Growth and feed intake of Nellore steers fed whole corn diets containing feed antibiotics

Abstract Text:  The objective was to investigate the effects of feed antibiotics on growth and feed intake of feedlot steers fed whole corn diets. Ninety-eight Nellore steers (302 ± 47 kg of BW and 24 mo of age) were assigned to a randomized complete block design experiment with 4 blocks (based on initial BW) and 5 treatments (Mon30: monensin 30 ppm; Virg25: virginiamycin 25 ppm; Mon20+Virg25: monensin 20 ppm + virginiamycin 25 ppm; Fla40: flavomycin 40 ppm; Mon20+Fla20: monensin 20 ppm + flavomycin 20 ppm). Pen was the experimental unit. The experiment consisted of a 100-d period. All steers were fed ad libitum with TMR (88.2% DM, 12.5% CP, 71.5% TDN) with 85% whole grain corn and 15% pelleted protein concentrate on a DM basis. Animals were weighed after a 16-h fast on d 0 and 100 of the experimental period to determine the ADG and feed efficiency (G:F, g of BW gain/kg of feed). No effect (P > 0.01) was observed on growth and feed intake of Nellore steers fed whole corn diets containing feed antibiotics (Table 1). Feed antibiotics tested had the same results. Feed antibiotics tested were able to maintain satisfactory performance in finishing beef cattle fed high-concentrate diets based on whole corn.

Table 1. Initial body weight (BWi), final body weight (BWf), dry matter intake (DMI) daily (kg/d) and DMI as % of BW, average daily gain (ADG) and feed efficiency (G:F) of Nellore steers fed whole corn diets containing feed antibiotics
Variables	Feed antibiotics					SEM	P Value
	Mon30	Virg25	Mon20+Virg25	Fla40	Mon20+Fla20
No. of pens (steers)	4 (20)	4 (20)	4 (19)	4 (19)	4 (20)	-	-
BWi (kg)	393	387	392	393	393	3.49	0.755
BWf (kg)	539	534	537	544	539	4.38	0.618
DMI
kg/d	8.4	9.0	8.8	9.3	9.1	0.39	0.578
% of BW	1.8	1.9	1.9	2.0	2.0	0.08	0.731
ADG (kg/d)	1.465	1.466	1.444	1.504	1.463	0.04	0.902
G:F	0.18	0.17	0.17	0.16	0.16	0.01	0.799

Keywords: beef cattle, performance, whole corn diet