A study was undertaken to examine the effects of a phytogenic feed additive (PFA) containing essential oils of thyme and star anise as lead active components on the growth performance and apparent ileal nutrient digestibility in broiler chickens. In total, 528 one-day-old Cobb male broilers were randomly divided into 4 dietary treatment groups with 6 replicate pens per treatment group (22 birds each). The dietary treatments were a control starter and grower basal diet without PFA or 150, 750, or 1,500 mg/kg of PFA. Body weight, weight gain, and feed intake were not significantly influenced by the feed additive, but the feed conversion ratio during the grower (22-42 d) and overall (1-42 d) periods improved linearly (P < 0.05) by the administration of PFA compared with that of the control diet. The average weights of the liver, heart, kidneys, and spleen were not significantly affected by the PFA. The results of the apparent ileal digestibility of crude ash, CP, crude fat, calcium, and phosphorus showed a linear increase (P < 0.05) related to the increase of PFA dose in the diet. Therefore, the means of digestibility of these nutrients were significantly higher in birds fed the PFA for all categories of age compared with the digestibility of these nutrients in the controls. In conclusion, the mode of action of the tested PFA can be explained by an improvement in the nutrient digestibility in the small intestine. The underlying physiological mechanisms, however, need to be characterized further.

The influence of the hypoglycemic drugs tolbutamide, meglitinide, glipizide and glibenclamide on ATP-dependent K+ currents of mouse pancreatic B-cells was studied using the whole-cell configuration of the patch-clamp technique. In the absence of albumin, tolbutamide blocked the currents half maximally at 4.1 mumol/l. In the presence of 2 mg/ml albumin half maximal inhibition of the currents was observed at 2.1 mumol/l meglitinide, 6.4 nmol/l glipizide and 4.0 nmol/l glibenclamide. The hyperglycemic sulfonamide diazoxide opened ATP-dependent K+ channels. Half maximally effective concentrations of diazoxide were 20 mumol/l with 0.3 mmol/l ATP and 102 mumol/l with 1 mmol/l ATP in the recording pipette. Thus, the action of diazoxide was dependent on the presence of ATP in the recording pipette. The free concentrations of the drugs which influenced ATP-dependent K+ currents were comparable with the free plasma concentrations in humans and the free concentrations which affected insulin secretion in vitro. The results support the view that the target for the actions of sulfonylureas and of diazoxide is the ATP-dependent K+ channel of the pancreatic B-cell or a structure closely related to this channel.

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.

The influence of low dietary levels of free and encapsulated medium-chain fatty acids on their concentrations in the digesta, the gastric microbial ecology and bacterial metabolic products in the gastrointestinal tract (GIT) in weaned piglets was studied. Starting after weaning, 36 piglets were fed a diet without (Control) or with medium-chain fatty acids uncoated (MCFA) or coated with vegetable fat and lecithin (MCFAc). After 4 weeks, the animals were killed, and digesta from the stomach and different sections of the GIT were collected. The concentrations of caprylic (p < 0.001) and capric (p = 0.001) acids were higher in the stomachs of piglets fed diets MCFA and MCFAc compared to the Control group. The concentrations dropped rapidly along the GIT, regardless of encapsulation, and tended to be higher in groups MCFA and MCFAc compared to the Control. Compared to the Control group, ingestion of diet MCFAc led to an increase in the number of eubacteria (p = 0.001), enterobacteriaceae (p < 0.001), clostridial clusters I (p = 0.001) and IV (p = 0.019), Lactobacillus johnsonii (p < 0.001) and Lactobacillus amylovorus (p = 0.001) in gastric contents. A similar trend was seen with diet MCFA. Relative concentrations of short-chain fatty acids were characterised by lower propionic acid levels (p = 0.045), numerically (p < 0.1) higher acetic, lower n-butyric and i-valeric acid concentrations in the small intestine. Lactic acid concentrations were not significantly changed in the GIT, but ammonia concentrations increased (p < 0.001) in the distal small intestine in the MCFA and MCFAc groups. In conclusion, medium-chain fatty acids affected microbial ecology parameters in the gastric contents and bacterial metabolites in the small intestine. At low dietary levels, medium-chain fatty acids may be regarded as modulators of the gastric microbiota in weaned piglets.

