Factors affecting wheat nutritional value for broiler chickens

In Europe, broiler chickens are fed with balanced diets where the energy is mainly supplied by wheat. The feed industry considers wheat a moderately uniform raw material and therefore its energy content and nutrient digestibility are taken from feeding tables (tabulated values) and assigned to all wheat grains. However, all major wheat-producing countries report considerable variability in energy content of wheat which invalidates the assumption of uniformity among wheat grains and forces the industry to look for the factors responsible of the variation. This PhD has focused on the study of factors that affect the nutritional value of wheat for broiler chickens. After the literature review, few nutrient components of the wheat grain (starch and non-starch polysaccharides) where selected and deeper studied in different wheat cultivars fed to broiler chickens. Emphasis was put on the rate of wheat starch digestion by broiler chickens and its effect on broiler performance

Variability in wheat: factors affecting its nutritional value

Wheat is a common raw material used to provide energy in broiler diets. Its apparent metabolisable energy and its influence on broiler performance varies between wheat samples. Reasons for that variability can be classified as intrinsic (variety, chemical composition) and extrinsic factors (growing conditions, storage, etc.), both of which affect nutrient digestibility and availability. However, these factors are not always considered when formulating the diets for broiler chickens. Moreover, research through the years has questioned the relation between wheat AME and animal performance. This review aims to describe factors that influence the observed variability in wheat nutritive value for broiler chickens by considering origin (variety, growing conditions and post-harvest storage), chemical composition of the grain (carbohydrates and protein) and the broiler chicken

Effect of wheat cultivar and enzyme addition to broiler chicken diets on nutrient digestibility, performance, and apparent metabolizable energy content.

A total of 5,000 one-day-old male broiler chickens were assigned to 8 different treatments in a 4 x 2 factorial design. Four wheat cultivars (Amiro, Guadalupe, Isengrain, and Horzal) and 2 levels (0 or 1 kg/t of feed) of an enzyme cocktail (Avizyme 1300, xylanase, 2,500 U/kg and protease, 800 U/kg) were used. Nutritionally complete mash diets contained 65 and 70% of the test wheat for the starter and grower period, respectively. Test wheats were used in diets for broilers, and growth performance and AME contents were measured. Broiler performance was measured in 4,800 broilers allocated to floor pens with 75 birds each and fed from 1 to 42 d of age. Digestibilities and AME contents of diets were measured in 200 broilers from 6 to 27 d of age individually allocated to battery cages. Chromic oxide (Cr2O3) at an inclusion rate of 0.5% in the diet was used as an indigestible marker. Apparent metabolizable energy was corrected by zero N balance to obtain AMEn. Wheat cultivar strongly influenced animal performance during the starter period (1 to 21 d of age). During the grower period (21 to 42 d of age), only BW and daily feed intake were influenced by wheat cultivar. Differences in daily feed intake were associated with differences in AMEn intake during the starter period, but not during the grower period. Nutrient digestibility was higher with the use of enzyme. Animal performance was not affected (i.e., wheat cultivar differences were not eliminated by using enzymes). During the grower period, significant interactions were detected with regard to nutrient digestibility and AMEn. Differences in AMEn content of wheat could not be explained by digestible starch

Wheat starch digestion rate in broiler chickens is affected by cultivar but not by wheat crop nitrogen fertilisation

1. A study was set up to investigate the influence of wheat cultivar and wheat crop nitrogen (N) fertilisation on starch (ST) digestion rate in broiler chickens. A total of 288 broiler chickens were used in a 3 2 factorial design with diets based on three varieties of wheat (Apache, Caphorn and Charger), each grown at two N application rates (40 and 170 kg of N/ha). 2. Starch digestion rate was determined by measuring the remaining starch and the mean retention time (MRT) in 4 segments of the small intestine (proximal and distal jejunum and proximal and distal ileum) and in excreta, using chromic oxide as a marker. 3. Varietal differences in starch content (714-746 g starch/kg DM) were smaller than differences caused by crop N fertilisation (705-755 g starch/kg DM). Nitrogen application increased wheat crude protein (CP) content from 94 to 130 g/kg DM. 4. The majority of the ST in all diets was digested by the time the digesta reached the distal ileum (average 0·84 in the distal jejunum and 0·96 in the proximal ileum). 5. Starch digestion differed among wheat cultivars in the proximal jejunum (from 0·43 to 0·57, P <0·001). Afterwards no differences due to wheat cultivar or N fertilisation were found. 6. Starch digestion rate varied among wheat cultivars (from 2·45 to 3·28 h-1, P <0·001), but did not vary with N fertilisation, whereas dietary CP digestion rate was not affected by wheat cultivar or N fertilisation level. The digestion rate of ST was faster than that of CP (average 2·78 vs. 1·53 h-1). 7. The current study suggests that wheat cultivars can be classified on their rate of ST digestion independently of the N fertilisation applied to the crop during growt

Wheat starch digestion rate affects broiler performance

Two experiments were conducted to determine the differences in starch digestion rate (KDS) among wheats from different cultivars and origins and to verify if chickens would benefit from a certain digestion rate of starch. In the first experiment, 192 chickens (21 d) were assigned to 4 diets containing 55% of each wheat sample (3 cultivars, one of them from 2 origins). Starch and protein digestion were calculated from the remaining starch and protein in 4 segments of the small intestine and in excreta, using chromic oxide as a marker. Mean retention time was measured in each segment, which enabled calculations of digestion rates. In the second experiment, 2,600 chickens were assigned to 5 isoenergetic and isonitrogenous diets (with KDS from 1.80 to 2.56 h–1) and growth performance was determined (1 to 34 d). In 3 treatments, dietary starch was provided each by the wheat cultivars (same origin), whereas in the other 2 treatments, 25 and 50% of the wheat starch with the highest KDS was substituted by pea starch. Clostridium perfringens and Lactobacillus in the cecal chyme and glucose in the blood (glycemic index) were measured in broilers at d 19 and 25, respectively. Starch was gradually digested along the small intestine, mainly in the jejunum (48.5 and 80.4% at proximal and distal jejunum) where the largest differences among wheat samples were found. Starch digestion rate varied with origin (from 1.96 to 2.56 h–1) and cultivar (from 2.17 to 2.56 h–1). Crude protein digestion rate (average 2.21 h–1) was not affected by either cultivar or origin. Broiler growth and feed conversion ratio improved in a quadratic way with KDS. The maximum broiler performance was observed with KDS around 2.2 h–1. Blood glucose response (glycemic index) was not affected by KDS; therefore, it cannot be used to predict broiler performance. In conclusion, the rate of starch digestion varies among wheats, depending on both genetic and environmental conditions of the grain, and affects broiler performanc