The effect of exogenously administered recombinant bovine somatotropin on intestinal phytase activity andin vivophytate hydrolysis in hybrid striped bassMorone chrysops × M. saxatilis

Abstract

It has been recently demonstrated that hybrid striped bass Morone chrysops · M. saxatilis exhibit intestinal phytase activity, an enzyme capable of liberating inorganic orthophosphate from the phytate molecule, thereby making phytate phosphorus (PP) available for absorption and utilization by the fish. However, it was also determined that hybrid bass were able to digest only 1-2% of dietary PP. Therefore, an experiment was conducted to determine if exogenously administered recombinant bovine somatotropin (rbST) would increase intestinal phytase activity in hybrid striped bass to a level that would improve PP availability. The results indicate that exogenous rbST treatment, administered either through intraperitoneal injection or orally, does increase intestinal brush border membrane protein concentration. While injection with rbST led to significant increases in both specific brush border membrane and total intestinal phytase activity, oral rbST administration did not cause similar increases. Total P and PP digestibility were not influenced by rbST administration. While treatment with rbST does have the potential to enhance intestinal phytase activity in hybrid striped bass, it does not appear to increase PP digestibility. This observation limits the hormone's utility as an effective technique for improving PP bioavailability to this species. KEY WORDS KEY WORDS: acid phosphatase, hybrid striped bass Morone chrysops · M. saxatilis, intestinal phytase, maltase, phytate phosphorus digestibility, somatotropin

Phytate and phytase in fish nutrition

“…(2003) has confirmed the presence of intestinal BBM phytase activity in Nile tilapia and also observed some phytase activity in hybrid striped bass Morone saxatilis x M. chrysops and M. chrysops × M. saxatilis and common carp Cyprinus carpio also. Although intestinal phytase activity has been detected in several fish species, its application for phytate hydrolysis is not satisfactory for fish nutrition (Ellestad et al., 2003). Recently, Shi et al.…”

“…Tilapia Oreochromis niloticus · O. aureus (LaVorgna, 1998) are capable of releasing inorganic P from phytate and this phytase activity appears to be localized in the small intestinal brush border membrane (BBM) (Maenz and Classen, 1998). Therefore Nile tilapia can digest approximately 50% of dietary phytate P. Research conducted by Ellestad et al (2003) has confirmed the presence of intestinal BBM phytase activity in Nile tilapia and also observed some phytase activity in hybrid striped bass Morone saxatilis x M. chrysops and M. chrysops · M. saxatilis and common carp Cyprinus carpio also. Although intestinal phytase activity has been detected in several fish species, its application for phytate hydrolysis is not satisfactory for fish nutrition (Ellestad et al, 2003).…”

Dietary protein level, microbial phytase, citric acid and their interactions on bone mineralization of Labeo rohita (Hamilton) juveniles

“…Phytase is an enzyme specific to phytate hydrolysis. Although intestinal phytase activity has been detected in several fish species, it was insufficient for any significant improvement in phytate hydrolysis in most teleosts (Ellestad, Dahl, Angel & Soares 2003). However, dietary supplementation of phytase improves the availability of phosphorus along with other minerals as observed in several fish species like rainbow trout, Oncorhynchus mykiss (Cain & Garling 1995; Rodehutscord & Pfeffer 1995; Forster, Higgs, Dosanjh, Rowshandeli & Par 1999), common carp, Cyprinus carpio (Schafer, Koppe, Meyer‐Burgdorff & Gunther 1995), channel catfish, Ictalurus punctatus (Jackson, Li & Robinson 1996; Li & Robinson 1997), African catfish, Clarias gariepinus (Van Weerd, Khalaf, Aartsen & Tijssen 1999), stripped bass, Morone saxatilis (Papatryphon & Soares 2001) and Pangasius pangasius (Debnath, Sahu, Pal, Jain, Yengkokpam & Mukherjee 2004).…”

Effect of dietary microbial phytase supplementation on growth and nutrient digestibility of Pangasius pangasius (Hamilton) fingerlings

“…Fish cannot digest phytate phosphorus as they lack the intestinal phytase (Pointillart, Fourdin & Fontaine 1987) evident from the reduced growth of channel catfish fed diet supplemented with 4 g phytate kg −1 (Andrews, Murai & Campbell 1973). Recently, Ellestad, Dahl, Angel and Soares Jr (2003) reported that in spite of the presence of intestinal phytase activity in some teleosts, they digest only a very small portion of the phytate phosphorus present in the diet, except hybrid tilapia ( Oreochromis niloticus × O. aureus ), which can digest around 50% of the dietary phytate phosphorus (Ellestad 2002). Generally, phytate phosphorus is excreted in the faeces and contributes to nutrient enrichment and subsequently algal growth in aquatic ecosystems.…”