Role of Feed Grinding and Feed Particle Size (Feed Granulometry) in Poultry Feed Nutrition

Role of Feed Grinding and Feed Particle Size (Feed Granulometry) in Poultry Feed Nutrition

Grinding, mixing and  pelletization are  the  key processes in poultry  feed  production. These  processes have direct  effect on  feed  quality,  feed  intake  (FI) and  poultry  performance. Grinding  is most typically associated with the size reduction of  cereal  grains.  It is extensively studied  that  particle  size and grinding  of raw  materials  have major  impact  on mixing and pellet  quality.  Particle  size also plays important role  on the  development of gastrointestinal tract  (GIT) and growth performance  of  broilers.  Generally, reduction  in  particle size leads  to higher  ingredient surface  area  to interact with digestive acids and enzymes which ultimately  improves digestibility.  The   practice    of   feeding  whole    grains   to broilers  along with balanced concentrate is increasing acceptance  in  certain   regions,  including   Europe, Canada, Australia and New  Zealand. The main driver  of this practice is  the  potential of  reducing feed  cost  by  eliminating the grinding  step.  It has also positive  effects  on  poultry  health and welfare.

 Supply of good quality feed to birds is the utmost requirement in poultry industry. It ensures maintenance of overall health of the birds and also reflects over its production performance. Unlike the quality of the feed, the feed particle size is often ignored in poultry production. During feed milling process, the feed particle size varies from very fine to extremely coarse and doesn’t remain as a uniform mixture. A poultry feed consists of different feed ingredients varying in shape and size. These ingredients are subjected to a number of processing steps which include grinding, mixing, pelleting and other methods to produce the final formulated feed. The digestive system of the poultry responds differently to diverse feed sizes and affects largely the performance of the flock. It is, therefore, necessary to appraise the feed particle sizes throughout the process of feed formulation.

Effect of particle size  and feed form on growth performance

Importance  of   particle   size   in   poultry    diets   has   been recognized because of  its benefits associated with  gizzard development and improvement in growth performance (Abdollahi et  al.,  2018). Various  studies  over  the  last few decades  demonstrated  that   the   particle   size  has  positive impact on the FI of broilers  fed mash diets. The FI in broilers fed  mash  diets  can be  increased by increasing particle  size and the effect  varied with the age of birds and type of grain (Table 1).  Attawong et  al.  (2014)  recommends that  corn particle  size  of around 805  microns  is enough for younger birds (<28 days).  However, with advancement of age larger corn  particle  size  is likely required. The  FI of crumbled or pelleted diets  was  not  affected by particle  size  of maize  or wheat (Table 2).  Weight gain  (WG) and  feed  efficiency (FE) improved with  increase  in particle  size of grains  either in  mash   or  pelleted  diets,   but   results   are   contradictory (Tables  1  and  2).  Auttawong et  al.  (2013)  tested two dietary   levels   of   coarse   corn   (0   or   35%)  on   broiler performance and  reported improvement in FE with  coarse corn (1080 microns) with ad libitum feeding  over restricted feeding.  Similarly,  Xu  et   al.  (2015)  reported improved zootechnical parameters and  digestive functions  of  broiler birds  when   crumble-pelleted diets  contained 50%  coarse corn.  The  authors reported  improvement in  body  weight (130 g) and feed conversion ratio (12 points) in 42 days old broilers.  This  correlates  well  with   the   increased  gizzard weight  (2.75  mg/g   body    weight),   increased  digesta retention time (0.78 h) and increased apparent ileal digestibility  of  energy (8.2%)  and  nitrogen (12.4%)  in broilers  fed diets  with  50% coarse  corn  compared to those fed without coarse  corn.

Effect  of  particle   size  reduction  of  commonly   used   by- products in poultry  feed  such  as distillers  dried  grains  with solubles  (DDGS)  and  soybean meal  (SBM)  has  also  been investigated. Pacheco  et  al. (2014) evaluated the  effect  of particle   size  of  SBM  (410 or  1025  microns) and  DDGS (480 or 745  microns) on live performance. The inclusion  of fine  SBM  (410  microns) improved pellet  quality  whereas coarse   SBM  (1025  microns) had  positive   effect   on  live performance. Fine  DDGS  (480  microns) increased FI and body   weight  without  any  impact   on  the   FE.  However, coarse   DDGS   (745   microns) in   broiler    diet   increased gizzard  weight. Therefore, coarse  particle  size of DDGS and SBM in broiler  diets results  in better growth performance. Physical  form   of  feed   has  significant   impact   on  growth performance of broilers  (Dozier et al., 2010). Many studies have  reported  improvement in  broiler   performance when fed  pelleted feed  compared to  mash  feed  (Amerah et  al., 2008; Chewning et  al., 2012; Mingbin  et  al., 2015). Use of crumble  or pellet  form  of feed  reduces the  feed  wastage and   prevents  particle    selection.   Pelleting   process    also improves  palatability  and increases nutrient digestibility (Mingbin et  al.,  2015). Zang  et  al.  (2009) also  reported improvement in  FI,  WG  and  FE when   broilers   were   fed pelleted diet.  Mingbin  et  al. (2015)  conducted a study  to evaluate the effects  of feed  form (mash and crumble-pellet) and   feed   particle    size   (fine,    medium    and   coarse)  on performance  and   GIT  development  of   broilers.  Results showed  that   feed   form   had   greater  effect   on   broiler performance and  GIT development than  feed  particle  size. Figure 1 shows  effect  of feed  form and feed  particle  size on growth performance of broilers.

