Effects of dietary byproduct feeding withdrawal prior to market on finishing pig growth performance, carcass characteristics, carcass fat quality, intestinal weights, and economics

A total of 288 pigs (PIC 327 Ã— 1050; initially 84.7 lb) were used in an 88-d study to determine the timing of high-fiber ingredient removal from the diet prior to marketing to optimize growth performance, carcass characteristics (primarily yield), carcass fatty acid composition, and economics. Two diet types, a cornsoybean meal control diet with low NDF (9.3%) and a high-fiber, high-NDF (19%) diet that contained 30% dried distillers grains with solubles (DDGS) and 19% wheat middlings (midds) were used throughout the study. Pens of pigs were randomly allotted to 1 of 6 dietary feeding strategies with 8 pigs per pen (4 barrows and 4 gilts) and 6 replications per treatment. The 6 feeding strategies consisted of the corn-soy control diet or high-fiber diet fed for the duration of the study, or the high-fiber diet fed until 20, 15, 10, or 5 d prior to slaughter after which the pigs were switched to the corn-soybean meal control diet. Overall (d 0 to 88), ADG was not affected by diet type or withdrawal strategy. Pigs fed the high-fiber diet continuously tended (P < 0.07) to have increased ADFI compared with pigs fed the control diet. This led to an increase (P < 0.01) in F/G for pigs fed the high-fiber diet for the entire study compared to pigs fed the control diet. The caloric efficiency of live weight gain of pigs fed the high-fiber diet continuously was worse (P < 0.03) compared with pigs fed the control diet throughout. Withdrawing the highfiber diet and switching to the control diet did not influence growth performance. For carcass characteristics, percentage yield and backfat were reduced (P < 0.01), whereas loin depth and jowl iodine value (IV) increased (P < 0.01) in pigs fed the highfiber diet continuously compared with those fed the corn-soybean meal control diet. As days of withdrawal from the high-fiber diet increased, percentage yield improved (linear; P < 0.01), whereas jowl IV decreased (linear; P < 0.01) and backfat increased (quadratic; P < 0.04). These data suggest that 15to 20-d of removal from high-fiber diets prior to slaughter was optimal in terms of percentage carcass yield. The full pluck from pigs fed the high-fiber diet continuously tended to weigh more (P < 0.10) than from those fed the control diet. In addition, pigs continuously fed the high-fiber diet had heavier (P < 0.01) whole intestines, specifically full large intestines, than pigs fed the control. For pigs fed the high-fiber diet then switched to the corn-soy control, whole intestine weight tended to decrease (linear; P < 0.06) and full large intestine weight decreased (linear; P < 0.02) as withdrawal time increased. In summary, pigs fed the high-fiber diet had increased F/G, poorer caloric efficiency, and lower carcass yield compared with pigs fed the corn-soy control. Withdrawing pigs from the high-fiber diet and switching them to a corn-soy control diet did restore carcass yield when done for the last 15 to 20 d prior to harvest.; Swine Day, Manhattan, KS, November 21, 2013


