Rats Allowed to Self-Select Zinc-Deficient Lard and Fish-Oil Diets Did Not Develop a Preference for Fish-Oil Diet

Abstract

Summary Zinc (Zn)-deficiency causes a reduction in food intake and alters adipose metabolism. The effect of zinc restriction in rats on the selection of fish-oil and lard was studied during a period of reduced appetite. The reduction of appetite was caused by an experimentally induced Zn-deficiency. Four-week-old male rats were divided into three dietary treatment groups: Zn-adequate (ZnA, 30.9 mg Zn/kg), marginal Zn-deficient (ZnM, 5.9 mg Zn/kg) or Zn-deficient (ZnD, 0.9 mg Zn/kg). The three groups were placed on a self-selection regimen of the ZnA-fish-oil diet (ZnA-FD) and the ZnA-lard diet (ZnA-LD), the ZnM-FD and the ZnM-LD or the ZnD-FD and the ZnD-LD, respectively for 24 d. The amount of the FD intake in the ZnD group decreased to 0.5 g/d after day 4-6 of self-selecting on the LD and the FD and no significant increase in the FD intake in the group was observed during the self-selection period. However, after day 7-9 and 13-15, the FD intake of the ZnA and the ZnM groups increased, respectively, and at the end of the self-selection period the ZnM and the ZnA rats consumed about 2.0 g FD/d and 4.5 g FD/d, respectively. The FD intake ratio [FD intake (g)/total intake (g)] in the ZnD rats during the self-selection period was the lowest and that in the ZnA rats was the highest of three groups. In conclusion, we showed that zinc status alters fish-oil and lard selection patterns and ZnD rats did not show a preference for fish-oil.

A Moderate Zinc Deficiency Does Not Alter Lipid and Fatty Acid Composition in the Liver of Weanling Rats Fed Diets Rich in Cocoa Butter or Safflower Oil

“…The two-thirds higher TAG levels in the liver of the rats given free access to the HZ-SF diet than those of the animals fed this diet in restricted amounts or freely fed the LZ-SF diet may be attributed to the higher energy intake in the HZ-SF group. This notion is consistent with former studies showing that hepatic TAG concentrations in Zn-deficient rats were lower than in control animals given free access to Zn-adequate diets [12–15, 23] but comparable to TAG levels in restrictedly fed control animals [15, 27, 28]. In contrast, research in which young rats were fed by gastric tube in order to equalize and synchronize food intake consistently found that Zn depletion caused greatly increased liver TAG concentrations compared to levels of control animals [8–11], unless diets contained oils rich in n-3 PUFAs [26].…”

“…Such a difference in Zn concentration can be expected to affect the growth response. However, other studies also suggest that Zn-deficient diets rich in PUFA may worsen appetite, growth, and Zn status of young rats [15, 23, 24] and chicks [25]. …”