Winery by-products as a feed source with functional properties: dose–response effect of grape pomace, grape seed meal, and grape seed extract on rumen microbial community and their fermentation activity in RUSITEC

Table 2 Fermentation characteristics of fermentation liquid as affected by dietary treatment^a

Item	Treatment						SEM	Overall P-value	Contrast P-value
Item	CON	EXT	GP-low	GP-High	GS-low	GS-high	SEM	Overall P-value	EXT vs. GP	EXT vs. GS	GP vs. GS
pH	6.57	6.58	6.64^*	6.62	6.61	6.65^*	0.04	0.006	0.021	0.024	0.945
Redox, mV	−243.8	−239.0	−241.7	−232.2	−246.4	−231.9	6.7	0.276	0.749	0.979	0.670
Ammonia, mmol/L	14.45	12.00^*	12.93^*	11.26^*	13.64^*	12.70^*	0.24	< 0.001	0.676	< 0.001	< 0.001
Methane, %	9.90	9.55	10.53	10.05	10.49	10.37	0.32	0.011	0.005	0.001	0.489
Carbon dioxide, %	84.33	84.19	83.56	83.83	83.23^*	83.62	0.48	0.032	0.097	0.014	0.489
Methane, mL/d	87	78	86	79	84	81	7.80	0.250	0.305	0.262	0.892
Carbon dioxide, mL/d	734	685	677⁺	651^*	667	648^*	44.76	0.094	0.417	0.304	0.778
Total fermentation gas, mL/d	871	815	810	777⁺	801	775^*	55.83	0.124	0.498	0.403	0.836
VFA, mmol/L	128.5	124.8	119.5^*	120.4^*	124.0	117.7^*	5.6	< 0.001	0.016	0.044	0.584
VFA composition, %
Acetate	48.57	50.35^*	49.24	50.68^*	48.89	49.53	0.73	< 0.001	0.338	0.009	0.031
Propionate	24.60	26.70	25.05	26.30	25.87	24.53	1.12	0.158	0.239	0.088	0.493
Butyrate	10.82	9.74^*	10.76	9.62^*	10.67	10.37	0.18	< 0.001	0.035	< 0.001	0.053
Isobutyrate	0.96	0.77^*	0.92	0.87^*	0.94	0.94	0.04	< 0.001	< 0.001	< 0.001	0.001
Valerate	8.09	6.76^*	7.59	6.88^*	7.26	7.86	0.43	0.014	0.181	0.030	0.267
Isovalerate	2.94	2.73	2.67⁺	2.56^*	2.79	2.92	0.11	0.004	0.174	0.161	0.002
Caproate	3.08	2.31^*	2.92	2.34^*	2.75	2.89	0.29	0.008	0.102	0.012	0.233
Heptonate	0.96	0.68^*	0.84	0.76⁺	0.82	0.92	0.11	0.013	0.072	0.008	0.228
Antioxidant capacity, µg/mL^b	2.58	2.87	2.24	2.41	2.48	2.53	0.16	0.129	0.007	0.057	0.251

Values in the same row with * significantly differ from CON (P < 0.05) or with + tend to differ from CON (0.05 < P ≤ 0.10) according to Dunnett’s test
^aDiets without (CON) or with different inclusion levels of grape pomace (GP-low and GP-high) or grape seed meal (GS-low and GS-high) or supplemented with grape seed extract (EXT)
^bExpressed as Trolox equivalents

ISSN: 2049-1891