Effects of increasing lysine on carcass composition and cutting yields of immunologically castrated male pigs

Effects of supplemental methionine sources in finishing pig diets on growth performance, carcass characteristics, cutting yields, and meat quality

Supplemental methionine (Met) is widely used within the swine industry; however, data are limited regarding the effect of Met sources on carcass cutability and meat quality. The objective was to determine the effects of L-Met (LM, 99%), DL-Met (DLM, 99%), or calcium salt of DL-Met hydroxyl analog (MHA, 84%) in finishing pig diets on carcass characteristics and meat quality. At 9 weeks of age, pigs (N = 240) were allocated to 60 single-sex pens for a four-phase finishing trial that lasted 104 d. Pigs were fed a common grower diet until day 56 where pens were randomly allotted to one of the three experimental diets. For the remaining 7 wk of the finisher phase, pigs (BW = 79.9 ± 0.80 kg) were fed diets containing LM, DLM, or MHA, with the supplemental Met source providing 25% of standardized ileal digestible (SID) Met + cysteine (Cys) requirement based on 65% bioefficacy for MHA in comparison with LM or DLM. One pig per pen was slaughtered at the study conclusion (on day 104), and the left sides of carcasses were fabricated into subprimal cuts to determine carcass-cutting yields. Loin quality including proximate composition and shear force were measured. Hot carcass weight was not different (P = 0.34) between treatments (LM 104.5 kg; DLM 103.0 kg; MHA 101.5 kg), moreover, loin eye area was not different (P = 0.98) between treatments (LM 52.65 cm²; DLM 52.49 cm²; MHA 52.81 cm²). Boneless carcass-cutting yield was not different (P = 0.56) between treatments (LM 54.97 kg; DLM 54.82 kg; MHA 54.52 kg). Loin pH was not different (P = 0.24) between treatments (LM 5.45; DLM 5.48; MHA 5.45). However, drip loss tended to be reduced (P = 0.11) by the DLM treatment (5.58%) compared with LM (7.03%) and MHA (6.68%) treatments. Shear force was not different (P = 0.85) between treatments (LM 3.03 kg; DLM 3.06 kg; MHA 3.10 kg). However, cook loss tended to be reduced (P = 0.06) by the DLM treatment (16.20%) compared with LM (18.18%) and MHA (18.50%) treatments. These data suggest that only minimal differences in carcass cutability and meat quality can be attributed to Met source in finishing pig diets when using 65% bioefficacy for MHA relative to L-Met or DL-Met.

Using an economic simulation model to identify key drivers of profitability and estimate the environmental sustainability impact of immunization against gonadotropin-releasing factor (GnRF) in male and female pigs intended for market

An existing model was used to identify key drivers of profitability and estimate the impact on environmental sustainability when immunizing finishing pigs against GnRF with Improvac®. The model estimated performance and economic differences between immunized (IM) and non-IM pigs from the perspective of producers and packers, based on two recent meta-analyses in male and female pigs. It was populated with data from 9 countries in four continents (Europe, Asia, North and Latin-America). One-way sensitivity analyses (OWSA) were used to define key drivers of profitability. When changing the country specific input data over a range of ±20%, most OWSA did not reverse the mathematical sign of incremental net return between IM and non-IM pigs as calculated in base case analyses. Only the difference in feed conversion rate between IM and untreated female pigs was a key driver of profitability. The parameters with the highest impact on outcomes were similar across countries and expectable (feed costs), or explainable (parameters with statistical differences between IM and non-IM pigs in meta-analyses). In both single-gender herds, Improvac® reduced the environmental impact of pig production by improving feed efficiency (FE), the key driver of environmental burden. In a 50/50 mixed gender herd, IM pigs consumed less feed and gained more weight in 7 out of 9 countries; in the other two countries the FE calculated for the additional weight gain in IM pigs was >1.00, i.e., each additional kilogram of weight gain was associated with less than one additional kilogram of feed consumed.

