Prececal amino acid digestibility and phytate degradation in broiler chickens when using different oilseed meals, phytase and protease supplements in the feed

Supplemental phosphorus can be completely replaced with microbial phytase in White Leghorn layer diets

1. A study was conducted to assess the possibility of totally replacing supplemental phosphorus sources in White Leghorn (WL) layer diets (aged 28 to 45 weeks of age) with microbial phytase supplementation. One thousand commercial layers (HyLine White) of 28 weeks of age were housed in California cages fitted in open-sided poultry shed at the rate of 20 layers in each replicate. Ten replicates were randomly allotted to each treatment, and the respective diet was fed from 28 to 45 weeks of age.2. A control diet (CD) containing the recommended levels of non-phytate phosphorus (3.6 g/kg NPP) and four other test diets (2-5) having sub-optimal levels of NPP (2.4, 2.0, 1.6 and 1.2 g/kg), but with supplemental microbial phytase (600 FTU/kg) were prepared and fed for the trial duration.3. The layers fed with lower levels of NPP with phytase had the same laying performance as the group fed the CD. Egg production, feed efficiency, egg mass, shell defects, egg density, shell weight, shell thickness, ash content and breaking strength of the tibia and sternum were not affected by feeding the lowest concentration of NPP (1.2 g/kg) plus microbial phytase.4. Phytase supplementation in diets with sub-optimal levels of NPP (2.4, 2 and 1.6 g/kg) significantly improved the Haugh unit score compared to those fed the CD.5. It was concluded that supplemental phosphorus can be completely replaced with microbial phytase (600 FTU/kg) in a diet without affecting egg production, shell quality or bone mineral variables in WL layers (28 to 45 weeks).

Different levels of single-strain probiotic (Bacillus subtilis) with proteolytic enzyme (serratiopeptidase) can be used as an alternative to antibiotic growth promoters in broiler

In the current study, the proteolytic enzyme (serratiopeptidase) was used to enhance the efficacy of Bacillus subtilis (B. subtilis) probiotic as a growth promotor in broiler chicken. The effects of serratiopeptidase on the efficacy of different levels of B. subtilis as a growth promotor in broiler chicks were evaluated regarding growth performance traits, villus histomorphometric characterization, and intestinal microbiota count. Day-old broiler chicks (n = 120) were allocated into 4 groups having 3 replicates/group. In the control group (C), the basal diet was kept without supplementation. In treatment groups (P100, P150, and P200), the basal diet was supplemented with 100, 150, and 200 mg probiotics, respectively besides 30 mg proteolytic enzyme in the 3 treated groups for 4 wk. The performance parameters were significantly affected by the supplementation of serratiopeptidase to the B. subtilis treatment groups. Feed intake (FI), body weight gain (WG), feed conversion ratio (FCR), and dressing percent were significantly improved in the treatment groups as compared to the control group. Significantly, the lowest feed intake was recorded for the P200 group. The highest body weight gain and dressing percentage were recorded for the P200 group. An improved FCR was recorded in the P200 group (1.7) as compared to the control group. The different levels of B. subtilis supplemented with serratiopeptidase revealed significant improvements (P<0.05) in the morphology of the intestine by showing increases in villus height and width and crypt depth of the small intestine. The microbial count revealed that E. coli and salmonella colonies were significantly reduced in the P200 group as compared to the control and other treatment groups. In conclusion, the supplementation of B. subtilis with serratiopeptidase as a growth promoter in broiler chicks significantly improved the overall performance, and intestinal health and reduced microbial load contributing to optimizing the performance of broiler chickens. The greatest improvement was observed in the P200 group fed with B. subtilis as a probiotic and serratiopeptidase enzyme (200 mg:30 mg).

