Growth of Zinc-Deficient Rats During Intra-Gastric Tube Feeding

This study aimed to examine the reasons for the lack of growth in rats fed a zinc-deficient (ZnD) diet via gastric tube. Four days after rats were given free access to the ZnD diet (0.3 mg/kg Zn), their food intake had decreased, and their growth had stopped. Rats were then fed via gastric tube; growth was restored in rats fed a control diet (25 mg/kg Zn; restored group) but not in those fed the ZnD diet (ZnD group). In the ZnD group, there was no reduction in the apparent absorption of dry matter, protein, or ash during 3 days of tube feeding. Dry matter in urine was markedly higher on day 3 and mainly consisted of glucose. Urinary nitrogen was also elevated in the ZnD group, but nitrogen balance remained positive; i.e., bodily protein continued to increase during the 3 days of tube feeding. Drinking water consumption in the ZnD group was markedly reduced from the second day of tube feeding. On the other hand, urine volume in the ZnD group was comparable to that in the restored group. Water content in the bodies of the ZnD group was reduced. These observations demonstrate that the ZnD group was dehydrated. In conclusion, rats fed a ZnD diet via gastric tube did not grow because their drinking water consumption decreased with progression of zinc deficiency, thereby, decreasing bodily water content. Administration of water led to growth in the ZnD group.