Alpha-tocopheryl Succinate in Extender Improves the Post Thaw Quality of Water Buffalo Spermatozoa.

BACKGROUND: Alpha-tocopheryl succinate, a major chain-splitting antioxidant, is the most effective form of vitamin E and may be used in the semen extender for cryopreservation of buffalo spermatozoa. OBJECTIVE: To use different concentrations of alpha-tocopheryl succinate (T1, 0.3 mM, T2, 0.6 mM, and T3, 0.9 mM) and control (0.0 mM) in extender for dose optimization and hence improve the frozen-thawed quality of water buffalo spermatozoa. MATERIALS AND METHODS: Semen samples were collected from three mature buffalo bulls with artificial vagina (42°C) and this study was replicated for five times. Semen was cryopreserved by conventional method which included filling of semen per experimental treatment into 0.5 mL French straws, sealing with polyvinyl alcohol powder and keeping them 5 cm above the liquid nitrogen vapors for 12 min and storing in liquid nitrogen tank. Frozen-thawed semen was also processed for total antioxidant capacity content (TAC) and lipid peroxidation (LPO) level by thiobarbituric acid (TBA). Computer-assisted semen analysis (CASA) and other assays were also performed. RESULTS: TAC levels were higher (P<0.05) with T2 and T3 as compared to T1 and control. LPO levels were lower (P<0.05) with T2 and T3 as compared to T1 and control. Sperm progressive motility (%) and rapid velocity (%) were higher (P<0.05) with T2 and T3 as compared to control. The extender containing T3 had higher (P<0.05) sperm average path velocity (µm/s) and straight line velocity (µm/s) as compared to control. At 1 and 2 h incubation period (37 °C) T2 and T3 in extenders had higher (P<0.05) progressive motility and rapid velocity compared to control. Sperm supra vital plasma membrane integrity (%), mitochondrial transmembrane potential (%), viable and intact acrosome (%) and DNA integrity (%) were higher (P<0.05) with T2 and T3 as compared to T1 and control, respectively. CONCLUSION: The supplementation of alpha-tocopheryl succinate in extender, either at 0.6 (T2) or 0.9 (T3) mM concentrations improves the post thaw quality of water buffalo spermatozoa by sustaining the TAC levels and keeping the LPO levels lower as compared to the control. It is suggested that future study should be aimed to explore the influence of these optimal concentrations of alpha-tocopheryl succinate on in vivo fertility of buffalo bull spermatozoa.

Superoxide Dismutase in Extender Improves the in vitro Quality and in vivo Fertility of Cryopreserved Water Buffalo (Bubalus bubalis) Spermatozoa.

BACKGROUND: Superoxide dismutase (SOD) as an antioxidant in semen extender may be used for the cryopreservation of buffalo spermatozoa and in vivo fertility. OBJECTIVE: This study was aimed to evaluate the effects of SOD (SOD1, 100 IU/mL; SOD2, 200 IU/mL; SOD3, 300 IU/mL) and control (0.0) in Tris citric acid extender on in vitro quality and in vivo fertility of cryopreserved water buffalo bull spermatozoa. MATERIALS AND METHODS: Semen collection was carried out on a weekly basis (four bulls, three replicates, and n = 24 ejaculates). The conventional freezing of semen loaded straws (0.5 mL) was undertaken by placing them horizontally on a steel rack inside a Styrofoam box for 10 min containing liquid nitrogen (LN2) vapours, and plunging into a liquid nitrogen tank (-196 °C) for storage, followed by thawing at 37 °C for 30 s and analysis by computer-assisted sperm analyzer (CASA) and other assays. RESULTS: At post-dilution, the acrosome integrity (ACR-I, %) was significantly improved (P < 0.05) in extender supplemented with SOD3 as compared to other experimental groups. In addition, DNA integrity (DNA-I, %) was significantly higher (P < 0.05) in SOD1 and SOD3 compared to SOD2 and control. At post-thawing, the mean values of sperm progressive motility (PM, %), average path velocity (VAP, µm/s) and straight line velocity (VSL, µm/s) were significantly higher (P < 0.05) in extender supplemented with SOD3 compared to the control. At post-thawing, mean values of subjective motility (SM, %), plasma membrane integrity (PMI, %) and ACR-I were significantly higher (P < 0.05) in extender supplemented with SOD3 compared to the control. At post-thawing, sperm DNA-I was significantly higher (P < 0.05) in extender supplemented with all SOD doses compared to the control in a dose-dependent manner. The in vivo fertility rate (%) was significantly higher with SOD3 compared to the control (68.2 % vs. 49.5 %). CONCLUSION: The supplementation of SOD3 (300 IU/mL) in Tris citric acid extender improves both in vitro quality and in vivo fertility of buffalo bull spermatozoa.