The effects of dietary net energy on grow-finish performance and carcass characteristics of male market pigs managed with immunological castration (Improvest)

The objective was to determine the effects of dietary net energy (NE) during the grow-finish period on live performance and carcass characteristics of intact male pigs managed with immunological castration (Improvest) compared with physically castrated (PC) male pigs. The 101-d study began when 1,008 pigs (504 intact male pigs and 504 PC male pigs; 10 wk old) were allocated by weight to 48 pens with 21 intact males or 21 PC males per pen. Three dietary NE treatments were fed to pigs using five dietary phases (dietary programs were formulated according to standardized ileal digestible lysine requirements of Improvest males or PC males) to provide an average of 2,212 kcal/kg (low NE), 2,337 kcal/kg (medium NE), or 2,462 kcal/kg (high NE). The experiment was designed and analyzed as a 2 × 3 factorial with main effects of Improvest management and NE. For the overall study period, there were no significant interactions between Improvest management and NE (P ≥ 0.19) for average daily feed intake (ADFI), average daily gain (ADG), or gain:feed (G:F). There were also no significant interactions between Improvest management and NE (P ≥ 0.06) for carcass characteristics. Improvest males consumed less feed (5.3% lower ADFI; P < 0.01), grew faster (5.1% greater ADG; P < 0.01), and were more efficient (11.2% greater G:F; P < 0.01) compared with PC males. Hot carcass weight (HCW) did not differ (P = 0.16) between Improvest males and PC males (attributed to 1.6 percentage unit lower dressing percentage for Improvest males; P < 0.01); however, Improvest males were leaner (0.9 mm less backfat and 0.65% greater predicted lean yield; P < 0.01) compared with PC males. For the overall study period, pigs fed low NE and medium NE diets consumed 7.5% and 4.6% more feed (P < 0.01) than pigs fed high NE diets, respectively, and pigs fed low NE diets grew 1.7% slower (P < 0.02) than pigs fed medium NE and high NE diets. This resulted in pigs fed low NE diets having 4.4% lower G:F compared with pigs fed medium NE and 8.6% lower G:F compared with pigs fed high NE diets (P < 0.01). Pigs fed low NE had 3.0 kg lighter (P < 0.01) HCW compared with medium NE, while high NE had intermediate HCW that did not differ from the other two treatments. Overall, typical Improvest response levels for live performance and carcass characteristics when compared with PC males were achieved for each of the NE treatments evaluated in this study.

Effects of maternal inflammation on growth performance, carcass characteristics, and meat quality of offspring pigs

The objective of this research was to determine the effects of mid-gestational maternal inflammation on performance, carcass characteristics, and meat quality of offspring. Pregnant gilts were administered either lipopolysaccharide (LPS; n = 7) or saline (CON, n = 7) from days 70 to 84 of gestation. Gilts assigned to the LPS treatment were administered an intravenous injection of reconstituted LPS every other day with a beginning dose of 10 μg LPS/kg body weight and subsequent doses increasing by 12%, while CON gilts received intravenous injections of comparable volumes of saline. Gilts farrowed naturally, and at day 66 of age, a total of 59 pigs, both barrows and gilts began a 3-phase feeding regimen designed to meet or exceed nutrient requirements for growing-finishing pigs. Pigs were weighed on days 0, 35, 70, and 105 of the finishing trial to determine average daily gain, average daily feed intake, and gain-to-feed ratio (G:F). On day 106, pigs were slaughtered under the supervision of the U.S. Department of Agriculture Food Safety Inspection Service. Ending live weight, hot carcass weight, and dressing percentage were determined. The left side of carcasses was weighed and fabricated to determine carcass cutting yields. The semitendinosus was collected for histological samples. Fresh belly characteristics and loin quality were measured. Two chops were collected for Warner-Bratzler shear force and proximate analysis. No differences (P ≥ 0.13) between LPS and CON pigs were observed for growth performance in phases 1, 2, 3, or overall (days 0 to 105) performance with the exception of overall G:F reduced in CON pigs compared with LPS pigs (P = 0.03). There was a tendency for carcass yield to be reduced (P = 0.06; 0.82% units) in LPS pigs compared with CON pigs. Additionally, longissimus muscle area tended to be reduced (P = 0.10) 2.27 cm2 in LPS compared with CON pigs. Loin chop quality traits including instrumental color, subjective color, marbling, firmness, pH, and drip loss were not different (P ≥ 0.09) between LPS and CON pigs. Fresh belly characteristics were not different (P ≥ 0.22) between LPS and CON pigs. There were no differences in primal and subprimal weights, except that LPS pigs tended to have a reduction (P ≥ 0.07) in tenderloin and Canadian back weights compared with CON pigs. Furthermore, LPS pigs had no differences (P ≥ 0.25) in muscle fiber composition or size; however, LPS pigs tended (P = 0.10) to have a 13% reduction in estimated muscle fibers number compared with CON pigs. In summary, mid-gestational inflammation did not result in reduced meat quality, growth performance, or carcass yields of offspring.