Assessment of the inclusion of a feed additive of sodium humate derived from freshwater sapropel in diets for broiler chickens

Background and Aim

Poultry production is the fastest growing livestock industry in the world, as the rapid growth of and efficient absorption of feed by poultry ensure the production of poultry meat with a relatively low carbon footprint. Seeking new ways to increase livestock productivity as well as poultry product quality, the number of research studies on the use of humic substances of various origins in livestock farming has increased significantly, emphasizing the role of feed additives derived from local resources. The unique capability of humic substances to improve metabolic processes allows the immune protection of the bird body to be strengthened and production efficiency to be increased. This study aimed to identify the effects of sodium humate (NaHum) on the growth performance of broiler chickens and selected blood and ileum microbiota parameters.

Materials and Methods

Dietary research was conducted 2 times under production conditions in a poultry facility of a commercial company, with 210 1-day-old, unsorted broiler chickens of both sexes (Ross 308). The broiler chickens were fed with standard commercial feed, the rearing period of 35 days, and slaughtered on day 36. Sodium humate additive was added to drinking water for the research groups of broilers in period from 8th to 35th day of life, 25 mL (Group 1, n = 2 × 35) and 50 mL (Group 2, n = 2 × 35) per liter of drinking water. Sodium humate contained an average of 4.48% dry matter, a kilogram of dry matter containing 104.3 g of crude protein, 3.6 g of crude fiber and 0.9 g of crude fat, 14.3 MJ of metabolic energy, and 5.8 MJ of energy for live weight gain, as well as a very high content of crude ash -759.8 g, including 4.2 g Ca, 4.2 g Na, and 4.81 g Fe, the dry matter digestibility of NaHum was 87.0%, and the absorption capacity of dry matter was 113.2%., the pH level was 13.0, i.e., alkaline. At the end of the dietary research, the productivity and economic efficiency of the research groups of broilers were calculated by live weight gain, carcass weight, feed conversation ratio, and blood and intestinal samples of broilers were analyzed to identify the effects of NaHum on the growth performance and health status of broilers.

Results

Dietary research found that adding 25 mL/L and 50 mL/L of NaHum to drinking water for the broiler chickens increased their live weights at the selling age, average live weight gains by 3.06-3.93%, and carcass weights by 5.07-6.06%, while feed conversion increased in terms of both live weight (1.5 and 1.51) and carcass weight (1.84 and 1.86) compared with the control group. The best economic performance in terms of the economic efficiency index and the cost index (CI) was found in Group 1, which was fed with the NaHum additive at an intake rate of 25 mL/L. The NaHum additive modulated the ileal microbiota and metabolic processes in the broiler body. At the same time, a significant decrease in the levels of total protein, alkaline phosphatase and phosphorus (P) in blood was found in the research groups.

Conclusion

Considering the positive effects of NaHum derived from freshwater sapropel on the productivity and economic efficiency of broiler chickens, the NaHum feed additive should be further investigated on a larger scale to obtain results that could reasonably be used in practice. This study concluded that a decrease in P levels in the blood was observed when NaHum was added to the drinking water; therefore, it is important to continue the research to draw reasonable conclusions on the effects of NaHum in liquid form on the health performance of farm animals.

Stepwise Reduction of Dietary Phosphorus in Diets for Piglets and Fattening Pigs of Different Genetic Origin Housed under Various Station Environments-A Ringtest

