Relationship between chemical composition and in situ rumen degradation characteristics of grass silages in dairy cows

Figures & data

Table 1 Diet components of the total mixed ration (TMR) fed to the cows during rumen incubations.

Feed ingredient	g/kg DM in TMR
Maize silage	237.4
Grass silage	395.8
Grass hay/wheat straw	13.5
Soybean meal	47.4
Sweet syrup	9.5
Wet distillers grains with solubles	84.3
Soybean meal (rumen protected)	18.6
Minerals and vitamin premix ^a	10.9
Concentrate ^b	182.6

a Premix composition: calcium 175 g/kg; phosphorous 0.2 g/kg; magnesium 130 g/kg; sodium 50 g/kg; chloride 78 g/kg; vitamin A 600,000 IE/kg; vitamin D 120,000 IE/kg; vitamin E 8,000 IE/kg.

b Contained (%): maize, 30; palm kernel, 22; rapeseed solvent extract, 21.3; citrus pulp, 10; soybean meal (rumen protected), 5; beet molasses, 5; molasses, 2; wheat, 2; chalk (CaO), 0.6; urea, 0.6; salt, 0.5; magnesium oxide (80% MgO), 0.5; palm oil, 0.2; vitamin and minerals premix, 0.3.

Table 2 Chemical composition of grass silages (n = 69) used in this experiment and, grass silage (n = 102) and grass hay (n = 14) samples in the database used by the DVE/OEB₂₀₁₀ system.

		Grass silages used in this experiment				DVE/OEB2010 database ^a
Variable		Mean	SD ^b	Minimum	Maximum	Mean	SD	Minimum	Maximum
Chemical composition (g/kg DM) ^#
	Dry matter (g/kg fresh matter)	454	112	201	680	473	194	143	909
	Ash	102	18	70	192	113	24	31	250
	Crude protein	170	29	109	222	198	48	99	305
	Crude fat	42	7	28	63	40	7	17	62
	Crude fiber	257	26	162	323	265	36	201	342
	Sugar	91	45	12	246	55	49	1	228
	Neutral detergent fibre	491	53	326	611	470	68	330	669
	Acid detergent fibre	268	29	157	332	287	42	220	355
	Acid detergent lignin	19	7	10	40	27	13	10	57
	NDIN ^c (g N/kg DM)	23.5	14.5	6.4	67.0	nd ^d	nd	nd	nd
	ADIN ^e (g N/kg DM)	1.5	0.7	-0.1	4.6	nd	nd	nd	nd
Silage quality parameters ^*
	pH	5.01	0.63	4.00	6.67	nd	nd	nd	nd
	Ammonia fraction	0.07	0.02	0.03	0.13	nd	nd	nd	nd

# Chemical composition of grass silages used in this experiment was determined on freeze dried material;

* Silage quality parameters were determined on air dried material.

a The data were compiled from different in situ experiments that were performed 17 to 50 years ago for different purposes.

b Standard deviation.

c Neutral detergent insoluble nitrogen.

d Not determined.

e Acid detergent insoluble nitrogen.

Fig. 1 Relationship between neutral detergent fibre (g/kg DM) and effective rumen degradable fraction of dry matter of grass silages.

Fig. 2 Relationship between neutral detergent fibre (g/kg DM) and effective rumen degradable fraction of crude protein of grass silages.

Fig. 3 Relationship between crude protein (g/kg DM) and effective rumen degradable fraction of crude protein of grass silages.

Table 3 Average rumen degradable fractions of dry matter, organic matter, crude protein and neutral detergent fibre of grass silages (n = 69) incubated for different time periods (2, 4, 8, 16, 32, 72 and 336 h).

