 14.3, respectively). Results of the semen analysis showed no significant effect of treatment on the volume of ejaculate between control (5.3 ± 2.0 mL) and treated (4.6 ± 2.4 mL). Both total and progressive motility of the semen showed no difference between control (70.5 ± 18.1% and 64.6 ± 19.4%) and treated (64.6 ± 22.7% and 58.6 ± 23.2%), respectively. No significant effects were seen in any of the sperm velocity parameters (μm s–1): VCL, 123.5 ± 31.5 in control and 121.7 ± 28.9 in treated; VAP, 75.4 ± 18.7 in control and 71.8 ± 17.2 in treated; and VSL, 62.3 ± 16.9 in control, and 59.3 ± 15.3 in treated groups. It can be concluded that 100 mg of Piportil has no discernible effect on stress levels, sperm count, or motility in bison bulls. Funded by Agriculture Development Fund (#2008044) and Canadian Animal Genetic Resources program.

Response of buffalo spermatozoa to low temperatures during cryopreservation

This is the first detailed report on the response of buffalo spermatozoa to low temperatures during freezing. The study determined the critical temperature zone for buffalo spermatozoa and developed a suitable freezing rate for this species. Semen from four Nili-Ravi buffalo bulls diluted in Tris-citric acid was frozen in a programmable freezer. Motion characteristics, plasma membrane integrity and acrosome morphology were determined at +4, 0, –5, –10, –20, –30, –40, –50, –80 and –196°C by removing semen straws from the freezer at exactly these temperatures and rewarming them at 37°C. The first statistical decline in sperm motility and lateral head displacement was observed at –40°C. For all other parameters, there was biphasic decline: for curvilinear velocity, at 0°C and –50°C; and for plasma membrane integrity and acrosome morphology, at –30°C and –50°C. In a second series of experiments, buffalo spermatozoa were frozen using slow (–10°C min–1), medium (–20°C min–1) or fast (–30°C min–1) freezing rates, between –10°C and –80°C. Freezing of buffalo spermatozoa at a rate of –30°C min–1 yielded higher post-thaw motion characteristics, plasma membrane integrity and normal acrosomes. In conclusion, different sperm characteristics respond differently at low temperatures and the freezing of buffalo spermatozoa at a higher rate ensures higher post-thaw semen quality.

73 VITRIFICATION OF BOVINE OOCYTES: EFFECT OF PACKAGING AND EQUILIBRATION TIME ON NUCLEAR MATURATION

The conservation of female animal genetics is challenging because of the scarcity of oocytes and their sensitivity to cryopreservation techniques. During slow, controlled freezing procedures, intracellular ice crystallization often leads to cell damage. Vitrification as an alternate method of cryopreservation exposes cells to a higher concentration of cryoprotectants with an ultra-rapid cooling rate, leading them to an ice-crystal-free, solid glasslike structure. The vitrification procedure has been used successfully for the cryopreservation of embryos and other body tissues, but very few reports of successful oocyte cryopreservation exist because of their complex structure. The present study was designed to compare two packaging methods (Cryotop v. 0.25-mL straw) and two equilibration times (10 v. 0 min) for vitrification of bovine oocytes. COC were aspirated from follicles <8 mm in diameter on bovine ovaries collected from a slaughterhouse. COC with ≥3 layers of cumulus cells and a uniform cytoplasm were selected, washed in Dulbecco’s phosphate-buffered saline (DPBS) + 5% calf serum (CS), and divided into five equal groups. In the control group, the COC were washed in TCM-199 + 5% CS and matured in vitro in TCM-199 containing 5% CS, 5 μg mL–1 of LH, 0.5 μg mL–1 of FSH, and 0.05 μg mL–1 of gentamicin at 38.5°C, 5% CO2, and high humidity for 22 h. In the treatment groups, half the COC were equilibrated with vitrification solution 1 [VS1: TCM-199, 7.5% ethylene glycol (EG), 7.5% DMSO, and 20% CS] for 10 min. After equilibration, COC were exposed to vitrification solution 2 (VS2: TCM-199, 15% EG, 15% DMSO, 20% CS, and 17.1% sucrose) for 30 s. The remaining half of the COC were directly exposed to VS2 without equilibration in VS1. Groups of five equilibrated or nonequilibrated COC were either loaded in a 0.25-mL straw or placed on Cryotop and plunged in liquid nitrogen. The COC were thawed by immersing straws and Cryotops into 37°C thawing solution (TCM-199, 20% CS, and 17.1% sucrose) for 1 min, and were washed and matured in vitro, as described above. After maturation, the COC were denuded using 0.3% hyaluronidase in Ca-Mg free DPBS and mounted on slides. The oocytes were fixed in ethanol:acetic acid (3:1) for 24 h, stained with aceto-orcein for 20 min, and evaluated for stage of maturation. The data (maturation rates) were analyzed using chi-square analysis. In the control group, 61% (n = 54) of the oocytes reached the metaphase-II (M-II) stage. In the treatment groups, more (P < 0.001) oocytes vitrified on Cryotops reached the M-II stage than those vitrified in straws (23.4%; n = 107 v. 9.4%; n = 116). The effect of equilibration time was not significant (P > 0.05) in either packaging method. In conclusion, vitrification of bovine oocytes using the Cryotop method provides an alternative for the cryopreservation of bovine oocytes. Moreover, bovine oocytes can be successfully vitrified without equilibration. This study was supported by the Canadian Animal Genetic Resources Program, Agriculture and Agri-Food Canada.