Effect of EDTA as Chelating Agent in Extender on the Post Thaw Quality of Buffalo Bull Spermatozoa.

BACKGROUND: Spermatozoa are prone to mechanical and biochemical stresses upon freezing. The influx of Ca++ causes early capacitation and production of reactive oxygen species. OBJECTIVE: To evaluate the effect of ethylenediaminetetraacetic acid (EDTA) as a calcium chelator in a semen extender. MATERIALS AND METHODS: The effect of EDTA concentrations (0%, 0.1%, 0.2% and 0.3%) on the post thaw quality of buffalo bull spermatozoa were studied. RESULTS: The extender with 0.2% EDTA improved significantly visual motility, progressive motility and plasma membrane integrity. Sperm kinematics, such as beat cross frequency (BCF), curved line velocity (VCL), straight line velocity (VSL) and average path velocity (VAP), were higher in the extender with 0.2% EDTA. EDTA at 0.2% improves semen parameters (visual motility, supra vital plasma membrane integrity, chromatin integrity and percentage viable spermatozoa with intact acrosome. CONCLUSION: The EDTA supplementation in a semen extender improves the post-thaw quality of Nili-Ravi buffalo bull semen.

Effect of Cryopreservation on Casa Characteristics, Mitochondrial Transmembrane Potential, Plasma and Acrosome Integrities, Morphology and in vivo Fertility of Buffalo Bull Spermatozoa.

BACKGROUND: Application of frozen-thawed semen is an important tool for improving the vivo fertility, but the process of freezing and thawing causes significant damage to spermatozoa. OBJECTIVE: The aim of this study was to evaluate the effect of cryopreservation on CASA characteristics, mitochondrial transmembrane potential, plasma, and acrosome integrities, morphology and in vivo fertility of buffalo bull spermatozoa. MATERIALS AND METHODS: Semen was collected from four mature buffalo bulls with artificial vagina at 42 °C. Ejaculates having > 1 mL volume, > 60 % sperm visual motility and > 0.5 x 109 sperm/mL concentration from each bull were diluted in Tris-citric acid egg yolk glycerol extender (TCA) making two aliquots per bull for analysis at post dilution and cryopreserved respectively. RESULTS: Analysis of variance (ANOVA) showed that the process of freezing and thawing significantly reduced (P < 0.05) CASA characteristics including total motility (TM, %), progressive motility (PM, %), rapid velocity (RV, %), average path velocity (VAP, µm/sec), straight line velocity (VSL, µm/sec), curvilinear velocity (VCL, µm/sec), beat cross frequency (BCF, Hz), straightness (STR, %) and linearity (LIN, %). Furthermore, the process of freezing and thawing significantly reduced (P < 0.05) subjective motility (SM, %), Supra-vital plasma membrane integrity (SVPMI, %), high mitochondrial membrane potential (HMMP, %), viable spermatozoa with intact acrosome (V/IACR, %). Moreover, it was observed that the freezing thawing process significantly decreased the in vivo fertility (%, 50.35 % vs. 61.39 %; P < 0.05) as compared to post diluted semen. CONCLUSION: It is concluded that the process of freezing and thawing significantly reduced semen quality and in vivo fertility of buffalo bull in terms of various functional parameters.

