The physical and chemical properties of six crude phytase preparations were compared. Four of these enzymes (Aspergillus A, Aspergillus R, Peniophora and Aspergillus T) were produced at commercial scale for the use as feed additives while the other two (E. coli and Bacillus) were produced at laboratory scale. The encoding genes of the enzymes were from different microbial origins (4 of fungal origin and 2 of bacterial origin, i.e., E. coli and Bacillus phytases). One of the fungal phytases (Aspergillus R) was expressed in transgenic rape. The enzymes were studied for their pH behaviour, temperature optimum and stability and resistance to protease inactivation. The phytases were found to exhibit different properties depending on source of the phytase gene and the production organism. The pH profiles of the enzymes showed that the fungal phytases had their pH optima ranging from 4.5 to 5.5. The bacterial E. coli phytase had also its pH optimum in the acidic range at pH 4.5 while the pH optimum for the Bacillus enzyme was identified at pH 7.0. Temperature optima were at 50 and 60 degrees C for the fungal and bacterial phytases, respectively. The Bacillus phytase was more thermostable in aqueous solutions than all other enzymes. In pelleting experiments performed at 60, 70 and 80 degrees C in the conditioner, Aspergillus A, Peniophora (measurement at pH 5.5) and E. coli phytases were more heat stable compared to other enzymes (Bacillus enzyme was not included). At a temperature of 70 degrees C in the conditioner, these enzymes maintained a residual activity of approximately 70% after pelleting compared to approximately 30% determined for the other enzymes. Incubation of enzyme preparations with porcine proteases revealed that only E. coli phytase was insensitive against pepsin and pancreatin. Incubation of the enzymes in digesta supernatants from various segments of the digestive tract of hens revealed that digesta from stomach inactivated the enzymes most efficiently except E. coli phytase which had a residual activity of 93% after 60 min incubation at 40 degrees C. It can be concluded that phytases of various microbial origins behave differently with respect to their in vitro properties which could be of importance for future developments of phytase preparations. Especially bacterial phytases contain properties like high temperature stability (Bacillus phytase) and high proteolytic stability (E. coli phytase) which make them favourable for future applications as feed additives.

For the evaluation of the effectiveness of phytase preparations as feed additive, in vitro properties like temperature optimum, temperature stability, pH optimum and pH profile or proteolytic stability are of utmost importance. Although at present all commercial phytase preparations authorized as feed additives in the EU are produced by recombinant filamentous fungi and have similar in vitro properties (acidic pH optimum, narrow pH range, low thermostability) the diversity of microbial phytases is great. Microbial sources for phytases span from fungi and yeasts to bacteria. Some of the naturally occurring phytases were identified to have high thermostability and a broad pH range (e.g. Aspergillus fumigatus phytase). The bacterial Bacillus phytases generally differ from other phytases, having a pH optimum from 7.0 to 8.0, being Ca 2+ dependent and highly specific for phytate. Thermostability can considerably be increased by protein engineering. A so-called Consensus phytase encoded by a synthetic gene was found to be stable in aqueous solutions at 70°C and in feed at pelleting temperatures of 80-90°C. The rate and site of inactivation of feed enzymes in the digestive tract are determined by their susceptibility to proteolytic enzymes. Highest residual activities after incubation in the presence of pepsin or in supernatants of stomach digesta was observed for Escherichia coli and Consensus phytases, while the Bacillus phytase was found to be most resistant to pancreatin. Comparative studies on in vitro properties of enzymes intended for use as feed additives provide valuable information for prediction of in vivo effectiveness.

The nutritive potential of rumen liquor fermented cassava peels (RLFCP) was assessed in rabbit nutrition in an 8 weeks trial. The freshly collected droppings from layers were sundried, ground and mixed at 100 g/kg with ground cassava peels, sprayed with rumen filtrate and fermented for 144 hours. Thereafter, one basal diet was formulated to meet the nutrient requirement of a growing rabbit. The maize content (43 g/100 g) of the basal diet was replaced at 0, 25, 50, 75 and 100 % with RLFCP and named as diets 1, 2, 3, 4 and 5 respectively. One hundred and fifty mixed sexes healthy 5-weeks old crossbred weaner rabbits were randomly distributed among the five dietary treatments at a rate of 30 rabbits per treatment. The response criteria were growth indices, cost benefit, carcass and organ weight, blood and serum indices. While the average daily feed intake increased (49.27-58.00 g/rabbit/day) with an increased RLFCP inclusion, the average daily weight gain only increased (12.38-17.75 g/rabbit per day) when the increased RLFCP inclusion reached up to a 50 %. The feed conversion ratio of rabbits fed on the control and those fed on 25 % and 50 % RLFCP was similar (3.03-3.20) (p>0.05). Only the slaughtered weight (1116.50-1416.16 g), dressed weight (477.65-695.85 g), dressing % (42.77-50.14), relative weight (% slaughter weight) of the liver (2.18-2.57) and heart (0.20-0.23) were significantly (p

Background: This study evaluates the effects of storage periods (1, 4, 7, 10, and 13 days), egg size (small 60-64 g, medium 65-69 g, and large ≥ 70 g), and egg positioning with air cell facing either down or up during storage on hatchability percentages and day-old chick's weight. One thousand and five hundred (1500) fertile eggs from Arbor acre broiler breed were purchased and arranged each according to egg sizes into five (5) different storage periods of 100 eggs per storage period. Each storage period was subdivided into 2 groups of 50 eggs each based on positioning during storage. A completely randomized design in 3 × 5 × 2 factorial arrangement was adopted. Stored eggs were incubated for hatch with recording of weights of the hatched chicks, and the hatchability rate was calculated. Results: The results indicated eggs stored for a day and 4 days had maximum hatchability, but declined slightly as the storage period increased (92 to 78%). The eggs positioned down generally had better hatchability. However, mediumsized eggs had the highest hatchability percentage. On the other hand, large-sized eggs stored for longer period attained higher chick weight compared to medium-and small-sized eggs, but large-sized eggs positioned down gave a better chick weight. Generally, eggs stored with air cell down present superior chick weight. Conclusion: Storage period and egg positioning during storage affect the subsequent egg hatchability and weight of the hatched chicks from different egg sizes. However, egg storage must not exceed 4 days for optimum hatchability and weight of the hatched chicks. In addition, storing of eggs with air cell down might also enhance the hatchability and weight of hatched chicks irrespective of the weight of the eggs.

The effectiveness of an Escherichia coli phytase in comparison with a commercially available Aspergillus phytase in improving the bioavailability of phosphorus in broilers, layers and young pigs was studied in three separate experiments. Three basal diets, marginally deficient in dietary P mainly provided as phytate, were formulated. Both phytases were added to the diets at the rate of 500 U/kg diet. The phytases significantly (P < or = 0.05) improved the availability of phytate P to broilers, layers and young pigs. Aspergillus and E. coli phytases enhanced the pre-caecal digestibility of P by 11 and 29% for broilers and 18 and 25% for layers, respectively. Total tract digestibility of P (P balance) was also enhanced but with smaller magnitude. In pigs, total tract digestibility of P was improved by 33 and 34% by Aspergillus and E. coli phytases, respectively. Under the conditions of this study, it was observed that E. coli consistently, though with small magnitude in layers and pigs, enhanced the availability of phytate P at the same range or slightly better than Aspergillus phytase. It was only in pigs that the availability of Ca was significantly (P < or = 0.05) improved by addition of both phytases. It can be concluded that E. coli phytase is highly effective in improving the bioavailability of phytate P to broilers, layers and young pigs. This seems to be based on the high proteolytic stability of the enzyme in the digestive tract, as shown recently.