Effects of alpha2-adrenoceptor antagonists on metabolic processes of swine: II. Nitrogen balance responses.
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.
Cleale
R M
RM
Fort Dodge Animal Health, Cyanamid Agricultural Research Center, Princeton, NJ 08543-0400, USA.
Ingling
J M
JM
Search
D J
DJ
Hadcock
J R
JR
Pausch
M H
MH
D000284:Administration, Oral; D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000821:Animal Feed; D000818:Animals; D004063:Digestion / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004983:Ethanolamines / Q000008:administration & dosage / Q000494:pharmacology; D019329:Idazoxan / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D007279:Injections, Subcutaneous / Q000662:veterinary; D016014:Linear Models; D008297:Male; D009584:Nitrogen / Q000378:metabolism* / Q000652:urine; D011897:Random Allocation; D013552:Swine / Q000378:metabolism*; D015016:Yohimbine / Q000008:administration & dosage / Q000494:pharmacology
D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D015016:Yohimbine; C058525:2-methoxyidazoxan; D009584:Nitrogen; D019329:Idazoxan; C047411:cimaterol