Cryoprotectant effect of trehalose in extender on post-thaw quality and in vivo fertility of water buffalo (Bubalus bubalis) bull spermatozoa.

This study was designed to ascertain the cryoprotectant effects of different concentrations of trehalose [0 (T0), 25 (T25), 35 (T35), 45 (T45) mm], egg yolk [20% (E20), 15% (E15) v/v] and glycerol [7% (G7), 5% (G5) v/v] in Tris-citric acid-based extender on post-thaw quality and in vivo fertility of buffalo bull spermatozoa. Twenty-five ejaculates were collected from five bulls and split into four parts. After that, the split ejaculates from each of the bull were diluted either in T0E20G7 (control) or T25E20G5 or T35E15G5 or T45E15G5 extender. Finally, the sperm suspension was frozen in 0.54-ml French straws. Post-thaw sperm total motility (%), progressive motility (%), rapid velocity (%), average path velocity (µm/s), straightline velocity (µm/s), curvilinear velocity (µm/s), linearity (%), plasma membrane and acrosome integrities (%) were higher (p < .05) in T45E15G5 extender as compared to other treatment groups and control. The fertility rate (56.8% versus 41.3%) was higher (p < .05) in buffaloes inseminated with semen doses cryopreserved in extender containing T45E15G5 combination of cryoprotectants than the control. In conclusion, addition of 45 mm trehalose along with 15% egg yolk and 5% glycerol in extender improves the post-thaw quality and in vivo fertility of buffalo bull spermatozoa.

Use of post-thaw semen quality parameters to predict fertility of water buffalo (Bubalus bubalis) bull during peak breeding season.

This study was designed to predict the fertility of water buffalo bull using post-thaw semen quality parameters during peak breeding season. Thirty ejaculates were collected from five bulls with artificial vagina and cryopreserved. At post-thaw, semen was analysed for motility parameters, velocity distribution, kinematics, DNA integrity/fragmentation, viability, mitochondrial transmembrane potential, morphology, plasma membrane and acrosome integrity. Data of 514 inseminations were collected for estimation of in vivo fertility. Pearson's correlation coefficients showed that progressive motility (PM), rapid velocity, average path velocity, straight line velocity, straightness, supravital plasma membrane integrity, viable spermatozoon with intact acrosome or with high mitochondrial activity were correlated with in vivo fertility (r = .81, p < .01; r = .85, p < .01; r = .64, p < .05; r = .73, p < .05; r = .57, p < .05; r = .88, p < .01; r = .84, p < .01 and r = .81, p < .01 respectively). Step forward multiple regression analysis showed that the best single predictor of fertility was PM. However, combinations of semen quality parameters to predict fertility were better as compared to single parameter. In conclusion, fertility of buffalo bull can be predicted through some of the post-thaw in vitro semen quality tests during peak breeding season.

Programmable fast-freezing method improves the post-thaw motion dynamics, integrities of plasmalemma, mitochondrial transmembrane, DNA and, acrosome, and in vivo fertility of water buffalo (Bubalus bubalis) spermatozoa.

The effects of freezing methods (FR1, nonprogrammable/static, 5 cm above liquid nitrogen [LN2 ] for 10 min, plunging in LN2 ; FR2, programmable medium, +4°C to -15°C at 3°C min-1 , from -15 to -80°C at 10°C min-1 and final holding for 1 min at -80°C, plunging in LN2 ; FR3, programmable fast, from initial holding at +4°C for 2 min, from +4°C to -20°C at 10°C min-1 , from -20°C to -100°C at 30°C min-1 , final holding for 1 min at -100°C and plunging in LN2 ) were assessed on post-thaw in vitro quality and in vivo fertility of water buffalo spermatozoa. Mean sperm progressive motility (%), rapid velocity (%), average path velocity (µm s-1 ), straight line velocity (µm s-1 ), curved line velocity (µm s-1 ), integrities (%) of plasmalemma, mitochondrial transmembrane, DNA and acrosome were higher (p < .05) in samples cryopreserved with FR3 compared to FR1 and FR2. Similarly, in vivo fertility (%) of buffalo spermatozoa was higher (p < .05) with FR3 than FR1 (%; 68.0 versus 50.0). We concluded that programmable fast-freezing method (FR3) improves the post-thaw in vitro quality and in vivo fertility of water buffalo spermatozoa.