Time periods (h)	Dry matter				Organic matter				Crude protein				Neutral detergent fibre (NDF)
	Mean	SD ^a	Minimum	Maximum	Mean	SD	Minimum	Maximum	Mean	SD	Minimum	Maximum	Mean	SD	Minimum	Maximum
2	0.306	0.067	0.158	0.505	0.273	0.064	0.132	0.479	0.522	0.087	0.343	0.727	-0.001	0.043	-0.094	0.087
4	0.323	0.070	0.156	0.523	0.292	0.065	0.143	0.493	0.531	0.091	0.342	0.723	0.020	0.045	-0.081	0.115
8	0.389	0.076	0.226	0.564	0.367	0.074	0.209	0.547	0.560	0.090	0.341	0.743	0.129	0.070	-0.015	0.443
16	0.528	0.075	0.369	0.715	0.514	0.074	0.338	0.702	0.662	0.082	0.454	0.830	0.326	0.074	0.180	0.512
32	0.698	0.066	0.544	0.838	0.701	0.060	0.544	0.831	0.740	0.071	0.547	0.891	0.605	0.066	0.442	0.728
72	0.797	0.054	0.660	0.877	0.801	0.046	0.658	0.881	0.773	0.070	0.576	0.894	0.764	0.052	0.624	0.863
336	0.841	0.036	0.742	0.916	0.847	0.031	0.761	0.930	0.777	0.065	0.539	0.878	0.846	0.031	0.738	0.905

a Standard deviation.

Table 4 The average, minimum and maximum dry matter, organic matter, crude protein and neutral detergent fiber values for the washout fraction ^a (W), rumen undegradable fraction ^b (U), potentially rumen degradable fraction ^c (D), degradation rate (k _d, h⁻¹) and effective degradability (ED) ^d of 69 grass silages.

Variable	Mean	SD ^e	Minimum	Maximum
Dry matter (DM)
W DM	0.240	0.062	0.101	0.412
U DM	0.159	0.036	0.084	0.258
D DM	0.601	0.054	0.469	0.742
k d	0.043	0.007	0.030	0.064
EDDM2	0.648	0.048	0.528	0.750
EDDM5	0.516	0.055	0.380	0.647
EDDM8	0.449	0.057	0.314	0.592
Organic matter (OM)
W OM	0.205	0.061	0.086	0.389
U OM	0.153	0.031	0.070	0.239
D OM	0.642	0.056	0.498	0.780
k d	0.043	0.007	0.029	0.062
EDOM2	0.640	0.047	0.507	0.760
EDOM5	0.499	0.056	0.351	0.646
EDOM8	0.427	0.058	0.281	0.588
Crude protein (CP)
W CP	0.405	0.087	0.205	0.598
U CP	0.222	0.065	0.122	0.461
D CP	0.373	0.103	0.143	0.584
k d	0.068	0.025	0.024	0.136
EDCP	0.610	0.061	0.478	0.729
REP ^f	0.390	0.061	0.271	0.522
Neutral detergent fibre (NDF)
W NDF	0.007	0.046	0.000	0.090
U NDF	0.154	0.031	0.095	0.262
D NDF	0.839	0.054	0.746	0.951
k d	0.046	0.009	0.022	0.083
Lag time (h)	4.892	1.070	3.320	8.280
EDNDF	0.545	0.046	0.386	0.647

a The fraction disappeared by washing with tap water in a washing machine at 25 °C for 40 min.

b The residual fraction determined after 336 h incubation in the rumen.

c The D fraction was calculated as D = 1-(W + U).

d The ED of DM was calculated by using three passage rates; 0.02 h⁻¹(ED_DM2), 0.05 h⁻¹ (ED_DM5) and 0.08 h⁻¹ (ED_DM8). The ED of OM was also calculated by using three passage rates; 0.02 h⁻¹(ED_OM2), 0.05 h⁻¹ (ED_OM5) and 0.08 h⁻¹ (ED_OM8). The ED_CP was calculated using 0.045 h⁻¹ value of passage rate while the ED_NDF was calculated using 0.025 h⁻¹ value of passage rate.

e Standard deviation.

f Rumen escape protein. 5% of W was added in REP.

Table 5 Relationship between the washable fraction (W), the rumen undegradable fraction (U), the potentially rumen degradable fraction (D), and the effective rumen degradable fraction (ED) of dry matter (DM), organic matter (OM), crude protein (CP) and neutral detergent fibre (NDF), and the chemical composition of grass silages.