Antagonist effect of DMSO on the cryoprotection ability of glycerol during cryopreservation of buffalo sperm

The objective of the present study was to investigate the synergistic effect of DMSO and glycerol added at various temperatures on the post-thaw quality of buffalo sperm. Pooled ejaculates from four Nili-Ravi buffalo bulls were divided into 18 aliquots and extended (1:10) in Tris-citric acid extender differing in glycerol:DMSO ratios (0:0, 0:1.5, 0:3; 3:0, 3:1.5, 3:3; and 6:0, 6:1.5, 6:3, respectively; %, v:v) either at 37 or 4 degrees C. Semen was packaged in 0.5 mL French straws and frozen in a programmable cell freezer. Thawing was performed at 37 degrees C for 50s. Post-thaw motion characteristics, plasma membrane integrity and acrosome morphology of buffalo sperm were determined using computer-assisted semen analyzer (CASA), hypoosmotic swelling (HOS) assay and phase-contrast microscopy, respectively. Glycerol (6%) in extender yielded better post-thaw sperm motility, velocities (straight-line and average path), plasma membrane integrity, and normal acrosomes (P<0.05). Post-thaw sperm motility and plasma membrane integrity declined in the presence of DMSO (P<0.01). The addition of glycerol (6%) at 37 degrees C yielded better post-thaw sperm motility, plasma membrane integrity and velocities than addition at 4 degrees C (P<0.05). In conclusion, glycerol is still an essential cryoprotectant for buffalo sperm. The addition of DMSO antagonized the cryoprotection ability of glycerol and reduced the post-thaw quality of buffalo sperm. Furthermore, 6% glycerol added at 37 degrees C, provided better cryoprotection to the motility apparatus and plasma membrane integrity of buffalo sperm.

Spontaneous uptake of exogenous DNA by bull spermatozoa

Sperm-mediated DNA transfer can be used to transfer exogenous DNA into the oocyte for the production of transgenic animals. In spite of controversy in the literature, sperm-mediated DNA transfer is a simple and quick technique that can be used in routine breeding programs (AI, embryo transfer and IVF). The main objective of this study was to determine the factors affecting the spontaneous uptake of exogenous DNA by bull spermatozoa. For this purpose, fresh and frozen spermatozoa (0.25 x 10(6)), from the same ejaculate from each of four bulls were co-incubated with fluorescent-labeled green fluorescent protein (GFP) and chloremphenicol acetyltransferase (CAT) plasmids at 37 degrees C for 30 min. Neither bull nor plasmid significantly affected the uptake of exogenous DNA. However, transfection efficiency was higher in frozen-thawed versus fresh spermatozoa (P<0.001). Regardless of whether transfected spermatozoa were alive or dead, all transfected spermatozoa were immotile. It can be concluded that a population of spermatozoa is present in bull semen which has the ability to uptake exogenous DNA spontaneously. There is tremendous scope to improve transfection efficiency of spermatozoa while maintaining motility; this needs to be achieved in order to more easily use this technique in transgenesis. However, live-transfected bull spermatozoa clearly can incorporate exogenous DNA and should be usable in intracytoplasmic sperm injection protocols.

