INBREEDING IN SWISS BRAUNVIEH AND ITS INFLUENCE ON BREEDING VALUES PREDICTED FROM A REPEATABILITY ANIMAL-MODEL

Inbreeding coefficients were computed for 910,444 animals of the Swiss Braunvieh population. Of the animals born in 1984, 71.5% were inbred with 67.9, 3.4, and .2% having inbreeding coefficients between > 0 and 5%, > 5 to 10%, and > 10%, respectively. The average inbreeding coeff icient was 1.14% but, for animals with both parents and at least one g randparent known, it was 1.67%. Breeding values for total milk, fat, a nd protein yields and for fat and protein percentages were predicted u sing a repeatability animal model including a regression on the inbree ding coefficient. Phenotypic performance was sizeably depressed for mi lk yield only (-26 kg/% of inbreeding or 2.4% of the phenotypic standa rd deviation). Adjusting for inbreeding increased the estimated geneti c trend slightly. Inbreeding is only partially accounted for when it i s ignored in the construction of the inverse of the numerator relation ship matrix. This effect was investigated by comparing predicted breed ing values from a model including the complete matrix with predicted b reeding values from a model including a matrix constructed with inbree ding ignored. Only .8% of all predicted breeding values were affected by more than +/- 5.5 kg. The maximum difference observed was 55.3 kg. The observed average absolute differences between the breeding values of offspring predicted with the two models increased with inbreeding o f parents.