Effects of immunological castration (Improvest) on changes in dressing percentage and carcass characteristics of finishing pigs

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1 Published November 24, 2014 Effects of immunological castration (Improvest) on changes in dressing percentage and carcass characteristics of finishing pigs D. D. Boler,* C. L. Puls,* D. L. Clark,* M. Ellis,* A. L. Schroeder, P. D. Matzat, 1 J. Killefer,* 2 F. K. McKeith,* and A. C. Dilger* 3 *Department of Animal Sciences, University of Illinois, Urbana 61801; and Zoetis, Kalamazoo, MI ABSTRACT: The objective was to determine which tissue components contributed to the reduction in carcass yield of immunologically castrated (IC) barrows when compared to physically castrated (PC) barrows. The carcass yield of an IC barrow is less than the carcass yield of a PC barrow. This has historically been attributed to the presence of testicles, but the testes have only accounted for approximately 0.25% of live weight. This experiment included PC barrows, intact males, IC barrows, IC barrows fed ractopamine hydrochloride, and gilts. When the pigs reached 15 wk old, they were weighed, assigned to treatments (intact male or IC barrow), and penned in groups of 4 pigs per pen. Pigs designated for immunological castration were given injections at approximately 16 wk old and approximately 20 wk old. Pigs were eligible for harvest 33 d after the second injection when the average weight of the pen reached 130 kg. Immunologically castrated barrows lost on average 0.7% units more live weight during transport and lairage than PC barrows, intact males, or gilts. Physically castrated barrows had a 1.43% unit advantage over IC barrows in carcass yield. The differences in yield can be attributed to differences in testicles, reproductive tract, intestinal mass, gut fill, and some visceral organs. Testicle weight accounted for a 0.28% unit reduction in carcass yield of IC barrows when compared to PC barrows. Additional reproductive tract weights accounted for differences of 0.10% units. Intestinal mass (empty large intestine, small intestine, and stomach) was 0.2% units heavier in IC barrows when compared to PC barrows. Livers from IC barrows were 200 g heavier (P < 0.05) and kidneys were 40 g heavier than the same organs in PC barrows. These 2 organs combined for a 0.15% unit difference in carcass yield between IC and PC barrows. Gut fill, testicles, reproductive tract, intestinal mass, and the liver and kidney accounted for 0.97 of 1.43% unit differences in carcass yield between IC and PC barrows. Immunologically castrated barrows had less marbling than PC barrows, but there were no other differences in pork quality parameters. Cutability differences were less than reported in previous experiments, but IC barrows still had a 1.0% unit advantage in lean cutting yield and a 0.7% unit advantage in carcass cutting yield when compared to PC barrows. Key words: carcass yield, dressing percentage, gonadotropin releasing factor, immunological castration, Improvest 2014 American Society of Animal Science. All rights reserved. J. Anim. Sci : doi: /jas INTRODUCTION Improvest (gonadotropin releasing factor analog - diphtheria toxoid conjugate; Zoetis, Kalamazoo, MI) was approved for use in the United States as a means to reduce boar taint in intact male pigs. Historically, boar taint issues were controlled by physical castration of 1 Present address: Elanco Animal Health, Greenfield, IN Present address: Oregon State University, Corvallis, OR, Corresponding author: adilger2@illinois.edu Received July 3, Accepted October 24, male pigs early in life. By removing the testicles, sex hormones such as androstenone are effectively eliminated. A problem with physical castration, however, is the elimination of testosterone. Testosterone is key to efficient growth of male pigs as evidenced by the increased growth rate and efficiency of intact males compared with physically castrated (PC) pigs. Immunologically castrated (IC) barrows tend to grow faster and are more efficient (Dunshea et al., 2001; Fàbrega et al., 2010) than PC barrows during the grow finish portion of production. However, the carcass yield (dressing percentage) of an IC barrow is on average 2.71% units less than the car-

2 360 Boler et al. cass yield of a PC barrow (Dunshea et al., 2013) and can be as much as 3.03% units different (Yuan et al., 2012). However, carcass yield can be highly variable and may be related to feed withdrawal duration before slaughter and the age of the pig at the time of second injection. Testicles have accounted for somewhere between 0.20 and 0.28% of ending live weight among 3 studies that have reported testes weight (Dunshea et al., 2001; Pauly et al., 2009; Gispert et al., 2010). Pauly et al. (2009) did report IC barrows had livers that were 141 g heavier than livers from PC barrows, but it has been hypothesized that a portion of the reduction in dressing percentage of an IC barrow is due to increased feed intake (Dunshea et al., 2001) and therefore increased gut fill weight and intestinal mass in IC barrows compared with PC barrows. The objective of this experiment was to determine which tissue components contributed to the reduction in carcass yield of IC barrows when compared to PC barrows. MATERIALS AND METHODS Procedures used for pig evaluation in this experiment were reviewed and approved by the University of Illinois Institutional Animal Care and Use committee. Experimental Design Ninety-six pigs each (Génétiporc G-Performer boars crossed with Fertilis 25 sows; (Génétiporc, Alexandria, MN) in 2 separate blocks (192 total) were housed at the University of Illinois Swine Research Center. Block was considered farrowing group, and there were 2 wk between blocks. The experiment was a randomized complete block design and included