Prediction model for manure zinc excretion in laying hens

The objective of this research trial was to compare 2 sources of zinc and different levels of supplementation on manure zinc excretion in laying hens. Bovan White Leghorn hens were used in this study and fed one of 6 dietary treatments. Treatments were in a 2 × 3 factorial arrangement with 2 sources of zinc (zinc sulfate or Availa®Zn) and 3 levels (40, 80, or 120 ppm) and were randomly assigned to 48 cages with 5 hens/cage and 8 replicates/treatment. Hens were housed in a tiered manure-belt housing system providing 627.1 cm2/hen and were given access to 110 g/hen/d of feed. Manure samples were collected, and manure zinc content was calculated at 10-week intervals. Data were analyzed using the Glimmix procedure in SAS. There was a significant overall effect of source (P < 0.0001) for zinc content, such that hens fed zinc sulfate had lower amounts of zinc excretion. There was also a significant level effect (P < 0.0001) in which hens fed 120 ppm zinc excreted the greatest amount of zinc. A significant source by level interaction was observed (P < 0.0001) for both the overall and individual analyses, such that 120 ppm Availa®Zn showed the highest zinc excretion, and both 40 ppm zinc sulfate and Availa®Zn showed the lowest zinc excretion. Based on these results, a prediction equation was written for an estimated amount of zinc excretion based on the amount of zinc provided in the diet.