Effect of Sample Preparation and Extended Mix Times with Different Salt Particle Sizes on the Uniformity of Mix of a Corn-Soybean Meal Swine Diet

The uniformity of a feed mixture is determined from the coefficient of variation (CV) of 10 samples in a single batch of feed. The feed industry standard is a CV of less than 10% using a single source tracer, such as salt, trace minerals, or iron filings. The objectives of these experiments were to determine the effects of 1) extended mix time, 2) particle size of the marker, and 3) sample preparation on the CV in a corn-soybean meal swine diet. In Experiment 1, treatments were arranged in a 3 × 7 factorial with main effects of 3 salt particle sizes (fine-350 μm, medium-464 μm, and coarse-728 μm) and 7 mix times (2, 3, 5, 15, 30, 45, and 60 min). In Experiment 2, treatments were arranged in 2 × 3 × 3 factorial with 2 sample preparations (unground vs. ground), 3 salt particle sizes (fine-350 μm, medium-464 μm, and coarse-728 μm) and 3 mix times (3, 30, and 60 min). There were 3 replicates per treatment and 10 samples per replicate. Salt concentrations were determined using a Quantab® Chloride Titrator. The result of Experiment 1 indicated no interaction between mix time and salt particle size. The extended mix time did not result in segregation (P = 0.307). Particle size of the salt significantly affected the uniformity of mix (P \u3c 0.0001; 21.2, 8.6, and 7.9% CV for the coarse, medium, and fine salt, respectively). The results of Experiment 2 indicated no interaction of sample preparation, salt particle size, and mix time. However, there was interaction between sample preparation and salt particle size (P = 0.0002). The difference in the CV% between unground and ground samples was significantly greater for the mixture with coarse salt (8.89 %) than the mixture with fine (1.35 %) and medium salt (2.59 %). The ground treatment had a significantly lower CV than the unground treatment (P \u3c 0.0001; 8.7 and 13.0 for ground and unground samples, respectively). The fine and medium salt treatments had significantly lower CV as compared to the coarse salt treatment. (P \u3c 0.0001; 7.4, 7.7, and 17.4 for fine, medium and coarse, respectively). These results indicated that feed did not segregate after mixing for up to 1 h. The greater number of particles per gram of the marker (in this case salt) increased the precision of the analysis, likely due to an increased probability that the marker was present in proportionate quantities in the sample tested. However, when coarse salt is used in the manufacturing process, the samples should be ground prior to analysis

The Effect of Liquid Application Times, and Mixer Types with Different Wet Mix Times on Uniformity of Mix

Liquid addition systems are often designed to add liquid ingredients with the shortest application time in order to increase the batching capacity and efficiency of the mixing process. The quantity of liquid that is added into the mixer affects batch cycle time, particularly when there is a programmed “wet mix” time, or mixing time after liquid application has completed. Shorter application time of liquids typically produces a larger droplet size, which may lead to greater clumping tendencies in the feed and less uniformity of liquid incorporation. Two experiments were conducted to determine the effect of liquid application time and wet mix time on the uniformity of mix in different mixers. In both experiments, treatments were arranged in a 2 × 3 factorial. Experiment 1 used a double ribbon mixer with 2 liquid application times (20 vs. 30 s) and 3 wet mix times (15, 30, and 45 s). Experiment 2 used a single shaft paddle mixer with 2 liquid addition times (15 vs. 30 s) and 3 wet mix times (15, 30 and 45 s). Ten samples were collected, and coefficient of variation (% CV) determined within those samples. Each treatment had 10 separate replicates. Experiment 1 indicated that wet mix time (P \u3c 0.0001), but not application time (P = 0.653) or the interaction (P = 0.638), impacted % CV in the double ribbon mixer. As wet mix time increased, % CV decreased in a quadratic manner (P = 0.02; 37.2, 18.6, and 10.8% for 15, 30, and 45 s wet mix time, respectively). In Experiment 2, both wet mix time (P = 0.030) and application time (P = 0.001) impacted % CV, but not their interaction (P = 0.290). A longer application time led to a better uniformity of mix (P \u3c 0.05; 13.5 vs. 9.8% CV for 15 vs. 30 s liquid application time), as did a longer wet mix time (P \u3c 0.05; 17.0, 9.8, and 8.2% CV for 10, 20, and 30 s wet mix time, respectively). These results suggest that extending liquid application times may be beneficial in some mixers, and underscore the importance of a sufficient wet mix time to maximize the uniformity of liquid incorporation

