M M Buhr

University of Guelph, Guelph, Ontario, Canada

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Publications (52)103.58 Total impact

  • Katie D Hickey, Mary M Buhr
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    ABSTRACT: Existing as a ubiquitous transmembrane protein, Na(+)K(+)-ATPase affects sperm fertility and capacitation through ion transport and a recently identified signaling function. Functional Na(+)K(+)-ATPase is a dimer of α and β subunits, each with isoforms (four and three, respectively). Since specific isoform pairings and locations may influence or indicate function, the objective of this study was to identify and localize subunits of Na(+)K(+)-ATPase in fresh bull sperm by immunoblotting and immunocytochemistry using antibodies against α1 and 3, and all β isoforms. Relative quantity of Na(+)K(+)-ATPase in head plasma membranes (HPM's) from sperm of different bulls was determined by densitometry of immunoblot bands, and compared to bovine kidney. Sperm and kidney specifically bound all antibodies at kDa equivalent to commercial controls, and to additional lower kDa bands in HPM. Immunofluorescence of intact sperm confirmed that all isoforms were present in the head region of sperm and that α3 was also uniformly distributed post-equatorially. Permeabilization exposing internal membranes typically resulted in an increase in fluorescence, indicating that some antibody binding sites were present on the inner surface of the HPM or the acrosomal membrane. Deglycosylation of β1 reduced the kDa of bands in sperm, rat brain and kidney, with the kDa of the deglycosylated bands differing among tissues. Two-dimensional blots of β1 revealed three distinct spots. Based on the unique quantity, location and structure Na(+)K(+)-ATPase subunits in sperm, we inferred that this protein has unique functions in sperm.
    Theriogenology 01/2012; 77(7):1369-80. · 2.08 Impact Factor
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    ABSTRACT: This paper reviews stresses boar sperm undergo during processing and presents preliminary results of dietary modification that minimize this damage. Processing for artificial insemination (AI) stresses boar sperm by osmotic effects; altering cell size, shape and membranes; intracellular ice formation; and production of reactive oxygen species (ROS). Sperm response to ROS is concentration-dependent, with low levels activating the ERK pathway to stimulate tyrosine phosphorylation (Tyr-P) and capacitation, but high concentrations or inappropriately timed onset of ROS pathways can harm sperm. Fresh boar sperm exposed to ROS increased intracellular hydrogen peroxide (H(2) O(2) ) phospholipase and lipid peroxidation, maintained viability but lost motility and underwent acrosome reactions (AR). Direct incorporation of lipids ± the antioxidant Vitamin E improves the survival of liquid- and frozen-stored semen. Boars fed dietary flaxseed for 8 weeks to increase n-3 fatty acids displayed improved sperm morphology (p < 0.05), increased membrane fluidity (p < 0.05) and better retention of motility and viability during 5-7 day storage (p < 0.05). Processes reducing oxidative damage to stored sperm should be evaluated.
    Reproduction in Domestic Animals 09/2011; 46 Suppl 2:39-44. · 1.39 Impact Factor
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    Katie D Hickey, Mary M Buhr
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    ABSTRACT: Sperm membranes change in structure and composition upon ejaculation to undergo capacitation, a molecular transformation which enables spermatozoa to undergo the acrosome reaction and be capable of fertilization. Changes to the membrane environment including lipid composition, specifically lipid microdomains, may be responsible for enabling capacitation. To study the effect of lipid environment on proteins, liposomes were created using lipids extracted from bull sperm membranes, with or without a protein (Na(+) K(+)-ATPase or α-amylase). Protein incorporation, function, and orientation were determined. Fluorescence resonance energy transfer (FRET) confirmed protein inclusion in the lipid bilayer, and protein function was confirmed using a colourometric assay of phosphate production from ATP cleavage. In the native lipid liposomes, ATPase was oriented with the β subunit facing the outer leaflet, while changing the lipid composition to 50% native lipids and 50% exogenous lipids significantly altered this orientation of Na(+) K(+)-ATPase within the membranes.
    Journal of lipids. 01/2011; 2011:208457.
