Defining Breeding Objectives And Evaluating Two-tier Open Nucleus Breeding Scheme For Beef Line Of Luxi Cattle

Luxi cattle are one of the excellent region breeds in china. With the development of market requirement, selecting and breeding enter into new stage from beef and labor dual-purpose to special beef direction. In order to breed a beef line in Luxi cattle, breeding objective traits and selected traits were defined, and profit function was constructed in the near future by systematic analysis according to real breeding condition of Luxi cattle in the paper. Profit and economic values were derived from profit function by partial budgeting method, and Discounting genetic coefficients were calculated and economic values were standardized by genetic standard deviation to obtain economic weights and relative economic weights of objective traits for breeding and production system in beef line of Luxi cattle. Sensitivity of economic values to change in prices of pre kg live weight and beef, concentrates and forages was analyzed. With current nucleus breeding schemes for beef line of Luxi cattle, deterministic simulation was used to evaluate 8 selection programs for genetic gain and profitability. To the two-tire nucleus breeding schemes for beef line of Luxi cattle, ultrasound scanning and IGF-Ⅰconcentration was taken into consideration as early records of carcass traits in this study. 8 selection programs that differed in the records available for use as selection criteria were defined. Breeding results were compared of closed nucleus and open nucleus breeding system. At last factors effect on breeding results were analyzed.1. Breeding objective traits were grouped three kinds of traits that were growth, carcass and second trait,including nine economic traits which are weaning weights, yearling weights, mature cow weight, fatten daily gain, carcass grade, dressing percentage, age of first calving, calving interval and productive lifetime. And Profit function of six herd which contained nine objective traits, including calves, heifers, young bulls, cows, bulls and fatten flock were constructed in the two-tire open breed system on the fixed basis of cow herd. Profit of pre cow pre year was–1033.9 yuan, and economic value of nine objectives were 3.98yuan/kg, 2.30yuan/kg,–2.42 yuan/kg, 2.20yuan/g, 67.23 yuan/%, 363.95 yuan/class,–0.66 yuan/d, –3.10yuan/d and 25.49 yuan/year, And the ratio of relative economic weights of three kinds of traits was 0.62:0.26:0.12 after standardization, similar to 5:2:1. With the price changes, the economic value of weaning weight, yearling weight, mature cow weight, fatten daily gain, age of first calving and productive lifetime had worse change, dressing percentage had stable change and carcass grade and calving interval had significant change.2. Current scheme(scheme 5) will derive desired breeding efficiency in the five schemes, and its genetic gain pre year and profit was 85.65 yuan and 624.16 yuan respectively, moreover, average generation interval was 5.58 years for the five schemes and total level of selection accuracy for the selection groups was lower. Comparing close nucleus breeding system and open nucleus breeding system on the basis of the current scheme, genetic gain pre year, total outcome and profit and generation was increased by 0.80%, 9.39%, 10.64% and 0.90% respectively.3. If take the current scheme as comparison, then index accuracy, genetic gains per year and profitability were improved 30.11%, 15.21% and 22.05% for the ultrasound scanning scheme(scheme 6); 4.44%, 1.51% and 0.35%for the IGF-Ⅰscheme(scheme 7); 37.78%, 22.09% and 40.58%0.21 for the combine ultrasound scanning and IGF-Ⅰscheme(scheme 8). According to the results, the schemes taking the ultrasound scanning and IGF-Ⅰas selection criteria would derive more ideal breeding efficiency.4. Only enlarge population size and increase nucleus size, it will increase genetic gains and profit. Increase ratio of seed cow, it will slowly decrease genetic gains and profit after reaching climax. Enlarge number of test bulls, it will increase slowly genetic gains and profit. And widen open degree, it will increase genetic gains and profit after reaching climax.5. With the price of live weight, beef and feed changing in current scheme, the rest traits had stable changes except carcass grade's significant changesThe results show that economic value and economic weights that were derived from current price system should be adjusted with price changes. And growth traits should be mainly strengthened to select for beef purpose direction, and that should be give attention to reproduction and carcass traits simultaneity; genetic gain and profit are changing with records available changing in selection criteria, and it could derive better breeding efficiency from the fifth selection program. However, the current nucleus breeding scheme kept some room to be improved in effect; breeding efficiency of open nucleus breeding system super to closed breeding system on the basis of current scheme. It will derive desired breeding efficiency that Ultrasound scanning and IGF-Ⅰconcentration were taken as early records of carcass traits into consideration, at same time it emphasized on the importance to derive carcass traits information from performance test of young bull and their relatives. For the future, Strengthening selection of carcass quality will more desired profitability because carcass quality is very important economically and is most desired characteristic to be improved in the future market requirement. However, selecting young bulls on the basis of their growth ability during performance testing is a less desirable strategy both genetically and economically. Thus, there is a need to include information on field carcass records from relatives of bulls to avoid potential losses of genetically superior candidates early in the selection process. In the process of selecting and breeding beef line of Luxi cattle, It will derive desired breeding efficiency that Ultrasound scanning should be taken as selecting criterion and IGF-Ⅰconcentration were taken into consideration as early records of carcass traits.