The reduction of emissions of nutrients from livestock is one of the main topics in areas with intensive animal husbandry. In order to minimize the loss of nutrients into the environment, it is common practice to feed animals as close as possible to metabolic demands. For phosphorus (P), there are various studies for swine and poultry, which showed that a reduction of dietary P levels is possible, if a sufficient level of phytase is added to the diet. The supplementation of a sufficient dosage of phytase to plant-based diets leads to an increase in digestible phosphorus (dP) upon the hydrolisation of phytate (InsP6) to P and lower inositol-phosphates. However, most of these studies were conducted under standardized experimental conditions. In terms of transfer to practical conditions with varying housing, management and genetics, there are concerns that have led to speculation by farmers and veterinarians whether the reduction of dietary P could negatively affect bone health and therefore animal welfare. In order to test whether a reduction of dietary P according to the recommendations for dP of the German Society of Nutrition Physiology (GfE) affects bone mineralization and growth performance, a ringtest was conducted where piglets and fattening pigs were fed at four experimental stations with three centrally produced diets from the same batches. The diets contained three different levels of P and were designed to reflect practical diets. The P level decreased from diet one to three, respectively. Diets one and two were calculated to contain P levels, which are typically fed under practical conditions in Germany. The third diet was optimized to fulfill the requirements of dP by the GfE. The animals were fed in two phases as post-weaning piglets (8-15 kg and 15-28 kg BW) followed by a three-phase fattening regime (28-60 kg, 60-90 kg and 90-120 kg BW). Individual body weight and feed consumption (pen basis or individually, depending on the experimental station) were recorded for every feeding phase. At the end of the experiment, animals were slaughtered. At one experimental station, additional blood serum, metatarsi of the left leg and kidney tissue were sampled to analyze serum P concentration, expression of P transporters in the kidney and bone traits. In two experimental stations, femur and vertebra were sampled, and bone ash was determined. Overall, animal performance and all other traits analyzed did not differ between the treatment with the highest and the treatment with the lowest dietary P concentration. The results demonstrate that it is possible to decrease dietary P according to the recommendations for dP of the GfE, without impairing the animals' performance or mineral homeostasis and health. A reduction of total P by reducing mineral P to the levels of the present study require the supplementation of phytase to achieve sufficient concentrations of dP.

Comparison of mucosal phosphatase activity, phytate degradation, and nutrient digestibility in 3-week-old turkeys and broilers at different dietary levels of phosphorus and phytase

A comparison between 3-wk-old female turkeys (B.U.T. 6) and broilers (Ross 308) was performed to study the effects of species, dietary P, Ca, and phytase levels on gut mucosal phosphatase activity, myo-inositol hexakisphosphate (InsP6) degradation along the digestive tract, digestibility of P, Ca, and amino acids, and concentrations of myo-inositol in the digesta and blood. The experimental diets were corn-soybean meal-based and identical for both species. Two dietary P and Ca concentrations (CaP-: 4.1 g P/kg, 5.5 g Ca/kg and CaP+: 9.0 g P/kg, 12.0 g Ca/kg) and 2 levels of phytase supplementation (0 and 1,500 FTU/kg) were used in a 2 × 2 factorial design and fed to the animals for 7 d in their third week of age. Each diet was randomly assigned to 6 broiler and 6 turkey pens, with 10 birds each. After slaughter, blood, digesta from the crop, gizzard, duodenum, lower ileum, and mucosa from the jejunum were collected. When fed CaP- without phytase supplementation, there were no differences between species in gut mucosal phosphatase activity, prececal InsP6 disappearance, and P and Ca digestibility, indicating a similar intrinsic capacity for phytate degradation in both species. When fed CaP+ without phytase supplementation, turkeys showed higher prececal InsP6 disappearance than broilers. Phytase supplementation increased prececal InsP6 disappearance and digestibility of P and Ca in both species. However, the phytase-induced increase in prececal InsP6 disappearance was more pronounced in broilers than in turkeys, possibly due to more adequate conditions for phytase activity in the broiler crop. In broilers, phytase supplementation increased amino acid digestibility overall, whereas, in turkeys, it increased with CaP+ and decreased with CaP-. In addition, the relationship between myo-inositol concentration in the ileum and blood differed between species, indicating differences in myo-inositol metabolism. It was concluded that 3-week-old turkeys and broilers differ in nutrient digestibility and InsP degradation in some segments of the digestive tract but have similar endogenous InsP6 degradation when fed low P and Ca diets.

