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pp.75-83
The objective of this study was to identify the effects of various environmental effects associated with performance testing results in pig population of domestic pig breeding farms. Performance test data collected from 2,000 to 2,010 were a total of 265,901 heads. By breeds, data consisted of Duroc, Landrace and Yorkshire. Environmental factors considered in models were breed, sex, farm, year of test, season of test, and parity. Broad range of age at testing day averaged at 155 days of age were grouped as A (up to 140 days) B (141~150 days), C (151~160 days), D (161~170 days), and E (greater than 170 days). Traits analyzed were ADG, days to 90 ㎏, end weight (body weight at the test day), rib eye area, back fat thickness. Age group effects were all significant for all the traits studied (p<0.05). As ages at test day get greater, ADG, days to 90 ㎏ and end weight tended to be greater while ultrasound measures of rib eye area and back fat thickness tended to be less. This would be the results of linear age adjustments on ultrasound measures, that caused overestimation in younger age groups and underestimation in older age groups than in average age group (C). This was evidenced by looking at ultrasound measures before linear age adjustments were applied. We conclude that, for more accurate performance testing, testing within guided age interval should be abided. And further researches should be made on biologically justifiable methods of age adjustments especially for ultrasound measures.