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    ABSTRACT: The objective of this study was to determine the effect of in utero and lactational exposure to nicotine on the male reproductive tract. Dams were randomly assigned to receive saline or nicotine bitartrate (1mg/kg-d s.c.) daily for two weeks prior to mating until weaning (postnatal day 21). Male offspring were sacrificed at 7 (peri-pubertal) and 26 (adult) weeks of age. Nicotine-exposure resulted in retention of spermatids after stage VIII, tubular vacuolation, degeneration of pachytene and round spermatids at stage VII in the testes; and lymphocyte infiltration, germ cell exfoliation, and hypospermia in epididymides, at 7 weeks of age. Nicotine-exposure had no effect on testis or epididymal morphology, daily sperm production, epididymal sperm reserve, sperm viability at 26 weeks of age, and circulating testosterone levels at either age examined. We conclude that maternal nicotine-exposure during pregnancy and lactation can induce transient structural changes in the testis and epididymis of male offspring.
    Reproductive Toxicology 12/2010; 31(4):418-23. · 3.14 Impact Factor
  • Basim J Awda, Mary M Buhr
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    ABSTRACT: The extracellular signal-regulated kinase (ERK) family of the mitogen-activated protein kinase (MAPK) pathway is identified for the first time in boar sperm and is associated with capacitation and tyrosine phosphorylation (tyr-P). Reactive oxygen species (ROS) modulate this signal transduction. Western immunoblotting detected the ERK pathway components RAF1, MEK1/2, and ERK1/2 in extracts from fresh boar spermatozoa and determined that their phosphoprotein profiles differed in a capacitation-dependent fashion. Capacitation was accompanied by appearance of two new ERKs (158 and 161 kDa) and disappearance of others. Capacitation was verified with increased tyr-P, which was inhibited by a 30-min pre-exposure of fresh boar sperm to a xanthine/xanthine oxidase ROS-generating system prior to the capacitating incubation; ROS pre-exposure also affected the phosphorylation of RAF1, MEK1/2, and ERK1/2. Preincubating sperm with inhibitors of the ERK components with or without the ROS generator affected subsequent capacitation. Inhibiting ERK1/2 inhibited tyr-P of capacitated boar spermatozoa proteins of 172, 97, and 66 kDa (P ≤ 0.04); with ROS, this inhibition increased (P < 0.002) and tyr-P of 111 kDa declined (P < 0.028). Pre-exposure to ROS plus MEK1/2 inhibitor prevented capacitation-induced tyr-P of proteins of 187 (P < 0.01) and 112 kDa (P < 0.04) versus capacitation with or without ROS. Therefore, ERK1/2 components of the MAPK pathway significantly regulate boar sperm capacitation, and RAF1 and MEK1/2 may have some lesser influence through crosstalk with different pathways. ROS affect RAF1, MEK1/2, and ERK1/2 and could influence the sequential events of boar sperm capacitation.
    Biology of Reproduction 11/2010; 83(5):750-8. · 4.03 Impact Factor
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    ABSTRACT: The present work aimed to compare the effect of dietary flax with other oil sources on rooster sperm membranes and on semen characteristics. White Leghorn roosters (16 per diet) were fed 1 of 4 treatments: control diet (CON), or a diet containing corn oil (CORN), fish oil (FISH), or flax seed (FLAX) as the lipid source. Semen from 4 birds (30 wk old) of each treatment was pooled, the sperm head (HM) and body membranes (BM) were isolated, and lipids were extracted and analyzed. Aspects of lipid composition tested were as follows: percentage of individual fatty acids (C14:0 to C24:1) in total fatty acids, percentage of fatty acid categories [saturated, monounsaturated, polyunsaturated (PUFA), n-3 and n-6 PUFA, and n-6:n-3 ratio] within total fatty acids, and percentage of phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol, phosphatidylserine, and sphingomyelin] in total phospholipids. Sperm characteristics evaluated were as follows: volume, concentration, viability, percentage of motile cells, average path velocity, track speed, progressive velocity, lateral head displacement, straightness, and linearity. Diet did not affect membrane phospholipid ratios in either membrane but modified major fatty acids within certain phospholipids. Birds fed FISH and CORN showed, respectively, the highest and the lowest n-3 in sperm, causing reciprocal significant changes in n-6:n-3 ratio. Feeding FLAX caused intermediate effects in n-3, with values significantly lower than FISH but higher than CORN in HM (PC, PE, and phosphatidylinositol) and PC in BM (P < 0.05). In the PE phospholipids, FISH, followed by FLAX, increased n-3 in BM and decreased n-6 PUFA in HM. Sperm concentration was specifically correlated with the amount of 20:4n-6 in FLAX and 22:4n-6 in CON. In FLAX diets, straightness correlated with C18:0, n-3, and n-6:n-3 ratio. Diets containing distinct lipid sources differentially modify the lipid contents of HM and BM, with minor effects on sperm characteristics. Flax seed produced changes similar to fish oil and could be used as a substitute.
