Dietary copper affects small intestine physiology in weanling pigs

Thirty weanling, crossbred barrows were used to determine the effects of amount and source of dietary Cu on small intestinal morphology and lipid peroxidation, Cu metabolism, and mRNA expression of proteins involved in hepatic Cu homeostasis. At 21 d of age, pigs were stratified by BW (6.33 ± 0.23 kg) and allocated to 1 of the following dietary treatments: i) control (no supplemental Cu; 6.7 mg Cu/kg), ii) 225 mg supplemental Cu/kg diet as Cu sulfate (CuSO₄), or iii) 225 mg supplemental Cu/kg diet as tribasic Cu chloride (TBCC). Pigs were housed 2 pigs per pen and were fed a 3-phase diet regimen until d 35 or 36 of the study. During harvest, bile and liver were obtained for mineral analysis, and liver samples were also obtained for analysis of liver glutathione (GSH) and mRNA expression of Cu regulatory proteins. Segments of duodenum, proximal jejunum, and ileum were obtained for mucosal morphology, and duodenal mucosal scrapings were collected from all pigs for analysis of malondialdehyde (MDA).

Duodenal villus height was reduced in CuSO₄ (338 µm) pigs compared with control (486 µm; P = 0.001) and TBCC (424 µm; P = 0.03) pigs. Villus height in the proximal jejunum of CuSO₄ pigs was reduced (408 µm; P = 0.03) compared with control pigs (509 µm), but ileal villus height was not affected (P = 0.82) by treatment. Duodenal MDA concentrations were higher (P = 0.03) in CuSO4 (0.57 µM/mg protein) pigs and tended to be higher (P = 0.10) in pigs supplemented with TBCC (0.49 µM/mg protein) compared with control pigs (0.33 µM/mg protein). Liver Cu was increased (P = 0.01) in CuSO₄ (268.2 mg/kg DM) vs. control pigs (34.9 mg/kg DM), and tended (P = 0.07) to be higher in TBCC pigs (188.6 mg/kg DM) than control pigs. Bile Cu concentrations were greater (P < 0.05) in CuSO₄ and TBCC pigs vs. controls (3.21 vs. 4.24 vs. 0.65 mg/l, respectively). Total liver GSH concentrations were reduced (P = 0.02) in pigs fed diets supplemented with CuSO4 (5.688 pmole/well) vs. pigs fed control (6.722 pmole/well) diets but total liver GSH did not differ (P = 0.11) between control and TBCC pigs (6.034 pmole/well). Hepatic mRNA of cytochrome c oxidase assembly protein 17 was lower (P = 0.01) in CuSO₄ (0.81) and tended to be reduced (P = 0.08) in TBCC pigs (0.90) vs. control pigs (1.07). Expression of antioxidant 1 mRNA was greater (P = 0.04) in TBCC pigs (1.86) and tended to be greater (P = 0.06) in CuSO₄ pigs (1.78) compared with control pigs (0.90).

Results of this study indicated that, when fed at 225 mg Cu/kg diet, TBCC may cause less oxidative stress in the duodenum than CuSO₄. Feeding weanling pigs increased Cu resulted in modulation of certain Cu transporters and chaperones at the transcription level.

RS Fry, MS Ashwell, KE Lloyd, AT O’Nan, WL Flowers, KR Stewart, JW Spears. 2012. Amount and source of dietary copper affects small intestine morphology, duodenal lipid peroxidation, hepatic oxidative stress, and mRNA expression of hepatic copper regulatory proteins in weanling pigs. Journal of Animal Science, 90:3112-3119. doi:10.2527/jas2011-4403.