Regression equation	R^2	RMSE ^a
Dry matter
W DM = 0.76 (± 0.09) - 0.76 (± 0.37) ash - 0.35 (± 0.16) sugar - 0.83 (± 0.13) NDF	0.40	0.05
U DM= - 0.03 (± 0.01) + 0.62 (± 0.22) ash + 0.47 (± 0.14) ADF ^b	0.23	0.03
D DM = 0.28 (± 0.06) + 0.37 (± 0.14) sugar + 0.59 (± 0.11) NDF	0.30	0.05
EDDM2 = 0.94 (± 0.06) - 0.86 (± 0.29) ash - 0.42 (± 0.10) NDF	0.26	0.04
EDDM5 = 0.86 (± 0.07) - 0.83 (± 0.32) ash - 0.52 (± 0.11) NDF	0.27	0.05
EDDM8 = 0.81 (± 0.07) - 0.77 (± 0.33) ash - 0.57 (± 0.11) NDF	0.29	0.05
Organic matter
W OM = 0.64 (± 0.04) - 0.89 (± 0.09) NDF	0.57	0.04
U OM = 0.25 (± 0.02) - 0.52 (± 0.09) CP - 0.40 (± 0.06) sugar + 1.46 (± 0.40) NDF	0.57	0.02
D OM = 0.38 (± 0.06) + 0.53 (± 0.11) NDF	0.25	0.05
k d-OM = 0.08 (± 0.01) - 0.14 (± 0.03) ADF	0.30	0.01
EDOM2 = 1.04 (± 0.03) - 0.41 (± 0.09) NDF - 0.72 (± 0.16) ADF	0.75	0.02
EDOM5 = 0.96 (± 0.03) - 0.58 (± 0.10) NDF - 0.67 (± 0.20) ADF	0.74	0.03
EDOM8 = 0.91 (± 0.04) - 0.66 (± 0.11) NDF - 0.59 (± 0.21) ADF	0.73	0.03
Crude protein
W CP = 0.83 (± 0.08) - 0.31 (± 0.08) DM - 1.15 (± 0.28) NDF + 1.15 (± 0.47) ADF	0.56	0.06
U CP = 0.57 (± 0.04) - 1.74 (± 0.19) CP - 0.62 (± 0.12) sugar	0.59	0.04
D CP= - 0.08 (± 0.07) + 0.52 (± 0.08) DM + 1.18 (± 0.35) CP	0.44	0.08
EDCP = 0.47 (± 0.04) - 0.28 (± 0.06) DM + 1.21 (± 0.23) CP + 0.62 (± 0.15) sugar	0.44	0.05
REP ^c  = 0.53 (± 0.05) + 0.28 (± 0.06) DM - 1.21 (± 0.23) CP - 0.62 (± 0.15) sugar	0.44	0.05
Neutral detergent fibre
U NDF = 0.09 (± 0.03) - 0.29 (± 0.11) DM + 0.52 (± 0.12) ADL ^d	0.21	0.03
D NDF = 0.80 (± 0.01) + 0.45 (± 0.14) NDF	0.13	0.05
k d-NDF = 0.05 (± 0.01) + 0.24 (± 0.03) DM - 0.14 (± 0.01) ADF	0.54	0.01
EDNDF = 0.54 (± 0.01) + 1.83 (± 0.07) DM - 0.99 (± 0.05) ADF	0.91	0.01

a Root mean square error.

b Acid detergent fibre.

c Rumen escape protein. 5% of W was also added in REP.

d Acid detergent lignin.

Table 6 Regression equations ^a derived using DVE/OEB₂₀₁₀ database (Personal communication, Product Board Animal Feed, The Netherlands).

Regression equations
Crude protein (CP, %)
% W = 94.35 - 0.10 DM ^b
% U = - 0.03 CP + 0.03 NDF
k d = 38.40 + 0.02 CP - 0.14 NDF + 0.0001 NDF^2
Neutral detergent fibre (NDF, %)
% U = 40.90 - 0.65 DOM ^c  + 0.05 NDF
k d = 6.13 - 0.006 NDF

a These are unpublished regression equation received from the Product Board Animal Feed, the Netherlands. No regression equation was derived for dry matter and organic matter. Information about R² values and root mean square error is not available.

b Dry matter.

c Digestion of organic matter.