Tris-Lecithin Extender Supplemented With Antioxidant Catalase for Chilling of Canine Semen

Effect of Aqueous Extract of Maca Addition to an Extender for Chilled Canine Semen

Simple Summary

The wide use of artificial insemination in dogs justifies the development of new strategies to prevent the reduction of fertilizing ability of stored semen. In recent years, the use of plant antioxidant supplementation has become increasingly popular. Maca (Lepidium meyenii) is an Andean edible root with antioxidant properties. The effectiveness of the oral supplementation of Maca in improving fresh semen quality and quantity and cooling or freezing ability has already been reported. This is the first in vitro study on the effects of aqueous extract of Maca on canine spermatozoa. The addition of low concentrations of aqueous extract of Maca to the canine chilled extender had positive effects only until 24 h of storage, increasing hyperactivation of sperm cells and preserving DNA integrity of spermatozoa in short-term storage. Meanwhile, a high concentration of Maca had an immediately deleterious effect on semen quality.

Abstract

Antioxidant supplementation has been proposed as a new strategy to improve the long-term preservation of semen. The aim of this study was to evaluate the effect of Maca supplementation of semen extender on quality-related canine semen parameters during cooling. Ejaculates from nine dogs were cooled for 7 days in the absence (control group) or in the presence of 10, 20 and 50 μL/mL of an aqueous extract of Maca. Sperm were evaluated for sperm viability, motility, DNA fragmentation and lipid peroxidation after 3 h, 24 h, 4 days and 7 days of storage. The addition of 10 μL/mL of Maca preserved sperm DNA and plasma membrane integrity at 3 h and increased sperm curvilinear velocity after 24 h. Treatment with 20 and 50 μL/mL of Maca increased the percentage of hyperactivated sperm after 3 h. Moreover, semen treated with 20 μL/mL of Maca decreased lipid peroxidation at 24 h. A significant reduction of sperm DNA and plasma membrane integrity as well as of kinetics parameters between 3 and 24 h of refrigerated storage with the higher concentration tested was observed. Although Maca was not able to protect canine semen with extended refrigeration storage time, it increased hyperactivation and preserved DNA integrity in short-term storage.

Freezability of Dog Semen after Collection in Field Conditions and Cooled Transport

Simple Summary

Dog semen freezing is gaining popularity, but it has to be performed in equipped facilities, which can be far from the place where the stud dog lives. To avoid animal movement, it seemed interesting to investigate whether freezing dog semen after 24 or 48 h of cooled transport to an equipped laboratory was possible when semen collection was performed in the field such as in local breeding kennels. The influence of two pre-freezing holding times (i.e., 24 or 48 h) and two holding diluents (solutions used to dilute semen before freezing) was evaluated. Post-thaw morphofunctional sperm features, such as motility, morphological integrity, and ability to bind female gametes, were assessed. No differences between times or diluents were observed, but motility tended to decrease in the samples frozen at 48 h. Since the insemination dose was based on the number of motile spermatozoa, a shorter pre-freezing time is advisable. Yet, considering that the rest of the morphofunctional parameters remained comparable between samples frozen after collection or after 24/48 h of transport, freezing after cooled transport is a good option for avoiding animal stress and for promoting a greater diffusion of semen cryopreservation.

Abstract

Dog semen freezing is gaining popularity, but it has to be performed in equipped facilities, which can be far from the place where the stud dog lives. The aim of this study was to evaluate whether freezing dog semen after 24 or 48 h of cooled transport to an equipped laboratory was possible when semen collection was performed in the field such as in local breeding kennels. Single ejaculates from different dogs (mixed breeds and ages) were collected. In Experiment I, 10 ejaculates were conventionally frozen using the Uppsala method or frozen after 24 or 48 h of storage in a Styrofoam transport box cooled by icepacks. In Experiment II, 10 ejaculates were used to assess the influence of two extenders (Uppsala chilling extender or freezing extender 1) used for semen dilution during the 24 or 48 h storage. Motility, morphology, membrane, and acrosome integrity were analyzed as well as spermatozoa zona-binding ability. No significant differences were observed among the frozen groups, regardless of freezing time (Experiment I) or extender (Experiment II). Motility at thawing, however, decreased in absolute value at 48 h. Freezing of freshly collected semen is the gold standard, but the results obtained in this study prompt the application of freezing after cooled transport for the long-term preservation of dog semen, especially if the transport can be organized in 24 h.

