Evaluation of Egyptian sheep production systems: II. Breeding objectives for purebred and composite breeds

Objectives for this study were to estimate relative economic weights for pe rformance traits for two native and two composite sheep breeds under two ma nagement systems in Egypt. Breeds studied were Rahmani (R), Ossimi (O), 3/4 R-1/4Finnish Landrace (RFR), and 3/4O-1/4Finn (OFO); OFO and RFR were compo site breeds. Management systems were one mating season per year (1M) and th ree mating seasons per 2 yr 13M). A dynamic computer model was used to simu late animal performance and enterprise efficiency and profit. Input paramet ers for the model were obtained from published results and analyses of data collected from experimental flocks of the same genetic stocks in Egypt. Re sponses for two measures of life-cycle feed conversion and one measure of e nterprise profit were evaluated. Life-cycle feed conversion was calculated as kilograms of TDN input per kilogram of empty body weight output (TDN/EBW ) and kilograms of TDN input per kilogram of carcass lean output (TDN/CLN). Profit was measured as annual gross margin/ewe (GM/EWE). Traits evaluated were conception rate (CR), lambing rate (LR), mortality rate (MR), mature w eight (MW), and milk production (MK). Based on responses to percentage chan ges in trait means, CR was most important for TDN/EBW, followed by LR and M R. For TDN/CLN, LR, MR, and CR were most important;. For GM/EWE, CR was mos t important, followed by LR, MW, and MR. In the systems studied, there was little response to changes in MK. Based on changes in GM/EWE per genetic st andard deviation change, LR was most important, followed by CR, MR, MW, and MK in all systems. Relative economic weights for O and OFO were similar, a s were weights for R and RFR. Differences in economic weights between manag ement systems for the same breed were not large enough to justify separate selection lines within breeds.