scholarly journals Ram Semen Cryopreservation Using Egg Yolk or Egg Yolk-free Extenders: Preliminary Results

2019 ◽  
Vol 50 (2) ◽  
pp. 96-103
Author(s):  
M. Ptáček ◽  
M. Stádníková ◽  
F. Savvulidi ◽  
L. Stádník

Abstract Kinematic parameters of thawed ram semen frozen under field conditions were analysed with the use of two commercial (egg yolk vs egg yolk free) semen extenders in different year-seasonal periods. The semen was collected from Suffolk (n = 2) and Charollais (n = 1) rams kept in private breeding farm on 3 test days (pre-mating, at mating, post mating) during year 2016. Two commercial semen extenders (egg yolk-based BullXcell® or egg yolk-free AndroMed®) were used for semen processing. Processed semen was frozen in 0.25 ml plastic cryostraws using the custom-made portable freezing box for ram semen cryopreservation under field conditions. Thawed semen characteristics were evaluated using computer-assisted semen analysis (CASA) system immediately after thawing and after 2 h of heat incubation (±38°C). Significantly higher total motility (+12.3%), straight line velocity (+5.6 μm s−1), and average-path velocity (+6.9 μm s−1) were detected for the semen processed and cryopreserved using egg yolk-based semen extender. Year-seasonal variation and introducing the ram to service had shown to have a significant effect on the cryopreserved ram spermatozoa. These preliminary results confirmed the feasibility of ram semen processing and cryopreservation under field conditions.

2006 ◽  
Vol 18 (2) ◽  
pp. 151
Author(s):  
M. E. Carini ◽  
R. Cavia ◽  
G. Larraburu ◽  
G. M. Brogliatti

Currently, cryopreservation process of fresh bull semen is carried out between 3 and 6 hours of refrigeration at 4°C post-collection (Hafez, 1989). However, it is sometimes difficult when the cryopreservation process is not available at the site of collection. The objective of this study was to determine seminal motility and viability in samples maintained at 4°C during 24 hours. A total of 98 ejaculates from 23 adult bulls (Angus, Brangus, Braford and Hereford) were collected and diluted in a semi-defined semen extender (Andromed, Minitüb, Tiefenbach, Germany) and stored at 4°C. Parameters of velocity average path (VAP, µm/s), velocity straight line (VSL, μm/s), amplitude lateral head (ALH, μm), linearity (LIN, %), percentage of rapid cells (RAPID, %), percentage of slow and static cells (SL/ST, %), and viability (VIA, %) were determined by Computer Assisted Semen Analysis (CASA, HTM-ceros 12.1, Berkeley, CA, USA). Measurements were done at 6, 9, 12, and 24 h. The obtained results were analyzed statistically with one-way ANOVA and Dunnet Multiple Comparison Test and are summarized in Table 1. There were no significant differences (P > 0.05) in the VAP, RAPID, or SL/ST during 24 h of storage at 4°C. Measurements were significantly different (P < 0.01) for VSL and VIA at 24 h. Measurements of ALH were increased from 12 h (P < 0.01) and consequently, LIN decreased at the same time (P < 0.01). These results suggest that there are no differences in velocity, except in VSL at the end of the storage time. The type of movement of the spermatozoa change, because ALH increases and the trajectory loses linearity. A decrease in viability suggests that from 24 h of storage, the membrane of the spermatozoa becomes more susceptible. More research needs to be done to evaluate the competence of this time-storage semen in the artificial insemination trial. Table 1. Parameters of motility and viability of semen maintained at 4°C during 24 h This research was supported by Centro Genético Bovino de EOLIA S.A.


