Factors that Affect Pellet Quality： A Review

Pelleting is the most popular thermal processing technique in poultry industry. Birds fed pelleted diets have greater feed intake and weight gain, and better feed conversion ratio. However, this better performance can only be achieved, if the pellets remain intact until they are ingested by the birds. Many factors may affect pellet physical quality, such as feed nutritional composition, ingredient particle size, conditioning temperature and time, feed moisture, etc.. Despite their importance, sometimes these factors are not managed properly, therefore, pelleted feed may not contain a high amount of intact pellets. In addition, the possible interactions among these variables may yield different responses in comparison with those expected when individual factors are considered. Very few experiments have been conducted to evaluate the impact of combined factors on pellet quality. This may be explained by the presence of many qualitative and quantitative factors in the manufacturing process. Research indicates that heat processing and feed formulation, especially fat inclusion level, are the factors which have the biggest influence on pellet quality. Strategies, such as the expansion process and fat inclusion restriction or post pellet liquid fat application could be implemented to produce high physical quality pellets. More research is needed to identify which factors have a positive or negative effect on pelleting process and to find new strategies to improve pellet physical quality.

Assessment of densified fuel quality parameters:A case study for wheat straw pellet

An investigation was conducted to examine the impact of additive mixing with wheat straw(WS)for pellet making.This study manufactured seven types of pellets with different additive combina-tions to evaluate pellet quality characteristics and their relationships.A laboratory-type hammer mill and a pellet mill were used for feedstock preparation and pellet production.Experimental investigations showed that the lignin content increased from 7.0%to 13.1%,which was a primary need for pelletization.Also,the heating value rose from 17.02 to 20.36 MJ/kg.However,the ash content also increased from 7.09%to 16.2%.Results showed that dimension(length and diame-ter),durability,and tensile strength increased significantly with additives while the fines content decreased.The fines content had an inverse relationship with durability and strength.Wheat straw(60%),together with 10%sawdust(SD),10%corn starch(CS),10%bentonite clay(BC),and 10%biochar(BiC),was optimal with good pellet performance(T7).In addition,both the T5 pellets(70%WS,10%SD,10%BiC,and 10%BC)and the T6 pellets(70%WS,10%SD,10%BiC,and 10%CS)provide suitable quality according to EN plus 2015 standard requirements.The ash content of produced pellet was higher than the recommended value,which suggests that further research onto the alternative additive use for ash reduction is needed.

Effects of feeding rate and formula fineness degree of ring die pellet mill on mechanical property, physical quality, energy requirements, and production cost of poultry diets

The effect of a machine feeding rate(FR;1,1.5 and 2 Mg/h)and/or three levels of selected fineness degree(FD;3,5 and 7 mm)on machine performance,pellet physical parameters,required energy and production cost of three main types of broilers diets were examined in this experiment.The examined broiler diets were formulated to meet the Ross 308 strain requirements.A complete factorial design(3×3×3)was used to identify the effects of studied factors on the pellet mill machine and pellet production.The obtained results indicated that the pellet mill productivity significantly(p˂0.001)improved through increased pellet mill feeding rate level.In addition,the machine pelleting efficiency was found to be significantly affected by all studied variables and their interactions.While the total power consumption of the machine showed no variations under the impact of the tested factors or with any of their combinations.Regarding the pellet physical quality indices,all broiler diets with all selected FD and lower FR had the maximum durability and bulk density levels.Furthermore,lower feeding rates were associated with higher hardness degrees.The lowest production costs were substantially correlated with high FR and intermediate FD(5 mm).Furthermore,production costs were determined to be reduced in finisher broiler diets under different feeding rates.Moreover,manufacturing costs of finisher broiler meals were observed to decrease in several feeding rates.Overall,these findings indicate the capabilities of producing high-quality pellets and reducing the needed production costs by optimizing feeding rates to 2 Mg/h and 2 mm fineness in broiler diets.

Effects of raw material extrusion and steam conditioning on feed pellet quality and nutrient digestibility of growing meat rabbits

This study was conducted to investigate the effects of raw material extrusion and steam conditioning on feed pellet quality and nutrient digestibility of growing meat rabbits, in order to determine appropriate rabbit feed processing methods and processing parameters. In Exp. 1, an orthogonal design was adopted.Barrel temperature, material moisture content and feed rate were selected as test factors, and acid detergent fiber(ADF) content was selected as an evaluation index to research the optimum extrusion parameters. In Exp. 2. a two-factor design was adopted. Four kinds of rabbit feeds were processed and raw material extrusion adopted optimum extrusion parameters of Exp. 1. A total of 40 healthy and 42-day-old rabbits with similar weight were used in a randomized design, which consisted of 4 groups and 10 replicates in each group(1 rabbits in each replicate). The adaptation period lasted for 7 d, and the digestion trial lasted for 4 d. The results showed as follows: 1) ADF was significantly affected by barrel temperature(P < 0.05); the optimum extrusion parameters were barrel temperature 125℃, moisture content 16% and feed rate 9 Hz. 2) Raw material extrusion and steam conditioning both significantly decreased powder percentage, pulverization ratio and protein solubility(P < 0.05), significantly improved hardness and starch gelatinization degree of rabbit feed(P < 0.05). They both had significant interaction effects on the processing quality of rabbit feed(P < 0.05). 3) Extrusion significantly improved the apparent digestibility of dry matter and total energy(P < 0.05). Extrusion and steam conditioning both significantly improved the apparent digestibility of crude fiber(CF), ADF and NDF(P < 0.05), but they had no interaction effects on the apparent digestibility of rabbit feed. Thus, using extrusion and steam conditioning technology at the same time in the weaning rabbits feed processing can improve the pellet quality and nutrient apparent digestibility of rabbit feed.

A novel approach to enhance decrepitation temperature and reducibility of ultrafine iron ore concentrate pellets

Utilizing ultrafine iron ore concentrate for pellet production can expand domestic iron ore resources in China and promote the utilization of low-grade ores.However,a challenge arises with the low decrepitation temperature and reducibility in the preparation process of ultrafine iron ore concentrate pellets.To address the challenge,a novel approach was proposed,which incorporated straw powder as an additive to enhance pellet porosity,thereby improving the decrepitation temper-ature and reducibility of ultrafine iron ore concentrate pellets.The effect of varying proportions of straw powder(0.0-2.0%)on the characteristics of ultrafine iron ore concentrate pellets was examined.Results indicate that at a 2.0%straw powder ratio,pellet decrepitation temperature notably rises from 380 to 540℃,while the reducibility index escalates from 25.7%to 48.1%.Nevertheless,the addition of straw powder results in diminished drop strength,compressive strength of green pellets,and cold crushing strength of fired pellets.In addition,enhanced pellet reducibility leads to exacerbated reduction swelling index and reduction degradation index.Despite these effects,all parameters remain within an acceptable range.