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Effects of Dietary Byproduct Feeding Withdrawal Prior to Market on Finishing Pig Growth Performance, Carcass Characteristics, Carcass Fat Quality, Intestinal Weights, and Economics1,2 K.F.Coble, J.M. DeRouchey, M.D. Tokach, R.D. Goodband, S.S. Dritz3 , T.A. Houser, B.L. Goehring, and M.J. Azain4 Summary A total of 288 pigs (PIC 327 × 1050; initially 84.7 lb) were used in an 88-d study to determine the timing of high-fiber ingredient removal from the diet prior to marketing to optimize growth performance, carcass characteristics (primarily yield), carcass fatty acid composition, and economics.Two diet types, a corn-soybean meal control diet with low NDF (9.3%) and a high-fiber, high-NDF (19%) diet that contained 30% dried distillers grains with solubles (DDGS) and 19% wheat middlings (midds) were used throughout the study.Pens of pigs were randomly allotted to 1 of 6 dietary feeding strategies with 8 pigs per pen (4 barrows and 4 gilts) and 6 replications per treatment.The 6 feeding strategies consisted of the corn-soy control diet or high-fiber diet fed for the duration of the study, or the high-fiber diet fed until 20, 15, 10, or 5 d prior to slaughter after which the pigs were switched to the corn-soybean meal control diet.
Overall (d 0 to 88), ADG was not affected by diet type or withdrawal strategy.Pigs fed the high-fiber diet continuously tended (P < 0.07) to have increased ADFI compared with pigs fed the control diet.This led to an increase (P < 0.01) in F/G for pigs fed the high-fiber diet for the entire study compared to pigs fed the control diet.The caloric efficiency of live weight gain of pigs fed the high-fiber diet continuously was worse (P < 0.03) compared with pigs fed the control diet throughout.Withdrawing the highfiber diet and switching to the control diet did not influence growth performance.
For carcass characteristics, percentage yield and backfat were reduced (P < 0.01), whereas loin depth and jowl iodine value (IV) increased (P < 0.01) in pigs fed the highfiber diet continuously compared with those fed the corn-soybean meal control diet.As days of withdrawal from the high-fiber diet increased, percentage yield improved (linear; P < 0.01), whereas jowl IV decreased (linear; P < 0.01) and backfat increased (quadratic; P < 0.04).These data suggest that 15-to 20-d of removal from high-fiber diets prior to slaughter was optimal in terms of percentage carcass yield.

