INDIVIDUAL CRYOPRESERVATION WITH DIMETHYL SULFOXIDE AND POLYVINYLPYRROLIDONE OF EJACULATES AND POOLED SEMEN OF THREE AVIAN SPECIES

Collection, Handling, and Preservation of Wild Bird Semen: Current Status, Challenges, and Perspectives

Semen preservation is a significant biotechnology used to safeguard the genetic material of birds, especially those with declining populations, through biobanking. However, there are limited reports on the successful chilling or cryopreservation of wild bird semen. In general, these techniques are not yet well-established for several species of wild birds and pose several challenges such as the need for bird handling and training, contamination of semen samples, low volume of semen collected, and inefficient preservation protocols. To address these challenges and improve post-thawing outcomes, new possibilities are being investigated, including alternative collection methods to traditional digital massage, the use of antioxidants and enzymes in the medium for chilling or freezing, storage methods using different straws from the usual pellet, and slower freezing rates. This review aims to discuss the various aspects of applying semen preservation in wild birds to create germplasm banks, highlighting the primary results obtained and the challenges that need to be addressed.

Viability of in vitro preserved sperm of Harris's hawk (Parabuteo unicinctus)

Harris hawks (Parabuteo unicinctus) are the raptors with more anthropogenic use, which makes it necessary to improve their reproduction either natural or assisted for sustainable use even though they are not endangered. The aim of this study was to determine fresh and thawed P. unicinctus sperm capacitation and acrosome reaction parameters as indicators of sperm viability in ejaculates of birds with injuries. A total of 30 ejaculates were analyzed as fresh and thawed samples. Basic sperm evaluations as well as in vitro acrosomal reaction capability through the presence and distribution of Ca²⁺ and N-acetylglucosamine and sialic acid using chlortetracycline and agglutinin-fluorescein isothiocyanate Triticum vulgaris were performed, respectively. Tagged samples were observed using epifluorescence microscopy. The results indicated 30.00% decrease in sperm viability following freeze-thaw, while rate of capacitated sperms (10.00%) and the percentage of sperm with acrosomal reaction (40.00%) were increased. The results of the experiment demonstrated that the post-thaw viability of the obtained sperm may be an alternative for use in artificial insemination.

Poloxamer 188 and hydroxyethyl starch have a cryoprotective synergic effect improving post-thawing quality and fertility of rooster spermatozoa

Poloxamer and hydroxyethyl starch have cytoprotective effects. In the present study, effectiveness was evaluated of these compounds as a cryoprotectant for rooster semen. In Experiment 1 (E1), poloxamer 188 (1%, P188), poloxamer 407 (1%, P407), and control groups were compared after sperm cryopreservation. Experiment 2 (E2) was conducted with 3%, 5%, and 7% of hydroxyethyl starch (H3, H5, H7), also combined with P188 (H3P188, H5P188, H7P188), based on results from E1. Sperm motility was assessed using CASA, abnormal forms and hypo-osmotic swelling (HOS) were evaluated using microscopy, and viability, apoptotic-like changes, and mitochondrial activity were determined using flow cytometry. In E2, there were assessments of fertility and hatching capacity. Results from E1 indicated total and progressive motility, velocity, membrane functionality, viability, and mitochondrial activity were greater with inclusion of P188 in semen extender, with less apoptotic-like changes (P < 0.05). In E2, HES inclusion in semen extender improved total motility, membrane functionality, and mitochondrial activity (P < 0.05), especially H5, which also markedly increased sperm viability and decreased apoptotic-like changes. The combination of P188 with HES increased sperm quality overall, with inclusion of H5P188 resulting in increases of progressive motility and VSL (P < 0.05). The H5 inclusion also increased proportion of fertilized eggs (P < 0.05). Furthermore, the combination of HES and P188 increased proportions of fertilized and hatched eggs compared with the control, with inclusion of H5P188 having the greatest effects. In conclusion, supplementation of semen extender with H5P188 increases post-thawing quality and fertility of rooster sperm, being a safe and effective method for the poultry industry.

In vitro sperm storage with poultry oviductal secretions

In the hen oviduct, tubules have been identified that preserve the sperm, maintaining viability for up to 15 weeks. This study aimed to evaluate the physiological status of rooster sperm when preserved in vitro with uterus vaginal junction secretions (UVJS). Males and females of the Rhode Island breed were used. Sperm aliquots were prepared using Lake extender and Lake extender with UVJS (10.00%, 30.00%, 60.00%, and 90.00%). Subsequently, a basic sperm evaluation was performed and sperm physiological status was determined through the presence and distribution of Ca²⁺ and its acrosomal reaction capability via perivitelline layer (PVL) co-incubation. It was observed that motility was decreased in sperm preserved with UVJS at 6 and 24 hr) compared to 40 min and fresh semen. The sperm decapacitation percentage was increased when preserved with UVJS at 40 min, 6 and 24 hr compared to fresh semen. The acrosomal reaction was increased in sperm co-incubated with PVL, even when preserved with UVJS. It was concluded that UVJS induced physiological changes in sperm by inducing a decapacitation process, which increased sperm viability when preserved in vitro.

