Table 3.

Rumen fermentation parameters in lactating cows selected for high or low milk solid.

Item	HS	LS	SEM	P-value
pH	6.84	6.79	0.094	0.772
NH3-N, mg/dL	9.74	10.11	0.784	0.829
MCP, mg/mL	0.31	0.28	0.015	0.532
VFA concentration, mmol/Lrowhead
Acetic acid	10.91	8.70	0.637	0.081
Propionic acid	4.40	3.10	0.335	0.044
Isobutyric acid	0.72	0.50	0.057	0.054
Butyric acid	2.75	1.99	0.266	0.164
Isovaleric acid	0.41	0.28	0.071	0.386
Valerate acid	0.38	0.29	0.022	0.045
Acetate-to-propionate ratio	2.55	2.79	0.102	0.261
Total VFA, mmol/L	19.58	14.87	1.294	0.065
Molar proportion, %rowhead
Acetic acid	56.36	58.31	0.966	0.335
Propionic acid	22.25	21.20	0.580	0.389
Isobutyric acid	3.63	3.45	0.165	0.623
Butyric acid	13.78	13.21	0.686	0.698
Isovaleric acid	2.02	1.81	0.282	0.726
Valerate acid	2.00	2.02	0.097	0.790

HS = high total milk solid group; LS = low total milk solid group; SEM = standard error of the mean; NH₃-N = ammonia nitrogen; MCP = microbial crude protein; VFA = volatile fatty acid.