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Digital Re-print - July | August 2010 Feature title: Technical design and equipment - Key to improving feed quality and nutrition

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Why do some feed factories earn profits while others don’t? Why do feed

of some factories sell well? The reason behind is technical design and equipment selection.

Choosing skilled feed engineering con-structors and comprehensive solutions pro-viders are also vital for the success of a company.

The factors affecting feed quality can be summed up in three aspects, namely:

• The quality of raw material • The feed formula • The process technologyWith the same level of raw material and

formula, the quality of feed only depends on

process technology and equipment perform-ance.

As the digest system of chicken, pig, fish, shrimp and pet varies, feed of different size and degree of ripeness are demanded. It is one of the important methods for the modern feed companies to improve product quality by upgrading process technology.

Impact of grain size on feed nutrition

Generally, grain size should take consid-eration of many factors like feeding method, process costs, capacity and growing charac-teristics of animals.

Its empirical value should be no more than 1/3 of the diameter of pellet.

Appropriate grain size can improve diges-tion rate of the nutritious ele-ment. Research has shown that if the even size of corn feed for sow is reduced from 1200um to 400um, its digestion rate could be raised by 14 percent, dry materi-als in manure could be reduced by 21 percent and the nitrogen would be lowered by 31 percent.

Over grind could lead to more consumption of energy, less capacity and destroy of nutrition of feed. The research data proves that VA of pellet after repeated grind would decrease 40 percent.

The key point of grain size control technology is to grind each raw material to the best size suitable for digestion so as

to ensure the batch feed can acquire best raising efficiency and economic profit. It is mandatory to study the best digestion size of each raw material for different animals as shown in Table 1.

Pulverization and micro-pulverization must be applied for aquatics feed.

Research has shown that carp feed ratio could raise 5-10 percent if the screen of grinder has been reduced from 1.5mm, 1.2mm to 1.0mm, 0.8mm, 0.6mm. As a result, grain size has a markable influence on variation of nutrition.

Grain with excessive small or big diam-eter could break into layers which would affect the digestion rate of feed nutrition. It is only by selecting proper technical design, professional company and equipment can good quality feed be made.

Impact of batch on feed nutritionFormula is a major impact factor for feed

nutrition and pellet quality. Formula with high content of grain like corn and soybean cannot produce high quality pellet feed due to the lack of natural bond.

Addition of highly cohesive wheat can improve pellet quality.

It is necessary to combine each ele-ment in the formula and keep fat to lowest limit. In case of large proportion of adding materials, the condition process should be adjusted or the materials should be added after pelleting.

As the core process of feed production, batching accuracy has a direct impact on feed composition and nutrition absorption of the

Table 1: International best grinding particle size

Animal Raise stage Best size recommended (μm)

Pork

Ablactation 0~14d 300

Ablactation 14~35d 400

Grice ≤500（Corn（

Fattening pig 500~600（Corn（

Sow 500~600（Corn（

Growing pig 15~30kg 323(batch)

Dorking 700~900（Corn（

900

Beef cattle 1~1.5cm（straw（corn stalk（

2~7cm（corn stock（hay（

Fish ≤0.5mm（batch（

Shrimp 150~175

Technical design and equipment

by Shao Jianxin, Engineer, ZCME, China

Grain&feed millinG technoloGy10 | July - august 2010

FeatureQuality and nutrition

animals. As a result, the feed nutrition can be balanced only with appropriate batching system.

The batching process has a important effect on batching accuracy and composition. The major technical improvements lie in fol-lowing aspects:

1: The batching scale must be checked regularly so as to ensure measure-ment accuracy of batching equipment

2: The formula should be right and the raw materials can be replaced

3: The materials should be fed at proper speed

4: The control system should be correct5: The batching equipment must

be operated in correct way6: The batching equipment

should be clean so as to avoid cross contamination

7: The batching process espe-cially the use of medicine should be carefully recorded

No-error computer control technology is adopted to manipulate batching accuracy.

Micro additives can be premixed and

batched and high accurate batching system can be adopted.

Impact of mixing conformity on nutrition

Conformity is vital for feed quality as it will determine whether the animal can get full nutrition from the feed. The air balance between mixing bin and mixer also has an impact on nutrition.

Too big finish product bins and pellet bins and too long transportation lines will destroy conformity of feed and reduce the conver-sion rate of the animal.