Table 1: Effect of particle  size on feed intake,  weight gain and feed conversion ratio (FCR) of broilers  fed mash diets

Table 2: Effect of particle  size on feed intake,  weight gain and feed conversion ratio (FCR) of broilers  fed crumbled or pelleted diets

Figure  1:  Effect  of  feed   form  (mash   and  crumble- pellet) and feed particle  size (fine, medium  and coarse) on  average feed  intake,   average daily  gain  and  feed conversion ratio of broilers  (1-40 days).  Fine, medium and coarse  particle  sizes were achieved  by grinding the macro  ingredients (wheat, corn  and  soybean meal) in the hammer mill to pass through 2, 5 and 8 mm sieves, respectively. (Mingbin et al., 2015)

Effect of particle size  on gut development and health

Feed particle size has significant impact on the early development and growth of the gut microflora. Certain experimental studies have revealed that the consumption of large, coarse feed particles influence the gut development due to improvement of gut motility and the increased intestinal length. The activity of the gizzard increases with an increase in the feed particle size thereby the muscular gizzard shows better results in terms of size and function; else, it remains vacant mostly when the birds are fed with very fine feed and hence gizzard reduces in size. A well-developed gizzard acts as a protective barrier against entry of harmful pathogens into the gastrointestinal tract thereby it becomes important for proper development of the gizzard. Birds fed with coarse larger or pelleted feed tend to have a reduced pH in the gizzard which restrains the growth of harmful pathogens. A functional gizzard also stimulates the secretion of HCl and other gastric secretions involved in the digestion process and thus help in better protein utilization. It has been found that when birds are fed with fine feed particles, the particles pass through the tract rapidly without spending much time inside the gut. This reduces the absorption capacity and the nutrients remain un-utilized. Whereas feed particles with comparatively larger sizes tend to remain in the intestinal tract for more time and aid in proper digestion and absorption of the nutrients. The theory behind this is that the increase in transit time of feed through the intestinal tract favours growth of the microvilli present in the gastrointestinal tract which resulting in improvement of the absorption process. Large and coarse feed particles attract the birds more than fine particles and thus influence the feeding behavior. Proper feeding behavior supports growth of the beneficial gut microorganisms. Feeding of fine feed particles may lead to increase in viscosity inside the gastrointestinal tract which limits the nutrient absorption and may cause wet litter condition. Furthermore, it creates an environment which flares up the opportunist pathogens leading to a disease condition. One of the most common condition is the necrotic enteritis caused by overgrowth of Clostridium perfringens type A producing toxins which further damages the intestinal epithelium.

Feed   particle   size  influences  the   GIT  development  to  a greater  extent  when    the   broilers    are   fed   mash   diets compared to pelleted diets.  Reducing  particle  size property of pelleting process  may results  in suboptimal gizzard development   and    changes   in    the    morphology   and microbiota profile of intestinal  tract (Zaefarian et al., 2016). Large particle  size supports gizzard  functions  and gut health development in broilers  (Svihus et al., 2004; Choct,  2009). Naderinejad et al. (2016) also found  that coarse  grinding  of maize in pelleted diets had positive  effect  on gizzard development  and   functionality   which   is   beneficial    for nutrient utilization   and  growth  performance. The  gizzard has  good  ability  to  grind  the  feed  to  a consistent particle size (Hetland et al., 2004). A well-developed gizzard improves  grinding activity and gut  motility  (Ferket, 2000). It  increases  cholecystokinin release  which   stimulates the secretion   of   pancreatic   enzymes   and    gastro-duodenal reflexes  (Duke, 1982; Svihus et al., 2004). Coarse  particles reduce the  digesta   rate  in  gizzard   and  lower   the  pH  of gizzard  (Nir et al., 1994). Low pH of gizzard  may increase pepsin  activity (Gabriel  et al., 2003) and protein efficiency. It also reduces the risk of coccidiosis (Cumming, 1994) and feed-borne pathogens (Engberg et al., 2002).

Particle  size  also affects  the  intestinal  tract  segments other than the gizzard, but results  are contradictory. Amerah  et al. (2007)  reported  non-significant change   in  villus  height, crypt  depth, and epithelial  thickness in the  duodenum with increase  in maize  particle  size.  However, Liu et  al. (2006) and  Xu  et  al.  (2015)  reported positive   effect   of  coarse maize  on  intestinal   morphology.  The  inclusion   of  coarse maize  reduced the  number of mast  cells in the  duodenum, jejunum, and ileum compared with finely ground maize (Liu et al., 2006). Reduction in mast cell in the small intestine is beneficial.  Increase   in  mast  cell  numbers reflects   Eimeria infection  in broilers  (Morris et  al.,  2004). Particle  size  of ingredients  also  affects   the   intestinal   microbiota  profile. Jacobs  et  al.  (2010)  reported change   in  cecal  microbiota profile  with  use  of  different corn  particle  sizes  (Table 3). The  Lactobacilli population was  significantly  increased (P < 0.05) when  the  largest  corn  particle  size of 1,387 μm was included  in the diet.  Increase  in Lactobacilli concentration is considered to  be  beneficial  because it can  prevent colonization of  pathogens such  as  E. coli (Engberg et  al., 2002). The Bifidobacteria population was significantly decreased with increasing corn particle  size from 557  μm to 1,387 μm. However, E. coli population was not affected by corn  particle  size.  Singh  et  al. (2014) also  found  that  the counts  of Lactobacillus and  Bifidobacteria species  increased and  those   of Clostridium,  Campylobacter   and  Bacteroides species  were decreased with  increasing inclusion  levels  of coarse  maize  (0  to 600  g/kg). Coarse  mash  diets  can also increase  the  Lactobacilli population in the  ceca  and  rectum (Engberg  et  al.,  2002).  It  can  be  concluded  that   large particle  size  not  only  influence   the  GIT development but also change  the  cecal  microbial  populations. Large  particle size  increases the  Lactobacilli counts  and  reduces the pathogenic bacteria  in the  caecum  of broilers. Gracia  et  al. (2016)  tested the   effect   of  whole   wheat  and  oat  hulls addition  in pellet  and  mash  diets  on  GIT development and Campylobacter  jejuni  in cecum.  Whole  wheat and  oat  hulls in  mash   diets   significantly   reduced  cecal   Campylobacter jejuni  colonization at  42  days  whereas no  clear  reduction was observed for pellet  diets.