Effects of Hydroxylated Lecithin on Growth Performance, Serum Enzyme Activity, Hormone Levels Related to Lipid Metabolism and Meat Quality in Jiangnan White Goslings

The objective of the present study was to evaluate the effects of hydroxylated lecithin on growth performance, serum enzyme activity, hormone levels related to lipid metabolism and meat quality in Jiangnan White goslings. Six hundred 1-day-old goslings were randomly divided into five treatments with six replicates and 20 for each replicate. The control group (CG) was fed the basal diet, while the experimental group was fed the basal diet with 50, 100, 200 mg/kg hydroxylated lecithin and 100 mg/kg soy lecithin (HLG50, HLG100, HLG200, and LG100, respectively) in the form of powder. Feed and water were provided ad libitum for 32 days. Compared with the CG, (a) the average daily feed intake was higher (P < 0.05) in HLG100, the final body weight and average daily gain were higher (P < 0.05), and the feed conversion ratio was lower in the HLG200; (b) the alanine aminotransferase, malate dehydrogenase, leptin, glucagon, thyroid hormone, Triiodothyronine contents in the HLG200 were lower (P < 0.05); (c) The breast muscle water holding capacity was higher (P < 0.05) in groups with hydroxylated lecithin, the breast muscle shear force and fiber diameter were lower (P < 0.05) in the HLG100; (d) the inositic acid, intramuscular fat, phospholipid contents were higher (P < 0.05), the triglyceride content was lower (P < 0.05) in HLG100 of the breast muscle; (e) the relative expression of sterol regulatory element-binding protein-1 genes were higher (P < 0.05) in the treated groups of muscles, the phosphorylase kinase gamma subunit 1 gene expression was shown an opposite trend. In comparison with LG100, (a) the feed conversion ratio was lower (P < 0.05) in HLG200; (b) the alanine aminotransferase and adiponectin contents were higher (P < 0.05), the malondialdehyde and free fatty acid contents were lower (P < 0.05) in HLG200; (c) the water holding capacity and intramuscular fat contents in the breast and leg muscles were higher (P < 0.05) in HLG200. The hydroxylated lecithin concentration of 200 mg/kg improved the growth performance, serum enzyme activity, hormone levels related to lipid metabolism, and the meat quality of Jiangnan White goslings.

Effects of egg yolk and soybean lecithin on sperm quality determined by computer-assisted sperm analysis and confocal laser scanning microscope in chilled canine sperm

The reduction of spermatozoa survival time is a major problem of canine chilled sperm for artificial insemination. The aim of the study was to improve the quality of canine chilled sperm during storage time. We therefore, evaluated the effects of eight treatments with different levels of soybean lecithin concentration (1, 3 and 5%) and egg yolk (20%) in Tris-citric-fructose or Tris-citric-fructose-mineral salts extender on chilled canine sperm quality during 10 days of storage. The sperm motility was analysed by computer-assisted sperm analysis (CASA), whereas plasma membrane integrity, acrosome membrane integrity and mitochondrial membrane potential parameters were determined using a fluorescent staining combination of propidium iodide (PI), Hoechst 33342 (H342), fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA) and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide (JC-1) by confocal laser scanning microscope. The results showed that egg yolk was found to be better than soybean lecithin in Tris-citric-fructose or Tris-citric-fructose-mineral salts extender for maintaining the quality of chilled canine sperm within 10 days of storage (P < 0.05). Although egg yolk in Tris-citric-fructose extender could maintain the motility better than other extenders, egg yolk in Tris-citric-fructose-mineral salts extender was the highest in intact plasma membrane, intact acrosome membrane and high mitochondrial membrane potential (P < 0.05). In contrast, the sperm quality of soybean lecithin in Tris-citric-fructose-mineral salts extender was lower than that of soybean lecithin in Tris-citric-fructose extender, and soybean lecithin 1% was greater than soybean lecithin 3% and 5% in plasma membrane integrity, acrosome membrane integrity and mitochondrial membrane potential (P < 0.05). In conclusion, soybean lecithin cannot replace egg yolk in Tris-citric-fructose or Tris-citric-fructose-mineral salts extenders, and egg yolk in Tris-citric-fructose-mineral salts extender is superior to other extenders in chilling canine sperm.

