Genetic structure of the Brazil Large White swine herd

Abstract

The breed structure of the pedigree Large White in Brazil, was analysed from records of the Brazilian Pig Book, and by the pedigree sampling method. I. The number of herds for the 1971 to 1978 period was 365, changing from three in the first year to 110 in the last year. The total number of records was 89.390 for the eight years. During the period, the average existence of the herds in the pig book was 2.81 years and the herd average size was 3.2 boars and 22.3 sows. II. The most important herds, according to their genetic contribution for the breed were: the group of imported progenitors, plus the herds Santa Tereza (RS), São Domingos (RS), Petri (SC), Anne (RS), Rosada (SC), Montagner (PR), Sipal (SC) and Boavistense (RS). III, The imported boar PBB 49 presented the largest direct relationship to the breed (5.89%), followed by the boars PBB 61 (4%) and PBB 688 (3.37%). No one sow presented a breed relationship superior to 3%. IV. The total inbreeding up to 1978 was 1.20%, corresponding to an increasing of 0.30% per generation. The in strains breed subdivision index was 3.79, meaning the starting of a national strain formation. V. The average generation length was 24.9 months and the average age of the males and females, when the progeny was born, corresponded to 24.1 and 25.5 months, respectively. VI. The average replacement rate of boars from the own herd, considering all the farms, was 222%. The 84.7% of the farms were classified as Elite and the 15.3% as Multiplier, from a total of 72 farms in the sample.