Elsevier

Livestock Science

Volume 146, Issue 1, June 2012, Pages 47-53
Livestock Science

Trace mineral status and toxic metal accumulation in extensive and intensive pigs in NW Spain

https://doi.org/10.1016/j.livsci.2012.02.019Get rights and content

Abstract

The aim of the present study was to determine trace element status and toxic metal accumulation in extensive and intensive pigs in NW Spain. Soil, feed and animal tissues (liver, kidney and muscle from 112 pigs) were collected from extensive and intensive pig farms across NW Spain and analysed for metals by ICP-MS and ICP-OES. Our results indicate that animals from both extensive and intensive systems showed an adequate mineral status and that toxic metal residues were generally low, no sample exceeding the maximum admissible levels in meat and meat products established by the EU. Trace element concentrations were generally higher in the intensive pigs possibly reflecting mineral supplementation in the concentrate feed. The statistically significantly higher As, Hg and Pb residues as well as the better Fe and Ni status in extensive pigs could be related at least in part with soil ingestion when rooting. On the contrary, the higher Cd accumulation in the intensive pigs can be explained considering Cu and Zn supplementation in the concentrate feed. Our results also seem to indicate that toxic metal accumulation as well as trace element status in different tissues could be related to metabolic aspects (i.e. related to breed and growth rate) as well as certain management practices (i.e. physical exercise when grazing).

Introduction

Intensive production systems have been designed to achieve a very high productivity at relatively low cost. Animals are maintained at very controlled conditions, including nutrition, to ensure minimum fatalities and increased productivity. From a mineral nutrition point of view, and in order to avoid mineral deficiencies, mineral supplements are incorporated into concentrate feed at concentrations exceeding the physiological requirements; this is possible because there are quite large “safety margins” to avoid mineral toxicity, even though toxic effects can appear when given at supra-optimal concentrations. In relatively unpolluted rural areas, mineral supplements represent an important (or even the main) source of essential trace elements in the diet (Suttle, 2010). However, mineral supplements generally contain higher toxic metal concentrations than most feedstuffs (López-Alonso and Miranda, 2011) although, because of its low rate of inclusion in the concentrate feed their contribution to the total dietary metal exposure is low and toxic metal residues in meat and meat products (mainly offal) are generally below the maximum admissible levels established by the EU (for review see López-Alonso et al., 2007).

However, intensive production systems are highly questioned because of animal welfare and environmental contamination: thousand of animals grow up highly confined and producing an extraordinary large amount of waste. In this context, excess of Cu given to pigs as a growth promoter in the mineral supplement is considered one of the main environmental problems in agricultural land. Excess of dietary Cu (up to 90%) that is not absorbed by the animal is excreted into the faeces, producing Cu-enriched manures (Jondreville et al., 2003) and when spread in the agricultural soils leading to increased soil Cu concentrations (Bengtsson et al., 2003, Poulsen, 1998), toxic effects in plants and microorganisms (Coppenet et al., 1993) and other livestock species (López-Alonso et al., 2000, López-Alonso et al., 2006, Miranda et al., 2006).

In contrast, in extensive low-input production systems, where most or even all animal feed is from the own farm and animals hardly or do not receive mineral supplements, mineral deficiencies or mineral imbalances can appear, especially in places where mineral content in the soil is low or shows a low availability (Mateos et al., 2006, Kumaresan et al., 2009). However, where animals are outdoors, toxic metal (but also essential trace element if present at high concentrations in soil) exposure through soil ingestion by foraging could be higher than through the diet. Information on toxic metal exposure through soil ingestion in pigs is not available in the literature, but results of a recent study in beef cattle in NW Spain indicate that toxic metal accumulation in animal tissues is directly related to grazing activity, which is a reflection of soil ingestion when grazing (Blanco-Penedo, 2008). Because the great rooting activity of pigs, particularly when animals are not fitted with nose rings, soil ingestion can be very high (from 19 to 94%; Rivera-Ferre et al., 2001) compared to ruminants (up to 18%; Thornton and Abrahams, 1983) and the effect of soil ingestion on toxic metal residues in tissues could be very important.