PC barrows, intact males, IC barrows, and gilts. There were 48 total pens with 24 pens in each block. Each block had 5 pens each of IC barrows, PC barrows, intact males, and gilts. Each block had an additional 4 pens of IC barrows fed ractopamine hydrochloride (RAC; Paylean, Elanco Animal Health, a division of Eli Lilly and Co., Greenfield, IN). Pigs were selected from an initial population of nearly 200 pigs per block. Litter origin and birth weight were used as allocation criteria to sex (intact male or PC male) to limit initial variation. Physically castrated barrows were physically castrated within 7 d of birth. When the pigs reached 15 wk old, they were weighed, assigned to a treatment (intact male or IC barrow), and penned in groups of 4 pigs of the same sex per pen. When the pigs designated for immunological castration reached approximately 16 wk of age they received the first of two 2 ml subcutaneous injections of an anti-gonadotropin releasing factor immunological product (Improvest). The second injection was administered 4 wk later when the pigs were approximately 20 wk old. Intact males, PC barrows, and gilts did not receive a placebo injection during either injection period. Immunologically castrated barrows designated for RAC treatment were switched to an experimental diet that included 5 mg/kg RAC 7 d after they received the second dose (approximately 17 wk of age). All pigs were individually weighed every 2 wk before the second dose and then each week after receiving the second dose. At 28 d after the second dose pigs were weighed to determine potential final farm weight. Any pen with an average pig BW heavier than 130 kg was selected for harvest, weighed at 32 d after the second injection, tattooed, and transported to the University of Illinois Meat Science Laboratory. The initial group of pigs was harvested at 33 d after the second dose. The selection process was repeated and pigs were harvested at 40 d or 47 d after the second dose as they reached an average BW of 130 kg. Thus, all pigs on the study were harvested over 3 wk within their respective block. Harvest Procedures Pigs were tattooed and weighed at the Swine Research Center without a fast before harvest. Immediately after weighing, feed was removed and pigs were transported to the University of Illinois Meat Laboratory. In lairage, pigs were provided ad libitum access to water but had no access to feed; therefore, pigs were fasted for approximately 12 to 15 h before harvest. Immediately before harvest, pigs were weighed again to determine ending live weight. After weighing, pigs were electrically stunned using a head-to-heart method and exsanguinated under the inspection of the United States Department of Agriculture. Blood was collected and immediately weighed. Pigs were scalded, dehaired, and singed to remove all hair from the carcass. Weight of hair and toenails were not collected. Evisceration The head was removed at the atlas joint and weighed. The tail was removed at the last sacral vertebrae and also weighed. Testicles were removed by making a single cut in the scrotum between the 2 testicles. All scrotal tissue was left on the carcass. The penis and prepuce were removed, separated, and weighed in all male pigs. The remaining male reproductive tract (seminal vesicles, bulbourethral gland, and epididymis) was removed and weighed. Entire female reproductive tracts were removed and weighed as a unit. The remaining viscera were placed in a bag with identification and further dissected. Initially, the full intestinal tract was weighed. The large intestine was separated from the small intestine at the ileocecal junction. The small intestine was separated

3 Carcass yield of immunologically castrated pigs 361 from the stomach between the pylorus of the stomach and the duodenum of the small intestine. The stomach was removed from the esophagus where the esophagus empties into the cardia of the stomach. Each piece of the intestinal tract was rinsed with water to remove all remaining diegesta or fecal material. Gut fill was calculated from the difference of the full intestinal tract and the sum of the empty components. Mesenteric tissue that surrounded the intestinal tract was also weighed. Leaf fat was removed from the abdominal wall on both sides of the carcass and weighed. The kidneys, liver, gall bladder, and spleen were all weighed separately. The pluck (heart, lungs, and trachea) was weighed as a set, separated, and weighed as individual pieces. The stick wound was trimmed and the neck trim tissue was weighed. Carcass Fabrication The carcasses were split down the midline after evisceration. Hot carcass weights were collected approximately 45 min after exsanguination. Hot carcass weight was designated as tail off, leaf fat out, and head removed but both front feet left on the sides. Twenty-four hours after harvest, the right side of each carcass was fabricated into primal and subprimal pieces. Sides were fabricated in the same manner described by Boler et al. (2011, 2012) with the only exception being the shoulder. Shoulders were removed from the loin and belly with a cut perpendicular to the backbone between the second and third ribs. The primal shoulder was weighed with the neck bones in, jowl on, and front foot removed. The neck bones were removed and weighed. The clear plate was removed and weighed. The whole shoulder was calculated as the primal shoulder weight minus the weight of the clear plate and neck bones. The subprimal shoulder pieces were then fabricated by separating the Boston butt from the picnic to form a National Association of Meat Purveyors (NAMP) #406 bone-in Boston butt and a NAMP #405 bone-in picnic shoulder. Each piece was boned out to meet the specifications of NAMP #406A boneless Boston butt and a NAMP #405A boneless picnic shoulder. The boneless