Lungworm In Bighorn Sheep

Author : Charles Cormack Gates
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (143 download)

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Download or read book Aspects of the Environment written by Charles Cormack Gates and published by . This book was released on 1975 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The occurrence of lungworms of the genus Protostrongylus in bighorn sheep (Ovis c. canadensis') has been known since the 1920's but the complex system which involves lungworms, bighorn sheep, and the environ ment remains poorly understood. The purpose of this study was to investigate the role of nutrition and other environmental factors in lungworm infections. Two neighbor ing bighorn sheep herds in the mountains of west-central Alberta were studied from September 1972 to May 1974. Seasonal variation in the rate of lungworm larvae shedding in the feces of two bighorn sheep herds was documented. Two distinct periods of shedding were apparent. These were approximately coincident with summer and winter, summer being a period of low larval shedding and winter a period of a higher rate of shedding. The possibility that this phenomenon could be the result of dilution or concentration of larvae in a seasonally variable fecal mass was discussed. Seasonal variation in the qualitative nutrition of the two sheep herds was evaluated using fecal nitrogen as an index for the estimation of forage crude protein, digestibility and gross energy content. Fecal protein (N X 6.25) proved to be a useful tool for the purposes of this study. Simulated energy positions of both sheep herds for both winter periods of the study were compared using a bioenergetics model construc ted with values from domestic and wild ruminant literature. The resulting observation was that although the energy position of both sheep herds declined from one winter to the next, lungworm burdens, as evaluated by larvae counts, fell significantly. The relevance of nutrition in the etiology of heavy lungworm infections was discussed. The observed decline in the intensity of lungworm infections followed a 30 percent decrease in rainfall from one preceding spring-summer season to the next, thus implicating ecological and/or environmental factors other than nutrition in the etiology of changing lungworm burdens. Prenatal infection of four near term bighorn sheep with first- and third-stage lungworm larvae was demonstrated. This finding suggested a more cosmopolitan occurrence of the phenomenon in bighorn sheep than was previously suspected.