Effects of monensin and virginiamycin supplementation in finishing diets with distiller dried grains plus solubles on growth performance and digestive function of steers

Figures & data

Table 1. Diet formulations and feeding programme during 42-d transition period from arrival of steers into the feedlot to initiation of Trial 1.

	Transition diets
Item	21-d	7-d	7-d	7-d
Ingredient (%, dry matter basis)
Steam-flaked corn	36.68	46.01	53.82	62.85
Distillers dried gains + solubles	20.00	20.00	17.50	15.00
Alfalfa hay	20.00	10.00	6.00	6.00
Sudangrass hay	12.00	12.00	12.00	6.00
Tallow	2.00	2.00	2.00	2.50
Molasses	8.00	8.00	6.00	5.00
Urea	0.45	0.65	0.75	0.75
Limestone	0.73	1.20	1.49	1.43
Tracemineralized salt^a	0.30	0.30	0.30	0.30
Magnesium oxide	0.10	0.10	0.10	0.17
TruMax^b	0.04	0.04	0.04
Nutrient composition (DM basis)^c
NE of maintenance (Mcal/kg)	1.97	2.06	2.11	2.21
NE of gain (Mcal/kg)	1.32	1.40	1.45	1.54
Crude protein (%)	16.0	15.5	14.9	14.5
NDF (%)	28.0	25.4	23.3	19.0
Ether extract (%)	6.4	6.5	6.5	7.0
Calcium (%)	0.80	0.80	0.81	0.75
Phosphorous (%)	0.37	0.38	0.37	0.36

^a Trace mineral salt contained: CoSO₄, 0.068%; CuSO₄, 1.04%; FeSO₄, 3.57%; ZnO, 0.75%; MnSO₄, 1.07%; KI, 0.052% and NaCl, 93.4%.

^b TruMax-Cr, Vi-COR, Mason City, Iowa.

^c Based on tabular values for individual feed ingredients (NRC 1996) with the exception of supplemental fat, which was assigned NE_m and NE_g values of 6.03 and 4.79 Mcal /kg, respectively (Zinn 1988).

Table 2. Composition of experimental diets fed to steers.

	Treatments
Item	Control	Monensin	Virginiamycin
Ingredients (%, dry matter basis)
Alfalfa hay	6.00	6.00	6.00
Sudangrass hay	6.00	6.00	6.00
Steam-flaked corn	62.85	62.85	62.85
Distillers dried gains + solubles	15.00	15.00	15.00
Yellow grease	2.50	2.50	2.50
Cane molasses	5.00	5.00	5.00
Limestone	1.43	1.43	1.43
Urea	0.75	0.75	0.75
Magnesium oxide	0.17	0.17	0.17
Trace mineral salt^a	0.30	0.30	0.30
Monensin (g/T)	0	34.1	0
Virginiamycin (g/T)	0	0	25.6
Nutrient composition (DM basis)^b
NE (Mcal/kg)
Maintenance	2.21	2.21	2.21
Gain	1.53	1.53	1.53
Crude protein (g/kg)	14.5	14.5	14.5
Ether extract (g/kg)	7.0	7.0	7.0
Calcium (g/kg)	0.75	0.75	0.75
Magnesium (%)	0.30	0.30	0.30
Phosphorus (g/kg)	0.36	0.36	0.36
Potassium (g/kg)	0.85	0.85	0.85

^a Trace mineral salt contained: CoSO₄, 0.068%; CuSO₄, 1.04%; FeSO₄, 3.57%; ZnO, 0.75%; MnSO₄, 1.07%; KI, 0.052% and NaCl, 93.4%.

^b Based on the tabular values for individual feed ingredients (NRC 1984) with exception of supplemental fat which was assigned NE_m and NE_g values of 6.03 and 4.79 Mcal /kg, respectively (Zinn 1988).

Table 3. Treatment effects on growth performance of feedlot steers and NE value of the diet.

	Treatments			P-value
Item	Control	Monensin	Virginiamycin	Control vs. Supplement	Monensin vs. Virginiamycin	SEM
Days on test	145	145	145
Pen replicates	9	9	9
Live weight (kg)^a
Initial	313	316	314			1
Final d	541	557	559	0.05	0.91	6
ADG kg	1.59	1.69	1.71	0.07	0.78	0.05
DMI (kg/d)	8.60	8.32	8.31	0.21	0.94	0.17
ADG/DMI	0.185	0.203	0.207	<0.01	0.50	0.003
Diet NE (Mcal/kg)
Maintenance	2.29	2.48	2.51	<0.01	0.59	0.03
Gain	1.60	1.77	1.79	<0.01	0.59	0.03
Observed/expected NE
Maintenance	1.04	1.12	1.14	<0.01	0.59	0.02
Gain	1.05	1.16	1.17	<0.01	0.59	0.02

ADG, average daily gain; DMI, dry matter intake; NE, net energy.

^a Initial and final weights were reduced by 4% to adjust for digestive tract fill. Final weights were carcass adjusted (carcass weight/0.64, average dressing percentage).

