Table 9.

Effects of feeding medium-chain fatty acid on rumen fermentation of pre-calving, early lactation, and peak lactation cows².

Variable	Treatment1		SEM	P-value
	CON	MCFA		Treatment	Time	Treatment ×Time
Pre-calving (mmol/L)
Acetate	42.34	43.76	1.827	0.71	0.24	0.28
Propionate	8.61	9.93	0.459	0.18	0.49	0.39
Iso-butyrate	0.65a	0.52b	0.024	<0.01	0.13	0.36
Butyrate	6.12	7.13	0.332	0.16	0.75	0.81
Isovalerate	1.08a	0.87b	0.035	<0.01	0.05	0.51
Valerate	0.46	0.50	0.022	0.45	0.51	0.50
TVFA3	59.25	62.45	2.553	0.55	0.28	0.35
A/P3	4.97	4.74	0.074	0.12	0.30	0.25
Early lactation (mmol/L)
Acetate	45.70	51.17	2.361	0.20	<0.01	0.54
Propionate	16.29	17.64	0.767	0.41	0.73	0.67
Iso-butyrate	0.73	0.60	0.039	0.12	0.77	0.20
Butyrate	7.71	9.15	0.463	0.14	0.21	0.78
Isovalerate	1.34	1.28	0.068	0.69	0.04	0.25
Valerate	0.92	1.09	0.067	0.161	<0.01	0.31
TVFA	75.75	81.47	3.320	0.39	0.05	0.97
A/P	3.14	2.85	0.095	0.08	<0.01	0.14
Peak lactation (mmol/L)
Acetate	40.09	41.07	1.179	0.67	0.06	0.27
Propionate	15.54	17.18	0.663	0.22	0.09	0.46
Iso-butyrate	0.74	0.75	0.026	0.78	0.33	0.93
Butyrate	6.67	7.07	0.272	0.47	0.20	0.39
Isovalerate	1.45	1.44	0.054	0.87	0.41	0.54
Valerate	0.98	1.12	0.040	0.11	0.87	0.94
TVFA	65.55	69.66	2.090	0.33	0.14	0.42
A/P	2.61	2.52	0.057	0.47	0.23	0.75

SEM, standard error of mean.

^a-bMeans within a row with unlike superscripts differ (P ≤ 0.05).

¹CON, control treatment, basic diet with no medium chain fatty acids, n = 9. MCFA, MCFA treatment, basic diet and medium chain fatty acids 20 g/d, n = 9.

²Pre-calving, from 21 d before calving to calving, Early lactation, from 1 d to 28 d after calving, Peak lactation, from 29 d to 70 d after calving.

³TVFA, total volatile fatty acid, A/P, the ratio of acetate to propionate.