Dietary contribution of iron from limestone and dicalcium phosphate for broiler chickens

Iron is routinely supplemented in broiler feeds aiming to prevent dietary deficiencies. Limestone and phosphates are very rich in Fe; however, its contribution from these sources have not been thoroughly investigated with chickens. The present research was conducted to evaluate live performance and blood parameters of broilers when using limestone and dicalcium phosphate as sources of Fe. A total of 576 one-day-old male Cobb x Cobb 500 were allocated into a total of 72 battery cages, 6 treatments with 12 replication cages of 8 chicks at placement. Chicks were fed diets formulated with corn, soybean meal (SBM) with laboratory grade calcium carbonate and phosphoric acid (having traces of Fe). All chicks were fed a common prestarter without Fe supplementation (analyzed total 58.2 ± 2.4 mg/kg Fe) from placement to 7 d. Allocation of birds to dietary treatments was completely randomized on day 8. Treatments had increasing Fe derived from commercial limestone and dicalcium phosphate (analyzed Fe 7,218 and 4,783 mg/kg, respectively) progressively replacing calcium carbonate and phosphoric acid to provide graded increases in total Fe (analyzed Fe in the feeds were 57.6 ± 2.1, 92.0 ± 2.3, 124.1 ± 2.7, 159.3 ± 3.1, 187.2 ± 3.2, 223.7 ± 3.6 mg/kg, respectively). There were no effects of dietary Fe on live performance, hematocrit, and hemoglobin the end of the study on day 28 (P > 0.05). Increasing dietary Fe from commercial limestone and dicalcium phosphate led to a linear reduction in the percent ileal digestible Fe. However, linear increments in Fe retention, serum ferritin and liver Fe occurred when compared to feeds without Fe derived from limestone and phosphate dicalcium. It is concluded that Fe from limestone and dicalcium phosphate can be partially utilized by broiler chickens. It was estimated that the Fe retained from limestone and dicalcium phosphate is of 1.9%. Broilers fed corn-soy feeds (58.2 mg/kg Fe) do not require supplemental Fe.

Dietary phytase effects on copper requirements of broilers

Information on the availability of Cu from plant feedstuffs for broilers in the presence of phytase is scarce. The present research has been conducted with the objective of evaluating the Cu requirements of broilers when fed corn-soy diets with or without phytase. A total of 640 one-day-old male Cobb x Cobb 500, allocated into 80 battery cages with 8 chicks in each, were fed a low Cu content diet (formulated with 8.58 ± 0.21 mg/kg Cu) without phytase from placement to day 7. Starting on day 8, battery cages were distributed into a 2 × 5 factorial arrangement (phytase-added diets X 5 with graded increases of supplemental Cu) until day 28. Feeding treatments (feeds added or not with phytase and 5 graded increases of Cu) were randomly distributed with 8 cages of 8 chicks. The basal non-supplemented feeds were formulated with corn and soybean meal (SBM) without any other significant Cu contributors. Supplemental Cu was from laboratory-grade Cu sulfate pentahydrate (CuSO5H20) which was increasingly added to the feeds. Phytase was added in excess to the producer recommendation (2,500 FYT) and had average analyzed values of 2,768 ± 135.2 FYT/kg whereas analyzed Cu values were: 8.05 ± 0.25, 11.25 ± 0.15, 14.20 ± 0.40, 16.55 ± 0.05, and 19.45 ± 0.45 mg/kg. Statistics were conducted using linear and quadratic polynomial regression models. No interactions occurred between dietary Cu and phytase (p > 0.05) for any response and no effects were found for the individual factors (phytase or dietary Cu) for Ht, Hb, varus, valgus, rotated tibia, and tibia breaking strength, as well as for Cu contents in breast, gastrocnemius tendon, and kidney (p > 0.05). However, the phytase-added diets led to higher BWG, lower FCR, and increased ileal digestible Cu (p < 0.05). The gradual increase in dietary Cu produced linear increases in Cu content in livers, as well as in excreta and retention (p < 0.05). Supplementing phytase at levels expected to maximize phytate degradation was demonstrated to improve BWG and FCR; however, no effects were observed when dietary Cu was increased to a maximum of 19.45 mg/kg. An increase of 8.8% in ileal digestible Cu was observed when birds were fed phytase.

Iron requirements of broiler chickens as affected by supplemental phytase

Iron is routinely supplemented in broiler feeds intending to prevent dietary deficiencies. The present research was conducted with the objective of assessing Fe requirements of broilers when fed supplemental phytase. A total of 1,280 1-d-old male Cobb × Cobb 500 were distributed in a 2 × 5 factorial arrangement (phytase-supplemented feeds × 5 graded increases of supplemental Fe) in 80 battery cages, eight replications of eight chicks each. The trial was replicated once. Chicks were fed a Fe-deficient diet without phytase (Fe analyzed at 31.30 ± 3.79 mg/kg) from placement to 7 d and then randomly distributed into battery cages with corresponding dieting treatments with or without phytase and graded increases of supplemental Fe. Feeds were formulated with corn and soybean meal (SBM), laboratory-grade calcium carbonate, and phosphoric acid; therefore, the vast majority of dietary Fe originated from corn and SBM (analyzed diet had 53.3 ± 1.41 mg/kg Fe). Phytase was added in excess to the producer recommendation of 1,000 FYT (4,452 ± 487 FYT/kg analyzed) such that phytate degradation was expected to be maximized. Supplemental Fe was from laboratory-grade ferrous sulfate heptahydrate (FeSO47H2O) which was increasingly added to the feeds (analyzed Fe in the supplemented feeds were: 53.3 ± 1.41, 65.5 ± 0.59, 77.2 ± 1.97, 87.6 ± 1.72, 97.7 ± 1.33 mg/kg). There were no interactions between phytase and dietary Fe for any response throughout the study (P > 0.05). Supplementing phytase had no effects on Fe intake or Fe excretion, as well as on hematocrit (Ht), hemoglobin (Hb), ferritin, Fe contents in the liver or thigh muscle color (P > 0.05). However, phytase-supplemented feeds produced better live performance as well as higher ileal digestible energy and Fe digestibility (P < 0.05). No effects were found for dietary Fe in live performance at day 28 (P > 0.05). On the other hand, increasing dietary Fe led to linear increases in Fe retention and excretion, Fe contents in livers, as well as Ht and Hb at 14 d (P < 0.05). Quadratic responses (P < 0.05) were observed for Hb at 21 d, serum ferritin on days 14, 21, and 28 (maximum responses were 83.3, 104.0, 91.9, and 88.3 mg/kg Fe, respectively). In conclusion, supplementing Fe adding to a total of 97.7 mg/kg dietary Fe did not affect live performance traits. However, the average of Fe-related blood parameters was maximized at 91.9 mg/kg dietary Fe. Supplementing phytase provided a significant increase in Fe digestibility.