Studies On Divergently Selective Effects For Plasma Very Low Density Lipoprotein Concentration In Broiler Chickens

The G₂,G₃and G₄ generation of birds from Arber Acres(AA) and divergentlyselected for plasma VLDL concentration were further studied on the divergentlyselective effects of plasma VLDL concentration on fatness,productive performanceand reproductive performance, the cross between sire line from AA divergentlyselected for plasma VLDL concentration dan line from Ayine never selected forplasma VLDL concentration were studied, too. The main results were as follows:1. Heritabilities of plasma VLDL concentration and fatness were moderate,the heritability estimate were 0. 2278 and 0. 2418～0. 40, respectively. Thephenotypic correlation between plasma VLDL and fatness were moderate (R_P=0. 21～0. 27), and the genetic correlation between them were high (R_A=0. 8427). wnichindicated that plasma VLDL concentration was a good genetic marker for selectingof fatness in meat-type birds.2. There was significant difference between plasma VLDL concentration of fatline and that of lean line in G₃. and significant difference between abdominal fatweight of them in G₃ and G₄, and percentage of abdominal fat in G₄. Which means thediyergently selecting for plasma VLDL concentration had made the fatness of fatline and lean line different from each other.3. There was significant difference between body weight of fat line and thatof lean line in G₃. Although the difference wns no longer significant in G₄, thetendency that the body weight of fat line is higher than that of lean line wasstill could be observed. And there was moderate positive phenotypic correlationand positive genetic correlation (R_P=0. 2425: R_A=0. 4645) between plasma VLDLconcentration and body weight, and relatively high positive phenotypic correlationand positive genetic correlation (R_P=0. 6553;R_A=0. 6156 ) between body weight andabdominal fat weight, and moderate positive phenotypic correlation and low geneticcorrelation (R_P=0. 4025;R_A=0. 0469) between body weight and percentage ofabdominal fat. which means the selecting for low plasma VLDL concentration woulddecline the body weight, and the selecting for low plasma VLDL concentration shouldbe accompanied with the selecting for high body weight.4. The 50-week and 40～50-week egg production of lean line were significantlyhigher than that of fat line in G₃. The phenotypic correlation between 40-week,50-week,40～50-week egg production and plasma VLDL concentration was-0. 224,--0. 28 and --0. 24, respective1y, the genetic correlation between them sas -0. 686l' -- 0. 4368 and -- 0. 2304, respectively. There was moderate phenotypiccorrelation and high genetic correlation between the p1asma VLDL concentrationand day--old egg production, the correlation coefficient was 0. 26 and 0. 7627,respective. The fertilization rate and hatchability of setting eggs of lean linewere significantly or very significantly higher than that of fat 1ine. There wasmoderate negative genetic correlation (R^= --0. 4564). The difference of egg weightand hatchability of ferti1e eggs between fat line and lean 1ine were notsignificant, but the phenotypic correlation between p1asma VLDL concentration andegg weight was very 1ow (RP=0. 024), and the tendency that the hatchability offerti1e eggs of 1ean line was higher than that of fat 1ine cou1d be observed. Al1of this demonstrated that the se1ecting for 1ow p1asma VLDL concentration did notdec1ine the reproductive performance, but made it incline, instead.5. The results of cross experiment showed, the fatness of offspring from fiveexperimental groups lined as fo1lows: Pat X Pat (FP) >Fat X Avine (PAV) > Avine XAvine (AVAV) >Lean XAvine (LAV) >LeanX Lean (LL), which indicated that the fatness offat and lean line from AA were hereditary steadily. The body weight of offspringfrom cross group higher than that of offspring from fat or lean 1 ine, which indicatedthat the cross remedy the genetic defect of fat or 1ean line in body weight.6. There wa...