Johnson Z B, Chewning J J, Nugent R A
Department of Animal Sciences, University of Arkansas, Fayetteville 72701, USA.
J Anim Sci. 1999 Jul;77(7):1679-85. doi: 10.2527/1999.7771679x.
The purpose of this study was to estimate genetic parameters for ADG, backfat thickness and loin eye area (LEA), and measures of feed intake and efficiency for purebred Large White boars born from 1990 to 1997. Boars from 60% of the litters were culled at weaning based on a maternal breeding value (index) of the dam, and remaining boars (n = 26,706) were grown to 100 d of age. Selection of boars for individual pen testing was based on a combination of growth and maternal indices. Boars were fed a corn-soybean meal diet that was 1.14% lysine, 19% protein, and 3,344 kcal/kg ME for approximately 77 d. Boars were weighed at the beginning and end of the test, and feed intake was recorded. Daily feed intake (DFI), ADG, and feed:gain ratio (FG) were computed. Four measures of residual feed intake (RFI) were estimated as the difference between actual feed intake and that predicted from models that included 1) initial test age and weight and test ADG (RFI1); 2) initial test age and weight, test ADG, and backfat (RFI2); 3) initial test age and weight, test ADG, and LEA (RFI3); and 4) initial test age and weight, test ADG, backfat, and LEA (RFI4). Genetic parameters were estimated using an animal model and single- or multiple-trait DFREML procedures. Models included fixed effects of contemporary groups and initial test age as a covariate and random animal and litter effects. Heritability estimates for test ADG, DFI, FG, backfat, LEA, RFI1, RFI2, RFI3, and RFI4 were .24, .23, .16, .36, .24, .17, .11, .15, and .10, respectively. Genetic correlations between ADG and backfat, ADG and LEA, ADG and DFI, and ADG and FG were .37, .36, .82, and -.32, respectively. Genetic correlations between ADG and measures of residual feed intake ranged from .11 to .18. Genetic correlations of backfat with LEA, DFI, and FG were -.27, .64, and .40, respectively. Genetic correlations of backfat with RFI measures were higher when backfat was not included in the estimation of RFI. Genetic correlations for LEA with DFI and FG were 0 and -.52, respectively. Genetic correlations for LEA with RFI measures were all negative and ranged from -.31 to -.51. Genetic correlations indicate that selection for reduced RFI could be made without adversely affecting ADG. Backfat should also decrease, and LEA should increase. The amount of change in backfat or LEA would depend on the measure of RFI used.
本研究旨在估计1990年至1997年出生的纯种大白公猪的平均日增重（ADG）、背膘厚度和眼肌面积（LEA）的遗传参数，以及采食量和效率指标。根据母猪的母本育种值（指数），60%窝的公猪在断奶时被淘汰，其余公猪（n = 26,706）饲养至100日龄。个体围栏测试公猪的选择基于生长和母本指数的组合。公猪饲喂含1.14%赖氨酸、19%蛋白质和3344千卡/千克代谢能的玉米-豆粕日粮约77天。在测试开始和结束时对公猪称重，并记录采食量。计算日采食量（DFI）、ADG和料重比（FG）。估计了四种剩余采食量（RFI）指标，即实际采食量与根据包含以下因素的模型预测的采食量之间的差异：1）初始测试年龄和体重以及测试ADG（RFI1）；2）初始测试年龄和体重、测试ADG和背膘（RFI2）；3）初始测试年龄和体重、测试ADG和LEA（RFI）；4）初始测试年龄和体重、测试ADG、背膘和LEA（RFI4）。使用动物模型和单性状或多性状DFREML程序估计遗传参数。模型包括当代组的固定效应和作为协变量的初始测试年龄以及随机动物和窝效应。测试ADG、DFI、FG、背膘、LEA、RFI1、RFI2、RFI3和RFI4的遗传力估计值分别为0.２４、0.２３、0.１６、0.３６、0.２４、0.１７、0.１１、0.１５和0.１０。ADG与背膘、ADG与LEA、ADG与DFI以及ADG与FG之间的遗传相关性分别为0.３７、0.３６、0.８２和 - 0.３２。ADG与剩余采食量指标之间的遗传相关性在0.１１至0.１８之间。背膘与LEA、DFI和FG之间的遗传相关性分别为 - 0.２７、0.６４和0.４０。当RFI估计中不包括背膘时，背膘与RFI指标的遗传相关性更高。LEA与DFI和FG之间的遗传相关性分别为0和 - 0.５２。LEA与RFI指标的遗传相关性均为负，范围在 - 0.３１至 - 0.５１之间。遗传相关性表明，选择降低RFI不会对ADG产生不利影响。背膘也应减少，LEA应增加。背膘或LEA的变化量将取决于所使用的RFI指标。
