Animals : an Open Access Journal from MDPI · 9 authors, 6 centres
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This study evaluated the mineral content of liver from buffaloes raised in different ecosystems (native pasture, cultivated pasture, and confinement) in the Eastern Amazon. The ecosystem significantly influenced levels of sodium, potassium, calcium, magnesium, sulfur, copper, iron, manganese, and barium in the liver. Buffalo liver is an excellent source of minerals and can meet human dietary recommendations regardless of the rearing ecosystem.
**Background:** Water buffaloes are increasingly valued for their productivity and the nutritional quality of their meat and organs. The liver is a rich source of minerals essential for human health, including macrominerals (calcium, phosphorus, magnesium, potassium, sodium, sulfur) and microminerals (iron, copper, zinc, manganese). In the Eastern Amazon, buffaloes are raised in diverse ecosystems—native flooded pastures (Marajó, Lower Amazon), cultivated dryland pastures, and confinement systems. The mineral composition of forage varies with soil, climate, and season, potentially affecting the mineral content of animal tissues. This study aimed to evaluate how different production ecosystems and seasons influence the mineral profile of buffalo liver.
**Methods:** Liver samples were collected from 84 crossbred Murrah/Mediterranean male buffaloes (12 per ecosystem) slaughtered in commercial slaughterhouses. Four ecosystems were studied: Marajó (native flooded pasture, Am climate, 2500 mm annual rainfall), Lower Amazon (native pasture, 2000 mm annual rainfall), Cultivated Pasture (cultivated dryland pasture, 2467 mm annual rainfall), and Confinement (intensive system, 192-day feeding period). For extensive systems, samples were collected at the end of the dry season and the end of the rainy season. Approximately 5 g of liver was collected, frozen at −80°C, lyophilized, and analyzed for mineral content using inductively coupled plasma optical emission spectrometry (ICP-OES). Statistical analysis used PROC MIXED in SAS with a 3 × 2 + 1 factorial model, with Tukey–Kramer test for post-hoc comparisons at p < 0.05.
**Key Results:** The ecosystem significantly influenced (p < 0.05) liver concentrations of Na, K, Ca, Mg, S, Cu, Fe, Mn, and Ba. Sodium was highest in Marajó buffaloes (dry: 3111.65 mg/kg; rainy: 3497.28 mg/kg) and lowest in Cultivated Pasture (dry: 2262.74 mg/kg). Potassium ranged from 10,454.0 mg/kg (Lower Amazon, dry) to 12,051.0 mg/kg (Cultivated Pasture, dry). Calcium was significantly lower in Cultivated Pasture (476.13–477.98 mg/kg) compared to other ecosystems (672.50–747.44 mg/kg). Magnesium was highest in Lower Amazon rainy season (731.72 mg/kg) and lowest in Cultivated Pasture rainy season (617.52 mg/kg). Copper showed extreme variation: Cultivated Pasture rainy season had 93,784 mg/kg, while Marajó had 6168.3–6235.0 mg/kg and Lower Amazon had 18,816.0–69,505.8 mg/kg. Iron was highest in Marajó (rainy: 1381.29 mg/kg; dry: 1266.30 mg/kg) and lowest in Lower Amazon (dry: 507.62 mg/kg; rainy: 435.94 mg/kg). Manganese was highest in Marajó (dry: 15.86 mg/kg; rainy: 14.86 mg/kg) and lowest in confinement (9.71 mg/kg). Barium was highest in Cultivated Pasture rainy season (6.32 mg/kg) and lowest in confinement (1.42 mg/kg). The extensive vs. intensive comparison showed significant differences for K, Cu, Fe, Mn, and Ba. Season affected Na, K, S, and Cu. Location × season interaction was significant for K, Mg, P, S, and Cu. Zinc did not differ significantly across ecosystems (p = 0.0652). No significant effects were found for Cr, Ni, As, Li, Pb, Co, Sn, V, or Cd, all of which were present at very low levels (<2.0 mg/kg for Cr and Ni, <1.5 mg/kg for As and Li, <1.0 mg/kg for Pb, Co, Sn, V, and <0.05 mg/kg for Cd).
**Clinical Implications:** Buffalo liver from all studied ecosystems meets or exceeds daily human dietary recommendations for essential minerals. The daily recommendation for iron (14 mg for adults) is easily met by a standard serving of buffalo liver, particularly from Marajó-raised animals (up to 1381.29 mg/kg). Copper levels (0.9 mg daily recommendation) are far exceeded in all ecosystems. Zinc recommendations (7 mg daily) are met by all samples (94.06–116.44 mg/kg). Manganese (2.3 mg daily) is adequately supplied. The Marajó ecosystem produced liver with the highest overall mineral content, likely due to the diverse native forage species (Panicum elephantipes, Leersia hexandra, Hymenachne amplexicaulis) and brackish water. However, the extremely high copper levels in Cultivated Pasture (93,784 mg/kg in rainy season) warrant attention, as excessive copper intake can be toxic. The low levels of toxic heavy metals (Pb, Cd, As) confirm the safety of buffalo liver for human consumption. These findings support buffalo liver as a nutrient-dense food that can contribute to meeting mineral requirements, particularly in regions where mineral deficiencies are common.