Phytate degradation and phosphorus digestibility in broilers and turkeys fed different corn sources with or without added phytase.

The aim of the present study was to test whether different dietary corn sources and phytase supplementation affect the prececal phosphorus digestibility (pcdP) and appearance of inositol phosphates in the lower ileum of growing broiler chickens and turkeys. Two experiments were conducted, one with broiler chickens and one with turkeys. Four corn diets were provided; these were formulated to contain low P and calcium (Ca) contents and incorporated 43% of one of the four different corn sources. Diets were either unsupplemented or supplemented with 500 FTU of an Escherichia coli-derived phytase/kg feed. Experimental diets were fed ad libitum from day 20 post-hatch. At 28 d of age, digesta were sampled from the lower ileum of animals to determine pcdP and pc myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) degradation and to analyze the concentrations of lower inositol phosphate isomers. The pcdP of non-supplemented diets ranged from 51 to 60% and from 22 to 28% in broilers and turkeys, respectively. A negative correlation was observed between the InsP6 content of the corn source and the pcdP of diets in broilers only. Without phytase supplementation, pc InsP6 degradation ranged from 64 to 76% in broilers and from 6 to 15% in turkeys. Phytase increased the pcdP by around 15% in broilers (P < 0.001) and 9 to 17% in turkeys (P < 0.001). In turkeys, phytase efficacy was greatest when the diets contained corn with higher contents of ether extract and InsP6. An effect of corn source on the appearance of lower InsPs in the ileal digesta was found in broilers only. These results suggest that broilers possess a greater capacity for InsP6 degradation and hydrolysis of lower InsPs compared with turkeys. Furthermore, the results are influenced by the corn source used. Further research is needed to identify the factors responsible for the low level of phytate degradation in turkeys in order to improve the availability of InsP6-P and the efficacy of phytase.

Effect of supplemental phytase and xylanase in wheat-based diets on prececal phosphorus digestibility and phytate degradation in young turkeys.

This study aimed to investigate the effect of phytase and a combination of phytase and xylanase on the prececal phosphorus digestibility (pcdP) of wheat-based diets in turkeys. A low-P basal diet (BD) based on cornstarch and soybean meal, and 2 diets containing 43% of different wheat genotypes (genotype diets GD6 or GD7) were fed to turkeys from 20 to 27 d of age. Diets were fed either without enzyme supplementation or supplemented with phytase (500 FTU/kg) or a combination of phytase and xylanase (16,000 BXU/kg). At 27 d of age, digesta were sampled from the lower ileum of animals to determine pcdP and pc myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) disappearance, and to analyze the concentrations of lower inositol phosphate isomers. Similar pcdP was observed in non-supplemented BD and GD (∼36%). Phytase alone increased the pcdP in all diets by 8 to 12%, but a beneficial effect of xylanase was found only for BD. Similar results were found for pc InsP6 disappearance, although xylanase addition compared to phytase alone decreased pc InsP6 disappearance in GD7 compared to phytase alone. Animals fed GD7 performed better than those fed GD6; however, these differences could not be linked to the pcdP. The pattern of lower inositol phosphates in digesta also changed with enzyme supplementation, resulting in lower proportions of InsP5 and higher proportions of InsP4. Phytase alone decreased Ins(1,2,3,4,6)P5 but increased D-Ins(1,2,3,4,5)P5 and D-Ins(1,2,5,6)P4 concentrations. An additional increase in D-Ins(1,2,3,4,5)P5 and D-Ins(1,2,5,6)P4 concentrations was achieved with xylanase, although for the former isomer, this was observed only with GD. These results indicate that enzyme supplementation alters the pc degradation of InsP6, and that combining both enzymes had a minor additional effect on the pcdP from wheat-based diets when compared to phytase alone.

Variability of prececal phosphorus digestibility of triticale and wheat in broiler chickens.

The aim of this study was to evaluate the P digestibility of different wheat and triticale genotypes in growing broiler chickens. Additionally, the relationships between physical or chemical properties of genotypes and P digestibility were determined. A low P, low Ca basal diet based on cornstarch and soybean meal was supplemented with 20% or 40% of 8 different wheat or triticale genotypes at the expense of cornstarch. Experimental diets were fed to broilers between d 20 and 26 of age before digesta samples were collected from their lower ileum for determination of prececal P digestibility (pcdP). Triticale-based diets had an average pcdP of 54%. Neither the concentration of triticale nor the genotype itself affected the pcdP of diets. The pcdP of triticale genotypes calculated by linear regression analysis ranged from 53% to 78%. No correlations were found between physical or chemical properties (viscosity, phytase activity, total and phytate P contents) and the pcdP of triticale genotypes. In contrast, a significant (P < 0.05) effect of genotype and wheat concentration was observed in wheat-based diets. The average pcdP of diets decreased from 60% to 50% by increasing the wheat concentration from 20% to 40%. As no linear relationship was observed between P intake and the amount of pcdP in the diet, the pcdP (%) of wheat genotypes was calculated separately for both concentrations, and accounted for 38% to 67% and 20% to 38% with 20% and 40% wheat inclusion in diets, respectively. Single chemical and physical characteristics could not explain the observed differences in P digestibility. Our results revealed a high variation in the pcdP of different wheat and triticale genotypes that should be considered in diet formulation. However, further research is needed to identify factors that contribute to variation of P digestibility in both grains.

