The relationship between zinc intake, dietary content, and fecal excretion in pigs

Excessive dietary Zn is excreted through feces in pigs. Spreading pig slurry containing high Zn concentrations to fields leads to increased risk of antibiotic resistance gene development in soil bacteria and has a negative impact on soil fertility. Data from 10 published studies with weaned pigs during the first 6 wks post-weaning (PW) was included in a meta-regression analysis to develop a model for the relationship between daily Zn intake and daily Zn excretion. The Zn excretion increased linearly with the Zn intake (P < 0.01), and the formulation of added Zn (source of Zn) had no influence on the Zn excretion (P > 0.60). To estimate the daily Zn intake at 150, 1,400, or 2,500 ppm Zn in the diet during the first 2 wks PW, a model was developed using our own experimental data from 179 weaned pigs individually fed one of six dietary Zn concentrations. By combining the two models, the daily Zn excretion was calculated for the first 2 wks PW at 150, 1,400, or 2,500 ppm dietary Zn. At 2,500 ppm dietary Zn, the daily Zn excretion was calculated to be 7.5 g/pig, while 150 or 1,400 ppm reduced the daily Zn excretion by 94 and 36%, respectively. The effect of reducing the dietary Zn content during the first 2 wks PW was put in perspective by applying an updated published model to calculate the Zn excretion from weaning to slaughter in 3 scenarios for dietary Zn content. The total Zn excretion was calculated to be 31.0 g/pig if supplying 6-to 9-, 9-to 28-, and 28-to 108-kg pigs with 2,500, 150, and 100 ppm dietary Zn, respectively. Of the total Zn excretion, 59% were accounted by 28-to 108-kg pigs. The calculated total Zn excretion was reduced by 49% if the dietary Zn concentrations were reduced to 1,400, 100, and 50 ppm for 6-to 9-, 9-to 28-, and 28-to 108-kg pigs, respectively. In contrast, if only reducing the dietary Zn content for 6-to 9-kg pigs from 2,500 to 150 ppm, the total calculated Zn excretion was reduced by 26%. In conclusion, pigs' Zn excretion can be reduced sub-stantially if the dietary Zn content is adjusted for all weight categories but the largest reduction can be achieved if the dietary Zn content for 28-to 108-kg pigs is reduced from 100 to 50 ppm.

Automated summary

Excessive dietary Zn in pigs leads to increased risk of antibiotic resistance gene development in soil bacteria and has a negative impact on soil fertility when pig slurry is spread to fields. A meta-regression analysis was conducted using data from 10 published studies to develop a model for the relationship between daily Zn intake and daily Zn excretion in weaned pigs. The results showed that Zn excretion increased linearly with Zn intake, and the formulation of added Zn had no influence on Zn excretion.