2006 ◽  
Vol 18 (2) ◽  
pp. 150
Author(s):  
G. M. Brogliatti ◽  
G. Larraburu ◽  
R. Cavia ◽  
M. E. Carini

The process of cryopreservation of bull semen in liquid nitrogen at −196°C is usually carried out after 3 to 6 h of refrigeration at 4°C post-collection. To guarantee the quality of the final product, the frozen straws are evaluated after cryopreservation. The seminal samples are usually stabilized during 48 h before being analyzed (Hafez, Reproduction and Artificial Insemination in Animals, 1989); this would retard the possible commercialization. The objective of the present study was to determine motility parameters and viability of semen doses stabilized by 1 h or more than 48 h in liquid nitrogen at −196°C. A total of 122 ejaculated from 23 different adult bulls (Angus, Brangus, Braford, and Hereford) were evaluated in an artificial insemination center between January and April 2005. The semen was diluted in a semi-defined semen extender (Andromed, Minitub, Germany) and frozen in an automatic freezer (Digicool, IMV, France). Parameters of velocity average path (VAP, μm/s), velocity straight line (VSL, µm/s), amplitude lateral head (ALH, µm), linearity (LIN, %), percentage of rapid cells (RAPID, %), and viability (VIA, %) were determined by Computer Assisted Semen Analysis (CASA, HTM-ceros 12.1, Berkeley, CA, USA). The obtained results were analyzed statistically with T Student and are summarized in Table 1. The results indicate that there is no difference in the velocity of the spermatozoa evaluated 1 h or 48 h post-frozen. There is no difference in VAP, VSL, movement of amplitude lateral head (ALH), or linearity (LIN). The percentage of viable spermatozoa was not affected in either group. Statistical analysis indicates that there is no difference (P > 0.05) in any of the evaluated parameters. The results demonstrate that spermatic motility and viability of frozen bull semen could be evaluated before 48 h post-frozen. This allows reduction of the time between freezing and evaluation and immediate availability of the bull straws. Table 1. Parameters of motility and viability at 1 h vs. 48 h of post-frozen stabilization time This research was supported by Centro Genético Bovino EOLIA S.A.


2005 ◽  
Vol 17 (2) ◽  
pp. 156 ◽  
Author(s):  
G. Brogliatti ◽  
F. Garcia Migliaro ◽  
R. Cavia ◽  
G. Larraburu ◽  
A. Albrecht

The latest entry in the field of semen evaluation is computer assisted semen analysis (CASA). Its greatest advantages are elimination of the subjective nature of routine semen evaluation and the addition of detailed motion analysis unquantifiable by visual examination. The objective of this study was to evaluate CASA motility parameters of fresh bull semen collected by artificial vagina (AV) or electroejaculation (EE) from a total of 56 beef different bulls. Semen samples from a total of 45 beef bulls were collected by AV from winter to the end of spring (740 collections), and from 11 beef bulls by EE (120 collections) in the same period. First and second AV collections were analyzed as individual data. EE collection was performed only one. Means and standard deviations for each characteristic were calculated, compared, and statistically analyzed. A sample of the collection was diluted 1:20 in a semi-defined semen extender (Andromed, Minitüb, Tiefenbach, Germany) and held in a glass tube at 36°C for 5 min before analysis. The sample was loaded into 20-μm chambers, and six microscope fields from each chamber were analyzed. The following sperm motility parameters were determined with the Ceros 12.1 sperm analyzer (Hamilton Thorne Biosciences, Inc., Beverly, MA, USA) on at least 1000 spermatozoa:concentration (CONC), velocity average path (VAP), velocity straight line (VSL), curvilinear velocity (VCL), amplitude lateral head (ALH), beat cross frequency (BCF), straightness (STR), linearity (LIN), and percentage of rapid or statics cells. There were no significant differences (P > 0.05) in VAP, VSL, VCL, ALH, STR, LIN, and the percentage of rapid and static cells of semen collected by AV or EE. The concentration (sperm/mL) of the AV-collected sperm was significantly higher than for the sperm collected by EE. Results from the analysis indicate that semen collected by artificial vagina have motility characteristics similar to those collected by electroejaculation. More research needs to be done to evaluate motility parameters of frozen/thawed semen collected by electroejaculation and by artificial vagina. This research was supported by Centro Genético Bovino de EOLIA sa Argentina.


