Effects of dietary zinc oxide levels on the metabolism of zinc and copper in weaned pigs

Abstract

This study compared different dietary zinc oxide (ZnO) levels on zinc (Zn) and copper (Cu) metabolism in weaned pigs. One hundred twenty weaned piglets (7.96 ± 1.17 kg; 21 d of age) were used in a completely randomized 3 × 4 factorial design composed with three levels of dietary ZnO at 100 (100Zn), 1,000 (1,000Zn), or 3,000 mg/kg (3,000Zn) and four ages at slaughter at 21 (day 21), 23 (day 23), 35 (day 35), and 42 d (day 42). Dietary Cu levels were constant at 130 mg/kg. Serum, jejunum, liver, and kidney levels of Zn and Cu as well as mRNA abundance of genes related to Zn and Cu metabolism were analyzed. Zinc levels were greatest in 3,000Zn piglets from day 35 in all tissues (P ≤ 0.01). In 3,000Zn piglets, mRNA expression of ZIP4 was reduced in jejunum whereas ZnT1 and MT3 were stimulated in jejunum and liver and MT1 in kidney (P ≤ 0.04) from day 35. Copper levels were greatest in jejunum (P = 0.06) and kidney (P ≤ 0.01; days 35 and 42 only) and lowest in liver and serum (P ≤ 0.01) of 3,000Zn piglets. In conclusion, the treatment containing 3,000 mg ZnO/kg triggered Zn homeostatic mechanisms in weaned pigs and impaired Cu metabolism through high enterocyte and kidney Cu sequestration.

Keywords: copper; metabolism; pig; supranutritional levels; zinc.

Figure 1.

Serum zinc (A) and serum copper (B) concentrations (mg/L) according to dietary treatments and age at slaughter, presented as LS means ± SEM. For both parameters, treatment × age interaction (P < 0.01) was detected. Zinc values were greatest for 3,000Zn, intermediary for 1,000Zn, and lowest for 100Zn on days 35 and 42. Copper values were lowest for 3,000Zn and were not different between 1,000Zn and 100Zn on days 35 and 42.

Figure 2.

Zinc concentrations in jejunum (µg/g protein) (A), liver (µg/g) (B), and kidney (µg/g protein) (C) according to dietary treatments and slaughter day, presented as LS means ± SEM. For all studied tissues, treatment × age interaction (P < 0.01) was detected. In jejunum and kidney, values were greatest for 3,000Zn and did not differ between 1,000Zn and 100Zn on days 35 and 42. In liver, values were greatest for 3,000Zn, intermediary for 1,000Zn, and lowest for 100Zn on days 35 and 42.

Figure 3.

Copper concentrations in jejunum (µg/g protein) (A), liver (µg/g) (B), and kidney (µg/g protein) (C) according to treatments and slaughter day, presented as LS means ± SEM. For jejunum and liver, there was a dietary treatment effect (P ≤ 0.06) but no treatment × age interaction (P ≥ 0.15). For kidney, treatment × age interaction (P < 0.01) was detected. Values were highest for 3,000Zn, intermediary for 1,000Zn, and lowest for 100Zn at days 35 and 42.