3.1. Differentiation of Iberian Fattening Production
Results of the canonical discriminant analysis based on technical and environmental variables are presented in
Table 3. The most discriminating variables between the fattening types implemented in Iberian pig farms are noted in
Table 3.
From technical variables studied, the most discriminant variables were “LU value”, “Dehesa land use”, and “Sows”. Regarding the second component of the analysis, related to environmental variables, the most discriminant variables were “GW value” and “GW”. Considering both sets of variables together, those variables with a greater discriminant ability were “LU value”, “GW”, and “GW value”.
Differences between fattening management types were observed in technical variables (
Table 3). The most important and significant difference between Iberian farms is found in “
Dehesa land use”, influencing in the fattening management. “
Dehesa land use” increase the natural resources availability when this technical variable moves to higher values. For this reason,
MF showed higher “
Dehesa land use” compared to
DF and it is explained by the higher percentage of fatteners’ acorn and grass-fed during the finishing period. In other technical variables, no significant differences were found due to the great variability shown on
DF data. Nevertheless, the different types of Iberian farms can be characterized through the results obtained. While
MF produces higher
montanera meat production per
dehesa hectare,
DF obtains a greater pig meat production per hectare. A higher meat production in
DF is achieved to a higher pig stocking rate that characterizes the intensification of this type of farm system. On
DF, the production of pigs through the two coexistent types of fattening (
montanera and
cebo de campo) and a higher number of sows both finally increase the pig stocking rate. In contrast, the legal requirement of several hectares of
dehesa for animal feeding purposes reduces the pig stocking rate in
MF. The combined condition of a greater number of animals as an output together with a lower “
Dehesa land use” lead
DF towards dependence on compound feed because of lower natural resource availability per animal produced. Because of this feed dependency, feedstuffs inputs per hectare are 3.5 times superior on
DF than on
MF in this study.
Environmental differences were observed between Iberian farms (
Table 3) majorly caused by the management described previously. Intensification of livestock production increases the inclusion of concentrated feed in the diet and decreases the grazing period, causing negative environmental impacts [
36]. From LCA, “GW” is lower on
MF than
DF which indicates that a greater use of natural resources in
MF is the best measure for reducing the environmental impacts on livestock activities [
5,
37,
38], since a high number of animals per unit limit the availability of natural resources increasing the consumption of compound feed on
DF. In contrast, LCA shows a trend towards greater “LO” in
MF than
DF. The trend might correspond to the attachment of natural resources on
montanera that requires a higher area requirement for feeding animals versus a lower land requirement in
cebo de campo (feedstuffs inputs).
Economic differences were observed between the participant Iberian farms (
Table 3). The relationship between the economic value generated and technical variables indicates that
MF obtains higher income per livestock unit (LU value). The higher income per livestock unit in
MF is due to a higher price of fatteners
montanera in the market compared to other fatteners pigs in other livestock systems around the globe [
39,
40]. In addition, the economic value obtained for 1 kg CO
2 emitted (GW value) in
MF is higher than in
DF because
MF is based on natural local resources use with the ultimate result of a reduction in GHG emissions [
5].
3.2. Reference Points in Iberian Fattening Production
The canonical discriminant models obtained from the stepwise discriminant analysis based on technical and environmental variables are presented in
Table 4. In both sets of variables, the extracted canonical functions significantly discriminated between the two types of fattening farms (
MF vs.
DF;
p < 0.001, Hotelling’s T2 test). The F-statistics revealed a higher discriminating ability for variables related to environmental performance.
Figure 1 also allows seeing the higher variability in
DF than
MF which seems reasonable due to the different types of animals produced. This outcome is supported by the Mahalanobis distances among farm groups (
Figure 2). The Mahalanobis distances among
MF and
DF were 2.10 for technical variables, 2.16 for environmental variables, and 2.46 for both sets. Therefore, the two fattening types studied are distanced because all pairwise distances were significant [
30].
Discriminant analysis classified the fattening farms on a preassigned group according to the selected technical or environmental variables (
Table 5). The model based on technical and structural variables classified 83.3% of the farms correctly, and the model based on environmental variables correctly classified 97.2% of the participant farms. In addition, 85.7% of classification errors occurred on technical variables, while there was only one misclassification regarding environmental performance. These results indicated that the set of environmental variables discriminate much better than the set of technical variables the differences in management among the two different fattening types. The model based on technical and environmental variables showed a predictive ability equal to that of the model based only on environmental variables. Therefore, the set of environmental variables can be used as reference points to classify the types of fattening carried out on Iberian farms.
Results obtained from canonical correlation analysis are presented in
Table 6. The model extracted 58.52% of the variance from the set of structural and technical variables, and 100% of the variance for the set of environmental variables. Canonical correlations for the first and second pair of canonical variables were 0.973 and 0.844, respectively. These values were significant and represented 69.24% of the variability observed in the model.
