Wang C T, Dickerson G E
Anim. Sci. Dept., Univ. of Nebraska, Lincoln 68583-0908.
J Anim Sci. 1991 Nov;69(11):4312-23. doi: 10.2527/1991.69114312x.
A deterministic mathematical computer model was developed to simulate effects on life-cycle efficiency of lamb and wool production from genetic improvement of performance traits under alternative management systems. Genetic input parameters can be varied for age at puberty, length of anestrus, fertility, precocity of fertility, number born, milk yield, mortality, growth rate, body fat, and wool growth. Management options include mating systems, lambing intervals, feeding levels, creep feeding, weaning age, marketing age or weight, and culling policy. Simulated growth of animals is linear from birth to inflection point, then slows asymptotically to specified mature empty BW and fat content when nutrition is not limiting. The ME intake requirement to maintain normal condition is calculated daily or weekly for maintenance, protein and fat deposition, wool growth, gestation, and lactation. Simulated feed intake is the minimum of availability, DM physical limit, or ME physiological limit. Tissue catabolism occurs when intake is below the requirement for essential functions. Mortality increases when BW is depressed. Equations developed for calculations of biological functions were validated with published and unpublished experimental data. Lifetime totals are accumulated for TDN, DM, and protein intake and for market lamb equivalent output values of empty body or carcass lean and wool from both lambs and ewes. These measures of efficiency for combinations of genetic, management, and marketing variables can provide the relative economic weighting of traits needed to derive optimal criteria for genetic selection among and within breeds under defined industry production systems.
开发了一个确定性数学计算机模型，以模拟在不同管理系统下，性能性状的遗传改良对羔羊和羊毛生产生命周期效率的影响。遗传输入参数可针对初情期年龄、乏情期长度、繁殖力、繁殖早熟性、产仔数、产奶量、死亡率、生长率、体脂和羊毛生长进行变化。管理选项包括配种系统、产羔间隔、饲养水平、补饲、断奶年龄、上市年龄或体重以及淘汰策略。动物的模拟生长从出生到拐点呈线性，然后在营养不限制时渐近减缓至指定的成熟空腹体重和脂肪含量。每天或每周计算维持正常状况所需的代谢能摄入量，用于维持、蛋白质和脂肪沉积、羊毛生长、妊娠和泌乳。模拟采食量为可利用量、干物质物理极限或代谢能生理极限中的最小值。当摄入量低于基本功能需求时会发生组织分解代谢。体重下降时死亡率增加。为计算生物学功能而开发的方程已通过已发表和未发表的实验数据进行验证。累积计算羔羊和母羊的总可消化养分（TDN）、干物质和蛋白质摄入量以及空体或胴体瘦肉和羊毛的市场羔羊等效产值的终生总量。这些遗传、管理和销售变量组合的效率衡量指标可以提供性状的相对经济权重，这些权重是在既定行业生产系统下，推导品种间和品种内遗传选择最佳标准所需的。