Freezability of water buffalo bull (Bubalus bubalis) spermatozoa is improved with the addition of curcumin (diferuoyl methane) in semen extender.

Effects of curcumin as antioxidant in extender were evaluated on freezability of buffalo spermatozoa. Semen from each of the five bulls (n = 3 replicates, six ejaculates/bull, a total of 30 ejaculates) was diluted in Tris-citric acid extender containing curcumin (0.5, 1.0, 1.5 or 2.0 mM) or control. At pre-freezing and post-thawing, total antioxidant contents (µM/L) and lipid peroxidation levels (µM/ml) were higher (p < .05) and lower (p < .05) respectively, with 1.5 and 2.0 mM compared to 0.5 and 1.0 mM curcumin and control. At post-thawing, progressive motility (PM, %) and rapid velocity (RV, %) were higher (p < .05) with 1.5 mM compared to other doses of curcumin and control (except in case of RV, 1.5 was similar with 1.0 mM). Kinematics (average path velocity, µm/s; straight-line velocity, µm/s; curved-line velocity, µm/s; straightness, %; linearity, %), in vitro longevity (%, PM and RV) and DNA integrity (%) at post-thawing were higher (p < .05) with 1.5 mM compared to control. At post-thawing, supravital plasma membrane integrity (%) and viable spermatozoa with intact acrosome (%) were higher with 1.5 compared to 2.0 mM curcumin and control. We concluded that freezability of water buffalo spermatozoa is improved with the addition of 1.5 mM curcumin in extender.

Effect of equilibration times, freezing, and thawing rates on post-thaw quality of buffalo (Bubalus bubalis) bull spermatozoa.

The effects of equilibration times (E1, 2 h; E2, 4 h; E3, 6 h), freezing rates (FR1, manual, 5 cm above liquid nitrogen (LN2 ) for 10 min, plunging in LN2 ; FR2, programmable ultra-fast, holding at +4 °C for 2 min, from 4 to -10 °C at -10 °C/min, from -10 to -20 °C at -15 °C/min, from -20 to -120 °C at -60 °C/min, holding at -120 °C for 30 sec, plunging in LN2 ), and thawing rates (T1, 37 °C for 30 sec; T2, 50 °C for 15 sec; T3, 70 °C for 7 sec) were evaluated on quality of buffalo bull spermatozoa. Progressive motility (%), rapid velocity (%), average path velocity (VAP, µm/s), straight line velocity (VSL, µm/s), and mitochondrial transmembrane potential (%) were higher (p < 0.05) with E2, FR2, and T3 compared to other groups. Sperm curved line velocity (VCL, µm/s) was higher (p < 0.05) with E2 and FR2 compared to other groups. Sperm straightness (%) and linearity (LIN, %) were higher (p < 0.05) with E2 compared to other groups. Sperm LIN was affected (p < 0.05) with T3 compared to other groups. Supravital-plasma membrane integrity (%), viability and acrosome integrity (%) of spermatozoa were higher (p < 0.05) with E2 and FR2 compared to other groups. Sperm DNA integrity (%) was higher (p < 0.05) with FR2 and T1 compared to other groups. We concluded that inclusion of 4 h-equilibration time, programmable ultra-fast freezing rate, and rapid thawing at 70 °C for 7 sec in cryopreservation protocol improves the post-thaw quality of buffalo bull spermatozoa.

Isolation of bacteria in semen and evaluation of antibiotics in extender for cryopreservation of buffalo (Bubalus bubalis) bull spermatozoa.