Table 3: Effect of corn  particle  size on cecal microbial  populations in 21-d-old chicks in experiment 1 as determined by quantitative PCR1 (Adapted from Jacobs et al., 2010)

Effect of whole grain feeding on growth performance and gut health

The  primary  aims of feeding whole  grains  in broilers  is to reduce feed  cost and to improve  digestive functions (Singh et  al.,  2014). It  has  also  good   impact  on  gut  health   by encouraging  the   colonization  of  beneficial   bacterial   and reduces the incidence of coccidiosis (Cumming, 1989). Engberg et  al. (2004) reported that  whole  wheat feeding can  reduce  intestinal   numbers  of  Clostridium  perfringens which   is  important  for  prevention  of  necrotic   enteritis. Whole  grain  feeding  practice  meets  consumer demands for a  natural   feeding   system   and   good   for   animal   welfare (Gabriel   et  al.,  2008).  Whole wheat feeding under   free choice  feeding system  increased weights and  length  of the segments of small intestine (Singh  et al., 2015). Fernandes et  al.  (2013)  also  reported  increased in  small  intestine weight with  50  or  100% of  whole  sorghum grain  in the broiler  diet.  Cecum  length  was  also  significantly  increased when birds were fed diets  contained whole  sorghum grain. Intestine is the  biggest immune  organ  inside  the  bird  body which contributes further to better health  and immune response. It  has  been   reported that  whole   grain  feeding approach  helps  in  preventing  the  enlargement  of proventriculus and  atrophy of  gizzard  which  are  common problems with  pelleted diets  (Singh  et  al.,  2014). Whole wheat  given   under    free   choice   feeding  increased  the relative  gizzard  weight, irrespective of mash  or pellet  form of feed  (Singh  et al., 2014). Whole  grain feeding may also influence  starch   digestive  dynamics   and   provide    more gradually  or  slowly  digestible starch.  This effect  on  starch digestion may lead to improvement in energy utilization  and FE (Liu et  al., 2015). Wu  et  al. (2004) reported that  pre- pellet    20%   whole     grain    addition     improved   energy utilization.   Published   studies    on   whole    grain    feeding reported contradictory results. Many  studies  reported beneficial  effect  of whole  grain  feeding on  broiler performance whereas others reported no advantage or even poorer performance (Singh  et  al.,  2014). The  inclusion  of 5-15% whole  wheat in grower and finisher  diets of broilers reduced final body  weight, FCR and  breast  meat  yield  by 3.8,   3.9   and  5.7%,  respectively. Water  intake,   nitrogen excretion and  litter  weight were   decreased by  5.8,   15.5 and 11.0%, respectively (Facts and Figures,  15177).

Whole grain  can be incorporated in poultry  feed  either  pre or post steam  pelleting and offered as either  intact pellets  or as a whole  grain  pelleted concentrate blend  (Moss et  al., 2018).   In    New     Zealand,    whole     wheat   is    usually incorporated  into   broiler   diet   prior   to   steam   pelleting whereas in Australia,  whole  wheat is added  post  pelleting. Effect of pre-  and  post-pellet inclusions  of whole  wheat in broiler  diet on growth performance is presented in Figure 2 (Truong et  al.  2017). The  post-pellet inclusion  of  whole wheat in broiler  diets had greater impacts  compared to pre- pellet  inclusions.  Relative to ground grain control  diet, post- pellet   whole   wheat  inclusion   increased  relative   gizzard weight, reduced gizzard  digesta  pH and  reduced incidence of dilated  proventriculus. The FE was significantly  improved in all whole  wheat included  diets (pre- and post-pellet).

Figure 2: Effect of pre-  and post-pellet inclusion levels of whole  wheat (WW) on growth performance from 7 to 28 days post-hatch. (Truong et al., 2017)

 

MAINTENANCE OF OPTIMAL FEED PARTICLE SIZE

Maintaining optimal size of feed particles is important through different stages of production of poultry rearing. Optimal feed size helps in regulating the feed consumption by the bird. With the increase in age, there is more inclination of the birds towards large and coarse sized feed. During the starter phase, generally crumble feed is provided to the birds with an ideal size of 1-3 mm. Crumbles are generally produced from breaking pellets. Crumbles feeding must be shifted to grower feed during the grower phase and subsequently to the pre-lay diet. Layer diet constitutes three phases and each phase requires well-textured and optimal pellet sized diet. Layer diet must include large particles of limestone or grit (2–4 mm diameter) as extra calcium source for egg production.

Poultry mash feed is generally a mixture of coarse and fine particles. Birds preferentially consume larger feed particles consisting mainly of the coarse-ground maize, which is an important source of gross energy. Diets also contain fine feed particles which are mostly the synthetic amino acids, phosphorus, vitamins, trace minerals and other feed additives. Intake of only large feed particles lead to high energy consumption and low intake of other nutrients. This might reflect in the performance of the birds in terms of egg production and meat yield. Pelleting of feed ingredients solves the problem of selective eating in birds and ensures uniform distribution of nutrients among the entire flock. Fine feed particles are often associated with dust problem and may result in certain respiratory illness.

Milling process has considerable impact on the size and the quality of the feed particles. Different feed ingredients counter differently when subjected to milling procedures. Feed ingredients like maize, soya bean meal etc. are usually in a form that does not require further particle size reduction. Diverse feed ingredients will counteract differently when processed. Moreover, there are certain factors related to feed mills which influence the size of the feed ingredients of a particular diet such as type of mills, speed, shape and condition of the machineries.

Maintaining uniformity in feed particle size is important in order to ensure uniform distribution of the feed in the flock and to reduce the problem of wastage. It can be concluded that giving a mere attention towards feed particle size during feed milling and feed formulation can play a key role in making a remarkable change in the production efficiency.