Morphological indices for canine spermatozoa based on the World Health Organization laboratory manual for human semen

Attempting to contribute to the development of a more objective morphological evaluation of dog spermatozoa, in this study the indices of multiple sperm defects (multiple abnormalities index [MAI]; teratozoospermic index [TZI]; sperm deformity index [SDI]) were calculated following the World Health Organization (WHO) guidelines. In Experiment I, the concordance of MAI, TZI and SDI with the proportions of morphologically normal spermatozoa (MNS) was evaluated in fresh ejaculated spermatozoa (dogs = 47). In Experiment II, the potential role of indices as prognostic values was assessed in spermatozoa of different origin and treatment (fresh ejaculated: n = 6; fresh epididymal: n = 6; frozen-thawed ejaculated: n = 6) by their correlation with different semen parameters (motility, membrane integrity and acrosome status) and with an in vitro sperm function test. Samples with different proportions of MNS showed different values of SDI, the index that better represented the decline of sperm morphology in both fresh and frozen-thawed samples (Exp. I and II; p < 0.05). No correlations between indices and semen parameters were observed (Exp. II), but when samples were evaluated collectively, negative correlations (SDI-motility, p = 0.01; SDI-acrosome integrity, p = 0.002) were found. Including all the defects of each spermatozoon, SDI might be a useful index during morphological analysis and better discriminates the increase in multiple defects. A more objective morphological evaluation for dog spermatozoa was achieved by the WHO method, and in vitro tests allowed to elucidate the validity of SDI as prognostic indicator of in vitro fertilizing potential.

Insights into soy lecithin and egg yolk-based extenders for chilling canine spermatozoa

SummaryThe aim of this study was to compare different concentrations of soy lecithin (LEC0.01%, LEC0.05% and LEC0.1%) with egg yolk (Control) in cooling extenders during the storage of semen at 5ºC for 5 days. Twelve dogs (n = 12) were selected, and semen was cooled and assessed after 2, 24, 48, 72, 96 or 120 h. At each time point, sperm were analyzed for kinetic patterns (using computer-assisted sperm analysis), mitochondrial activity (3'3- diaminobenzidine assay), lipid peroxidation (TBARS assay), DNA fragmentation (SCSA®) and plasma and acrosome membrane integrity (eosin/nigrosin and fast green/rose Bengal stains, respectively). The Control group (1814.4 ± 197.2) presented the highest rates of lipid peroxidation at 120 h. Conversely, progressive motility (42.8 ± 4%), linearity (45.4 ± 1%), and VAP (88 ± 3%) were higher in the Control group. In addition, there was lower mitochondrial activity in the Control group at 72 h. Therefore, our data show that lecithin used at these concentrations was not able to maintain sperm viability at as high qualities as would egg yolk. Moreover, the decrease in high mitochondrial activity and the persistence of sperm motility may indicate a compensatory mechanism in canine spermatozoa (i.e., glycolytic pathway). Furthermore, these higher lipid peroxidation indexes could indicate the necessity for future therapy using extenders and antioxidants over a long cooling time for dog sperm.

Effect of ostrich egg lipoproteins and hen egg yolk on the quality of dog sperm during liquid storage at 5°C

The objective of this study was a comparative analysis of the impact of the addition of lipoproteins from ostrich egg yolk (LPFo) and hen egg yolk (HEY) to a Tris-citric acid-fructose (TCF) extender on the quality of dog sperm preserved at 5°C for 7 days. The sperm-rich fraction of the ejaculate was manually collected and extended using the following extenders: control (TCF), TCF+ 5% addition of LPFo (TCF-LPFo) and TCF+ 20% of addition HEY (TCF-HEY). The analysis of quality included: sperm motility parameters (TMOT, PMOT, VAP, VSL, VCL, ALH, BCF, STR, LIN), normal apical ridge acrosome (NAR), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), and ATP content. The addition of LPFo and HEY to the TCF extender had a beneficial effect on all quality parameters of the stored sperm compared with the TCF extender. However, the analysis of sperm motility parameters revealed differences (P≤0.05) between TCF-LPFo and TCF-HEY extenders as affected by storage day. Semen extended in TCF-LPFo was characterized by lower values of TMOT and VAP on Day 5 and by lower values of TMOT and VCL on Day 7, compared to that extended in TCF-HEY. The analysis of PMOT, VSL, ALH, BCF, STR, LIN, PMI, MMP and ATP content showed no differences (P≥0.05) between TCF-LPFo and TCF-HEY extenders. The results suggest that TCF extender supplementation with LPFo or HEY improves the quality of dog sperm stored at 5°C. Both LPFo and HEY protect motility, membrane integrity and can contribute to the improvement of the energy status of stored dog sperm. LPFo can be alternatively used instead of HEY for dog semen preservation in the liquid state.