Sephadex and sephadex ion-exchange filtration improves the quality and freezability of low-grade buffalo semen ejaculates

The effect of sephadex and sephadex ion-exchange filtration on the improvement in quality and freezability of low-grade buffalo semen ejaculates was assessed. Two types of filtration columns were used: one containing only sephadex G-10 (FS) and the other sephadex G-10 along with ion-exchangers (diethyl amino ethane-52 (DEAE-52) cellulose and carboxy methyl-52 (CM-52) cellulose; FS+IE). Unfiltered samples served as controls. Semen ejaculates extended in Tris-citric acid (1:4) (n=16; initial motility 40-50%) were filtered at the rate of 1.5 ml/min under negative pressure at room temperature (28-30 degrees C). The mean recovery rate (%) of motile spermatozoa in the FS (85.9+/-1.51) and FS+IE (77.10+/-2.28) filtrates did not differ significantly. Percentages of sperm motility, normal acrosomes, and intact plasma membranes were highest (P<0.05) in FS+IE, intermediate (P<0.05) in FS and lowest (P<0.05) in controls at the three stages of cryopreservation (postfiltration final dilution, after equilibration, and after freezing). Mean sperm abnormalities were lowest (P<0.05) in the filtrates of FS+IE, moderate (P<0.05) in FS and highest in controls at all stages of freezing. Compared to dilution and equilibration, freezing greatly reduced (P<0.05) the overall percent motility, normal acrosomes and intact plasma membranes. The spermatozoa eluted through FS+IE columns proved more resistant (P<0.05) in bearing dilution, equilibration, freezing and thawing stresses than the spermatozoa from FS and control samples. It is concluded that filtration systems containing an FS+IE column can effectively enhance the quality and freezability of extended, low quality buffalo semen.

Optimizing and quantifying fusion of liposomes to mammalian sperm using resonance energy transfer and flow cytometric methods

BACKGROUND

Liposomes are used to carry pharmaceutical agents and to alter the lipid composition of cell membranes. This study compared resonance energy transfer (RET), fluorescence dequenching, and flow cytometry as monitors and quantifiers of fusion between liposomes and mammalian spermatozoa.

METHODS

Preliminary experiments used RET to determine the optimum sperm concentration for fusion of DL-alpha-phosphatidylcholine dipalmitoyl (PC)/DL-alpha-phosphatidylethanolamine dipalmitoyl (PE) liposomes at 35 degrees C +/- 5 mM Ca2+. Microscopy confirmed the fusion of liposomes, not just adhesion (n = 3). Dequenching tested the time-dependent fusion of liposomes of two different lipid compositions to sperm, both, (n = 3) +/- 1 mM Ca2+ and (n = 3) without Ca2+ at two sperm concentrations. Finally, flow cytometry absolutely quantified the percentage of sperm fusing to liposomes at different liposome-to-sperm ratios (n = 4) and with sperm from different donors (n = 3).

RESULTS

RET detected fusion of liposomes with sperm and microscopy confirmed the interaction to be true fusion. Dequenching detected more fusion of liposomes with sperm at 100 x 10(6) sperm per milliliter than at lower concentrations (P < 0.05). Fusion dynamics differed with lipid composition but Ca2+ had no effect. Flow cytometry reliably quantified the percentage of sperm fusing with liposomes, which varied from bull to bull (P < 0.05).

CONCLUSION

Liposome fusion with mammalian sperm membranes can be quantified cytometrically and varies with lipid composition, sperm-to-liposome ratio, and individual animals.

Changes in motion characteristics, plasma membrane integrity, and acrosome morphology during cryopreservation of buffalo spermatozoa