picnic shoulder was further fabricated by removing the triceps brachii and weighing the cushion (NAMP #405B). Pork Quality Pork quality measurements for ultimate ph, objective color, subjective color, marbling, and firmness scores and drip loss were conducted by trained University of Illinois Meat Science Laboratory personnel. Measurements were collected on boneless Canadian back loins (NAMP #414) cut at the area of the 10th rib. Ultimate ph was measured using a hand held ph star probe fitted with a glass electrode (SFK Technologies Inc., Cedar Rapids, IA; 2 point calibration: ph 4 and 7). Objective CIE L*, a*, and b* (CIE, 1978) values were collected with a Minolta CR-400 (Minolta Camera Company, Osaka, Japan) using a D65 light source and a 0 observer and an aperture size of 8 mm. Subjective color and marbling scores (NPPC, 1999) and firmness scores (NPPC, 1991) were conducted by a single individual according to standards established by the National Pork Producers Council. Water holding capacity was evaluated using the drip-loss method where a 1.25 cm thick chop was suspended from a fish hook in a Whirl-pak bag for approximately 24 h at 4 C. Chops were weighed before and immediately after suspension. Results were reported as weight lost as a percent of initial weight. Carcass Measurements The left side of each chilled carcass was cut between the 10th and 11th rib interface to expose the LM. Back fat was measured perpendicular to the skin three-fourths the distance from the midline at the 10th rib 48 h postmortem. Loin eye area (LEA) was measured by tracing the face of LM on double matted acetate paper. Loin tracings were traced in duplicate using a Super PLANIX α polar planimeter (Tamaya Technics Inc, Tokyo, Japan) and the average of the 2 measurements was reported as LEA. Fat-Free Lean Determination Fat-free lean determination was conducted on the left side of each carcass 48 h postmortem. Sides were skinned using an air skinner to remove less than 3 mm of skin and tissue. All bones were separated from soft tissue and knife-scraped to remove residual tissue. Sides were divided and weighed based on category of skin, bone, and soft tissue. Soft tissue was prepared for proximate composition analysis in the same manner described by Boler et al. (2011). Fat free lean was calculated with the following equation: {[soft tissue weight (soft tissue weight soft tissue % fat)]/chilled right side weight} 100. Statistical Analyses Data were analyzed with the Mixed procedure of SAS (SAS Inst. Inc., Cary, NC) as a general linear mixed model. Pen served as the experimental unit for all parameters. The fixed effect in the model was treatment (IC barrow, IC barrow + RAC, PC barrow, intact male, or gilt). Replication block interaction was considered a random variable. Homogeneity of variance was tested with the Levene s test or Brown and Forsythe in the case of nonnormal data using the GLM procedure of SAS. Normality of the residuals was tested in the Univariate procedure of SAS with normal probability plots. Least square means were separated with the PDIFF option.

4 362 Boler et al. Table 1. Number of pens selected for harvest per sex based on farm weights >130 kg 1 Days after the second injection Immunologically castrated (IC) barrow IC barrow + ractopamine Physically castrated barrow Intact male Block Block Pigs harvested on Day 47 of block 1 and Day 33 of block 2 were harvested on the same day. Gilt Statistical differences were accepted as significant at P < 0.05 using a 2-tailed test. RESULTS AND DISCUSSION It has been routinely reported that IC barrows grow faster (Dunshea et al., 2001; Pauly et al., 2009; Fàbrega et al., 2010) and have heavier ending live weights (Schmoll et al., 2009; Fàbrega et al., 2010; Boler et al., 2011) than their PC barrow counterparts. All of these experiments harvested pigs on a fixed time post second injection basis. The current experiment, however, selected pigs for slaughter based on a fixed weight basis. Therefore, more IC barrows were harvested on Day 33 after the second injection than PC barrows (Table 1). Table 2. The effect of a gonadotropin releasing factor immunological on visceral weights of finishing pigs Immunologically castrated IC barrow + Physically Intact Gilt (IC) barrow ractopamine castrated barrow male SEM 1 P-value Final farm wt, kg b c ab ab a 1.40 <0.001 Ending live wt, kg b c ab ab a 1.26 <0.01 Transport shrink, % 3.69 c 3.87 c 3.18 b 2.48 a 3.30 b 0.15 < HCW, kg a b a a a 0.96 <0.01 Carcass yield, % a b c a c 0.21 < Tail, kg Testicles, kg 0.38 a 0.35 a 0.88 b 0.01 < Penis, kg b b a c < Prepuce, kg 0.25 a 0.25 a 0.24 a 0.28 b 0.01 <0.01 Residual male reproductive tract, 2 kg 0.37 b 0.36 b 0.24 a 0.83 c 0.02 < Female reproductive tract, kg Full intestinal tract, kg 8.83 c 8.75 bc 8.15 b 7.08 a 8.13 b 0.24 < Empty large intestines, kg 2.12 c 2.14 c 2.00 bc 1.66 a 1.97 b 0.05 < Empty small intestines, kg 1.40 b 1.37 b 1.26 a 1.24 a 1.26 a 0.04 <0.01 Empty stomach, kg 0.67 c 0.66 bc 0.62 ab 0.59 a 0.64 bc Gut fill, 3 kg 4.63 b 4.59 b 4.26 b 3.60 a 4.26 b 0.19 <0.01 Mesenteric tissue, kg 2.03 b 2.03 b 1.98 ab 1.83 a 2.00 b Esophagus, kg a b a b a <0.01 Leaf fat, kg 1.76 bc 1.58 b 2.11 d 1.21 a 1.80 c 0.08 < Kidneys, kg 0.45 b 0.47 b 0.41 a 0.47 b 0.41 a 0.01 < Liver, kg 1.95 cd 1.99 d 1.75 ab 1.84 bc 1.68 a 0.04 < Gall bladder, kg Spleen, kg Pluck, 4 kg 1.60 ab 1.63 ab 1.56 a 1.69 b 1.56 a Lungs, kg Trachea, kg Heart, kg a ab a b a Neck trim, kg Blood, kg 4.88 b 5.09 b 4.43 a 4.97 b 4.57 a 0.11 <0.001 Head, kg 6.35 ab 6.45 bc 6.30 ab 6.62 c 6.28 a 0.07 < SEM: largest reported. 2 Residual male reproductive tract = complete male reproductive tract (testicles + penis + prepuce). 3 Gut fill = full intestinal tract wt (empty small intestine + empty large intestine + empty stomach + esophagus). 4 Pluck = heart + trachea + lungs.

