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2. Dietary additives for enhancing nutritional value of feeds

Enzyme supplementation to improve the productive value of high fibre diets:

Studies conducted on the effect of in vitro digestion on the chemical composition of broiler feed incorporated with enzymes suggest an increase in available carbohydrate (A-CHO) and acid soluble nitrogen fraction (ANSF) and reduction in acid detergent fibre (ADF) and neutral detergent fibre (NDF) of low fibre (LF) and high fibre diets supplemented with 1.0 and 1.5 g/kg enzyme feed supplement (EFS). One gram of EFS contained amylase, 7,500 units; cellulase, 400 units; protease, 200 units and lipase, 300 units. LF and HF diets contained un-autoclaved and autoclaved rice bran (RB), wheat bran (WB) and sunflower cake (SC). The observations have also been supported by in vivo studies. These studies involved two types of diets namely LF (fibre, 3.2%) and HF (fibre, 6.4%) containing 22.18% crude protein; 2900 kcal ME and 22.68% crude protein; 2600 kcal/kg ME, respectively. Third diet (HF1) had 1.5-g/kg enzyme feed supplement. LF diet contained autoclaved rice bran (RB) as higher fibre feed ingredient whereas HF diet contained autoclaved RB, wheat bran and sunflower cake as high fibre feed ingredients. Body weight gain, feed efficiency and performance index were significantly higher in chicks fed diet with EFs. Cost of production of 1 kg live weight of broiler fed LF diet was Rs.13.68, whereas for producing the same live weight gain of broiler fed HF diet with EFS, the cost involved was Rs.13.56. Therefore, in the production of 1 kg live weight in broiler fed HF diet with EFs, there was saving of 12 paisa approximately. It was also suggested that for large-scale broiler production, use of autoclaved high fibre ingredients along with EFs was economical. The cost benefit analysis at 6 weeks of age is given below:

ATTRIBUTES

LF

HF

HF1

Mean live weight (g)

1552

1377

1483

Body weight gain (g)

1504a

1322b

1438a

Feed intake (g)

3623

3736

3568

Feed efficiency

2.41b

2.80a

2.48b

Feed efficiency ratio

0.415a

0.356b

0.403a

Performance index

624a

475b

579b

Cost/quintal diet (Rs.)

570

517

547

Feed cost/kg live weight (Rs.)

13.68

14.73

13.56

Effect of non-starch polysaccharide hydrolyzing enzymes (cellulase, xylanase, pectinase and α-galactosidase etc.) on performance of broiler fed maize-soya diets.

Experiments on utilization of non-starch polysaccharides (NSP) indicated that the performance of broilers in terms of weight gain, efficiency of feed utilization, livability and carcass attributes is not affected by supplementation of different NSP degrading enzymes. The supplemental levels of enzymes incorporated individually or in combination were as follows.

Enzyme(s)

Level(s)

Cellulase

420 IU/kg

Xylanase + pectinase

4025 IU and 5 IU/kg, respectively

Xylanase + pectinase

40253 IU and 53 IU/kg, respectively

Xylanase + pectinase + α-galactosidase

40253 IU, 53 IU and 20 IU/kg, respectively

Xylanase + pectinase + α-galactosidase + cellulase

40253 IU, 53 IU, 20 IU and 560 IU/kg, respectively

The insignificant effect of enzyme supplementation on performance indicates that the enzymes at the concentration used did not elicit any beneficial response on the utilization of NSP in broilers. The calculated total NSP content in starter and finisher diets is 9.79 and 9.58%, respectively, out of which the major component is glucose, which might be a monomer of cellulose. The observed significant increase in weight gain in xylanase and pectinase fed birds at 28 d of age and subsequent disappearance of this effect in these experiments indicate that the chicken at the younger age are not able to utilize xylans and pectins and thus required additional supplementation of enzymes to hydrolyze these compounds. This observation also indicates that as the age of the bird advances the anti-nutritive effect of these NSP declines.

