Biomedical subjects

A de Kruif

Publications and source records attributed to A de Kruif.

At least 19 recordsLinked to original sources

PubMed2006

Tetracycline-resistance in lactose-positive enteric coliforms originating from Belgian fattening pigs: degree of resistance, multiple resistance and risk factors.

Between March and October 2003 a field study was conducted in 50 randomly selected pig herds to assess the degree of tetracycline-resistance in lactose-positive enteric coliforms (LPEC) originating from fattening pigs and to evaluate the combined effects of various husbandry conditions on the development and persistence of antimicrobial-resistant bacteria. Data on housing, management and antimicrobial-drug consumption were collected, as well as faecal samples at three production stages: end of the nursery period (mean age: 72 days), end of the grower period (mean age: 125 days) and end of the finisher period (mean age: 186 days). The degree of tetracycline-resistant LPEC was determined by means of an agar dilution method. Tetracycline-resistant LPEC were found in every herd. The overall degree of tetracycline-resistance in LPEC was 56.8% (S.D. 22.4%). Only a very weak relation was found between the degrees of TETR in the different production stages within the same herd, indicating that the degree of TETR is mainly associated with the production stage rather than with the farm as a whole. The risk factor analysis showed that besides the antimicrobial-drug use, other factors like inside pen hygiene can influence the development and maintenance of antimicrobial-resistant bacteria in the gastrointestinal tracts of pigs. It was also observed that tetracycline-resistance in commensal Escherichia coli is often linked with resistance to other antimicrobial drugs like ampicillin and trimethoprim-sulphonamides. These results illustrate that the epidemiology of antimicrobial resistance is influenced by antimicrobial-drug use, cross-resistance development and non-antimicrobial risk factors.

Animal Husbandry↗

PubMed2006

Protein variability among Mycoplasma hyopneumoniae isolates.

Sodium-dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was used to study the protein variability of Mycoplasma hyopneumoniae isolates. Fifty-six M. hyopneumoniae isolates from 6 different countries and 37 different herds were used. From eight herds, more than one isolate was available. All SDS-PAGE patterns of isolates originating from different herds were clearly divergent. Intra-species protein variability was quantified using the reference strain J and seven field strains all obtained from different herds and classified according to virulence. Between the field strains, a variability of 25% was found, while the culture-adapted strain J was clearly divergent and showed 30% variability with the field strains. No clustering according to virulence was obtained, but a protein band of about 181kDa was present in the two highly virulent isolates whereas this protein band was absent in the moderately and low virulent isolates. Protein patterns of isolates derived from different animals from the same herd, were identical or differed in only a few protein bands. This study clearly indicates that, in agreement with previous studies on genomic diversity of M. hyopneumoniae isolates, proteomic variability within the species is high. Our study did not find clear evidence that more than one M. hyopneumoniae isolate circulates within a herd at a specific time point. The minor differences found between M. hyopneumoniae isolates from the same herd might reflect the organism's ability to alter its proteomic expression profile under field conditions.

Animals↗

PubMed2006

Interactions of highly and low virulent Mycoplasma hyopneumoniae isolates with the respiratory tract of pigs.

Mycoplasma hyopneumoniae is the etiological agent of swine enzootic pneumonia, a chronic nonfatal disease affecting pigs of all ages. To obtain better insight in the mechanisms responsible for differences in virulence between highly and low virulent M. hyopneumoniae isolates, 23 caesarean-derived, colostrum-deprived piglets were randomly assigned to three groups. Groups 1 and 2 consisted of nine animals each, which were intratracheally inoculated at 1 week of age with a highly or a low virulent isolate of M. hyopneumoniae, respectively. The remaining five animals were inoculated with sterile culture medium. Animals were euthanized at 5, 10, 15 and 28 days post-inoculation (DPI). Animals inoculated with the highly virulent isolate had more neutrophils in BAL fluid at 10, 15 and 28DPI compared to the other groups. At 10 and 15DPI, animals in the highly virulent group had significantly higher concentrations of TNF-alpha in BAL fluid. IL-1beta concentration in this group was higher at 5 and 28DPI compared to the other groups. From 10DPI onwards, significantly higher titres of M. hyopneumoniae were detected in the BAL fluid of animals inoculated with the highly virulent isolate compared to animals inoculated with the low virulent isolate. Additionally, the in vitro generation time of the highly virulent M. hyopneumoniae isolate was significantly shorter than that of the low virulent isolate. The present study indicates that the difference in pathogenicity between the highly and low virulent isolates is associated with a faster in vitro growth, a higher capacity to multiply in the lungs and the induction of a more severe inflammation process by the highly virulent isolate.

