PIG BREEDING: CURRENT PROGRAMS VS. FUTURE PRODUCTION REQUIREMENTS

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Abstract
Reports reported annually for the Canadian ROP swine testing program provide no evidence of genetic trends in the seed stock herds enrolled. Small herd size (< 8 sows), short average life span of these herds (< 5 yr) and the geographically diffuse nature of the seed stock industry appear to have been major impediments to the application of cohesive and sustained selection programs. The commercial industry, in contrast, has shown a marked improvement in average carcass merit during the past decade. This trend, stimulated and guided by the 1968 revision of carcass grading standards, has been accompanied by a 60% reduction in the number of commercial herds and a three-fold increase in the average number of pigs marketed annually per unit. The specific breeding programs employed by the commercial industry cannot be documented but there has been a steady growth in the use of systematic crossbreeding programs, and producer demand for boars with performance credentials has greatly intensified. This has fostered a fivefold increase in ROP testing activity since 1973, given impetus to the evolution of swine AI programs, and encouraged the development of large closed-herd seed stock operations with self-contained performance test facilities. The central objective of performance testing programs, both private and public, is the genetic improvement of traits directly relevant to efficient lean meat production. Future production requirements are unlikely to alter this basic objective but advances in the technology for live animal carcass evaluation and changing economic circumstances, specifically changes in rations to accommodate the increasing competition for cereal grain supplies, will necessitate continuous review and revision of testing procedures. Recent experimental evidence indicates that rate of feed ingestion is inversely related to efficiency of digestion and lean tissue feed conversion. This implies that testing programs which place a premium on rate of ingestion (e.g. "to appetite" or "scale" feeding) may be less suitable for purposes of measuring genetic differences in efficiency of lean production than programs which utilize ad libitum feeding.