Effects of sugar sources and doses on fermentation dynamics, carbohydrates changes, in vitro digestibility and gas production of rice straw silage

Figures & data

Table 1. Chemical composition, pre-ensiled characteristics and bacterial population of raw materials.

Items	Rice straw	Molasses
Chemical composition (g/kg DM)
Dry matter (g/kg FW)	445.71	517.74
Organic matter	893.68	782.17
Crude protein	62.59	41.22
Water soluble carbohydrate	53.23	659.81
Glucose	13.86	43.78
Fructose	15.08	46.25
Xylose	ND	ND
Neutral detergent fibre	603.04	NA
Acid deterge fibre	377.10	NA
Acid detergent lignin	54.81	NA
Cellulose	322.29	NA
Hemicellulose	225.94	NA
Pre-ensiled characteristics
pH	6.59	6.27
Buffering capacity (mEq kg/DM)	41.22	NA
Fermentation coefficient	54.90	NA
Bacterial population (log10 cfu/g FW)
Lactic acid bacteria	4.41	NA
Aerobic bacteria	6.39	NA
Moulds	3.88	NA
Yeasts	4.57	NA

DM: dry matter; FW: fresh weight; mEq: milligram equivalent; cfu: colony-forming units; ND: no detected; NA: no analysis.

Table 2. Effect of additives and ensiling days on pH, organic acids and ethanol composition of rice straw silage.

