Objective: This experiment was conducted to assess the beneficial effect(s) of β-mannanase (Lycell® and Hemicell®) supplementation to low energy diet on productive performance, gross energy digestibility, hematological parameters and carcass traits of broiler chicks. Materials and Methods: A total of 540, day old Ross 308 broiler chicks, obtained from local hatchery with mean body weight of 33±0.05 g, were randomly assigned to three dietary treatments, 180 birds each. The treatments were T1 (low energy diet, 80 kcal kg1, as control), T2 (low energy diet +250 g t1 β-mannanase from Lycell® product) and T3 (low energy diet +300 g t1 β-mannanase from Hemicell® product). The parameters recorded were growth performance, carcass traits, haematological and blood biochemical parameters, dropping and litter microbiology, gut histomorphology and digestibility trial. Results: Results demonstrated that β-mannanase improved growth performance (p<0.05) in terms of body weight, weight gain, feed intake and feed conversion ratio from three to five weeks of age. Carcass traits criteria including dressing weight, dressing percentage, and abdominal fat were significantly (p<0.05) affected by β-mannanase while gizzard, heart and spleen weight were not affected by the dietary treatments. Moreover, the dietary treatments did not affect the dry matter digestibility (DMD) and organic matter digestibility (OMD) of broiler. Conclusion: β-mannanase enzymes, either Lycell® or Hemicell®, supplementation should be considered when low energy diets are formulated in broiler.
M.M. Hashim, S.A. El-Safty, K.G. El-Eraqi, H.M.R. El-Sherif, T. Azza, K. Marwa, H.M. Ibrahim and A.Y.M. Abdelhady, 2020. Effect of β-Mannanase Enzymes Supplementation to Energy Deficient Diets on Productive Performance, Physiological and Carcass Traits of Broilers. International Journal of Poultry Science, 19: 455-466.
About 80% of the birds’ diets are made up of ingredients from plant origin containing non-starch polysaccharides (NSPs) in the plants cell wall. Among NSP, β-mannans can be considered as the leading molecules and are the most prevalent in a wide variety of feed ingredients including soybean meal, which is the major protein source in feeds produced around the world1.
The β-mannans have the ability to bind large quantity of water which subsequently results in an increase in the digesta viscosity, decrease in the diffusion of digestive enzymes and stimulates proliferation of bacteria inside the gastrointestinal tract2. Higher digesta viscosity also results in poor enzyme substrate interaction and thus reduces nutrient availability to the birds3. β-mannans is an anti-nutritional fiber and reduces metabolizable energy and nitrogen retention and increase fecal output of birds4.
In practice, the poultry diets supplementation with exogenous enzymes is a universal strategy to improve nutrient utilization, growth performance and thus reduce feed cost5. Dietary β-mannanase supplementation is responsible for the hydrolysis of β-mannans, thus reduce intestinal viscosity, promote better nutrient digestibility and absorption in the gut and improve feed conversion6,7. Supplementation of β-mannanase to β-mannan-rich diets may boost the population of beneficial intestinal bacteria, increase the digestibility of mannans, enhance the immunity, suppresses the growth of harmful intestinal bacteria, enhance the digestion and absorption of nutrients in intestinal tracts and reduce the environmental pollution due to poultry excreta8.
Thus, the objective of this experiment was to determine the effect of two different commercial β-mannanase products on growth performance, nutrient digestibility and energy utilization of broilers fed energy deficient diet.
MATERIALS AND METHODS
The present trial was carried out in the Poultry Research Unit belonging to Applied Feed Research House (AFRH), Orabi Community, Egypt, during October and November 2019.
Experimental design: A total 540 one-day-old broiler chicks (Ross 308) with initial body weight of 44±1 g were raised in well ventilated pens with soft wood shaving bedding material. The broiler chicks were weighed and randomly allocated to three treatment groups each of 180 chicks, in six replicates, 30 chicks each. The first group (T1) was fed the negative Control diet (Basal diet -80 kcal). Lycell® consists of 1,4 β-mannanase 250000 Unit g1 were obtained from Bacillus Lentus Fermentation with wheat bran carrier, whereas Hemicell® was a dried Bacillus lentus fermentation solubles with 158 000 unit g1 minimum β-mannanase enzyme activity.