The importance of feed particle size (granulometry) in laying hens

 Feed structure (feed particle size in particular) is an often-overlooked aspect of egg production. Feed producers should not assume that when chicken feed is uniform in size and homogeneously mixed, it will be provided in the optimal distribution of particle size along the feeders.

Feed granulometry affects the birds’ feed consumption¹, therefore we recommend checking the feed granulometry on a regular basis in the feed mill as well as on the poultry farm. The structure of the feed, including both the particle size and the uniformity depends on many characteristics, for example the ingredient composition, the grain characteristics, and the milling method^2;3.

When feed is presented in the form of a good quality crumb, it will be easier for the chickens to consume, it reduces the time that it takes to consume the feed, and it provides a more uniform composition. As a result, it will encourage the development of the chickens¹. When rearing chicks, it is highly recommended to use a crumble diet from day 0 to 4/5 weeks of age, followed by a mash diet with the recommended particle size as specified below¹.

Please be aware that mash diets are more sensitive to selective eating by the chickens. Particle size is therefore more critical in mash diets when compared to pellets or crumbles³. Besides, particles which are too fine will result in a reduction in feed consumption¹, the right balance between the different particles is therefore key!

If segregation in the silo or feeding system occurs, the different ingredients and nutrients are separating⁴. This can negatively affect the chickens’ daily nutrient intake⁴. Mash feed, with the good particle size distribution, will allow good growth and the proper development of a robust digestive system¹. There is no standard method of particle size analyses yet⁵, however, dry sieving is an appropriate method for non-expanded feed⁵. Therefore, Hendrix Genetics recommends using a small feed sieve for the on-farm analysis that is mentioned in this article. The result of your feed sieve analyses will give you a fast and reliable reflection on the feed structure of the poultry diets. In feed mills, often more accurate dry feed sieves are used to check the structure after grinding and/or after mixing.

THE EFFECT OF FEED PARTICLE SIZE ON THE DIGESTIVE TRACT

The development of the digestive tract is heavily influenced by feed particle size. In general, chickens consuming feed containing large particles will develop bigger and more muscular gizzards, these birds will also develop longer intestinal tracts. The larger the feed particle, the more time the particle will spend in the gizzard. The function of the gizzard is to grind the larger feed particles into smaller particles before they can enter the small intestine. These larger feed particles have also longer transit time when passing through the gastro-intestinal tracts. It is known that birds that are fed with optimum particle sized diets have longer microvilli in their intestines. These longer microvilli result in increased absorptive surface areas, this directly affects the digestibility and nutrient absorption in a positive way.

When the chicken feed is composed of too many fine particles (<1.0 mm), the fine feed particles will pass quickly through the gizzard as no (or limited) grinding is required. Once the particles have passed the gizzard, they will enter the proventriculus. The results of consuming diets that contain too many fine feed particles are a small gizzard, an enlarged proventriculus and reduced intestinal length.

We strongly advise not to feed chicken diets containing too high levels of too fine particles!

RECOMMENDED FEED PARTICLE SIZE
Feed particle size has a large impact on the chickens’ feed intake, dusty feed particles (<0.5 mm) will reduce feed intake greatly. We advise to increase the feed particle size with the age of the chicks. As the chicks grow, they will develop the size of their beaks, their gizzards, and the digestive tract. It is well known that laying hens are selective eaters: laying hens have a clear preference for the larger particles. The older the hen (the chick) becomes, the higher the preference for the larger feed particles. It is recommended to allow the birds time to finish the feed during the middle of the day, this will help to clean the feeders and to prevent the accumulation of small feed particles (referred as empty feeder technique). The larger feed particles are often the coarse grinded grains or corn, while the fine feed particles usually contain the vitamins, amino acids, phosphorus, and the essential trace minerals. As the fine particles play a crucial role in persistency of egg production and eggshell quality selective eating should be always prevented. As an egg producer you should carefully monitor the eating behavior of your flock. The empty feeder technique should already be applied after the first 4-5 weeks of rearing, as this will train the birds to eat well and develop a good crop.

Figure 1. Example of the feed sieve

USING THE FEED SIEVE
Method of sampling
The most important step for accurate analysis is taking a representative sample⁶ from the feeders. Take 5-6 subsamples from different locations, mix them together and reduce the sample size, preferably via a quartering procedure⁶. For the quartering procedure, mix the samples, spread them out, split the sample up again in four equal parts and sieve the two opposite quarters⁶.

Method of sieving
• Remove the lid and fill the first compartment with one cup of feed.
• Bring the lid back on the shaker and make sure it is properly closed.
• Turn the sieve, so it stands vertically with the filled compartment at the top.
• Shake the sieve firmly. Stop shaking when all the fine particles fell to the last compartment for at least 10 seconds.
• Return the sieve sideways and record the values per compartment.
• Calculate the percentage by filling in the values in the grey area by using a calculator or excel.
• Check if the particle size distribution is according to the recommendations.

FURTHER ACTIONS
If the particle size distribution is not according to the recommendation, it is necessary to check all the factors which can affect feed particle size: feed manufacturing, transportation from factory to farm and within the farm, storage, feed pans, feeder management and grinding. If the standard of minimum 85% particles between 0.5 and 3.2 mm in mash cannot be achieved for the starter rearing feed (from 0 to approximately 5 weeks of age), it is preferable to use a diet of good quality crumbs or pellets¹.

Good Physical Quality Of Pellet Feed- Important For Commercial Broiler

The performance of commercial broilers not only depends on a balanced nutritional diet, but also is greatly influenced by form of feed. It is found that pellet feed significantly influences the performance of the flock .

Feed form comprises two distinct elements,

• the microstructure, that describes the particle size and uniformity, and
• the macrostructure that describes pellet size, hardness, and quality.

These two factors are linked as all feeds are first reduced to particles (mash) before being pelleted. Feed is the link factor between formulator(nutritionist) and farm. So, not only nutritional value is important but also delivery of those nutrients through quality feed is equally important.