Introduction
Including feed ingredient sources that are higher in fiber and lower in energy to partially replace a portion of the corn and soybean meal in diets has become a common practice.Reduced carcass yield is one negative effect of including high-fiber ingredients such as DDGS or wheat middlings.Research has reported (Asmus et al., 2011 5 ) that changing pigs from a high-NDF diet (19% NDF; 30% DDGS and 19% wheat middlings) to a corn-soybean meal diet (9.3% NDF) approximately 20 d prior to marketing fully restored carcass yield; furthermore, switching from a high-to low-NDF diet prior to market could reduce gut fill and intestinal weights.Although packers do not pay producers on a yield basis, feeding high-fiber diets does influence HCW, thus affecting producer revenue.More data are needed to determine the optimum time to switch finishing pigs from the high-to low-NDF diet to fully recover carcass yield loss associated with higher fiber diets.
Therefore, the objective of this study was to determine the timing of high-fiber ingredient removals prior to marketing to optimize growth performance, carcass characteristics (primarily yield), carcass fat quality, intestinal weights, and economics.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in this experiment.The study was conducted at the Kansas State University Swine Teaching and Research Center in Manhattan, KS.The barn was tunnel-ventilated with completely slatted flooring and deep pits.Each pen was equipped with a 2-hole stainless steel feeder and bowl waterer for ad libitum access to feed and water.Feed was delivered to each individual pen by a robotic feeding system (FeedPro; Feedlogic Corp., Wilmar, MN).
A total of 288 pigs (PIC 327 × 1050; initially 84.7 lb) were used in an 88-d study.Pens of pigs were randomly allotted to 1 of 6 dietary feeding strategies with 8 pigs per pen (4 barrows and 4 gilts) and 6 replications per treatment.The 6 dietary strategies consisted of a corn-soy control diet (NDF = 9%) or high-fiber diet (NDF = 19%; 30% DDGS and 19% wheat middlings) fed for the duration of the study, or the high-fiber diet fed until 20, 15, 10, or 5 d prior to slaughter after which pigs were fed the corn-soy SWINE DAY 2013 control diet.All diets were formulated on a standardized ileal digestible (SID) lysine basis and fed in 4 dietary phases (Tables 1 and 2).All diets were fed in meal form.
Composite samples of the DDGS and wheat middlings used in the diets were collected at the time of manufacturing and analyzed for DM, CP, fat, crude fiber, NDF, ADF, and ash (Table 3).Samples of the complete feed were obtained from each delivery for each diet type to measure bulk density (Table 4).In addition, samples of the DDGS, wheat middlings, and complete diets were analyzed for fatty acid concentrations (Table 5).
Pens of pigs and feeders were weighed approximately every 3 wk to calculate ADG, ADFI, and F/G.When the pigs reached approximately 227 lb, pigs fed the high-fiber diet were realloted to withdrawal strategy, balancing by the d 0 and d 68 average pen weights.This was done to ensure that any measured criteria were not influenced by prior performance when the pigs were all fed the same diet.During the last 20 d of the experiment, all pens of pigs and feeders were weighed each time a treatment group switched diets, which was 20, 15, 10, and 5 d prior to slaughter.Prior to harvest, pigs were individually tattooed for identification purposes in the plant.On the final day of the study, pens of pigs and feeders were weighed and each pig was weighed individually to allow carcass yield to be calculated.The second-heaviest gilt in each pen (1 pig per pen, 6 pigs per treatment) was identified and transported to the K-State Meat Laboratory, and all other pigs were transported to Triumph Foods LLC (St.Joseph, MO) for processing and data collection.Carcass measurements taken at the commercial plant included HCW, backfat, loin depth, and percentage lean.Jowl fat samples were collected and analyzed by near-infrared spectroscopy (NIR) at the plant for IV.Percentage yield was calculated by dividing HCW at the plant by live weight at the farm and multiplying by 100.
Gilts selected for harvest at K-State were blocked by treatment and randomly assigned to a slaughter order to equalize withdrawal time before slaughter.Immediately after evisceration, the entire pluck was weighed and individual organs (stomach, cecum, large intestine, small intestine, heart, liver, lungs, kidneys, spleen, and reproductive tract) were separated and weighed.The weights of the stomach, cecum, and large intestine were weighed full of intestinal contents, and weighed again after they were flushed with water and stripped of contents to determine an empty weight.During the harvest process, carcasses were split into two halves.At the end of the harvesting process, each pair of sides were moved onto a scale to record HCW and railed into a cooler for storage and further carcass measurements.
Carcass quality measurements were taken 24 h after slaughter on the right side of the carcass, which was ribbed at the 10th rib.Marbling and color scores were determined for the loin by using the Pork Quality Standards according to the American Meat Science Association (AMSA) and the National Pork Producers Council (NPPC).Ultimate pH of the loin was determined with a portable Hazard Analysis Critical Control Point (HACCP)-compliant pH meter designed for meat (model HI 99163;  Hanna Instruments, Smithfield, RI).Fat samples from the jowl, belly, backfat, and ham collar were collected and analyzed for fatty acid.Jowl samples were taken from the lowest portion of the jowl when the carcass was hanging.Belly samples were taken from behind the 2nd teat on the teat line.Samples of the backfat were taken at the 10th rib

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on the outer edge of the loin.Lastly, ham collar samples were collected from the middle portion of the ham collar.All 3 layers of fat were used in the analysis.
Measurements of belly quality were also collected from bellies cut from the left side of each carcass.The weight, length, width, and height were recorded for each belly.A belly flop test was also performed on each belly to determine firmness.To measure belly flop, bellies were centered upon a fulcrum point and allowed to hang for 1 min, at which point the distance between the two ends were measured.This was completed with both the skin side up and skin side down.
At the conclusion of the study, an economic analysis was completed to determine the impact of withdrawing pigs from a high-fiber diet to the control diet prior to harvest.The total feed cost per pig was calculated by multiplying the ADFI by the feed cost per pound and the number of days in each respective period, then taking the sum of those values for each period.Cost per pound of gain was calculated by dividing the total feed cost per pig by the total pounds gained overall.Carcass gain value was calculated by multiplying the HCW by an assumed carcass value of $77.00/cwt and then subtracting initial pig cost, which was determined by multiplying the initial weight by 75% and the assumed carcass value of $77.00/cwt.To calculate income over feed cost (IOFC), total feed cost was subtracted from the value of the carcass gain.
Data were analyzed utilizing the MIXED procedure of SAS (SAS Institute, Inc., Cary, NC) with pen serving as the experimental unit.Linear and quadratic contrasts were completed to determine the effects of withdrawing the high-fiber diet prior to slaughter, as well as a contrast between the corn-soy control and high-fiber diet fed throughout the entire study.Hot carcass weight served as a covariate for the analysis of loin depth, backfat, and percentage lean.Data are presented as least square means, and results were considered significant at P ≤ 0.05 and tendencies between P > 0.05 and P ≤ 0.10.

