H. L. Classen

The effect of minerals and mineral chelators on the formation of phytase-resistant and phytase-susceptible forms of phytic acid in solution and in a slurry of canola meal

Abstract Minerals can readily bind to phytic acid and thus have the potential to form mineral–phytate complexes that may be resistant to hydrolysis by phytase activity of animal, plant and microbial origin. In simple solution, at pH 7.0, mineral concentrations from 0.053mM for Zn 2+ up to 4.87mM for Mg 2+ caused a 50% inhibition of phytate-P hydrolysis by microbial phytase. The rank order of mineral potency as inhibitors of phytate hydrolysis was Zn 2+ ⪢Fe 2+ >Mn 2+ >Fe 3+ >Ca 2+ >Mg 2+ at neutral pH. Acidification of the media to pH 4.0 decreased the inhibitory potency of all of the divalent cations tested. The inhibitory potency of Fe 3+ showed a moderate increase with declining pH. Inclusion of 25mM ethylenediamine-tetraacetic acid (EDTA) completely blocked Ca 2+ inhibition of phytate hydrolysis at pH 7. Inorganic P comprised 0.20–0.25 of the total P in a slurry of canola meal. Incubation with microbial phytase increased inorganic P up to 0.50 of total P levels. Supplementation with chelators such as EDTA, citrate and phthalate increased the efficacy of microbial phytase in hydrolyzing phytic acid. Incubation of canola meal with 100mM phthalic acid plus microbial phytase resulted in complete hydrolysis of phytate-P. Competitive chelation by compounds such as EDTA, citric acid or phthalic acid has the potential to decrease enzyme-resistant forms of phytic acid and thereby improve the efficacy of microbial phytase in hydrolyzing phytic acid.

Response of chickens fed on hull-less barley to dietary β-glucanase at different ages

Abstract A high viscosity hull-less barley with or without β-glucanase supplementation was compared to wheat in diets given to broiler or Single Comb White Leghorn (SCWL) cockerels. Both genotypes fed on the unsupplemented hull-less barley had poorer gain and feed conversion, higher digesta viscosity, slower rate of food passage and lower fat digestibility than chicks given the enzyme-supplemented hull-less barley or wheat diets. These effects were largely confined to the early growth period (0–4 weeks) and, with the exception of higher digesta viscosity, disappeared with ageing. Streptococcus faecium colonization of the upper small intestine also declined with ageing in all treatments, but chicks given unsupplemented hull-less barley tended to have higher counts than those given the enzyme-supplemented hull-less barley or the wheat diet. Older chickens were apparently better able to cope with higher viscosity induced by feeding barley. Despite the slower growth and reduced nutrient requirements of SCWL chicks, they responded in a parallel fashion to broiler stock.

Necrotic enteritis: Effect of barley, wheat and corn diets on proliferation of Clostridium perfringens type A

Necrotic enteritis, caused by Clostridium perfringens type A, is more prevalent in broilers fed wheat or barley diets than in those fed a corn diet. We compared the effects of wheat, barley and corn diets on in vitro proliferation of C. perfringens type A. Bacteria were inoculated into the supernatants delivered from either digested or non-digested barley, wheat and corn diets mixed with thioglycollate medium (1:3). Colony forming units were counted following incubation for 6 h at 40°C. There were no significant differences in clostridial proliferation among non-digested diets. Bacterial proliferation in the digested wheat and barley diets was significantly higher than in the digested corn diet. These findings suggest that the increased incidence of necrotic enteritis in broilers fed barley and wheat diets compared with those fed a corn diet may be due in part to increased clostridial proliferation associated with the wheat and barley diets, or to decreased proliferation associated with the corn diet.

Cereal grain starch and exogenous enzymes in poultry diets

Cereal grain starch utilization by poultry is affected by the grain species and grain sample within a species. The primary factors affecting starch digestion are the soluble cell-wall polysaccharides, which impede digestion of all nutrients including starch. Other factors which may affect starch utilization include the presence of anti-nutritional factors in grains, the nature of grain starch and the digestive capacity of the animal. Microbial enzymes containing appropriate carbohydrate hydrolysis activity are the most effective in improving starch utilization in cereal grains. Enzyme sources containing amylase and other activities may also be effective under specific circumstances.

The digestibility and content of amino acids in toasted and non-toasted canola meals

A study was conducted to determine the level and digestibilities of amino acids and the level of glucosinolates in toasted and non-toasted canola meal samples produced in commercial crushing plants in western Canada. A total of 26 non-toasted and 31 toasted canola meals samples were analyzed for apparent ileal amino acid digestibilities using broiler chickens between 21 and 28 d of age. Commercially toasted canola meal contained 5.6 g 16 g-1 N (range 5.3–5.9) of Lys with a digestibility ranging from 65.5 to 85.7% (mean = 78.0%). Non-toasted canola meal contained 6.0 g 16 g-1 N (range 5.7–6.3) Lys with digestibility values ranging from 87 to 92% (mean = 89.7%). Toasted canola meal had an average total digestible amino acid content (not including Tyr and Trp) of 69.6 g 16 g-1 N (range 56.6–75.6) while non-toasted canola meal had 77.6 g 16 g-1 N (range 73.1–82.0). The levels of aliphatic glucosinolates in the toasted (6.16 μmol g-1 meal, range 1.2–12.5) and non-toasted meals (10.5 μmol g-1 meal, range 7.8–15...

