Abstract An 18-d study evaluated the effect of increasing phytase levels in diets with limestone or Ca-formate on Ca and P digestibility, P retention, and blood inositol, Ca, and P in weaned piglets. At weaning, male piglets [n = 60; 29.8 ± 1.10 d of age; initial body weight (BW) = 8.8 ± 0.31 kg) were randomly allocated to ten diets formulated as a 2 × 5 factorial design with 2 primary Ca sources (limestone or Ca-formate) and 5 Ca/P levels. There was a positive control diet (PC; 0.76% Ca, 0.34 dP) and 4 negative control diets (NC; 0.56% Ca, 0.34% dP) supplemented with phytase at 0, 750, 1,500, and 3,000 FYT/kg. At d 10, piglets were individually housed in metabolism crates and fed 3.2 x metabolic weight. On d 14 to 18, fecal and total urine samples were collected. Apparent total tract digestibility (ATTD) was calculated for dry matter (DM), organic matter (OM), crude protein (CP), ash, Ca, and P using TiO2 as marker. Urinary P was measured to calculate P retention. These data were analyzed as a 2-way interaction. On d 0 (baseline), 8 and 18, blood samples were collected to analyze serum Ca and P, and plasma inositol. Blood data were analyzed as a 3-way interaction. Results indicated that piglets fed Ca-formate had greater ATTD of Ca (75.0% vs. 71.4%, P < 0.01) but decreased ATTD of P (66.4% vs. 68.8%, P < 0.01), than piglets fed limestone. Phytase supplementation improved ATTD of DM, ash, OM, CP, P, and Ca compared with the NC and PC. An interaction between Ca/P levels and Ca-sources was observed for urinary P (P = 0.03), as there were no differences between Ca sources in piglets fed the NC or the 750 FYT diets, but piglets fed the PC diet and the NC+1,500 or 3,000 FYT with limestone had greater urinary P compared with Ca-formate. A 2-way interaction between Ca/P levels and d was observed for plasma inositol (P = 0.012). On d 8 and 18, there was no difference between the NC and PC;, however, phytase supplementation at 750, 1,500, and 3,000 FYT increased plasma inositol on d 8 (58.2, 80.7, and 89.5 μmol) and d 18 (70.2, 85.4, and 106.4 μmol). There was only a main effect of Ca/P levels in serum P. Compared with the NC (73.7 mg/L), the PC and the NC+750, 1,500, and 3,000 FTU/kg increased serum P (90.3, 89.1, 87.6, and 93.2 mg/L, respectively, P < 0.01). There was no effect of Ca source on blood inositol and P. No significant dietary treatment effects were observed in serum Ca. In conclusion, using Ca-formate instead of limestone increases Ca digestibility but reduces P digestibility, likely due to a greater Ca solubility of Ca-formate. This suggests that diets should be formulated based on digestible Ca instead of total Ca.

Carbohydrates are the main components of cereal grain ingredients and are comprised predominantly of starch which varies in the rate and extent of digestibility, and non-starch polysaccharides (NSP) from plant cell walls. These components are traditionally measured by chemical methods but there is interest in developing more rapid, cost effective predictions by use of near infrared reflectance spectroscopy (NIRS) technology. In this study, around 400 samples of wheat, corn, barley, wheat bran, oats, rye, corn germ, and sorghum were collected over several years to develop global NIR calibrations. Chemical analysis was performed for NSP, including details on solubility and individual constituent sugars, as well as separate determinations of cellulose and lignin. Total starch content and starch digestibility were characterized by the method of Englyst as rapidly (RDS) and slowly (SDS) digestible starch, and resistant starch (RS) determined as total starch content minus RDS and SDS. The same samples were scanned (400 to 2500 nm, every 0.5 nm) by two NIRS machines: a Foss model DS2500 and a Bruker Tango FT-NIR (Fourier transform near-infrared spectroscopy). The NIRS calibrations were developed by using the combined set of different cereal grains. The modified Partial Least Squares Regression method was employed to establish correlations between the reference chemical analysis and the collected NIRS spectra. The correlation between the NIRS and reference data for total and insoluble NSP and the main component sugars (arabinose, xylose, and glucose) were robust (R2 = >0.97) with a 1-VR > 0.96 and RPD values > 5.3. Similarly, the NIRS predicted lignin (R2 = 0.94; 1-VR = 0.93) and to a lesser extent cellulose (R2 = 0.70; 1-VR = 0.98) but still highly correlated with the reference data. The predicted total starch content was excellent (R2 = 0.99; 1-VR = 0.99). The NIRS prediction for RDS and SDS were lower in linearity (R2 = 0.81 and R2 = 0.97, respectively) but more than sufficient to provide an estimate of the starch digestion profile for many of the raw materials evaluated. In addition, the robust NIRS predictions for total starch content, RDS and SDS could then provide information to calculate the RS fraction of the ingredients. In conclusion, compared with the reference chemical data for this large set of cereal grains the global NIR calibrations developed provide a good prediction of NSP, monosaccharide sugars, lignin, cellulose , total starch content in cereal grains , for the first time an NIR relationship with starch digestibility fractions in the grains has been shown.

Changes in small intestine digestion kinetics and early enzymatic hydrolysis in the crop attributable to xylanase supplementation has not previously been thoroughly studied in relation to animal performance. The current paper reports the effects on broiler performance of a commercial mono-component GH11 xylanase added to normal and high viscous wheat-based broiler diets with emphasis on the site of early enzymatic hydrolysis as indicated by nutrient digestibility kinetics, and visual cereal cell wall degradation. The study was conducted using 2850 1-day old male Ross 308 broilers, allocated to 5 dietary treatments: (1) positive control, an optimized diet based on wheat, soy and corn; (2) negative control; (3) negative control of high viscosity; (4) negative control supplemented with xylanase; (5) negative control of high viscosity supplemented with xylanase. Both negative control and negative control high viscosity diets were reduced in apparent metabolizable energy (starter 3.3 %, grower 7.0 % and finisher 8.5 %) as well as digestible amino acids compared to the positive control, achieved by substituting corn for rye and wheat-coproducts. The xylanase was supple-mented at 150 FXU/kg to treatment 4 and 5. Each treatment was fed ad lib to 19 replicated pens of 30 birds. The BW, feed intake (FI) and FCR were measured from d0-35 and intestinal viscosity and nutrient digestibility on d28. Statistical comparisons were performed using a mixed model. All negative controls had higher FI than the positive control regardless of xylanase supplemen-tation. The negative control with high viscosity supplemented with xylanase had an increased BW at d35 compared to all other treatments. The xylanase improved d35 FCR compared to the unsupplemented diets resulting in a European efficiency factor similar to the positive control. Microscopy of digesta samples helped visualize that the exogenous enzymatic degradation of the cereal cell wall components commenced already in the crop and increased throughout the in-testinal tract. This was accompanied by reduced jejunal and ileal digesta viscosity for the xylanase supplemented treatments. Depending on diet, the xylanase improved jejunal, but not ileal, digestibility of several nutrients including starch and protein. In conclusion, it is suggested that improved growth performance is caused by an array of multifactorial effects such as viscosity reduction, cell wall degradation and changes in the intestinal site of digestion. The current results display the potential of using xylanase in diets containing what is generally considered as lower quality arabinoxylan rich feedstuffs.