The good quality of pellet starts from good grinding

Grinding the feed ingredients into finer particles is a key factor to start quality pellet manufacturing. Particle size should be so fine that it may impact digestibility of feed. The geometric mean diameter (GMD) of the fine particles is always equal to or lower than that of mash feed, and these particles may cause a nutritional imbalance in feed chemical composition, which may negatively affect the bird performance (Muramatsu et al., 2015).Small particle size of feed causes gizzard atrophy and intestinal hypertrophy caused by bacterial fermentation

When particles are large, breakdown of feed particles at the proximal small intestine will be slower. Gizzard is the pacemaker of the GI tract. When finer feed is given, gizzard acts as a transit rather than a grinding organ. Less retention in gizzard leads to less exposures to proventriculus enzymes. It is found that a finely ground diet (560μm) compromised nutritional metabolism as particle size affects ME, nitrogen retention and DM retention. If the particle size is small ( 800 micron) feed intake is significantly reduced. On an average, a reduction of mean particle size of 100 micron will lead to a decreased feed intake of 4%.

If the feed particles are too coarse, it makes it difficult to mix a homogenous diet and feed selection. The best performance is obtained with the medium size particles 1.13 mm to 1.23 mm. It is true that a more coarsely ground maize leads to improved nutrient utilization by the birds and this remains the case when after pelleting, although the pellet press will regrind many of the larger particles. Roller mill tends to produce particles evenly distributed across a weight range, whereas a hammer mill tends to produce a greater proportion of fines and coarse particles.

Diet particle size positively influences the performance and organ and tissue growth of 21-72-day old broilers (Maiorka et al., 1998). Feed wastage tends to be higher when mash feeds are fed. In addition, the bird covers each with mucin before swallowing, which needs both protein and energy.

Nowadays most of the broiler feeds are fed in pelleted form. Injecting steam into the feed during conditioning and subsequent pressing through pellet die improves pellet durability. Pelleting is defined as the agglomeration of smaller particles into larger particles through a mechanical process combining moisture (through steam), heat, and pressure. (Abdollahi et al.,2013)

Why Pellet feed so good for commercial broiler chicken ?

It is now well-established commercial activity to manufacture and offer pellet feed in commercial broilers because of following reasons:

• Feed homogeneity is improved because feed separation is greatly reduced
• Less feed is wasted when pellets are fed
• Pelleting should slightly improve the energy value through the chemical changes brought about by heat moisture and pressure
• Much of the improvement is measured energy value of pellets results from the fact that birds spend less time eating them and so their energy requirement for eating and digestion is reduced. Although pellet size may play a role in feed intake.
  ❖ Lilly et al. (2011) found for every 10-percentage-point increase in whole pellets there was a 0.4-point improvement in FCR and breast weight, while increasing FI
  ❖ Glover et al. (2016) found broilers fed a high pellet quality (90:10 pellet: fine) diet achieved a low FCR and high carcass weight, indicating production savings relative to a ground pellet diet of $0.05 to $0.03/kg of carcass weight

The Best suitable methods for measuring pellet quality

Apart from proximate values of feed ingredients, some other physical qualities like abrasiveness, pellet quality factor, color and density impact on pellet quality and durability. Pellet quality factor (PQF) has a score from 0 to 10 where o predicts poor quality and 10 indicates good pellet binding quality. Abrasiveness factor of the ingredient is just opposite to the pellet quality factor. Lower the factor value higher is the binding capacity.

Young (1962) used the technique consisting of an inclined screw, a hopper, and bucket elevator conveyor to measure pellet durability. 23 kg of pellets were continuously passed through this system for a period of 10 min. At the end of the test, the pellets were separated and the fines were removed. Calculation of the Pellet Durability Index (PDI) was percentage of the mass of surviving pellets over the total mass of pellets.

Several laboratory methods developed different technique to measure the durability of pellets like:

Tumbling box method: Commonly used method and a recognized standard in the feed industry in North America(Winowiski, 1998). The tumbling box technique uses 500 g of pellets, from which the fines have been separated. The pellets are placed in a box that revolves for the time frame of 10 min at a speed of 100 rpm. After this process, the pellets are screened on a mechanical sieve shaker. The PDI is calculated as the weight of the pellets retained on the screen divided by the total weight of pellets. (ASAE Standards, 2003)

Holmen durability tester: It is a pneumatic method of measuring the durability of the pellets. A sample size of 100 g of pellets is placed through tubes with high velocity air for 30 to 120 s, replicating the handling process. Breakage occurs when pellets strike the right-angle corners of the tester. The PDI is calculated as the weight of the pellets retained on the screen divided by the total weight of pellets. (ASAE Standards, 2003)

The Stokes hardness tester: The tester comprises a calibrated spring, a cone with a tip, and a plate supporting the opposite side of the cone. The cone tip applies pressure on the cylindrical surface of the pellet during testing. Pressure is controlled by a screw turned by hand to compress the spring. Only 10 pellets are placed in the tester, and pellet hardness is expressed in psi (Young, 1962).

Three major factors responsible for good quality of pellet feed:

Formulation: Formulation plays a vital role in pellet quality but it is not the only factor. Ingredient composition like moisture percentage, fat percentage, protein percentage, starch content are important nutritional factors to be considered for good quality pellet production. Corn-soya diet is considered as the best formulation for getting better pellet quality. Dietary inclusion of 10-15% of wheat or wheat middlings or addition of as little as 5% sunflower oilcake will result in good quality pellets. It is found that addition of 1% oil in diet reduces pellet durability by 8-10%. Each 10% increase in fines is equal to about 0.016 kcal per kg reduction in energy. Moritz et al. (2002) stated that addition of two oils at graded levels (30 g/kg and 65 g/kg) in broiler diets and observed that PDI decreased from 81.6% to 62.1% with the highest oil inclusion.

