Influence of high dose of phytase and an emulsifier on performance,apparent metabolisable energy and nitrogen retention in broilers fed on diets containing soy oil or tallow

1. The effects of high dose of microbial phytase and an emulsifier on the performance, apparent metabolisable energy (AME) and nitrogen (N) retention in broilers fed on diets containing different fat sources were examined in a 5-week trial. Two fat sources (soy oil and tallow), two inclusion levels of E. coli phytase (500 or 1000 phytase units (FTU)/kg diet) and two inclusion levels of lysolecithin emulsifier (0 or 3.5 g/kg of diet) were evaluated in a 2 × 2 × 2 factorial arrangement of treatments.

2. Throughout the 5-week trial, soy oil supplementation improved weight gain and feed per gain compared with tallow, but had no effect on feed intake.

3. The high dose of phytase increased the weight gain and feed intake and lowered the feed per gain during d 1–21, but had no effect on performance parameters over the whole trial period.

4. An effect of emulsifier was observed for feed intake during d 1–21 and over the whole trial period. Addition of emulsifier increased feed intake compared with diets without emulsifier.

5. During weeks 1, 2, 3 and 5, birds fed on soy oil–based diets had higher nitrogen-corrected AME (AME_N) compared with those fed on tallow-based diets. During weeks 2, 3 and 5, the effect of phytase was significant for AME_N, with the high dose increasing the AME_N. During week 2, AME_N was increased with emulsifier addition.

6. During weeks 1, 2, 3 and 5, birds fed on soy oil–based diets had higher fat retention compared with those fed on tallow-based diets. The high dose of phytase improved the retention of fat during week 5 and the addition of emulsifier resulted in higher fat retention during week 1.

7. During weeks 2, 3 and 5, an interaction between fat source × phytase × emulsifier was observed for N retention. In soy oil–based diets, emulsifier plus 1000 FTU/kg phytase increased N retention compared with other groups, while in tallow-based diets, emulsifier addition increased N retention in diets with 500 FTU/kg, but not in 1000 FTU/kg diet.

8. Overall, the present data suggest that the dietary fat source influenced performance, AME_N and fat retention in broiler chickens. There is opportunity to improve bird performance during d 1–21, AME_N and fat retention with higher doses of microbial phytase. Addition of the emulsifier increased the AME_N during week 2 and tract retention of fat during week 1, but this effect was not translated into improvements in performance.

     

Evaluation of a layer diet formulated from non‐conventional feedingstuffs

1. A layer diet, the formulation of which was based on several non‐conventional feedingstuffs, was evaluated at the research station and under small farm conditions in Sri Lanka. The new feedingstuffs included finger millet, rice polishings, rubber seed meal, cassava leaf meal, ipil ipil leaf meal and dried poultry manure. A commercial mash, that is normally used on the farm, served as the control.

2. The performance and egg quality characteristics were similar between the test and control diets, the only exception being the egg yolk colour which was improved (P< 0.05) by feeding the test diet. Food cost per dozen eggs was lowered by feeding the test diet.

3. It is possible to formulate layer diets using non‐conventional feedingstuffs, achieve acceptable production and lower the food costs under small farm conditions in tropical developing countries.     

Detection of Babesia bigemina DNA in ticks by DNA hybridization using a nonradioactive probe generated by arbitrary PCR

The Dig-labeled probe specific to Babesia bigemina generated from monomorphic RAPD fragment of approximately 873 bp size amplified by a 10 mer CGGTGGCGAA, detected up to 100 ng of template DNA. This nonradioactive probe also detected B. bigemina in preparations of larval tick DNA from two of the five samples on dot-blot hybridization.     

Consequences of calcium interactions with phytate and phytase for poultry and pigs