This study was designed to investigate the occurrence of bacterial species in water buffalo semen at the time of collection/processing and to assess the efficacy of some selected antibiotics (GTLS; gentamycin, tylosin and linco-spectin or SP; streptomycin and penicillin) in cryodiluent on bacterial control and quality including in vivo fertility of buffalo spermatozoa. For this purpose, four experiments were conducted. In experiment 1, a total of 11 bacterial species were isolated from buffalo ejaculates. In experiment 2, total aerobic bacterial counts at post dilution and thawing were lower (P < 0.05) in GTLS than in SP or control. The majority of the bacterial isolates from ejaculates were more susceptible to GTLS than SP. In experiment 3, sperm acrosome integrity was higher (P < 0.05) in GTLS and SP compared to control. In experiment 4, the in vivo fertility results for GTLS were higher (P < 0.05) than that for SP. In conclusion, a number of bacterial species were isolated from the bubaline semen, which requires an efficient control before its use in artificial insemination program. The GTLS combination of antibiotics may be incorporated into a freezing extender/protocol without compromising the post-thaw quality and in vivo fertility of buffalo bull spermatozoa.

l-Cysteine improves antioxidant enzyme activity, post-thaw quality and fertility of Nili-Ravi buffalo (Bubalus bubalis) bull spermatozoa.

The effects of l-cysteine in extender on antioxidant enzymes profile during cryopreservation, post-thaw quality parameters and in vivo fertility of Nili-Ravi buffalo bull spermatozoa were studied. Semen samples from 4 buffalo bulls were diluted in Tris-citric acid-based extender having different concentrations of l-cysteine (0.0, 0.5, 1.0, 2.0 and 3.0 mm) and frozen in 0.5-ml French straws. The antioxidative enzymes [catalase, super oxide dismutase and total glutathione (peroxidase and reductase)] were significantly higher (P < 0.05) at pre-freezing and post-thawing in extender containing 2.0 mm l-cysteine as compared to other groups. Post-thaw total motility (%), progressive motility (%), rapid velocity (%), average path velocity (µm s-1 ), straight line velocity (µm s-1 ), curvilinear velocity (µm s-1 ), beat cross frequency (Hz), viable spermatozoa with intact plasmalemma (%), acrosome and DNA integrity (%) were higher with the addition of 2.0 mm l-cysteine as compared to other groups (P < 0.05). The fertility rates (59 versus 43%) were higher (P < 0.05) in buffaloes inseminated with doses containing 2.0 mm of l-cysteine than in the control. In conclusion, the addition of 2.0 mm l-cysteine in extender improved the antioxidant enzymes profile, post-thaw quality and in vivo fertility of Nili-Ravi buffalo bull spermatozoa.

Efficiency of ciprofloxacin for bacterial control, post-thaw quality, and in vivo fertility of buffalo spermatozoa.

Ciprofloxacin (CP) was evaluated for bacterial control, post-thaw quality, and fertility of buffalo semen. Pseudomonas aeruginosa, Escherichia coli, Proteus sp., Corynebacterium sp., Micrococcus sp., and Staphylococcus sp. were isolated from buffalo semen. Pseudomonas aeruginosa, Corynebacterium sp., and Micrococcus sp. were resistant to streptomycin, whereas P. aeruginosa and Proteus sp. were resistant to penicillin. All bacteria were susceptible to CP. In vitro dose toxicity was assessed in sodium citrate buffer containing 0, 200 to 2000 µg/mL of CP. CP up to 1000 µg/mL was found nontoxic to motility and viability of buffalo sperm. For post-thaw quality, buffalo semen was frozen in Tris-citric acid extender containing streptomycin-penicillin (SP; 1000 µg/mL-1000 IU/mL) or CP 600 µg/mL and was assessed for total aerobic bacterial count (post-thaw), motility, plasma membrane integrity, viability at 0, 2, and 4 hours post-thaw. At 4 hours post-thaw, plasma membrane integrity (%) was higher (P < 0.05) in extender containing CP than SP. Total aerobic bacterial count was 0.00 in extender containing CP compared with 0.07 × 10(4) cfu/mL with SP. To assess the in vivo fertility rate, semen (two bulls) frozen in Tris-citric acid extender containing SP or CP was used to inseminate, and 400 inseminations (200/group) were recorded. Higher (P ≤ 0.05) fertility rate was recorded with CP (55%) compared with SP (41%). In conclusion, use of CP in extender was efficient to control the bacterial contamination without compromising the post-thaw quality and fertility of cryopreserved water buffalo bull semen.

