Effects of food deprivation and particle size of ground wheat on digestibility of food components in broilers fed on a pelleted diet

Prediction of wheat chemical and physical characteristics and nutritive value by near-infrared reflectance spectroscopy

1. The aims of this study were to investigate the potential of near infrared reflectance spectroscopy (NIRS) to predict the chemical and physical characteristics of wheat and also to predict the nutritive value of wheat for broiler chickens. 2. A total of 164 wheat samples, collected from a wide range of different sources (England, Northern Ireland and Canada), varieties and years, were used in this study. 3. Chemical and physical parameters measured included specific weight, thousand grain weight, in vitro viscosity, gross energy, nitrogen, neutral detergent fibre (NDF), starch, total and soluble non-starch polysaccharides (NSP), lysine, threonine, amylose, hardness, rate of starch digestion and protein profiles. 4. A total of 94 wheat samples were selected for inclusion in three bird trials and included at 650 g/kg in a typical UK starter/grower diet. Birds were housed in individual wire metabolism cages from 7 to 28 d and offered water and food ad libitum. Dry matter intake (DMI), live weight gain (LWG) and gain:feed ratio were measured weekly. A balance collection was carried out from d 14 to 21 for determination of apparent metabolisable energy (AME), ME:gain and dry matter retention. At 28 d the birds were humanely killed, the contents of the jejunum removed for determination of in vivo viscosity and the contents of the ileum removed for determination of ileal dry matter, starch and protein digestibility. 5. The wheat samples were scanned as whole and milled wheat, both dried and undried and NIRS calibrations, first excluding and then including the Canadian wheat samples, were developed. 6. NIRS calibrations for milled wheat samples may be useful for determining specific weight (R(cv)(2) = 0.75, for milled wheat dried), nitrogen (R(cv)(2) = 0.983 for milled and dried) and rate of starch digestion (R(cv)(2) = 0.791 for milled, dried and undried). 7. NIRS calibrations for whole wheat samples (undried) may be useful for determining wheat nutritive value, with good predictions for live weight gain (R(cv)(2) = 0.817) and feed conversion efficiency (R(cv)(2) = 0.825). 8. Inclusion of the Canadian wheat samples in the NIRS analysis provided additional robust calibrations for gross energy (R(cv)(2) = 0.86, dried and milled) and starch content (R(cv)(2) = 0.79, undried and milled). 9. This study shows that NIR is a useful tool in the accurate and rapid determination of wheat chemical parameters and nutritive value and could be extremely beneficial to both the poultry and wheat industry. 10. Further extension of the dataset would be recommended to further validate these findings.

Influence of particle size and microbial phytase supplementation on the performance, nutrient utilisation and digestive tract parameters of broiler starters

The aim of the present experiment was to examine the interaction between particle size and microbial phytase supplementation on the performance, nutrient utilisation and digestive tract development of broiler starters fed maize-based diets. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating two maize particle sizes (medium and coarse) and two levels of phytase supplementation (without or with 500 phytase units/kg diet). The two particle sizes were achieved by grinding the whole maize in a hammer mill to pass through 3- and 7-mm screens, respectively. Broiler starter diets, based on maize and soybean meal, were formulated to meet recommended requirements for major nutrients, except phosphorus. Each of the four diets was fed ad libitum to six pens of eight male broilers each, from day 1 to day 21 post-hatching. Phytase supplementation increased (P < 0.001) the feed intake and weight gain, and lowered (P < 0.05) feed per gain in both medium and coarse particle size diets. Coarse grinding improved (P < 0.05) weight gain, but had no effect (P > 0.05) on feed intake and feed per gain. No interactions (P > 0.05) between phytase supplementation and particle size were observed for any of the performance parameters. Phytase supplementation increased (P < 0.001) ileal phosphorus digestibility and toe ash content of birds fed the medium particle size diet, but had no effect in those fed the coarse particle size diet. Apparent metabolisable energy and ileal digestibility of calcium and nitrogen were not influenced by particle size or phytase supplementation. The present findings suggest that the effectiveness of supplemental phytase on broiler performance is not influenced by the particle size of maize.