Effects of exogenous protease on performance, economic evaluation, nutrient digestibility, fecal score, intestinal morphology, blood profile, carcass trait and meat quality in broilers fed normal diets and diets considered with matrix value

This study was conducted to estimate the effects of exogenous protease on performance, economic evaluation, nutrient digestibility, fecal score, intestinal morphology, blood profile, carcass traits, and meat quality in broilers fed normal diets and diets considered with matrix value. A total of 90, one-day-old Arbor Acres broiler chickens were randomly allocated to 3 dietary treatments with 6 replicates and each replicate of 5 broiler chickens. Treatments were as follows: 1) Basal diet (positive control, PC), 2) Basal diet formulated with full ProAct 360 matrix at 50 g/MT without addition of ProAct 360 (negative control, NC), 3) NC + 50 g/MT ProAct 360 (PA). Supplementation of exogenous protease to nutrient deficient NC diet by matrix values (PA) tended to increase growth performance and significantly improved intestinal morphology compared with the NC group. The PA group had significantly lower fecal score, and higher ATTD of crude protein and amino acids than those of the NC group. Furthermore, supplementation of exogenous protease to NC diet decreased feed cost, resulting in improved profit margin. However, there was no significant difference on carcass yield and relative organ weight. In conclusion, supplementation of exogenous protease using matrix value could be used as economic additive to improve growth, profit margin, digestibility, and gut health in broiler chickens.

Research Note: Influence of monocalcium phosphate and phytase in the diet on phytate degradation in cecectomized laying hens

This study investigated the effects of phytase and monocalcium phosphate supplementation on the dephosphorylation of phytic acid [myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate); InsP₆] in cecectomized laying hens using total excreta collection. Four corn-soybean meal-rapeseed meal-based diets were mixed with or without 6 g of monocalcium phosphate/kg, with or without supplementation of 1,500 FTU phytase/kg, and had the same calcium concentration at 39 g/kg of feed. Each diet was tested in 5 replicates using a row-column design with 10 cecectomized laying hens in 2 periods. The hens received 120 g/d of feed while being housed individually in metabolism units, and total excreta were collected for a period of 4 d. The monocalcium phosphate × phytase interaction was not significant for InsP₆ degradation (P = 0.054). Phytase increased InsP₆ disappearance from 13% to 83% (P < 0.001), whereas monocalcium phosphate had no effect. Concentrations of most of the lower inositol phosphate isomers in excreta were higher when monocalcium phosphate was added to the diets. The concentration of Ins(1,2,5,6)P₄ in excreta was the highest among the studied partially dephosphorylated inositol phosphates with phytase supplementation and was higher than in diets without phytase supplementation (P < 0.001). Supplementation with phytase increased myo-inositol concentration in excreta (P = 0.002), whereas monocalcium phosphate had no effect. Phosphorus utilization ranged from 4% to 18% and was not significantly affected by the treatments. These results suggest that phytase supplementation markedly increased InsP₆ degradation in laying hens. The cecectomized laying hen assay may be suitable for studying the effects of phytase supplementation on phytate dephosphorylation under dietary conditions when performance and phosphorus excretion are unlikely to be affected.

Effects of different feeding regimens with protease supplementation on growth, amino acid digestibility, economic efficiency, blood biochemical parameters, and intestinal histology in broiler chickens

Background

This study was conducted to estimate the impacts of using varied feeding regimens with or without protease supplementation on the growth performance, apparent amino acid ileal digestibility (AID%), economic efficiency, intestinal histology, and blood biochemical parameters of broiler chickens. Three hundred one-day-old chicks (Ross 308 broiler) were randomly allotted to a 3 × 2 factorial design. The experimental design consisted of three feeding regimens; FR1: a recommended protein SBM diet, FR2: a low-protein SBM diet, and FR3: a low-protein diet with the inclusion of 5% DDGS and 5% SFM, with or without protease supplementation (250 mg/kg).