Cryopreservation of Dog Semen in a Tris Extender with 1% or 2% Soya Bean Lecithin as a Replacement of Egg Yolk

Egg yolk is usually included in extenders used for preservation of dog semen. Lecithin is an interesting animal-protein free alternative to egg yolk for semen preservation. The aim of our study was to evaluate soya bean lecithin for cryopreservation of dog semen. Five ejaculate replicates were divided in three equal parts, centrifuged and each pellet diluted with one of the three Tris-based extenders containing 20% egg yolk, 1% soya bean lecithin or 2% soya bean lecithin. Extended semen was loaded in 0.5-ml straws, cooled and diluted a second time and frozen in liquid nitrogen vapours. Sperm motility parameters (CASA), acrosome integrity (FITC-PNA/PI) and sperm membrane integrity (C-FDA) were evaluated 5 min post-thaw and after 2 and 4 h of incubation. Total motility was significantly better in the egg yolk extender than in any of the lecithin-based extender and was better in the 1% lecithin extender than in the 2% lecithin extender. Sperm membrane integrity was significantly better in the egg yolk extender than in any of the lecithin-based extenders but did not differ significantly between the 1% and 2% lecithin extenders. Acrosome integrity was significantly better in the egg yolk extender than in the 2% lecithin extender but did not differ between the egg yolk extender and the 1% lecithin extender or between the two lecithin extenders. In conclusion, egg yolk was superior to lecithin in our study. The extender with 1% lecithin preserved sperm motility better than the extender with 2% lecithin.

Motility and fertility of rabbit sperm cryopreserved using soybean lecithin as an alternative to egg yolk

This study was conducted to investigate whether soy lecithin can be used as an alternative cryoprotectant to establish a procedure that does not require the use of egg yolk to cryopreserve rabbit strains. Semen from Japanese White rabbits was frozen with HEPES extender containing 20% egg yolk (EYH), 0.5% (Lec-0.5), 1.5% (Lec-1.5), 2.5% (Lec-2.5), or 3.5% (Lec-3.5; wt/vol) lecithin (type IV-S, ≥30%), and the motility of thawed sperm was analyzed. The sperm motility in the Lec-1.5 group was significantly higher than that in the Lec-2.5 and 3.5 groups and equivalent to the EYH group. From 17 rounds of artificial insemination with frozen-thawed sperm in the EYH and Lec-1.5 groups, 12 rabbits in both groups were pregnant (70.6%) and delivered offspring. The litter size was 3.3 in the EYH group and 5.1 in the Lec-1.5 group. These results indicate that soy lecithin can be used as a substitute for egg yolk as a cryoprotectant on the basis of motility and fertility of the frozen-thawed rabbit sperm and that 1.5% lecithin (type IV-S, ≥30%) in the semen extender was the optimum concentration for rabbit sperm cryopreservation.

Soybean lecithin-based extender preserves spermatozoa membrane integrity and fertilizing potential during goat semen cryopreservation

