Abstract
Although chromium (Cr) feeding study results have been variable, our hypothesis was feeding a regimen that changed dosage over time would result in a larger positive response in growth performance and carcass characteristics. In Exp. 1, a total of 1,206 pigs (PIC 337 × 1050, initial BW 28.7 kg) were used with 27 pigs per pen and 9 pens per treatment. Diets were corn-soybean meal-dried distillers grains with solubles based and were fed in a five-phase feeding program. Treatments were arranged as a 2 × 2 + 1 factorial with a control diet containing no added Cr propionate (Kemin Industries Inc., Des Moines, IA), or diets with either 100 or 200 µg/kg added Cr during the grower (dietary phases 1 and 2) and/or finisher (dietary phases 3, 4, and 5) periods. During the grower period, ADG and G:F were similar among pigs fed the control or 100 µg/kg added Cr diets, but decreased in pigs fed 200 µg/kg Cr (quadratic, P ≤ 0.001). During the finisher period, pigs supplemented with 200 µg/kg added Cr had the greatest ADG and G:F (quadratic, P ≤ 0.019). Overall, increasing Cr had no effect on ADG or ADFI; but G:F was greatest (quadratic, P = 0.020) when pigs were fed 100 µg/kg of added Cr throughout. Carcass characteristics were not influenced by Cr dosage or feeding regimen. In Exp. 2, a total of 1,206 pigs (PIC 359 × 1050, initial BW 48.9 kg) were used with 27 pigs per pen and 15 pens per treatment. Diets were corn-soybean meal, dried distillers grains with solubles based and were fed in four phases. There were three dietary treatments: a diet with no added Cr for both grower (dietary phase 1 and 2) and finisher (dietary phase 3 and 4) periods, a diet with 200 µg/kg added Cr during the grower and 100 µg/kg added Cr during the finisher periods, or a diet with 200 µg/kg added Cr for both periods. Addition of 200 µg/kg Cr in both periods marginally increased (P < 0.10) ADG compared with pigs fed no added Cr. There was no evidence (P ≥ 0.523) of added Cr influencing overall ADFI and G:F. Percentage carcass yield was reduced (P = 0.018) when Cr was added at 200 µg/kg for both periods, with no evidence of differences (P ≥ 0.206) in other carcass characteristics. In summary, overall G:F was improved in Exp. 1, and ADG in Exp. 2, by added Cr, but there was no evidence that different feeding regimens will consistently result in improved performance. However, these data are consistent with the literature in that added Cr in growing-finishing pigs diets improves, albeit small, ADG or G:F.