Van Vleck L D, Gregory K E
Roman L. Hruska U.S. Meat Animal Research Center, USDA-ARS, Lincoln, NE 68583-0908, USA.
J Anim Sci. 1996 Jun;74(6):1234-9.
Estimates of variances due to additive and dominance genetic effects and permanent and temporary environmental effects were obtained for ovulation and twinning rates from a composite population selected for twinning rate. Measures of ovulation rate after 11 mo of age on 2,317 heifers with a total of 19,209 measures were used. Twinning measures were on 1,522 first-parity cows, 1,311 later-parity cows with a total of 3,571 measures, and 1,704 all-parity cows with 5,100 measures. Models included fixed effects of year-season-age at calving for twinning, and year-season of birth, age in months, and calendar month of measurement for ovulation rate. Four analyses were performed for each sample: combinations of models with and without dominance effects and with and without covariates for fractions of inheritance from the seven foundation groups. Variance components as fractions of phenotypic variance for analysis of all ovulation rate measures were .076, .000, and .045 for additive, dominance, and permanent environmental effects with no foundation groups in the model and .069, .000, and .050 with foundation groups in the model. For sums of eight measures, the estimates were .287 and .000 for relative variances of additive and dominance effects with groups in the model and .316 and .000 with groups ignored. For twinning rate for first parity, estimates were .126 and .209 for relative variances of additive and dominance effects; for later parities, estimates were .045 and .035 for models including foundation group effects. The results suggest lack of dominance effects in expression of ovulation rate and the possibility of dominance effects for embryo and(or) fetal survival or conception rate because twinning rate is a function of ovulation, conception, and embryo and(or) fetal survival rates.
从一个为双胎率选择的复合群体中，获得了由于加性和显性遗传效应以及永久和暂时环境效应导致的排卵率和双胎率方差估计值。使用了对2317头11月龄后母牛的排卵率测量值，共计19209个测量值。双胎测量值来自1522头初产母牛、1311头经产母牛，共计3571个测量值，以及1704头所有胎次母牛的5100个测量值。模型包括产犊时年份-季节-年龄对双胎的固定效应，以及出生年份-季节、月龄和测量的日历月份对排卵率的固定效应。对每个样本进行了四项分析：有和没有显性效应以及有和没有来自七个基础群体的遗传比例协变量的模型组合。在模型中没有基础群体时，所有排卵率测量值分析的方差成分占表型方差的比例，加性、显性和永久环境效应分别为0.076、0.000和0.045；模型中有基础群体时分别为0.069、0.000和0.050。对于八项测量值的总和，模型中有群体时加性和显性效应的相对方差估计值分别为0.287和0.000，忽略群体时分别为0.316和0.000。对于初产双胎率，加性和显性效应的相对方差估计值分别为0.126和0.209；对于经产，包括基础群体效应的模型中估计值分别为0.045和0.035。结果表明排卵率表达中缺乏显性效应，并且由于双胎率是排卵、受孕以及胚胎和（或）胎儿存活率的函数，胚胎和（或）胎儿存活率或受孕率可能存在显性效应。