Items	Treatment^1	Ensiling days						SEM	Significance
		3	6	9	15	30	60		D	T	D × T
pH	Control	5.41^aA	5.06^aAB	4.89^aBC	4.72^aBC	4.68^aC	4.94^aBC	0.03	*	*	*
	2% M	4.44^bcA	4.21^cAB	4.12^dB	4.18^bAB	4.21^bAB	4.42^bAB
	3% M	4.32^cAB	4.30^bcAB	4.05^dC	4.13^bBC	4.13^bcBC	4.39^bcA
	4% M	4.36^bcA	4.27^cA	4.01^dBC	4.01^bC	3.95^bcC	4.19^cdAB
	0.02% E	4.67^bA	4.51^bB	4.36^bcC	4.05^bE	3.95^bcE	4.21^bcdD
	0.04% E	4.61^bcA	4.44^bcA	4.41^bA	4.02^bBC	3.89^cC	4.15^dB
	0.06% E	4.54^bcA	4.42^bcAB	4.18^cdBC	3.94^bC	3.91^cC	4.09^dC
Lactic acid (g/kg DM)	Control	14.67^dD	17.89^dD	28.41^bBC	32.93^cAB	37.80^eA	19.88^cCD	1.53	*	*	*
	2% M	25.72^abcB	35.98^abcAB	39.74^abAB	43.35^bcAB	50.18^deA	43.04 ^abAB
	3% M	31.54^aD	38.80^abCD	46.33^aBC	50.59^abB	60.39^cdA	40.39^bC
	4% M	28.45^abC	43.26^aB	47.67^aB	55.90^aAB	64.75^bcA	46.15^abB
	0.02% E	18.14^cdE	29.77^cDE	43.69^aBC	54.76^aB	74.90^abA	41.86^abCD
	0.04% E	14.16^dE	35.00^abcD	42.74^abCD	57.40^aB	80.51^aA	51.49^abBC
	0.06% E	18.96^bcdE	31.27^bcD	44.18^aC	60.90^aB	84.85^aA	59.44^aB
Acetic acid (g/kg DM)	Control	6.92^abD	9.73^aCD	12.09^aC	15.70^aB	22.71^aA	25.46^aA	0.53	*	*	*
	2% M	6.21^abC	7.32^abC	7.27^cC	7.91^cC	10.04^bB	11.99^bcA
	3% M	7.20^abC	7.89^abBC	8.14^bcBC	9.01^bcB	11.13^bA	12.57^bcA
	4% M	5.33^bD	6.20^bCD	7.39^cBC	7.94^cBC	9.06^bB	10.93^cA
	0.02% E	7.27^abC	8.09^abC	9.58^bC	11.16^bC	21.12^aB	26.05^aA
	0.04% E	6.76^abC	8.06^abC	8.64^bcC	10.61^bcC	21.93^aB	27.50^aA
	0.06% E	7.78^aB	8.24^abB	7.80^bcB	9.52^bcB	13.76^bA	16.06^bA
Butyric acid (g/kg DM)	Control	0.00^aB	0.00^aB	0.00^aB	0.36^aB	1.68^aA	2.19^aA	0.05	*	*	*
	2% M	0.00^aB	0.00^aB	0.00^aB	0.00^aB	0.00^bB	0.84^bA
	3% M	0.00^aB	0.00^aB	0.00^aB	0.00^aB	0.00^bB	0.69^bA
	4% M	0.00^aB	0.00^aB	0.00^aB	0.00^aB	0.30^bAB	0.41^bA
	0.02% E	0.00^aC	0.00^aC	0.00^aC	0.00^aC	0.53^bB	1.45^abA
	0.04% E	0.00^aA	0.00^aA	0.00^aA	0.00^aA	0.46^bA	0.82^bA
	0.06% E	0.00^aB	0.00^aB	0.00^aB	0.00^aB	0.00^bB	0.92^bA
Ethanol (g/kg DM)	Control	8.16^abD	12.28^aC	13.26^aBC	15.76^aB	21.41^aA	20.27^aA	0.31	*	*	*
	2% M	7.28^abA	7.55^bcA	7.70^dA	7.68^cA	7.77^cA	7.14^bcA
	3% M	7.32^abA	7.65^bcA	7.34^dA	7.63^cA	7.15^cA	6.32^cA
	4% M	6.93^bA	6.79^cA	7.06^dA	6.66^cA	8.25^cA	8.21^bcA
	0.02% E	8.46^aD	9.26^bcCD	11.71^abABC	12.60^bAB	14.10^bA	10.92^bcBCD
	0.04% E	8.57^aB	10.35^abAB	10.65^bcAB	11.61^bAB	13.20^bA	12.12^bAB
	0.06% E	7.57^abB	7.76^bcB	8.17^cdB	8.39^cB	8.84^cAB	10.87^bcA
Lactic/acetic acid	Control	2.12^cA	1.86^cA	2.35^bA	2.13^cA	1.66^eA	0.78^bB	0.16	*	*	*
	2% M	4.14^abA	4.94^bA	5.46^aA	5.50^abA	5.02^bcdA	3.58^aA
	3% M	4.38^aBC	4.95^bAB	5.69^aA	5.63^abA	5.44^abcAB	3.21^aC
	4% M	5.34^aAB	6.98^aA	6.53^aA	7.08^aA	7.19^aA	4.20^aB
	0.02% E	2.50^bcBC	3.86^bAB	4.56^abA	4.93^bA	3.55^dAB	1.63^bC
	0.04% E	2.10^cB	4.34^bA	5.06^aA	5.46^abA	3.73^cdAB	1.87^bB
	0.06% E	2.55^bcD	3.87^bBCD	5.77^aABC	6.42^abA	6.25^abAB	3.71^aCD

DM: dry matter; SEM: standard error of mean; T: treatments; D: ensiling days; T × D: interaction between treatments and ensiling days.

Values with different small letters show significant differences among treatments in the same ensiling days.

Values with different capital letters show significant differences among ensiling days in the same treatment (p < 0.05).

¹ Control, no additive; 2%M, 2% molasses; 3%M, 3% molasses; 4%M, 4% molasses; 0.02%E, 0.02% fibrolytic enzyme; 0.04%E, 0.04% fibrolytic enzyme; 0.06%E, 0.06% fibrolytic enzyme.

*p < .05.

Figure 1. V-score of 60-day rice straw silage (n = 5, bars indicate standard error of the means). Control, no additive; 2%M, 2% molasses; 3%M, 3% molasses; 4%M, 4% molasses; 0.02%E, 0.02% fibrolytic enzyme; 0.04%E, 0.04% fibrolytic enzyme; 0.06%E, 0.06% fibrolytic enzyme. Means with different small letters shows significant differences among treatments at p < .05.