Soya-lecithin in extender improves the freezability and fertility of buffalo (Bubalus bubalis) bull spermatozoa.

Egg yolk is routinely used as a cryoprotectant in semen extenders. However, it may contain cryoprotective antagonists, and there are hygienic risks associated with its use. Proteins of plant origin, like soya-lecithin, lack these hazards. The aim of this study was to use soya-lecithin as a cryoprotectant in extender and to investigate its effects on in vitro quality and in vivo fertility of buffalo semen. Semen from three buffalo bulls was frozen in tris-citric extender containing 5.0%, 10% or 15% soya-lecithin or 20% egg yolk. Sperm motility, plasma membrane integrity and viability were assessed post-dilution, pre-freezing and post-thaw. In Post-dilution and pre-freezing, the values for motility, plasma membrane integrity and viability remained higher (p ≤ 0.05) in extenders containing 10% soya-lecithin and control compared with extender containing 5% and 15% soya-lecithin. However, motility, plasma membrane integrity and viability were higher (p < 0.05) in extender containing 10% soya-lecithin compared with control and extenders containing 5% and 15% soya-lecithin. Semen from two buffalo bulls was frozen in tris-citric extender containing either 10% soya-lecithin or 20% egg yolk. Higher (p < 0.05) fertility rate was recorded in buffaloes inseminated with semen containing 10% soya-lecithin (56%) compared with 20% egg yolk (41.5%). The results suggest that 10% soya-lecithin in extender improves the freezability and fertility of buffalo bull spermatozoa and can be used as an alternate to egg yolk in cryopreservation of buffalo semen.

Effect of low density lipoproteins in extender on freezability and fertility of buffalo (Bubalus bubalis) bull semen.

This study was designed to determine whether low-density lipoporoteins (LDLs) extracted from egg yolk in extender improve the freezability and fertility of buffalo bull semen. Semen from three Nili-Ravi buffalo bulls was diluted at 37 °C with tris-citric acid extender (50 × 10(6) motile spermatozoa mL(-1)) containing LDLs 2.5%, 5%, 10%, and 15% extracted from egg yolk and extender containing 20% egg yolk was kept as control. Diluted semen was cooled to 4 °C in 2 h, equilibrated at 4 °C for 4 h, filled in 0.5 mL French straws, and kept on liquid nitrogen vapors for 10 min. Straws were then plunged and stored in liquid nitrogen (-196 °C). Sperm motility (visually; %), plasma membrane integrity (%; with supravital hypo-osmotic swelling test), and viability (%; with dual staining test using Trypan-blue Giemsa) were assessed at post-dilution, pre-freezing and post-thawing. At post-dilution and pre-freezing, sperm progressive motility, plasma membrane integrity and viability was similar (P > 0.05) in extender containing 10% LDLs or the control. However, at post-thaw the aforementioned parameters were higher (P < 0.05) in extender containing 10% LDLs compared with the control and other experimental extenders. The fertility rate of inseminations performed were higher (P < 0.05) with extender containing 10% LDLs than the control. It was concluded that LDLs (10%) in extender improved the freezability and fertility of buffalo bull spermatozoa.

In vitro evaluation of liquid-stored buffalo semen at 5°C diluted in soya lecithin based extender (Bioxcell®), tris-citric egg yolk, skim milk and egg yolk-citrate extenders.