Effects of feeding high oleic soybean oil to growing-finishing pigs on loin and belly quality

Feeding growing-finishing pigs supplemental fat is a common practice in the swine industry and can result in improved feed efficiency and reduced feed intake; however, dietary lipids also play a key role in determining pork quality. Objectives of the study were to evaluate the effects of feeding graded levels of high oleic soybean oil (HOSO) on loin and belly quality. A total of 288 pig raised in two separate blocks (144 pigs each) were assigned to one of four diets containing either 25% dried distiller's grains with solubles (DDGS), 2% high oleic soybean oil (HOSO2), 4% high oleic soybean oil (HOSO4), or 6% high oleic soybean oil (HOSO6). Following the conclusion of the feeding trial, 144 pigs were slaughtered at the University of Illinois Meat Science Laboratory. Following fabrication, loins were collected for the evaluation of fresh quality measurements and color stability. Belly quality and fatty acid composition were evaluated using skin-on natural fall bellies. There were no differences (P ≥ 0.11) in pH, visual color, lightness (L*), drip loss, or WBSF among dietary treatments. However, visual marbling was increased (P ≤ 0.01) in loin chops from pigs fed HOSO4 and HOSO6 treatments compared with chops from pigs fed the DDGS dietary treatment. Additionally, loin chops were more red (a*) (P ≤ 0.01) from pigs fed HOSO diets when compared with pigs fed DDGS. Extractable lipid was decreased (P ≤ 0.01) in fresh loin chops from pigs fed DDGS and HOSO2 diets compared with pigs fed HOSO6. There were no differences (P ≥ 0.75) in trained sensory tenderness, juiciness, or flavor for loin chops from pigs fed different dietary treatments. Pork fatty acid composition was altered by dietary HOSO inclusion, with pigs fed DDGS having (P ≤ 0.01) the greatest concentration of C16:0 and was decreased with increasing levels of HOSO inclusion. Inversely, the percentage of C18:1n-9 was least (P ≤ 0.01) in pigs fed DDGS and increased with increasing levels of HOSO inclusion. Pigs fed DDGS produced wider (P ≤ 0.03) and thinner (P ≤ 0.04) bellies with reduced flop distance compared with pigs fed HOSO diets. Overall, HOSO diets did not negatively affect fresh loin quality or sensory traits of loin chops. Furthermore, feeding HOSO to swine resulted in bellies containing greater percentages of oleic acid and reduced percentages of palmitic and linoleic acid.

Effects of feeding high oleic soybean oil to growing-finishing pigs on growth performance and carcass characteristics