Animals↗

PubMed2006

Comparison of sperm quality of Belgian Blue and Holstein Friesian bulls.

Few data are currently available on sperm quality of Belgian Blue (BB) bulls. The present study compared sperm quality of BB to Holstein Friesian (HF) bulls of several age categories, by means of a classical semen evaluation. Volume and concentration, and consequently total sperm output depended largely on age. Gross, total, and progressive motility, % live and % normal spermatozoa were significantly lower in the BB breed. Primary sperm abnormalities, such as nuclear vacuoles, midpiece defects and cytoplasmic droplets which were noticed most frequently, occurred far more in the BB breed. Hence, disturbances in spermiogenesis are deemed to be the cause of the poorer BB sperm quality. Since these sperm abnormalities occur significantly more in the BB breed than in the HF breed, it seems as if the BB breed is genetically predisposed to a higher susceptibility to environmental stresses which are known to interfere with normal spermiogenesis. The small scrota typical of the inbred BB breed might in part be responsible for this, and therefore selection for larger scrota in the BB breed is advisable.

Age Factors↗

PubMed2006

Evaluation of epididymal semen quality using the Hamilton-Thorne analyser indicates variation between the two caudae epididymides of the same bull.

Epididymal semen is being more often considered as a potential source of valuable genes for genome resource banks. To utilize this resource as efficiently as possible, storage and freezing fertility and preservation characteristics of epididymal semen have to be examined. Because semen quality should be assessed as objectively as possible, we introduced computer assisted sperm analysis (CASA) of epididymal bull semen. The aims of this study were: to determine the quality of fresh cauda epididymal bull sperm, conventionally and by CASA (Hamilton-Thorne Ceros 12.1); to compare epididymal sperm movement with the motion characteristics of ejaculated semen; and to investigate whether equality of semen characteristics exists between both caudae epididymides of the same bull. In experiment 1, it is shown that epididymal sperm has a lower motility (total: 48.7% versus 79.9%, p < 0.0001 and progressive: 34.4% versus 58.4%, p < 0.0001) and moves less straight (80.5% versus 84.5%, p < 0.0009) with a higher amplitude (6.1 microm versus 5.0 microm, p < 0.0001) than ejaculated semen. The epididymal straight line velocity (85.2 microm/s versus 98.3 microm/s, p < 0.0001) is lower, but the curvilinear velocity (173.5 microm/s versus 156.4 microm/s, p < 0.0001) is higher than those of ejaculated semen. The data in experiment 2 are analysed to determine equality, rather than to find a difference. They illustrate that mean differences, for most semen parameters, between the semen from paired caudae epididymides, deviated more than 20% from the average values of these parameters from all bulls; the exceptions (those parameters within 20% of the average for all bulls) were the percentage of live spermatozoa, the linearity of sperm movement, the weights of testis and epididymis, the weights of the cauda epididymis alone, the volumes, and the amplitudes of movement of the semen (p < 0.05). The mean differences between the percentage of live spermatozoa and the amplitude of movement of the epididymal semen of both epididymides of one bull, were the only values smaller than 10% of the average value of this parameter (p < 0.05). This implies that sperm from one cauda epididymis should not be used as a control for the other because, for most of the semen parameters (concentration, morphology, motility, and beat cross frequency), equality between caudae epididymides of the same bull could not be established.

Animals↗

PubMed2006

A multiplex PCR to identify porcine mycoplasmas present in broth cultures.

Mycoplasma hyopneumoniae, Mycoplasma hyorhinis and Mycoplasma flocculare can be present in the lungs of pigs at the same time. These three mycoplasma species all require similar growth conditions and can be recovered from clinical samples using the same media. We have developed a multiplex PCR as a helpful tool for rapid differentiation of these three species in the course of isolation. Based on the 16S ribosomal DNA sequences, three different forward primers and a single reverse primer were selected. Each forward primer was compared to available mycoplasma sequences, showing the primers to be specific. The three amplification products observed of 1129 bp (M. hyorhinis), 1000 bp (M. hyopneumoniae) and 754 bp (M. flocculare) were clearly distinguishable on a 1% agarose gel. In addition, no cross-reaction with Mycoplasma hyosynoviae, another porcine mycoplasma, was noted. This multiplex PCR using the proposed set of primers is the first reported assay that allows the simultaneous identification of the different Mycoplasma species isolated from the lungs of pigs.