This study was designed to compare the quality of liquid-stored buffalo bull spermatozoa in soya lecithin based extender Bioxcell(®) (BIOX), milk (MILK), tris-citric egg yolk (TEY) and egg yolk-citrate (EYC) extender at 5°C. Semen was collected from five Nili-Ravi buffalo (Bubalus bubalis) bulls of 6-7 years of age with artificial vagina over a period of 3 weeks (two consecutive ejaculates once in a week). Semen ejaculates having more than 60% motility were pooled, split into four aliquots, diluted (37°C; 10 × 10(6) motile spermatozoa/ml), cooled from 37 to 5°C in 2 h (0.275°C/min) and stored for 5 days. Sperm motility, viability, plasma membrane integrity (PMI) and normal acrosomal ridge were studied at first, third and fifth day of storage. Higher values of progressive sperm motility (%), sperm viability (%), sperm PMI (%) and normal apical ridge (%) were observed in BIOX, MILK and TEY extenders at first, third and fifth day of storage than EYC extender. Progressive sperm motility, sperm viability and sperm PMI in BIOX(®) extender were not different from MILK and TEY extenders at 1st and third day storage period. However, at fifth day of storage, the values for these parameters remained significantly higher (p<0.05) in BIOX(®) compared with MILK, TEY and EYC extenders. At fifth day of storage, the semen quality parameters for Bioxcell(®) were comparable to those with MILK and TEY extenders at third day of storage. In conclusion, motility, viability and PMI of buffalo bull spermatozoa remained similar in Bioxcell(®) , milk and TEY extender at first and third days of storage at 5°C. Yet, the values for the aforementioned parameters in Bioxcell(®) were higher compared with milk, TEY and EYC extender at fifth day of storage at 5°C.

Cryopreservation of buffalo (Bubalus bubalis) semen in Bioxcell extender.

This study was designed to compare commercially available extender Bioxcell with tris-citric egg yolk extender for post thaw quality and in vivo fertility of buffalo semen. For comparison of post thaw semen quality: semen was collected from five adult Nili-Ravi buffalo (Bubalus bubalis) bulls of similar age group with artificial vagina (at 42 degrees C) for three weeks (replicates). Qualifying ejaculates having motility >60% from each buffalo bull were divided in two aliquots and diluted (at 37 degrees C having 50 x 10(6) spermatozoa/ml) in tris-citric egg yolk or Bioxcell extender. Diluted semen was cooled to 4 degrees C in 2 hours, equilibrated for 4 hours and filled in 0.5 ml straws. Semen straws were kept over liquid nitrogen vapors (5 cm) for 10 minutes. Straws were then plunged and stored in liquid nitrogen (-196 degrees C). After 24 hours of storage, semen straws were thawed at 37 degrees C for 30 seconds to assess sperm motility, viability, plasma membrane integrity, normal apical ridge, and abnormalities (head, mid piece, and tail). For comparison of in vivo fertility: semen from two buffalo bulls of known fertility was cryopreserved in tris-citric egg yolk and Bioxcell as described earlier, and used for inseminations under field conditions. Post-thaw percentage of sperm motility (45.3 +/- 1.1, 45.0 +/- 1.4), viability (66.2 +/- 1.1, 64.4 +/- 1.3) plasma membrane integrity (60.4 +/- 1.2, 59.2 +/- 1.4) and normal apical ridge (82.9 +/- 0.5, 80.7 +/- 0.5) did not differ (P > 0.05) in tris-citric egg yolk and Bioxcell extender, respectively. Similarly, sperm abnormalities of head (1.20 +/- 0.1, 1.20 +/- 0.1), mid piece (0.67 +/- 0.1, 0.87 +/- 0.1) and tail (11.7 +/- 0.2, 11.6 +/- 0.3) remained similar (P > 0.05) in tris-citric egg yolk and Bioxcell extender, respectively. In vivo fertility rates of buffalo semen cryopreserved in tris-citric egg yolk and Bioxcell also remained similar (44% vs. 47%). It is concluded that commercially available Bioxcell may be used for the cryopreservation of buffalo semen with an equal efficiency to tris-citric egg yolk extender.