Table 3. Effect of additives and ensiling days on dry matter, dry matter loss and NH₃-N content of rice straw silage.

Items	Treatment^1	Ensiling days						SEM	Significance
		3	6	9	15	30	60		D	T	D × T
Dry matter (g/kg FW)	Control	352.12^bA	330.33^cAB	327.84^cB	322.06^cB	314.08^cB	317.53^bB	2.98	*	*	NS
	2% M	410.11^aA	410.79^aA	407.63^aA	407.36^aA	398.76^aA	387.52^aA
	3% M	396.07^aA	398.85^aA	399.72^aA	398.51^aA	393.34^aA	394.41^aA
	4% M	401.15^aA	393.61^aA	395.17^aA	394.44^aA	391.23^aA	383.39^aA
	0.02% E	333.51^bA	331.78^cA	327.02^cA	328.71^bcA	326.24^bcA	328.56^bA
	0.04% E	344.72^bA	341.82^bcA	340.32^bcA	336.39^bcAB	332.42^bcAB	321.75^bB
	0.06% E	360.40^bA	355.23^bAB	351.76^bAB	347.32^bAB	348.21^bAB	329.28^bB
Dry matter loss (g/kg DM)	Control	165.68^abD	205.54^aC	229.12^aBC	247.38^aAB	272.08^aAB	263.97^aA	7.15	*	*	*
	2% M	24.59^cD	30.71^cCD	55.03^cBC	63.35^cB	89.39^dA	96.49 ^dA
	3% M	35.49^cD	51.78^cCD	65.86^cBC	70.19^cABC	81.67^dAB	86.58^dA
	4% M	44.82^cA	59.85^cA	58.57^cA	61.92^cA	69.41^dA	81.75^dA
	0.02% E	199.68^aB	217.78^aAB	236.91^aA	233.09^aA	239.98^bA	234.99^bcA
	0.04% E	186.37^abB	202.36^abB	205.38^abB	217.81^aAB	230.59^bAB	250.97^abA
	0.06% E	151.83^bB	164.11^bAB	171.37^bAB	178.89^bAB	186.20^cAB	215.65^cA
NH3-N (g/kg TN)	Control	85.95^bD	114.99^abcCD	129.99^aBCD	148.70^aABC	164.23^aAB	177.46^aA	2.35	*	*	*
	2% M	92.84^abE	104.12^abcDE	111.79^abcCD	124.48^abcBC	135.01^abB	155.68^aA
	3% M	96.43^abB	121.41^abAB	122.35^abAB	126.69^abcAB	130.79^abA	140.13^aA
	4% M	116.48^aA	128.81^aA	130.50^aA	129.82^abA	129.45^bA	130.57^aA
	0.02% E	74.82^bB	81.81^cB	93.84^cAB	94.08^cAB	102.43^bAB	124.20^aA
	0.04% E	92.29^abA	95.87^abcA	96.71^bcA	97.52^bcA	112.33^bA	133.00^aA
	0.06% E	81.60^bB	89.62^bcB	95.92^bcB	104.70^bcB	122.57^bAB	163.25^aA

FW: fresh weight; DM: dry matter; NH₃-N: ammonia nitrogen; TN: total nitrogen; SEM: standard error of mean; T: treatments; D: ensiling days; T × D: interaction between treatments and ensiling days; NS: not significant.

Values with different small letters show significant differences among treatments in the same ensiling days.

Values with different capital letters show significant differences among ensiling days in the same treatment (p < 0.05).

¹ Control, no additive; 2%M, 2% molasses; 3%M, 3% molasses; 4%M, 4% molasses; 0.02%E, 0.02% fibrolytic enzyme; 0.04%E, 0.04% fibrolytic enzyme; 0.06%E, 0.06% fibrolytic enzyme.

*p<.05.

Table 4. Effect of additives and ensiling days on structural carbohydrates composition of rice straw silage.

