Influence of monensin on Holstein steers fed high-concentrate diets containing soybean meal or urea.
We conducted two growth trials to evaluate the effects of monensin on amino acid sparing. When Holstein steers were fed a 90% concentrate diet supplemented with soybean meal (13.5% CP), the DMI, ADG, and efficiencies of feed and nitrogen utilization were greater than with urea (P < .10). Monensin improved ADG with both nitrogen supplements (P < .01), but the positive effects of monensin on efficiencies of feed (P = .12) and nitrogen (P = .26) utilization were greater for soybean meal than for urea. Increasing amounts of monensin (0, 11, or 22 mg/kg of DM) caused a linear increase in DMI with urea. Diets with soybean had greater intakes than diets with urea (P < .01); the greatest intake was of a soybean diet with monensin at 11 mg/kg of DM. Holstein steers fed soybean meal at 13.5% CP had lower DMI and greater efficiencies of feed and nitrogen utilization than steers fed 16.7% CP (P < .10). Crude protein level had no effect on ADG (P > .10). Monensin always increased the efficiencies of feed and nitrogen utilization (P < .05), but these trends were greater for diets with 16.7 than for those with 13.5% CP. Overall, monensin decreased DMI (P < .01), but this effect was greater for 16.7% than for 13.5% CP. Because the positive effects of monensin on diet NEg (P = .16) and efficiency of nitrogen utilization (P = .26) were greater for soybean meal than for urea, it seemed that monensin was sparing amino acids.
Lana
R P
RP
Department of Animal Science, Cornell University, Ithaca, NY 14853, USA.
Fox
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DG
Russell
J B
JB
Perry
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TC
D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D003049:Coccidiostats / Q000494:pharmacology*; D004032:Diet / Q000662:veterinary*; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects / Q000502:physiology; D008297:Male; D008985:Monensin / Q000494:pharmacology*; D009584:Nitrogen / Q000378:metabolism; D011897:Random Allocation; D013025:Glycine max / Q000592:standards*; D014508:Urea / Q000494:pharmacology*; D015430:Weight Gain / Q000187:drug effects / Q000502:physiology
D003049:Coccidiostats; D014508:Urea; D008985:Monensin; D009584:Nitrogen