Degree Type

Dissertation

Date of Award

1980

Degree Name

Doctor of Philosophy

Department

Animal Science

Abstract

Two hundred seven purebred Duroc pigs from twelve sires were used to evaluate the effects of sire soundness classification (sound and unsound), level of feeding (ad libitum and 80% restrictive) and sex of the pig (barrows, boars, and gilts) on leg soundness scores, severity of bone abnormalities and performance and carcass traits. Animals within each progeny group were fed either ad libitum or 80% of ad libitum during the growing phase (18 to 54 kg). All pigs were fed ad libitum from 54 to 100 kg. Each pen consisted of approximately equal numbers of each sex (boars, barrows and gilts). X-rays of the right forelimb and bone tissue samples were obtained for evaluation of osteochondrosis dissecans and lesions of the metaphysis of the distal ulna;The effects of sire soundness classification were not large for most traits. Level of feeding appeared to have no effect upon visual scores for leg soundness. Boars were found to be more unsound at 100 kg than either barrows or gilts. Problems in leg soundness became more apparent as the animals approached market weight at 100 kg;Osteochondrosis dissecans of the humeral condyles (OCD) and incomplete metaphyseal fractures of the distal ulna were the most common bone lesions observed. These bone lesions were related poorly to soundness scores. OCD was affected unfavorably by increased average daily gain, and favorably correlated with longer bodied, leaner market hogs;The heritability estimates of soundness scores were moderately high: front leg structure, .53 (+OR-) .28; front leg movement, .31 (+OR-) .23; rear leg structure, .20 (+OR-) .20; rear leg movement, .29 (+OR-) .14; total visual score, .30 (+OR-) .23. Selecting for longer pigs which are lower in backfat was found to be favorable to making improvement in soundness. Selection for large loin eye areas was antagonistic to soundness. The heritability estimate for osteochondrosis dissecans lesion score of the distal humerus was .38 (+OR-) .33.

DOI

https://doi.org/10.31274/rtd-180813-4616

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Ralph Dean Wilson

Language

en

Proquest ID

AAI8028645

File Format

application/pdf

File Size

134 pages

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