A historical review of the downer cow literature is presented in order to provide a background for understanding current research. Initially thought to be an entity separate from parturient paresis, the condition has eventually come to be regarded as a complication of parturient paresis. Since many other factors also contribute to the syndrome, it is difficult to define precisely what is meant by the term 'downer cow'. A hypothesis that many primary factors, including parturient paresis, may cause the initial stage of recumbency is presented. This is followed by secondary muscle and nerve damage caused by tissue compression. This damage leads to permanent recumbency even if the primary factors have been ameliorated by therapeutic measures. Support for this hypothesis is given from the literature on cattle and other species and from recent experiments on cows. The concepts are applied to a discussion of prevention and therapy of downer cow cases.

A retrospective study of 2,912 cryptorchid dogs identified 14 breeds with significantly high risk. Among six distinct closely interrelated breed groups (e.g., toy, miniature, and standard poodles), the risk in the smaller breed was always greater than that in the larger relative, suggesting that genetically influenced maldescent could be, in part, related to physical size or the rate of growth of the involved structures. Testicular tumors were diagnosed in 5.7% of the cryptorchid dogs; half had only Sertoli cell tumors, one-third had only seminomas. The relative risk for Sertoli cell tumor or seminoma was not directly related to a familial risk for cryptorchism. Using the health experience of a control population composed of male dogs with anal sac disease (N = 4,184), there is an estimated relative risk of 9.2 in cryptorchid dogs to develop a testis tumor (95% confidence interval, 5.9-14.3) and 4.2 in dogs with inguinal hernia (95% confidence interval, 1.8-9.5). Considering that the anatomical development of the genital tract, testis descent, and tunic relationships in dog are very similar to that in man, and that the associations of cryptorchism and inguinal hernia with testis neoplasms are also similar, the dog should be an excellent model system to further investigate the causes of human cryptorchism.

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Twelve cases of cryptorchidism were found in a colony of Minature Schnauzer purebred and crossbred dogs. At least nine affected dogs were derived from the same sire directly or indirectly. Of 12 affected dogs, five cases were unilateral and seven were bilateral. Eight of the 12 cases were subjected to anatomic study. Fixation of affected organs was by vascular perfusion or immersion. Testes were separated from epididymides and both were weighed. All unilateral retained testicles were on the right side, and right sided bilaterally retained testes were always smaller than their left sided counterparts. With only one exception, ectopic testes were in the abdominal positon. Developmentally, the morphologic appearance of the epididymis of abdominal testes was very primitive in bilateral cases but nearly normal in the unilateral cases. Degree of inbreeding was greater for bilateral cases than unilateral cases. High incidence of cryptorchidism in this colony provided good evidence for hereditary nature of the condition in the Miniature Schnauzer dog. Morphologic observations were suggestive of a multiple gene defect.