ASSOCIATED EFFECTS OF DIVERGENT SELECTION FOR RESIDUAL FEED CONSUMPTION ON REPRODUCTION, SPERM CHARACTERISTICS, AND MITOCHONDRIA OF SPERMATOZOA

Eighteen generations of divergent selection for residual feed intake h ave been completed in two Rhode Island Red lines of domestic fowl. The high intake R(+) Line and the low intake R(-) line cocks used to sire Generation 19 of the selection experiment have been compared for asso ciated responses on fertility, hatching, and sperm quality. Evaluation s of sperm samples were based on volume, cell concentration, biochemic al parameters (pH, uric acid and protein concentrations), and motility and morphology of spermatozoa. Finally, individual spermatozoa were a nalyzed by flow-cytometry (FCM) using Rhodamine 123 (Rh123) and nonyl- acrydine-orange (NAG) specific fluorochromes to assess, respectively, overall mitochondrial activity and overall mitochondrial content. Hatc hability of incubated eggs was 20 points higher for the R(-) Line, mai nly because unfertilized eggs were only 6 vs 30% in the R(+) line. Ear ly embryo mortality was also twice as high in the R(+) Line (21%). The ratio of Rh123 to NAO fluorescence was identical for both Lines. This result suggests that there was no difference in the energy producing potential of the individual mitochondria. Therefore, the difference se en for both dyes between the two lines might be attributed to a differ ence in the quantity of mitochondrial inner membranes present in the c ell (with 17% less for the R(+) line). In the R(+) line, the poor perf ormance at fertilization and during early embryonic development was as sociated with lower production of motile spermatozoa, possibly in rela tion to a lower quantity of mitochondria in spermatozoa from R(+) cock s. Although the female contribution to the differences between lines w as not explored separately, results suggest that selection for residua l feed intake may have altered some cellular function related to the p roduction of energy in the R(+) line.