Influence of 4-week intraduodenal supplementation of quercetin on performance, glucose metabolism, and mRNA abundance of genes related to glucose metabolism and antioxidative status in dairy cows.

Quercetin has been shown to be a potent antioxidant, acts hepatoprotectively, and affects glucose and lipid metabolism in monogastrics. If this is also true in ruminants, quercetin could be beneficial in periparturient high-yielding dairy cows by ameliorating the negative effects of free radical formation and reducing the severity of liver lipidosis and ketosis. In a first attempt to evaluate effects of a long-term quercetin treatment, we intraduodenally administered twice daily 18 mg of quercetin (Q)/kg of body weight to 5 late-lactation (215d in milk) dairy cows over a period of 28 d. Frequent blood samples were taken before and during administration to determine plasma concentrations of flavonols and metabolites. Before and after 1 and 4 wk of Q administration, glycogen and fat content as well as mRNA expression of selected genes were measured in liver biopsies. Furthermore, euglycemic, hyperinsulinemic, and hyperglycemic clamp studies were conducted before and after 2 wk of Q administration. During the experiment, dry matter intake and most other zootechnical data remained unchanged. Milk protein content was increased in wk 2 and 4 of Q administration compared with basal values, whereas fat and lactose contents of milk remained unchanged. Plasma nonesterified fatty acids, γ-glutamyl transferase, cholesterol, glutamate dehydrogenase, triglyceride, and albumin concentrations, as well as liver fat and glycogen concentrations, were not affected by Q supplementation. Plasma glucose and ß-hydroxybutyrate concentrations in plasma decreased and increased, respectively, under the influence of quercetin. During hyperglycemic clamp conditions, the relative increase of plasma insulin was higher after 2 wk of Q administration, and a tendency for an increased rQUICKI (revised quantitative insulin sensitivity check index) was observed. The relative mRNA expression levels of selected genes related to glucose metabolism, fat metabolism, and antioxidative status were not altered after 1 or 4 wk of Q supplementation. In conclusion, the effects on insulin release and sensitivity support the assumption that administration of Q could have positive effects on the metabolic adaption of high-yielding cows to early lactation. The increase of milk protein content in response to Q supplementation needs to be verified.

Bioavailability of quercetin from its aglycone and its glucorhamnoside rutin in lactating dairy cows after intraduodenal administration.

Because of their health-promoting properties, flavonoids are used in feed supplements for ruminants, although scientific evidence for their efficacy in vivo is limited. It has been shown recently that bioavailability of quercetin is low after ruminal administration in cows because of degradation by the ruminal microbiota. It is unknown whether quercetin could be absorbed from the small intestine in ruminants if degradation is prevented; therefore, we investigated the bioavailability of quercetin after duodenal administration in 6 German Holstein cows. On 88 ± 3 d in milk, each cow received equivalent doses of quercetin [9, 18, or 27 mg of quercetin equivalents (QE)/kg of body weight] either as quercetin aglycone (QA) or as its glucorhamnoside rutin (RU). In addition, 2 control studies with duodenal administration of NaCl solution (0.9%) were conducted per cow to examine concentrations of flavonoids in plasma during regular feeding. Blood samples were collected at defined time intervals over a period of 24h before and after administration of the test compounds. A washout period of 2d was applied between the runs to avoid possible carryover effects. Concentrations of plasma quercetin aglycone and its metabolites isorhamnetin, tamarixetin, and kaempferol were measured after treatment with glucuronidase/sulfatase by HPLC with fluorescence detection. After administration of RU, levels of plasma quercetin did not increase above baseline, irrespective of dose administered. After duodenal administration of QA, the plasma concentration of QA and its methylated metabolites clearly increased above baseline. The maximal plasma concentrations of total flavonols (about 2h after application) increased in a dose-dependent manner but showed high interindividual variability (range 368.8 to 983.3 nmol/L at 27 mg of QE/kg of body weight) but peak time did not differ. Preadministration baseline values of total flavonols were reached again 3 to 4h after QA administration. The bioavailability of quercetin and its metabolites, as measured by the area under the concentration-time curve, was affected by the quercetin source applied, whereby quercetin from RU was unavailable. Taken together, duodenal administration enhanced bioavailability of QA almost to values previously reported in pigs after oral administration of QA. In contrast to findings in monogastrics or after oral administration in cows, quercetin from RU seems to be unavailable when administered duodenally.