Motion characteristics, plasma membrane integrity, and acrosome morphology of buffalo spermatozoa after different stages of cryopreservation (ie, dilution, cooling to 4 degrees C, equilibration at 4 degrees C, and freezing and thawing) were examined. Semen ejaculates from 4 buffalo bulls were pooled (n = 5), diluted in tris-citric acid extender, cooled to 4 degrees C over 2 hours, equilibrated at 4 degrees C for 4 hours, dispensed into 0.5-mL straws, and frozen in a programmable cell freezer before plunging into liquid nitrogen. Frozen semen was thawed at 37 degrees C for 15 seconds. After completion of each stage, sperm motion characteristics, plasma membrane integrity, and acrosomal morphology were determined using computer-assisted semen analysis, hypo-osmotic swelling assay, and phase-contrast microscopy, respectively. Data were presented as mean +/- standard error of the mean. Visual and computerized motility did not differ due to dilution, cooling, or equilibration (77.3% +/- 2.3% and 90.5% +/- 1.2%, respectively), but was reduced (P < .05) after freezing and thawing (53.0% +/- 4.6% and 48.6% +/- 6.5%, respectively). Linear motility of spermatozoa was lower (P < .05) after dilution or equilibration (56.2% +/- 2.4%) than after cooling or freezing and thawing (79.6% +/- 1.4%). Sperm curvilinear velocity was reduced (P < .05) from 112.4 +/- 5.3 microm/sec after dilution to 96.0 +/- 5.8 microm/s after cooling, and from 87.6 +/- 4.1 microm/s after equilibration to 69.4 +/- 2.0 microm/s after freezing and thawing. Sperm lateral head displacement differed (P < .05) after each stage (ie, dilution, 3.9 +/- 0.2 microm; cooling, 2.3 +/- 0.2 microm; equilibration, 3.1 +/- 0.3 microm; and freezing and thawing, 1.7 +/- 0.2 microm). Spermatozoa with intact plasma membranes were 80.2% +/- 3.9% after dilution, reduced (P < .05) to 60.4% +/- 5.6% after equilibration, and then to 32.6% +/- 3.8% after freezing and thawing. The percentage of spermatozoa with normal acrosomes remained higher after dilution, cooling, or equilibration (73.2% +/- 2.4%) than after freezing and thawing (61.8% +/- 2.4%; P < .05). In conclusion, the maximal damage to the motility apparatus, plasma membrane, and acrosomal cap of buffalo spermatozoa occurs during freezing and thawing followed by equilibration.

Effect of buffering systems on post-thaw motion characteristics, plasma membrane integrity, and acrosome morphology of buffalo spermatozoa

This study was carried out to identify the suitable buffer for cryopreservation of buffalo semen. Semen was collected with artificial vagina (42 degrees C) from four buffalo bulls. Split pooled ejaculates (n=5), possessing more than 60% visual sperm motility, were extended at 37 degrees C either in tri-sodium citrate (CITRATE), Tris-citric acid (TCA), Tris-Tes (TEST) or Tris-Hepes (HEPEST). Semen was cooled to 4 degrees C in 2 h, equilibrated at 4 degrees C for 4 h, filled in 0.5 ml straws and frozen in a programmable cell freezer before plunging into liquid nitrogen. Thawing of frozen semen was performed after 24 h at 37 degrees C for 15 s. Sperm motion characteristics, plasma membrane integrity, and acrosome morphology of each semen sample were assessed by using computer-assisted semen analyzer (CASA), hypo-osmotic swelling (HOS) assay, and phase-contrast microscope, respectively. Analysis of variance revealed that percent post-thaw visual motility tended (P=0.07) to be higher in HEPEST (61.0+/-2.9) and lowest in CITRATE (48.0+/-2.5). Computerized motility did not vary due to buffering system. Percent post-thaw linear motility tended (P=0.09) to be higher in TCA (78.2+/-5.5) and lower in TEST (52.0+/-6.9). Circular motility (%) was significantly lower (P<0.05) in TCA (11.6+/-2.8) and higher in TEST (29.8+/-5.6). Curvilinear velocity (microm s(-1)) was lower (P<0.05) in TCA (69.4+/-2.0) than in CITRATE (79.0+/-5.8), TEST (87. 2+/-1.6) and HEPEST (82.6+/-3.0). Lateral head displacement (microm) was lowest (P<0.05) in TCA (1.7+/-0.2) and highest in TEST (3.7+/-0. 6). Plasma membrane integrity and normal acrosomes of buffalo spermatozoa did not differ due to buffering system and averaged 40. 0+/-2.7% and 61.4+/-4.6%, respectively. Based upon lower circular motility, curvilinear velocity, and lateral head displacement, it is concluded that post-thaw quality of buffalo semen can be improved using the Tris-TCA buffering system.

