Table 4.

Effects of treatment and temperature on rumen pH characteristics of finishing steers

Items1	TRT2		TEMP3		SEM	P value
	CON	ADY	TN	HS		TRT	TEMP	TRT × TEMP
Mean pH	5.50	5.59	5.69a	5.39b	0.16	0.2901	0.0029	0.1279
pH variation	0.11	0.13	0.13	0.11	0.02	0.3328	0.3500	0.5440
DUR pH > 5.6, min/d	658	686	741	603	167	0.8093	0.2407	0.0726
DUR of SARA, min/d	450	376	432	394	101	0.5519	0.7604	0.5925
DUR of ARA, min/d	277	314	195b	396a	141	0.6816	0.0381	0.1353
AUC pH > 5.6, h	8.36	13.1	13.2	8.32	3.3	0.0976	0.0923	0.0954
AUC in SARA, h	18.1	17.8	20.8b	15.2a	3.2	0.8482	0.0028	0.2997
AUC in ARA, h	2.75	2.62	0.70b	4.67a	1.72	0.9255	0.0079	0.8862
Mean temperature, °C	40.04	40.01	39.33b	40.73a	0.15	0.7616	<0.0001	0.6289
Temperature variation, °C	0.463	0.417	0.241b	0.638a	0.076	0.5831	0.0001	0.9342
DUR > 40 °C, min/d	624	591	91b	1,124a	65	0.5422	<0.0001	0.4778
AUC > 40 °C/h	21.9	20.2	0.6b	41.5a	4.9	0.7222	<0.0001	0.7641

^a,bLeast squares means within a row with different superscripts differ at P < 0.05.

¹Items are variables derived from indwelling ruminal pH and temperature boluses; DUR = duration, SARA = subacute ruminal acidosis (pH = 5.0 to 5.6); ARA = acute ruminal acidosis (pH < 5.0); AUC = area under the curve (pH units × time, h).

²Treatment is control fed (CON) or control + 3 g/d of an active dried yeast (ADY).

³Temperature is thermoneutral [TN; 18 ± 0.55 °C; 20% relative humidity (RH)] or heat stressed (HS; 35 ± 0.55 °C; 42% RH).