2007 ◽  
Vol 76 (4) ◽  
pp. 601-604 ◽  
Author(s):  
R. Kozdrowski ◽  
A. Dubiel ◽  
W. Bielas ◽  
M. Dzięcioł

The objective of the study was a comparison of two protocols of goat semen cryopreservation with the use of computer-assisted semen analysis system. Twenty ejaculates obtained with electroejaculation method were assessed. Each ejaculate was divided in half and frozen according to two protocols. In protocol I semen was centrifuged in order to remove its plasma and diluted in Tris buffer extender containing glucose, citric acid and glycerol with 20% addition of egg yolk. Protocol II did not include removal of plasma and the extender contained 1.5% egg yolk. It was shown that the removal of semen plasma improved motility of goat spermatozoa following freezing/thawing with respect to the following motility indicators: motility, average path velocity, amplitude of lateral head displacement at p < 0.05, and straight velocity, straightness and linearity at p < 0.01. In conclusion, the removal of semen plasma through centrifugation improved motility properties of goat semen following the freezing/thawing procedure.


2008 ◽  
Vol 20 (1) ◽  
pp. 161 ◽  
Author(s):  
C. Tamargo Miguel ◽  
S. S. Pérez-Garnelo ◽  
P. Beltrán Breña ◽  
A. T. Palasz ◽  
J. De la Fuente ◽  
...  

This experiment was designed to test the efficacy of 2 different preparation protocols of zwitteronic soyabean-origin lipids for the production of lipidsglycerol liposomes for use in bull semen cryopreservation. Lipids liposomes were prepared at 10% concentration in Tris buffer by 1. highpressure homogenization (Panda 2K, Parma, Italy) and then 8% glycerol were added, extender-1 (E-1); Lipids were homogenized together with glycerol, extender-2 (E-2). Bioxcell extender (E-3) was used as control. Semen was collected 3 times from 3 endangered Asturiana de la Monta�a bulls by the means of an artificial vagina. Ejaculates with at least 70% motility were processed further by a standard freezing protocol used in our AI station. Semen was diluted at 37�C with each of the 4 extenders to a concentration of 92 � 106 spermatozoa per mL, cooled to 4�C over 4 h, aspirated into 0.25-mL plastic straws (IMV Technologies, Aigle, France), frozen in a bio-freezer (IMV Technologies) in 3 steps from 4 to –140�C, and then plunged into liquid N2. Straws were thawed in a water bath at 37�C for 30 s. Sperm motility was analyzed microscopically immediately after collection, after dilution, and after 4, 24, 48, and 72 h of storage at 4�C. Post-thaw semen progressive motility was assessed microscopically, and sperm movement characteristics were analyzed by computer-assisted semen analysis (CASA) (SCA�, Microptic, Barcelona, Spain). Data were compared between extenders and bulls by 2-way ANOVA; percentages were transformed by arcsine transformation before ANOVA. Total and progressive sperm motility at 0 h after dilution ranged from 90 to 70% and was not different between extenders and bulls. There was no difference between bulls in total and progressive motility after 24 h of cold storage; however, both were significantly greater (P < 0.05) for Control (62.4 � 14.7 and 41.4 � 14.9) and E-1 (70.1 � 12 and 33.8 � 7.0) extenders than for the E-2 extender (22.5 � 17 and 1.2 � 1.3). Average post-thaw sperm motility was not different between bulls for either extender, but motility for Bioxcell (Control, 48.1 � 14.6%) and E-1 extenders (43.2 � 13.0%) were significantly greater (P < 0.05) than for E-2 extender (18.7 � 8.8%). There were no differences between bulls for all kinematic semen parameters: curvilinear (VCL), straight line (VSL), average path (VAP) velocities, linearity (LIN) and straightness (STR), evaluated by CASA before and after freezing; however, all were lower (P < 0.05) for the E-2 extender and not different between Control and E-1 extenders. Sperm movements derived from heads (VCL) and linearity of sperm(LIN), both closely related to field fertility, were in the range of 90.9 � 2.1 and 63.0 � 5.5 for E-3 (Control) extender; 99.1 � 3.4 and 49.4 � 3.5 for E-1; and 21.8 � 2.2 and 29.9 � 4.0 for E-2. In summary, zwitteronic soyabean lipid liposomes are an effective egg yolk substitute for the cryopreservation of Asturiana de la Monta�a bull semen; however, the homogenization protocol of the lipids-glycerol mixture must be improved.