Feeding growing-finishing pigs supplemental fat is a common practice in the swine industry and can result in improved feed efficiency and reduced feed intake; however, dietary lipids also play a key role in determining pork composition. The objectives of the current study were to evaluate the effects of feeding graded levels of high oleic soybean oil (HOSO) on growth performance and carcass characteristics. A total of 288 pigs raised in two separate blocks (144 pigs each) were assigned to one of four diets containing either 25% dried distiller's grains with solubles (DDGS), 2% high oleic soybean oil (HOSO2), 4% high oleic soybean oil (HOSO4), or 6% high oleic soybean oil (HOSO6). Pigs were housed 4 per pen and fed for 98 d using a 3-phase feeding system. Pigs were individually weighed and feed intake was recorded throughout the trial to calculate average daily feed intake (ADFI) and gain to feed ratio (G:F). A total of 144 pigs were transported to the University of Illinois Meat Science Laboratory and fabricated into primal and subprimal cuts to calculate carcass cutting yields. Differences in growth performance were observed, with pigs fed the DDGS treatment exhibiting greater (P ≤ 0.01) overall ADFI consuming 0.21, 0.18, and 0.28 kg/d more than HOSO2, HOSO4, and HOSO6 diets, respectively. Pigs fed the HOSO6 diet had greater (P ≤ 0.03) overall G:F than pigs fed DDGS and HOSO2 diets but did not differ (P = 0.12) from pigs fed HOSO4. Furthermore, differences in carcass traits were observed. Hot carcass weight was increased (P ≤ 0.03) in pigs fed the HOSO6 diet compared with pigs fed the DDGS and HOSO2 diets, while pigs fed HOSO4 did not differ (P > 0.05) from either extreme. Additionally, pigs fed HOSO4 and HOSO6 produced fatter (P ≤ 0.01) carcasses with reduced (P ≤ 0.01) standardized fat-free lean. Minimal differences were observed in primal weights expressed as a percentage of chilled side including bone-in Boston butt, trimmed loin, and trimmed ham with primal weights decreasing with increasing inclusion of dietary HOSO. Overall, pigs fed HOSO2 had reduced ADFI with similar backfat thickness and standardized fat-free lean compared with pigs fed the DDGS treatment. However, pigs fed HOSO 4% and 6% not only had improvements in ADFI and G:F but also had increased backfat thickness, which resulted in reductions in standardized fat-free lean and primal weights expressed as a percentage of chilled side weight.

High inclusion rates of hybrid rye instead of corn in diets for growing-finishing pigs do not influence the overall growth performance and most carcass traits are not influenced by hybrid rye

It was hypothesized that hybrid rye may replace corn in diets for growing and finishing pigs without impacting growth performance, carcass characteristics, or meat quality. A total of 128 pigs (23.69 ± 2.51 kg) were allotted to four treatments with eight replicate pens per treatment. Phases 1 and 2 diets were fed for 35 d each and phase 3 diets were fed for 27 d. Within each phase, pigs were fed a control corn and soybean meal diet or a diet in which 33%, 66%, or 100% of the corn in the control diet was replaced with hybrid rye. Average daily gain (ADG) and average daily feed intake (ADFI) decreased (linear, P < 0.05) in phase 1 with increased dietary inclusion of hybrid rye. In phase 3, gain:feed (G:F) increased and then decreased (quadratic, P < 0.05) with more hybrid rye in the diet. Overall ADG, ADFI, and G:F did not differ among treatments. Diet did not impact most carcass traits, but loin (visual) and backfat (instrumental L*) color were paler (linear, P < 0.05) with greater inclusion of hybrid rye in the diet. Organ weights increased (linear, P < 0.05) with increased dietary hybrid rye. In conclusion, pigs fed hybrid rye consumed less feed in phase 1, resulting in reduced ADG, but growth performance for the entire growing-finishing period did not differ among treatments. Hybrid rye may replace all the corn in growing and finishing pig diets without diminishing growth performance or carcass quality, but feed intake may be reduced at high inclusion rates.

Ante-and post-mortem strategies to improve the meat quality of high-value muscles harvested from farmed male common eland (Taurotragus oryx)

The effects of immunocastration, pelvic suspension and wet ageing on the meat quality of the longissimus lumborum et thoracis (LTL) and biceps femoris (BF) muscles of male common eland were evaluated. Ten subadult males were either immunocastrated (n = 5) or remained intact (n = 5) throughout a four-month growth trial, after which their carcass sides were randomly allocated to either pelvic- or Achilles-suspension. The LTL and BF were further aged for 14 days, measuring changes in the physical quality weekly. The sensory quality of the LTL and BF were determined after ageing (8/9 days, respectively). Immunocastration had minimal effects on the meat quality of male eland, but pelvic suspension decreased the shear force. All muscles reached minimum shear force after seven days of ageing, and the panellists ranked the pelvic-suspended muscles higher for tenderness traits. Incorporating pelvic suspension and wet ageing into the commercial processing of eland carcasses should be considered to improve overall meat quality.