Items	Treatment^1	Ensiling days						SEM	Significance
		3	6	9	15	30	60		D	T	D × T
NDF (g/kg DM)	Control	647.83^aB	657.02^aAB	669.10^aAB	673.79^aAB	686.45^aA	691.32^aA	2.34	*	*	*
	2% M	614.32^abB	621.64^bcAB	627.03^abcAB	633.71^bcAB	642.26^abAB	659.77^abA
	3% M	588.16^bC	599.77^cBC	605.01^cABC	614.73^bcAB	622.65^abAB	632.03^bcA
	4% M	583.97^bB	593.12^cAB	602.45^cAB	616.42^bcA	603.51^bAB	614.18^cA
	0.02% E	631.94^aB	642.09^abAB	655.17^abAB	661.19^abA	668.74^abA	677.81^abA
	0.04% E	623.67^aA	628.52^bcA	636.70^abcA	634.07^bcA	640.11^abA	649.29^abcA
	0.06% E	617.13^abA	616.52^bcA	610.87^bcA	605.10^cA	604.01^bA	609.56^cA
ADF (g/kg DM)	Control	402.85^aB	406.70^aAB	411.32^aAB	413.04^aAB	422.75^aA	425.08^aA	1.57	*	*	NS
	2% M	385.65^bcA	391.04^abA	392.78^abA	393.46^abA	395.47^abA	403.87^abcA
	3% M	370.75^bcB	372.92^bAB	375.14^bAB	379.48^bAB	384.71^abAB	395.20^bcA
	4% M	365.25^cB	371.20^bAB	377.50^bAB	378.82^bAB	379.31^bAB	388.86^cA
	0.02% E	394.57^abB	398.85^abAB	404.02^abAB	409.82^aAB	414.65^abA	418.28^abA
	0.04% E	387.19^bcA	390.15^abA	395.97^abA	395.52^abA	400.88^abA	405.09^abA
	0.06% E	383.57^bcA	386.68^abA	391.61^abA	392.36^abA	393.58^abA	399.40^bcA
ADL (g/kg DM)	Control	64.65^aA	67.53^aA	69.98^aA	71.66^aA	74.14^aA	74.06^aA	0.91	*	NS	NS
	2% M	54.16^aA	54.46^aA	55.67^aA	56.52^aA	58.68^aA	59.21^aA
	3% M	52.83^aA	53.99^aA	54.42^aA	54.91^aA	56.25^aA	56.49^aA
	4% M	51.49^aA	52.77^aA	52.81^aA	53.09^aA	53.23^aA	53.97^aA
	0.02% E	67.46^aA	68.43^aA	70.34^aA	70.22^aA	71.02^aA	72.28^aA
	0.04% E	66.17^aA	67.70^aA	67.26^aA	68.52^aA	69.99^aA	71.74^aA
	0.06% E	55.74^aA	54.85^aA	58.99^aA	61.10^aA	66.45^aA	69.92^aA
Cellulose (g/kg DM)	Control	338.20^aA	339.18^aA	341.34^aA	341.38^aA	348.61^aA	351.03^aA	1.14	*	*	NS
	2% M	331.49^abA	336.58^aA	337.11^aA	336.94^aA	336.79^abA	344.66^abA
	3% M	317.92^bB	318.93^bB	320.72^aB	324.57^aAB	328.46^bAB	338.76^bcA
	4% M	313.75^bB	318.43^bB	324.69^aAB	325.73^aAB	326.08^bAB	334.88^bcA
	0.02% E	327.11^abA	330.42^abA	333.67^aA	339.61^aA	343.62^aA	346.00^abA
	0.04% E	321.03^bA	322.44^bA	328.71^aA	327.01^aA	332.89^abA	335.35^bcA
	0.06% E	319.84^bA	321.83^bA	326.62^aA	327.26^aA	327.13^bA	329.48^cA
Hemicellulose (g/kg DM)	Control	244.97^aA	250.32^aA	257.77^aA	260.75^aA	263.70^aA	266.24^aA	1.84	*	*	*
	2% M	228.67^aB	230.60^abAB	234.25^abAB	240.25^abAB	246.79^abAB	255.91^abA
	3% M	217.41^aA	226.85^bA	229.88^abA	235.25^abcA	237.94^abA	236.79^abcA
	4% M	218.73^aA	221.93^bA	224.95^abA	227.60^bcA	224.20^abA	225.32^bcA
	0.02% E	237.37^aA	243.25^abA	251.16^aA	251.37^abA	254.09^aA	259.53^abA
	0.04% E	236.48^aA	238.37^abA	240.72^abA	238.55^abA	239.24^abA	242.20^abcA
	0.06% E	233.56^aA	229.85^abA	219.26^bAB	212.75^cB	210.43^bB	210.16^cB