Table 4. Treatment effects on carcass characteristics of feedlot steers.

	Treatments			P-value
Item	Control	Monensin	Virginiamycin	Control vs. Supplement	Monensin vs. Virginiamycin	SEM
Carcass weight (kg)	347	357	358	0.05	0.91	4
Dressing percentage	63.4	64.5	64.3	0.12	0.75	0.3
KPH (%)^a	2.47	2.47	2.34	0.38	0.11	0.05
Subcutaneous fat thickness (cm)	1.18	1.18	1.16	0.88	0.86	0.08
LM area (cm^2)	82.3	83.5	83.7	0.41	0.89	1.3
Marbling score^b	5.03	4.74	5.33	0.98	0.04	0.19
Retail yield (%)^c	49.9	49.8	49.9	0.98	0.74	0.3

^a Kidney, pelvic and heart (KPH) fat as a percentage of carcass weight.

^b Using 3.0 as minimum slight, 4.0 as minimum small, 5.0 as minimum moderate, 6.0 minimum modest, etc. (USDA 1997).

^c Estimated retail yield of boneless, closely trimmed retail cuts from the round, loin, rib and chuck (percentage of HCW; Murphey et al. 1960) = 52.56 − 1.95 × subcutaneous fat − 1.06 × KPH + 0.106 × LM area − 0.018 × HCW.

Table 5. Treatment effects on characteristics of ruminal and total tract digestion in Holstein steers.

	Treatments			P-value
Item	Control	Monensin	Virginiamycin	Control vs. Supplement	Monensin vs. Virginiamycin	SEM
Steer replications	3	3	3
Intake (g/d)
Dry matter^b	6687	6688	6690
OM	6330	6331	6332
Starch	3262	3262	3262
N	143	143	143
Flow to the duodenum (g/d)
OM	3261	3396	3322	0.16	0.29	37
Starch	631	615	584	0.47	0.52	29
N	167	160	171	0.51	0.02	1
Microbial N	92	73	84	0.03	0.07	2
Ammonia-N	6.15	5.91	5.58	0.52	0.64	0.43
Non-ammonia–N	161	155	165	0.52	<0.01	0.58
Feed N	54	67	68	0.03	0.92	2
Ruminal digestibility kg/kg intake
OM	0.631	0.579	0.608	<0.01	0.02	0.003
NDF	0.517	0.428	0.447	0.04	0.43	0.014
Starch	0.807	0.811	0.821	0.47	0.52	0.009
Feed N	0.622	0.531	0.529	0.03	0.92	0.014
Microbial N efficiency^b	23.30	19.97	21.83	0.09	0.17	0.621
N efficiency^c	1.12	1.08	1.15	0.50	<0.01	0.004
Fecal excretion (g/d)
Organic matter	1350	1366	1484	0.29	0.19	43.20
Starch	33.76	30.73	39.87	0.78	0.24	3.91
N	46.81	42.70	43.52	0.28	0.81	2.10
Total tract digestibility kg/kg intake
OM	0.787	0.784	0.765	0.29	0.19	0.007
Starch	0.990	0.991	0.988	0.78	0.25	0.001
N	0.674	0.702	0.697	0.28	0.81	0.014

^a DMI was restricted to 2.2% of BW daily.

^b Microbial N g/kg OM fermented.

^c Non-ammonia-N flow to the small intestine as a fraction of N intake.

Table 6. Treatment effects on ruminal fermentation characteristics in Holstein steers.

	Treatments			P-value
Item	Control	Monensin	Virginiamycin	Control vs. Supplement	Monensin vs. Virginiamycin	SEM
Ruminal pH	5.94	6.05	6.10	0.02	0.17	0.02
Total VFA, mM	88.7	83.6	81.1	0.04	0.23	1.07
Ruminal VFA, mol/100 mol
Acetate	52.7	51.8	52.5	0.70	0.72	1.10
Propionate	27.7	30.6	31.4	0.12	0.64	1.03
Isobutyrate	0.74	0.72	0.67	0.84	0.86	0.16
Butyrate	14.2	12.8	12.4	0.31	0.77	0.96
Isovalerate	2.2	2.0	0.75	0.38	0.28	0.60
Valerate	2.4	2.0	2.3	0.42	0.32	0.18
Acetate/propionate	1.92	1.80	1.81	0.54	0.96	0.13
Methane^a	0.49	0.45	0.45	0.09	0.74	0.01

^a Methane, mol/mol glucose equivalent fermented.

NRC. 1996. Nutrient requirements of beef cattle. 7th rev. ed. Washington (DC): National Academies Press.

 Google Scholar

Zinn RA. 1988. Comparative feeding value of supplemental fat in finishing diets for feedlot steers supplemented with and without monensin. J Anim Sci. 66:213–227.

 PubMed Web of Science ®Google Scholar

NRC. 1984. Nutrient requirements of beef cattle. 6th rev. ed. Washington (DC): National Academies Press.

 Google Scholar

USDA. 1997. United States standards for grading of carcass beef. Washington (DC): Agricultural Marketing Service, USDA.

 Google Scholar