Results and Discussion
Chemical analysis of the DDGS and wheat middlings were similar to the nutrient values used for diet formulation (Table 3).As DDGS and wheat middlings were included in the diet, diet bulk density was reduced (Table 4).Fatty acid analysis of the wheat middlings, DDGS, and complete diets showed that the iodine value product (IVP) was lower in wheat middlings compared with DDGS (34.72 vs. 51.97).Also, because of the lower fat content, the corn-soy control diets had much lower IVP (15.7 to 21.3) than the high-fiber diet (20.6 to 43.9).
For growth performance from d 0 to 63, pigs fed the high-fiber diet for the entire study tended to have decreased (P < 0.07) ADG and worse (P < 0.01) F/G than pigs fed the corn-soybean meal control (Table 6).
From day d 63 to 88, pigs fed the high-fiber diet throughout tended to have greater (P < 0.06) ADG and ADFI (P < 0.01) compared with pigs fed the corn-soybean meal control diet.This resulted in no difference in F/G between the two treatments.For pigs withdrawn from the high-fiber diet and switched to the corn-soy control, there were no differences in ADG or F/G; however, ADFI increased then decreased (quadratic; P < 0.05) as days of fiber withdrawal prior to slaughter increased.

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Overall (d 0 to 88), ADG was not affected by diet type or withdrawal strategy.Pigs fed the high-fiber diet continuously tended (P < 0.07) to have increased ADFI compared with pigs fed the control diet.This led to poorer (P < 0.01) F/G for pigs fed the highfiber diet throughout compared with pigs fed the control diet.The caloric efficiency of pigs fed the high-fiber diet was worse (P < 0.03) compared with pigs fed the control diet, which suggests the energy content of the high-fiber diet was overestimated.Timing of the withdrawal of high-fiber ingredients prior to slaughter did not influence overall growth performance.
For carcass characteristics, percentage yield and backfat were reduced (P < 0.01), whereas percentage lean and jowl IV increased (P < 0.01) in pigs fed the high-fiber diet continuously compared with those fed the corn-soybean meal control diet (Table 7).As days withdrawn from the high-fiber diet increased, percentage yield improved (linear; P < 0.01; quadratic, P < 0.03), whereas jowl IV decreased (linear; P < 0.01) and backfat increased (quadratic; P < 0.04).These data suggest that 15 to 20 d of feeding a cornsoybean meal based diet prior to slaughter was optimal to recover percentage carcass yield when pigs were previously fed a high-fiber diet.
Pigs fed the high-fiber throughout tended (P < 0.06) to have increased belly width compared with those fed the control diet.In addition, belly firmness decreased (P < 0.01) when bellies were measured skin-up and skin-down for pigs fed the highfiber diet continuously compared with pigs fed the control diet.Belly characteristics and firmness were not affected by withdrawal time.
Feed cost per pig, feed cost per pound of gain, and carcass gain value per pig all decreased (P < 0.01) in pigs fed the high-fiber diet throughout the study compared with those fed the control diet, but IOFC did not differ.Feed cost per pound of gain tended to respond in a quadratic (P < 0.09) manner as withdrawal time decreased, with the lowest feed cost per pound of gain for no withdrawal or 20 d of withdrawal.As a result of the improved carcass yield, IOFC tended to increase (linear; P < 0.08) as withdrawal time increased from 0 to 20 d.Pigs fed the high-fiber diet until 20 d prior to harvest had the highest IOFC at $27.76 per pig, or $1.64 over that of pigs fed the control.
Intestinal weights were analyzed on both a weight (Table 8) and percentage of BW (Table 9) basis.On a weight basis, the full pluck from pigs fed the high-fiber diet continuously tended to weigh more (P < 0.10) than plucks from pigs fed the control diet.Pigs fed the high-fiber diet continuously also had heavier (P < 0.04) whole intestines and full large intestines (P < 0.01) than pigs fed the control diet.This result suggests that more intestinal contents remained in the large intestine of the pigs fed the high-fiber diet than in the control-fed pigs.For pigs fed the high-fiber diet then switched to the control, whole-intestine weight tended to decrease (linear; P < 0.06) and full large intestine weight decreased (linear; P < 0.02) as withdrawal time increased.With the exception of the lungs, which unexpectedly tended to increase (linear; P < 0.08) as withdrawal time increased, the rinsed weights of the organs did not differ in the various diet types or withdrawal strategies.