Experimental diets: Birds were fed on starter (0-14 day), grower (15-24 day) and finisher (25-35 day) diets which were formulated according to the nutritional recommendation of Ross 308 strain catalogue (Table 1). The birds were vaccinated against common viral diseases i.e. Newcastle Disease virus (NDV), Infectious Bursal Disease (IBD), Infectious bronchitis (IB) and Avian Influenza (AI). Fresh water and feed were offered ad libitum during the whole experimental period.
Data recorded and measurements
Productive performance traits: Live body weight (LBW), body weight gain, feed consumption and feed conversion ratio were recorded at weekly intervals throughout the experimental period. Feed consumption was calculated by measuring the difference between the amount of feed offered and residue left. Feed conversion ratio (FCR) was calculated as total feed consumed divided by total weight gain for a given period of growth.
The feeding economic efficiency was carried out according to the prices of feed ingredients, tested material during the experimental period.
Performance index (PI) was calculated according to North9 using the following equation:
European Performance Efficiency Index (EPEI) was calculated using the following equation:
where, LBW is live body weight (kg), SU is survival rate (%) [100-Mortality rate], FCR is feed conversion ratio, and age is age of slaughter (days).
Carcass traits: At the end of the trial (35 day), four chickens from each treatment were randomly slaughtered for measurements of live body weight, dressing weight, dressing (%) abdominal fat, gizzard, heart and spleen weight.
Haematobiochemical parameters: Blood samples were collected from the slaughtered birds (4 chicks/treatment) in two tubes, one with anticoagulant (EDTA) and the other without anticoagulant for harvesting serum by centrifugation at 4000 rpm for 15 min. The resulting serum was kept frozen at -20°C until the biochemical analyses were done.
Haemogram estimation: Erythrocytic and leukocytic counts were performed using an improved Neubauer hemocytometer and Natt and Herrick solution as a special diluent for chicken’s blood according to Harrison and Harrison10. The packed cell volume was estimated by micro hematocrit centrifuge according to Coles11. Hemoglobin estimation was performed using the cyanomethemoglobin colorimetric method after centrifugation according to Zijlstra12. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) were then calculated. Blood films were made, fixed by methyl alcohol, stained by Giemsa stain for differential leukocytic count and detection of abnormalities in RBCs morphology according to Weiss and Waldrop13.
Serum biochemical analyses: Serum total proteins and albumin were calculated using the available commercial kits (DRI-CHEM NX500i, Japan) according to Weissman et al.14 and Doumas et al.15 respectively, while globulin was calculated by subtracting the value of albumin from the total protein whereas A/G ratio was calculated according to results of albumin and globulin. Serum Aspartate aminotransferase (AST) activity was determined using the method of Reitman and Frankel16, creatinine and urea were also determined using method of Bartels et al.17, serum total cholesterol and serum glucose was determined using the method of Allain et al.18.
Microbiological analysis: Aerobic, anaerobic, and coliform bacteria populations were counted from each sample (litter or dropping). To process the samples, 1 g of litter sample or dropping was diluted 10-fold using sterile buffered peptone water. The diluted sample was serially diluted using sterile buffered peptone water until a final dilution of 1:10 was obtained. From each serial, 12 dilutions, 0.1 mL was then spread plated onto two different media: tryptic soya agar and MacConkey agar. The dilutions were plated in quadruplicate on the tryptic soya agar and in duplicate on the MacConkey agar. Half of the tryptic soya agar plates and all of the MacConkey plates were incubated under aerobic conditions at 37°C for 24 h. To obtain anaerobic bacteria counts, the other tryptic soya plates were incubated anaerobically at 37°C for 24 h using Gaspack anaerobic jar19.
