Effects of ensiling conditions on pyrrolizidine alkaloid degradation in silages mixed with two different Senecio spp.

Figures & data

Figure 1. Major pyrrolizidine alkaloids in Senecio plants (oxidation at the nitrogen atom indicates the N-oxide form).

Figure 2. Mean pH values and NH₃-N contents [g/kg N] after 10 d and 90 d of ensiling in pre-wilted and non pre-wilted silages, with either S. vernalis or S. jacobaea. Treatments were CON (control), LBHE (heterofermentative Lactobacillus buchneri strain LN4637 at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter), LBHO (homofermentative lactobacilli at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter) and SOIL (10 g soil/kg fresh matter).

Figure 3. Contents of fermentation acids (lactic acid, acetic acid and butyric acid) [% of DM] in pre-wilted and non pre-wilted silages, with either S. vernalis or S. jacobaea as means of day 10 and day 90 of ensiling. Treatments were CON (control), LBHE (heterofermentative Lactobacillus buchneri strain LN4637 at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter) and LBHO (homofermentative lactobacilli at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter) and SOIL (10 g soil/kg fresh matter).

Table 1. Nutrient contents [g/kg DM] of silages averaged across storage duration and for pre-wilted and non pre-wilted silages (except for DM content).

	Senecio jacobaea				Senecio vernalis				SEM	p-Values
	CON^†	LBHE^¶	LBHO^£	SOIL^*	CON	LBHE	LBHO	SOIL		Treatment	Senecio spp.	Storage duration	Pre-wilting
Dry matter content^$ [g/kg fresh matter]
Non pre-wilted	311	326	322	319	311	323	325	313	4.4	<0.001	<0.001	0.521	<0.001
Pre-wilted	358	377	372	359	348	363	347	345	4.4
Crude ash	104^a	94.5^b	94.4^b	104^a	106^a	95.0^b	98.5^b	108^a	1.5	<0.001	0.004	<0.001	<0.001
Neutral detergent fibre	546^a	509^b	500^b	554^a	539^a	510^b	497^ab	539^a	4.1	<0.001	0.025	<0.001	<0.001
Acid detergent fibre	327^a	286^b	284^b	331^a	322^a	289^b	286^b	323^a	3.0	<0.001	0.257	0.161	<0.001
Crude protein	151	164	157	151	154^ab	162^a	154^ab	151^b	1.5	<0.001	0.612	<0.001	0.008

^$Corrected according to Weissbach and Strubelt (2008); ^†CON, control; ^¶LBHE, heterofermentative Lactobacillus buchneri strain LN4637 at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter; £LBHO, homofermentative lactobacilli at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter; *SOIL, 10 g soil/kg fresh matter.

^a,bWithin Senecio spp. values not sharing the same superscript differ significantly (p < 0.05).

Table 2. Contents and profile of pyrrolizidine alkaloids (PA) and their N-oxides (PANO) before ensiling.

	Senecio jacobaea				Senecio vernalis
	CON^†	LBHE^¶	LBHO^£	SOIL^*	CON	LBHE	LBHO	SOIL
Total PA-PANO [µg/kg dried sample]	20,470	19,352	22,320	21,582	109,346	95,512	140,953	111,965
Proportion of total PA-PANO [%]^◊
Erucifoline	1.82	1.37	1.80	1.28	-	-	-	-
Erucifoline N-oxide	54.2	54.1	53.6	54.2	0.043	0.032	0.026	0.036
Jacobine	0.035	0.030	0.028	-	-	-	-	-
Jacobine N-oxide	4.52	5.44	4.11	2.68	-	-	-	-
Jacoline^$	-	-	-	-	-	-	-	-
Jacoline N-oxide^$	0.688	0.609	0.388	0.248	-	-	-	-
Jaconine^$	-	-	-	-	-	-	-	-
Jaconine N-oxide^$	0.206	0.446	0.173	0.323	0.010	0.050	0.051	0.007
Retrorsine^$	0.217	0.187	0.295	0.201	0.037	0.037	0.117	0.024
Retrorsine N-oxide^$	12.4	11.8	12.7	12.4	3.32	3.54	3.33	3.49
Riddelliine	-	-	-	-	-	-	-	-
Riddelliine N-oxide	2.44	2.47	2.45	2.57	0.108	0.104	0.102	0.077
Senecionine^$	0.429	0.312	0.478	0.323	1.35	1.48	2.83	1.19
Senecionine- N-oxide^$	15.3	16.1	16.1	17.3	79.2	78.5	77.1	79.1
Seneciphylline^$	0.090	-	-	-	0.161	0.153	0.383	0.121
Seneciphylline N-oxide^$	7.60	7.06	7.75	8.41	9.69	9.78	9.16	9.44
Senkirkine	-	0.073	0.113	0.105	6.09	6.38	6.98	6.54

^†CON, control; ^¶LBHE, heterofermentative Lactobacillus buchneri strain LN4637 at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter; ^£LBHO, homofermentative lactobacilli at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter; ^*SOIL, 10 g soil/kg fresh matter; ^◊limit of quantification per PA-PANO = 5 µg/kg; ^$including naturally occurring isomers.