Separation of motile spermatozoa from frozen-thawed buffalo semen: swim-up vs filtration procedures

Three experiments were conducted to maximize the recovery rate of motile spermatozoa from frozen-thawed buffalo semen. In Experiment 1, the swim-up of motile spermatozoa was performed in the presence or absence of HEPES in TALP medium and CO2 in the environment. The recovery rate of motile spermatozoa in TALP medium (control), TALP + HEPES + CO2, TALP + HEPES and TALP + CO2 was 15, 18, 12 and 10%, respectively (P > 0.05), with sperm motility at 87, 89, 90 and 90%, respectively (P > 0.05). In Experiment 2, the pH of TALP medium was adjusted to 7.0, 7.5, 8.0, 8.5 and 9.0, and swim-up procedure was performed in the presence of HEPES and CO2. The recovery rate of motile spermatozoa at different pH was 14, 20, 24, 27 and 16%, respectively (P < 0.05). Motility of separated spermatozoa was 88, 91, 90, 89 and 90%, respectively (P > 0.05). In Experiment 3, the efficiency of ion-exchange filtration and Swim-up procedure in separating motile spermatozoa from frozen-thawed buffalo semen was compared. The recovery rate of motile spermatozoa was 95% in filtration procedure and 33% in swim-up procedure (P < 0.005). In all experiments, normal acrosomes did not vary due to treatments (P > 0.05). In conclusion, HEPES and CO2 had no significant effect on swim-up of buffalo spermatozoa. The pH 8.5 of TALP improved the recovery rate of motile spermatozoa in swim-up procedure. The ion-exchange filtration was found superior to swim-up procedure in harvesting maximum number of motile spermatozoa from frozen-thawed buffalo semen (95 vs 33%; P < 0.001).

Post-thaw plasma membrane integrity of bull spermatozoa separated with a sephadex ion-exchange column

Previous experiments have established that filtration of bovine semen through a Sephadex ion-exchange column improves its quality before and after freezing. The present study was conducted to determine the post-thaw membrane integrity of bull spermatozoa separated with a Sephadex ion-exchange column and to determine the kind of protection to spermatozoa is provided by glycerol during freezing and thawing. Semen from Holstein bulls diluted in TEST-yolk extender (with and without glycerol) was filtered through a Sephadex ion-exchange column and frozen in liquid nitrogen (-196 degrees C). After thawing, there were more normal acrosomes in filtered spermatozoa than nonfiltered (P < 0.01). Post-thaw plasma membrane integrity and swelling ability in a hypoosmotic solution revealed that the filtered spermatozoa had a stronger (P < 0.005) plasma membranes than the nonfiltered. Filtered spermatozoa demonstrated higher zona-free hamster oocyte penetration than the nonfiltered (30.5 vs 11.5%; P < 0.0005). Spermatozoa extended in TEST-yolk without glycerol had the lowest (P < 0.001) normal acrosomes, intact plasma membranes and swelling ability. Plasma membrane over the post-acrosomal region of the head and post-midpiece region of the tail was more sensitive to damages caused by freezing and thawing than acrosomal and midpiece regions of spermatozoa. Glycerol in the extender provided significant (P < 0.05) protection to the sensitive regions of filtered and nonfiltered spermatozoa during freezing and thawing. Filtered plus glycerolated spermatozoa had the highest (P < 0.01) normal acrosomes, intact plasma membranes and swelling ability. In conclusion, the pre-freezing filtration of bovine semen harvested the spermatozoa possessing stronger plasma membranes which enabled them to endure freezing and thawing stresses. The addition of glycerol to the extender protected the post-acrosomal region of the head and post-midpiece region of the tail of spermatozoa from freezing and thawing shocks.

Role of sperm motility and acrosome integrity in the filtration of bovine semen

In this study, the role of sperm motility and acrosome integrity in filtration of bovine semen was investigated. In Experiment 1, the treatment of semen with formaldehyde, hyperosmotic buffer, heating and direct freezing immobilized the spermatozoa completely but their acrosomal status varied significantly (P < 0.01). The immotile spermatozoa, of any kind, did not pass through the Sephadex ion-exchange column at room temperature. In Experiment 2, semen samples possessing different percentages of immobilized spermatozoa (0, 50, 75 and 100%) were filtered through the Sephadex ion-exchange column. The immotile/dead spermatozoa were removed proportionately to their number in the semen by Sephadex ion-exchange column. The type and number of immotile spermatozoa in semen had no effect (P > 0.05) on the post-filtration recovery rate of motile spermatozoa. Filtered spermatozoa exhibited higher (P < 0.01) motility (> 90%), progressive motility (> 70%) and normal acrosomes (> 95%) than non-filtered spermatozoa. In conclusion, sperm motility seems to be more important than acrosome integrity for semen filtration, and the Sephadex ion-exchange column can remove the known quantities of different kinds dead/immotile spermatozoa.