Cryopreservation of Ghagus chicken semen: Effect of cryoprotectants, diluents and thawing temperature

The present study evaluated the effects of cryoprotectants, semen diluents and thawing temperature during Ghagus chicken semen cryopreservation. Four different experiments were conducted; Experiment 1-semen was cryopreserved using 6% dimethylacetamide (DMA) and 2% dimethylsulphoxide (DMSO) in Sasaki diluent (SD) and Lake and Ravie diluent (LR), Experiment 2 and 3-semen was cryopreserved using 8% ethylene glycol (EG) in SD, LRD and Red Fowl Extender (RFE), Experiment 4-semen was cryopreserved using 6% dimethylformamide (DMF) in SD, LR and Beltsville poultry semen extender (BPSE). Semen was cryopreserved in 0.5 ml French straws. Thawing was done at 5°C for 100 s in ice water in Experiments 1, 2 and 4, whereas in Experiment 3 thawing was done at 37°C for 30 s. The post-thaw sperm motility, viable sperm and acrosome-intact sperm were significantly (p < .05) lower in cryopreserved samples in all the experiments. No fertile eggs were obtained from cryopreserved samples in Experiments 1 and 2, except for 8% EG RFE treatment where the fertility was 0.83%. In Experiments 3 and 4, highest fertility was obtained in LR treatment 48.12 and 30.89%, respectively. In conclusion, using cryoprotectant EG (8%) and thawing at 37°C for 30 s, and DMF(6%) resulted in acceptable level of fertility in Ghagus chicken. Though the diluents influenced post-thaw in vitro semen parameters, the fertility was not affected. In addition, results indicated that thawing temperature may be a critical stage in the cryopreservation protocol.

Optimization of Sperm Cryopreservation Protocol for Peregrine Falcon (Falco peregrinus)

Sperm cryopreservation is a complex process that needs to be adapted to wild and domestic avian species to ensure proper efficiency. Because of its accessibility, the peregrine falcon may be used as a good model for studying other raptor species. To find the most optimal cryopreservation protocol for peregrine falcon ejaculates, sperm parameters such as motility, viability, DNA fragmentation, acrosome integrity, and mitochondrial activity were analyzed under different conditions by varying the freezing method (slow freezing in straws vs. ultrarapid freezing in pellets), thawing conditions (37 °C for 30 s vs. 5 °C for 1 min), type of cryoprotectant (DMA vs. DMSO), and concentration of DMSO (4% vs. 8%). Results show that slow cryopreservation in straws yielded greater percentages (p < 0.05) of motile spermatozoa (22.5% ± 4.4% vs. 0.0% ± 4.1%), viable spermatozoa with intact acrosomes (84.6% ± 4.3% vs. 77.4% ± 4.3%), and spermatozoa with active mitochondria (41.0% ± 6.7% vs.12.8% ± 6.7%), compared with those obtained by the ultrarapid freezing in pellets. However, no differences were found between different thawing conditions. Moreover, all sperm motility parameters were greater (p < 0.05) when DMSO was used during freezing compared with DMA, although the use of 3% and 8% DMSO produced similar results. In conclusion, these results represent important progress in the study of falcon semen cryopreservation protocol, highlighting the crucial steps of the process and the most suitable conditions.

Fertility after insemination with frozen-thawed sperm using N-methylacetamide extender on the Combatiente Español avian breed

The aim of this study was to evaluate the in vitro and in vivo quality of frozen-thawed sperm obtained from the Combatiente Español avian breed, with sperm having previously been diluted in N-methylacetamide (NMA). Experimental groups were established: fresh control semen (C); semen diluted without cryoprotectant (T1); semen diluted with extender containing NMA (T2); frozen-thawed sperm (with NMA) containing 500 × 10⁶ spermatozoa (T3); frozen-thawed sperm (with NMA) containing 250 × 10⁶ spermatozoa (T4). In the different groups, sperm motility and viability were assessed using a computer-assisted semen analyzer and flow cytometer, respectively. To evaluate the fertilizing capacity of the sperm, the percentage of fertile eggs was determined. The fertility rate after insemination with frozen-thawed semen was poor, and the concentration of the inseminating dose did not affect fertility rate (9.4 ± 2.7% and 7.0 ± 2.3%, respectively). The results indicate insemination using diluted semen without CPA leads to a reduced fertility, and the addition of 9% NMA to the extender has a greater negative effect on this in vivo variable. Furthermore, inclusion of NMA in the freezing-thawing processes reduced capacity of sperm for fertilization. Sperm viability was reduced during the freezing process, and the dilution in NMA extender affected both sperm viability and motility. The results indicate rooster fertility is negatively affected by sperm dilution, NMA addition and the frozen-thawed effects. Frozen-thawed sperm from Combatiente Español roosters maintained fertilizing capacity for no more than 6 days after insemination, whereas for fresh sperm this capacity was maintained for 14 days.