Effects of two wheat cultivars on physico-chemical properties of wheat flours and digesta from two broiler chicken lines (D+and D−) differing in digestion capacity

1. The current experiment is the second part of a study about the effects of wheat quality on digestibility of pelleted diets for broiler chickens. In the first part, it was shown that a hard cultivar resulted in a negative effect on starch digestibility in two divergent lines of chickens (D+ and D-) selected for digestion capacity. The aim of this second part was to investigate the reasons for this negative effect of a hard cultivar (Baltimor) compared to a soft one (Scipion) in D+ and D- lines. 2. Proventriculus pepsin activity and pancreas proteolytic and amylolytic activities were estimated in 4 pools of birds: 'D+ line (Baltimor fed)', 'D+ line (Scipion fed)', 'D- line (Baltimor fed)' and 'D- line (Scipion fed)'. Results suggested the greatest amount of pepsin units per g BW for D+ birds and the lowest amount of pancreas proteolytic units per g BW for D+ birds fed Scipion wheat. Pancreas showed very similar alpha-amylase activities among treatments. 3. In vitro hydrolyses of wheat gluten proteins with proventriculus extracts from pools of D+ and D- birds did not show any differences between hard and soft cultivars, whatever the origin of pools. 4. Pepsin hydrolysis of fine (300 to 425 microm) and coarse (1180 to 1600 microm) fractions from wheat flours (Baltimor or Scipion) showed that the 30 min proteolysis rate was highest for the fine fraction in both cultivars. No difference was observed with extended hydrolysis time. 5. In vitro digestion simulation of whole wheat flours confirmed the results previously obtained in vivo, with a negative effect of hard cultivar on starch digestion rate and no effect on protein digestion. 6. Laser particle size analyses showed that ileum digesta from birds fed with hard wheat cultivar showed the highest proportion of coarse particles. 7. Microscopic analyses of D+ ileum digesta revealed that the concentration of undigested starch granules in the subaleurone area of wheat bran particles was the highest with hard cultivar. 8. The results suggested that physical entrapment of starch granules in coarse particles was a major explanation for decreased starch digestibility values in chickens fed hard wheat diets.

Apparent nutrient digestibility and excreta quality in African grey parrots fed two pelleted diets based on coarsely or finely ground ingredients

A feeding trial was performed to study the influence of particle size in extruded parrot pellets on apparent digestibility and excreta consistency and pH. Two test diets were alternately provided to eight African grey parrots according to a 2 x 2 cross-over design. Both diets were similar in nutrient content and ingredient composition but differed in particle size of the composing particles of individual pellets. Apparent digestibility of macronutrients was studied using the total collection method. Next, the appearance of the excreta was studied by calculation of weight-surface ratio of individual excrements as an objective measurement of consistency. Last, excreta pH was measured directly on fresh excrements and on homogenized 10% excreta solutions. Neither apparent digestibility coefficients nor excreta pH values were significantly different in parrots fed the two diets. However, excreta consistency was significantly (p < 0.05) more solid when fed the coarse diet than when fed with the finely ground diet. The results of this study suggest that excreta consistency can be improved through larger particle size, without adverse effects on nutritive value of the diet.

Effects of wheat quality on digestion differ between the D+ and D- chicken lines selected for divergent digestion capacity

The aim of the experiment was to study the effects of 2 wheat cultivars (Baltimor and Scipion) with different hardness values (75 and 5, respectively) on 2 divergent lines (D+ and D-) of broiler chickens selected on the basis of their digestion ability assessed by AME(n). Wheat was incorporated at 54.6% in diets. The other main ingredients were soybean meal (35.3%) and rapeseed oil (5.5%). Diets were given as pellets from 7 to 26 d. The experimental design was a 2 x 2 factorial design testing 2 wheat cultivars (soft or hard) on 2 selected lines of broiler chickens (high AME(n) or low AME(n)). From 7 to 16 d, D+ line showed lower (P < 0.0001) feed intake and feed:gain ratio than the D- line. At 3 wk of age, the D+ chickens resulted in increased digestibility values (P < 0.01) and 9% increased AME(n) value (P < 0.0001) compared with D-. Wheat cultivar effects on feed efficiency and AME(n) differed between lines. In the D+ line, their values were about 6% higher (P < 0.05) with soft than with hard wheat, whereas they did not differ in the D- line. However, wheat cultivar effect on starch digestibility did not differ between lines; soft instead of hard wheat resulted in about 6% improvement (P < 0.0001) in both lines. In the D- line, soft instead of hard wheat tended to reduce lipid and protein digestibilities, which explained why the starch digestibility improvement due to soft wheat was not converted into a significant AME(n) improvement in D birds. Study of digestive organ size revealed that increased proventriculus and gizzard weight (P < 0.05) could be one of the causes for the better digestion capacity of the D+ line. The pancreas was bigger (P < 0.01) in D- than in D+ birds, which probably came from an adaptation to a digestive disorder in D- birds.