    Poultry Science 06/2009; 88(5):1060-9. · 1.52 Impact Factor
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    ABSTRACT: Boar spermatozoa are very susceptible to reactive oxygen species (ROS), but ROS involvement in damage and/or capacitation is unclear. The impact of exposing fresh boar spermatozoa to an ROS-generating system (xanthine/xanthine oxidase; XA/XO) on sperm ROS content, membrane lipid peroxidation, phospholipase (PL) A activity, and motility, viability, and capacitation was contrasted to ROS content and sperm function after cryopreservation. Exposing boar sperm (n = 4-5 ejaculates) to the ROS-generating system for 30 min rapidly increased hydrogen peroxide (H2O2) and lipid peroxidation in all sperm, increased PLA in dead sperm, and did not affect intracellular O2- (flow cytometry of sperm labeled with 2',7'-dichlorodihydrofluorscein diacetate, BODIPY 581/591 C11, bis-BODIPY-FL C11, hydroethidine, respectively; counterstained for viability). Sperm viability remained high, but sperm became immotile. Cryopreservation decreased sperm motility, viability, and intracellular O2- significantly, but did not affect H2O2. As expected, more sperm incubated in capacitating media than Beltsville thawing solution buffer underwent acrosome reactions and protein tyrosine phosphorylation (four proteins, 58-174 kDa); which proteins were tyrosine phosphorylated was pH dependent. Pre-exposing sperm to the ROS-generating system increased the percentage of sperm that underwent acrosome reactions after incubation in capacitating conditions (P < 0.025), and decreased capacitation-dependent increases in two tyrosine-phosphorylated proteins (P < or = 0.035). In summary, H2O2 is the major free radical mediating direct ROS effects, but not cryopreservation changes, on boar sperm. Boar sperm motility, acrosome integrity, and lipid peroxidation are more sensitive indicators of oxidative stress than viability and PLA activity. ROS may stimulate the acrosome reaction in boar sperm through membrane lipid peroxidation and PLA activation.
    Biology of Reproduction 05/2009; 81(3):553-61. · 4.03 Impact Factor
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    ABSTRACT: Assessing semen quality is crucially important for the exploitation of genetically superior sires in an artificial insemination (AI) program. In this study, we compare modern and conventional techniques to estimate bovine sperm concentration and membrane integrity. First, the NucleoCounter SP-100 was validated for sperm concentration and provided statistically reliable and repeatable estimates among aliquots and replicates of 25 fresh ejaculates. Sperm concentrations in 78 ejaculates were then determined with hemacytometer, flow cytometer, and NucleoCounter SP-100 and were significantly correlated (P < .001), with regression coefficients among these 3 techniques close to 1 (P < .01). However, the sperm concentration determined by hemacytometer was lower (P < .01) than by flow cytometer and NucleoCounter SP-100. Forty frozen-thawed semen samples were then assessed for sperm concentration and membrane integrity with hemacytometer, flow cytometer and NucleoCounter SP-100. Significant relationships were found for sperm concentration determined by hemacytometer and NucleoCounter SP-100 and for sperm membrane integrity determined by flow cytometer and NucleoCounter SP-100 (P < .01). Finally, the standard curves of sperm concentrations in 6 spectrophotometers, comparing optical density against counts drawn by hemacytometer and NucleoCounter SP-100 (n = 94 fresh ejaculates) showed different (P < .01) intercepts and regression coefficients (linear, quadratic, cubic). It was calculated that a breeding station can improve its production potential by 13% with the use of NucleoCounter SP-100 instead of hemacytometer for calibration of spectrophotometers. Flow cytometer and NucleoCounter SP-100 can be used with equal confidence to estimate sperm concentration and membrane integrity in domestic animals and human semen.
