Cleale R M, Ingling J M, Search D J, Hadcock J R, Pausch M H
Fort Dodge Animal Health, Cyanamid Agricultural Research Center, Princeton, NJ 08543-0400, USA.
J Anim Sci. 1998 Jul;76(7):1849-58. doi: 10.2527/1998.7671849x.
We studied the effects of alpha2-adrenoceptor antagonists (A2AA) on nitrogen (N) partitioning. The diets fed contained 19.8% CP and 1.15% lysine. Pigs were fed the diet as a percentage of BW equaling approximately 90% of voluntary intake. In Trial 1, pigs (n = 11/treatment) were fed a basal diet and injected s.c. at 8-h intervals for 11 d with saline, RX821002 (25 mg/injection), or cimaterol (.6 mg/injection). Compared to saline-treated pigs, urinary N, as a percentage of N eaten, decreased among pigs injected with RX821002 (15%, P < .05) or cimaterol (17%, P < .05). In Trial 2, pigs got saline (n = 6) or 25 mg RX821002 (n = 6) as s.c. injections three times daily, or they were fed a diet containing 150 ppm RX821002 and injected thrice daily with saline (n = 6) for 11 d. The RX821002 lowered apparent DM and N digestibility (P < .05). Compared to controls, RX821002 lowered urinary N, as a percentage of N eaten, 15 and 18% when given by injections or per os, respectively, but effects were not significant. Trial 3 evaluated the effects of RX821002 fed at levels of 0 (n = 6), 37.5 (n = 5), 75 (n = 6), or 150 ppm (n = 6). Contrasts showed linear dose-dependent decreases in gain and apparent N digestibility (P < .05). Compared to untreated controls, urinary N, expressed as a percentage of N consumed, decreased 2, 12, and 10% among pigs fed diets with 37.5, 75, or 150 ppm RX821002, respectively, but effects were not significant. Trial 4 compared N balance in pigs (n = 6/treatment) fed basal diet or diet with 100 ppm RX821002 to that of pigs fed diets with 25 or 100 ppm yohimbine. Treatments reduced apparent N and DM digestibility (P < .05). Urinary N, as a percentage of N consumed, decreased 16 (P > .05), 18 (P < .05), and 24% (P < .05) for 100 ppm RX821002, 25 ppm yohimbine, or 100 ppm yohimbine, respectively. Data from Trials 2, 3, and 4 from control pigs (n = 18) or pigs fed A2AA (all A2AA sources and doses; n = 41) were pooled and analyzed. Feeding A2AA decreased apparent N and DM digestibility (P < .01). The fact that fecal moisture content was higher in pigs fed A2AA suggests rate of digesta passage increased and offers an explanation for reduced N and DM digestibility in treated pigs. Despite adverse effects of A2AA, efficiency of postabsorptive N metabolism increased. As a percentage of N consumed and compared to control pigs, urinary N decreased 15% (P < .01) and retained N increased 12% (P < .05) in animals fed A2AA. Data from these studies show net efficiency of N metabolism is improved in swine given A2AA.
我们研究了α2-肾上腺素能受体拮抗剂（A2AA）对氮（N）分配的影响。所喂饲的日粮含有19.8%的粗蛋白和1.15%的赖氨酸。猪按体重的一定比例饲喂日粮，该比例约等于其自由采食量的90%。在试验1中，猪（每组n = 11）饲喂基础日粮，并每隔8小时皮下注射一次，持续11天，注射生理盐水、RX821002（25毫克/次）或西马特罗（0.6毫克/次）。与注射生理盐水的猪相比，注射RX821002（降低15%，P < 0.05）或西马特罗（降低17%，P < 0.05）的猪，其尿氮占摄入氮的百分比降低。在试验2中，猪每天皮下注射3次生理盐水（n = 6）或25毫克RX821002（n = 6），或者饲喂含150 ppm RX821002的日粮并每天注射3次生理盐水（n = 6），持续11天。RX821002降低了表观干物质和氮消化率（P < 0.05）。与对照组相比，注射或口服RX821002时，尿氮占摄入氮的百分比分别降低了15%和18%，但差异不显著。试验3评估了饲喂0（n = 6）、37.5（n = 5）、75（n = 6）或150 ppm（n = 6）水平的RX821002的效果。对比显示，日增重和表观氮消化率呈线性剂量依赖性下降（P < 0.05）。与未处理的对照组相比，饲喂含37.5、75或150 ppm RX821002日粮的猪，其尿氮占消耗氮的百分比分别降低了2%、12%和10%，但差异不显著。试验4比较了饲喂基础日粮或含100 ppm RX821002日粮的猪（每组n = 6）与饲喂含25或100 ppm育亨宾日粮的猪的氮平衡情况。各处理组降低了表观氮和干物质消化率（P < 0.05）。对于100 ppm RX821002、25 ppm育亨宾或100 ppm育亨宾，尿氮占消耗氮的百分比分别降低了16%（P > 0.05）、18%（P < 0.05）和24%（P < 0.05）。将试验2、3和4中对照组猪（n = 18）或饲喂A2AA的猪（所有A2AA来源和剂量；n = 41）的数据合并并进行分析。饲喂A2AA降低了表观氮和干物质消化率（P < 0.01）。饲喂A2AA的猪粪便水分含量较高这一事实表明，食糜通过速度加快，这为处理组猪氮和干物质消化率降低提供了解释。尽管A2AA有不良影响，但吸收后氮代谢效率提高。与对照组猪相比，饲喂A2AA的动物尿氮占消耗氮的百分比降低了15%（P < 0.01），留存氮增加了12%（P < 0.05）。这些研究数据表明，给猪饲喂A2AA可提高氮代谢的净效率。
