Matos C A, Thomas D L, Nash T G, Waldron D F, Stookey J M
Department of Animal Sciences, University of Illinois, Urbana 61801.
J Anim Sci. 1992 Jan;70(1):43-50. doi: 10.2527/1992.70143x.
The objectives of this study were to identify nongenetic factors influencing scrotal circumference size and growth and to estimate heritabilities of scrotal circumference size at different ages and scrotal circumference growth between ages. Data on scrotal circumference, live weight, and age were recorded over 6 yr (1982 to 1987) on 541 spring-born Rambouillet ram lambs (109 sires, 307 dams) at the Dixon Springs Agricultural Center. Scrotal circumference and live weight were predicted at four ages (90, 120, 150, and 180 d) for each lamb. The two models used to evaluate factors affecting scrotal circumference size at fixed ages were the same except for the addition of live weight and live weight squared to one of the models. Likewise, the two models used for scrotal circumference growth between ages were the same except for the addition of live weight change and live weight change squared to one of the models. Year and type of birth were significant sources of variation for both traits under both models. Regression coefficients for live weight and live weight squared on scrotal circumference size and for live weight change and live weight change squared on scrotal circumference growth and for day of birth within year for both traits were generally different from zero (P less than .05). Heritability estimates for scrotal circumference size at fixed ages ranged from .19 to .41. Adjustments for live weight led to an average 41.5% increase in heritability estimates. For scrotal circumference growth, heritabilities ranged from .17 to .60 and adjustments for live weight change resulted in an average 13% decrease in estimates.(ABSTRACT TRUNCATED AT 250 WORDS)
本研究的目的是确定影响阴囊周长大小和生长的非遗传因素，并估计不同年龄时阴囊周长大小的遗传力以及不同年龄间阴囊周长的生长遗传力。在迪克森斯普林斯农业中心，对541只春季出生的兰布耶公羊羔羊（109只父本，307只母本）在6年期间（1982年至1987年）记录了阴囊周长、活重和年龄数据。预测了每只羔羊在四个年龄（90、120、150和180日龄）时的阴囊周长和活重。用于评估固定年龄时影响阴囊周长大小因素的两个模型除了在其中一个模型中加入活重和活重平方外其余相同。同样，用于评估年龄间阴囊周长生长的两个模型除了在其中一个模型中加入活重变化和活重变化平方外其余相同。在两个模型下，年份和出生类型都是这两个性状变异的重要来源。活重和活重平方对阴囊周长大小的回归系数、活重变化和活重变化平方对阴囊周长生长的回归系数以及这两个性状在年内出生日的回归系数通常都不为零（P小于0.05）。固定年龄时阴囊周长大小的遗传力估计值范围为0.19至0.41。对活重进行调整后，遗传力估计值平均增加了41.