Effect of Pellet Cooling Method, Sample Preparation, Storage Condition, and Storage Time on Phytase Activity of a Swine Diet

Temperature and moisture content have been identified as two factors that influ­ence enzyme inactivation. Phytase may be further degraded in feed samples if there is moisture left in the sample and it is not properly stored prior to analysis. Therefore, the objective of this experiment was to determine the effect of cooling method, sample preparation, storage condition, and storage time on phytase stability. In Exp. 1, treat­ments were arranged in 2 × 2 factorial with main effects of sample preparation (none or freeze-dried) and storage condition (ambient storage or freezer storage). Diets were mixed 3 separate times to provide 3 replicates per treatment. The result of Exp. 1 demonstrated that there was no interaction between drying process and storage condi­tion for mash samples collected from the mixer. The sample drying process and storage condition did not impact the phytase stability. In Exp. 2, treatments were arranged in a 2 × 3 factorial with main effects of cooling method (counterflow cooler or freezer) and sample preparation (non-dried then freezer storage, freeze-dried then freezer storage, freeze-dried then ambient storage). The diet was steam conditioned for approximately 45 s at 185°F using a 5.1- × 35.8-in single shaft conditioner of a pellet mill (California Pellet Mill model Cl-5, Crawfordsville, IN) at a production rate of 2.2 lb/min by holding the feeder at a constant speed setting. The sample was collected at the end of the conditioner and did not pass the pellet die. The conditioner was run 3 separate times to provide 3 replicates for each treatment. The result of Exp. 2 demonstrated that there was no interaction between the cooling method and sample preparation for phytase stability of conditioned mash samples. The cooling method and sample prepara­tion did not affect the phytase stability. In Exp. 3, treatments were arranged in a 5 × 3 × 2 factorial with main effects of cooling method (none, heat diffusion, experimental fan cooler, experimental counterflow cooler, or freezer), storage condition (ziplock/ ambient, ziplock/frozen, and vacuum/frozen), and storage time (1 or 3 wk.). The diet was steam conditioned for approximately 45 s at 185°F and pelleted using a pellet mill (California Pellet Mill model Cl-5, Crawfordsville, IN) equipped with 0.16- × 0.50-in die. The diet was pelleted at a production rate of 2.2 lb/min by holding the feeder at a constant speed setting. The pellet mill was run 3 separate times to provide 3 replicates for each treatment. The result of Exp. 3 demonstrated that there were no three-way and two-way interactions among cooling method, storage condition, and storage time (P \u3e 0.686). The cooling method, storage condition, and storage time did not impact phytase stability (P \u3e 0.348). Therefore, freeze-drying, vacuum sealing, and freezing were not required when the feed samples were analyzed within 3 weeks of production. However, conditioned mash and hot pellet samples should be dried prior to sending the samples to the lab to prevent mold growth

The Impact of Fines Inclusion Level and Conditioning Temperature on Pellet Quality and Energy Consumption