In Galicia (NW Spain) most pig production corresponds to intensive indoor industrial farming feed a highly standardised and balanced concentrate diet. However, in the last years there has been an increase in breeding of the Celta pig, an autochthonous breed maintained on local resources on an extensive silvopastoril system. The Celta pig was the traditional breed on farms until the middle of the 20th century – when it suffered an important recession by the introduction of improved breeds in industrial systems – and its new increase is motivated by the consumer demand of animal welfare and environmentally friendly production systems, together with its highly appreciated organoleptic characteristics (Franco et al., 2006).

The aim of the present study was to determine trace element status and toxic metal accumulation in extensive and intensive pigs in NW Spain.

Section snippets

Farms of study

Three representative extensive and intensive farms were selected for this study in the region of Galicia (NW Spain). All farms were located in rural areas with no identifiable source of anthropogenic metal contamination.

Basically, extensive pig farms (regulated by Real Decreto, 1221/2009 on 4th August) were Celta pig farms maintained on native extensive silvopastoral systems. Animals were outdoors at a maximum density of 2.4 LSU/ha. Animal feed was mainly based on the own-farm resources:

Results and discussion

Trace element concentrations in tissues (liver, kidney and muscle) of extensive and intensive pigs in our study are shown in Table 2. In terms of overall trace metal nutrition, trace element concentrations in the liver (the tissue that best indicates the animal mineral status) are generally within the adequate ranges for this species (Cu: 5–100, Fe: 100–200, Mn: 2.3–4.0, Mo: 0.8–1.9, Se: 0.2–1.2, Zn: 40–90 mg/kg wet weight; Puls, 1994, Suttle, 2010) and are also within the range of trace

Conclusion

The results of our study indicate and appropriate mineral status in both extensive and intensive pigs in NW Spain, even though hepatic mineral concentrations were generally higher in the intensive pigs possibly reflecting mineral supplementation in the concentrate feed. The statistically significantly higher As, Hg and Pb residues as well as the better Fe and Ni status in extensive pigs could be related at least in part with soil ingestion when rooting. On the contrary, the higher Cd

Conflict of interest statement

None of the authors have financial, personal or other relationships with other people or organizations within three years from the beginning of the submitted work that could inappropriately influence, or be perceived to influence, their work.

Acknowledgements

This study was supported by the Xunta de Galicia (Spain) (PGIDT02RA6261001PR).

References (38)

  • Commission of the European Communities

    Directive EC 1881/2006. Setting maximum levels for certain contaminants in foodstuffs

    Off. J. Eur. Union

    (2006)
  • M. Coppenet et al.

    Évolution chimique des sols en explotations d'élevage intensif: Exemple du Finistère

    Agronomie

    (1993)
  • EFSA

    Opinion of the Scientific Panel on Contaminants in the Food Chain on a request from the Commission related to cadmium as undesirable substance in animal feed. (Request No EFSA-Q-2003-033). Adopted on 2 June 2004

    EFSA J.

    (2004)
  • EFSA

    Opinion of the Scientific Panel on Contaminants in the Food Chain on a request from the Commission related to lead as undesirable substance in animal feed. (Request No EFSA-Q-2003-032). Adopted on 2 June 2004

    EFSA J.

    (2004)
  • EFSA

    Opinion of the Scientific Panel on Contaminants in the Food Chain on a request from the Commission related to arsenic as undesirable substance in animal feed. (Request No EFSA-Q-2003-031). Adopted on 31 January 2005

    EFSA J.

    (2005)
  • EFSA

    Scientific opinion on arsenic in food. EFSA panel on contaminants in the food chain (CONTAM)

    EFSA J.

    (2009)
  • A. Kabata Pendias

    Trace Elements in Soil and Plants

    (2001)
  • A. Kumaresan et al.

    Mineral profiling of local pig-feeds and pigs reared under resource driven production system to reduce porcine mineral deficiency in subtropical hill ecosystem of Northeastern India

    Trop. Anim. Health Prod.

    (2009)
  • A. Lindén et al.

    Cadmium levels in feed components and kidneys of growing/finishing pigs

    J. AOAC Int.

    (1999)
  • Cited by (27)

    • Review: Nutritional ecology of heavy metals

      2018, Animal
      Citation Excerpt :

      Inorganic salts, such as sulphates, carbonates, chlorides and oxides, are the most common ones. When ingested, these salts are broken down in the digestive tract to form free ions which are then absorbed (Lopez-Alonso, 2012a). In order to ensure the extranutritional effect of some elements on animals, the concentrations of these salts often exceed the physiological requirements, causing fecal excretion.

    View all citing articles on Scopus
    View full text