Performance, carcass and meat quality of pigs submitted to immunocastration and different feeding programs

The feed restriction of pigs aims to improve the nutrient utilization of the diet, reduce carcass fat and increase lean meat. Immunocastration is a painless, reversible technique that improves animal welfare, decreases boar taint in meat, leading to lower fat deposition and increases lean meat. This study aimed at evaluating either feeding (restricted) programs (FP) and castration categories (surgically castrated × immunocastration) in terms of pig performance, carcass traits and meat quality. Castration category and FP did not influence marbling, initial pH and drip loss in loin and ham. However, immunocastrated pigs presented lighter loins and hams with lower ultimate pH, compared to the surgically castrated pigs. The FP with lower feed volume resulted in higher ultimate pH. Immunocastrated males had a higher live weight than those surgically castrated. Also, the more the feed supply decreased, the better the feed conversion. Immunocastrates had lower carcass yields, however these pigs had their backfat thickness decreased and lean meat increased in the carcass, without affecting the loin depth.

Effect of porcine reproductive and respiratory syndrome virus infection and soy isoflavone supplementation on carcass cutability and meat quality of pigs

The objective was to evaluate the effects of porcine reproductive and respiratory syndrome virus (PRRSV) infection and dietary soy isoflavone (ISF) supplementation on carcass cutability and meat quality of commercial pigs. Barrows (21 d of age) were randomly allotted to experimental treatments that were maintained throughout the study: noninfected pigs received an ISF-devoid control diet (CON, n = 22) and infected pigs received either the control diet (PRRSV-CON, n = 20) or that supplemented with total ISF in excess of 1,500 mg/kg (PRRSV-ISF, n = 25). Pigs were penned by treatment, with six pigs within a pen. Following a 7-d adaptation, weanling pigs were inoculated once intranasally with either a sham-control (phosphate buffered saline [PBS]) or live PRRSV (1 × 105 tissue culture infective dose [TCID]50/mL, strain NADC20). Pigs were maintained on experimental diets for 166 d after inoculation and then slaughtered (192 or 194 d of age; approximately 120 kg body weight [BW]). At 1-d postmortem, left sides were separated between the 10th and 11th rib for the determination of loin eye area (LEA), backfat (BF) thickness, and loin quality (ultimate pH, instrumental color, drip loss, visual color, marbling, and firmness). Loin chops were aged 14 d postmortem prior to Warner-Bratzler shear force (WBSF) determination. Belly width, length, thickness, and flop distance were determined. Data were analyzed as a one-way ANOVA with pig as the experimental unit. Carcass yield, LEA, BF, and estimated lean percentage did not differ (P > 0.26) among treatments. Loins from CON pigs had increased ultimate pH (P = 0.01), reduced L* scores (P = 0.005) coupled with darker visual color scores (P = 0.004), were firmer (P < 0.0001), and exhibited reduced drip loss (P = 0.01) compared with PRRSV-CON and PRRSV-ISF pigs. However, WBSF did not differ (P = 0.51) among treatments after 14 d of aging. Bellies from CON pigs were more firm compared with bellies from PRRSV-CON and ISF pigs (P < 0.01). These data suggest PRRSV infection did not alter carcass characteristics but may have marginally reduced loin and belly quality. Supplementation with dietary soy isoflavones did nothing to mitigate the detrimental effects of PRRSV infection.

Growth performance, carcass characteristics, fresh belly quality, and commercial bacon slicing yields of growing-finishing pigs from sire lines intended for different industry applications

The objective was to control intrinsic and extrinsic factors associated with the production and slaughter of pigs to determine effects of sire line (Pietrain vs. Duroc ancestry) on growth performance, carcass and belly characteristics, and commercial bacon yields of growing-finishing pigs. There were no differences in growth performance (P ≥ 0.08) or belly processing characteristics (P ≥ 0.09). Pietrain sired pigs had a greater lean yield (P ≤ 0.01). Duroc sired pigs had darker, more highly marbled loins (P ≤ 0.04) and thicker bellies (P < 0.001). Bacon from Pietrain sired pigs had a greater (P = 0.04) lean to fat ratio with 1.58% increase (P = 0.04) in average bacon slice lean. Barrows had more highly marbled loins (P ≤ 0.01) and thicker bellies (P < 0.001) than gilts. Bacon from barrows had a greater slice area (P < 0.001) while bacon from gilts had a greater lean to fat ratio (P = 0.04).