The advantages of pelleted feed can include improved handling, palatability, and nutrient availability. Poor pellet quality, however, can diminish these positive returns and lead to customer complaints. Thus, commercial feed mills may remove fines with a screener after cooling in order to provide a consistent product to customers. There are limited data on the effect of returning pellet fines back to the pellet mill on pellet quality and pellet mill efficiency. The objective of the following 2 experiments was to determine the effect of fines inclusion level and conditioning temperature on pellet quality and energy consumption. Experiment 1 treatments were arranged in a 3 × 2 factorial design of fines inclusion level (0, 10, and 20%) and conditioning temperature (170 and 180°F). Experiment 2 treatments were arranged in a 3 × 2 factorial design of fines inclusion level (0, 10, and 20%) and conditioning temperature (175 and 185°F). The results of Experiment 1 demonstrated there was no interaction between fines inclusion level and conditioning temperature on pellet durability index (PDI) (P \u3e 0.348). Increasing conditioning temperature from 170 to 180°F increased (P \u3c 0.003) PDI by 0.6 and 4.3% for both the standard and modified methods, respectively. There was a linear increase (P \u3c 0.032) in standard and modified PDI as the fines inclusion level increased. The results of Experiment 2 demonstrated that there was an interaction between fines inclusion level and conditioning temperature for modified PDI (P \u3c 0.001). When the diets were pelleted at 185°F, increasing the fines inclusion level increased the modified PDI. However, there was no significant difference for modified PDI of the diets with 0, 10, and 20% fines inclusion level when they were pelleted at 175°F. For starch analysis, there was no interaction between fines inclusion level and conditioning temperature on total starch. There was no evidence of difference in total starch between the diets that were pelleted at 175 and 185°F. The total starch was the lowest in the diet with 0% fines (54.11%) followed by the diet with 20% and 10% fines (56.42% and 57.90%), respectively (P = 0.013). For gelatinized starch and cooked starch, there was no interaction between the fines inclusion level and conditioning temperature. Both fines inclusion level and conditioning temperature did not affect gelatinized starch. For energy consumption, there was an interaction (P \u3c 0.0001) between fines inclusion level and conditioning temperature. When the diets were pelleted at 185°F conditioning temperature, the diet with 20% fines required significantly more energy during the pelleting process as compared to the diets with 0 and 10%. However, there was no significant difference in energy consumption for diets containing 0, 10, and 20% fines when the diets were pelleted at 175°F conditioning temperature. Therefore, increasing conditioning temperature increased pellet quality. When a diet contained less than 1.5% oil, recirculating fines through the conditioner and pellet die improved pellet quality. However, the 20% inclusion of fines led to occasional roll slips, decreased pellet mill stability, and increased energy usage when the diet was pelleted

Effect of Added Water, Holding Time, or Phytase Analysis Method on Phytase Stability and Pellet Quality

The addition of water to the mixer prior to pelleting is sometimes necessary to reach the target moisture content at the end of the conditioning process. However, there are limited data to demonstrate the impact of water addition in the mixer on phytase stability during the pelleting process. In addition, the variation of phytase analysis method may lead to incorrect or biased conclusions for research on industrial phytase stability. Therefore, the objective of this experiment was to determine the effect of water added in the mixer, feed holding time, and phytase analysis method on phytase stability and pellet quality. Treatments were arranged in a 2 × 2 × 2 factorial with main effects of added water (0% or 1%), holding time (0 or 2 h), and phytase analysis method (ELISA or EN ISO), respectively. For the 0% added water treatment, a 210-lb basal feed and 0.03-lb phytase were mixed for 5 min. For the 1% added water treatments, a 208-lb basal feed and 0.03-lb phytase were mixed for 120 s followed by the addi­tion of 2-lb water and then the mixture was mixed for 180 s wet mix time. The water was applied to dry feed in the mixer using a hand-held sprayer (Country Tuff model 26329, Sedalia, MO) with a flat spray tip nozzle (TeeJet model TP11006, Glendale Heights, IL). After the diets were mixed, treatments were immediately pelleted or held in a closed container for 2 h before pelleting. Treatments were steam conditioned at 185°F for approximately 30 s and pelleted using a pellet mill (California Pellet Mill Co. model Cl-5, Crawfordsville, IN). The pellet mill was equipped with a 0.16 × 0.87 in die. Samples were collected during discharge of the mixer, after conditioning and after pelleting. The conditioned mash and pelleted samples were cooled for 10 min using an experimental counterflow cooler. There were 3 replicates per treatment. Data were analyzed using the GLIMMIX procedure of SAS. The results demonstrated that there was no evidence of three-way or two-way interactions among added water, holding time, and analysis method on phytase stability for mash samples, conditioned mash samples, and pellets. The added water and holding time did not impact phytase stability for mash samples, conditioned mash samples, and pellets. The ELISA method had greater (P = 0.004) phytase activity than the EN ISO method for the pellet samples. The phytase activity was similar between the two analytical methods for mash samples and conditioned mash samples. For pellet quality, there was no evidence of interaction between added water and holding time. Added water and holding time did not impact pellet durability index. Therefore, the stability of phytase produced by a strain of Trichoderma reesei was not affected when feed was stored in a bin up to 2 h prior to pelleting. The added water in mash feed did not affect the degradation of Trichoderma reesei phytase when the feed moisture did not exceed 13%. Additionally, the ELISA or EN ISO method could be used in the laboratory to determine Trichoderma reesei phytase stability. Increasing moisture content of mash feed by 0.6% did not improve pellet quality