Composition (%DM) of the NSP in maize and soyabean meal

NSP component

Maize

Soyabean meal

Arabinose

1.9

2.0

Xylose

2.4

1.8

Mannose

0.2

0.6

Galactose

0.4

2.9

Glucose

2.6

6.7

Uronic acid

0.6

2.5

Total NSP

8.1

17.2

The growth depression observed in broilers fed xylanase + pectinase + α-galactosidase might be due to incomplete hydrolysis of the NSP and consequent increased viscosity of intestinal digesta. The α-galactosidase concentration employed was very low. The increased viscosity of intestinal digesta is known to inhibit the digestion and subsequent absorption of nutrients from the feed. The growth depressing effect of above enzymes on broilers was alleviated by the addition of cellulase to the above enzyme complex. Since, cellulose is the major component of the NSP in the experimental diets, cellulase supplementation might have increased the hydrolysis of -1-4 linkage of glucose monomers utilization in broilers fed a combination of xylanase + pectinase + α-galactosidase + cellulase. It is also possible that on breakdown of cellulose, the major component of the cell wall the release of encapsulated intracellular nutrients might have been released.

NSP (%) present in the diet.

NSP component

Starter diet

Finisher diet

Arabinose

1.68

1.69

Xylose

1.91

1.93

Mannose

0.29

0.28

Galactose

1.10

1.03

Glucose

3.49

3.40

Uronic acid

1.09

1.05

Total NSP

9.79

9.58

Several workers also did not observe any significant effect on broiler performance due to supplementation to corn soya diet of either individual or multi-enzymes hydrolyzing NSPs. Contrary to this, a significant improvement in broiler performance has been reported in broilers when fed either corn soya diet or soyabean meal supplemented with either individual or combination of NSP hydrolyzing enzymes. The reported beneficial effects of NSP enzymes on broiler performance may be due to increase in digestibility and retention of nitrogen, increase in dry matter and energy utilization. The reported wide variation in the performance of broilers due to NSP enzymes supplementation to corn soya diet might be due to variations in the concentration and composition of NSP in the diet and source and/or activity of the enzymes supplemented. The activity of a specific enzyme produced even from the same microorganism vary significantly. Further, the variation could also be due to the variation in dose and composition of enzyme cocktail. The improvement in broiler performance observed by some workers due to supplementation of enzyme could be due to incorporation of higher dose of cellulase (1000 to 3000 IU/kg diet) compared to the levels used in some of other studies (420 and 560 IU/kg diet) and also be earlier workers (15 to 97 IU/kg diet). The lack of response due to supplementation of only xylanase in corn-soya is expected because, the monomers released from by the action of the enzyme on arabinoxylan i.e. arabinose and xylose are poorly metabolized by poultry and therefore of little value to animal performance. The addition of a mixture of enzymes considering the composition of NSP in a given diet may yield better response compared to supplementation of individual exogenous enzyme. A series of experiments have also been conducted in CARI Experimental Station employing various maize-soya, pearl millet, sorghum, finger millet, mustard cake and un-decorticated sunflower seed meal based diets in broiler chickens, native chickens and Japanese quails. The commercial preparation was analyzed and found to contain sufficient enzyme activities. The enzyme preparation was incorporated in diet at level of 50-g/100 kg. The activities of various enzymes in a gram of commercial enzyme preparation were: glucanase, 35732; -D xylanopyrosidase, 98466; xylanase, 2202; FT Pase, 397; amylase, 5773 and CM cellulase, 1906 MIU/kg. There was marginal improvement in growth of broiler chicks in pearl millet based diets during starting phase while significant improvement was observed in finger millet based broiler starting and finishing diets. Enzyme supplemented was also found beneficial to improve utilization of sunflower seed meal supplemented in maize-finger millet or maize-sorghum based broiler starting and finishing diets. However, on repeated trials on maize-soya-deoiled rice bran diets for three times in broiler chickens, twice in Japanese quails and twice in native chickens, enzyme supplementation did not prove beneficial in terms of growth or feed conversion efficiency.

Some of the reports on enzyme supplementation and its effect have been summarized hereunder:

Enzyme(s)

Level

Type of birds

Type of feed

Effect on performance

1. Anizyme, allzyme BG, ventrigold

-

Broiler

Low/normal energy

Superior weight gain and FCR than control.

2. Multi-enzymes preparation

500 g/tone

Broiler

Raw/ autoclaved millets

Better FCR and P balance.