Effects of increasing photoperiod length on performance and health of broiler chickens

1. Broiler performance and health were compared from 0 to 42 d for lighting programmes consisting of near-continuous light 23L:1D (23L), a lighting programme where photoperiod gradually increased from 6 to 23 h between days 4 and 35 (INC) or an increasing-lighting programme with 1 h of light mid-way through the scotophase (INC + 1). 2. The increasing lighting programmes reduced growth rate and increased gain:food ratio from 0 to 21 d; INC + 1 growth rate was intermediate to the 23 L and INC treatments. From 0 to 42 d there were no differences in growth rate or gain:food ratio among lighting treatments. Males grew faster, ate more food and converted food more efficiently than females. 3. The increasing-lighting programmes (INC and INC + 1) resulted in less skeletal disease than the 23L control. The incidence of sudden death syndrome (SDS) and mortality other than SDS were numerically lower for the increasing lighting treatments. More males died as a result of SDS and were affected by skeletal defects than females. 4. In terms of health, increasing lighting programmes were superior to near-continuous light for broiler chickens.

Genotypic and environmental differences in extract viscosity of barley and their relationship to its nutritive value for broiler chickens

Sixteen barley cultivars selected for variation in extract viscosity were grown at five locations across western Canada. Differences in extract viscosity among locations were most apparent for high viscosity genotypes while those exhibiting low viscosity were more uniform across locations. Eight barley genotypes grown in a single location representing high and low viscosity traits were given to broiler chickens in a 3-week growth study. Chicks fed on low viscosity barley gained significantly faster (P < 0.01), and converted feed more efficiently (P < 0.01) than those given high viscosity barley. Two high and two low viscosity genotypes were given to chicks with or without β-glucanase (Aspergillus niger) supplementation. With no enzyme addition chicks given low viscosity barley surpassed those given high viscosity barley with respect to growth (P < 0.01) and feed conversion (P < 0.01). Enzyme supplementation improved chick performance with both barley types, however the response was greater for high viscosity barley. Performance of chicks fed on enzyme-supplemented diets was similar for high and low viscosity barleys.

The effect of β-glucanase supplementation on nutrient digestibility and growth in broilers given diets containing barley, oat groats or wheat

Abstract Nutrient availability in relation to broiler chick performance was evaluated in diets containing barley, oat groats or wheat with β-glucanase supplementation. Both growth and feed conversion of chicks (0–3 weeks) were improved significantly with enzyme supplementation for diets containing hulled or hulless barley or oat groats. No response to dietary enzyme was evident for chicks given wheat diets. Added dietary fat (1.0, 4.5 or 8.0%) also improved the performance of chicks fed on wheat or hulled barley, but results were variable when fat was added to hulless barley or oat-groat diets without enzyme. Both amino-acid and starch utilization in chicks fed on hulless barley or oat-groat diets were improved with enzyme supplementation, however, the response was less than that seen for fat digestibility. Most of the dietary fat was not derived from the cereal source indicating that β-glucan affected nutrient availability of the entire diet.

In vitro hydrolysis of phytate in canola meal with purified and crude sources of phytase

Pre-treatment conditions required to hydrolyze phytate in canola meal with crude and purified phytases were investigated. Phytase (10,000, 100,000, 340,000 U/kg Natuphos®) and the same phytase (10,000, 100,000 U/kg) that had been purified by gel filtration were added to canola meal without pH adjustment (pH 5.8, 2:1 H2O: meal). Phytate hydrolysis was incomplete after 30 and 60 min (50°C) indicating that a portion of the phytate was resistant to hydrolysis. Purified and crude phytases (10,000 U/kg) were used to hydrolyze canola meal at pH 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 5.8. Phytase was more effective between pH 3 and 5. Crude phytase was significantly more effective (P<0.0001) than purified enzyme, suggesting that non phytase enzymes facilitated the action of phytase. The levels of lower inositol phosphates in response to incubation pH were similar to phytate, suggesting that they too are susceptible to the formation of complexes which prevent hydrolysis. Complete hydrolysis with crude phytase (pH 5.0, 5000 U/kg, 50°C, 2:1 H2O: meal) in 250 g batches was accomplished within 23 h. In conclusion, a portion of the phytate in canola meal is resistant to hydrolysis by phytase. Therefore, meal pretreatment, which includes pH modification, temperature and moisture control, and the addition of phytase and other enzymes, is required for the effective hydrolysis of phytate.

Effect of cultivar and environment on the feeding value of Western Canadian wheat and barley samples with and without enzyme supplementation

The feeding value ofnine wheat cultivars grown in replicate in three locations in each of two crop years, and 14 barley cultivars grown in seven locations over three crop years was tested with or without an appropriate commercial enzyme using a broiler chick bioassay. Four pens of six male broilers were fed mash diets containing 80% of the test cereal with or without enzyme from 4 to 17 d. Digestibilities were determined using an acid insoluble ash marker at 1.1% of diet. Significant intraclass correlation coefficients between duplicate wheat samples suggested a common effect of the location, but their low to moderate values suggested the presence of random variation or variation due to unique growing conditions within location. For both wheat and barley samples, the growing location affected the feeding value of the cereal grain and subsequent broiler chick performance. Durum wheat cultivars had higher feeding values than that of other wheat classes, both with and without enzyme supplementation, and the ...