Effects of a combining feed grade urea and a slow-release product on performance, dietary energetics and carcass characteristics of steers fed finishing diets

Figures & data

Table 1. Ingredients and composition of experimental diets.

	Treatments
Item	SRU + U-4.5	U-3.5	U-4.5	U-5.5
Ingredient composition, % DMB
flaked sorghum	61.00	56.00	61.00	66.00
DDGS	11.00	11.00	11.00	11.00
Sudangrass hay	12.00	18.00	12.00	8.00
U	0.80	0.80	0.80	0.80
Optigen II^a	0.80	–	–	–
Cane molasses	9.83	9.63	10.63	9.63
Yellow grease	2.50	2.50	2.50	2.50
Trace mineral salt^b	0.40	0.40	0.40	0.40
Limestone	1.67	1.67	1.67	1.67
NE concentration^c, Mcal/kg of DM basis
ENm, Mcal/kg	2.03	1.98	2.03	2.09
ENg, Mcal/kg	1.38	1.34	1.38	1.43
Nutrient composition, % of DM^d
Crude protein (N × 6.25)	15.90	13.57	13.71	13.84
Starch	42.36	39.56	42.40	46.38
ADF	9.31	11.36	9.24	8.36
S:ADF ratio	4.55	3.48	4.59	5.55

^a Optigen-II. Alltech de México, Guadalajara Jalisco.

^b Trace mineral salt CoSO₄, 0.068%; CuSO₄, 1.04%; FeSO₄, 3.57%; ZnO, 1.24%; MnSO₄, 1.07%; KI, 0.052%; NaCl, 92.96%.

^c Based on tabular NE 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, respectively (Zinn, 1988).

^d Dietary composition was determined by analyzing subsamples collected and composited throughout the experiment. Accuracy was ensured by adequate replication with acceptance of mean values that were within 5% of each other.

Table 2. Influence of treatments on growth performance and dietary energy of feedlot steers.

	Treatments^a						S:F ratio^b
Item	SRU + U-4.5^c	U-3.5	U-4.5	U-5.5	SEM	SRU + U-4.5 vs.U-4.5	Linear	Quadratic
Pen replicates	5	5	5	5
Number of steers	15	15	15	15
Days on feed	70	70	70	70
Weight, kg^d
Initial	371.65	372.22	372.74	372.86	3.3	0.81	0.89	0.96
Final	461.18	453.31	462.08	473.85	6.5	0.92	0.05	0.82
ADG, kg	1.279	1.158	1.276	1.443	0.052	0.97	<0.01	0.97
DMI, kg	7.896	8.321	8.548	9.085	0.219	0.06	0.03	0.57
DMI, % LW	1.896	2.012	2.046	2.145	0.037	0.02	0.03	0.49
Gain for feed, kg/kg	0.162	0.139	0.149	0.159	0.003	0.02	<0.01	0.97
Dietary NE, Mcal/kg^e
Maintenance	2.14	1.93	2.00	2.05	0.018	<0.01	<0.01	0.71
Gain	1.47	1.28	1.35	1.39	0.016	<0.01	<0.01	0.71
Observed to expected dietary ratio^f
Maintenance	1.06	0.98	0.99	0.98	0.009	<0.01	0.59	0.55
Gain	1.06	0.96	0.98	0.97	0.011	<0.01	0.59	0.55
Observe to expected daily DM intake^g	0.94	1.02	1.02	1.04	0.011	<0.01	0.39	0.50

^a SRU + U-4.5 = 0.80% U plus 0.80% at 4.5 S:F ratio, U-3.5 = 0.80 U at 3.5 S:F ratio, U-4.50 = .80% U at 4.5 S:F ratio, and U-5.5 = 0.80% U at 5.5 S:F ratio.

^b Proportion of starch vs. fibre acid detergent in diet.

^c Source of SRU was Optigen II, Alltech Inc., México, Guadalajara México.

^d The initial and BW was reduced by 4% to adjust for the gastrointestinal fill.

^e The estimation of dietary NE was performed based on observed ADG, DMI and average shrunk weight (SBW) and was estimated by means of the quadratic formula: , where x = NE_m, a = −0.41EM, b = 0.877 EM + 0.41 DMI + EG, and c = −0.877 DMI, where EM = maintenance coefficient of 0.077 Mcal/BW^0.75 (NRC 1984), EG is the daily energy deposited (Mcal/day) estimated by equation: EG = ADG^1.097 × 0.0557W^0.75 (NRC 1984), and DMI is the average daily dry matter intake (Zinn et al. 2008).

^f Observed to expected dietary NE ratio was computed by dividing NE observed between expected diet NE, which was estimated based on tabular values for individual dietary ingredients (NRC 1996).

^g Expected DMI, kg/day = (EM/NE_m) + (EG/EN_g); where, NE_m and EN_g is the diet energy concentration.

Table 3. Treatment effects on carcass characteristics.

	Treatments^a						S:F ratio^b
Item	SRU+U-4.5	U-3.5	U-4.5	U-5.5	SEM	SRU + U-4.5 vs. U-4.5	Linear	Quadratic
Pen replicates	5	5	5	5
Number of steers	15	15	15	15
HCW, kg	301.7	293.1	302.7	308.6	4.12	0.86	0.02	0.72
Cold carcass weight, kg	298.1	289.6	299.1	305.0	4.07	0.86	0.02	0.72
Drip loss, %	1.20	1.18	1.19	1.19	0.023	0.73	0.87	0.98
Dressing percent	65.40	64.66	65.50	65.10	0.32	0.78	0.81	0.28
Longissimus muscle área, cm^2	78.10	77.18	78.30	80.73	1.079	0.90	0.04	0.62
Backfat thickness, mm	0.62	0.62	0.61	0.67	0.065	0.94	0.61	0.70
Kidney-pelvic fat, %	1.93	2.00	2.00	2.13	0.154	0.76	0.55	0.73
Marbling score	3.27	3.20	3.28	3.33	0.157	0.95	0.55	0.95

^a SRU + U-4.5 = 0.80% U plus 0.80% at 4.5 S:F ratio, U-3.5 = 0.80 U at 3.5 S:F ratio, U-4.50 = .80% U at 4.5 S:F ratio, and U-5.5 = 0.80% U at 5.5 S:F ratio.

^b Proportion of starch vs. fibre acid detergent in diet.

[NRC] National Research Council. 1996. Nutrient requirement of beef cattle. 7th ed. Washington (DC): National Academy Press.

 Google Scholar

Zinn RA, Barreras A, Owens FN, Plascencia A. 2008. Performance by feedlot steers and heifers: ADG, mature weight, DMI and dietary energetics. J Anim Sci. 86:1–10.10.2527/jas.2007-0687

 Web of Science ®Google Scholar