Data from the Caracu herd of Sertãozinho Experimental Station, selected for post weaning weight between 1979 and 2002, was analyzed to describe effective size, generation coefficient, generation interval, selection differentials and genetic gain in this population. Genetic gain was estimated by the product of the average weighted standardized differential (kg) and heritability divided by the average generation interval. Averages of sire and dam weighted selection differentials for post weaning weights were 1.10 and 0.28 standard deviations units (s.d.u). Sire and dam cumulative selection differentials measured in the progenies born in 2001 were 3.61 and 2.32 s.d.u, respectively. The ratio between averages of unweighted and maximum sire selection differentials was 0.89 indicating a efficiency loss of 11% mainly due to avoiding selection of related animals in the same year. Estimates of generation interval for the periods 1979 - 1984, 1985 - 1990, 1991 - 1996 and 1997 - 2002, were 6.3, 6.3, 5.5 and 4.8 years, respectively. In the same order, population effective size was 9, 12, 20 and 64 for these periods.The generation coefficient for the progeny born in 2002 was 4.5 generations. Average annual inbreeding of the population was 0.50% and 1.83% for inbred animals. The annual estimated genetic gain by selection for yearling weight was 2.02 kg/year. The introduction of genetic material from other herds, the restriction to avoid mating of related animals and the selection of a maximum of two progeny/sire/year were effective to avoid larger increase of inbreeding.
effective size; generation interval; inbreeding coefficient; generation coefficient; post weaning weight; selection
