Micronutrients and Toxic Elements in Soil, Grass, and Nutritional Supplements and in Blood and Meat Products from Beef Cattle Raised in the Southern Amazon, Brazil

Abstract

The objectives of this study were to investigate the transfer of micronutrients and toxic elements from the environment to animals and food and to obtain information about trace element levels in pasture-based animal production systems. Samples of soil, grass, nutritional supplements, and blood were obtained from different farms in the southern Amazon, Brazil. In addition, samples of muscle, kidney, and liver were obtained from various markets in the same region. All samples were analyzed to determine the concentrations of several elements: Fe, Mn, Zn, Cu, Se, Co, Mo, Ni, Cr, Pb, As, Cd, and Hg. Low concentrations of these elements were detected in soil and grass samples. Deficient or excessive concentrations of several micronutrients were detected in the nutritional supplements. Marginal Se deficiencies were identified in cattle blood. Meat products had low concentrations of Pb, As, Cd, and Hg and were considered rich sources of micronutrients, particularly of Fe, Zn, Se, and Cr in the muscle, Cu and Mo in the liver, and Se in the kidney. Information about the levels of micronutrients and toxic elements in animal production systems, such as pasture-based systems, can support strategies that promote sustainable farming and environmental, animal, and human health.

Keywords: farm; livestock; mercury; one health; pasture; selenium.

1

Location of the study area and farms. The geographic features of the pasture areas were obtained from MapBiomas. Locations of artisanal gold mining were obtained from the Serviço Geológico do Brasil.

2

Descriptive statistics of pseudototal contents of trace elements in the soil of pastures from farms I–VIII located in the southern region of the Amazon. Typical levels for world soil from Kabata-Pendias.

3

Descriptive statistics of trace elements in the grass (in dry matter) from pastures on farms I–VIII located in the southern region of the Amazon. Hg data in the grass were obtained using a Direct Mercury Analyzer, as it was not possible to detect Hg in some samples using ICP-MS.

4

Descriptive statistics of trace elements in bovine nutritional supplements (in dry matter) offered to cattle herds reared on farms located in the southern region of the Amazon. n = number of samples obtained from each nutritional supplement.

5

Estimate of trace element intake by cattle on pasture through consumption of grass and nutritional supplements in the southern region of the Amazon. The estimate considers the following range between the minimum and maximum levels of each element in the grass: (in mg/kg DM) 43.07–349.83 for Fe, 11.43–27.99 for Zn, and 2.77–7.57 for Cu; (in μg/kg DM) 0.79–145.94 for Se and 4.19–29.51 for Co. Estimated intakes for all elements and combinations of grass and nutritional supplements are provided in Tables S5–S7.

6

Descriptive statistics of trace elements in the blood plasma of herds I to IV, VIa, and VIb from farms located in the southern region of the Amazon. No reference ranges were available for Ni, Cr, Pb, As, Cd, and Hg.

7

Descriptive statistics of trace elements in the muscle, kidney, and liver (wet weight) obtained in markets located in the southern region of the Amazon. The minimum, 10th, 25th, 50th, 75th, 90th, and maximum percentiles of elements in meat products are shown in Tables S7–S9.

8

Estimate of relative monthly intake (RMI) to the reference daily intake adjusted to 30 days (RDI_30d) for human categories by consumption of the muscle, kidney, and liver of cattle obtained in markets located in the southern region of the Amazon. The following ages and body weights were assumed for the different human categories: 6 years and 20 kg for children; 16 years and 53 kg for girls; 16 years and 58 kg for boys; 30 years and 65 kg for women; and 30 years and 80 kg for men. Element contents in the meat products in this figure were the range between the 10th and 90th percentiles of the descriptive results of the muscle, kidney, and liver (Tables S8–S10).

9

Estimate of relative monthly intake (RMI) in relation to the tolerable upper levels adjusted to 30 days (UL_30d) for human categories by consumption of the muscle, kidney, and liver of cattle obtained in markets located in the southern region of the Amazon. The following ages and body weights were assumed for human categories: 6 years and 20 kg for children; 16 years and 53 kg for girls; 16 years and 58 kg for boys; 30 years and 65 kg for women; and 30 years and 80 kg for men. Element concentrations in the meat products in this figure were the range between the 10th and 90th percentile of the descriptive results for the muscle, kidney, and liver (Tables S8–S10).