The Effect of Pellet Mill Production Rate and Knife Distance on Pellet Quality

Longer pellet lengths may lead to decreased pellet breakage, resulting in increased pellet durability index (PDI). Thus, the objective of this experiment was to determine the effects of production rate and knife distance on pellet length and subsequent pellet quality. Treatments were arranged in a 2 × 3 factorial with two production rates (16 and 33 lb/min) and three knife distances (0.25, 0.50, and 0.75 in). All diets were conditioned at 185°F and pelleted using a CPM pellet mill (Model 1012-2 HD, California Pellet Mill Co., Crawfordsville, IN) equipped with a 0.19 in × 1.25 in die. The production rate (PR) and knife distance (KD) were randomized to minimize the effects of pelleting and sampling order. There were 3 replicates per treatment. Samples were analyzed for pellet length, percentage fines, and PDI using the standard and modified tumble box method (STD and MOD, respectively) and Holmen NHP100 (TekPro Ltd, Norfolk, UK) with a 60-sec run time. Data were analyzed using the GLIMMIX procedure of SAS (v. 9.4, SAS Inst. Inc., Cary, NC). There was no evidence for an interaction between PR and KD for all analyzed variables (P \u3e 0.24). The 16 lb/min PR yielded a longer pellet (P ≤ 0.05) compared to the 33 lb/min PR. The PR had no effect on percentage fines (P \u3e 0.10); however, decreasing the PR tended to increase PDI regardless of analytical method (P ≤ 0.10). Increasing KD resulted in longer (P \u3c 0.01) pellets and decreased (P \u3c 0.01) percentage fines. Reducing KD to 0.25 in reduced PDI compared to 0.50 in and 0.75 in treatments, which yielded similar PDI. In conclusion, pellet quality can be improved by increasing the pellet length from 0.19 to 0.34 in (KD 0.25 and 0.75 in, respectively)

The Effects of Filter Type and Warm-Up Time on Pellet Durability Index Using the Holmen NHP100 Portable Pellet Tester

The Holmen NHP100 (TekPro Ltd, Norfolk, UK) is a portable forced air pellet tester commonly used by the feed industry to determine the pellet durability index (PDI). The objective of this study was to determine the effect of filter type and machine warm-up time on PDI. A corn-soybean meal-based grower diet was conditioned at 185°F for 30 sec and subsequently pelleted using a laboratory pellet mill (Model CL5 California Pellet Mill Co., Crawfordsville, IN) equipped with a 0.16- × 0.5-in die. Production rate was 120 lb/h. Once cool, pellets were analyzed for PDI using the NHP100 with a 60-sec run time. Air temperature and pressure within the NHP100 were recorded throughout the experiment. Treatments were arranged in a 3 × 8 factorial with varying filters (none, factory tissue filter, or commercial paper towel filter) and machine warm-up time (0, 3, 6, 9, 12, 15, 18, or 21 min). There were three replicates per treatment. Pellets were sifted before and after analysis for separation of fines and pellets using a U.S. #6 standard sieve. There was a filter × warm-up time interaction (P ≤ 0.05) for air temperature. The air temperature without warm-up time (0 min) was greater with the factory filter and paper towel compared to no filter. Air temperature remained similar regardless of filter type as the warm-up time increased from 6 to 21 min There was a filter × warm-up time interaction (P ≤ 0.05) for air pressure. At 0 min warm-up time, there were no differences in air pressure between none, factory and paper towel filters. At 3 to 21 min warm-up time, air pressure remained similar between factory and paper towel filters, while no filter was greater than the paper towel filter. There was a filter × warm-up time interaction (P ≤ 0.05) for PDI. For no filter, increasing warm-up time from 0 to 6 min increased PDI with no further increase from 6 to 21 min. However, there were no differences in PDI with increasing warm-up time when using the factory filter or paper towel. Using the factory filter or paper towel had similar PDI, but resulted in greater PDI compared to no filter. In conclusion, warm-up time did not influence air temperature, pressure, or PDI when using a filter. Therefore, it is suggested to use a filter when conducting PDI analysis using the Holmen NHP 100

