The interplay of dietary nutrient specification and varying calcium to total phosphorus ratio on efficacy of a bacterial phytase: 1. Growth performance and tibia mineralization

Phytate-phosphorus and phytase on performance, bone characteristics, tissue and serum mineral concentration on broilers

Male broiler chickens (384), Cobb 500, were housed in metabolic cages to assess the efficacy of phytase in diets with low and high phytate-phosphorus on the performance, bone physical characteristics, tissue and serum mineral deposits. Birds were distributed in four treatments with a 2 x 2 factorial arrangement in a completely randomized block design. Experimental diets based on maize-soybean meal were T1 - diet low phytate-phosphorus; T2 - diet low phytate-phosphorus and phytase (500 FTU/kg); T3 - diet high phytate-phosphorus; T4 - diet high phytate-phosphorus and phytase (500 FTU/kg). Feed intake, body weight, weight gain and feed conversion ratio were assessed. Two left tibias per experimental unit were analyzed for physical characteristics and mineral concentration; a section of skinless breast muscle and blood were collected to measure the concentration of calcium, phosphorus and sodium. Results showed interaction between bone stiffness and serum calcium. The inclusion of phytase in diets with low and high phytate-phosphorus did not alter performance, bone resistance and flexibility, mineral deposits in the tibia and breast muscle, but increased bone stiffness after 22 days of age. It also provided a higher serum calcium rate in broilers fed diets with low phytate-phosphorus up to 32 days of age.

Investigating possible impact, and interaction, of phytase supplementation during pre-experimental and experimental phases on assay of true phosphorus pre-caecal digestibility and total tract retention

1. Two experiments were conducted to investigate whether the use of phytase in the pre-experimental or experimental phases of true pre-caecal phosphorus digestibility (TPD) assay influenced the assayed TPD values. In experiments 1 and 2, broiler chickens were randomly allocated to 12 treatments in a 2 × 2 × 3 factorial arrangement. The factors were pre-experimental phytase supplementation (+ or -), experimental phase phytase supplementation (+ or -) with varying soybean meal inclusion levels (450, 560, or 670 g/kg).2. The diets in the pre-experimental phase were based on maize-soybean meal, whereas the diet used during the experimental phase was semi-purified, with soybean meal as the only source of P. Both TPD and true phosphorus retention (TPR) were determined using regression for the P output (g/kg, dry matter basis), pre-caecal or total tract, against P intake (g/kg). Data for TPD and TPR were analysed as a 2 × 2 factorial (with or without pre-experimental or experimental phase phytase).3. In both experiments 1 and 2, there were no significant effects for pre-experimental phytase supplementation nor interaction of pre- and experimental phytase supplementation on any of the pre-caecal digestibility responses. Phytase supplementation during the experimental phase increased (P < 0.01) pre-caecal P digestibility and retention, as well as digestible and retained P intake, and decreased (P < 0.01) P output.4. In experiment 1, pre- and experimental phytase supplementation increased (P < 0.01) the coefficient of TPR. In experiment 2, there was no significant effect of pre-experimental phytase supplementation on coefficient of pre-caecal TPD. However, phytase supplementation in the experimental phase increased (P < 0.01) the coefficient of pre-caecal TPD.5. In conclusion, whether or not phytase was supplemented to a P-adequate diet in the pre-experimental phase of the TPD assay, it had no influence on assayed TPD or TPR value.

Interactive effect of dietary calcium and phytase on broilers challenged with subclinical necrotic enteritis: 3. Serum calcium and phosphorus, and bone mineralization