Factors affecting the quality of cryopreserved buffalo (Bubalus bubalis) bull spermatozoa.

Storage of buffalo (Bubalus bubalis) bull semen in the cryopreserved state is discussed in this article. Fertility rate in buffalo following artificial insemination with frozen-thawed semen is reviewed. To better understand the freezability of bubaline spermatozoa, the available data on biochemical components and the activity of specific enzymes of semen/spermatozoa are given. Moreover, the major factors that may influence the post-thaw viability and fertility of buffalo spermatozoa are examined in detail. In addition, suggestions for improvement in cryogenic procedures for buffalo spermatozoa are also given.

Duck egg yolk in extender improves the freezability of buffalo bull spermatozoa.

We investigated the use of duck egg yolk (DEY), Guinea fowl egg yolk (GFEY) and Indian indigenous hen (Desi) egg yolk (IDEY) in extender for improving the post-thaw quality of buffalo (Bubalus bubalis) bull spermatozoa, and compared it with commercial hen egg yolk (CHEY; control). For this purpose, two consecutive ejaculates of semen from each of two Nili-Ravi buffalo bulls were collected on 1 day each week for 5 weeks (replicates; n=5) with artificial vagina (42 degrees C). Split pooled ejaculates, were diluted in tris-citric acid glycerol extender containing either DEY or GFEY or IDEY or CHEY at 37 degrees C. Extended semen was cooled to 4 degrees C in 2 h and equilibrated for 4 h at 4 degrees C. Cooled semen was then filled in 0.5 ml straws at 4 degrees C and frozen in programmable cell freezer. Thawing of semen was performed at 37 degrees C for 30 s. Sperm motility, plasma membrane integrity and sperm morphology (acrosome integrity, head, mid-piece and tail abnormalities) of each semen sample were assessed at 0, 3 and 6 h after thawing and incubation at 37 degrees C. Visual motility (%) and percentage of intact plasma membranes assessed at 6h post-thaw of buffalo bull spermatozoa were highest (P<0.05) due to DEY as compared to GFEY, IDEY and control. The percentage of spermatozoa with normal acrosomes at 0, 3 and 6 h post-thaw was highest (P<0.05) in DEY extender than GFEY, IDEY and CHEY. Sperm tail abnormalities (%) observed at 0, 3 and 6 h post-thaw in samples cryopreserved with freezing extender having DEY were lower (P<0.05) as compared to extender containing GFEY, IDEY and CHEY. In conclusion, DEY compared to other avian yolks in extender improves the frozen-thawed quality of buffalo bull spermatozoa.

Mammalian sperm chromatin structure and assessment of DNA fragmentation.

This review article illustrates the biology of mammalian sperm chromatin structure. The possible causes of DNA (deoxyribonucleic acid) fragmentation are discussed. Also available molecular techniques for assessment of mammalian sperm DNA damage are described.

A review on reproductive biotechnologies for conservation of endangered mammalian species.

This review describes the use of modern reproductive biotechnologies or assisted reproductive techniques (ART) including artificial insemination, embryo transfer/sexing, in vitro fertilization, gamete/embryo micromanipulation, semen sexing, genome resource banking, and somatic cell nuclear transfer (cloning) in conservation programs for endangered mammalian species. Such biotechnologies allow more offspring to be obtained from selected parents to ensure genetic diversity and may reduce the interval between generations. However, the application of reproductive biotechnologies for endangered free-living mammals is rarer than for endangered domestic breeds. Progress in ART for non-domestic species will continue at a slow pace due to limited resources, but also because the management and conservation of endangered species is biologically quite complex. In practice, current reproductive biotechnologies are species-specific or inefficient for many endangered animals because of insufficient knowledge on basic reproduction like estrous cycle, seasonality, structural anatomy, gamete physiology and site for semen deposition or embryo transfer of non-domestic species.