This review highlights the similarities between pigs and humans and thereby the value of the porcine human nutritional model, and reviews some of the more recent applications of this model for nutritional research.

The Pig as an Experimental Model for Elucidating the Mechanisms Governing Dietary Influence on Mineral Absorption

Dietary means to better control the environmental impact of copper and zinc by pigs from weaning to slaughter

One hundred twenty crossbred piglets (Duroc × Landrace × Yorkshire) were used to determine the effects of dietary zinc glycine chelate on growth performance, tissue mineral concentrations, and serum enzyme activity. All pigs were allotted to four treatments and fed with basal diets supplemented with 0, 50, and 100 mg/kg Zn as zinc glycine chelate or 3,000 mg/kg Zn as zinc oxide (ZnO). After the 35-day feeding trial, results of the study showed that, compared to the control, average daily gain was improved (P < 0.05) for pigs fed 100 mg/kg Zn from zinc glycine chelate or 3,000 mg/kg Zn from ZnO and Zn concentrations in serum and M. longissimus dorsi were significantly enhanced by 100 mg/kg dietary zinc glycine chelate and 3,000 mg/kg ZnO. In addition, supplementation of 100 mg/kg zinc glycine chelate decreased (P < 0.05) the liver Fe level, liver Zn level, spleen Cu level, and kidney Cu level compared to that of the 3,000-mg/kg ZnO group. For feces mineral excretion, 3,000 mg/kg Zn from ZnO greatly increased the concentration of fecal Zn (P < 0.01) and Mn (P < 0.05) compared to that of the control or the 100-mg/kg zinc glycine chelate group. Moreover, alkaline phosphatase and Cu/Zn superoxide dismutase activities of pigs in 100 mg/kg zinc glycine chelate and ZnO treatments were greatly higher than that of the control. The results of present study showed that supplementation with zinc glycine chelate could improve growth and serum enzyme activities and could also decrease zinc excretion in feces in weanling pig compared to high dietary ZnO.

Dietary Zinc Glycine Chelate on Growth Performance, Tissue Mineral Concentrations, and Serum Enzyme Activity in Weanling Piglets

Effect of zinc supplemented as either an organic or an inorganic source and of microbial phytase on zinc and other minerals utilisation by weanling pigs

This study was conducted to determine the effect of zinc level and source on growth performance, tissue Zn concentrations, intracellular distribution of Zn, and immune response in weanling pigs. Ninety-six 3-wk-old crossbred weanling pigs (BW = 6.45 +/- 0.17 kg) were assigned to one of six dietary treatments (four pigs per pen, four replicates per treatment) based on weight and litter origin. Treatments consisted of the following: 1) a corn-soybean meal-whey diet (1.2% lysine) with a basal level of 80 ppm of supplemental Zn from ZnSO4 (control; contained 104 ppm total Zn); 2) control + 80 ppm added Zn from ZnSO4; 3) control + 80 ppm added Zn from Zn methionine (ZnMet); 4) control + 80 ppm added Zn from Zn lysine (ZnLys); 5) control + 40 ppm added Zn from ZnMet and 40 ppm added Zn from ZnLys (ZnML); and 6) control + 160 ppm added Zn from ZnSO4. Zinc supplementation of the control diet had no effect on ADG or ADFI. Gain efficiency was less (P < 0.05) for pigs fed 80 ppm of Zn from ZnSO4 than for control pigs and pigs fed 160 ppm of Zn from ZnSO4. Organ weights, Zn concentration, and intracellular distribution of Zn in the liver, pancreas, and spleen were not affected (P = 0.12) by Zn level or source. Skin thickness response to phytohemagglutinin (PHA) was not affected (P = 0.53) by dietary treatment. Lymphocyte proliferation in response to PHA was greater (P < 0.05) in pigs fed ZnLys than in pigs fed the control diet or the ZnML diet; however, when pokeweed mitogen was used, lymphocyte proliferation was greatest (P < 0.05) in pigs fed the ZnMet diet than pigs fed the control, ZnLys, ZnML, or 160 ppm ZnSO4 diets. Antibody response to sheep red blood cells was not affected by dietary treatments. Supplementation of 80 ppm of Zn from ZnSO4 or ZnMet and 160 ppm of Zn from ZnSO4 decreased (P < 0.05) the antibody response to ovalbumin on d 7 compared with control pigs, but not on d 14. Phagocytic capability of peritoneal exudate cells was increased (P < 0.05) when 160 ppm of Zn from ZnSO4 was supplemented to the diet. The number of red blood cells ingested per phagocytic cell was increased (P < 0.05) in pigs fed the diet supplemented with a combination of ZnMet and ZnLys and the diet with 160 ppm of Zn from ZnSO4. Results suggest that the level of Zn recommended by NRC for weanling pigs was sufficient for optimal growth performance and immune responses, although macrophage function may be enhanced at greater levels of Zn. Source of Zn did not alter these measurements.

Effects of organic forms of zinc on growth performance, tissue zinc distribution, and immune response of weanling pigs.

We conducted two trials (n = 144 and 96) to evaluate the response of feeding either ZnSO4 x H2O or a zinc-lysine complex (ZnLys) in combination with various lysine levels on growth performance, liver, kidney, and 10th rib Zn concentration, serum Zn humoral immune response and absorption of Zn (chromic oxide method) of young pigs. The following treatments were started after a 7-d postweaning adjustment during which all pigs were fed a common diet adequate in zinc. Diets were as follows: 1) basal 1 (B1), .8% dietary lysine without added Zn (basal contained 32 ppm Zn); 2) B1 plus 100 ppm Zn from ZnSO4; 3) B1 plus 100 ppm Zn from ZnLys, 4) basal 2 (B2), 1.1% lysine without added Zn; 5) B2 plus 100 ppm Zn from ZnSO4; 6) B2 plus 100 ppm Zn from ZnLys. In Trial 1 only, 100 ppm Zn from ZnSO4 (diet 7) or ZnLys (diet 8) was added to a .95% lysine basal diet. The basal 20% CP diet contained 9.0% corn gluten meal to lower the total lysine level. Within lysine level, all diets were made isolysinic by using crystalline lysine. Zinc sulfate, ZnLys, or lysine replaced dextrose in the basal diet. After 4 wk on test, one barrow in each pen was killed; liver, kidney, left 10th rib, and contents of the stomach, small intestine, and lower colon were removed for Zn analyses. Performance (ADG and ADFI) was only improved (P .20) by lysine level, or Zn level and source. Pigs fed diets without added Zn had lower (P < .001) liver, kidney, and rib Zn concentrations than pigs fed diets with added Zn regardless of Zn source. Dietary lysine did not influence liver Zn, but kidney (P < .01) and rib (P < .001) Zn concentrations were lower for pigs fed the higher lysine level. Digestibility coefficients of Zn were lower in the stomach for pigs fed diets without added Zn, similar among Zn levels and sources in the small intestine, and higher in the lower colon for pigs fed the basal diets without added Zn. Lysine level and Zn source did not influence Zn absorption. The ZnSO4 and a zinc lysine complex seemed to be equally effective in promoting growth performance, zinc absorption, and tissue stores of young pigs when diets contained deficient, adequate, or slightly more than adequate levels of lysine.

J Cheng

Papers

Influence of dietary lysine on the utilization of zinc from zinc sulfate and a zinc-lysine complex by young pigs.