Calcium is chelated by phytic acid and forms phytate-mineral complexes reducing Ca availability and the ability of phytase to hydrolyze phytate. An increased Ca concentration in the gut favors the activity of Clostridium perfringens (C. perfringens). Therefore, it was hypothesized that high dietary calcium with high dietary phytase would decrease serum Ca and P and bone mineralization during necrotic enteritis occurrence. A total of 768 one-day-old Ross 308 male chicks were randomly allocated to 8 treatments with 6 replicate pens, each housing 16 birds. A 2 × 2 × 2 factorial arrangement of treatments was applied: dietary Ca (0.6 or 1.0%), phytase (500 or 1,500 FTU/kg), and challenge (no or yes). Half of the birds (384) were challenged with Eimeria spp. on day 9 and C. perfringens strain EHE-NE18 on day 14 and 15. Blood was collected from 2 birds per pen to determine Ca, P, and parathyroid hormone in the serum. The middle toe, tibia, and femur were excised from 2 birds per pen on day 16 and 29 for determination of ash, breaking strength (BS), and mineral concentration. The challenge decreased (P < 0.05) serum Ca⁺ in birds regardless of dietary Ca level (day 16). There was a challenge × Ca interaction (P < 0.05) for tibial BS (day 16), with challenge being more severe in birds fed high Ca than low Ca diets. A challenge × phytase interaction (P < 0.05) was present for femur ash (day 16), with high phytase only increasing ash in challenged birds. The challenge decreased (P < 0.05) the BS of femur and tibia at each time point. Birds fed high dietary Ca had lower tibial Mg (P < 0.001), Fe (P < 0.001), Na (P < 0.001), and Zn (P < 0.05) concentrations (day 29). Altogether, high dietary Ca and phytase improved bone mineralization showing that attention to Ca and P nutrition and phytase matrix values is warranted when high levels of phytase are used.

Hydrolysis of phytate to its lower esters can influence the growth performance and nutrient utilization of broilers with regular or super doses of phytase

The aim of the study was to observe the effects of dietary available phosphorus (aP) and calcium (Ca), with regular or super doses of phytase, on phytate hydrolysis and subsequent influences on broiler growth performance and nutrient utilization. In a 2 × 3 factorial design, 384 Ross-308 broilers were allocated to one of 6 dietary treatments with 8 replicates in a randomized complete block design for 21 days. Diets were nutritionally adequate (positive control, PC) or marginally deficient in aP and Ca (negative control, NC), with 0, 500 or 1,500 FTU/kg phytase. Bird and feed weights were recorded on d 0 and 21, excreta were collected on d 19 and 20, and gizzard and ileal contents were collected on d 21. Body weight gain (P < 0.01) increased linearly with phytase in the PC and quadratically in the NC. There was an interactive effect on ileal DM, N, and P utilization, increasing quadratically with phytase supplementation in the NC, but there was no phytase influence in the PC (P < 0.05). Phytase linearly increased copper (P < 0.001) and linearly decreased Ca (P < 0.05) utilization in the ileum. Phytase decreased ileal (IPx, inositol x-phosphate) IP6 and IP5 and increased inositol (quadratic, P < 0.001) but had no effect on IP4 or IP3. The influence of the dietary aP was more apparent on the hydrolysis of phytate and phytate esters after the ileum, with increasing (linear and quadratic, P < 0.05) IP4 and IP3 content in the excreta of birds fed the NC or PC when phytase was added. Phytate hydrolysis improves the growth potential of birds fed NC diets, allowing them to match the growth performance of birds fed PC diets and improve nutrient utilization. These results indicate that dietary Ca and aP concentrations can be reduced when phytase is supplemented. It also may be beneficial to apply the enzyme nutrient matrix to other nutrients in the diet to maintain an optimal balance of nutrients in the digesta.

Evaluation of the effect of a highly soluble calcium source in broiler diets supplemented with phytase on performance, nutrient digestibility, foot ash, mobility and leg weakness

High inclusion concentrations of dietary calcium (Ca) from limestone may have detrimental effects on broiler performance, such as increased gastric pH and a reduction in phosphorus (P) and amino acid digestibility. To assess the potential for feeding diets with lower total Ca concentrations, the effect of a novel highly soluble source of calcium (HSC) on bird performance, nutrient digestibility and skeletal integrity of 1120 male Cobb-500 broilers was compared with that of limestone. Eight dietary treatments in a 2 × 2 × 2 factorial design consisted of two sources of Ca (limestone or HSC), two concentrations of Ca (6.0 or 7.7 g/kg in the starter and 4.0 or 5.7 g/kg in the grower), two phytase levels (0 or 500 FTU/kg). The effect of dietary treatments on growth performance and feed intake were measured from Day 1 to Day 40 and foot ash and leg health on Day 40. At the end of the starter period, in the absence of phytase, changing Ca source from limestone to HSC at 6.0 g/kg total Ca decreased both bodyweight gain and feed intake (P < 0.05). The addition of phytase to diets containing 6.0 g/kg total Ca provided by HSC increased bodyweight gain (P < 0.05), as well as increasing feed intake (P < 0.05). At the end of the grower period, diets supplemented with phytase increased bodyweight gain (P < 0.001), birds fed the higher Ca concentration were also observed to have an increased bodyweight gain (P < 0.001). Apparent ileal Ca digestibility significantly increased with the addition of phytase to diets containing 4.0 g/kg total Ca provided by HSC (P < 0.05), this was also observed for P digestibility. Replacement of limestone with HSC when fed in conjunction with phytase has the potential to be an effective strategy to improve broiler performance and bone mineralisation.

