Levels and effects of inbreeding on growth and reproductive traits in Tropicarne and Brown Swiss cattle

With the objectives of determining levels and trends and to quantify the effects of inbreeding on offspring and mother on reproductive and growth traits in Tropicarne (TR) and European Swiss (SE) cattle breeds, the pedigrees of 5730 TC animals born between 1960 and 2003, and 10 471 SE animals born between 1962 and 2002 were analyzed. Inbreeding coefficients of the cattle were obtained using the ENDOG software. Variables studied in TR (1976 to 2003) were calving interval (IEP); age at first calving; and weights at birth (PN), weaning (PD), one year (PA), and IS months. In SE the variables (1993 to 2003) were PN, PD and PA. The statistical models included the fixed effects of herd, sex, year-season of birth, important first-order interactions (p <= 0.05), among them, inbreeding covariables of calf and mother, and age of the cow at calving, and in TR direct breed and maternal genetic effects, individual and maternal heterosis; and the random effect of the father of the animal for traits of growth and EPP, and of the animal for IEP. Means and standard deviations of inbreeding in TR and SE were 1.8 +/- 3.5 and 1.5 +/- 4.0% for all of the animals and 3.6 +/- 4.5 and 3.1 +/- 5.0% considering only those that were related. Annual increases in inbreeding for the entire population were 0.12 +/- 0.01% (p <= 0.01) in TR and 0.06 +/- 0.00% (p <= 0.01) in SE. No significant effects of inbreeding on the offspring (p > 0.21) or on the mother (p > 0.54) were found for the characteristics studied in either breed. The effect of some parameters based on probability of origin of the genes in the subestimation of inbreeding is discussed. It is concluded that the current inbreeding in these populations is low; however, mating should be planned so as to reduce increases in inbreeding.