Table 3.

Rumen volatile fatty acids (VFA) concentrations and pH of Bos indicus steers receiving a high-forage (Cynodon dactylon spp.) diet and supplemented or not (CONT; n = 10) with 13 (13NAR; n = 10) or 20 (20NAR; n = 10) ppm of narasin (Zimprova; Elanco Animal Health, São Paulo, SP, Brazil) throughout the experimental period¹

	Treatments			P-Value2
Item	CONT	13NAR	20NAR	SEM	T	D	T × D	CONT vs. NAR	13NAR vs. 20NAR
VFA, mM/L
Acetate	74.21b	72.71a	72.83a	0.163	< 0.0001	< 0.0001	0.12	< 0.0001	0.60
Propionate	13.83a	15.82c	15.22b	0.131	< 0.0001	< 0.0001	0.24	< 0.0001	< 0.01
Isobutyrate	0.81	0.79	0.83	0.018	0.27	< 0.0001	0.92	0.90	0.11
Butyrate	8.89b	8.54a	8.86b	0.073	< 0.01	< 0.0001	0.19	0.04	< 0.01
Isovalerate	1.20	1.20	1.28	0.039	0.32	< 0.0001	0.70	0.49	0.18
Valerate	0.98	0.95	1.00	0.028	0.46	< 0.0001	0.94	0.75	0.23
Total VFA	90.02a	97.62b	102.08b	2.765	0.03	< 0.0001	0.97	0.01	0.25
Ac:Pr	5.40c	4.63a	4.81b	0.048	< 0.0001	< 0.0001	0.41	< 0.0001	0.01
AcBu:Pr	6.04c	5.17a	5.39b	0.049	< 0.0001	< 0.0001	0.48	< 0.0001	< 0.01
Rumen pH	6.70	6.72	6.85	0.065	0.25	< 0.0001	0.33	0.33	0.17
Ammonia, mg/dL	8.38b	5.67a	5.44a	0.621	< 0.01	< 0.0001	0.28	< 0.01	0.80

¹Treatments were offered on a daily basis throughout the experimental period (day 0 to 140). Rumen samples were collected on day 0 (prior to first treatment administration), 14, 28, 56, 84, 112, and 140 of the study, approximately at 0600 h after treatment administration. Rumen ammonia and pH were evaluated every 28 d. Letters within the same line denote differences at the P ≤ 0.05 level.

²T = treatment effect; D = day effect = T × D = treatment × day interaction; CONT vs. NAR = unsupplemented vs. narasin-supplemented animals; 13NAR vs. 20NAR = dose effect of 13 vs. 20 ppm of narasin.