When expressed as a percentage of BW, the whole intestine tended (P < 0.06) to be a greater percentage of BW in pigs fed the high-fiber diet continuously compared with SWINE DAY 2013 pigs fed the control diet.As the number of days pigs were withdrawn from the highfiber diet increased, however, whole intestine as a percentage of BW decreased (linear; P < 0.05).The spleen occupied a lower (P < 0.04) percentage of BW in pigs fed the high-fiber throughout compared with the control.Similarly, the full large intestines of pigs fed the high-fiber diet also contributed a higher (P < 0.01) percentage of BW.The same effect existed for the full large intestine and spleen, because it contributed a lower (linear; P < 0.05) percentage of BW as days withdrawn from the high-fiber diet increased.The tendency for a quadratic response (P < 0.06) in full intestine weight when expressed as a percentage of BW indicates that much of the change in full intestine weight occurred in the first 5 d of withdrawal.Again, the lungs tended to increase (linear; P < 0.09) in weight as a percentage of BW as high-fiber diet withdrawal time increased.
Fatty acid analysis completed on the jowl, belly, backfat, and ham collar fat are reported in Tables 10, 11, 12, and 13, respectively.For pigs fed the high-fiber diet compared with the control diet, the concentration of PUFA was higher (P < 0.01) in jowl fat, partially because of the increase (P < 0.01) in linoleic (C18:2n-6) and α-linoleic (C18:3n-3) acid.Total trans fatty acids also increased (P < 0.01) in pigs fed the high-fiber diet throughout compared with pigs fed the corn-soy control.The PUFA:SFA ratio and IV also were higher (P < 0.01) in the jowl fat of pigs fed the high-fiber diet compared with the corn-soy control.
Fat from the belly of pigs fed the high-fiber diet had a lower (P < 0.01) percentage of MUFA and higher (P < 0.01) percentage of PUFA compared with those fed the cornsoy diet.This was mainly due to the shift from lower (P < 0.01) amounts of oleic acid (C18:1 cis-9) and higher amounts of linoleic and α-linoleic acid in the belly fat of pigs fed the control diet compared with the high-fiber diet.The PUFA:SFA ratio and IV also were higher (P < 0.01) in the belly fat of pigs fed the high-fiber diet for the entire study.
Similar differences existed in the backfat and ham collar fat of pigs fed the high-fiber diet compared with the corn-soy control.The total concentration of PUFA, concentration of total trans fatty acids, PUFA:SFA ratio, and IV increased (P < 0.01) when pigs were fed the high-fiber diet compared with the corn-soybean meal control.In addition to those differences, the concentrations of eicosatrienoic acid (C20:3n-3), dihomo-γlinoleic acid (C20:3n-6), and arachidonic acid (C20:4n-6) were also higher (P < 0.04) in pigs fed the high-fiber compared with the corn-soy control.The concentration of total trans fatty acids, however, were higher (P < 0.01) only in backfat of pigs fed the high-fiber compared with the corn-soy control.
For pigs withdrawn from the high-fiber diet and switched to the corn-soy control, fewer differences were observed in fatty acid concentration.The concentration of palmitoleic acid increased (linear; P < 0.03) in jowl fat as the number of days withdrawn from the high-fiber diet increased.The concentration of eicosatrienoic acid decreased (linear; P < 0.01) in belly fat as the number of days withdrawn from the high-fiber diet increased.Most differences existed in the backfat, where total concentration of PUFA, PUFA:SFA ratio, and IV decreased (quadratic; P < 0.03) with the increase in withdrawal time.The difference in total concentration of PUFA was due in part to the change (quadratic; P < 0.03) in concentrations of α-linoleic, linoleic acid, and SWINE DAY 2013 arachidonic acid as withdrawal time increased.Dihomo-γ-linoleic acid concentration also decreased (quadratic; P < 0.01) as withdrawal time increased.Total concentration of PUFA in ham collar fat also increased (quadratic; P < 0.05) as withdrawal time increased, partially because of the increase in α-linoleic and arachidonic acid (quadratic; P < 0.04).The concentration of dihomo-γ-linoleic also increased (quadratic; P < 0.02) as withdrawal time increased from 0 to 20 d.
In summary, pigs fed the high-fiber diet had poorer F/G and caloric efficiency and lower carcass yield compared with pigs fed the corn-soybean meal control diet.Withdrawing pigs from the high-fiber diet and switching them to a corn-soy control diet restored carcass yield when done for the last 15 to 20 d prior to harvest.Withdrawal of highfiber ingredients less than 20 d prior to slaughter, however, did not have a measurable impact on carcass fatty acid composition.  Carcass characteristics were adjusted by using HCW as a covariate.

