BREED EFFECTS ON COMPONENTS OF BEEF PRODUCTION EFFICIENCY IN CROSSBREDS: COW AND CALF PREWEANING TRAITS (GROWTH, SURVIVAL, CALVING)

Effects of seven breeds of cow\u27s sire and 12 breeds of cow\u27s maternal grandsire on components of performance and on estimated efficiency of beef production were examined, using data for 3 - breed - cross cows and their calves from two experiments conducted at the Roman L. Hruska Meat Animal Research Center. Experiments 1 and 2 respectively, included 1043 and 680 records over four parities for cows from four and three breeds of cow\u27s sire and from six and six breeds of cow\u27s maternal grandsire. The statistical model fitted effects of calf sex, cow-calf year, parity, the breed effects and their interactions. Variation in breed effects on each trait were expressed as deviations from the mean of Hereford+Angus, multiplying deviations for breed of cow\u27s maternal grandsire by one half of the inverse of the reciprocal of genetic expectations (2), to make them directly comparable to those of cow\u27s sire. Estimated crossbred deviations ranged from -1.6 to 5.5 kg (P \u3c .001) for calf birth weights, -17.7 to 11.0% (P \u3c .001) for calving difficulty, -19.2 to 17.0% (P \u3c .10) for preweaning calf mortality, -1.5 to 27.1 kg (P \u3c .001) for calf weaning weight. For cow traits, deviations ranged from -23.4 to 13.3% for calves weaned per cow exposed to breeding, (P \u3c .05), -39.3 to 42.3 kg for calf weight weaned per cow exposed (P \u3c .01), -7.4 to 77.6 kg for cow weight (P \u3c .001) and -1.3 to 0.14 units for body condition score (P \u3c .001). After regressing breed deviations to their expected real genetic level for estimated ratio of income to feed costs ($) per cow year ranged from -28.2 to -.20% of mean for Hereford+Angus. The deviations ranged from -5.2 to 19.0% of Hereford+Angus for total weight of weaned calves sold, -32.0 to 31.6% for weight of cull cows sold, -1.8 to 15.7% for total income but from 2.0 to 44% for total feed costs