Adding pellet binder in diet improves binding capacity and durability of pellet. There are several available options like synthetic polymer-based binder, natural resin-based binder, lignosulphonate and bentonite. But selection of best binder is very critical and should be based on higher pellet quality factor and mode of binding. Synthetic resin has pellet quality factor 40 and can irreversibly bind at high pellet temperature and conditioning moisture.

Processing equipment: Quality and die capacity are important for good quality pellet. Compression length and diameter of the compression hole are important factors for deciding the pellet quality. If thickness of the die increases, then pellet durability will improve but inversely throughput of pellet will decrease. So, trading off these two factors are very important. Similarly die set up, cooler set up and screen set up are deciding factors for good quality pellets.

Processing standard: As discussed earlier, grinding and pulverization during milling is another deciding factor for good quality pellets. In commercial broilers below 300-micron particle size during grinding helps in better gelatinization during conditioning resulting in a good durable pellet. Similarly standardizing the conditioning parameters like temperature, moisture percentage, steam injection and steam pressure, retention time are equally important. Briggs et al. (1999) stated that increasing retention time frame from 5 s to 15 s increased pellet durability by 4.5%.

 Feed Mill Management

Feed generally is considered to be the major input for livestock, poultry production and may account for 70-80 percent of total production cost. So, if we can produce high quality feed at most economical way, it will not only cut the cost of production, but also yield high profits. One needs to produce consistency in quality and quantity 365 days a year. For this consistent quality & quantity – feed mill management plays an important role; that mainly involves 4 M’s:

• Material Management
• Machines Management
• Manpower Management
• Money Management

1. Material Management:

Management

Material mainly includes; raw material & finish goods management like moisture of raw material, protein, ash, silica, oil range in grains. Quality check in terms of toxicity in grains. All these parameters plays a vital role in feed nutrition and profit statement, as small miscalculation may leads to huge financial loss as mentioned:

Moisture loss

Moisture loss is calculated on the basis of average moisture of raw material batch minus average moisture of finish goods. Example – let us assume a standard broiler feed formulation as mentioned:

• Maize          – 60 % in formulation by weight having 14 % moisture
• Soya Doc     – 25 % in formulation by weight having 9.5 % moisture
• DORB           – 10 % in formulation by weight having 9 % moisture
• Other material like MBM, gluten etc. – 5 % in formulation by weight having 9 % moisture

Considering 1000 kg batch; total average moisture in raw material batch is:

600 x 14 % + 250 x 9.5 % + 100 x 9 % + 50 x 9 % = 121.25 kg (moisture/water) in 1000 kg of grain. Equals to 12.125 % average moisture in complete batch…… (a)

Ideal moisture of finish pellets in bag is considered between 11 to 12 %, depending upon the atmospheric temperature & humidity. Cooling is an evaporative process, so moisture reduction is essential. But there may be times when over cooling happens leading to over drying. If average moisture of finish good is 10.5 %, considering the statement ….a, average moisture loss or shrinkage will be 12.125 – 10.5 = 1.625 %.

For a feed mill manufacturing 200 MT a day, calculation of 1.625 % @ average price of 24 rs/kg – whole batch; daily loss = 78,000 rs . Apart from this monetary loss there is fluctuation in formulation too.

With net profit margins in some feed companies being low as 1 to 2 %, this factor alone could influence whether or not that company returns a profit or loss, so it really is a vital part of feed mill management.

Same calculation can be done in terms of protein, energy & oil requirement as per breed. Extra nutrients may leads to financial loss and low nutrition calculation provides less growth in birds and animals.

Following process can be followed to reduce /monitor this loss as mentioned:

• Moisture check in raw material before or at the time of procurement.
• Sampling at different locations – after batching – grinding – conditioning – pelleting – cooling and final product for moisture check – as and when required.
• Corrective action as per reports like – temperature at grinding, moisture addition in mixer, quality & quantity of steam, retention time in conditioner, cooler setting in terms of bed level and sensor , blower valve setting as per temperature , cleaning of cyclone & ducts , moisture and weather conditions etc.
• Various automation modules help in inventory management of raw material by getting feedback from weigh scale ( raw material in ) , Material stock in ware house & daily weight of finish goods out from feed mill . (Every 10th day – thrice a month)
• After all corrective measures; there is still some amount of shrinkage (due to limitations in raw material availability as per season, price of grains, chances of mold /fungus in finish feed in rainy season, machinery behavior & limitation w.r.t. different formulations etc.) ; it’s wise to consider 0.5 % – 0.6 %  process loss in cost estimations . Also each plant should recognize where shrink or gain may occur and make the best possible effortsto control and minimize these losses

2. Machines Management:

Machines management mainly includes – Optimum production process parameters, Preventive maintenance, general hygiene & safety etc.

1. Process Parameters:

Process parameters are important part of any quality control program. This is the process of measuring specific components of feed or ingredients at different stages like batching, grinding, mixing, conditioning, pelleting, cooling, crumbling, screening and packing.

In batching we have to take care that the initial moisture of the combine raw material batch should not exceed 12-12.5 %;

In grinding we have to maintain following parameters: (for poultry broiler pellets)

• Particle Size:More than 80 % of average particle size should be below 1 mm.
• Gap between Hammer tip & Screen:As for fine grinding we need lesser gap between hammer tip & screen and for coarse grinding we need more gap between hammer tip & screen. There should be gap adjustment feature in hammer mill for different types of grinding texture required.

  For all types of grinding solution Lark provides QGA “Quick Gap Adjustment”, as its name implies this technology is a boon for grinding different sizes of products as Fine /Medium / Coarse by quick change of gap between hammer tip and screen.

• Tip speed of hammer mill:Ideal Tip speed for a hammer mill should be 19000 -22000 FT/Min
• Specific energy of hammer mill:Average ideal power consumption of grinding unit should not be more than 9 units/ton.
• Temperature difference; Material in and out:Maximum difference in the grinding temperature (material in versus material out) should not be more than 5 degrees.