Inclusion of phytogenic feed additives (PFA) in feed may enhance performance of broilers. Levels of essential oils in powdered form (characterized by menthol and anethole) at 150 mg/kg (P-150) and matrix-encapsulated form (characterized by carvacrol, thymol, and limonene) at 100 mg/kg (ME-100) were supplemented in diet to investigate their effect on performance (trial 1) and apparent ileal digestibility (AID) of nutrients (trial 2) in broilers. A total of 480 1-day-old broilers (Cobb 500) were used in trial 1 and 120 broilers in trial 2. Broilers were distributed in 24 pens with 8 pens per treatment (trial 1) and 6 pens with 2 pens per treatment (trial 2), with 20 birds per pen. Feed and water were offered ad libitum throughout the experimental periods in both trials. In trial 1, body weight of birds at d 42 and overall body weight gain from d 1 to d 42, was higher in treatment ME-100 than birds in control treatment (P = 0.023 and P = 0.024, respectively). Feed efficiency during finisher phase was improved in treatment ME-100 relatively to control and P-150 treatments (P = 0.035). At d 21 in trial 2, the apparent ileal digestibility of crude protein was higher in ME-100 treatment in comparison with control and P-150 treatments (P < 0.001). Apparent ileal absorption (AIA) of phosphorus was higher in ME-100 treatment than control treatment (P = 0.028). AID of cysteine was higher in both phytogenic additive supplemented treatments in comparison with control treatment (P = 0.001). In conclusion, inclusion of a powdered phytogenic additive characterized by menthol and anethole at 150 mg/kg had no effect but only a tendency towards improved performance and AIA of phosphorus, whereas essential oils addition in encapsulated form characterized by caravacol, thymol, and limonene at 100 mg/kg improved performance as well as apparent ileal digestibility of nutrients in broilers, possibly due to improved secretion of digestive enzymes.

1. Three bacterial phytases derived from Bacillus, Escherichia coli or Klebsiella were compared with a phytase derived from Aspergillus niger in vitro and in vivo. 2. The in vitro results indicated that Aspergillus, E. coli and Klebsiella phytase displayed their activity optima in an acid pH range while Bacillus phytase did so in neutral pH. 3. The trials also revealed that only Bacillus phytase is more resistant to heat treatments, while E. coli and Klebsiella phytases are more stable against proteolytic inactivation. 4. In vivo phytases derived from Aspergillus, Bacillus, E. coli, Klebsiella or a combination of Bacillus and E. coli improved the utilisation of phosphorus (P balance) significantly to 0.54, 0.54, 0.55, 0.55 or 0.58, respectively, compared to 0.42 in the negative control. 5. The phytases used in this study seemed to be equally effective in improving P utilisation regardless of proposed intestinal site of activity. Combination of phytases acting in the gizzard with phytases acting in the intestine seems to be a promising way to further improving in vivo efficacy of phytases in poultry.

No abstract

Phytogenic feed additives represent a potential alternative to antibiotics with attributed health and growth-promoting effects. Chickens supplemented with an essential oil blend, a Quillaja saponin blend, or a combination of both phytogenic preparations showed a comprehensively and significantly improved apparent ileal digestibility of crude protein and amino acids compared to control birds. Accordingly, holistic transcriptomic analyses of jejunum and liver samples indicated alterations of macromolecule transporters and processing pathways likely culminating in an increased uptake and metabolizing of carbohydrates and fatty acids. Complementary analyses in Caco-2 showed a significant increase in transporter recruitment to the membrane (SGLT1 and PEPT1) after addition of essential oils and saponins. Although the penetrance of effects differed for the used phytogenic feed additives, the results indicate for an overlapping mode of action including local effects at the intestinal border and systemic alterations of macronutrient metabolism resulting in an improved performance of broilers.