Isolation and detection of C. Perfringens, were done according to Shaltout et al.20. The collected samples were inoculated into tubes of freshly prepared, boiled and cooled cooked meat medium (Oxoid) and incubated anaerobically for 24 h at 37°C. A loopful of inoculated fluid medium was streaked on to neomycin sulphate sheep blood agar plate21 and incubated anaerobically at 37°C for 24 h using Gaspack anaerobic jar22. Suspected C. perfringens colonies were cultured onto 2 plates of sheep blood agar and egg yolk agar. One plate was incubated aerobically and the other plate was incubated anaerobically. The colonies that grew only in anaerobic condition and lecithinase producer and showed double zone of hemolysis on blood agar were picked up and purified for identification tests21,23. Isolated colonies with a typical appearance were then biochemically tested by using a commercial biochemical panel kit (API 20A, Bio Mérieux).
Histopathological examination: Tissue samples from duodenum, jejunum, liver and kidney were collected from the slaughtered chickens at the end of the experimental period. Samples were fixed in 10% neutral formalin buffer for latter processing by paraffin embedding technique. Tissue sections (4 micron thick) were then made by microtome (Leica 2135, Germany), deparaffinized and stained with hematoxylin and eosin23. The length of intestinal villi was measured from the tip of villus to its base. The mean length of 10 randomly selected villi/ intestinal cross section was measured in 3 cross sections for each chick24,25. Similarly, the width of villi and crypt depth were measured. The villus height/crypt depth and the absorption surface (AS) area were calculated using the formula reported by Oliveira et al.26, as follow:
AS (um2) = villus height (um)×width at half of the villus height (um)
Digestion trial: A digestibility trial was conducted at the end of experiment. Four birds from each treatment were housed in digestion cages, (47×47×47 cm3 dimensions) with nibble drinkers and separate feeders for 7 days. Feed and water were offered ad libitum during the preliminarily (4 days) followed by a collection period of 3 days. The feed consumption was recorded and excreta amounts were collected every 24 h.
The collected samples were dried at 60°C until constant weight then, excreta were weighed, ground, mixed well and stored for analysis according to AOAC27. The parameters recorded were; Feed intake (g bird1 day1), Excreta Weight (EW) (g bird1 day1), Excreta weight % (EWP), dry matter digestibility (DMD), organic matter digestibility (OMD); either as air dried or dried basis; and Excreta moisture content (%).
Statistical analyses: Data were analyzed with the help of the general linear model procedure using SAS28 and the corresponding means were compared using Duncan multiple test29. For all statistical analyses, differences were considered significant at p<0.05.
Table 2 shows non-significant differences in LBW of chicks during the first two weeks of age. At the 3rd week, chicks from treatment groups T2 and T3 had significantly heavier LBW than the control (T1) group. This trend was also observed at the 4th and 5th weeks of age, with chicks from T3 treatment having the best values. Moreover, BWG was significantly better for both T2 and T3 group than that of the control group. On the other hand, feed consumption ratio was significantly increased in response to feed additives (T2 and T3) compared to the control chicks at the 3rd week of age, whereas at the 4th week, chicks from all treatments consumed nearly similar amounts of feed. At the 5th week of age and for the whole experimental period, chicks from T2 and T3 treatments consumed significantly less amount of feed compared to the control chicks. This reduction in FC was 5.68 and 6.02% for chicks in T2 and T3, respectively. It is well-known that FCR is a function of BWG and FC, since our results revealed significant improvement in FCR of chicks from T2 and T3 for the whole period. This improvement was 11.11 and 12.78% for T2 and T3, respectively.
Supplementation of β-mannanase (Lycell® or Hemicell®) enzyme in the diets of broilers significantly (p<0.05) improved PI and EPEI. Minimum and significantly (p<0.05) lower EPEI (286) was observed in chicks fed negative control (T1) diet, however it was improved significantly (p<0.05) in T2 and T3 group (356, 371) respectively.
arcass traits:Table 3 shows that dressing weight and dressing percentage were significantly increased in chicks from T2 and T3 compared to the control group. However, abdominal fat was decreased significantly.