Animals↗

PubMed2006

Detection of tetracycline-resistant and susceptible pasteurellaceae in the nasopharynx of loose group-housed calves.

The aim of the present study was to determine which Pasteurella and Mannheimia species are present in the upper respiratory tract of healthy calves with no history of antimicrobial treatment prior to sampling. The presence of subpopulations of tetracycline-resistant Pasteurellaceae was also investigated. Nasal swabs from 61 loose group-housed, clinically healthy calves, 1 to 4 months old, from 16 dairy herds were inoculated aerobically on a selective medium (Columbia agar with 5% ovine blood and 16 mg/L bacitracin) with or without 4 mg/L oxytetracycline (OTC). A total of 43 strains belonging to the family Pasteurellaceae were isolated from 38 calves (62.3%) out of 13 herds (81.3%). The predominant organisms were Pasteurella multocida subsp. multocida (57.4%), Mannheimia varigena (4.9%) and M. haemolytica (3.2%). Growth of Pasteurellaceae on the OTC-containing medium was seen only with samples from two herds (6 animals; 9.8%), and on only one farm this proved to be an OTC-resistant subpopulation. Minimum inhibitory concentration (MIC) determinations by means of agar dilution confirmed a low prevalence of OTC-resistant Pasteurellaceae, with overall MIC(50) and MIC(90) values of 0.25 and 32 mg/L, respectively. These data do not support the hypothesis that the relative high frequency of tetracycline-resistant P. multocida isolates from fatal cases of bovine respiratory disease is related to the presence of minor tetracycline-resistance subpopulations within this species.

Animals↗

PubMed2006

Effects of beta-OH butyrate on bovine granulosa and theca cell function in vitro.

In this study, the effects of beta-OH butyrate (BHB) levels, associated with a negative energy balance, on bovine granulosa and theca cell function were investigated in vitro. Granulosa and theca cells of healthy large follicles (>8 mm), obtained from slaughterhouse ovaries, were cultured in serum free medium containing 0, 0.5, 1 or 1.5 mm BHB and 3 mm glucose, to mimic the situation in the early postpartum dairy cow. Hormone concentrations (progesterone, oestradiol-17beta and/or androstenedione) in spent medium and cell numbers were measured after 48 h of culture. No effects of BHB on theca cell numbers or on steroid production were observed. In granulosa cells, all BHB treatments evenly increased cell numbers (p < 0.05), while they reduced progesterone and oestradiol-17beta production per cell (p < 0.05). These effects may be attributed to the use of BHB as energy source which is however differently metabolized than glucose. Conclusively, in the presence of physiological glucose concentrations BHB can modulate granulosa but not theca cell function in vitro.

3-Hydroxybutyric Acid↗

PubMed2006

The in vitro development of bovine oocytes after maturation in glucose and beta-hydroxybutyrate concentrations associated with negative energy balance in dairy cows.

Negative energy balance (NEB) in high yielding dairy cows early postpartum may affect oocyte quality. Therefore, we tested the effect of two different beta-hydroxybutyrate (BHB) and glucose concentrations, which are associated with subclinical or clinical ketosis, during in vitro maturation (IVM) on the developmental competence of bovine oocytes. In Expt 1, subclinical ketosis conditions were imitated. Oocytes were matured in four different serum-free media with two glucose concentrations (g1=2.75 mm or G1=5.5 mm glucose) and with or without BHB (BHB1=1.8 mm BHB). Following maturation groups were used: g1, G1, g1:BHB1 and G1:BHB1. In Expt 2, clinical ketosis conditions were mimicked by using the concentrations: g2=1.375 mm or G2=3.1 mm glucose and BHB2=4.0 mm BHB. The combinations used were: g2, G2, g2:BHB2 and G2:BHB2. After IVM and in vitro fertilization (IVF), presumptive zygotes were routinely cultured for 7 days in synthetic oviduct fluid [SOF; 5% fetal calf serum (FCS)]. At 48 h and 8 days pi, cleavage rate and number of blastocysts were recorded respectively. The results demonstrated that the maturation conditions mimicking subclinical (g1:BHB1) and clinical ketosis (g2 : BHB2) resulted in an impaired developmental competence of the oocyte after maturation. Especially the moderately low (g1) or extremely low glucose (g2) concentrations were responsible for this detrimental effect that was associated with a blocked cumulus expansion. Only in moderately low glucose conditions (g1:BHB1), BHB exerted an additive toxic effect during oocyte maturation resulting in a reduced blastocyst rate. Conclusively, our results may suggest that subclinical and clinical ketosis can affect the oocyte's developmental competence most likely through a directly adverse effect of the low glucose concentrations on oocyte maturation. Only in subclinical conditions this harmful effect may be aggravated by BHB.