5 Carcass yield of immunologically castrated pigs 363 Table 3. The effect of a gonadotropin releasing factor immunological on visceral weights expressed as a percentage of ending live Immunologically castrated (IC) barrow IC barrow + ractopamine Physically castrated barrow Intact male Gilt SEM P-value Tail, % Testicles, % 0.28 a 0.26 a 0.67 b 0.01 < Penis, % b b a c < Prepuce, % b b a c 0.01 <0.01 Residual male reproductive tract, % 0.28 b 0.26 b 0.18 a 0.64 c 0.01 < Female reproductive tract, % Full intestinal tract, % 6.63 c 6.40 bc 6.20 b 5.39 a 6.24 b 0.15 < Empty large intestines, % 1.60 b 1.57 b 1.52 b 1.26 a 1.51 b 0.04 < Empty small intestines, % 1.05 b 1.00 ab 0.96 a 0.94 a 0.97 a Empty stomach, % 0.50 c 0.48 bc 0.47 ab 0.45 a 0.49 b Gut fill, 1 % 3.48 b 3.35 b 3.24 b 2.73 a 3.27 b 0.12 <0.01 Mesenteric tissue, % 1.53 b 1.49 ab 1.51 b 1.39 a 1.54 b Esophagus, % a b a b ab Leaf fat, % 1.32 c 1.16 b 1.60 d 0.92 a 1.39 c 0.06 < Kidneys, % 0.33 b 0.35 bc 0.31 a 0.36 c 0.31 a 0.01 < Liver, % 1.46 b 1.45 b 1.33 a 1.40 b 1.29 a 0.03 < Gall bladder, % Spleen, % 0.14 a 0.14 a 0.15 ab 0.16 b 0.16 b Pluck, % 1.21 a 1.19 a 1.19 a 1.29 b 1.19 a Lungs, % Trachea, % Heart, % a a a b a Neck trim,% Blood, % 3.65 bc 3.71 c 3.34 a 3.76 c 3.49 ab 0.08 <0.01 Head, % 4.46 a 4.41 a 4.47 a 4.72 b 4.50 a 0.06 < Gut fill = [(Full intestinal tract wt empty intestinal tract wt)/ending live weight] 100. Carcass Yield Immunologically castrated barrows fed RAC had the heaviest hot carcass weights (106.3 kg) of any of the treatment groups. There were no differences in HCW among IC barrows (102.9 kg), PC barrows (103.4 kg), intact males (101.6 kg), and gilts (101.9 kg). Physically castrated barrows (78.72%) and gilts (78.81%) had the greatest carcass yield of all treatment groups. Intact males (77.40%) and IC barrows (77.29%) had the least carcass yield. The magnitude of the difference in carcass yield between IC barrows and PC barrows in the current study (1.43% units) is lower the magnitude of the difference (2.76 and 2.11% units) reported by Boler et al. (2011) and Gispert et al. (2010), respectively. In the case of Boler et al. (2011), pigs were weighed live before a fast and over 24 h before harvest. This is likely a direct contributor to the reduction in carcass yield of IC barrows when compared to PC barrows. The IC barrows fed RAC (77.86%) had an intermediate carcass yield (Table 2). The increase in carcass yield of the IC barrows fed RAC compared with IC barrows not fed RAC was expected. Ractopamine consistently increases carcass yield of physical castrates and gilts although not usually statistically significant at P < 0.05 when fed at doses of 5 mg/kg (Apple et al., 2007). In the current study, 97.94% of the ending live weight of IC barrows, 97.96% of IC barrows fed RAC, 98.24% of PC barrows, 97.50% of intact males, and 98.42% of gilts was accounted for by the summation of the HCW, tail, reproductive tract, full intestinal tract, leaf fat, kidneys, liver, gall bladder, spleen, pluck, neck trim, blood, and the head. The approximately 2% units of ending live weight not accounted for was likely due to toenails, hair, and residual blood that was not captured. There were no differences among any treatment groups for the tail, gall bladder, spleen, lungs, trachea, or neck trim (Table 2). There were also no differences among any treatments for the percentage of live weight for lungs, trachea, and neck trim (Table 3). Several researchers have weighed or measured testicles, bulbourethral glands, and other components of the male reproductive tract (Oonk et al., 1995; Dunshea et al., 2001; Gispert et al., 2010). Pauly et al. (2009) reported the testicles of IC barrows accounted for 0.28% of ending live weight and the testicles of intact males accounted for 0.55% of ending live weight. In the current experiment, the weight of the