Results

Increased feed intake and feed conversion ratio were observed in the FR3 treatment during the starter stage and decreased body weight and body weight gain during the grower stage. However, there was no significant effect of the different feeding regimens, protease supplementation, or interaction on the overall performance. The economic value of diets also remained unaffected by the different feeding regimens, protease supplementation, or interaction. Protease supplementation resulted in lowering the AID% of tryptophan and leucine. Reduced AID% of methionine was evident in the FR2 + VE and FR3 − VE treatments. Histological findings substantiated the FR3 treatment mediated a decrease in the duodenal and jejunal villous height (VH), jejunal villous width (VW), and ileal VW, whereas, increase in the ileal crypt depth (CD). The FR2 + VE treatment reduced the VH:CD ratio in the duodenum. The duodenal CD and the jejunal goblet cell count were reduced as a consequence of protease supplementation. The FR3 + VE treatment documented a rise in duodenal CD, while an increase in the jejunal goblet cell count was observed in the FR3 − VE treatment. The FR3 treatment enhanced the IgM serum levels compared to the FR1 and FR2 treatments. IgM serum levels were also elevated following protease supplementation. FR3 + VE treatment increased IgM serum levels. The highest serum ALP was found in the FR3 treatment, whereas the lowest level was obtained in the FR2 treatment.

Conclusion

Low-protein SBM-based diets could be used without affecting the birds’ growth. Altered morphometric measures of the intestine and increased IgM and ALP levels indicated the low-protein SBM/DDGS-SFM diet-induced damage of the intestinal histoarchitecture and immune system of birds. These different diets and protease supplementation failed to affect economic efficiency positively.

Phytate degradation and phosphorus utilisation by broiler chickens fed diets containing wheat with increased phytase activity

1. The objective of this study was to investigate wheat genotypes bred for increased intrinsic phytase activity for InsP₆ disappearance and the formation of lower inositol phosphates in such wheat-fed broiler chickens. The influence of monocalcium phosphate (MCP) supplementation on these characteristics and the utilisation of P and Ca were also determined. A three-step in vitro assay and a broiler trial were performed.2. In the 63 wheat genotypes tested in vitro, phytase activity varied from 1900 FTU/kg to 5200 FTU/kg, and InsP₆ disappearance increased with higher phytase activity of wheat in a linear manner. The addition of MCP significantly reduced in vitro InsP₆ disappearance by one-third, independent of the inclusion level of wheat in the feed. When exogenous phytase was added to wheat, in vitro InsP₆ disappearance increased independently of the phytase activity of the wheat used.3. In the broiler trial, four wheat genotypes with phytase activities between 2400 and 3700 FTU/kg were included at 400 g/kg in diets with and without MCP. The diets were not pelleted. Separately, wheat 1, without MCP, was tested with the addition of exogenous phytase. Unsexed Ross 308 broiler chickens were allocated to 72 metabolic units of 10 birds each and assigned one of the nine diets. Mineral utilisation was measured based on excreta collection from 20 to 23 d of age. Digesta from the crop and terminal ileum were collected on d 24.4. In the crop and ileum, InsP₆ disappearance was not affected by the wheat genotypes, but the addition of MCP significantly decreased InsP₆ disappearance. Precaecal P disappearance was significantly reduced by the addition of MCP, with wheat genotypes exerting an effect. Wheat genotypes and the addition of exogenous phytase significantly affected P utilisation. Exogenous phytase had no effect on InsP₆ disappearance in the crop but did up to the terminal ileum, the precaecal InsP₆ and P disappearance increased with the addition of exogenous phytase.5. Although the intrinsic wheat phytase activity exerted distinct effects on in vitro InsP₆ disappearance, no such effect was found in the broiler trial. The addition of MCP significantly inhibited InsP₆ degradation in vitro and in vivo.

Phytase Supplementation Effects on Amino Acid Digestibility in Broiler Chickens are Influenced by Dietary Calcium Concentrations but not by Acid-Binding Capacity

BACKGROUND

Responses to dietary calcium (Ca) and supplemented phytase on prececal amino acid digestibility (pcAAD) in broiler chickens vary among studies. The variation may arise from the dietary acid-binding capacity (ABC) that influences the activity of enzymes in the digestive tract and from microbial activity.

OBJECTIVE

This study aimed to investigate whether the ABC influences phytase effects on pcAAD and whether microbial activity contributes to this.

