Genetic and Environmental Effects on Internal Parasites, Foot Soundness and Attrition in Crossbred Ewes

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Abstract
Approximately 400 ewes from eight crossbred groups (North Country Cheviot, Dorset, Finn or Romney sires ✕ Suffolk or Columbia-type dams), two birth years and two management environments were evaluated for differences in internal parasites, footrot scores and attrition rate. Fecal samples collected from 160 ewes six times over a 1-year period were evaluated for parasite eggs per gram of feces (EPG). Columbia crossbred ewes tended to have lower EPG than Suffolk crossbred ewes. Higher levels were suggested for both North Country Cheviot and Dorset sired ewes. Intraclass correlations of repeated EPG on the same ewe were near zero. For four of six sampling periods, ewes on irrigated pastures had higher EPG than ewes on nonirrigated hill pastures (P<.01). Footrot scores were recorded for all ewes on seven occasions from July 1975 to July 1977. No consistent footrot score differences were attributable to breed of the ewe's dam, breed of the ewe's sire or age of the ewe, but ewes on irrigated pasture generally had significantly higher incidence than ewes on hill pasture. Results indicated that breed selection could be based on adaptability and performance traits other than parasite and footrot resistance. Annual attrition rate averaged 4.9 and 4.6% for the two birth year groups. Illness caused 42% of total attrition; 5% was due to reproductive and lactational problems; 16% was the result of accidents; and 37% was due to unknown causes. Suffolk crosses had higher losses than Columbia crosses, a large part of which was due to founder in 1975. Finn crossbred ewes had relatively high attrition in both age groups, also partly attributable to founder in 1975; while Romney crossbreds were below average for rate of attrition. Copyright © 1979. American Society of Animal Science. Copyright 1979 by American Society of Animal Science.

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