Zinc concentrations in commercial mineral salt mixtures for beef cattle

Abstract

Zinc concentration was measured in 32 salt formulations collected from the states of Mato Grosso, Mato Grosso do Sul and Goiás, Brazil. Zinc content in each sample was determined by inductively coupled plasma atomic emission spectrometry.

Thirty-one samples had values above 300 ppm (range 90 to 8,260 ppm), the maximum  recommended value.

These results show the necessity to monitor the industry, because some mineral mixtures can be dangerous to animal health and the environment, and therefore could impair food safety.

Keywords: Zinc, toxicity, cattle, minerals.

 

Introduction

The increased competition in the Brazilian market for the commercialization of mineral salt mixtures for animal consumption is one of the main reasons why the mineral mixture industry looks to reduce costs with the aim to win competition and guarantee future business. At present, there are around 5,500 formulations of mineral mixtures being sold throughout the Brazilian market (Marçal et al 1999). 

In order to be profitable and maintain its business, the mineral mixture industry has neglected some important aspects related to quality. Some of these aspects are the quality of the raw material sources used in mineral salt mixtures. The materials chosen are usually those most accessible in price, including those of international origin.  

It is believed that some of these raw material sources may be contaminated with toxic elements, such as heavy metals and radioactive substances, generating a subject of concern among nutritionists, clinical veterinarians and technicians that work in the area of health and animal production. 

For this reason, a research project was launched with the intention to evaluate the level of pollutants in mineral formulations used as cattle feed supplement in Brazil. Zinc was the element chosen, because it is considered to be an inorganic element of potential risk to animals, mainly the bovine species (Brito 1993; NRC 1996; Marçal 1996; Marçal et al 1999; AAFCO 2001).
 

Material and methods

Multiple samples of the main formulations in markets in three Brazilian states were collected from the stock of selected rural properties in a time frame of 15 months. These samples were combined, forming a representative "pool" sample of approximately 200 g. 

The samples were stored in transparent plastic containers, previously identified and then  analyzed at the National Commission of Nuclear Energy (CNEN) Laboratory of Poços de Caldas, Minas Gerais, Brazil. After drying at 110 ⁰C, the  samples were solubilized by treatment with nitric, hydrofluoric and hydrochloric acids. Zinc was determined by inductively coupled plasma atomic emission spectrometry using a Varian model 220 FS equipment. 

Statistical analyses were made with the SAS/Basic program, as described in SAS Procedures Guide (1990).

 

Results

In most of the samples (Table 1; Figure 1), the zinc concentration was higher than the acceptable maximum limit of 300 ppm as recommended by the AAFC (2001).   

 

Figure 1. Average values (n=32) for zinc concentrations in mineral salt from three states in Brazil
[AAFCOI: Recommended maximum according to AAFCO 001]

 

 

Discussion

Brazil has one of the largest commercial bovine herds in the world, as highlighted by Martin (1993), and is still looking for the improvement of the cattle industry.  In order to achieve this goal, it is necessary to maintain a health record for the viability of the national industry that counts with a bovine population of 160 million heads (IBGE 2001). In today’s world where epidemics of animal-related health diseases (Mad Cow Disease and Foot and Mouth Disease) have been threatening the potential of foods of animal origin in many countries, the concern for animal health and the safety of its products is an important issue. 

This preliminary study shows  that the levels of zinc in almost all the mineral formulations was of the order of ten times the recommended levels. These findings imply that very probably contaminated raw material has been used in the mineral mixtures with the intention to decrease production costs of the final product (Marçal et al 2001).   

The next phase of our studies will be to evaluate possible sub-clinical effects of zinc toxicity in cattle receiving the mineral mixtures with the highest zinc concentrations. These sub-clinical effects are likely to be manifested in a depression of feed intake and in induced deficiencies of copper and iron (McDonald et al 1987). 

These results show the necessity to monitor the feed industry and when failures are found the proper recommendations should be made. Apart from toxic effects of excessive zinc levels in the feed, there is also the potential negative effect on the environment, as the excretion of unabsorbed quantities of the metal will contaminate soil, plants and water.

Conclusions

The following conclusions can be drawn:

• Only one of  the 32 samples analyzed had a zinc concentration below 300 ppm, considered to be the maximum safe limit.
• The highest value (8,260 ppm) was in a mineral formulation sold in the state of Mato Grosso, where there are very large numbers of beef cattle.

 

References

AAFCO 2001 Official guidelines for contaminant levels permitted in mineral feed ingredients. Association of American Feed Control Officials Incorporated. Indiana. pp: 292-293.

Brito J 1993 Fosfato bicálcico feed grade. Apostila Serrana. Cajati. 17p.  

IBGE 2001 Anuário estatístico do Brasil. In: Efetivo pecuário. v.54.pp:3-62. Rio de Janeiro. 

Marçal W S 1996 Valores sanguíneos de bovinos Nelore, em pastejo de Brachiaria decumbens, suplementados com sal mineral naturalmente contaminado por chumbo. Tese de Doutorado, Universidade Estadual Paulista, UNESP, Campus de Botucatu, São Paulo. 164p. 

Marçal W S, Gaste L, Liboni M, Pardo P E, Nascimento M R and Hisasi C 1999 Lead Concentration in mineral salt mixtures used in beef cattle food supplementation in Brazil. Veterinarski Arhiv, Croatia. 69:6, 349-355. 

Marçal W S, Gaste L, Liboni M, Pardo P E, Nascimento M R and Hisasi C 2001 Concentration of lead in mineral salt mixtures used as supplements in cattle food. Experimenthal and Toxicologic Pathology, Jena 53:7-9.  

Martin I C T 1993 Nutrição mineral de bovinos de corte 2ª ed. São Paulo, Nobel. 173p. 

McDonald P and Edwards R A, Grenhalgh J F D 1987 Animal nutrition, 4ª ed. Burnt Mill, Longman. pp:90-116.

 NRC 1996 Subcommittee on Mineral Toxicity in Animals. In: Mineral tolerance of domestic animals. Washington: National Academy of Science, Washington D. C. 234p.

 SAS Procedures Guide 1990 Version. SAS Institute. 3: 705.

 Received 2 February 2002

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