Extending the interval between second vaccination and slaughter: I. Effects on growth, scrotal size and stress responses of immunocastrated ram lambs

Immunocastration provides a less invasive means of castrating lambs. Considering increasing consumer awareness, the efficacy of this technique on commercial slaughter lambs needs to be further investigated and its effects on growth and stress responses need to be established. This study compared the growth rate, testes size and stress responses of immunocastrated lambs with that of lambs physically castrated with a Burdizzo clamp, as well as intact rams. A total of 40 Dohne Merino ram lambs (average live weight = 45.4±3.68 kg) were randomly allocated to the following four treatment groups: control (intact; R), Burdizzo-castrated (on day 2; B), immunocastrated with a 4-week (ICS4), or a 6-week (ICS6) interval between the second immunocastration vaccination and slaughter. Within the immunocastration treatments, the reaction to vaccination was assessed through injection site scoring, recording the local injection site surface temperature and assigning a walking score. The response to Burdizzo castration was assessed by scoring the reaction during the procedure, testes palpation reaction, walking gait and measuring testis temperature. Additional parameters recorded included BW, serum cortisol concentration, scrotal circumference and rectal temperature. Pain behaviours were described for the short-, medium- and long-term effects after the two methods of castration. Predominantly, tissue-hardening and bruising occurred at the injection sites of immunocastrates, but little effect was observed on walking comfort and no effect on injection site temperature or rectal temperatures. After Burdizzo castration, lambs spent more time in abnormal postures, and from day 3 (D3) to D8 of the trial, discomfort was observed during testes palpation and walking in B lambs. Serum cortisol concentrations were elevated in B lambs on D3 and D15, indicating physiological stress. Thus, immunocastration improved the welfare of castrated lambs as assessed by cortisol secretion, scrotal swelling and pain behaviours, without influencing growth rate.

Zinc injection as a novel castration method in beef bulls: effects on performance, behavior, and testosterone and haptoglobin concentration

Crossbred beef bulls (n = 180) were blocked by initial BW (337 ± 10.9 kg; six blocks) and assigned randomly to one of three treatments on day 0: 1) INJ; received 1 mL (100 mg Zn) of a Zn solution in each testis, 2) BAN; received blood- restrictive rubber band placed around the dorsal aspect of the scrotum, 3) BUL; bulls with testicles remaining intact in a randomized complete block design (three treatment pens per block and 10 cattle per pen). A subset of 54 animals (n = 3 per pen) was fitted with accelerometers on day 0 to quantify behavior variables continuously for 28 d. Testis width and scrotal circumference, and serum haptoglobin (days 0, 1, 3, 5, 7, and 14) and testosterone concentrations (every 28 d until slaughter) were also determined for the subset. During the slaughter process, testes from INJ and BUL were collected to assess final testes weight and for histopathological evaluation. Data were analyzed using a mixed model (α = 0.05); pen served as the experimental unit for all dependent variables. Final BW was greater (P < 0.01) for INJ and BUL compared to BAN (672, 686, and 611 kg, respectively; SEM = 4.4). Overall ADG and G:F were greater (P ≤ 0.03) in INJ and BUL than BAN; whereas, DMI was similar between treatments for the study duration (P = 0.46). Histopathological evaluation (n = 13; INJ = 7; BUL = 6) indicated that INJ testes were degenerative and reproductively nonviable whereas BUL testes were normal. Serum testosterone concentrations on day 168 were similar (P = 0.14) between INJ and BUL whereas after day 14, BAN was nondetectable; however, initial serum testosterone concentrations were similarly low across treatments. Serum haptoglobin concentration was greater (P < 0.01) in INJ than BUL and BAN on days 1, 3, 5, and 7. Scrotal circumference (P = 0.08) and testis width (P = 0.07) on day 168 tended to be greater for BUL than INJ. Motion index (P ≤ 0.02) and step count (P = 0.04) was greater in BUL and INJ compared to BAN cattle during the 28 d monitoring period. No difference in standing time (P ≥ 0.85) or lying bouts (P = 0.35) occurred. Zinc injection resulted in sterilization but did not cause complete cessation of testicular function evidenced by testosterone concentrations more similar to BUL than BAN. This resulted in overall increased BW and G:F for INJ vs. BAN, yet the acute phase response was markedly greater directly after Zn injection. Collectively, Zn injection resulted in outcomes more similar to BUL than BAN, implying minimal efficacy of INJ as a castration method in older bulls arriving to the feedlot.