The Effect of Screen Hole Diameter and Hammer Tip Speed on the Subsequent Particle Size of Ground Corn Analyzed With and Without Sieving Agent

Reducing the particle size of grains increases the ratio of surface area to volume which provides digestive enzymes greater access to nutrients, therefore improving utilization of the feed. Hammermills are a very cost-effective method of reducing grains to very fine particle sizes for feeding. A variety of settings can be changed on hammermills to achieve a target particle size. Thus, the objective of this experiment was to determine the effects of screen hole diameter, hammer tip speed, and the inclusion of a sieving agent on the particle size of corn. Treatments were arranged in a 4 × 6 × 2 factorial with screen hole diameter (10/64, 12/64, 16/64, 24/64 in.), hammer tip speed (20,500, 18,450, 16,400, 14,350, 12,300, and 10,250 ft/min), and particle size analytical method (with and without sieving agent). All treatments were ground using a Bliss Hammermill (Model 22115) equipped with a variable frequency drive (VFD) and a 25 HP motor. The screen hole diameter and hammer tip speed were randomized to reduce the effects of grinding and sampling order. There were 3 replicates per treatment. Samples were analyzed for geometric mean diameter (dgw) and standard deviation (Sgw) of the particle size. There was no evidence of a screen hole diameter × hammer tip speed × sieving agent interaction for all variables (P \u3e 0.327). There was a linear screen hole diameter × linear hammer tip speed interaction (P \u3c 0.001) for dgw. When increasing tip speed from 10,250 to 20,500 ft/min, the rate of decrease in dgw was greater as screen hole diameter increased from 10/64 to 24/64. There was a quadratic screen hole diameter × linear hammer tip speed interaction (P \u3c 0.035) for Sgw. When increasing the screen size from 10/64 to 24/64, the rate of increase in Sgw was greater as tip speed increased from 10,250 to 16,400 ft/min and was similar from 16,400 to 20,500 ft/min. There was no evidence of a screen hole diameter × hammer tip speed interaction for percent fines (P \u3e 0.153). There was no evidence of a screen hole diameter × sieving agent or hammer tip speed × sieving agent interaction for dgw or Sgw (P \u3e 0.540). There was a linear screen hole diameter × sieving agent interaction (P \u3c 0.001) for percent fines. When increasing the screen size from 10/64 to 24/64, the rate of decrease in percent of fine particles was greater when sieving agent was used compared to when it wasn’t used. The results of this trial indicate that the particle size range for a specified hammermill screen size can be altered by adjusting the hammer tip speed with a VFD. Additionally, particle size should be determined with the addition of sieving agent during analysis to more accurately characterize the particle size distribution, especially of finer particles that may influence flowability or animal intake

The Effects of Cold Pelleting and Separation of Fine Corn Particles on Growth Performance and Economic Return in Nursery Pigs

