DEVELOPMENT OF AN ANIMAL-MODEL FOR ACROSS-HERD GENETIC EVALUATION OF NUMBER BORN ALIVE IN SWINE

An animal model and computer software were developed to conduct across -herd genetic evaluations using data from producers participating in t he Sow Productivity Index program of the American Yorkshire Club. The final data set consisted of 61,596 litter records from 1986 to early 1 990. The animal model included fixed contemporary group effects and ra ndom additive direct, service sire, permanent environmental, and resid ual effects. Additive genetic relationships among animals were include d. A separate relationship matrix for service sires and their sires wa s also included. A data set similar to the Yorkshire field data was si mulated to use in testing the animal model. The simulated data set con sisted of 40 herds, each with 120 reproducing dams and either four or five sires. Six generations of simulated data were produced, resulting in 20,605 litter records. These records were then evaluated using the animal model for number of pigs born alive. Finally, correlations bet ween the true breeding values from the simulation and the predicted br eeding values were computed. The correlation between the 918 true and predicted sire breeding values was considerably lower for the animal m odel without a service sire effect than when it was included (.53 vs . 74, respectively). However, the difference was cut in half (.66 vs .77 ) when only sires with greater than five daughter records were include d. The high accuracy of the animal model with a random service sire ef fect indicates that the proposed model adequately accounts for the var iation found in records for number of pigs born alive.