The correlation structure (
Figure 3) showed that environmental performance was strongly correlated with land use, degree of intensification, and feeding practices. The first pair (F1) of canonical variables linked environmental values with land use and degree of intensification (
Figure 3), showing that a more intensified fattening system generates a higher economic yield per hectare. The main cause of higher profitability is the increase in the number of animals produced. The production of fatteners
cebo de campo is carried out in a lower area (15 fatteners pigs per hectare) as stated in the legislation [
8], increasing the number of animals by area on more intensive management [
37]. To improve profitability, Iberian farms can produce various production cycles of fatteners on
cebo de campo per year. In contrast, Iberian farms with the exclusive production of fatteners in
montanera only could fit one productive cycle per year as the ability of the Iberian pig breed to feed on acorns is possible from October to March [
41]. Consequently, a greater number of productive cycles in
cebo de campo increases the economic value per hectare.
The second pair (F2) of the canonical variables linked environmental variables with feeding practices (
Figure 3). The best practice to reduce emissions is to increase the proportion of natural resources in animal feeding [
5] and to reduce the use of imported feedstuff. For reaching this goal, the fattening systems must optimize the use of the resources of the
dehesa. As a result, the ratio of fatteners
montanera in relation to the number of animals produced would increase the feeding through natural resources base. The predominance of fattening
montanera together with a better price of fatteners
montanera in the market increases “LU value” in Iberian farms where fatteners
montanera are produced. Consequently, Iberian farms with a lower production of emissions generate more economic value per environmental unit emitted. According to our results and interpretations, the first combination of standardized canonical variables could be considered a predictable measure of LO, and the second combination could be considered a predictable measure of GW.
The fattening management per se determines the economic and environmental characteristics of the farm unit.
MF is more environmentally friendly due to extensive fattening management focused on better use of the
dehesa’s natural resources [
6].
DF is more profitable due to a more intensive management in the fattening period, increasing the stocking rate and feedstuffs inputs. This interpretation is in line with other studies on Iberian pig production [
6] which contributes to show sample representativeness of the participant farms in this study.
3.3. Improvements for More Sustainable Iberian Fattening Production
Through the results obtained in the present study, it is possible to elaborate strategies focused on the improvement of the sustainability of the Iberian pig sector in the
dehesa. Based on the optimal economic and environmental results obtained by the
MF, the Iberian pig traditional livestock should be oriented towards the production of finishing pigs in
montanera as a first option. The reason is mainly based on the environmental values obtained for the close attachment to natural resources during fattening
montanera [
5].
The reduction of inputs required by making more efficient use of internal resources can improve the environmental sustainability of livestock activity [
42]. For this reason, the
MF can be more environmentally sustainable through the optimization of the resource-use of the
dehesa ecosystem. The
MF should maximize “kg
montanera” through increased fatteners
montanera stocking rate in the
dehesa during the finishing period, still under the framed legislation. To achieve this goal, the reforestations are necessary to increase the number of fatteners
montanera that are produced. According to Spanish legislation [
8], the farm unit could increase from 0.25 to a maximum of 1.25 fatteners
montanera per hectare depending on the woodland density. As a result of this improvement, the “kg
montanera” would increase while “LO” per kg of live weight at farm gate would decrease [
43]. This way, increased efficiency generates both an improvement in livestock and environmental performances [
36].
Although the finishing period in
montanera should be the first option for fattening pigs, the
cebo de campo fattening is necessary for several reasons in Iberian traditional pig production at present. For instance, the
cebo de campo fattening is a valid alternative for the overproduction of piglets that exceeds the capacity of the
dehesa to fatten pigs with natural resources only [
11]. In this way, the surplus of piglets is not converted into an undesirable output. If the
cebo de campo was more linked to the land, the feed inputs required would have been reduced [
42]. This is a more favorable scenario since feed production is the main hotspot for several environmental impacts [
36,
38,
44]. For this reason, adapting feeding strategies and animal management can reduce, to some extent, the environmental impacts [
45] of the Iberian traditional pig production. The good management practices can be carried out during the phases of growing and fattening because the Iberian pigs are fed with compound feed and natural resources in both phases.
The results showed that
DF consumes 3.5 times more feedstuffs inputs than
MF. A decrease in compound feed consumption reduces the environmental impacts resulted from feed production [
16]. For that purpose, optimal use of pasture is an appropriate feeding strategy for extensive systems since outdoor pigs obtain a considerable portion of nutritional requirements from grazing, reducing the daily ration [
38]. Furthermore, the integration of pig production into cereal crops is possible [
46]. Iberian pigs can graze the cereal crop before the earing phase [
47], and the harvested grain can be used as additional feed for Iberian pigs, reducing the number of feed inputs. Another feeding strategy to improve the sustainability of pig production is the use of local feed products [
48]. For instance, some authors [
38,
49,
50] investigated the use of local subproducts in swine feed, quantifying a reduction of environmental impacts. In addition, the use of local protein sources in feed production such as sainfoin [
51], grain legumes [
44], or rapeseed [
52], among other alternative sources [
53] showed a reduction of the environmental impact of different pig systems and geographical contexts.