BREED OF DAM, AGE OF DAM AND SEX OF CALF EFFECTS IN THE CANADIAN SIMMENTAL YOUNG SIRE PROVING PROGRAM

Abstract

Canadian Simmental Association Young Sire Proving Program records (1978–1982) were used to estimate breed of dam by age of dam by sex of calf effects for several traits. Two models were used. Model 1 included fixed herd-years, breed of dam by age of dam by sex of calf (BAX) plus random sire and residual effects. Model 2 included fixed herd-year by sex of calf and breed of dam by age of dam (BA) plus random sire and residual effects. Both models included additive genetic relationships among sires and maternal grandsires. Traits used with Model 1 were gestation length (GL), calving ease (CE), birth weight (BW), gain on dam (GD) and 200-day weight (WW). Model 2 was used for gain on test (GT) and 365-day weight (YW). Mixed model techniques were used to obtain best linear unbiased estimates of BAX and BA from models 1 and 2, respectively. Hypothesis tests were conducted using two breed of dam groups ([Formula: see text] Simmental (S) and [Formula: see text] British breeds (B)) and four age of dam groups (2, 3, 4 and 5 + yr which correspond to < 31, 31–42, 43–54 and > 54 mo, respectively). Three-way subclasses (BAX) were significant (P < 0.01) for GL, CE, BW, GD and WW as were two-way subclasses (BA) for YW. Estimated differences for breed of dam by age of dam by six of calf subclasses (for GL, CE, BW, GD, WW) and breed of dam by age of dam subclasses (for YW) generally increased as age of dam increased. Accounting for breed of dam, age of dam, sex of calf and interaction effects are important in sire evaluation. Estimated differences of these effects, a by-product of sire evaluation, can be used to increase the accuracy of procedures for individual and dam evaluation. Key words: Breed of dam by age of dam by sex of calf effects, sire evaluation, mixed model techniques