Rp. Lana et al., INFLUENCE OF MONENSIN ON HOLSTEIN STEERS FED HIGH-CONCENTRATE DIETS CONTAINING SOYBEAN-MEAL OR UREA, Journal of animal science, 75(10), 1997, pp. 2571-2579
We conducted two growth trials to evaluate the effects of monensin on
amino acid sparing. When Holstein steers were fed a 90% concentrate di
et supplemented with soybean meal (13.5% CP), the DMI, ADG, and effici
encies 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 t
han 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 gr
eater 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 fe
ed and nitrogen utilization than steers fed 16.7% CP (P < .10). Crude
protein level had no effect on ADG (P > .10). Monensin always increase
d the efficiencies of feed and nitrogen utilization (P < .05), but the
se trends were greater for diets with 16.7 than for those with 13.5% C
P. Overall, monensin decreased DMI (P < .01), but this effect was grea
ter for 16.7% than for 13.5% CP. Because the positive effects of monen
sin on diet NEg (P = .16) and efficiency of nitrogen utilization (P =
.26) were greater for soybean meal than for urea, it seemed that monen
sin was sparing amino acids.