Effect of filtration on post-thaw quality of bull semen

Semen from 4 Holstein bulls was diluted in 4 different extenders, filtered with Sephadex ion-exchange column, and frozen in liquid nitrogen. Sperm motility, progressive motility, path velocity, progressive velocity and the percentage of normal acrosomes of filtered and nonfiltered semen were recorded before and after freezing. Semen characteristics were significantly influenced by extender, filtration and freezing. Before and after freezing, motility measurements and the percentage of normal acrosomes were higher (P < 0.001) in filtered than in nonfiltered spermatozoa. Post-thaw recovery rate of motile spermatozoa was higher in filtered semen than nonfiltered (68 vs 39%, P < 0.0001). The reduction in motility, progressive motility and the percentage of normal acrosomes during freezing and thawing processes were significantly lower (P < 0.0001) in filtered semen (34, 34 and 4%, respectively) than nonfiltered (59, 54 and 15%, respectively). Post-thaw viability of spermatozoa was significantly affected by extender, filtration and time (P < 0.0001). Immediate (0 h) post-thaw motility of nonfiltered semen (29%) was similar to 4-h post-thaw motility of filtered semen (25%; P > 0.05). In conclusion, bull spermatozoa recovered by Sephadex ion-exchange filtration showed better post-thaw viability.

Efficacy of the Hamilton Thorn Motility Analyzer (HTM-2030) for the evaluation of bovine semen

Semen samples from four Holstein-Friesian bulls were evaluated by the Hamilton Thorn Motility Analyzer (HTM-2030) for sperm concentration, motility and other motion parameters. In the first trial, the extender preparation (P<0.005) and the program settings (P<0.001) of the motility analyzer significantly effected the accuracy of sperm concentration estimates. The student's t-test revealed that setting the variables on the HTM-2030 Analyzer according to the dimensions and brightness of bull spermatozoa and the background of the extender was better than using the settings for bull semen as recommended in the manufacturer's manual. In the second trial, different quantities of dead cells were added to semen samples to evaluate the accuracy of the HTM-2030 Analyzer for the estimation of percentage of motile cells and other motion characteristics. All motion parameter estimations except mean path velocity were similar for the settings studied. Addition of dead spermatozoa had a significant effect (P<0.0001) on all parameters of sperm movement. High correlation coefficients between the percentage of dead cells added and the decline in sperm motility verified the accuracy of this system. Use of the HTM-2030 system yielded simple, rapid and objective analysis of the studied spermatozoal parameters.

Post mortem studies on infertile buffalo bulls: testicular histology

Testicular tissues of 22 buffalo bulls (Bubalus bubalis) which suffered from three types of infertility were examined histologically. Nine bulls with no sexual libido showed underdeveloped seminiferous tubules; five of them also had various forms of germinal tissue hypoplasia (bilaterally complete, partial or incomplete) and in the other four the seminiferous tubules showed developed layers of germinal epithelium but no complete spermiogenesis. Among 11 bulls which had always produced poor quality semen one suffered from incomplete bilateral testicular hypoplasia and two had simple testicular degeneration; five showed marked testicular degeneration associated with fibrosis of intertubular spaces, and in three there was intertubular fibrosis and tubular stasis. In two bulls in which the quality of semen had deteriorated one showed bilateral partial testicular hypoplasia and the other had bilateral testicular degeneration with unilateral intertubular fibrosis and tubular stasis.

Post mortem studies on infertile buffalo bulls: anatomical and microbiological findings

Twenty-two buffalo bulls suffering from three different types of infertility were slaughtered and used for this study. Except for the reproductive system, no signs of localised or generalised disease were observed. Microbiological investigations were negative for brucellosis, vibriosis, mycoplasma and other non-specific microorganisms. Nine bulls with type 1 infertility had low bodyweights and underdevelopment of testes, accessory sex glands and endocrine glands. This picture suggests a total dysfunction of the pituitary-growth-gonadal axis. One bull of this type also showed bilateral epididymitis. Four out of 11 bulls with type 2 infertility had low bodyweights and most suffered from underdevelopment of testes, accessory sex glands and endocrine glands. Six bulls of this type had lesions of either epididymitis or orchitis or both. Two of these animals showed adhesions of periorchitis. One also showed seminal vesiculitis. In two bulls with type 3 infertility, bodyweights, reproductive organs and endocrine glands were normal. In later life, they yielded poor quality semen. Semen samples collected a few months before slaughter from nine bulls with type 2 and type 3 infertility were of poor quality and had higher percentages of abnormal spermatozoa in most cases.