The efficacy of dietary xylanase and phytase in broiler chickens fed expeller-extracted camelina meal

A study was conducted to investigate the effects of dietary phytase (PHY) and xylanase (XYL) on growth performance, nutrient utilization, and intestinal characteristics in broilers fed corn-soybean meal-based diets with added expeller-extracted camelina meal (CM). The corn-soybean meal-based diets without or with CM was formulated to contain 2.9 or 2.7 g/kg non phytate phosphorus, respectively. A total of 384 male Ross 708 broilers were allocated to 8 dietary treatments in a randomized complete block design with 6 replicates per treatment, from 7 to 21 d post hatching. The experiment consisted of a 2 × 2 × 2 factorial arrangement of treatments with 2 dietary CM levels (zero or 100 g/kg), 2 dietary levels of XYL (zero or 800 unit/kg), and 2 dietary levels of PHY (zero or 4,000 unit/kg). Chromic oxide was included in the diets as an indigestible marker. Growth was measured throughout the experiment and excreta were collected on d 18 to 21 post hatching for measurement of nutrient and energy retention. On d 21 post hatching, broilers were euthanized by CO2 asphyxiation, ileal digesta was collected for nutrient and energy digestibility measurements, and the left tibia was removed for bone ash measurement. Furthermore, duodenal digesta was collected and a segment of the mid jejunum was excised for viscosity and morphology measurement, respectively. Broilers fed 100 g/kg CM diets showed lower (P < 0.001) BW gain and G:F than those fed zero g/kg CM diets for 7 to 14 d and 7 to 21 d post hatching periods, respectively. Phytase supplementation improved (P < 0.05) all the growth parameters measured regardless of CM addition. Phytase supplementation resulted in an increase (P < 0.05) in jejunum villus height but there was no impact of CM or XYL. Additionally, duodenal digesta viscosity increased (P < 0.001) with added CM. Tibia ash and weight increased (P < 0.001) with PHY supplementation. There was a CM × PHY interaction (P < 0.05) on percentage tibia ash, with greater PHY effect in zero g/kg CM diets compared with 100 g/kg CM diets. Phytase supplementation increased (P < 0.05) ileal DM, N, energy, P, and neutral detergent fiber (NDF) digestibility. In diets with 100 g/kg CM, addition of PHY had a greater effect (CM × PHY; P < 0.05) on ileal P digestibility compared with diet without CM. There was a CM × PHY interaction (P < 0.05) for ileal digestible energy (IDE) in which PHY increased the IDE in birds fed CM supplemented diets. Both ileal digestibility and retentions of DM, N, energy, and IDE, AME, and AMEn were decreased (P < 0.05) by CM supplementation. Retention of ether extract and NDF decreased (P < 0.05) with CM supplementation. Nitrogen retention, AME, and AMEn decreased (CM × XYL; P < 0.05) with XYL supplementation in zero g/kg CM diets. There were CM × XYL interactions (P < 0.01) for P and Ca retentions in which XYL increased retentions in 100 g/kg CM diets. In conclusion, PHY was efficacious at improving P digestibility and retention of birds fed low P corn-soy based diets without or with CM. However, regardless of CM addition, XYL did not improve nutrient utilization and growth performance of broiler chickens. The present data also show that the mechanism underlying the detrimental effects of CM inclusion on nutrient utilization is not mediated through gut morphology and goblet cell density. The data also show that the villus height increase occurring with PHY addition might be a contributor to the improvements in ileal DM, N, and energy digestibility obtained with PHY supplementation.