6 364 Boler et al. testicles accounted for 0.28% of ending live weight in IC barrows and 0.67% of ending live weight in intact males (Table 3). The 0.28% of ending live weight only accounts for a small portion of the 1.43% unit difference in carcass yield between IC and PC barrows. This still leaves 0.91% units difference in carcass yield that must be accounted for by other visceral and reproductive organs. Visceral Weights Immunologically castrated barrows consume more feed than PC barrows or intact males from approximately 1 wk after they receive the second injection until the time of harvest (Dunshea et al., 2001; Fàbrega et al., 2010). The increase in feed intake of IC barrows compared to other sexes increases gut fill and was offered as a partial contributor to lesser carcass yield by Dunshea et al. (2001). A reduction in carcass yield was reported in IC barrows when compared with both PC barrows and intact males (Gispert et al., 2010). Final farm weight in the current study was increased in IC barrows compared with gilts but was similar to intact males and PC barrows. There were no differences in final farm weights among PC barrows, intact males, and gilts. Immunologically castrated barrows fed RAC were heavier than all other treatments (Table 2). Shrinkage during transport was greatest in IC barrows (3.69%) and IC barrows fed RAC (3.87%) compared with PC barrows and gilts. The transport shrinkage of intact males was less than any other treatment. This reduced the variation in body weights from 7.8 kg at the farm to 6.7 kg at the time of harvest. This approach was used as a means to normalize gut fill. Even so, IC barrows not fed RAC (4.63 kg) had 0.37 kg more gut fill (P = 0.12) than PC barrows (4.26 kg; Table 2), which accounted for 0.24% units reduction in carcass yield (Table 3). There were no differences in gut fill among any treatments except for intact males, which had less (P < 0.05) gut fill than the other treatment groups. Residual male reproductive tracts (everything except for the penis and prepuce) from PC barrows (0.24 kg) were at least 120 g lighter (P < 0.05) than male reproductive tracts from IC barrows fed and not fed RAC. Residual male reproductive tracts from intact males (0.83 kg) were at least 460 g heavier (P < 0.05) than residual male reproductive tracts of IC barrows fed and not fed RAC (Table 2). This attributed a difference of 0.13% units in male reproductive tracts (penis + prepuce + residual male reproductive tract) from IC barrows when compared with PC barrows. There was a total difference of 0.2% units of live weight between IC barrows (3.15%) and PC barrows (2.95%) among the empty large intestine (0.08), empty small intestine (0.09), and empty stomach (0.03). This means the increase in intestinal mass of IC barrows when compared to PC barrows accounted for almost as much of a reduction in carcass yield as the presence of testicles. Pauly et al. (2009) reported livers were 141 g heavier (P < 0.05) and kidneys were 19 g heavier (P > 0.05) in IC barrows when compared to PC barrows. Livers from IC barrows (1.95 kg) in the current experiment were 200 g heavier (P < 0.05) than livers from PC barrows (1.75 kg; Table 2). Kidneys of IC barrows (0.45 kg) were 40 g heavier (P < 0.05) than kidneys from PC barrows (0.41 kg). These 2 organs combined for an additional 0.15% unit difference in carcass yield between IC barrows and PC barrows (Table 3). The summation of the percentage unit differences from gut fill (0.24), the testicles (0.28), reproductive tract (0.13), intestinal mass (0.20), and liver and kidney (0.15) was 1.00% units. The remaining 0.43% unit reduction in carcass yield between IC barrows and physical castrates can be attributed to slight differences in mesenteric tissue, esophagus, trachea, heart, lungs, blood, and the head. Carcass Characteristics Immunologically castrated barrows fed RAC had larger (P < 0.05) LEA than IC barrows not fed RAC, PC barrows, and intact males. There were no differences in LEA between IC barrows fed RAC and gilts or between gilts and the other 3 treatment groups. Intact males (1.82 cm) had the least (P < 0.05) 10th rib back fat among all treatment groups. Skin weights were relatively similar among all treatments except intact males (4.00 kg), which had the heaviest skin weight. Bone weights were also heavier in intact males when compared with IC barrows not fed RAC, PC barrows, and gilts. As expected, intact males (18.27%) had the lowest (P < 0.05) percentage of soft tissue fat and PC barrows (28.61%) had the greatest percentage of soft tissue fat (Table 4). Immunologically castrated barrows fed RAC (21.80%) had 3.53% units more (P < 0.05) soft tissue fat that intact males but were still less (P < 0.05) than IC barrows not fed RAC (24.48%) or gilts (60.63%). This resulted in IC barrows fed RAC (63.32%) and intact males (64.48%) having the greatest fat-free lean percentages among all treatments. Because of the high percentage of soft tissue fat, PC barrows had the least (P < 0.05) fat-free lean percentage (58.08%) among all treatment groups. Fat-O-Meater (Fat-O-Meater measurments, SFK Technology Fat-O-Meater, Herley, Denmark) measurements were reflective of objective carcass measurements, but the calculation for estimated carcass lean was not able to capture magnitude of differences observed with fat-free lean determination (Table 4). Boler et al. (2011) reported comparison values between fat-free lean determination and Fat-O-Meater carcass lean estimates among PC barrows, intact males, and IC barrows fed different dietary

