Effect Of Caponization On Production Performance And MRNA Expression Of Related Genes On Roosters

To study the effects of caponization on body measurement, growth performance,carcass composition, meat quality, blood parameters and the expression mRNA of relatedGenes in guang xi Three-yellow chickens. Male chicks with similar body weight werecaponized or sham-operated at4wk of age and slaughtered at20wk. The results showed:1. Caponization resulted in reduced the size and weight of comb and wattle (P<0.01)and increased the length of fossil bone, calcar and chest depth (P<0.05) but decreased thelength of pelvis width. There were no significant differences in body slope length, breastwidth, shank length and shank circumference (P>0.05).2. The live body weight, carcass weight, half-eviscerated weight, eviscerated weight,breast muscle weight, abdominal fat weight and gizzard weight in capons were higher thanthose in the control (P<0.05or P<0.01). while the heart weight and the percentage of heartweight were significantly higher in the control chickens (P<0.01).the percentage ofdressing, half-eviscerated, eviscerated, leg muscle,liver and gizzard weight were notaffected by the caponization (P>0.05).3. Capon exhibited lower (P<0.01) values of breast and thigh meat redness and higher(P=0.01) values of thigh meat Yellowness compared with sham-operated chickens.Caponization had no effect on pH, drip loss and shear values (P>0.05).4. The length of fossil bone was found to be positively correlated with breast muscleweigh and the percentage of breast muscle weigh in two groups(r=0.629,0.624,0.648,0.582).The breast and thigh muscle weigh were found to be positively correlated with carcassweight, half-eviscerated weight and eviscerated weight in two groups.5. Caponization significantly increased (P<0.05or P<0.01) the blood HDL, LDL, TC,LH and E2concentration and decreased (P<0.01) the T concentration. There were nosignificant differences in concentration of TG and FSH between the groups (P>0.05).6. There was a positively correlated between TC concentration and HDL,LDLconcentration. TC concentration was found to be negative correlation with the abdominalfat weight and the percentage of abdominal fat weight in capons. There was a positivelycorrelated with the HDL concentration the abdominal fat weight and the percentage ofabdominal fat weight in sham-operated chickens.7. In abdominal fat tissue of capons, levels of mRNA encoding PPARγ and LPL were1.7and1.68fold compared with sham-operated chickens (P<0.05or P<0.01).Caponizationincreased3.62fold of liver FAS mRNA (P<0.05).Levels of hypothalamus GnRHⅠ,NPYand POMC mRNAs, however, were similar in castrated and sham-operated chickens(P>0.05). In castrated chickens levels of pituitary LHβ and FST mRNA were1.72and1.83fold (P<0.05) compared with sham-operated chickens. However, sham-operated chickensexhibited a significantly higher levels of FSHβ and ActivinβBmRNA (P<0.05) and were1.78and1.46fold compared with capons.Overall, this study indicated that the guang xi Three-yellow chickens caponized at4wk of age and reared until at20wk significantly improved growth performance andcarcass traits, one of the most important is significantly increased the breast muscle weight and abdomen fat weight.After castration, the breast muscle weight increased waspositively correlated with increased the length of fossil bone. and the abdomen fat weightincreased was related to up-regulation mRNA levels of FAS in liver and PPARγ, LPLmRNA levels in abdomen fat tissue. The decreased mRNA concentration of FSHβ wasrelated to up-regulated mRNA levels of FST and down-regulated mRNA levels ofActivinβB.