    Journal of Andrology 05/2009; 30(6):661-8. · 3.37 Impact Factor
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    ABSTRACT: Sperm-mediated gene transfer (SMGT) might become the most efficient and cost effective technique to generate transgenic animals, which will significantly increase their application in biomedical research and in commercial production. Despite some successes, the technique has remained controversial for almost 20 years and despite number of studies the reasons for poor reproducibility of this promising technology has not been understood. We suggest that the reason for poor reproducibility is the presence of natural defences against exogenous DNA invasion acting in spermatozoa or in embryo. Based on previous reports we have investigated the effect of foreign DNA binding on spermatozoa by monitoring motility, viability and genomic DNA damage. Evaluation of DNA binding in sperm collected from 16 boars demonstrated that 28-45% of the added pEGFP plasmid was bound to spermatozoa with 9-32% being internalized in sperm nucleus. In agreement with previous reports, our results demonstrated that the pEGFP-treated sperm show an average a 2-fold decrease in motility (p<0.05), 5-fold decrease in progressive motility (p<0.05), and 1.4-fold increase in number of sperm with highly damaged DNA (p<0.05) as detected by Comet assay. In contrast with previous reports, we demonstrate that all such changes were associated with the removal of seminal plasma during the washing step and not with foreign DNA binding per se. We suggest that poor reproducibility of SMGT most likely result from selection against DNA-loaded sperm at later stages of fertilization.
    Theriogenology 11/2008; 70(8):1288-96. · 2.08 Impact Factor
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    ABSTRACT: Sex-sorted bovine semen has become a valuable tool in animal production for sex preselection. Development of novel sperm sexing technologies, or evaluation of the quality of existing methods, often requires a single-sperm, sex-typing method that is reliable and easy to perform. In the present study, we report the development, validation, and application of a simple, reliable, and cost-effective method for single-sperm sex typing using nested polymerase chain reaction (PCR), based on the amelogenin gene. Several hundred single sperm were isolated using a simple manual technique, or a high-speed flow-sorter, and were successfully sex-typed using the amelogenin nested PCR. Based on the pooled results of individual sperm, there was no significant difference in the semen sex ratio of unsorted (44.6% X-sperm and 55.4% Y-sperm) or X/Y-sorted semen (91.4% X-sperm and 94.0% Y-sperm), as compared to the expected ratio in unsorted semen or the post-sorting reanalysis data, respectively. The amelogenin single-sperm sexing method was an adaptable, accurate, and reliable tool for single-sperm sex typing.
    Theriogenology 10/2008; 70(6):978-83. · 2.08 Impact Factor
  • Mary M Buhr
    Theriogenology 09/2008; · 2.08 Impact Factor
  • Basim J. Awda, Mary M. Buhr
    Theriogenology 01/2008; 70(8):1388-1388. · 2.08 Impact Factor
  • Theriogenology 01/2008; 70(8):1384-1384. · 2.08 Impact Factor
  • M.M. Buhr, M.J. Pettitt
    Reproduction in Domestic Animals 10/2007; 31(1):147 - 152. · 1.39 Impact Factor
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    ABSTRACT: A heteromeric integral membrane protein, Na+/K+ATPase is composed of two polypeptides, alpha and beta, and is active in many cell types, including testis and spermatozoa. It is a well-known ion transporter, but binding of ouabain, a specific inhibitor of Na+/K+ATPase, to Na+/K+ATPase in somatic cells initiates responses that are similar to signaling events associated with bovine sperm capacitation. The objectives of the present study were to demonstrate the presence of Na+/K+ATPase in bovine sperm and to investigate its role in the regulation of bovine sperm capacitation. The presence of Na+/K+ATPase in sperm from mature Holstein bulls was demonstrated by immunoblotting and immunocytochemistry using a monoclonal antibody developed in mouse against the beta 1 polypeptide of Na+/K+ATPase. Binding of ouabain to Na+/K+ATPase inhibited motility (decreased progressive motility, average path velocity, and curvilinear velocity) and induced tyrosine phosphorylation and capacitation but did not increase intracellular calcium levels in spermatozoa. Furthermore, binding of ouabain to Na+/K+ATPase induced depolarization of sperm plasma membrane. Therefore, binding of ouabain to Na+/K+ATPase induced sperm capacitation through depolarization of sperm plasma membrane and signaling via the tyrosine phosphorylation pathway without an appreciable increase in intracellular calcium. To our knowledge, this is the first report concerning the signaling role of Na+/K+ATPase in mammalian sperm capacitation.