A total of 320 pigs (DNA 241 × 600; initially 22.5 lb BW) were used in a 21-d experiment to determine the effects on pelleting technique and removing fine corn particles (\u3c 150 microns) on nursery pig growth performance. There were 5 pigs per pen and 8 pens per treatment and diets were all manufactured using corn ground to 400 microns. Diets were fed as a mash or pelleted using a traditional vertical die pellet mill equipped with a steam conditioner (steam pellet) or a horizontal pellet die with hot water conditioning prior to pelleting (cold pellet). Therefore, the 8 treatments were: 1) ground corn diet fed as mash, 2) ground corn diet steam pelleted, 3) ground corn diet cold pelleted, 4) ground corn with fines less than 150 microns removed from the diet and the diet fed as mash, 5) ground corn with fines less than 150 microns removed from the diet and the diet without fines was steam pelleted, 6) ground corn with fines less than 150 microns removed from the diet and the diet without fines was cold pelleted, 7) fines less than 150 microns were steam pelleted then proportionally added back to ground corn and fed as a mixture of pellets and mash, and 8) fines less than 150 microns were cold pelleted then proportionally added back to ground corn and fed as a mixture of pellets and mash. Removal of fines less than 150 microns from the corn improved the flowability characteristics of the diets as indicated by improved composite flow index values. The best flowability was achieved when fines were pelleted and added back to the mash diets. Pigs fed steam- or cold-pelleted diets had decreased (P \u3c 0.02) ADG, ADFI, and d-21 BW, total feed cost, revenue, and income over feed cost (IOFC) compared to those fed mash diets. Pigs fed steam pelleted diets had decreased (P \u3c 0.006) ADG, d-21 BW, revenue, and IOFC compared to those fed cold pelleted diets. There were no growth performance differences between pigs fed ground corn diets or ground corn diets with fines removed. Pigs fed diets with fines removed, pelleted, and subsequently added back had increased (P \u3c 0.05) ADFI, F/G, and feed cost compared to all other treatments. It is assumed that this response resulted from increased feed wastage resulting from pigs sorting pellets mixed with mash diets. The results of this study indicate that removing particles less than 150 microns improved the flowability of a mash diet without sacrificing growth performance. Additionally, cold pelleting was a viable option to steam pelleting in the current experiment. However, pelleting diets reduced pig performance compared to pigs fed mash diets. Further research is needed to validate the response to cold pelleting when the expected response to pelleting using steam conditioning is achieved

The Effect of Hammermill Screen Hole Diameter and Hammer Tip Speed on Particle Size and Flowability of Ground Corn

A variable frequency drive can be installed on the motor of a hammermill to adjust motor speed and ultimately hammer tip speed. This enables particle size adjustments to be made externally without requiring screens to be changed, therefore reducing idle time. The objective of this study was to determine the effect of screen hole diameter and tip speed on geometric mean diameter (dgw), geometric standard deviation (Sgw), and angle of repose (AoR). Treatments were arranged as a 3 × 3 factorial in a completely randomized design using three screen hole diameters and three hammer tip speeds. Each treatment replicate (n = 3) was manufactured as a separate grinding queue with individual queue samples as the experimental unit. Whole corn was ground using three common screen hole diameter (6/64, 10/64, and 16/64 in.) at varying hammer tip speeds (10,250, 15,375, and 20,500 ft/min). Results indicated a marginally significant linear interaction (P \u3c 0.077) between screen hole diameter and tip speed for dgw, and Sgw. For dgw, when tip speed increased from 10,250 to 20,500 ft/min the rate of decrease in dgw was greater as screen hole diameter increased from 6/64 to 16/64 in. Therefore, when tip speed was increased from 10,250 to 20,500 ft/min, dgw was reduced by 233, 258, and 305 μm for corn ground using the 6/64, 10/64, and 16/64 in. screen hole diameter, respectively. For Sgw, when tip speed increased from 10,250 to 20,500 ft/min the rate of decrease in Sgw was smaller as screen hole diameter increased. Therefore, when tip speed increased from 10,250 to 20,500 ft/min, Sgw was reduced by 0.31, 0.24, and 0.13 for corn ground using the 6/64, 10/64, and 16/64 in. screen hole diameter, respectively. There was no observed interaction between screen hole diameter and tip speed on AoR. Increasing hammer tip speed increased (linear, P \u3c 0.001) AoR. Increasing screen hole diameter decreased (linear, P \u3c 0.001) AoR. In summary, the particle size range for a specified hammermill screen size can be adjusted through manipulation of the hammer tip speed, which is made possible using motor variable frequency drives. This enables operators to quickly change the particle size output, while reducing idle time in the mill