Dietary Zinc Supplementation to Prevent Chronic Copper Poisoning in Sheep.

Antonio Minervino,Francisco Oliveira,Carolina Araújo,Alexandre Antonelli,Marta López-Alonso,Clara Mori,Rejane Sousa,Marta Miranda,Frederico Rodrigues,Enrico Ortolani,Raimundo Barrêto Júnior

doi:10.3390/ani8120227

Abstract

Simple SummarySheep are susceptible to copper toxicosis, a deadly disease that usually occurs when the animals ingest large amounts of this mineral. Considering that the susceptibility of sheep to copper accumulation varies widely among breeds and from animal to animal., we evaluate whether Zn supplementation could be an option as a preventive measure to protect against hepatic Cu accumulation in sheep. Zn at 300 mg/kg dry matter (DM) is useful for preventing excessive hepatic Cu accumulation. Hepatic Cu accumulation is lower in animals receiving the Zn supplementation.The aim of this study was to evaluate whether zinc (Zn) supplementation protects against hepatic copper (Cu) accumulation in copper-loaded sheep. Forty cross-bred lambs were assigned to five experimental groups. These included the control group (C) and four treatment groups that received Cu and/or Zn supplementation (dry matter (DM) basis) over 14 weeks, as follows: Cu (450 mg Cu/kg); Zn-35 (450 mg Cu + 35 mg Zn/kg); Zn-150 (450 mg Cu + 150 mg Zn/kg); and Zn-300 (450 mg Cu + 300 mg Zn/kg). Blood, liver, and bile samples were obtained for mineral determination by inductively coupled plasma optical emission spectrometry (ICP–OES). The hepatic metallothionein (MT) concentrations were also determined. At the end of the experiment, hepatic Cu concentrations were higher in all Cu-supplemented groups than in C. Hepatic Cu accumulation was lower in the groups receiving the Zn supplementation than in the Cu group, although the difference was only statistically significant (66%) in the Zn-300 group. The MT concentrations tended to be higher (almost two-fold) in the Zn groups (but were not dose related) than in the C and Cu groups, and they were related to hepatic Zn concentrations. Zn supplementation at 300 mg/kg DM is useful for preventing excessive hepatic Cu accumulation in sheep exposed to high dietary concentrations of Cu.

Highlights

Chronic copper poisoning (CCP) is a severe disease in sheep, causing the death of animals and economic losses worldwide [1,2]
Considering a sheep weighting 40 kg, the basal diet produced an intake of 12.8 mg Cu and 84.6 mg Zn per day
The final supernatant fraction was analyzed for Cd by inductively coupled plasma optical emission spectrometry (ICP–OES), and the MT concentrations were calculated by assuming a Cd/MT molar ratio of 17

Summary

Introduction

Chronic copper poisoning (CCP) is a severe disease in sheep, causing the death of animals and economic losses worldwide [1,2]. Secondary CCP is very common and appears to be associated with interactions in the gut with other essential trace elements such as sulphur (S), molybdenum (Mo), and iron (Fe) when these are not balanced in the diet [11,12]. Sheep appear to be very sensitive to CCP as, unlike most other species, they have a very limited capacity to excrete biliary Cu, as a result of a low capacity to accumulate Cu bound to metallothioneins (MT) in the liver. When Cu is absorbed from the intestine, it enters the liver, where it is utilized in normal hepatocyte metabolism; stored bound to MT; and, if the Cu balance is positive, excreted into the bile [13]. Metallothioneins appear to play a central role in Cu excretion into the bile, where Cu–MT is sequestered by the lysosomes for excretion [14]. If there is a large influx of Cu into the liver, the binding capacity of the MT and the removal of Cu–MT from the cytosol by lysosomes may be surpassed [13]

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