Bovine Reproduction. Группа авторов

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Bovine Reproduction - Группа авторов


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of a mature bull with small hyperechoic foci distributed throughout the testis parenchyma.

Photo depicts sagittal view of a testis with small hyperechoic foci (large arrow) surrounding the mediastinum (small arrow) suggestive of lesions in the straight ducts that drain the seminiferous tubules into the rete testis. Photo depicts sagittal view of a testis with multiple linear radiating hyperechoic lesions, two of which are highlighted by the smaller arrows. A normal mediastinum testis is shown (large arrow). Photo depicts sagittal view of the right ventral testis of an aged beef bull. Histologically, the hyperechoic lesion (arrow) was a Sertoli cell tumor. Photo depicts sagittal views of the left and right testes of a yearling dairy bull. The left testis is normal, while the hyperechoic areas of the right testis cast prominent dark shadows in the distal tissue and represent areas of mineralization.

      Barth et al. [15] have proposed a scoring system for fibrotic lesions in the bull testis based on the size and frequency of hyperechoic lesions detected by ultrasonography in a single transmediastinal plane. They found that the occurrence of fibrotic lesions in young bulls aged between 3 and 20 months was not associated with decreased semen quality. This is consistent with their histologic findings, where seminiferous tubules within the area of fibrosis were generally affected, but immediately adjacent germinal tissue was quite often completely normal. However, bulls that experienced a dramatic increase in fibrosis score at a second examination (≥4 points, 4–13 months later) were more likely to have poor semen quality than bulls that did not experience this degree of change [15]. While bulls in this report with up to 50% of their parenchyma affected were able to produce mostly normal sperm, it is reasonable to suspect that they would have reduced production capacity.

      The cause of fibrotic lesions in the testis is unknown. Possible etiologies include infectious or inflammatory conditions, developmental defects of the seminiferous tubules or their connecting ducts, autoimmunity, degenerative conditions, or aging. Ram testes inoculated with Trueperella pyogenes (formerly Arcanobacterium pyogenes) eventually developed hyperechoic lesions that consisted of fibrotic tissue [16]. A severe outbreak of bovine respiratory syncytial virus (BRSV) in a group of bulls was associated with an increased prevalence of fibrotic lesions in one report, though a cause‐and‐effect relationship could not be confirmed [15]. On the other hand, scrotal insulation resulting in a dramatic decrease in semen quality did not cause fibrosis or any other ultrasonically detectable change in the testis within four months [17] or six months [12] after the insulation event. A progressive fibrosis that is more marked in the ventral testis has been described as a histologic feature of aging in the bull [18].

Photo depicts transverse view of the testis containing two discrete hypoechoic wedge-shaped areas (between arrows) of unknown etiology or significance. Photo depicts sagittal view of the left testis of a mature Holstein bull that presented with a complaint of low semen volume and oligospermia. Note the hypoechoic distension of the rete testis (dark linear area between arrows). The distension was secondary to a complete outflow obstruction resulting from the absence of the epididymal body on this side.
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