Evaluation of Conditioning Temperature and Die Specifications on Evaluation of Conditioning Temperature and Die Specifications on Nursery Pig Performance Nursery Pig Performance

Summary The objective of this study was to determine the effects on growth performance in nursery pigs that is linked to the conditioning temperature and die specifications used during the feed pelleting process. A total of 315 barrows (DNA; 200 × 400; initial BW 13.2 lb) were used in a 35-d growth trial. Upon arrival, pigs were weighed and assigned to pens in a completely randomized design with 5 pigs per pen, and each pen was randomly assigned to 1 of 7 dietary treatments with 9 replications per treatment. Treatments consisted of a mash control (MC) and 6 pelleted diets manufactured using 2 different pellet dies (length/diameter [L:D]: 6.7 and 2.7) and 3 different conditioning temperatures (low, medium, high). Conditioning temperatures for Phase 1 diets pelleted using the 6.7 L:D die were 80, 100, and 120°F and for the die with a L:D 2.7 were 100, 120, and 140°F for the low, medium, and high, respectively. Phase 2 conditioning temperatures for diets pelleted using the die with a L:D of 6.7 were approximately 120, 140, and 160°F and for the 2.7 L:D die were 140, 160, and 180°F for the low, medium, and high, respectively. Diets were fed in three phases as follows, Phase 1: d 0 to 10, Phase 2: d 10 to 25, and Phase 3: d 25 to 35. During Phase 3 all pigs were fed a common mash diet. Overall from d 0 to 35, similar ADG was observed for pigs fed the MC or pelleted diets with the exception of the diet pelleted at the low conditioning temperature using the 6.7 L:D die, which had


Introduction
Pelleting of swine feed is a common industry practice as it typically improves growth performance and feed handling throughout production. During the pelleting process mash feed is exposed to moisture and heat via steam in the conditioner before it is pushed through the die to form pellets. Multiple variables during this process can be changed to influence pellet mill throughput and pellet quality. Conditioning temperature, the amount of time feed is retained in the conditioner and exposed to steam (retention time), and die selection are some factors that can be manipulated during the pelleting process. The die length to diameter (L:D) ratio plays a key role in the quality of pellets produced. A larger L:D ratio indicates a thicker die, allowing for more compression, which correlates with improved pellet quality. In addition to pelleting parameters, individual ingredient specifications can also vary greatly and influence the pelleting process.
It has been widely reported that pelleted feed can improve the feed efficiency of nursery pigs when compared to mash. Nursery pig diets also contain specialty ingredients, such as dried whey, that reduce flowability of the diets. These diets are pelleted to negate the flowability concerns. A variety of factors, such as pellet mill model, die specification, and diet composition can influence the conditioning temperature at which nursery pig diets are pelleted. Traditionally, nursery pig diets are pelleted at lower conditioning temperatures, ranging from approximately 140°F to 160°F, because of the increased levels of specialty proteins included in the diet. Whey products specifically require a lower conditioning temperature as milk-based products tend to absorb more moisture at higher temperatures, which creates a sticky consistency and risks plugging the equipment. Therefore, the objective of this study was to determine the effects of conditioning temperature and die specifications used when pelleting diets on the growth performance of nursery pigs.

Procedures
A total of 315 barrows (DNA 200 × 400; initial BW of 13.2 lb) were used in a 35-d growth trial at the Kansas State University Segregated Early Weaning (SEW) facility. Pigs were housed in 4-× 4-ft pens containing a three-hole dry self-feeder and one cup waterer to provide ad libitum access to feed and water. Pigs were weaned at approximately 21 d of age. Upon arrival, pigs were weighed and assigned to pens in a completely randomized design with 5 pigs per pen, and each pen was assigned to 1 of 7 treatments. There were 9 replications per treatment.
Dietary treatments consisted of a basal diet fed as a mash control (MC) or 6 diets pelleted with different pelleting parameters. The mash control diet was mixed at Hubbard Feeds (Beloit, KS) and transferred to Kansas State University, Manhattan, KS, and pelleted using the CL-5 experimental pellet mill (Model CL-5 California Pellet