In mixing we have to maintain following parameters:

• CV should be less than 5.
• Oil should be added after dry mixing (Medicine) of minimum 90 to 120 seconds.

In Conditioning & Pelleting:

• Minimum 60 seconds of retention time with adjustments to decrease or increase the retention time.
• Minimum 1.5 to 2.0 % moisture should be added through conditioners.
• Double shaft design for better mixing of steam.
• Multi –Point steam injections.
• Temperature range should be 75-85 degrees.
• Steam pressure at boiler should be 8.5-9.5 kg/cm2
• Steam pressure after PRV should be 2.0 to 2.5 kg/cm2.
• Steam should be Dry Saturated.
• PDI of Pellets should be more than 85 %.
• Specific energy consumption of pellet mill should not be more than 15 units/ton.

Cooling

• Maximum variation in temperature after pellet cooler should not be more than + – 5 degrees of ambient temperature.
• Moisture of pellets after cooler should be in between 11.0 to 11.5 %

Crumbling & Screening

• Fines % in crumbling process should not be more than 25 %.( depend upon different formulation , particle size required and PDI)
• In any case recycling in Finisher Pellet, Finisher Crumbs, Starter & Pre-Starter should not be more than 10 %, 15 %, 18 % and 25% respectively.
• Ideal moisture in finish feed should be in between 11.0 to 11.5. Too high moisture lowers the feed quality and leads to toxicity or fungus and too less moisture leads to process loss.
• Fines percentage ( below 1 mm ) in packing bags in Finisher pellet , Finisher crumbs , Starter and pre-starter should not be more than 4 % , 7 % , 10 % and 12% respectively

Preventive Maintenance

Well, “A stich in time saves nine”. Maintenance is an important part of feed mill management. The main purpose of regular maintenance is to ensure that all equipment required for production is operating at 100 % efficiency at all times. It must be a part of the daily schedule.

As we all know, livestock needs feed on daily basis and there is no space for unwanted breakdowns in feed mills. Every feed miller must be aware of the importance of preventive maintenance. For this we have developed special checklists & formats on daily , weekly , monthly and yearly basis in different languages.

Few check points for machinery are:

• Intake Chain
  •       Checking of Motor, Gear Box and Chain condition
  • Abnormal Sound
  • Check Drag Chain Slackness
  • Greasing of Bearings
  • Checking of PVC Scrapers
• Jute Remover
  • Rotor Change
  • Greasing
• Elevators
  • Check Tension in Belts
  • Belts Alignment
  • Cleaning the Boot of Elevator
  • Cleaning Top end of Elevator
  • Tightening of Bucket Bolts, Joints
  • Greasing of Bearings
• Magnet
  • Cleaning after every 4 hours
• Hammer Mill
  • Check Hammer Edges
  • Screen Conditions
  • Vibration
  • Abnormal Noise
• Pellet Mill
  • Check wearing condition of dies & rolls
  • Greasing of bearings
  • Check for any vibration & noise
  • Check position of cutting knives & deflectors.
  • Check gap between die & rolls.
• Crumbler
  • Check wearing of crumbler rolls
  • Greasing of Bearings
  • Leakage of unbroken pellets.

Hygiene &safety:

The ability to protect raw materials and finished feeds from harmful contaminants is crucial to ensure animal performance. By improving the microbiological quality of the feed, animals can utilize the full nutritional benefit of each ingredient with lowered risk for sickness and transmission of diseases.

Raw materials and feeds constitutes as one of the most important causes of microbial contamination, such as Salmonella and Escherichia coli.Hence controlling the raw material quality and other process parameters during the feed production is very important to maintain the feed hygiene. Few other process parameters or checkpoints which help to maintain feed hygiene are:

• Intake & Storage
  Storage of raw material in round bins or bins without dead corners helps to prevent sticking of materials .Bin cleanliness in the feed storage area is essential & should be monitored regular basis. Sticking of material & dust not only induces fungus growth but also may leads to “GRAIN DUST EXPLOSIONS”.

  Moving and handling grain creates grain dust, when combine with other components like oxygen, ignition source, dispersion can result in grain dust explosions. Proper monitoring of cleanliness, leakages at ducts & connecting chutes, fines/dust at elevator pits should be done on regular basis to avoid such incidents and to maintain proper hygiene at feed mill.

• Liquid, Steam & oil addition
  Proper cleaning on regular basis is required where application of steam, oil or liquids comes along with grinded ingredients. For reference see the below attached images of conditioners and mixer with feed stuck at paddles, surface and shaft leading to fungus / bacterial growth.
• Sampling:
  Sampling at different stages; after batching, mixing, grinding, conditioning, pelleting, cooling & bagging helps to control moisture, detect fungus growth and other quality parameters.

3. Manpower Management:

Manpower management involves effective utilization of labor &staff, trainings as per requirement,defining & delegating duties & responsibilities of feed mill staff as mentioned:

Responsibilities of Plant Manager:

• Plan, organize, direct and run optimum day-to-day operations to exceed our customers’ expectations
• Increase production, assets capacity and flexibility while minimizing unnecessary costs and maintaining current quality standards
• Be responsible for production output, product quality and on-time shipping
• Allocate resources effectively and fully utilize assets to produce optimal results
• Implement strategies in alignment with strategic initiatives and provide a clear sense of direction and focus
• Monitor operations and trigger corrective actions
• Share a trusting relationship with workgroup and recruit, manage and develop plant staff
• Collect and analyse data to find places of waste or overtime
• Commit to plant safety procedures
• Develop systems and processes that track and optimise productivity and standards, metrics and performance targets to ensure effective return on assets
• Address employees’ issues or grievances and administer collective bargaining agreements
• Influence and learn from below
• Stay up to date with latest production management best practices and concepts

Responsibilties of Pellet operator

• Follow all established plant safety rules.
• Keep work area clean & orderly.
• Follow a schedule of routine cleaning, greasing & maintenance for all pelleting and related equipment and advise appropriate personnel when maintenance is required.
• Properly adjust pellet mill rolls, scrapper, crumbler rolls and other equipment to maximize efficiency and equipment life.
• Operate the pellet mill with proper moisture, heat and production rates to efficiently produce products while maintain pellet quality.
• Tends machine that presses ingredients into feed pellets for poultry stock feed
• Turns steam valves to regulate temperature of mash feed.
• Observes ammeter & feed material to pellet mill by increasing/decreasing the speed of feeder as per motor amperage.
• Turn steam valves to regulate temperature of molasses
• Adjust flow of air to cool pellets in cooler.
• Follow procedure for fitting a new die, starting a new die, flushing dies, removing dies, fiiting roll shells, rings etc. concerned with pellet mill.