7 Carcass yield of immunologically castrated pigs 365 Table 4. The effect of a gonadotropin releasing factor immunological on carcass characteristics of finishing pigs Immunologically castrated (IC) barrow IC barrow + ractopamine Physically castrated barrow Intact male Gilt SEM P-value Carcass measurements Loin eye area, cm a b a a ab Backfat, cm 2.43 cd 2.21 bc 2.52 d 1.82 a 2.11 b 0.10 < Left side wt, kg ab c b a ab 0.52 <0.01 Skin wt, kg 3.63 ab 3.74 b 3.50 a 4.00 c 3.58 a 0.05 < Bone wt, kg 5.84 ab 6.01 bc 5.70 a 6.19 c 5.76 a 0.09 <0.01 Soft tissue wt, kg b c b a b 0.48 < Soft tissue moisture, % b c a d b 0.65 < Soft tissue fat, % c b d a c 0.83 < Fat-free lean, % b c a c b 0.61 < Fat-O-Meater 1 Loin depth, mm ab c c a ab 1.20 <0.01 Fat depth, mm c b c a b 0.76 < Estimated carcass lean, % a bc a c b 0.60 < Fat-O-Meater measurments, SFK Technology Fat-O-Meater, Herley, Denmark. lysine inclusion levels. In Boler s study, the Fat-O-Meater was effective at predicting carcass lean estimates between 55 and 57% but underestimated carcass lean values when fat-free lean was determined between 58 and 60%. Pigs in the current study were heavier at the time of harvest and had larger LEA than Boler et al. (2011) and may contribute to the underestimation of carcass lean by the Fat-O-Meater in the current study. Pork Quality It is commonly reported that pork quality parameters such as ph, water holding capacity, color, and tenderness are not affected by immunological castration (D Souza and Mullan, 2003; Pauly et al., 2009; Boler et al., 2011). These results are similar in that there were no differences among any treatment groups for pork loin cook loss, objective L*, a*, b*, or subjective color, marbling, and firmness (Table 5). There were also no differences in ultimate ph among males in the study (IC barrows with and without RAC, PC barrows, or intact males). Gilts, however, had a 0.09 lower (P < 0.05) loin muscle ultimate ph when compared with IC barrows and IC barrows fed RAC but were similar to PC barrows and intact males. With regards to fresh meat water-holding capacity, IC barrows not fed RAC Table 5. The effect of a gonadotropin releasing factor immunological on fresh loin quality of finishing pigs Immunologically castrated (IC) barrow IC barrow + ractopamine Physically castrated barrow Intact male Gilt SEM P-value Loin chop cook loss, 1 % ph 5.64 b 5.64 b 5.59 ab 5.59 ab 5.55 a Objective color L* a* b* Subjective evaluations 2 Color Marbling Firmness Loin composition Moisture, % b b a c ab 0.18 < Fat, % 2.40 bc 2.14 ab 3.01 d 1.99 a 2.65 cd 0.17 < Drip loss, % 4.20 a 5.47 b 5.39 b 5.01 b 5.44 b Cook loss averaged over 4 different aging days. 2 Subjective evaluations based on National Pork Producers Council standards (NPPC, 1991, 1999).

8 366 Boler et al. Table 6. The effect of a gonadotropin releasing factor immunological on right side carcass cut-out values from the shoulder and loin of finishing pigs Immunologically castrated (IC) barrow IC barrow + ractopamine Physically castrated barrow Intact male Gilt SEM P-value Whole shoulder, 1 kg bc c ab c a 0.14 <0.01 % chilled side wt b b ab c a 0.20 < Neck bones, kg 0.90 a 0.89 a 0.88 a 0.99 b 0.93 ab % chilled side wt 1.82 a 1.76 a 1.76 a 2.02 b 1.89 a 0.06 <0.01 Clear plate, kg % chilled side wt Bone-in Boston, kg 4.08 a 4.35 b 4.04 a 4.25 b 4.01 a 0.07 <0.01 % chilled side wt 8.27 ab 8.55 bc 8.12 a 8.69 c 8.17 a 0.11 <0.01 Boneless Boston, kg 3.72 ab 3.93 c 3.71 a 3.85 bc 3.65 a 0.06 <0.01 % chilled side wt 7.55 ab 7.72 bc 7.46 a 7.89 c 7.44 a 0.09 <0.01 Bone-in picnic, kg 5.76 bc 5.87 c 5.64 ab 5.94 c 5.43 a 0.08 <0.01 % chilled side wt b b ab c a 0.14 < Picnic bones, kg 1.01 b 1.01 b 0.96 a 1.06 b 0.96 a 0.02 <0.01 % chilled side wt 