One-way ANOVA revealed a significant accession effect across all 12 analyzed mineral elements (p<0.05), with Tukey’s HSD test identifying distinct homogeneous groups. For clarity, results are presented and discussed separately for macronutrients (Table 4) and micronutrients (Table 5).
Macronutrients composition
Calcium (Ca)
Ca ranged from 21,174.19 to 25,529.8 mg kg
-1 DM (mean: 23,037.62) in
V.
sativa and from 15,257.31 to 26,560.47 mg kg
-1 DM in
V.
narbonensis (mean: 22,045.46). Accessions differed significantly for Ca, with V8 forming the highest homogeneous group and V9 the lowest. Both species exceed values reported by
Badrzadeh et al., (2008) under semi-arid conditions (13,700-13,800 mg·kg
-1 DM) but remain below
Vasiljevic et al., (2009) for
V.
sativa (34,530 mg kg
-1 DM). Both species exceed established ruminant Ca requirements (1,800-8,200 mg kg
-1 DM;
Deaville and Flinn, 2000).
Potassium (K)
K concentrations varied significantly among accessions, ranging from 10,061.7 to 14,924.65 mg kg
-1 DM (mean: 11,754.93) in
V.
sativa and from 8,979.14 to 14,934.98 mg kg
-1 DM in
V.
narbonensis (mean: 11,616.61), with accession V8 recording the highest and V9 the lowest. Results align with
Badrzadeh et al., (2008) for
V.
sativa (13,500 mg kg
-1 DM), though lower than the 24,500 mg kg
-1 DM reported by
Enneking (1995) for
V.
narbonensis. Both species exceed K requirements for all ruminant categories (6,000-10,000 mg kg
-1 DM;
Thompson, 1972;
Council et al., 2001).
Phosphorus (P)
P accumulation revealed significant differences among accessions, with
V.
narbonensis displaying a higher average concentration (mean: 3,455.00; range: 2,242.97 to 4,002.43 mg kg
-1 DM) than
V.
sativa (mean: 3,046.16; range: 1,896.27 to 3,968.68 mg kg
-1 DM). Accession V5 formed the highest statistically significant group, whereas V11 represented the lowest. Results exceed those of
Badrzadeh et al., (2008) in semi-arid Iran (840-1,040 mg kg
-1 DM) but align with
FAO (1999) for
V.
narbonensis (3,600 mg kg
-1 DM) and established forage mineral reference values (2,900 mg·kg
-1 DM;
Minson, 1990a). Both species satisfy ruminant P requirements (1,800-3,000 mg kg
-1 DM;
McDowell, 1992;
Council et al., 2001).
Magnesium (Mg)
V.
sativa Mg ranged from 3,185.56 to 4,151.98 mg kg
-1 DM (mean: 3,573.27), consistent with
Caballero et al., (1996) at flowering stage (3,700 mg kg
-1 DM).
V.
narbonensis showed a higher mean (3,771.42 mg kg
-1 DM) and greater variability (2,884.99-5,254.11 mg kg
-1 DM), exceeding the general forage range of 2,600-2,800 mg kg
-1 DM (
Minson, 1990b). Accessions differed significantly for Mg, with V8 forming the highest homogeneous group and V9 the lowest. Both species comfortably meet ruminant Mg requirements (1,000-2,000 mg kg
-1 DM;
McDowell, 1997).
Sodium (Na)
V.
sativa Na ranged from 589.80 to 5,624.12 mg kg
-1 DM (mean: 3,054.63) and from 1,070.96 to 4,003.02 mg kg
-1 DM in
V.
narbonensis (mean: 2,432.19). Overall these concentrations align closely with 3,000-4,000 mg kg
-1 DM range reported in forage legumes (
Edmeades and O’Connor, 2003). Accessions differed significantly for Na, with V2 forming the highest homogeneous group and V12 the lowest. The wide
V.
sativa range suggests species-specific Na uptake mechanisms
(Khan et al., 2012). V.
narbonensis Na falls within ruminant recommendations (1,000-4,000 mg kg
-1 DM;
Underwood, 1999;
Suttle, 2022), while
V.
sativa slightly exceeds this range.
Sulfur (S)
S content differed significantly among all 12 accessions.
V.
narbonensis recorded markedly higher values (3,250.89-4,020.51 mg kg
-1 DM; mean: 3,607.71), than
V.
sativa (1,718.59-2,322.17 mg kg
-1 DM; mean: 1,969.82). Accession V8 formed the highest statistically significant group and V11 the lowest. All values fall within the range reported by
Suttle (2022) (500 to >5,000 mg kg
-1 DM). Notably S levels in
V.
narbonensis exceed the 2,000 mg kg
-1 DM optimum level for effective fiber digestion in ruminants (
Miles and McDowell, 1983).
Micronutrients composition
Manganese (Mn)
Mn ranged from 38.45 to 52.00 mg kg
-1 DM (mean: 45.59) in
V.
sativa and from 30.62 to 55.02 mg·kg
-1 DM in
V.
narbonensis (mean: 43.83), consistent with 50.3 mg·kg
-1 DM reported for common vetch by
Caballero et al., (1996) and the 42.80 mg kg
-1 DM reported for hairy vetch by
Türk et al. (2009). Accessions differed significantly for Mn, with V5 forming the highest homogeneous group and V9 the lowest. Both species exceed the 40 mg kg
-1 DM threshold for ruminants
(Tejada et al., 1987) and fall within the optimal guidelines of 50 mg kg
-1 DM (max 150 mg kg
-1 DM) reported by
Vigh et al., (2023).