2018 ◽  
Vol 30 (1) ◽  
pp. 141
Author(s):  
S. X. Yang ◽  
E. M. Zwiefelhofer ◽  
G. P. Adams ◽  
M. Anzar

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.


Respuestas ◽  
2013 ◽  
Vol 18 (2) ◽  
pp. 16-27
Author(s):  
Leonardo Hernández-Corredor ◽  
Alexander Nivia-Osuna ◽  
Daniel Hernández-Villamizar ◽  
Jorge Alexander Rubio-Parada ◽  
Armando Quintero-Moreno

 El estudio evaluó la motilidad espermática y su efecto postdescongelación en semen caprino, en dos medios comerciales (Andromed® y TwoStep®) y diferentes protocolos de congelación (medio completo, con adicción del 10% de yema de huevo, semen centrifugado y sobrenadante seminal), se utilizaron machos de la raza alpina de la Universidad Francisco de Paula Santander Ocaña, el semen fue colectado con electroeyaculador, una vez los medios terminados y parte de los contenidos seminales enteros o centrifugados mezclados, se estabilizó por 2 horas, se envasó en pajillas de 0,5 cc y se congela en vapores de nitrógeno por 10 minutos, las pajillas se llevaron al laboratorio de Andrología de la Universidad del Zulia y por medio del sistema C.A.S.A.(Computer Assisted Sperm Análisis) se evaluaron los parámetros de motilidad como velocidad curvilínea (VCL), velocidad rectilínea (VSL), velocidad lineal (VAP), índice de linealidad (LIN), índice de rectitud (STR), índice de oscilación (ALH), Amplitud media del desplazamiento lateral de la cabeza del espermatozoide (BCF), los datos fueron analizados por medio del procedimiento GLM de SAS versión 9.0; los mejores índices de motilidad (VCL, ALH, BCF) fueron expresados enel tratamiento de contenido seminal centrifugado en medio Andromed®. (p≤0,001))La mejor progresividad espermática (VSL,LIN,STR)se presentó el tratamiento de Semen completo de caprino, criopreservado en medio comercial TwoStep®. ABSTRACT  The study evaluated the effect sperm motility and sperm post-thawing in goats, two commercial means (Andromed ® and Two Step ®) and different freezing protocols (complete medium with 10% addition of the egg yolk, semen centrifuged supernatant and seminal ), we used males of the Alpine race of the University Francisco de Paula Santander Ocaña, semen was collected with electroejaculator once finished media and part of the whole and centrifuged seminal contents mixed, stabilized by two hours, packed in 0.5 cc straws and frozen in nitrogen vapor for 10 min, the straws were taken to the laboratory of Andrology at the University of Zulia and through CASA system (Computer Assisted Sperm Analysis) were evaluated motility parameters such as curvilinear velocity (VCL), straight line velocity (VSL), linear velocity (VAP), linearity index (LIN), straightness index (STR) Oscillation Index (ALH ) average amplitude of the lateral displacement of the sperm head (BCF), the data were analyzed by the GLM procedure of SAS version 9.0, the highest rates of motility (VCL, ALH, BCF) were expressed in the treatment of seminal content centrifugation Andromed ® medium. (p ≤ 0.001)) The best progressive sperm (VSL, LIN, STR) will present the full Semen treatment goats, cryopreserved at Two Step ® commercial medium.Keywords: semen, buck, Andromed, Two step.


Zygote ◽  
2018 ◽  
Vol 26 (4) ◽  
pp. 301-307 ◽  
Author(s):  
José A. B. Bezerra ◽  
Andréia M. Silva ◽  
Patrícia C Sousa ◽  
Lívia B. Campos ◽  
Érica C. G. Praxedes ◽  
...  