2.05 b 1.98 ab 1.93 a 2.16 c 1.95 a 0.03 < Boneless picnic, kg 4.28 bc 4.46 c 4.21 b 4.38 bc 4.03 a 0.07 <0.01 % chilled side wt 8.66 bc 8.76 bc 8.47 ab 8.96 c 8.21 a Cushion, kg 1.13 b 1.14 b 1.08 ab 1.10 ab 1.04 a % chilled side wt Jowl, kg 1.72 c 1.70 c 1.77 c 1.57 a 1.66 b 0.04 <0.01 % chilled side wt 3.47 bc 3.34 ab 3.55 c 3.21 a 3.39 b 0.07 <0.01 Whole loin, kg b c c a bc 0.14 < % chilled side wt b b c a c 0.18 < Trimmed loin, kg a b a a a % chilled side wt a ab ab ab b Fat back, kg 2.58 b 2.97 c 2.90 c 1.99 a 2.50 b 0.12 < % chilled side wt 5.23 b 5.84 c 5.83 c 4.07 a 5.09 b 0.23 < Canadian back, kg 4.00 a 4.34 b 4.01 a 4.04 a 4.18 ab 0.07 <0.01 % chilled side wt 8.11 a 8.54 b 8.07 a 8.26 ab 8.51 b Tenderloin, kg 0.45 a 0.50 b 0.44 a 0.46 a 0.46 a 0.01 <0.01 % chilled side wt 0.91 ab 0.99 c 0.89 a 0.95 bc 0.93 ab Sirloin, kg 0.82 ab 0.88 c 0.82 a 0.86 bc 0.83 ab % chilled side wt 1.67 ab 1.73 bc 1.64 a 1.76 c 1.69 abc Back ribs, kg 0.76 a 0.83 c 0.77 ab 0.79 b 0.79 ab 0.01 <0.01 % chilled side wt 1.55 a 1.63 b 1.54 a 1.62 b 1.62 b 0.02 <0.01 Backbone, kg 1.84 a 1.82 a 1.83 a 1.97 b 1.89 ab % chilled side wt 3.72 ab 3.59 a 3.68 a 4.04 c 3.85 b 0.08 < a c Means within a row for experimental treatments without a common superscript differ (P < 0.05). 1 Whole shoulder = shoulder separated between the second and third rib and the jowl, front foot, and neck bones removed. had the least drip loss percentage when compared with all other treatment groups. There were no differences (P > 0.05) among other treatment groups for drip loss. Physical castrates (3.01%) had the greatest amount of extractible lipid of any treatment group and were 1.02% units greater than intact males (1.99%), which had the least amount of extractible lipid of all treatment groups. There were no differences in extractible lipid between IC barrows (2.40%) and IC barrows fed RAC (2.14%). Boler et al. (2011) reported no differences in extractible lipid between IC barrows and PC barrows and between IC barrows and intact males when each was fed the same diet specifically formulated for the appropriate control. Carcass Cutability There were no statistical differences in the primal weights between IC barrows not fed RAC and PC barrows for the bone-in Boston butt, boneless Boston butt, bonein picnic, boneless picnic, bone-in trimmed loin, bone-in trimmed ham, or the trimmed belly (Tables 6 and 7). There were also no differences in the subprimal components of the shoulder or loin. Immunologically castrated barrows not fed RAC had 0.05 kg heavier (P < 0.05) shank meat portions than PC barrows (Table 7). Trimmed bone-in whole hams from IC barrows not fed RAC (20.76%) did make up a larger percentage of chilled right side weight than trimmed bone-in hams from PC barrows (20.01%). This is

9 Carcass yield of immunologically castrated pigs 367 Table 7. The effect of a gonadotropin releasing factor immunological on right side carcass cut-out values from the ham and belly of finishing pigs Immunologically castrated (IC) barrow IC barrow + ractopamine Physically castrated barrow Intact male Gilt SEM P-value Feet, kg 1.36 b 1.37 b 1.28 a 1.46 c 1.29 a 0.02 < % chilled side wt 2.75 c 2.69 bc 2.58 a 3.00 d 2.62 ab 0.03 < Whole ham, kg a b a a ab % chilled side wt ab ab a b b Trimmed ham, kg ab c 9.95 a bc b 0.12 <0.01 % chilled side wt b b a c b 0.21 < Inside, kg 1.86 ab 2.00 c 1.85 a 1.96 c 1.95 bc % chilled side wt 3.78 ab 3.93 bc 3.71 a 4.01 c 3.96 c 0.06 <0.01 Outside, kg 2.59 a 2.78 b 2.57 a 2.72 b 2.70 b 0.04 <0.01 % chilled side wt 5.23 a 5.47 b 5.17 a 5.57 b 5.50 b 0.08 <0.01 Knuckle, kg % chilled side wt Light butt, kg % chilled side wt Shank meat, kg 0.81 b 0.84 b 0.76 a 0.83 b 0.78 a 0.01 < % chilled side wt 1.65 b 1.65 b 1.54 a 1.69 b 1.58 a 0.02 <.0001 Ham bones, kg 1.34 a 1.33 a 1.30 a 1.44 b 1.30 a 0.02 < % chilled side wt 2.71 b 2.61 a 2.62 a 2.95 c 2.65 ab 0.04 <.0001 Whole belly, kg 8.83 b 9.17 c 8.95 bc 8.53 a 8.72 ab 0.13 <0.01 % chilled side wt ab b b a ab Natural Fall Belly, kg 7.20 bc 7.45 c 7.34 c 6.80 a 7.05 ab 0.12 <0.001 % chilled side wt bc bc c a b 0.15 <0.01 Trimmed belly, kg 5.86 bc 6.10 c 6.05 c 5.44 a 5.76 b 0.11 < % chilled side wt bc bc c a b 0.17 < Spareribs, kg 1.63 a 1.72 b 1.61 a 1.73 b 1.67 ab 0.03 <0.01 % chilled side wt 3.30 ab 3.38 b 3.23 a 3.54 c 3.41 bc Teat line trim, kg % chilled side wt Skin from the teat line, kg 0.16 ab 0.17 b 0.15 