Table 3. Contents of pyrrolizidine alkaloids (PA) and their N-oxides (PANO) in silages and their proportions [%] after 90 d^◊.

	Senecio jacobaea				Senecio vernalis					p-Values
	CON^†	LBHE^¶	LBHO^£	SOIL^*	CON	LBHE	LBHO	SOIL	SEM	Treatment	Senecio spp.	Storage duration	Pre-wilting
Total PA-PANO [µg/kg dried sample]
After 10 d	2,523	1,845	2,176	2,696	25,075^a	18,845^b	20,145^b	24,385^a	850.2	<0.001	<0.001	0.029	<0.001
After 90 d	2,955	3,273	2,085	2,759	23,942^ab	20,024^b	23,849^ab	26,321^a
Proportions of total PA-PANO after 90 d [%]
Erucifoline	27.8	25.5	26.8	26.3	0.048	0.043	0.063	0.051	1.561	0.592	<0.001	<0.001	0.804
Erucifoline N-oxide	-	-	-	-	-	-	-	-
Jacobine^$	1.87	1.22	1.13	2.36					0.425	0.231	<0.001	<0.001	<0.001
Jacobine N-oxide^$	-	-	-	-	-	-	-	-
Jacoline^$	4.61	4.21	4.01	4.18					0.345	0.938	<0.001	<0.001	<0.001
Jacoline N-oxide^$	-	-	-	-	-	-	-	-
Jaconine^$	9.61^a	7.92^ab	10.78^a	6.01^b					0.677	<0.001	<0.001	0.021	0.518
Jaconine N-oxide^$	-	-	-	-	-	-	-	-
Retrorsine^$	14.7	14.0	15.3	13.5	3.16	3.03	3.46	3.04	0.609	0.255	<0.001	0.041	0.054
Retrorsine N-oxide^$	-	-	-	-	-	-	-
Riddelliine	2.21	2.19	2.40	2.05	0.127	0.163	0.153	0.145	0.170	0.536	<0.001	0.090	0.503
Riddelliine N-oxide	-	-	-	-	-	-	-	-
Senecionine^$	22.6	22.8	21.4	23.5	47.0^a	37.0^b	41.6^ab	47.1^a	1.48	<0.001	<0.001	<0.001	<0.001
Senecionine-N-oxide^$	-	0.137	-	-	1.03^b	1.33^ab	0.513^c	1.55^a	0.080	<0.001	<0.001	0.137	0.691
Seneciphylline^$	9.15^a	7.69^b	8.08^b	8.49^ab	7.25^a	5.86^b	6.07^b	7.25^a	0.204	<0.001	<0.001	<0.001	<0.001
Seneciphylline N-oxide^$	-	-	-	-	-	-	-	-
Senkirkine	7.39	14.3	10.2	13.7	41.4^b	52.6^a	48.1^ab	40.8^b	1.89	<0.001	<0.001	0.006	0.005

^◊Limit of quantification per PA-PANO = 5 µg/kg; ^†CON, control; ^¶LBHE, heterofermentative Lactobacillus buchneri strain LN4637 at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter; ^£LBHO, homofermentative lactobacilli at 3 · 10⁵ cfu/kg fresh matter plus 25 g molasses/kg fresh matter; ^*SOIL, 10 g soil/ kg fresh matter; ^$including naturally occurring isomers; ^$including naturally occurring isomers.

^a,bWithin Senecio spp. values within one row not sharing the same superscripts differ significantly (p < 0.05).

Table 4. p-Values of the interactions effects between Senecio spp. and ensiling treatments (p-values between Senecio spp. and pre-wilting conditions, storage duration as well ensiling treatment and storage duration).

	p-Values
	Senecio spp. × treatment	Senecio spp. × pre-wilting	Senecio spp. × storage duration
Total PA/PANO^† [µg/kg dried sample]	<0.001	<0.001	0.261
Proportion of total PA/PANO [%]
Erucifoline	0.553	0.711	<0.001
Jacobine^$	-	-	-
Jacoline^$	-	-	-
Jaconine^$	-	-	-
Retrorsine^$	0.576	0.417	0.064
Riddelliine	0.677	0.361	0.176
Senecionine^$	<0.001	0.023	<0.001
Seneciphylline	0.082	0.276	<0.001
Senkirkine	<0.001	<0.001	<0.001

^†PA/PANO, pyrrolizidine alkaloids (PA) and their N-oxides (PANO) in silages; ^$including naturally occurring isomers.

Figure 4. Correlation matrix of PA contents after ensiling [µg/kg dried sample] with quality traits from silages with either S. vernalis (A) or S. jacobaea (B). Data from 10 and 90 d of storage are included. Positive correlations are depicted in grey, and negative correlations in black. Areas of circles show the absolute value of corresponding correlation coefficients. Insignificant correlations with p > 0.05 were left blank. DM, dry matter; ADF, acid detergent fibre, NDF, neutral detergent fibre.

Weissbach F, Strubelt C. 2008. Correcting the dry matter content of grass silages as a substrate for biogas production. Landtechnik. 63:210–211.

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