Despite increasing practical experience and cascades of scientific reports on exogenous microbial phytases, several issues associated with their use remain unresolved because of the ambiguous and, at times, conflicting data that has been generated. One possible cause of these inconsistent outcomes is dietary calcium (Ca) levels, which are mainly derived from limestone. Thus the purpose of this review is to examine Ca interactions with dietary phytate and phytases, particularly exogenous, microbial phytases, and their consequences for poultry and pigs. The polyanionic phytate molecule has a tremendous capacity to chelate cations and form insoluble Ca–phytate complexes, which are refractory to phytase activity. Thus Ca–phytate complex formation along the gastrointestinal tract, where one phytate (IP₆) molecule binds up to five Ca atoms, assumes importance and approximately one third of dietary Ca may be bound to phytate in digesta. Consequently, phytate limits the availability of both P and Ca as a result of insoluble Ca–phytate complex formation, the extent of which is driven by gut pH and molar ratios of the two components. It is accepted that Ca–phytate complexes are mainly formed in the small intestine where they have a substantial negative influence on the efficacy of mucosal phytase. However, exogenous phytases are mainly active in more proximal segments of the gut and lower pH levels, so their efficacy should not be influenced by Ca–phytate complexes in the small intestine. There is, however, data to indicate that Ca and phytate interactions occur under acidic conditions with the formation of soluble and insoluble Ca–phytate species, which could negatively impact on exogenous phytase efficacy. Also, Ca will tend to elevate gut pH because of limestone's very high acid binding capacity, which will favour Ca–phytate interactions and may influence the activity of exogenous phytases depending on their pH activity spectrum. The de novo formation of binary protein–phytate complexes that are refractory to pepsin hydrolysis may be fundamental to the negative impact of phytate on the digestibility of protein/amino acids. However, high dietary Ca levels may disrupt protein–phytate complex formation by interacting with both phytate and protein even at acidic pH levels, thereby influencing the outcomes of phytase amino acid digestibility assays. Finally, it is increasingly necessary to define the Ca and nonphytate-P requirements of pigs and poultry offered phytase-supplemented diets.     

Effects of microbial phytase, produced by solid-state fermentation, on the performance and nutrient utilisation of broilers fed maize- and wheat-based diets

1. The influence of a microbial phytase on the performance, toe ash contents and nutrient utilisation of male broilers fed diets based on maize and wheat was investigated. The experiment was conducted as 2 x 2 x 2 factorial arrangement of treatments. Within the factorial, two diet types (maize-soy or wheat-soy) containing two levels of non-phytate phosphorus (3.0 or 4.5 g/kg) were evaluated and each level of non-phytate phosphorus was supplemented with 0 or 500 PU phytase/kg diet. Each of the 8 dietary treatments were fed to 6 pens of 8 birds from d 1 to 21 post-hatching. 2. Main effects of diet type and phytase were observed for all parameters. Main effect of non-phytate phosphorus was significant only for feed/gain and toe ash contents. Phytase addition improved weight gains irrespective of diet type or non-phytate phosphorus level, but the magnitude of improvement in the phosphorus-deficient wheat-soy diet was greater, resulting in a diet type x non-phytate phosphorus interaction. Responses in toe ash contents were noted only in phosphorus-deficient diets, as indicated by a non-phytate phosphorus x phytase interaction. 3. Phytase addition improved apparent metabolisable energy values of wheat-based diets, but had little effect on the apparent metabolisable energy of maize-based diets as shown by a diet type x phytase interaction. The apparent metabolisable energy was not influenced by dietary non-phytate P. 4. Phytase improved ileal nitrogen digestibility in both diet types, but the responses to added phytase tended to be higher in wheat-based diets, as shown by a diet type x phytase interaction. 5. Increasing the dietary non-phytate phosphorus level reduced phosphorus digestibility and increased excreta phosphorus content. Addition of phytase improved phosphorus digestibility, but the increments were higher in low phosphorus diets resulting in a non-phytate phosphorus x phytase interaction. Phytase addition tended to lower the excreta phosphorus content, but the effects were greater in birds fed low phosphorus diets, as shown by a non-phytate phosphorus x phytase interaction.     

Influence of caecectomy and dietary protein concentration on apparent excreta amino acid digestibility in adult cockerels

1. The influence of caecectomy and dietary crude protein content (50, 100, 150, 200 and 250 g/kg diet) on the apparent excreta amino acid digestibilities in adult cockerels fed on semi‐purified diets containing soyabean meal (SBM) or cottonseed meal (CSM) as the sole source of protein was investigated.

2. Caecectomy had no influence on the apparent digestibilities of most amino acids in SBM, the exceptions being histidine, arginine and lysine, but lowered the apparent digestibility of amino acids in CSM.

3. The protein content in assay diets has a strong influence on the apparent amino acid digestibility values for poultry. Apparent values are lower when the dietary protein content is low.

4. The use of a single endogenous amino acid output value, generated by regression analysis or protein‐free diets, for true digestibility adjustments across a wide range of protein intakes is questioned. In particular, such an application will penalise estimates of apparent digestibility when the dietary protein content is high.     

