Crampy or Progressive Posterior Paralysis in Mature Cattle

Records from 12,387 dairy bulls of five breeds, and 448 beef hulls of four breeds, were studied toestablish the frequency and age at occurrence of the crampy condition, and to determine if evidence of genetic influence existed.The 323 dairy and ten beef bulls which were affected represented all nine breeds.Chi-square analysis showed that the frequency of occurrence differed significantly (P < 0.01) among the dairy breeds.Death or last effective service of affected bulls occurred at a mean age of 10.02 ± 2.49 yr.Numerous familial relationships were demonstrated; differences in frequency of occurrence in sire groups, and in lines and line-crosses, were significant (P < 0.04 and P < 0.01, respectively).Thus~ a genetic background of the condition was indicated strongly.Although multiple gene inheritance was not discounted, inheritance was suggested as a single recessive factor with incomplete penetranee.A syndrome characterized by intermittent spastic contraction of the muscles of the rear legs and back of mature cattle of both sexes has been recognized for some years.It has been called crampy (krampfigkeit), neuromuscular spasticity, posterior paralysis, progressive posterior paralysis, spastic syndrome, stretches, and other names.The cause of this syndrome has not been established ; however, a familial pattern of occurrence has been reported.Crampy has shortened the useful lives of numerous bulls and cows.Crampy occurs in otherwise normal adult cattle.Symptoms become evident when animals are three or more years of age and usually are mild for the first few years.The earliest signs are slight muscle spasms which appear when animals arise, back up, or move suddenly.As the condition progresses the muscles of one or both rear legs go into spasmodic contractions that last for a few seconds to several minutes.Animals often extend or flex their legs, one at a time, during these episodes.When both rear legs are affected, they remain on the ground and are extended backward during an attack; hence, the term stretches.The condition becomes progressively more severe over a period of months or years until the muscles over the back, and eventually much of the body, are involved.Because physical activity is necessary to induce an attack, animals affected severely usually remain recumbent.Animals in the advanced stages have reduced value.Roberts (4) observed or assembled reports of 65 cases, 33 bulls and 32 cows.Affected cattle included two full brothers, two half-brothers, three sons of the t~ecelved for publication November 18, 1960.