a 0.20 b 0.16 ab 0.01 < % chilled side wt 0.33 a 0.33 a 0.30 a 0.41 b 0.33 a 0.01 < partially reflective of the difference in shank meat weights. Percentage of chilled side weight from the shank meat of IC barrows not fed RAC (1.65%) was slightly greater (P < 0.05) than the shank meat percentage from PC barrows (1.54%). Even though there were few statistical differences in cutability components between IC barrows not fed RAC and PC barrows, IC barrows had numerically heavier (P > 0.05) bone-in Boston butts and picnics, boneless Boston butts and picnics, shoulder cushions, tenderloins, trimmed bone-in hams, inside and outside hams, and knuckles. Table 8. The effect of a gonadotropin releasing factor immunological on carcass cutability of finishing pigs Immunologically castrated (IC) barrow IC barrow + ractopamine Physically castrated barrow Intact male Gilt SEM P-value Right side chilled wt, kg a b a a a Lean cutting yield, 1 % ab b a c b 0.42 < Boneless lean cutting yield, 2 % ab cd a d bc 0.39 < Carcass cutting yield, 3 % ab cd a d bc 0.33 <0.01 Boneless carcass cutting yield, 4 % ab c a c bc 0.35 < Lean cutting yield = [(trimmed ham + trimmed loin + Boston + picnic)/right chilled side wt] Boneless lean cutting yield = [(inside ham + outside ham + knuckle + light butt + shank + Canadian back + tenderloin + sirloin + boneless Boston + boneless picnic)/right chilled side wt] Carcass cutting yield = [(lean cutting yield components + trimmed belly)/right chilled side wt] Boneless carcass cutting yield = [(Boneless lean cutting yield components + trimmed belly) right chilled side wt] 100.

10 368 Boler et al. The magnitude of difference among all treatments for lean cutting yield was 3.25% units. Physically castrated barrows (61.48%) had a lesser (P < 0.05) lean cutting yield than IC barrows fed RAC (63.42%), intact males (64.73%), and gilts (62.83%). However, there were no differences between IC barrows not fed RAC (62.48%) and PC barrows (Table 8). Even so, IC barrows still had a 1.0% unit advantage in lean cutting yield and 0.7% unit advantage in carcass cutting yield when compared to PC barrows. Boler et al. (2011, 2012) reported a 2.5% unit advantage in lean cutting yield and carcass cutting yield of IC barrows compared to physical castrates when IC barrows were fed a diet with more total lysine. In contrast, pigs in the current study were all fed the same diet. These data, along with previously reported data, further confirm the need for IC barrows to be fed a diet higher in total lysine than normally fed to PC barrows to realize full cutability potential. Immunologically castrated barrows fed RAC had heavier (P < 0.05) bone-in Boston butts, boneless Boston butts, bone-in trimmed loins, Canadian back loins, tenderloins, sirloins, back ribs, bone-in trimmed hams, inside hams, outside hams, and spareribs than IC barrows not fed RAC (Tables 6 and 7). This resulted in a 1.32% unit advantage (P < 0.05) in boneless lean cutting yield and a 1.48% unit advantage (P < 0.05) in boneless carcass cutting yields of IC barrows fed RAC when compared to IC barrows not fed RAC. These advantages demonstrate that RAC can be used in IC barrows to improve cutability with the same effectiveness as historically observed in PC barrows and gilts. Conclusion Physically castrated barrows had a 1.43% unit advantage in carcass yield when compared to IC barrows not fed RAC. The difference in carcass yield between the 2 sexes can be attributed to 0.24% unit more gut fill, 0.28% units heavier testicles, 0.13% unit more additional male reproductive tract weight, 0.20% units more intestinal mass, and 0.15% units difference between the liver and kidney. Historically, testicles have been blamed for the reduction in carcass yield of IC barrows when compared with PC barrows. These data show that testicles do reduce carcass yield of IC barrows; however, gut fill and other tissues also contribute to the reduction in carcass yield. Drop value may actually be greater in IC barrows relative to PC barrows due to increased liver and kidney weights. Boler, D. D., J. Killefer, D. M. Meeuwse, V. L. King, F. K. McKeith, and A. C. Dilger Effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of immunologically castrated male pigs. J. Anim. Sci. 90: Boler, D. D., L. W. Kutzler, D. M. Meeuwse, V. L. King, D. R. Campion, F. K. 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