DM: dry matter; NDF: neutral detergent fibre; ADF: acid detergent fibre; ADL: acid detergent lignin; SEM: standard error of mean; T: treatments; D: ensiling days; T × D: interaction between treatments and ensiling days; NS: not significant.

Values with different small letters show significant differences among treatments in the same ensiling days.

Values with different capital letters show significant differences among ensiling days in the same treatment (p < 0.05).

¹ Control, no additive; 2%M, 2% molasses; 3%M, 3% molasses; 4%M, 4% molasses; 0.02%E, 0.02% fibrolytic enzyme; 0.04%E, 0.04% fibrolytic enzyme; 0.06%E, 0.06% fibrolytic enzyme.

*p<.05.

Figure 2. Dynamic changes of (A) water soluble carbohydrates, (B) glucose, (C) fructose and (D) xylose during fermentation with different treatments (n = 5, bars indicate standard error of the means). Control, no additive; 2%M, 2% molasses; 3%M, 3% molasses; 4%M, 4% molasses; 0.02%E, 0.02% fibrolytic enzyme; 0.04%E, 0.04% fibrolytic enzyme; 0.06%E, 0.06% fibrolytic enzyme. Treatments, ensiling days and their interaction were significant at p < .05.

Table 5. Crude protein, crude ash, gas production kinetics and in vitro degradability of rice straw silage after 60 days of ensiling.

Items	Treatment^1							SEM	Significance
	Control	2%M	3%M	4%M	0.02%E	0.04%E	0.06%E
Crude protein (g/kg DM)	61.020^D	61.910^D	63.060^D	64.010^CD	70.350^AB	73.700^A	68.590^BC	0.130	*
Crude ash (g/kg DM)	144.450^A	116.400^B	118.990^B	119.340^B	138.240^A	141.990^A	135.740^A	0.750	*
GP24 (mL)	50.800^B	48.100^B	45.110^BC	38.110^C	48.570^B	56.300^A	56.290^A	0.870	*
Potential gas production, b (mL)	78.260^B	76.970^B	70.650^C	63.410^D	75.970^B	78.790^B	86.040^A	1.770	*
Gas production rate constant, c (mL h^−1)	0.045	0.043	0.046	0.044	0.044	0.061	0.048	0.001	NS
In vitro dry matter degradability (%)	55.450^B	56.380^AB	57.100^AB	57.600^A	55.230^B	56.270^AB	56.700^AB	0.210	NS
Amount of NDF degraded (g/kg DM)	334.110^A	326.920^A	320.500^AB	315.570^AB	331.180^A	313.020^AB	288.750^B	2.340	*
Amount of ADF degraded (g/kg DM)	213.770^A	193.530^AB	189.660^AB	187.550^B	193.750^AB	191.730^AB	181.650^B	2.670	*

DM: dry matter; SEM: standard error of mean; NS: not significant; GP₂₄: 24-h net gas production.

Values with different capital letters show significant differences among treatments (p<.05).

¹ Control, no additive; 2%M, 2% molasses; 3%M, 3% molasses; 4%M, 4% molasses; 0.02%E, 0.02% fibrolytic enzyme; 0.04%E, 0.04% fibrolytic enzyme; 0.06%E, 0.06% fibrolytic enzyme.

* p<.05.

Figure 3. Gas production profiles (mL/g DM) from in vitro fermentation of rice straw silage for 72 h (n = 5). DM: dry matter; Control, no additive; 2%M, 2% molasses; 3%M, 3% molasses; 4%M, 4% molasses; 0.02%E, 0.02% fibrolytic enzyme; 0.04%E, 0.04% fibrolytic enzyme; 0.06%E, 0.06% fibrolytic enzyme. Treatments, incubation time and their interaction were significant at p < .05.