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3 Percentage yield was calculated by dividing HCW by live weight obtained at the farm before transport to the packing plant. 4Iodine value was measured on the jowl of the carcass at the plant. 5The second-heaviest gilt was selected to represent the pen. 6Values represent the distance from each end of the belly when centered upon a fulcrum point. 7Carcass gain value is calculated as $77.00/cwt of final carcass wt.minus (initial weight x 75% assumed yield x $77.00/cwt).
8 Income over feed cost = revenue/pig -feed cost/pig.The second-heaviest gilt was selected to represent the pen (6 pigs/treatment).The second-heaviest gilt in each pen was selected to represent the pen (6 pigs/treatment).

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2 All values are on a DM basis.

Table 5 .
Fatty acid analysis of ingredients and treatment diets during each phase1,2 1 Values represent the mean of composite samples that were analyzed in duplicate.2Allvaluesareon a DM basis. 3ied distillers grains with solubles.4Wheatmiddlings.

Table 6 .
Effects of high-fiber withdrawal prior to market on growth performance of finishing pigs 1

Table 7 .
Effects of high-fiber withdrawal prior to market in finishing pigs on carcass characteristics and economics Probability, P < High-fiber ingredient withdrawal prior to market, d

Table 8 .
Effects of high-fiber withdrawal prior to market on finishing pig intestinal and organ weights, lb 1

Table 9 .
Effects of high-fiber withdrawal prior to market on finishing pig intestinal and organ weights, % of live weight 1

Table 10 .
Effects of high-fiber withdrawal prior to market on jowl fatty acid analysis1,2 2All values are on a DM basis.

Table 11 .
Effects of high-fiber withdrawal prior to market on belly fatty acid analysis 1,2 Probability, P < High-fiber ingredient withdrawal prior to market, d