BREED STRUCTURE AND POPULATION DYNAMICS OF THE CANADIAN YORKSHIRE PIG

Abstract

Over a period of 6 years terminating in 1966, 87,295 Canadian Yorkshire pigs were registered from 2281 herds. Approximately half of the herds and the animals recorded were from the provinces of Alberta and Ontario. Average life span of herds was short, 50.9% of the herds appearing for only one year of the 6-year period. Such herds contributed less than 10% to the total registrations. Herds in continuous production comprised 10.9% of all herds, produced 53.5% of total registrations and registered 30.4 pigs annually from an average herd size of 2.8 sires and 8.3 dams. These estimates of herd size were approximately four times larger than for herds registering pigs only once in the 6 years.During the period under study, the number of herds was reduced by more than 50% (from 1501 in 1960 to 737 in 1966), primarily by elimination of small herds. However, of all herds registering in 1966, 70% comprised five or fewer sows and 74% registered fewer than 20 pigs. The average generation interval was approximately 24 months. Record of Performance records were not employed to any meaningful degree for culling parental stock or for selecting progeny entered for registration.Pedigree analysis indicated a relatively minor degree of centralization, and there was little evidence of intra-herd breeding.