Influence of feeding thermally peroxidized soybean oil to finishing pigs on carcass characteristics, loin quality, and shelf life of loin chops

The objective of this study was to evaluate the effect of feeding soybean oil (SO) with varying levels of peroxidation on carcass traits and shelf life of loins. Fifty-six barrows were randomly assigned to 1 of 4 diets containing 10% fresh SO (22.5 °C) or thermally processed SO (45 °C for 288 h, 90 °C for 72 h, or 180 °C for 6 h), each infused with air at a rate of 15 liter/min. Individually housed pigs were provided ad libitum access to feed for 81 d. At 82 d, pigs were slaughtered and hot carcass weight and liver weights were recorded. Carcass characteristics and fresh loin quality were evaluated 1 d postmortem. Loin chops from each carcass were overwrap-packaged and subjected to a 10-d simulated retail display. Daily measurements of L*, a*, b*, reflectance, and visual discoloration were conducted, evaluation of cooking loss and Warner-Bratzler shear force (WBSF) was conducted on chops stored 0, 5, and 10 d, and thiobarbituric acid reactive substances (TBARS) were evaluated on chops stored 0 and 10 d. Shelf life-related data were analyzed as a completely randomized design with repeated measures in time, with storage location (shelf) as a random effect. Carcasses of 90 °C pigs weighed 6.0, 8.6, and 6.9 kg less (P < 0.03) than 22.5 °C, 45 °C, and 180 °C carcasses, respectively. Livers of 90 °C and 180 °C pigs were 14.3% and 11.7%, respectively, heavier (P ≤ 0.02) than those from pigs fed 22.5 °C SO, with livers of 45 °C being intermediate. Livers of 90 °C pigs represented 0.12 percentage units less (P = 0.02) of ending live weight than livers of 180 °C pigs, and 180 °C livers were 0.12 percentage units less (P < 0.01) of ending live weight than those from pigs fed 22.5 °C SO, with 45 °C being intermediate. There was no difference (P ≥ 0.19) in back fat depth, loin muscle area, or estimated carcass lean percentage among SO treatments, nor was there an effect (P ≥ 0.13) of SO on any early post-mortem loin quality traits or loin composition. There was no effect (P > 0.14) of SO on cooking loss, WBSF, L*, a*, b*, hue angle, reflectance, discoloration, or TBARS; however, there was a tendency (P = 0.09) for chops of 45 °C pigs to have greater (P < 0.04) chroma than either 22.5 °C or 180 °C, with 90 °C being intermediate. Overall, feeding SO cooked at 90 °C for 72 h resulted in reduced carcass weight and dressing percentage; however, there was no evidence that feeding peroxidized SO was detrimental to shelf life of loin chops.

Effects of full fat rice bran and defatted rice bran on growth performance and carcass characteristics of growing-finishing pigs

