The aim of this study was to estimate the additive, heterosis, recombination loss, heritabilities and correlations between milk yield (MY), lactation length (LL), calving
interval (CI), age at first calving (AFC) and herd life (HL) for crossbred of Friesian
(F) and Jersey (J) with Boran (B). Analysis of fixed effects and crossbreeding parameter were undertaken using general linear procedure. Genetic parameters were estimated by multivariate analysis procedure with wombat software. Crossbred cows significantly outperform the B cows by 3 to 7 folds of MY per lactation. Even though performance of CI and AFC are slightly compromised, upgrading from 1/2F:1/2B (F1) to 3/4F:1/4B (F1) had better advantage as average MY improved by about 34% following this approach. The additive effects of F and J breed were 3985.2±150 and 1195.6±257 kg for MY, 166.3±16 and 18.5±27 days for LL, 52.9±25 and -40.3±44 days for CI, -0.23±2 and -9.8±4 months for AFC, and 548.7±431 and -569.9±784 days for HL, respectively. The estimated heterosis effects were 1054.8±145 and -150. 6±76 kg for MY, 62.4±15 and -7.3±8 days for LL, -58.1±24 and -88.7±13 days for CI, -1.9±3 and -4.7±1 months for AFC and -215.0±446 and -890.1±226 days for HL for J and F with B breed crosses, respectively. The loss due to recombination of F and B was significant (p < 0.005) and undesirable for MY, LL, AFC which reflect the need of appropriate breeding program. The heritability (h2) estimates were 0.30±0.00 for MY, 0.18±0.02 for LL, 0.09±0.03 for CI, 0.19±0.06 for AFC and 0.28±0.06 for HL. Strong genetic correlations were obtained between MY and LL (0.84±0.04), LL and CI (0.86±0.10) and LL and HL (0.94±0.07). The estimated genetic variance, heritabilities and correlations between traits and decline in performance of inter-se generations reveal the available potential of improvement through selection and the need of designing appropriate breeding program.