SummaryThe aim of this study was to establish a functional freezing–thawing protocol for epididymal sperm of collared peccaries (Pecari tajacu L., 1758) by comparing different extenders. The epididymal sperm from 12 sexually mature males was recovered by retrograde flushing using Tris-based or coconut water-based (ACP®-116c) extenders. After initial evaluation, samples were diluted and frozen with the same extenders to which 20% egg yolk and 6% glycerol were added. After 2 weeks, thawing was performed at 37°C/60 s and sperm motility, vigour, morphology, functional membrane integrity, sperm viability, sperm plasma membrane integrity, and a computer-assisted semen analysis (CASA) were assessed. In addition, to evaluate the survival of frozen–thawed sperm, a thermal resistance test (TRT) was executed. Samples preserved using Tris were in better condition compared with those preserved using ACP®, showing higher values for most assessments performed, including CASA and the TRT (P<0.05). After determining Tris to be the better of the two extenders, additional samples were thawed using different thawing rates (37°C/60 s, 55°C/7 s, 70°C/8 s). Sperm thawed at 37°C/60 s had the greatest preservation (P<0.05) of viability (54.1 ± 5.9%) and functional membrane integrity (43.2 ± 5.4%), and had higher values for various CASA parameters. In conclusion, we suggest the use of a Tris-based extender added to egg yolk and glycerol for the cryopreservation of epididymal sperm obtained from collared peccaries. In order to achieve better post-thawing sperm quality, we suggest that samples should be thawed at 37°C/60 s.


2010 ◽  
Vol 22 (1) ◽  
pp. 204
Author(s):  
J. Dorado ◽  
M. J. Galvez ◽  
M. R. Murabito ◽  
S. Demyda ◽  
L. J. De Luca ◽  
...  

Tris-egg yolk-based diluents provide adequate cryoprotection for the sperm of most species. This study was conducted to compare the ability of Tris-glucose extender containing 2 different concentrations of egg yolk to maintain sperm motility and acrosome integrity of canine spermatozoa during 72 h of preservation. For this purpose, a total of 20 ejaculates from 4 clinically healthy dogs (2 Spanish Greyhound, 1 German Pointer, and 1 Crossbreed) were collected by digital manipulation. The sperm-rich fraction of each ejaculate was divided into 2 aliquots. Then, they were diluted in Tris-based extender and centrifuged at 700g for 8 min. Sperm pellets were resuspended in either Tris buffer added to 20% (EY20) or 10% centrifuged egg yolk (EY10) and cooled to 5°C over 72 h. The effects of these extenders on motility and acrosome integrity were assessed objectively using a computer-aided semen analyzer (Sperm Class Analyzer, Microptic SL, Spain) and Spermac® staining, respectively. Each cooled-rewarmed semen sample was evaluated after 24, 48, and 72 h of preservation. Sperm motion parameters shown by computer-assisted semen analysis (CASA) are progressively motile (PMS) and motile spermatozoa (MS), curvilinear velocity (CLV), average path velocity (APV), progressive speed (SLV), and lateral head displacement (LHD). Data were statistically analysed by ANOVA. Dependent variables expressed as percentages were arsine-transformed before analysis. Differences between mean values were evaluated by the Duncan method. Data were presented as mean ± SEM. Differences were considered significant when P < 0.05. Analyses were performed using the statistical package SPSS 12.0. A total of 98 172 motile sperm trajectories were analyzed by CASA: 52 259 in EY20 and 45 913 in EY10. After 24, 48, and 72 h of preservation, MS and PMS were statistically higher (P < 0.01) in EY20. No significant differences were found for LHD using either extender over a 72-h period. No significant differences were observed for CLV using either extender during the first 2 days. At Day 3, CLV data were significantly higher (P < 0.01) in EY20. Similarly, from Day 2, APV was significantly higher (P < 0.001) in EY20. After 24 h of preservation, SLV was statistically higher (P < 0.001) in EY10, whereas the opposite tendency was found at Day 3. No significant differences were observed for SLV using either extender after 48 h of preservation. During the first 2 days, acrosome integrity was statistically higher (P < 0.001) in EY20. At hour 72, higher acrosome integrity (P < 0.001) was observed in EY10. In conclusion, we have observed that the EY20 extender provided higher motility after 72 h of chilled preservation; however, the acrosome membrane integrity was better preserved in EY10.


