Page 974 - Small Animal Internal Medicine, 6th Edition
P. 974

946    PART VIII   Reproductive System Disorders


            it flows into the clear tubes. There are three fractions in the
            ejaculate. The first is clear, from seminal vesicles. The second
  VetBooks.ir  fraction is white sperm-rich fluid (SRF). The third fraction
            is clear and is prostatic fluid. The SRF is usually released at
            the end of rapid thrusting after the dog has turned. Semen
            evaluation requires the collection of only the first and second
            fractions. Evaluation of a small amount of the more volumi-
            nous prostatic fluid is adequate. If collecting for fresh artifi-
            cial insemination, avoid collecting the clear prostatic fluid.
              The total volume of SRF in a large dog is generally no
            more than 1 to 2.5 mL. After collection is complete, leave the
            AV on the stud until his erection has diminished. This keeps
            the penis more comfortable. Apply some water-soluble lubri-
            cation to the base of the penis, under the AV, to facilitate
            return of the penis within the prepuce. Always check to make
            sure the paraphimosis (penis extruded outside of the
            prepuce) resulting from artificial semen collection resolves.   FIG 54.21
            It is not necessary to walk the dog; he will lose the erection   Canine spermatozoa, phase contrast microscopy.
            in 5 to 15 minutes. Care must be taken to ensure that the
            stud dog has adequately recovered from his erection before
            he is retired; preputial skin and hair can strangulate the tip
            of the penis.                                                                    Detached
                                                                                               head
            SEMEN ANALYSIS
            Semen analysis should include evaluation of sperm mor-
            phology, motility, and concentration. If the clinician is
            uncomfortable with semen evaluation, the sample or a rep-                Distal
            resentative aliquot can be submitted to a commercial labora-     Proximal  droplet  Coiled
                                                                                            tail
            tory for analysis, but motility must be judged immediately       droplet
            postcollection. Normal canine semen has 70% (or greater)
            progressively forward-moving sperm with moderate speed
            and good-quality motility. To evaluate motility, place a drop    “Dag”
            of the sperm-rich fraction (second) on a warmed slide, using     defect
            a pipette. Top with a coverslip and observe under ×10 to ×40                       Bent tail
            magnification. Sperm should swim across the slide in a rela-
            tively straight path, with minimal gyrations (good-quality                            Thickened
            motility) and brisk speed (moderate to fast motility). No                    Pyriform  midpiece
                                                                                          head
                                                                              Acrosomal
            sperm-to-sperm agglutination should occur, but agglutina-        condensation  abnormal
            tion to egg yolk particles in extenders or other cells in semen             midpiece
            can be normal. If motility is poor, prepare another drop on
            a new slide and double-check. Observe individual live,   FIG 54.22
            unstained sperm cells under ×40 magnification for morphol-  Schematic of sperm morphology showing common
                                                                 abnormalities.
            ogy. Abnormal sperm can have coiled tails, proximal drop-
            lets, abnormal shape to heads, double tails or heads, and
            altered acrosomes (Figs. 54.21 and 54.22). The acrosome is   semen morphology with the previously mentioned catego-
            difficult to visualize without phase contrast microscopy. Iat-  ries is helpful. If a high number of morphologic abnormali-
            rogenic damage can cause detached heads and bent tails.   ties occur poststaining, a different methodology may be
            Observing fresh sperm before staining permits evaluation   advisable. Note the presence of epithelial cells, white blood
            for stain-induced morphologic abnormalities. Prepare   cells (WBCs), and RBCs as well (record as 1-4+/HPF). Sperm
            another slide with the pipette as you would a peripheral   counts can be performed by using a hemocytometer and
            blood smear, air dry, and stain for morphologic analysis.   Unopette. Alternatively, the automated Spermcue (MOFA
            Both Wright-Giemsa and eosin-nigrosin stains are com-  Inc.) produces a very accurate automated sperm count. Mul-
            monly used. At least 100 to 200 sperm should be tallied for   tiply the number of sperm per milliliter by the volume of the
            morphology, noting both normal cells and sperm cells with   SRF to obtain the number of sperm per ejaculate. Normal
            head abnormalities (misshapen, double), neck abnormalities   dogs have 200 to 400 million (up to a billion) sperm per
            (proximal droplets), and tail abnormalities (distal droplets,   ejaculate. Normal toms’ average semen volume varies by the
            coiled, double). Using a differential cell counter labeled for   method of collection (10.5-233 µ/L); sperm count 21 to 57
   969   970   971   972   973   974   975   976   977   978   979