Responsibilties of Boiler operator

• Operates fired boilers to generate required steam.
• Observes pressure, temperature, and draft meters on panel to verify specified operation.
• Turns valves and adjusts controls to set specified fuel feed, water level, and steam pressure of boiler
• Testing and treat boiler feed water, using specified chemicals.
• Activate valves to maintain required amounts of water in boilers, to adjust supplies of combustion air, and to control the flow of fuel into burners
• Adjust controls and/or valves on equipment to provide power, and to regulate and set operations of system and/or industrial processes.
• Analyze problems and take appropriate action to ensure continuous and reliable operation of equipment and systems
• Monitor and inspect equipment, switches, valves, gauges, alarms, safety devices, and meters to detect leaks or malfunctions, and to ensure that equipment is operating efficiently and safely.
• Perform or arrange for repairs, such as complete overhauls, replacement of defective valves, gaskets, or bearings, and/or fabrication of new parts
• Observe and interpret readings on gauges, meters, and charts registering various aspects of boiler operation, in order to ensure that boilers are operating properly.
• Test electrical systems to determine voltages, using voltage meters
• Maintain daily logs of operation, maintenance, and safety activities, including test results, instrument readings, and details of equipment malfunctions and maintenance work.

Responsibilties of Electrician technician

• Troubleshoots, repairs and maintains electrical distribution systems including electric motors, electric controls, fire alarms, and clock systems
• Assemble, install, test, and maintain electrical or electronic wiring, equipment, appliances, apparatus
• Diagnose malfunctioning systems, apparatus, and components, using test equipment and hand tools, to locate the cause of a breakdown and correct the problem.
• Connect wires to circuit breakers, transformers, or other components
• Advise management on whether continued operation of equipment could be hazardous
• Test electrical systems and continuity of circuits in electrical wiring, equipment, and fixtures, using testing devices such as ohmmeters, voltmeters to ensure compatibility and safety of system
• Install ground leads and connect power cables to equipment, such as motors
• Perform business management duties such as maintaining records and files, preparing reports and ordering supplies and equipment.
• Repair or replace wiring, equipment

Responsibilties of Maintenance Personnel

• Responsible for the completion of all maintenance service requests as assigned
• Maintain inventory controls for cost effective operations
• Schedule and complete the “Preventative Maintenance Program”
• Assure safety standards are used which comply with all machinery.
• Periodically grease machinery & all maintenance as per schedule.

4. Money Management:

Money Management involves all calculations like financial statement in terms of raw material cost, processing cost,consumables, bank interests, bad debts, credit flow in market, investment on dealers, advertisements &promotions, all hidden expenses etc.

 Conclusion:

During processing, reduction of particle size is a significant influencing factor for better pellet quality and positively influences the performance of the birds. Formulation especially in terms of inclusion of certain feed ingredients are to be considered judiciously. Similarly standardization of processing equipment and process flow are equally important for pellet quality consistency.

Particle  size of grains  and  by-products used  in broiler  feed affects   growth  performance.  Particle   size   has   positive impact on the development of GIT mainly the gizzard development and functionality. Large  particle  size supports gizzard  functions   and  gut  health  development in  broilers. Impact of particle  size is clearer  for mash diets compared to pellet/crumble diets.   Use  of  large  particle   size  of  grains increases the  Lactobacilli counts  and reduces the population of pathogenic bacteria. Whole  grain feeding improves digestive functions  and encourages the colonization of beneficial  bacteria  in gut of broilers.

FEED PROCESSING- AND QUALITY

CONCEPT OF FLOATING FEEDS,SINKING FEEDS & TRADITIONAL FISH FEEDS MANUFACTURING TECHNOLOGY IN INDIA

Compiled  & Shared by- Team, LITD (Livestock Institute of Training & Development)

 

Image-Courtesy-Google

 

Reference-On Request.

References
¹ Nutrition Management Guide. Hendrix Genetics. https://layinghens.hendrix-genetics.com/en/technical-support/nutrition/
² Influence of particle size of the main cereal of the diet on egg production, gastrointestinal tract traits, and body measurements of brown laying hens. Herrera, J., et al. 2017, Poultry Science, pp. 96: 440- 448.
³ Implication of milling methods, thermal treatment, and particle size of feed in layers on mineral digestibility and retention of minerals in egg contents. Hafeez, A., et al. 2015, Poultry Science, pp. 94: 240-248.
⁴ Effect of Feed Segregation on the Commercial Hen and Egg Quality. Tang, P., Patterson, P.H. and Puri, V.M. 2006, The Journal of Applied Poultry Research, pp. 15: 564-573.
⁵ The effects of particle size, milling method, and thermal treatment of feed on performance, apparent ileal digestibility, and pH of the digesta in laying hens. Ruhnke, I., et al. 2015, Poultry Science, pp. 94: 692-699.
⁶ Servi-Tech Laboratories. Feed Sampling Procedures. Servi-Tech Laboratories. [Online] 2019. https://servitechlabs.com/Services/Feed/FeedSamplingProcedures/tabid/126/Default.aspx