3. Multi-enzymes preparation (-D-Glycosidase, cellulase, protease, anaylase and phytase)

500 g/tone

Broiler

Commercial poultry feed

Significant improve-ment in body weight.

4. Fibrolytic enzyme - Nutrizyme (xylanase, pectinase and cellusase)

0.1%

Layers

Energy levels - 2000 to 2700 kcal/ME/kg

Significant improve-ment in egg product feed efficiency and decreased viscosity except in high-energy group (2700 kcal/ME/kg.

5. Multi-enzyme preparation

-

Broiler

Broiler diet having dried poultry excreta (0-10%)

Improvement in the performance.

6. Multi-enzyme preparation

-

Broiler

Apple pomace replacing maize (15-20%)

Improvement in feed conversion efficiency.

In vitro evaluation of non-starch polysaccharide digestibility of feed ingredients by enzymes:

Some of the commonly used feed ingredients for poultry (corn, sorghum, finger millet, deoiled rice bran, soya bean meal, peanut meal, sunflower meal and rapeseed meal) were screened for pentosans, cellulose, pectin and total non-starch polysaccharides. The ingredient in vitro digestibilities by enzymes were evaluated. Cereal samples screened contained mainly pentosans. Pectin content was rich in oilseed meals. Sunflower meal, soybean meal, deoiled rice bran and a broiler starter diet were subjected to a 2 stage in vitro digestion assay with 3 different enzyme mixtures viz. Enzyme-I (xylanase + cellulase from Trichoderma viridae), Enzyme-II (xylanase + Cellulase + beta-glucanase from Huminicola insolens) and Enzyme-III (xylanase + cellulase + pectinase + beta-glucanase from Aspergillus aculeatus) by incubating 0.1 g of the sample with 3 ml of a pepsin-HCl mixture (2000 U pepsin/ml of 0.1 N HCl) for 45 min to simulate the peptic phase of bird digestion. A panereatin-NaHCO3 mixture (2 mg panereatin/ml of 1 M NaHCO3) was used for 2 h at 40C to simulate the panereatic phase. Digestibility was assessed by measuring the relative viscosity of the digesta supernatant and the total sugars released. Enzyme-I produced the least relative viscosity and highest total sugars in sunflower meal, deoiled rice bran and broiler starter diet, and whereas, Enzyme-III was very effective in soyabean meal subjected to in vitro digestion.

Use of probiotics for improving the performance of birds:

Probiotics have been primarily used to establish normal intestinal flora to prevent or minimize the disturbances caused by enteric pathogens and secondarily to serve the function of antibiotic feed additives in diet of animal. The probiotics currently on the market/under investigations contain Lactobacilli : (L.lactis, L. bulgaricus, L.bifidus, L.brevis, L.cellobiosus, L.fermentum, L.sporogenes, L.acidophillus, L.plantrum, L.cremoris, L.cellinoides, L.salivarius, L.reuteri); Streptococcus (S.faecium, S.lactis, S.thermophilus); Pdiococcus (P.halophilus, P.pentosaccus), Bfidobacterium spp. and Saccharomyces (S.cerevisine, S.boulardii.), Bacillus (B.cereus, B.subtilis), etc. These have been used both alone and in combination. However, they are active against a wider range of condition when multiple - strain preparations are used. Lactic acid bacteria or yeast are able to inhibit the growth of bacteria like Salmonella, Clostridia and E.coli. Probiotics especially lactobacilli and Bacillus cereus are also important in the development of immunocompetence against enteric infections. However, the probiotics are not substitute of antibiotics in birds with serious infections but are useful in restoring the normal bacterial population that was otherwise altered due to administration of antibiotics. The lactic acid bacteria also consume potentially dangerous waste products and suppress the aflatoxin effect. The response in relation to performance and microbial balance has not always been consistent. Such variations on the response of birds to probiotics feeding have been attributed to several factors such as microbial strain used, number of viable cells per units of feed, mode of administration, processing method for feed employed, type and nature of diet, age of the birds and the sanitary condition of poultry house. The improvement in the performance of birds has usually been realized for young chicks and more so under the unhygienic housing conditions. Some of the important observations recorded in studies conducted on the use of probiotics are recorded below:

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