饲料酶制剂在动物营养中的应用--最新动态及展望

1饲料酶制剂 家禽及猪饲料添加酶制剂以提高生产性能已经有许多年历史。但仅在过去的20年里，人们对酶昕作用的底物的结构及化学性质才有更好的了解，这才使针对特定的底物来调制酶制剂成为可能：在生物技术方面，特别是在发酵和微生物技术方面已有了突破性进展，这也才使最近10年里能够生产足够物美价廉的饲用酶制剂成为现实，以保证在家禽口粮中的应用。     

Nutrient digestibility and energy utilisation of diets based on wheat, sorghum or maize by the newly hatched broiler chick

1. Two experiments were conducted to measure changes in nutrient utilisation in the newly hatched broiler chicken. The first experiment determined the nitrogen-corrected apparent metabolisable energy (AME(N)) and total tract digestibility of starch and fat in diets based on wheat, sorghum and maize during the first two weeks post-hatch. The second experiment was conducted to confirm the results of Experiment 1 using wheat- and maize-based diets and was of 21 d duration. 2. In both experiments, changes to AME(N) with age were similar irrespective of the diet type, declining from d 3 to d 5-9 and then increasing after d 9. 3. In Experiment 1, the total tract digestibility of starch and fat exhibited a pattern similar to that of AME(N). 4. In Experiment 1, cereal effects were significant, with maize- and sorghum-based diets having higher AME(N) values than the wheat-based diet. Total tract starch digestibility determined for d 5, 7 and 14 showed no cereal differences. Total tract fat digestibility on d 7 was significantly lower for the wheat- and sorghum-based diets than for the maize-based diet, but no cereal differences were observed on d 5 or 14. 5. In Experiment 2, cereal effects were significant, with the maize-based diet having a higher AME(N) than the wheat-based diet. 6. These results showed that nutrient utilisation is compromised during the first week of life of the broiler chick.     

Effect of exogenous enzymes in maize-based diets varying in nutrient density for young broilers: growth performance and digestibility of energy, minerals and amino acids

1. A total of 192 male broilers (Cobb 500) were used in a growth and digestibility assay, involving a 2 x 2 factorial arrangement of treatments, to assess the effects of an enzyme cocktail of xylanase, amylase and protease in maize-based diets. 2. The following two diets were formulated: a positive control diet containing adequate nutrient concentrations for broiler starters as per breeder recommendations and a negative control diet to contain approximately 0.63 MJ/kg apparent metabolisable energy (AME) and 3% amino acids less than the positive control. 3. A further two dietary treatments were developed by supplementing each control diet with an enzyme product containing xylanase, amylase and protease. 4. Birds fed on the negative control diet had poorer weight gain and feed efficiency than those given the positive control diet. There was no effect of diet or enzyme on feed intake. The digestibility of nitrogen, calcium, phosphorus and most amino acids were unaffected by dietary nutrient density. 5. Supplementation of both the positive and negative control diets with the enzyme improved weight gain and feed efficiency compared with the unsupplemented diets. In the case of the negative control, supplemental enzyme improved performance to that of the unsupplemented positive control diet. There was no interaction between diet and enzyme for either weight gain or FCR, suggesting similar beneficial responses regardless of the nutrient density of the diet. 6. In both diets, enzyme supplementation improved AME by an average of 3% (0.35 MJ/kg DM) and nitrogen retention by an average of 11.7% (26 g/kg DM intake vs 29 g/kg DM intake). There was no interaction between diet and enzyme for AME or nitrogen retention. 7. Ileal digestibilities of calcium and phosphorus were not influenced by supplemental enzyme, whereas the digestibility of nitrogen and most amino acids was improved by enzyme addition compared with the unsupplemented control diets. There was no interaction between diet and enzyme for the ileal digestibility of nitrogen and amino acids. 8. These data demonstrate that it is possible to improve the nutritional value of a maize/soy-based diet for broiler starters through the use of exogenous enzymes. The nutrient density of the diet does not appear markedly to influence the response to enzyme, offering flexibility in the use of enzymes for maize-based diets. 9. It is concluded that the energy and amino acid values of maize-based diets for broilers can be enhanced by supplementation with an enzyme cocktail of xylanase, amylase and protease, offering potential economic benefits to producers.