METHODS

Male Ross 308 broiler chickens were provided 1 of 12 diets in 72 pens (15/pen) from day 16 of age until the end of the experiment on days 21 or 22. In a 3 × 2 × 2-factorial arrangement, the ABC was varied by replacing calcium carbonate (CaCO3) with Ca-formate or by adding formic acid to CaCO3-containing diets, and contained 5.6 or 8.2 g Ca/kg and 0 or 1500 phytase units/kg. The ileum content was collected for pcAAD measurement and microbial community composition was used to investigate whether changes in pcAAD are related to the microbiota.

RESULTS

Three-factor ANOVA showed that reducing the ABC increased pcAAD (average 1.1 percentage points) and no significant interaction of the ABC with Ca concentration and phytase supplementation including 3-way interactions. Without phytase, increasing dietary Ca concentration decreased pcAAD (average 3.1 percentage points). Phytase supplementation increased pcAAD (average 2.1 and 5.0 percentage points at low and high Ca concentrations, respectively), to reach the same level for both Ca concentrations. Microbial functional predictions pointed towards an influence of the microbiota in the crop and ileum content on amino acid concentrations, as indicated by different relative abundances of predicted genes related to amino acid biosynthesis, degradation, and metabolism.

CONCLUSIONS

Dietary Ca concentrations but not the ABC modulates the effect of supplemented phytase on pcAAD in broiler chickens. The microbiota might contribute to differences in pcAAD by changing the amino acid composition of the digesta. The extent of this effect is still unknown.

Reevaluation of Phytase Action Mechanism in Animal Nutrition

The release of phosphorus from phytates occurs via sequential cleavage of phosphate groups. It was believed that, regardless of the properties of phytases, the rate of phytate dephosphorylation is limited by the first cleavage of any phosphate group. The position of the first cleaved-off phosphate group depending on the specificity of phytase. The inhibition of dephosphorylation initiation is not associated with the action mechanism of the enzyme and can be rather due to the insufficient phytase activity or low availability of phytates. The analysis of the transformations in the inositol hexakisphosphate (IP₆)→inositol (I) reaction chain shows that IP₆ dephosphorylation as a whole limits the phosphate group removal from I(1,2,5,6)P₄ (third reaction from the beginning of hydrolysis of phosphate bonds in PA). The lower availability of nutrients in the presence of phytates is not due to action of phytates, but is caused by PA anions (IP_6-3), which bind positively charged metal ions, amino acids, and proteins. The availability of nutrients increases as a result of the decrease in their binding caused by the decrease in the concentration of IP_(6-3) anions under the action of phytases. Phytases added to feeds play a lesser role in the digestion of phytates compared to natural enzymes and complement their action. The concept of extra-phosphoric effect has no scientific justification, since phytases exhibit only the phosphohydrolase activity and are not able to catalyze other reactions.

Phytase supplementation effects on amino acid digestibility depend on the protein source in the diet but are not related to InsP6 degradation in broiler chickens

The objective was to determine phytase effects on prececal amino acid (AA) digestibility and phytate (InsP6) breakdown when different oilseed meals were used in broiler chicken diets. The study included 14 diets: a corn-soybean meal (SBM) basal diet and 6 diets that contained SBM, rapeseed meal (RSM), and sunflower meal (SFM) with 2 inclusion levels at the expense of corn starch (150 and 300 g/kg SBM or SFM, or 100 and 200 g/kg RSM). Each diet was mixed with or without a phytase supplement of 1,500 FTU/kg. Diets were provided to broilers for 5 D. Digesta from the posterior half of the ileum were collected on day 21. The average essential AA digestibility, calculated by a regression approach, without and with phytase was 84 and 85% (SBM), 74 and 77% (SFM), and 66 and 73% (RSM), respectively. In the diets, phytase effects on AA digestibility were lower owing to other protein sources also present in the diet, but significant. Prececal InsP6 disappearance was significantly affected by interactions between oilseed meal, inclusion level, and phytase supplementation. Overall, prececal InsP6 disappearance was higher in SBM diets (52%) than in SFM diets (38%) and intermediate in RSM diets (43%). Across diets, phytase supplementation effects on prececal InsP6 degradation linearly increased with the InsP6 concentration of the diet up to 12 g/kg DM. The only exception from linearity was the diet with the high inclusion of SFM, which contained 15.9 g InsP6/kg DM. In the ileal content, the concentration of myo-inositol was significantly increased by phytase supplementation, and this effect was highest in the diets that contained SBM as the only oilseed meal. Concentrations of lower inositol phosphates were increased by phytase supplementation, and this effect was most remarkable for Ins(1,2,3,4)P4 and inositol tetrakisphosphates. The study showed that phytase effects on AA digestibility varied among the 3 tested oilseed meals, but these differences were not detectable in the diets containing these meals. Although phytase effects on ileal content of InsP6 and its degradation products were substantial, they were not related to the effects on AA digestibility.

