Zinc requirements for grow-finish pigs published by the National Research Council (NRC) in 2012 are based on data published many years ago and, as such, likely are not suitable for today’s swine genetics and dietary ingredients.

Because 60 to 75% of the phosphorus in corn and soybean meal is estimated to be bound to phytate, it is not readily available to the pig without phytase supplementation. A few studies suggest that phytase supplementation increases not only phosphorus availability to the pig, but also zinc.

Most finishing diets include phytase, with Paylean (Elanco Animal Health) added in the last phase prior to market.

In recent work at The Ohio State University and Michigan State University, pigs supplemented with 25 ppm organic zinc (Bioplex) gained at the same rate as pigs fed 100% of all NRC (1998) trace mineral requirements (2.37 vs. 2.35 lb./day) from approximately 53 lb. to 260 lb.

The analyzed trace mineral content of the selenium-supplemented diet in the three phases prior to treatment supplementation was: 6, 9 and 6 ppm copper; 200, 203 and 186 ppm iron; 20, 34 and 18 ppm manganese; 0.8, 0.75 and 0.75 selenium; and 35, 59 and 36 ppm zinc.

By calculation, the NRC (1998) requirements were met in the non-supplemented diets except for zinc in phases 1 and 3.

Numerically, for the entire study, pigs fed the diet supplemented with 100% of the NRC requirements (1998) consumed more feed per day (5.9 lb.) than pigs fed the diet supplemented with only 25 ppm organic zinc (5.5 lb.). This resulted in a gain:feed ratio of 0.43 for pigs supplemented with 25 ppm organic zinc. This compared to pigs fed 100% of the NRC requirements (1998) with a gain:feed ratio of 0.40.

These results indicate that today’s fast-growing, lean pigs fed corn and soybean meal diets need only 25 ppm organic zinc added to finisher diets that are supplemented with phytase.

Researchers: G.M. Hill and D.W. Gowanlock, Michigan State University and D.C. Mahan, The Ohio State University. For more information, contact Hill by phone (517) 355-9676 or e-mail hillgre@msu/edu.