Copper (Cu)
V.
narbonensis showed a wide Cu range (9.01-25.33 mg kg
-1 DM; mean: 17.72), substantially higher than
V.
sativa (8.80-11.75 mg kg
-1 DM; mean: 10.08). Accessions differed significantly for Cu, with V5 forming the highest homogeneous group and V11 the lowest. These values exceed the 7.3 mg kg
-1 DM reported for common vetch by
Caballero et al., (1996) but remain below the 19.76 mg kg
-1 DM reported for
V.
villosa by
Türk et al. (2009). Copper content in both species aligned with current ruminant feeding guidelines (optimal: 10 mg kg
-1 DM; max: 35 mg kg
-1 DM) reported by
Nozière
et_al(2018).
Zinc (Zn)
Zinc content ranged from 39.78 to 59.39 mg kg
-1 DM (mean: 48.62) in
V.
sativa and from 36.96 to 76.00 mg kg
-1 DM in
V.
narbonensis (mean: 61.72), consistent with the 30.2 mg kg
-1 DM reported for common vetch by
Caballero et al., (1996) and within
Minson’s (1990a) global pasture range (7 to >100 mg kg
-1 DM). Accessions differed significantly for Zn, with V8 forming the highest homogeneous group and V9 the lowest. Zn levels in both species meet the minimum requirement of 30 mg·kg
-1 DM and remain below the regulatory maximum of 120 mg kg
-1 DM (
NASEM, 2016;
Vigh et al., 2023).
Iron (Fe)
V.
sativa Fe ranged from 252.73 to 1,461.90 mg kg
-1 DM (mean: 644.38) and from 378.05 to 2,172.18 mg kg
-1 DM in
V.
narbonensis (mean:1,010.08), consistent with
Nizam et al., (2022) for common vetch (43.00-2,295.20 mg kg
-1 DM). Accessions differed significantly for Fe, with V5 forming the highest homogeneous group and V12 the lowest. Several accessions exceeded the maximum tolerable Fe concentration of 500 mg kg
-1 DM for grazing animals (
Council, 2005), partly due to soil dust adhering to leaf surfaces in the clay-textured soil (
Kabata-Pendias, 2000).
Boron (B)
B ranged from 24.20 to 34.70 mg kg
-1 DM in
V.
sativa (mean: 30.50) and from 24.90 to 45.44 mg kg
-1 DM in
V.
narbonensis (mean: 30.95), within the range of 14-78 mg kg
-1 DM reported for forage legumes by
Kabata-Pendias (2000) and comparable to the 24 mg kg-1 DM reported for alfalfa by
Gupta (1991). Accessions differed significantly for B, with V8 forming the highest homogeneous group and V12 the lowest. Both species remain well below the ruminant tolerance threshold of 800 mg kg
-1 DM (
Council, 2005), indicating no toxicity risk.
Cobalt (Co)
Cobalt content ranged from 0.28 to 0.73 mg kg
-1 DM in
V.
sativa (mean: 0.52 mg kg
-1 DM) and from 0.35 to 1.09 mg kg
-1 DM in
V.
narbonensis (mean: 0.63 mg kg
-1 DM), consistent with the levels reported for red clover (0.35 mg kg
-1 DM) and lucerne (0.3-0.4 mg kg
-1 DM) by
Underwood (1999). Accessions differed significantly for Co, with V5 forming the highest homogeneous group and V3 the lowest. Both species exceeded the Co requirement of 0.20 mg kg
-1 DM reported for rumen B12 synthesis by
González-Montaña et al. (2020), while remaining well below the maximum tolerable limit of 25 mg kg
-1 DM (
Council, 2005), with no evidence of deficiency or toxicity in any accession.
Despite uniform soil and management conditions (Table 3), accessions differed significantly for all twelve mineral elements, indicating that genetic background is the primary driver of the observed variability. Beyond genotype, seasonal and climatic conditions during plant growth are also known to influence forage mineral concentration, sometimes more strongly than soil characteristics
(Jumba et al., 1995; McDowell, 1997), underscoring the importance of site-specific mineral analyses in forage evaluation (
Suttle, 2022).
ANN analysis of mineral composition
The predictive function, f(x), demonstrates its effectiveness in revealing the differences in mineral composition between
V.
narbonensis and
V.
sativa accessions. Optimal performance was achieved by minimizing prediction error (Fig 3); during the training phase, logistic regression was optimized using the least squares method with the mean squared error (MSE) on the test set: 0.0030044 (Fig 4). The model converged after only 5 iterations out of a maximum of 1,000, reflecting the clear mineral differentiation between the two species.
Among the twelve elements analyzed, Ca, Mg, K and Fe were the strongest contributors to species discrimination in the ANN model, whereas Mn, B and Co contributed less to the separation between
V.
sativa and
V.
narbonensis. These results highlight the capacity of ANNs to identify and model complex, non-linear relationships within multidimensional datasets such as those characterizing plant mineral composition
(Watanabe et al., 2007).
ANOVA revealed significant differences among the 12 accessions for all twelve minerals, while ANN identified Ca, Mg, K and Fe as the most informative elements for discriminating between
V.
sativa and V.
narbonensis. Thus, the two approaches provide complementary information on accession variation and species discrimination.