    Biology of Reproduction 10/2006; 75(3):308-17. · 4.03 Impact Factor
  • M Anzar, M M Buhr
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    ABSTRACT: Sperm-mediated DNA transfer can be used to transfer exogenous DNA into the oocyte for the production of transgenic animals. In spite of controversy in the literature, sperm-mediated DNA transfer is a simple and quick technique that can be used in routine breeding programs (AI, embryo transfer and IVF). The main objective of this study was to determine the factors affecting the spontaneous uptake of exogenous DNA by bull spermatozoa. For this purpose, fresh and frozen spermatozoa (0.25 x 10(6)), from the same ejaculate from each of four bulls were co-incubated with fluorescent-labeled green fluorescent protein (GFP) and chloremphenicol acetyltransferase (CAT) plasmids at 37 degrees C for 30 min. Neither bull nor plasmid significantly affected the uptake of exogenous DNA. However, transfection efficiency was higher in frozen-thawed versus fresh spermatozoa (P<0.001). Regardless of whether transfected spermatozoa were alive or dead, all transfected spermatozoa were immotile. It can be concluded that a population of spermatozoa is present in bull semen which has the ability to uptake exogenous DNA spontaneously. There is tremendous scope to improve transfection efficiency of spermatozoa while maintaining motility; this needs to be achieved in order to more easily use this technique in transgenesis. However, live-transfected bull spermatozoa clearly can incorporate exogenous DNA and should be usable in intracytoplasmic sperm injection protocols.
    Theriogenology 04/2006; 65(4):683-90. · 2.08 Impact Factor
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    ABSTRACT: Sperm gain full ability to bind to the zona(e) pellucida(e) (ZP) during capacitation. Since lipid rafts are implicated in cell adhesion, we determined whether capacitated sperm lipid rafts had affinity for the ZP. We demonstrated that lipid rafts, isolated as low-density detergent resistant membranes (DRMs), from capacitated pig sperm had ability to bind to homologous ZP. This binding was dependent on pig ZPB glycoprotein, a major participant in sperm binding. Capacitated sperm DRMs were also enriched in the male germ cell specific sulfogalactosylglycerolipid (SGG), which contributed to DRMs-ZP binding. Furthermore, SGG may participate in the formation of sperm DRMs due to its interaction with cholesterol, an integral component of lipid rafts, as shown by infrared spectroscopic studies. Since sperm capacitation is associated with cholesterol efflux from the sperm membrane, we questioned whether the formation of DRMs was compromised in capacitated sperm. Our studies indeed revealed that capacitation induced increased levels of sperm DRMs, with an enhanced ZP affinity. These results corroborated the implication of lipid rafts and SGG in cell adhesion and strongly suggested that the enhanced ZP binding ability of capacitated sperm may be attributed to increased levels and a greater ZP affinity of lipid rafts in the sperm plasma membrane.
    Developmental Biology 03/2006; 290(1):220-35. · 3.87 Impact Factor
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    J A B Robinson, M M Buhr
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    ABSTRACT: Boars in an artificial insemination centre have been selected for their superior genetic potential, with 'superior' being defined as having traits the customer wants transmitted to his herd. The ability to meet the customers' needs depends on the heritability of the trait, the geneticist's success in devising a selection scheme for the trait in balance with other economically important traits, and the boar's ability to produce sperm that can fertilise oocytes. Genetic evaluation research over the past 20 years has greatly increased the number of traits for which a boar can be selected: currently in the Canadian national program, these include age at 100 kg, backfat at 100 kg, feed efficiency, lean yield and litter size. In the near future, traits that are very likely to be added to this selection list include piglet survival, marbling, loin eye area and structure traits. In Canada, sires are ranked on two estimated breeding value (EBV) indices; one, focused on development of terminal sire lines, is based on the growth and yield traits and another, primarily focused on maternal line development, de-emphasises these traits and incorporates litter size. Boars that are in Canadian AI centres because of their excellent growth traits are typically in the top 5-10% of the national population for terminal sire line index, but they may be only average or substandard for litter size. Conversely, boars selected to be in the top 5-10% for conveying such reproductive traits as litter size may only be in the top 33% for growth traits. The more offspring from a superior boar in either of these indices, the faster the population average for the trait improves. The original sire gets knocked out of the elite group, is culled and replaced by a higher ranked young boar from the now improved general population. Although genetic superiority should govern an AI centre's selection and culling of boars, decision-making in real life is seldom that simple. Selection criteria may be contradictory as above, or a boar with truly superior traits may be excluded because a newly-developed molecular genetics test determines he carries an undesirable gene such as PSS, RN or others being developed. Selection for terminal sire or maternal line traits can ignore important practical factors that affect an AI centre--boars with superior genetics may not produce good semen because skeletal or penile problems prevent ejaculation, or because sperm production is poor due to a genetic flaw, disease, or some other cause. Interestingly, selection pressure for one trait may inadvertently select for a trait that is linked but whose linkage is unrecognised, and such unintentionally selected genes could benefit, harm, or have no effect on production traits. An AI centre serving a variety of customers must select boars in anticipation of their customers' needs (including new, foreign and niche markets). A centre should also review its genetic evaluation results and progeny records, both to critique its own selection success and to try to detect unexpected linkages. Finally, an AI centre needs to predict its own future, selecting not just for production traits for the swine producer, but also for factors that enhance the centre's efficiency including boar conformation and temperament, and sperm quantity, quality and hardiness. Can we select for efficiency? Our colleagues in dairy cattle AI evaluate bull performance--should the swine industry consider evaluation of male fertility traits?
