Doctoral Dissertations

Date of Award

3-1984

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

J.B. McLaren

Committee Members

R.R. Shrode, C.C. Melton, E.R. Lidvall

Abstract

One hundred eighteen pigs, representing 12 litters, were used to study structural soundness and toe size uniformity. The pigs were sired by either a Hampshire or Duroc boar and the sows were Duroc x Yorkshire, Yorkshire x Duroc, or Landrace x Yorkshire X Duroc crosses. Pigs were cared for by normal and standard management and feeding practices. While in the farrowing house, the floor surface was partly concrete and partly one-half inch steel rods spaced three-eights of an inch apart. The grower-finishing unit had a total concrete floor. Pigs were visually appraised by an experienced evaluator at 1, 7, 14, 21, 60, and 223 days of age. Pigs were first scored for overall soundness and then scored for components of growth and composition, and components of skeletal shape. All scoring was on a 1-15 basis. At the same days of age, each pig was measured, in centimeters, for toe and pad size and the differences between lateral and medial toe measurements were calculated.

The evaluator's scores accounted for more variation among younger pigs and pigs at 223 days of age, while there was less variation in scores at the intermediate time of 6D days of age. The. skeletal shape components of foreleg side view, front pastern, and topline and the variable age accounted for 76% of the total variation in overall soundness score.

Pad width and pad depth were more highly associated to overall soundness score than any other foot measures. Calculated differences between lateral and medial toes and pads provided little explanation in the variation of overall soundness score, however, scores for pad width and pad depth did tend to explain the most variation in overall soundness score at all ages, especially at day 223 with R-squares of .26 and .37 respectively.

Growth of the pigs tended to follow the chronological schedule of management and environmental changes. This chronological schedule affected the total variation that the evaluator observed in the population. Litter effect explained 34% of the variation in overall soundness score at birth, however, when litter effect was removed the means of the subjective components remained the same. This would indicate that soundness score is the result of genetics, however, more likely it is influenced by both genetic and environmental components.

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