Eisen E J, Croom W J, Helton S W
Dept. Anim. Sci., North Carolina State University, Raleigh 27695-7621.
J Anim Sci. 1988 Feb;66(2):361-71. doi: 10.2527/jas1988.662361x.
Male mice selected for rapid 3 to 6 wk postweaning gain (M16) and unselected controls (ICR) were ad libitum fed a stock diet containing 0, 50 or 200 ppm cimaterol, a beta-agonist, from 4 to 7 or 4 to 10 wk of age. Mortality rate was higher in M16 than in ICR mice fed cimaterol (12.5 vs 1.3%; P less than .01). No mortalities occurred in either line fed the control diet. Line M16 exceeded (P less than .01) ICR in growth rate, feed intake, feed efficiency and lean index. Line X cimaterol level interactions (P less than .01) were found for the first three of these traits, although cimaterol level did not change line ranking. Epididymal fat as a percentage of empty body weight decreased at a faster rate in M16 than in ICR as cimaterol level increased. At 0 and 50 ppm, M16 exceeded ICR (P less than .05), but at 200 ppm there was no line difference (P greater than .05). Line M16 exceeded (P less than .05) ICR in blood glucose (5%), nonesterified fatty acids (4%) and lactate at 7 wk (9%), but lactate was higher in ICR at 10 wk (13%). Lines were not different in blood urea-N. Compared to zero cimaterol level, at 50 and 220 ppm glucose decreased (14% and 23%; P less than .05), nonesterified fatty acids decreased (3% and 29%; P less than .05), lactate increased (9% and 11%; P less than .05) and blood urea-N increased (3% and 16%; P less than .05). There were no line X cimaterol level interactions for blood metabolites. Differences in mortality rate, growth, feed consumption, feed efficiency and epididymal fat pad percentage between the high-growth and control lines in response to cimaterol may reflect genetic differences in mechanisms of metabolic regulation.
选择断奶后3至6周体重快速增加的雄性小鼠（M16）以及未选择的对照小鼠（ICR），在4至7周龄或4至10周龄时随意喂食含有0、50或200 ppm西马特罗（一种β-激动剂）的基础日粮。在喂食西马特罗的情况下，M16小鼠的死亡率高于ICR小鼠（12.5%对1.3%；P<0.01）。喂食对照日粮的两个品系均未出现死亡情况。M16品系在生长速率、采食量、饲料效率和瘦肉率方面超过ICR品系（P<0.01）。对于前三个性状，发现品系X西马特罗水平存在交互作用（P<0.01），尽管西马特罗水平并未改变品系排名。随着西马特罗水平的增加，M16附睾脂肪占空体重的百分比下降速度比ICR更快。在0和50 ppm时，M16超过ICR（P<0.05），但在200 ppm时品系间无差异（P>0.05）。在7周龄时，M16品系的血糖（5%）、非酯化脂肪酸（4%）和乳酸（9%）超过ICR品系（P<0.05），但在10周龄时ICR品系的乳酸更高（13%）。两个品系的血尿素氮无差异。与西马特罗水平为零相比，在50和220 ppm时，血糖下降（14%和23%；P<0.05），非酯化脂肪酸下降（3%和29%；P<0.05），乳酸增加（9%和11%；P<0.05），血尿素氮增加（3%和16%；P<0.05）。血代谢物方面不存在品系X西马特罗水平的交互作用。高生长品系和对照品系在对西马特罗的反应中，死亡率、生长、饲料消耗、饲料效率和附睾脂肪垫百分比的差异可能反映了代谢调节机制的遗传差异。
