Table 4.

Growth performance, observed net energy concentration, morbidity, and mortality of newly received feedlot calves-fed diets containing different roughage levels (wheat hay; 30% or 60%; DM basis) and supplemental fat (yellow grease; 0 [−FAT] or 3.5% [+FAT]; DM basis)

Item	Roughage level		Supplemental fat		SEM1	P-value
	30%	60%	−FAT	+FAT		Roughage	Fat	Roughage × Fat
Pens (steers)	12 (36)	12 (36)	12 (36)	12 (36)	-	-	-	-
Days on feed	58	58	58	58	-	-	-	-
Growth performance
Initial body weight, kg	200	199	200	200	6.00	-	-	-
Final body weight, kg	285	269	270	284	11.2	0.08	0.13	0.94
Dry matter intake, kg/d	6.00	5.92	5.87	6.04	0.297	0.85	0.64	0.94
Average daily gain, kg	1.47	1.20	1.21	1.46	0.144	0.07	0.09	0.91
Gain efficiency2	0.249	0.204	0.207	0.246	0.016	0.01	0.03	0.80
Observed NE, Mcal/kg3
Maintenance	2.09	1.84	1.86	2.07	0.08	0.01	0.02	0.88
Gain	1.42	1.21	1.23	1.40	0.07	0.01	0.02	0.87
Observed:expected NE ratio4
Maintenance	1.02	1.09	1.02	1.08	0.05	0.22	0.18	0.80
Gain	1.03	1.11	1.03	1.11	0.06	0.22	0.16	0.76
Health
Cattle treated for respiratory disease5, %
First Treatment	50.0	47.2	44.4	52.8	9.61	0.82	0.49	0.82
Second Treatment	19.4	11.1	8.33	22.2	6.50	0.32	0.10	0.32
Third treatment	11.1	2.78	5.56	8.33	6.10	0.14	0.62	0.62
Number of antimicrobial treatments required	1.75	1.34	1.51	1.58	0.272	0.11	0.78	0.30
Mortality, %, (n)	8.33 (3)	2.78 (1)	5.56 (2)	5.56 (2)	3.87	0.31	1.00	0.31

¹ Standard error of the mean.

² Gain-to-feed ratio (G:F; kg/kg).

³ Calculated according to Zinn and Shen (1998).

⁴ Expected values were calculated using the NASEM (2016)—Beef Cattle Nutrient Requirements Model, empirical solution model, based on the diet composition presented in Table 1.

5 Calves were observed daily for bovine respiratory disease (BRD) signs according to the 4-point scale method based on depression, anorexia, respiratory, and temperature (“DART” system) as described by Step et al. (2008) and Wilson et al. (2015).