2019 ◽  
Vol 31 (1) ◽  
pp. 194 ◽  
Author(s):  
D. A. Galarza ◽  
M. Ladrón de Guevara ◽  
P. Beltrán-Breña ◽  
M. J. Sánchez-Calabuig ◽  
A. López-Sebastián ◽  
...  

The use of cold-stored ram semen has been applied in sheep AI programs, because it preserves its fertilizing ability similar to fresh. Besides, the heterologous IVF has been successfully employed to assess semen fertilizing ability in several species. Hence, we aimed to evaluate the fertilizing ability of ram semen cold stored up to 48h at 5°C by assessing heterologous IVF using bovine oocytes. Fifteen pools of 3 normospermic Merino ram (2-7 years) ejaculates were collected using artificial vagina, diluted to 200×106 spermatozoa mL−1 with ultra-heat-treatment-based extender (skim milk-6% egg yolk) and cold stored up to 48h. In vitro matured zona-intact bovine oocytes were subjected to heterologous IVF using fresh semen (FS, n=707), semen cold stored to 24h (CS24, n=832) or semen cold stored to 48h (CS48, n=611). In parallel, homologous IVF (control, n=1356) and parthenogenesis (parth control non-fertilized oocytes, n=334) were performed. Ram non-selected and selected (BoviPure, Nidacon International, Mölndal, Sweden) semen parameters were evaluated by computer-assisted semen analysis. Sperm-oocyte interaction was assessed at 2.5h post-insemination (hpi) by evaluating the number of bound spermatozoa, whereas penetration and polyspermy were evaluated after 12 hpi. Presumptive zygotes were fixed and stained with Hoechst 33342 at 18, 20, 22, 24 and 26 hpi to assess pronuclear formation using phase contrast and confocal microscopy. Cleavage rate was evaluated in all groups at 48 hpi. Data obtained from 5 replicates were analysed using one-way ANOVA. Data was expressed as mean±standard error of the mean. In terms of sperm storage time, non-selected semen showed a significant decrease (P&lt;0.05) for CS24 and CS48 compared with FS on progressive motility [SPM (%): 52.30±4.1 and 36.9±5.5v. 71.3±1.6] and straight-line velocity (mm s−1: 132.2±6.1 and 109.7±6.3v. 176.7±4.3), respectively. However, selected semen showed a decrease (P&lt;0.05) only for CS48 when compared with CS24 or FS on SPM (35.6±3.9v. 56.1±6.91 and 59.3±2.6) and straight-line velocity (83.5±4.4v. 105.3±6.5 and 110±2.0), respectively. No differences were observed between heterologous IVF groups in all parameters evaluated. Homologous IVF showed a higher percentage of penetration only when compared with heterologous FS group (44.4±6.8v.12.5±4.5%; P&lt;0.01). The polyspermy was higher in heterologous CS24 group when compared with homologous IVF (11.4±3.4v. 3.8±2.2; P&lt;0.05). The homologous IVF group, as expected, showed the higher percentage of pronuclear formation at 18 hpi compared with heterologous IVF with FS (67.3±5.8v. 35.2±5.6%), CS24 (72.1±4.5 v. 37.2±5.7%) and CS48 (63.0±6.0 v. 27.0±5.6%), respectively (P&lt;0.001). Likewise, cleavage rate was higher in homologous group compared with heterologous IVF and parthenogenetic groups for FS (78.3±2.6.8v. 46.3±3.2 and 7.0±2.3%), CS24 (78.4±2.6 v. 48.3±3.2 and 4.9±2.0%), and CS48 (78.4±3.3 v. 43.3±3.5 and 4.3±1.2%), respectively (P&lt;0.001). In conclusion, Merino ram semen cold stored up to 48h maintains its fertilization ability to the same extend as fresh and can be used for sheep crossbreeding programs.


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