    Theriogenology 02/2005; 63(2):668-78. · 2.08 Impact Factor
  • L H Graham, J Bando, C Gray, M M Buhr
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    ABSTRACT: The Asian elephant (Elephas maximus) population in the wild has been in decline for several decades and breeding in captivity has not been self-sustaining. The use of artificial insemination (AI) can help overcome many of the difficulties associated with breeding elephants in captivity; however, the ability to store semen for extended periods of time is critical to the successful application of AI to elephants. The objective of the present study was to assess the effects of four different semen extenders and the presence of egg yolk on the viability and motility of Asian elephant semen stored at 4 degrees C. High quality ejaculates (n=4) were collected from two Asian elephant bulls by rectal massage. Aliquots of each ejaculate were extended in four different diluents (Beltsville thawing solution (BTS); Tris-citric acid (TCA)/fructose-based; Beltsville F5 (BF5); dextrose-supplemented phosphate-buffered saline (PBS)) with or without egg yolk then cooled and stored at 4 degrees C. The percentages of viable (viability) and motile (motility) sperm were evaluated at 8, 24 and 48 h following collection. The addition of egg yolk significantly reduced the percentage loss in viability from initial collection to 48 h compared to extenders without egg yolk (17.0 +/- 8.2 versus 32.6 +/- 8.9 decline in percent viable sperm in the population, respectively; P<0.05). Extender and egg yolk affected (P<0.005) total motility and percent progressively motile sperm at all evaluation times during incubation. TCA + egg yolk maintained higher (P<0.05) levels of progressive motility compared to other extenders supplemented with egg yolk. These results indicate that Asian elephant semen extended in TCA diluent supplemented with egg yolk can maintain at least 50% viability and motility when stored at 4 degrees C for 48 h.
    Animal Reproduction Science 03/2004; 80(3-4):329-40. · 1.90 Impact Factor
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    Katrina Merkies, Mary M Buhr
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    ABSTRACT: The major obstacle in standardizing techniques to evaluate stallion fertility is the huge variation in ejaculates from different stallions and even among ejaculates collected from the same stallion (1,2). Spermatozoa concentration, total volume, motility, percent live spermatozoa, and percent normal spermatozoa can range greatly (3), and any or all may have an effect on the ability of the ejaculate to fertilize. Cryopreservation of semen results in partial, irreversible membrane damage to the spermatozoa, reducing fertility rates even further. Using current industry protocols for cryopreservation of stallion semen, 50–75% of stallions do not produce ejaculates suitable for freezing (4). Pregnancy rates from natural or artificial insemination have shown little improvement in recent years and this has a significant impact on the economic feasibility of the horse breeding industry. Simple, accurate assessment of the viability of fresh and cryopreserved stallion spermatozoa prior to insemination could improve the reproduction rate in horses (5).
    Methods in molecular biology (Clifton, N.J.) 02/2004; 253:49-58. · 1.29 Impact Factor

Publication Stats

740 Citations
103.58 Total Impact Points

Institutions

  • 1993–2012
    • University of Guelph
      • Department of Animal and Poultry Science
      Guelph, Ontario, Canada
  • 2011
    • University of Saskatchewan
      • College of Agriculture and Bioresources
      Saskatoon, Saskatchewan, Canada
  • 1989–1993
    • University of Manitoba
      • Department of Animal Science
      Winnipeg, Manitoba, Canada
  • 1990
    • Royal Veterinary College
      Londinium, England, United Kingdom