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Mill Co., Crawfordsville, IN). Diets were steam conditioned (5 in diameter × 36 in length) to 3 target conditioning temperatures for approximately 30 s and pelleted using 1 of 2 pellet dies. Both pellet dies had holes that were 3/16 inches in diameter and two different die thicknesses, to create length:diameter (L:D), of 2.7 and 6.7. Phase 1 feed was conditioned to approximately 80 (Low), 100 (Medium), and 120°F (High) using the 6.7 L:D die and 100 (Low), 120 (Medium), and 140°F (High) using 2.7 L:D die. The feeder was set at a constant rate to achieve approximately 120 lb per hour. Phase 2 feed was conditioned to approximately 120 (Low), 140 (Medium), and 160°F (High) using the 6.7 L:D die and 140 (Low), 160 (Medium), and 180°F (High) using the 2.7 L:D die. The feeder was set at a constant rate to achieve approximately 240 lb per hour for Phase 2. Pellets were then cooled in an experimental cooler for 15 minutes. After pelleting, pellets were sifted to remove fines to mitigate effects of pellet quality on pig performance. Pellet samples were taken at the die as well as after cooling and analyzed for pellet quality using a Holmen NHP100 (TekPro Ltd, Norfolk, UK) for 60 seconds. The basal diet formulation was a standard nursery diet that was formulated to meet or exceed the recommended nutrient requirement estimates for nursery pigs. 2 Diets were fed in three phases (Phase 1: d 0 to 10; Phase 2: d 10 to 25; Phase 3: d 25 to 35).
Pens of pigs were weighed, and feed disappearance calculated on d 0, 10, 17, 25, and 35 of the experiment to determine average daily gain (ADG), average daily feed intake (ADFI), and feed/gain ratio (F/G). Feed additions were recorded for each individual pen. Feed samples were taken from the feeders and appropriately stored until proximate analysis was performed (Ward Laboratories, Kearney, NE). Total and available lysine analysis was performed using official analytical methods at the Agricultural Experiment Station Chemical Laboratories at the University of Missouri.
Data were analyzed using the PROC-GLIMMIX procedure of SAS (SAS Institute, Inc., Cary, NC) with pen serving as the experimental unit. Analysis was performed using Dunnett's multiple comparison test to compare each pelleted diet to the MC. Contrasts were used to separate treatment means with comparison of die (6.7 vs. 2.7), and linear and quadratic polynomials were used to test increasing conditioning temperature within each die. Results were considered significant at P ≤ 0.05, and marginally significant at P ≤ 0.10.

Results and Discussion
All treatment diets were analyzed for crude protein, fiber, fat, phytase content, as well as total and available lysine. Phase 1 diets pelleted using the 6.7 L:D die had an approximately 10% decrease in available lysine as conditioning temperature increased. Diets pelleted using the 2.7 L:D die had an even larger 25% decrease in the available lysine of Phase 1 diets as conditioning temperature increased. A similar trend was seen in Phase 2 diets pelleted using the 2.7 L:D die, where available lysine decreased by 15% as conditioning temperature increased. However, Phase 2 diets pelleted with the 6.7 L:D die had similar available lysine at all of the conditioning temperatures evaluated in this experiment. The increasingly harsh conditions with increased conditioning temperature and frictional heat across the die may have caused the reduction in available lysine.