3-Hydroxybutyric Acid↗

PubMed2006

Role of two glycosidases (alpha-mannosidase and beta-N-acetylglucosaminidase) on in vitro bovine embryonic development.

Glycosidases are enzymes that might play a role in embryonic development. The aims of the present project were to evaluate if bovine in vitro produced embryos: (1) release beta-N-acetylglucosaminidase (beta-NAGASE) and alpha-mannosidase in culture medium and (2) to investigate if these glycosidases may be used as markers of embryo quality. Bovine embryos were obtained using routine methods for IVM, IVF and IVC. Two experiments were done [(experiment 1: culture of embryos in the same droplet until day 7 and experiment 2: separation and transfer of embryos to new droplets at the morula stage (day 6)]. Samples were collected on day 7 (experiment 1) and on days 6 and 7 (experiment 2). The results of the present study are summarized as follow: (i) Embryos release both glycosidases. (ii) The activity of both glycosidases was significantly lower (p<0.05) in droplets with degenerate embryos compared to droplets without degenerate embryos. (iii) The activity of beta-NAGASE was higher in droplets which contained morulae compared to droplets without morulae. In conclusion, embryos release both glucosidases during their development, while degenerate embryos release less beta-NAGASE and alpha-mannosidase compared to good embryos. Furthermore, beta-NAGASE secretion seems to be related to retarded morulae.

Acetylglucosaminidase↗

PubMed2006

Accuracy of trans-abdominal ultrasound pregnancy diagnosis in sows using a linear or sector probe.

The assessment of an early and reliable pregnancy diagnosis in sows is very important for limiting the number of non-productive days in sow herds. The aim of the present study was to investigate the accuracy of trans-abdominal ultrasound detection for early pregnancy diagnosis in sows under field conditions. Particular attention was paid to the time when a reliable diagnosis can be made, and to possible differences between two commonly used types of scanners. In total, 202 sows from two herds were tested daily with scanners A (linear transducer of 5 MHz) and B (sector transducer of 3.5 MHz) from day 16 until 25 after insemination. Ninety-three percentage of the sows were pregnant 36 days after insemination. Using ultrasound, the first pregnancy could be detected already 18 days after insemination. The sensitivity, specificity and overall accuracy were higher than 95% from day 24 (scanner A) or day 23 (scanner B) post-insemination onwards. The positive predictive values from day 19 onwards were consistently higher than 95% with both types of scanners, whereas the negative predictive values were consistently low for both scanners during the entire period. The sensitivity of testing tended to be slightly lower in sows with a litter size of <10 total born piglets, compared to sows with 10 or more piglets. In conclusion, pregnancy diagnosis in sows using trans-abdominal ultrasound testing can be assessed quickly and reliably under field conditions from day 23 of gestation onwards. Predictive values of positive test results were high in these herds, whereas those of negative test results were low. This implies that sows with a negative test result early in pregnancy should be retested later.

Abdomen↗

PubMed2005

Breeding soundness and libido examination of Belgian Blue and Holstein Friesian artificial insemination bulls in Belgium and The Netherlands.

Data on breeding soundness and libido evaluations in Belgian Blue (BB) bulls are scarce. The present study compared results of breeding soundness and libido evaluations of young BB bulls to young Holstein Friesian (HF) bulls prior to acceptance into an AI program. Breed differences for breeding soundness exist between BB and HF bulls, as 93.7% of the young BB bulls failed the breeding soundness examination (BSE) compared to 59.3% of the HF bulls (P=0.0005). Within the BB breed, differences were present between bulls of different ages, and bull selection for better fertility with increasing age apparently influenced the results. The number of reasons for which bulls failed the test differed between the age groups in the BB breed, whereas a tendency for more failure reasons in the BB breed was noticed in the breed comparison. The most important reasons for failure were sperm morphology and scrotal circumference (SC), but far more BB bulls failed for these traits compared to the HF breed (82.8% versus 56.0% and 43.8% versus 17.6% in the BB and the HF breed for sperm morphology (P=0.0005) and SC (P<0.0001), respectively). The high proportion of BB bulls with a substandard SC and poor sperm morphology might suggest an increased prevalence of testicular hypoplasia or degeneration within this breed. Concerning libido, the reaction time did not differ either between breeds or between age groups within the BB breed, whereas mounting enthusiasm, although not different between the two breeds, did decline with increasing age, probably due to the greater mating experience of the older bulls. All in all, libido did not seem to be different between the breeds.