Toward standardized amino acid matrices for exogenous phytase and protease in corn-soybean meal-based diets for broilers

A total of 468 male Ross 308 broilers were used in a digestibility study to determine the additivity of apparent or standardized amino acid (AA) digestibility values for corn, soybean meal (SBM), or a mixture of corn and SBM that were supplemented, or not, with either phytase, protease, or a combination of phytase and protease. These treatments generated a total of 12 experimental diets that were arranged in a 3 × 4 design. A nitrogen-free diet was also fed to estimate endogenous AA loss. Apparent and standardized AA digestibility values were assessed on day 28 posthatch. The apparent digestibility of AA in the complete diet was higher (P < 0.05) than expected based on the digestibility of the corn and SBM individually. However, this overestimation was corrected by the adjustment to standardized values. Importantly, addition of protease or the combination of protease and phytase increased (P < 0.05) the digestibility of AA in corn and SBM. Furthermore, these effects were arithmetically coherent with respect to the measured effects of the enzymes in the mixture of corn and SBM, even improving the additivity of AA digestibility values when assessed on an apparent basis. This study demonstrates that the effect of exogenous protease and phytase on AA digestibility in complete diets is predictable based on measurements made in individual ingredients. In addition to improving digestibility values per se, exogenous protease and phytase may enhance precision in least cost formulation systems.

Growth performance, nutrient digestibility, bone mineralization, and hormone profile in broilers fed with phosphorus-deficient diets supplemented with butyric acid and Saccharomyces boulardii

The present study evaluated the effects of butyric acid supplementation and Saccharomyces boulardii (alone or in combination) on growth performance, nutrient digestibility, bone mineralization, and blood hormones of male broiler chickens fed a diet including reduced levels of nonphytate phosphorus (NPP). The chickens were allocated to 6 dietary treatments: 1) positive control diet with adequate amounts of NPP (PC; 0.48, 0.43, and 0.39% in the starter, grower, and finisher period, respectively); 2) negative control diet with low amounts of NPP (NC; 0.38, 0.33, and 0.29% in the starter, grower, and finisher period, respectively); 3) NC plus 500 FTU/kg microbial phytase (PHY); 4) NC plus 0.2% butyric acid (BA); 5) NC plus 1 × 10⁸ cfu/kg S. boulardii (SB); 6) NC plus butyric acid and S. boulardii (BA+SB). Each treatment had 5 pen replicates of 25 birds. After 6 wk, the body weight and ADG in birds fed with any of the diets were higher (P < 0.001) than those in birds fed with the NC diet, where the birds fed with the PHY and BA+SB diets had the highest values. However, only the PHY diet improved (P = 0.041) overall F:G. All diets, except the SB diet, resulted in the increased apparent ileal digestibility coefficient (AIDC) of CP, AME_n, and tibia ash content and decreased serum alkaline phosphatase level compared with the NC diet (P < 0.05). Broiler chickens fed with the PHY, SB, and BA+SB diets also had increased AIDC of phosphorus (P = 0.017) than those fed with the NC and PC diets. Feeding PC, PHY, and BA+SB diets increased (P = 0.007) the tibia phosphorus content but decreased (P = 0.033) serum parathyroid hormone concentration. Overall, the present data indicate that the simultaneous inclusion of butyric acid plus S. boulardii in the low-NPP diets was beneficial for improving growth rate and bone mineralization, but not for feed efficiency.