Effects of Fungal Phytase on Utilization of Dietary Protein and Minerals, and Dephosphorylation of Phytic Acid in the Alimentary Tract of Channel Catfish Ictalurus punctatus Fed an All‐Plant‐Protein Diet

Abstract

A feeding trial was conducted to quantify the effects of phytase at levels of 0, 500, 1,000, 2,000, 4,000, and 8,000 units (U) per kg diet on utilization of dietary protein and minerals by fingerling (12 g) channel catfish Ictalurus punctatus fed an all‐plant‐protein diet composed of soybean meal, corn, and wheat middlings. The effects of phytase on dephosphorylation of phytic acid (phytate) in the alimentary tract of catfish also were determined. After 14 wk, mean weight gains (30.2–43.9 g/fish), feed conversion ratios (2.27–2.40 g feed consumed/g weight gain), protein efficiency ratios (1.47–1.61 g weight gaid/g protein consumed), and dietary protein retentions (23.8–26.7%) did not differ significantly (P > 0.05) among treatment groups. A digestibility trial conducted after the feeding trial showed no difference (P > 0.05) in mean digestibility of diet dry matter (49.0–58.3%) or crude protein (85.4‐88.5%) among treatment groups. Concentrations of ash (46.7–48.6%), calcium (Ca, 17.9–18.5%), phosphorus (P, 9.1–9.5%), and manganese (Mn, 65.5–74.1 mg/kg) were significantly higher (P ≤ 0.05) in bone of fish fed ≥ 500 U/kg than in bone of fish fed 0 U/kg (ash, 43.5%; Ca, 16.4%; P, 8.4%; and Mn, 49.0 ma/kg), but concentrations of these minerals did not differ (P > 0.05) in bone of fish fed ≥ 500 Uk/g. The magnesium (Mg) content of bone did not differ (P > 0.05) between fish fed 0 U/kg (0.29%) or 500 U/kg (0.34%), but was significantly lower in fish fed 0 U/kg than in fish fed ≥ 1,000 U/kg (0.35–37%). Bone Mg levels did not differ (P > 0.05) among fish fed ≥ 500 U/kg. The amount of zinc (Zn) in bone of fish fed 8,000 U/kg (153.3 mg/kg) was significantly higher than that in fish fed 0 U/kg (115.7 mg/kg) or 500 U/kg (130.3 mg/ kg), but did not differ from Zn levels in bone of fish fed 1,000–4,000 U/kg (134.5–135.8 mg/ kg). Dephosphorylation of phytate occurred primarily in the stomach within 2–8 h after diet ingestion, depending on the level of phytase supplementation. Initial levels of total phytate in the diet decreased 32–94% in stomach contents of fish fed l,000–8,000 U/kg within 2 h after feeding. Eight hours after feeding, stomach contents of fish fed ≥ 1,000 U/kg contained less than 6% of initial total dietary phytate. Stomach contents of fish fed 500 U/kg retained 92% of initial total dietary phytate 2 h after feeding and 15% of total dietary phytate 8 h after feeding. Results of this study indicate that phytase supplementation at levels up to 8,000 U/kg diet did not increase weight gain or improve dietary protein utilization of channel catfish fed an all‐plant‐protein diet. Addition of phytase at a level of 1,000 U/kg diet was sufficient to significantly increase the Ca, P, Mg, and Mn content of bone, relative to fish fed an unsupplemented diet, and significantly decrease the quantity of total phytate in feces. A phytase level of 8,000 U/kg diet significantly increased the bioavailability of naturally occurring Zn in feed ingredients and increased the rate of phytate dephosphorylation in the stomach, co...

Comparative efficacy of phytase from fish gut bacteria and a commercially available phytase in improving the nutritive value of sesame oilseed meal in formulated diets for fingerlings of rohu, Labeo rohita (Actinopterygii: Cypriniformes: Cyprinidae)

“…The performance of fi sh reared on the control and raw oilseed meal incorporated diets were poor compared to fi sh reared on other experimental diets in terms of weight gain, PER, FCR, deposition of crude protein and lipid in the carcass, and apparent nutrient (crude protein, lipid) digestibility. However, the signifi cant increase in body protein accretion and nutrient (crude protein, lipid) digestibility recorded from this study disagree with the report of Yan et al (2002), who demonstrated that weight gain and dietary protein utilization of channel catfi sh were not improved by phytase addition.…”

“…Apparent digestibility of phosphorus, calcium, manganese, iron, and zinc from barley, canola meal, wheat, and wheat middling by rainbow trout also has been reported to increase with the addition of phytase (Gatlin and Li 2008). Omnivorous fi sh species such as channel catfi sh, Ictalurus punctatus, has been shown to exhibit increased phosphorus utilization from soybean meal based diets with the supplementation of phytase (Yan et al 2002). …”

Effect of Phytase on Growth and Phosphorus Utilization in Japanese Flounder (Paralichthys olivaceus)

“…Several investigators have also reported that a significant amount of dephosphorylation of phytate occured in a phytase-supplemented diet during diet preparation (Scafer et al 1995, Branden and Carter 1999, Yan et al 2002. The advantageous effects of phytase in SBM-containing diets were confirmed in this feeding experiment with improved growth performance, feed conversion, feed efficiency, P and protein digestibility and mineral utilization by Japanese flounder.…”

FLUCTUATION OF POST-PRANDIAL PLASMA MINERAL LEVEL OF JUVENILE JAPANESE FLOUNDER, Paralichthys olivaceus FED DIETARY PHOSPHORUS AND PHYTASE SUPPLEMENTATION

“…Incorporation of dietary phytase in fish diets have been reported to improve P availability and growth performances (Rodehutscord & Pfeffer, 1995;Yan & Reigh, 2002). However, the observation of the specific effects of phytase in different fish species is insufficient.…”