Soybean lecithin may represent a suitable alternative to egg yolk for semen cryopreservation in livestock species. However, additional studies are needed to elucidate its effects on spermatozoa functional properties. Semen collected from five Sarda bucks was cryopreserved in Tris-based extender and glycerol (4% v:v) with different supplementations. In a preliminary experiment, different soybean lecithin concentrations were tested (1%-6% wt/vol) and results in terms of viability, percentages of progressive motile and rapid spermatozoa, and DNA integrity after thawing showed that the most effective concentration was 1%. In the second experiment, semen was frozen in a Tris-based extender with no supplementation (EXT), with 1% lecithin (EXT LC), and 20% egg yolk (EXT EY). The effectiveness of these extenders was also compared with a commercial extender. The EXT EY led to the highest viability and motility parameters after freezing and thawing (P < 0.0001). No significant differences were observed in intracellular ATP concentrations. Additional molecular features revealed that sperm functionality was affected in EXT EY, as demonstrated by lower DNA and acrosome integrity (P < 0.05), and higher lipid peroxidation compared with spermatozoa cryopreserved in EXT LC (P < 0.0001). Results obtained in the heterologous in vitro fertilization test showed that EXT LC better preserved spermatozoa functionality, as demonstrated by the higher fertilization rates compared with the other media (66.2 ± 4.5% for EXT LC vs. 32.7 ± 4.5%, 38.7 ± 4.5%, 39.6 ± 5.2% for EXT, EXT EY, and commercial extender; P < 0.01). The present study demonstrated that lecithin can be considered as a suitable alternative to egg yolk in goat semen cryopreservation, because it ensures higher fertilization rates and a better protection from membrane damage by cold shock.

In vitro assessment of soybean lecithin and egg yolk based diluents for cryopreservation of goat semen

Soybean lecithin is a suitable plant-based cryoprotectant for freezing ruminant sperm. Optimum level of lecithin was not clear for goat semen cryopreservation. The objective of this study was to investigate the effects of different levels of soybean lecithin in semen extender on post-thaw sperm quality including CASA-motion parameters, viability, plasma membrane integrity and lipid peroxidation. Semen samples were collected from 4 Mahabadi bucks using an artificial vagina. Different concentrations of soy lecithin (SL, 0.5%, 1%, 1.5%, 2% and 2.5% w/v) were compared to 15% (v/v) egg yolk-based extender (TR-EY). No significant difference was observed for sperm progressive motility, viability or plasma membrane integrity in 1.5% SL media (33.8%, 66%, and 62.7%, respectively) and TR-EY medium (35.4%, 67.2%, and 64.9%, respectively). Sperm motion characteristics (VAP, VSL, VCL, ALH and LIN) and rapid spermatozoa were improved with extender containing 1% and 1.5% SL, compared to TR-EY extender. Furthermore, egg yolk produced significantly higher malondialdehyde (4.02±0.21) than other groups. Results suggest that the optimal lecithin concentration in the semen extender was 1.5% and also soy lecithin can substitute for egg yolk during cryopreservation for caprine sperm.

Effect of incorporation of additives in tris-based egg yolk extender on buffalo (Bubalus bubalis) sperm tyrosine phosphorylation during cryopreservation

Phosphorylation of tyrosine residues on sperm protein is a known indicator of capacitation and a major intracellular signalling event. There is evidence that sperm cryopreservation promotes tyrosine phosphorylation and is associated with reduced fertility of spermatozoa. Under this study, cryoprotective role of different additives namely taurine, trehalose, catalase and 4-bromophenacyl bromide on buffalo sperm quality was evaluated. Buffalo semen was cryopreserved in tris-based egg yolk extender supplemented with additives like taurine (50 mm) or trehalose (100 mm) or 4-bromophenacyl bromide (200 μm) or catalase (100 U/ml) and used for assessment of levels of tyrosine phosphorylation in frozen-thawed spermatozoa. The results obtained were compared with the level of protein tyrosine phosphorylation of semen cryopreserved in tris-based egg yolk extender without additives. Proteins were extracted from a total number of nine ejaculates from three individual buffalo bulls chosen at random and analysed for tyrosine phospho-proteins using SDS-PAGE followed by immunoblotting. Monoclonal anti-phosphotyrosine antibody (Clone pT-154) was used as primary antibody followed by treatment with HRP-conjugated secondary antibody. Signals were detected on X-ray film using chemiluminescence. Nine proteins (p20, p30, p32, p38, p49, p56, p59, p72 and p86) were found to be tyrosine phosphorylated in cryopreserved spermatozoa. Supplementation of additives significantly (p<0.05) reduced the level of protein tyrosine phosphorylation in spermatozoa. Moreover, this study showed improved (p<0.05) post-thaw motility, viability and membrane integrity of spermatozoa on addition of these additives. The results obtained clearly indicate reduced level of capacitation like changes on supplementation of additives in terms of protein tyrosine phosphorylation.