It is critical to choose the right mixer, mixing period and feeding method in order to ensure conformity and nutrition. The control of mixing conformity covers mixing feed, concentrated feed, additives, premix feed and liquid feed.

The technical improvements in batching process have the following aspects:

1: Proper mixer must be select-ed to ensure conformity

2: The materials should be added in

correct order with big materials added at first and small ones added later. All materials should be added in proper amount and order espe-cially for production of premix feed

3: In case of change of formula, the mixer should be thoroughly cleaned to avoid cross contamination

4: Premix should be separated from major mixing process in order to prevent cross contamination

5: The transportation distance and height of materials after batching should be as short as possible and no conveying equipment like pneu-matic device should be adopted as it would cause separation of materials

Impact of pelleting on feed nutrition1. Pellet quality control: pellet qual-ity is the precondition of feed nutrition which must be strictly manipulated. The conditioning quality is the primary control point of pellet quality which includes tem-

Grain&feed millinG technoloGy July - august 2010 | 11

Feature Quality and nutrition

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steam with proper characteristics is a pre-condition of pellet quality.

Technical improvements of steam pres-sure and flow rate covers following aspects to ensure high quality of feed: 1: Control the conditioning of meals,

including the adding of steam and oil, and check the quality of steam and keep a good record of it

2: Control the product from the pel-let mill and keep record of it

3: Control the cooling time, mois-ture and temperature of feed in accordance with the room temperature and moisture

4: Control the fat coated on the surface of feed

5: Check the hardness of pelleted feed and keep good records

Conditioning process is vital for pellet quality. The mixed materials with high content of grain usually stay for at least 40-60 seconds in the conditioner.

Meanwhile, the temperature inside the conditioner should be kept between 85-98℃ to improve ‘pasting’ of starch. Materials with high fibers must stay for shorter time in the conditioner. In case of addition of liquids like molasses, the materials should stay longer in conditioner (maximum 30 minutes) so that it would absorb molasses fully.

High temperature conditioner with short time (60-160 seconds) can kill bacteria.

Many conditioners of this type have been developed in several countries. The durability of feed at high temperature should also be considered during condition-ing.

Materials with bad durability under high temperature and poor ‘strength’ should avoid conditioning at high temperature. Instead, they should be coated later so as to ensure pellet quality. 2. The impact on vitamins: it is vulnerable to increase conditioning time and raise temperature as the vitamins with poor thermal stabil-ity would be easily lost during the pelleting process. Vitamins like A, E, C, thiamine hydrochloride, etc will be killed rapidly as the temperature and conditioning time is raised.

The critical condition for con-ditioning of feed with vitamins is

as following: temperature ≥90°C, mois-ture≥15%, time ≥60 seconds.

steam supply and control systems, condition-ing, pellet-ing, cooling and screen-ing equip-ment with all control parameters scientifically adjusted.

The steam fed into con-ditioning units must be unsatu-rated steam, free from condensed water so as to ensure enough ‘pasting’ of starch and prevent machine blockage

due to too much moisture. The steam must go through a water trap and a pres-sure reducing valve before entering the conditioner.

Meanwhile, the flow rate of steam must be matched to the feeding rate. As a result,

perature, time, water and ‘pasting degree’ of starch. A secondary control point covers powder rate, cooling temperature, moisture, blade-even degree and water

durability of the feed. To meet the above requirements manufacturers need proper

Table 2: Anti-nutritional factors of common raw materials of feed

Anti-nutritional factors Distribution Inhibit function

Protease inhibitor

Pea seed, beet broomcorn Restrain activity of trypsin and pepsin, facilitate secrete of pancreas

GlucosideRapeseed, cabbage,Kale, etc Prohibit growth, increase cardiolipin and reduce appetite

Lectin Pea seed Impair intestinal wall, lose more endogenous protein, inhibit growth

Tannin Pea seed and cake, etc Weaken absorption of protein, carbohydrates

Gossypol Cottonseed and cakeinjures gastric mucous membrane, destroy metabolization of protein and iron

Phytic acid Pea seedInterfere biological effectiveness of mineral elements, form protein complex

Saponine Soybean Destroy absorption of nutrition, reduce appetite

Lignin Pasture Destroy absorption of nutrition, reduce appetite

Alkaloid Pasture Reduce appetite, inhibit growth

NSP Grain feed Facilitate pasting of materials inside enteron, weaken absorption of nutrition

Grain&feed millinG technoloGy12 | July - august 2010

FeatureQuality and nutrition

ish pellet feed can obtain satisfactory quality and nutrition.

