| A total of400Rex Rabbit of America from Quanzhou breeding co., LTD. in Shanxi Province were to determine its growth pattern and evaluate its breeding characteristics. They were weighted at28,35,42,49,56,63,70,84,98,112,126,140,154and168days old. Elected eight healthy Rex rabbits(4males and4females) with similar body weight were slaughtered and used for analysis of slaughter, digest functions, muscle and pelt quality. All data were fitted using Gompertz and logistic function. The result showed that:1.The growth of Rex Rabbit fitted with both Gompertz and logistic functions, with Gompertz had higher fitting degree (R2>0.98).①The body size was highly correlated with weight (R2>0.95), and the formulas were as follow:y=217.75x-176.22for male and y=329.81e0.1706x for female within6months of age.(unit:body weight of y is g; body size of x is cm)。②The development was difference between male and female; male and female reached to the days of inflexion at87.64and110.88d, and with the body weight of1496.77g and2022.51g, respectively. The maximal weight was2993.54g of male and4045.02g of female, respectively. The rapid growth stage was between7.73-127.55d for male and60.22-161.53d for female.③Both Gompertz and Logistic functions could fit the development of skeleton, adipose tissue, muscle and pelt., the Gompertz model had a better fitting degree for muscle, skeleton and pelt; Logistic model fitted better for adipose tissue.④Both Logistic and Gompertz functions could be used for internal organ development estimation. Lung, liver, stomach and small intestinal had better fitness using Gompertz model, and heart, kidney, large intestinal and spleen had better fitness using Logistic model. The internal organs weight were as follows:heart:1.09-5.99g, lung:1.47-10.22g, stomach:5.12-20.01g, liver:9.71-75.84g, spleen:0.31-1.77g, small intestinal:9.52-42.15g, large intestinal:9.08-45.20g and kidney:2.94-14.77g.2.The nutrient deposition of body was not fully developed at140d.①The contents and deposition of protein and fat were increased with the body weight, and the concentration was different among tissues., The protein and fat concentration were sable in internal organ, with fat at3%-4%and protein at11%to13%,belong to early-maturing (b2<1); The protein concentration of carcass skeleton remained unchanged but the fat contents were increased, The protein is belong to early-maturing and fat isn’t. Both protein and fat contents of carcass muscle were increased with age. The protein was increased but fat content was decreased in pelt. The protein and fat in both carcass and pelt were later developed (b2>1).②Except for fat of carcass muscle, fitting equation of deposition on protein and fat in other tissues could be expressed as quadratic function. As for the intramuscular fat deposition, the allometric growth model was better than quadratic function. The total fat and protein depositions of carcass showed a polynomial manner, and the quadratic function showed a good fitness.3.Development of each part, internal organs and tissue showed successional manner.①Limbs and internal organs of digestion were developed firstly, followed by brain, carcass and pelt.②The internal organs maturity sequences were as follows:digest system, urinary system, cardiac system and immune system. The b values of allometry on different organs were as follows:Jejunum:0.4722, duodenum:0.4746, cecum:0.4753, ileum:0.5048, stomach:0.5556, colon:0.6129, rectum:0.6942, kidney:0.6945, heart:0.7299, lung:0.7817, spleen:0.8172, liver:0.8464, popliteal lymph nodes:1.0747, procussus vermiformis:1.4259, thymus:1.5691, sacculus rotundus:1.6415.③Except for immune system, all internal organs index decreased with increase of age. The proportions of the internal organs of the empty weight were as follows:heart:0.40-0.25, lung:0.80-0.47, stomach:1.00-2.00, liver:3.15-4.78, spleen:0.05-0.12, small intestine:2.50-4.50, big intestine:3.50-4.50, kidney:1.12-0.55.④The development order of tissue is:Skeleton, adipose tissue, muscle and pelt. the adipose tissue began to deposit at70days, and the inflection was at100days; the inflection of pelt was at126-140d.4. The age significantly affected the small intestine histomorphology (P<0.05) and had no effect on pepsin, trypsin, and amylase.(P>0.05)。In addition, age significantly affected IWT (P<0.01),VH of front and middle part on duodenum, Jejunum and ileum (P<0.05) and CD of front and middle part on duodenum, Jejunum (P<0.05); IWT, VH and CD were increased with age.The increased age was associated with increased pepsin, trypsin, and amylase activity, which reached to stable at60days.The activity of trypsin and amylase were different on different segment at same age, with jejunum had highest value, followed by ileum and duodenum had lowest value.5.The muscle pH was correlated with age, and pHBF was higher than pHBF. Cooking loss (CL), drip loss(DL)and Muscle shear force (X) were significantly affected by age, with CL and DL decreased with age, and the X value showed high-low-high trend.The ultimate pH of maturity muscle was4.0-4and the values of CL, DL and X were38.5%-39.8%,2.0%-2.4%,1.83-3.24kg/cm2, respectively. 6.Gompertz and Logistic functions could fit the change of its quality of pelt with age.The degree of fitting used the Gompertz function was better on the area of fresh pelt and dermatome’s thickness, and inflection were65.62and70.20d, respectively. The intensity’s fitness was better when used the logistic model, and the inflection was146.13d. The dermatome’s thickness of pelt was about0.59mm and the maximal S value was4396-4902cm2. T was increased significantly (P<0.01) and E1was decreased (P<0.01) with age, E2did not change with age (P>0.05)Conclusions:The development of America Rex Rabbit was fitted with both Gompertz and Logistic functions. The deposition of nutrition was exhibited quadratic model, and reached to stable at140days. The internal organs continued growth, and reached to maximal at140days. The maturity of muscle and pelt were98days and140days, respectively. Taken together, the harvest of Rex Rabbit should no early than140days. |
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