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A genetic disease in cattle, progressive degenerative myeloencephalopathy (weaver disease), is assodated with increased milk production. This association could result from population stratification, from a pleiotropic effect of a single gene, or from linkage disequilibrium between the gene causing weaver disease and a quantitative trait locus (QTL) for milk production. To test these hypotheses, we performed an extensive linkage study in a bovine pedigree segregating for the weaver condition and identified a microsatellite locus (TGLA116) closely linked to the weaver gene (zma, 8.15; 9, 0.03). TGLA116 and, by extension, the weaver locus were assigned to bovine synteny group 13. This microsatellite can be used to identify weaver carriers, to select against this genetic defect, and to study the effect of the corresponding chromosomal region on milk production in Brown Swiss and other breeds of cattle.The majority of traits selected in livestock production are quantitative traits; i.e., the individual phenotype reflects the action of several genes, confounded by environmental effects. Mapping the underlying genes or quantitative trait loci (QTLs) should allow for marker-assisted selection, which is expected to increase the rate of genetic progress. 11 However, because the contribution of individual QTLs to the overall phenotypic variance may be modest, their mapping may require the study of very large population samples. Several strategies have been proposed to reduce the number of individuals to be analyzed. These strategies include selective genotyping, progeny testing, interval mapping, the simultaneous search for multiple QTLs, and the use of DNA pools (1-3, **).An alternative strategy consists of exploiting the associations that are sometimes found in selected populations between an unrelated monogenic trait and a quantitative trait under selection. Association between a monogenic and a quantitative trait can result from population stratification, from the pleiotropic effect of a single gene on both the monogenic and the quantitative trait, or from genetic linkage between the gene underlying the monogenic trait and a QTL. In the last two cases, genetic mapping of the monogenic trait leads to the concomitant mapping of a QTL. Examples of such associations in domestic animals include hyperkalemic periodic paralysis and muscularity in Quarter horses (4), malignant hyperthermia and the porcine stress syndrome/ pale soft exudative meat syndrome (PSS/PSE) in pigs (5), and weaver disease and increased milk production in cattle (6).The weaver syndrome in cattle (7-11) is characterized by the appearance, between 5 and 8 months of age, of progressive signs of pelvic limb paresis, ataxia, and proprioceptive placing deficits. Affected animals are mentally alert and reveal normal motor and sensory reflexes. Long-standing cases exhibit atrophy of the flexor and extensor muscles of the hip and stifle. Both males and females have atrophied gonads. Histological examination reveals extensive Wallerian degeneration in the...

Abstract. Nature and cause of bilateral ocular dermoids were investigated by field studies, pedigree analysis, clinical examination, light microscopy, scanning electron microscopy, and transmission electron microscopy. It was determined that ocular dermoids in Hereford cattle are a genetically transmitted defect; characteristics of autosomal recessive and polygenic inheritance were observed. Calves typically were affected bilaterally with multiple, connected ocular growths that clinically, histologically, and ultrastructurally mimicked normal haired skin. Sites most commonly involved included ventro-lateral limbus, third eyelid, medial canthus, eyelid and conjunctiva. Centro-corneal and anterior segmental dermoids also were observed.

Abstract. Gross changes and other necropsy findings in 36 purebred Brown Swiss cattle affected with bovine progressive degenerative myeloencephalopathy were nonspecific. Primary microscopic lesions were confined to the central nervous system, specifically the white matter of the spinal cord, axons in some brainstem nuclei, and Purkinje cells of the cerebellar cortex.Spinal cord lesions involved only the white matter and consisted of axonal degeneration, loss of axons and myelin, and status spongiosus. Axonal degeneration was characterized by swelling and fragmentation of the axoplasm or formation of large, discontinuous swellings referred to as spheroids. Lesions were qualitatively similar at all levels, but quantitatively dissimilar in the same funiculi at different levels. Both ascending and descending fibers were involved but correlation to specific fasciculi was not evident. Lesions always were most severe in thoracic spinal cord segments. Little or no astroglial response, no inflammatory response, and no involvement of gray matter were observed in the spinal cord. Cerebellar lesions were limited to selective degeneration and loss of Purkinje cells and occasional swelling of Purkinje cell axons (torpedos) in the granular layer of the cerebellar cortex. Brainstem lesions were inconsistent and limited to occasional axonal swelling in brainstem nuclei. The pathogenesis of bovine progressive degenerative myeloencephalopathy is unknown and possible mechanisms were discussed. The disease exhibits a familial pattern in Brown Swiss cattle and may be hereditary. Extraneural lesions were considered secondary to central nervous system lesions.Bovine progressive degenerative myeloencephalopathy of purebred Brown Swiss cattle is a progressive disease with clinical signs that implicate central nervous system involvement. Epidemiology, clinical signs, and other clinical and laboratory findings have been detive myeloencephalopathy has an onset at five to eight months of age, affects both sexes, and is characterized clinically by hind leg weakness, ataxia, and dysmetria in the absence of other significant clinical abnormalities. A familial relationship has been suggested. The disease occurs throughout the United States and has been reported only in Brown Swiss cattle. The purpose of this study was to characterize the morphologic lesions and to examine the distribution and nature by light microscopy.scribed.-'8. 39. 57. 58 B nefly, .bovine progressive degeneraForty-three cattle were necropsied in this study, including 36 Brown Swiss cattle, 28 females and 8 males, affected with bovine progressive degenerative myeloencephalopathy. A fetus in the last trimester of gestation from an affected cow (number 16) was not affected. Additional control animals free of bovine progressive degenerative myeloencephalopathy included three other Brown Swiss affected with other conditions and two Jersey cows and one Brown Swiss calf which were all neurologically normal. Animal numbers, sex, age at death, manner of fixation, and final diagnoses ...

Abstract. Spina bifida was diagnosed in four English Bulldogs and one Collie dog. These cases and the examination of records from the Veterinary Medical Data Program suggested a high incidence of spina bifida in the English Bulldog. Urinary and fecal incontinence was the most common reason for initial examination for the five dogs. Radiographs and myelography confirmed the diagnosis of spina bifida. Blood, cerebrospinal fluid and urine analyses did not aid diagnosis but urocystitis was identified. In addition to spina bifida, clinical signs and morphologic changes in the spinal cords of all five dogs fulfilled the criteria for an additional diagnosis of spinal dysraphism. A common pathogenesis for the two conditions is suggested.