Table 5.

Volatile fatty acids (mM) of Angus crossbred cannulated steers (658 ± 79 kg BW) fed free-choice step-up diets that contained increased concentrations of cracked corn¹ plus 0.45 kg of molasses that was individually fed containing or not 3 g of polyclonal antibody preparations against S. bovis, F. necrophorum, and lipopolysaccharides (40%, 35%, and 25% of the preparation, respectively).

Item, mM	Treatment		STEP						P-value
	PAP	CON	SEM	STEP1	STEP2	STEP3	STEP3-7d	SEM	Treat	STEP	Treat × STEP
Acetate	63.3	60.6	2.5	81.6a	60.9b	54.1c	51.1c	2.58	0.42	<0.01	0.57
Propionate	37.8	36.7	2.5	23.4b	43.4a	40.2a	41.9a	2.58	0.70	<0.01	0.60
Butyrate	15.3	15.9	1.2	16.1a	17.8a	16.1a	12.6b	1.22	0.58	0.02	0.29
BCVFA2	1.51	0.35	0.35	1.09	0.78	1.86	1.61	0.40	0.77	0.35	0.46
Valerate	2.65	2.36	0.23	0.80c	2.42b	4.12a	2.69b	0.29	0.39	<0.01	0.12
Caproate	0.85	0.86	0.11	0.27b	0.19b	1.44a	1.51a	0.13	0.97	<0.01	0.89
Total VFA	121.5	118.1	4.3	123.3a	126.5a	117.9ab	111.4b	4.38	0.59	0.01	0.76
A:P	2.0	1.9	0.1	3.7a	1.5b	1.4b	1.3b	0.12	0.82	<0.01	0.86

Diets consisted of gradual inclusion of cracked corn from 0 (Bermudagrass hay only) to 35%, 60%, and 82% for STEP1 (d 14–21), STEP2 (d 21–28), and STEP3 (d 28–35), respectively.

Within a row, means with different superscripts differ, P ≤ 0.05.

BCVFA = branched-chain volatile fatty acids: isobutyrate + isovalerate + 2-methylbutyrate.