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Conditioning and hot pellet temperatures were recorded periodically throughout each pelleting run and the difference (Δ T) was calculated. Conditioning temperatures averaged within 5°F of the target and the Δ T decreased as conditioning temperature increased. This is an expected result as frictional heat will decrease when conditioning temperature increases, as steam provides moisture and therefore lubrication while feed passes through the die. All pelleted diets were evaluated for pellet quality using a Holmen 100 for 60 seconds. There was approximately a 10% decrease in pellet durability index (PDI) of the Phase 1 diet when pelleted with the 2.7 L:D die compared the 6.7 L:D die, but no large differences in PDI were observed when comparing conditioning temperatures. However, the Phase 2 diet pelleted at the low or medium conditioning temperature on the 2.7 L:D die was analyzed to have a PDI value approximately 30% poorer than all other pelleted treatments.
From d 0 to 10 there were no differences in ADG, ADFI, or F/G for each pelleted treatment compared to the mash control diet. When diets were pelleted using the 6.7 L:D die, pigs fed diets conditioned at the medium temperature (100°F) tended to have increased (quadratic, P = 0.077) ADFI compared to the low and high temperatures. There was no difference in d 10 BW for any treatment.
From d 10 to 25, pigs fed the MC had increased (P < 0.05) ADG compared to those fed the diets pelleted using the low and medium conditioning temperatures on the 6.7 L:D die. Pigs fed all other pelleted diets had ADG similar to those fed the MC. When pelleting using the 6.7 L:D die, there was a tendency for a linear increase (P = 0.098) in ADG in pigs fed diets pelleted with increasing conditioning temperature. Pigs fed the MC or the diet pelleted at the medium conditioning temperature on the 2.7 L:D die had similar ADFI as those fed the MC, while pigs fed all other pelleted diets had decreased (P = 0.001) ADFI during this phase. Furthermore, pigs fed diets pelleted on the 6.7 L:D die had decreased (P = 0.026) ADFI compared to the 2.7 L:D die. There were no differences in F/G or d 25 BW during this period.
From d 25 to 35 all treatments were fed a common mash diet. There were no differences in ADG, ADFI, or F/G between pigs previously fed the MC and each pelleted diet. However, there was a tendency for increased (P = 0.083) ADG in pigs previously fed diets pelleted on the 2.7 L:D die compared to the 6.7 L:D die. Pigs fed diets pelleted using the die with a L:D of 2.7 also had increased (P = 0.039) ADFI compared to pigs fed diets manufactured with the L:D 6.7 die.
From d 0 to 25 there was no difference observed in ADG when comparing each pelleted treatment to the MC. Pigs fed diets pelleted on the 6.7 L:D die at any of the conditioning temperatures, and diets pelleted using the 2.7 L:D at the low and high conditioning temperatures had decreased (P < 0.05) ADFI during this phase, compared to those fed the MC and the medium conditioning temperature on the 2.7 L:D die. Pigs fed all pelleted diets manufactured on the 6.7 L:D die as well as the medium conditioning temperature on the 2.7 L:D die showed improved (P < 0.05) F/G compared to the MC and diets pelleted on the 2.7 L:D die at the low and high conditioning temperatures. There were no differences between pigs fed diets pelleted using the different dies.

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Overall from d 0 to 35, pigs fed the MC had increased (P < 0.05) ADG compared to diet manufactured using the 6.7 L:D die at the low conditioning temperature with all other pelleted treatments performing similarly to the MC. When pelleting diets using the 2.7 L:D die, there was a tendency for increased (quadratic, P = 0.077) ADG in pigs fed diets conditioned at increasing temperatures, with the medium temperature having the greatest ADG. There was a tendency for increased (P = 0.088) ADG in pigs fed diets pelleted using the 2.7 L:D die compared to the 6.7 L:D die. Pigs fed diets pelleted on the 6.7 L:D die and diets pelleted using the 2.7 L:D at the low and high conditioning temperatures had decreased (P < 0.05) ADFI during this phase compared to the MC. Pigs fed pelleted diets using the 6.7 L:D die at any conditioning temperature or the 2.7 L:D die at the medium conditioning temperature had improved (P < 0.05) F/G compared to the MC diet. Additionally, pigs fed diets manufactured using the 6.7 L:D die had decreased (P = 0.030) ADFI compared to those fed diets pelleted using the 2.7 L:D die. There was a tendency for increased (P = 0.088) d 35 BW in pigs fed diets pelleted using the 2.7 L:D die compared to the 6.7 L:D die.
In the experiment reported herein, numerical decreases in available lysine were observed as conditioning temperature increased on both the 6.7 and 2.7 L:D dies. In addition, there was a decrease in pellet quality when treatments were manufactured on the 2.7 L:D die; however, pellet quality improved as conditioning temperature increased. These differences did not result in a growth performance response due to conditioning temperature or die. Furthermore, pigs fed pelleted diets had poorer ADG but decreased ADFI and improved F/G compared to those fed the MC. Overall, increasing the conditioning temperature decreased the available lysine, and pigs fed pelleted diets had poorer ADG but decreased ADFI and improved F/G compared to those fed the MC.

Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned.
Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.     All diets were mixed at Hubbard Feeds (Beloit, KS) and transported to Kansas State University for further processing. 2 Diets pelleted at K-State were manufactured on two pellet dies with a pellet diameter of 3/16 in with an L:D ratio of either 6.7 or 2.7 and sifted to control for differences in pellet quality. 3 Conditioning temperatures for Phase 1 on the 6.7 L:D die were approximately 80, 100, and 120°F and 100, 120, and 140°F for the 2.7 L:D die for the low, med, and high respectively. Phase 2 conditioning temperatures for the 6.7 L:D die were approximately 120, 140, and 160°F and for the 2.7 L:D die were 140, 160, and 180°F for the low, medium, and high respectively. 4 MC = Mash control. 5 Δ T = Hot pellet temperature -conditioning temperature. 6 Pellet durability analysis was performed using a Holmen 100 for 60 s for all pelleted samples.