Racial and heterosis effects of prolificacy traits on complete diallelic crossings between four rabbit breeds

Resumen

Four thousand twenty-five observations of three complete diallelic crossings between four rabbit breeds (California, C; Chinchilla, CH; New Zealand, N and Semi-giant, S) were conducted to determine the racial and heterosis effects on prolificacy traits. In the first study, a generalized linear model through the GENMOD procedure of SAS (2007), was applied which considered the race effects (paternal, maternal and their interaction), parity and generation. In the second, a mixed model through the PROC MIXED procedure, also of SAS, was used, which considered the genotype (cross vs. pure) as random and parity and generation as fixed. The BLUPs resulting from the second model were used when calculating heterosis. The indictors total born (TB), born alive (BA) and number of weaned animals (NW) were analyzed.
The maternal breed was the only important effect for the TB and BA. Chinchilla breed highlighted with more than seven kids for both measurements. Non-significant positive heterosis was found in the reciprocal crossings CCH-CHC for each trait under study, as in the CN-NC for the NW. Heterosis was negative or null in the other combinations. The use of C as maternal breed is a way to improve the traits TB and
BA. Advantages at the heterosis level are obtained with the CH-CHC crossing for all the prolificacy traits studied and with that of CS-SC for the WN. These results show that crossing is an alternative to increase productivity in different rabbit exploitations.
Key words: diallelic cross, rabbit, prolificacy, heterosis