Semen collection by electro-stimulation in a variety of bird orders

It is unquestinable that artificial insemination (AI) offers many benefits to avian conservation programs, but a serious impediment towards implementing AI for wild species is the development of effective techniques to consistently collect good quality ejaculates. Thus, we aimed to examine the success rate of electro-stimulation (ES) in collecting semen from 49 unconditioned males from orders Piciformes, Strigiformes, Accipitriformes, Cathartiformes, Galiformes, Anseriformes and Psittaciformes at different times of the year. Sixty out of 299 ES attempts provided ejaculates with sperm, but collection success rates varied widely (0-50%) depending on the species. Except for swans whose greater results were registered during spring-summer, males from most orders responded better to ES during winter-spring, suggesting seasonal variations on semen collection success rates. Overall, ES enabled successful semen collection from males of unproven and proven fertility under mixed pairing conditions. However, the highest success rate occurred in paired males with fertile clutches (40.6%) followed by unpaired males (22.1%), paired males without clutches (13.9%), and paired males with infertile clutches (6.8%). Behavioral responses of male birds to electrical impulses were also recorded to assess any discomfort during semen collection. Furthermore, macroscopic and microscopic analysis provided ejaculate parameters from several species, even from orders that hitherto have never been assessed for semen collection, which may serve as a starting point in the future. Altogether, these findings demonstrate the feasibility of ES in collecting semen from unpaired, unconditioned and non-imprinted males from a variety of bird orders. In the medium to long term, the use of this technique in both captive and free-ranging populations offers new perspectives to ensure genetic diversity in avian conservation programs.

Cryoprotectant effects of egg yolk on Indian red jungle fowl (Gallus gallus murghi) sperm

Egg yolk is a good external cryoprotectant of mammalian sperm and some wild bird's sperm, but, at least in domestic breeds of chicken (Gallus gallus domesticus), it may inhibit eventual fertilization of ova when high concentrations are used. We hypothesized that egg yolk can protect the sperm from cryo-induced damages providing adequate fertilization in one phylogenetic wild ancestor of current chicken breeds: the Indian red jungle fowl (Gallus gallus murghi). To test the hypothesis, the present study was designed to evaluate different concentrations of egg yolk in extender in comparison with glycerol. Semen collected from Indian red jungle fowl cocks (n = 8) was cryopreserved using different egg yolk concentrations (10%, 15%, 20% and 25%) or 20% glycerol (control group) following routine protocol of cryopreservation. During cryopreservation, sperm motility (67.5 ± 2.5%), plasma membrane integrity (66.3 ± 2.4%), viability (58.8 ± 1.3%) and acrosomal integrity (60.0.8 ± 2.0%) were recorded highest in an extender with 15% egg yolk compared to other experimental extenders and control at post-dilution, cooling, equilibration and thawing. The no. of fertilized eggs (26.6 ± 0.7, 21.6 ± 1.2), percent fertility (55.9 ± 4.4, 46.5 ± 2.2), no. of hatched chicks (23.6 ± 1.0, 17.2 ± 1.0), percent hatch (49.5 ± 3.2, 37.1 ± 2.5%) and hatchability of the fertile eggs (89.4 ± 2.2, 79.7 ± 3.7) were recorded higher (P < 0.05) with semen cryopreserved with 15% egg yolk compared to control (20% glycerol). It is concluded that 15% egg yolk can be used in cryopreservation protocol of Indian red jungle fowl sperm.

Cryopreservation of rat, dog and human hepatocytes: influence of preculture and cryoprotectants on recovery, cytochrome P450 activities and induction upon thawing

Several cryopreservation protocols for hepatocytes have been proposed over the past few years, but their effectiveness varies greatly as a function of the characteristics of the method used. One factor in the success of cryopreservation is the quality of cells before freezing. The results suggest that the cryopreservation of hepatocytes in a medium containing polyvinylpyrrolidone (PVP), in addition to DMSO, constitutes a convenient means of long-term storage of hepatocytes for preparing primary cultures to be used in drug metabolism studies. The combined use of the two cryoprotectants is particularly critical for low-viability cell suspensions. An interesting alternative to increase cell viability is the preculture of hepatocytes before cryopreservation. By the use of this procedure, high-quality cells, estimated in terms of post-thaw recovery, viability, adaptation of hepatocytes to culture, drug-metabolizing capability and cytochrome P450 induction, are obtained. Therefore, cryopreserved hepatocytes can provide a regular source of metabolically competent cells for in vitro investigations of the metabolic profile of new drugs and drug-drug interactions in pharmaco-toxicological research.