THE INFLUENCE OF PERFORMANCE TEST DURATION AND SELECTION INTENSITY IN SWINE EVALUATION PROGRAMS
The problem of optimizing the use of limited test station facilities was considered in terms of varying performance test duration and intensity of selection using part-record genetic parameters for feed conversion ratio (FCR) and average daily gain (ADG). Average backfat (ABF) was limited to the market weight period. Full test duration, based on 396 Lacombe barrows and gilts was 88.5 days with FCR of 2.96, ADG of 0.84 kg/day, and ABF of 19.4 mm at a market weight of 93 kg. Proportions saved (p) of tested animals based on the whole record were 0.10, 0.25 and 0.50. As test station capacity was increased by reducing test duration, p was decreased such that a constant number of animals would be retained within each level of selection intensity. Optimum test period for FCR, ADG and index selection all coincided with the same test period. However, as p increased from 0.10 to 0.50, the optimum on test weight increased from 52 kg to 65 kg with a similar corresponding increase in on-test age from 98 days to 112 days. The test terminated at market weight. Gains in efficiency were 12%, 23% and 50% for index selection when the test period began at 52 kg, for p of 0.10, 0.25 and 0.50, respectively. Since very efficient animals would be near market weight by the on-test age of 98 days, test periods defined in terms of constant weight, rather than constant age, were deemed most suitable. Other limitations to the model and use of part-record selection procedures were discussed. Key words: Swine, part records, performance evaluation, station testing