Age Factors↗

PubMed2005

Effect of non-esterified fatty acids on bovine theca cell steroidogenesis and proliferation in vitro.

Elevated serum non-esterified fatty acid (NEFA) levels associated with a negative energy balance (NEB) may affect ovarian function and hence reproductive performance in high-yielding dairy cows. We have investigated the individual and combined effects of the three major NEFAs on bovine theca cell proliferation and steroidogenesis in vitro. Theca cells from healthy large follicles (>8 mm) obtained from slaughterhouse ovaries were cultured in serum free medium in the presence of 0, 50, 150 and 200 microM of palmitic acid (PA; C16:0); 0, 50, 150 and 250 microM of stearic acid (SA; C18:0); and/or 0, 50, 150 and 250 microM of oleic acid (OA; C18:1). Progesterone and androstenedione concentrations were measured in spent medium after 48 h of culture and cell numbers were determined spectrophotometrically per culture well. Cell viability was assessed by annexin-V FITC/propidium iodide staining. Only the treatment with 200 microM of PA inhibited cell proliferation (P<0.001) when tested individually, both of the mixtures tested (M1=100 microM of PA, 130 microM of SA and 140 microM of OA; M2=200 microM PA, 260 microM of SA and 280 microM of OA) reduced cell numbers (P<0.001). Progesterone and androstenedione production, both per well and per 10(4) cells, were not affected by any of the treatments, with the exception of M2. This mixture reduced progesterone production per well and per 10(4) cells (P<0.05). The effects observed were most likely caused by the cytotoxic action of the NEFAs, as demonstrated by the increased percentage of early apoptotic (M1) and late apoptotic/necrotic cells (M1 and M2) in the combination treatments (P<0.05). When combined, elevated physiological concentrations of PA, SA and OA can modulate theca cell proliferation and steroidogenesis in vitro by reducing theca cell viability. These NEFAs may be one of the mediators through which NEB compromises ovarian functioning and thus fertility in high-yielding dairy cows.

Androstenedione↗

PubMed2005

Comparison of embryo quality in high-yielding dairy cows, in dairy heifers and in beef cows.

The purpose of this study was to compare embryo quality of lactating Holstein Friesian cows (LHFC), non-lactating Holstein Friesian heifers (NLHFH) and Belgian Blue beef cows (BB) and to identify factors that are associated with embryo quality in LHFC and NLHFH. After superovulation and embryo recovery at Day 7, embryos (n=727 from 47 LHFC, 27 NLHFH and 50 BB) were scored morphologically for quality, colour and developmental stage. Blood samples and data concerning parity, age, milk production and management were collected. Data were compared univariably between the three groups. A multivariable regression model was built with quality and colour of the LHFC and NLHFH embryos as dependent variables. Only 13.1% of LHFC embryos were categorized as excellent compared to 62.5% and 55.0% of the embryos in NLHFH and BB, respectively. Almost none of the NLHFH or BB embryos displayed a dark appearance of the cytoplasm compared to 24.1% of the LHFC embryos. Only 4% of all LHFC embryos reached blastocyst stage compared to 23.2% and 17.3% in NLHFH and BB. Based on the multivariable regression analysis, "physiological status" (lactating or not) together with the serum total protein concentration of LHFC and NLHFH, was significantly associated with embryo quality and colour. Thus, LHFC display an inferior embryo quality compared to NLHFH and BB. Producing milk or not seems to be significantly associated with embryo quality. Therefore, reduced embryo quality on Day 7 following AI, could be an important factor in the subfertility problem in modern high-yielding dairy cows.

Animals↗

PubMed2005

Efficacy of in-feed medication with tylosin for the treatment and control of Mycoplasma hyopneumoniae infections.