Impact of technical processThe anti-nutrition factors in feed can

cause disease of pigs and pets and retard the growth process. As they are closely related with process technology, nutri-tionists have developed many methods to eliminate anti-nutrition factors.

However, the nutrition elements in feed would lose at the same time. Extrusion and expansion at high tempera-ture can improve feed quality and limit lost of nutrition; anoxia sterilisation could kill bacteria effectively and keep vitamins; fermentation could eliminate toxic effect of anti-nutrition factory and keep vita-mins; enzymes preparation cannot only erase toxic effect of feed but also provide a health function.

Getting rid of anti-nutrition factors in raw materials has become vital in selection of process technology and equipment. Feed quality and nutrition can be only be guaranteed using pro-fessional technology and equipment. With the development of nutrition, technicians of professional company can work out better methods to elimi-nate anti-nutrition factors and make more contribution in improving feed quality and nutrition.

More inforMation:ZCME Floor 25th, Friendship Building No.159Zhao Jia Bang Rd ShanghaiPC:200032 PR China

Tel:+86 21 64188282Fax:+86 21 64163299

5. Impact of pellet on starch and protein: the starch would become ‘pasted’ and pro-tein would be denaturated after conditioning so that the animal can digest and aborb the starch and protein better.

However, it is the technical issue of a professional company to determine the raw material of specific size for spe-cific animals. Protein denaturation has little influence on amino acid but improves its absorption rate greatly so that protein can be highly utilised.

6. The impact of post-cooking: after condi-tioning, the ‘paste’ degree and water durabil-ity of pellet should be improved, however, some thermal alert vitamins are destroyed. As a result, it is better to use formulations with sound thermal stability or apply the improved coating technology so as to pre-serve nutrition values of the feed as much as possible; which is mostly used in the produc-tion of aquatics feed or special aquatics feed for shrimp for example.7. Impact of storage and transportation: cross contamination usually takes place during storage and transportation. Residue in transportation vehicles, bins, buffer hop-pers and process equipment could cause cross contamination. Harmful microbe and pests are also source of cross contamina-tion.

To meet increasingly high demand of security, sanitation and nutrition of feed, it is necessary to equip residue-free con-veyor and bins, apply scientific technology of cleaning and sequencing. Heat treat-ment technology should be applied which includes cooking at high temperature, extru-sion, high-pressure treatment and ultraviolet irradiation, etc. With the comprehensive application of the above technology, the fin-

As a result, it is necessary to choose formulation with sound thermal stability. A good pellet conditioner, correct air admis-sion and mixing methods are also the vital factors for pelleting process.

3. Feed enzymes: pellet process also affects feed enzyme and other microbials.

Enzyme and microbial are biological products, the activity of which are usually damaged under the comprehensive func-tion of high temperature, humidity and pressure. It is reported that the activity of phytase drops by 87.5 percent at tempera-tures of over 80℃.

So the utilisation rate of N.P. will be affected. The microbe additives in the feed is especially reactive to high temperature so that its activity will be lost completely if the pellet temperature exceeds 85℃. It is better to coat enzyme after pelleting or to use enzymes with better thermal stability.

4. Impact on anti-nutrition factors: part of anti-nutrition factors and harmful sub-stances will be killed during the condition-ing of pellet. Anoxia sterilisation before pelleting can kill various bacteria effectively and improve feed quality. It has been a key research subject for professional techni-cians.

Animals have different reactions to the same anti-nutrition factors as its species and age vary. The anti-nutrition factors can be divided into positive inhibitors for carbohydrate, minerals and prolease, etc. The pelleting process adopts conditioning, high temperature extrusion methods to weaken the anti-nutrition factors as listed in Table 2 to maximum limit.

Grain&feed millinG technoloGy July - august 2010 | 13

Feature Quality and nutrition

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August 2010

• Mycotoxintesting:

ready for this year’s harvest?

In this issue:

• Technical design and equipment - Key to improving

feed quality and nutrition

• Factors affecting pelleting

and energy consumption

• Fusarium mycotoxins

– What’s all the fuss about?

• MakingFeedPellets

• AddedvaluebyFlourHeatTreatment

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