The efficacy of in-feed medication with tylosin for the treatment of enzootic pneumonia was examined in an experimental Mycoplasma hyopneumoniae infection model. One group of 10 conventional M. hyopneumoniae-free pigs was inoculated intratracheally with a highly virulent field isolate of M. hyopneumoniae; a second group of 10 pigs was inoculated in the same way and after 12 days was given tylosin at 100 mg/kg feed for 21 days; a third group of 10 pigs was inoculated with sterile culture medium, and these pigs were not given tylosin. The pigs were examined daily for clinical signs and each pig was given a respiratory disease score. Thirty-three days after they had been infected the pigs were euthanased, the lung lesions were quantified and samples of lung were processed for immunofluorescence testing for M. hyopneumoniae. The mean (sd) respiratory disease and lung lesion scores were significantly higher (P<0.05) in both the infected groups than in the uninfected group. Between 23 and 33 days after infection the mean respiratory disease score of the pigs treated with tylosin was 0.54 (0.22), significantly (P<0.05) lower than that of the infected pigs which were left untreated, 1.54 (0.46); similarly, their average lung lesion score, 1.72 (1.20), was significantly lower than that of the untreated pigs, 5.27 (3.85).

Animal Feed↗

PubMed2005

Risk factors for bovine herpesvirus-1 seropositivity.

This paper reports the investigation of risk factors for bovine herpesvirus-1-seropositivity, based on a cluster-sample survey of the Belgian cattle population. This serosurvey was carried out in 1998 in 309 randomly selected unvaccinated herds of all types (dairy, mixed and beef) were all bovids (N = 11,284) were sampled. Older and male cattle had higher seroprevalence. Origin (homebred or purchased) and herd size interacted; for smaller herds (< or = 50 cattle on the premises), purchase status and larger herd size were risk factors, whereas these effects were not observed for larger herds.

Age Factors↗

PubMed2005

Apoptosis in cumulus cells, but not in oocytes, may influence bovine embryonic developmental competence.

Aim of our study was to clarify if the occurrence of apoptosis in oocytes and cumulus cells is correlated to bovine oocyte developmental competence. The cumulus-oocyte complexes (COCs) were selected according to cumulus status: G1 with more than five layers of compact cumulus cells, G2 with one to five layers of compact cumulus cells and G3 with expanded cumulus cells. The degree of apoptosis in cumulus cells and oocytes measured by caspase staining and TUNEL assay before and after maturation, and 24 h post-insemination was compared to the cleavage, blastocyst formation and hatching rates of each group. Highest cleavage, blastocyst and hatching rates were found in cumulus-oocyte complexes with more than five layers of compact cumulus cells, but no apoptosis was detected in immature or in vitro matured oocytes, regardless of the cumulus status. Many cumulus cells contained active caspases before maturation, but caspase activity declined dramatically after maturation. TUNEL positive cells were rarely observed in each cumulus-oocyte complex upon oocyte recovery, but a huge increase of them was seen after in vitro maturation. Significantly more TUNEL and caspase positive cells were found in G2 cumulus-oocyte complexes. Our results suggest that: (i) oocyte apoptosis does not account for the inferior oocyte quality of G2 and G3; (ii) apoptosis occurs in cumulus cells regardless of the number and compactness of cumulus cells; and (iii) the degree of apoptosis in the compact cumulus-oocyte complexes (G1 and G2) is negatively correlated to the developmental competence of oocyte.

Animals↗

PubMed2005

New techniques for the assessment of canine semen quality: a review.

Until recently, canine semen assessment was routinely performed by conventional light microscopic techniques. The limitations of these methods include subjectivity, variability, the small number of spermatozoa analyzed, and poor correlation with fertilizing potential. The last decade, several new in vitro techniques have been introduced for canine semen assessment that enable a more detailed evaluation of several sperm characteristics. Numerous fluorescent staining techniques have been developed for the evaluation of specific sperm characteristics and functions, including plasma membrane integrity, capacitation status and the acrosome reaction. By combining fluorescent stains, several functional sperm characteristics can be assessed simultaneously. Moreover, by means of flow cytometry, large numbers of fluorescently labelled spermatozoa can be analysed in a short interval. Following thorough standardization and validation, computer-assisted sperm analysis systems provide objective and detailed information on various motility characteristics and morphometric dimensions that cannot be identified by conventional light microscopic semen analysis. In vitro assays, evaluating the capacity of canine spermatozoa to bind to the zona pellucida or oviductal explants, or to penetrate the oocyte, provide additional information on canine gamete interaction that may be useful in predicting the fertilizing potential of spermatozoa. Although substantial improvements have been made in canine semen assessment, surprisingly few parameters were correlated with in vivo fertility. Therefore, further research is required to determine which sperm characteristics are of clinical value for predicting the in vivo fertility in dogs.

Acrosome Reaction↗