The objective was to test the hypothesis that increasing inclusion levels of full fat rice bran (FFRB) or defatted rice bran (DFRB) are not detrimental to growth or carcass characteristics, longissimus muscle (LM) quality, or fat quality when fed to growing-finishing pigs. A total of 224 barrows and gilts were randomly allotted to 7 treatments, with 4 pigs per pen and 8 pen replicates per treatment. Pigs had an average initial BW of 28.2 ± 4.1 kg and a 3-phase feeding program was used. A basal diet containing corn and soybean meal, 3 diets containing corn, soybean meal, and 10, 20, or 30% FFRB, and 3 diets containing corn, soybean meal, and 10, 20, or 30% DFRB were formulated within each phase. Daily feed allotments and pig BW at the start of the experiment and at the conclusion of each phase were recorded. On the last day of the experiment, 1 pig per pen was harvested and carcass characteristics, LM quality, and fat quality were determined. For the overall experimental period, no effects of dietary treatments were observed for average daily gain. However, average daily feed intake (ADFI) decreased (linear, P < 0.05) and gain to feed ratio (G:F) increased (linear, P < 0.05) for pigs fed diets with increasing concentrations of FFRB. In contrast, ADFI increased linearly (P < 0.05) and G:F decreased (linear, P < 0.05) as DFRB was included in the diets. There were no effects of dietary treatments on LM quality. The length of the bellies decreased (linear and quadratic, P < 0.05) as the inclusion of FFRB or DFRB increased in the diets. The concentration of crude fat in the adipose tissue of pigs increased linearly (P < 0.05) as the concentration of FFRB or DFRB increased in the diets. The concentration of saturated fatty acids in the adipose tissue of pigs fed diets containing FFRB decreased (linear, P < 0.05), whereas the concentration of polyunsaturated fatty acids (PUFA) increased (linear, P < 0.05). In contrast, addition of DFRB did not affect the concentration of fatty acids in adipose tissues. In conclusion, 30% FFRB included in diets for growing-finishing pigs may improve G:F without affecting carcass characteristics or LM quality with the exception that PUFA in adipose tissues will increase. However, inclusion of DFRB in diets for growing-finishing pigs will reduce G:F without affecting the LM quality or composition of adipose tissues.

Effects of pelleting diets without or with distillers' dried grains with solubles on growth performance, carcass characteristics, and gastrointestinal weights of growing-finishing barrows and gilts

Pigs (192 total) were blocked by age and stratified by initial BW (25.75 ± 2.29 kg) into pens (2 barrows and 2 gilts per pen). Within blocks, pens were randomly allotted to treatments in a 2 × 2 factorial arrangement, with 2 diet forms (meal vs. pellet) and 2 distillers' dried grains with solubles (DDGS) inclusion levels (0 vs. 30%). Pigs were weighed at the beginning of the experiment and at the end of each feeding phase (d 35, 70, and 91) and daily feed allotments were recorded. Pigs were slaughtered at the end of the 91-d experiment, and full gastrointestinal (GI) tract and GI tract component weights were recorded immediately following evisceration. Carcass characteristics and meat quality were determined after a 24-h chill. Overall ADG was increased ( < 0.01) 3.2% when pigs were fed pelleted diets rather than meal diets, but there was no effect ( = 0.46) of DDGS inclusion on overall ADG. Overall ADFI of meal-fed pigs fed 30% DDGS was 4.7% greater ( < 0.01) than that of pigs fed 0% DDGS in meal form, but overall ADFI did not differ ( ≥ 0.19) between DDGS inclusion level in pellet-fed pigs (diet form × DDGS inclusion, < 0.01). When fed meal diets, pigs fed 0% DDGS had 2.7% greater ( = 0.02) overall G:F than pigs fed 30% DDGS; however, there was no difference ( = 0.42) in overall G:F between DDGS inclusion levels in pigs fed pelleted diets (diet form × DDGS inclusion, < 0.03). Pigs fed pelleted diets had 2.9% heavier HCW ( = 0.01), 10.4% greater 10th-rib back fat ( = 0.01), and 1.8 percentage units less estimated lean percentage ( = 0.04) than meal-fed pigs. Full GI tracts of pigs fed pelleted diets were 0.33 percentage units less ( = 0.03) of the ending live weight than that of meal-fed pigs due to decreased ( < 0.01) GI tract contents. Inclusion of DDGS increased ( = 0.03) full GI tract weight, large intestine weight ( < 0.01), and GI tract contents ( = 0.02). Severity of parakeratosis of the pars esophagea was greater ( < 0.01) in pellet-fed pigs than in meal-fed pigs, but the magnitude of the difference was likely not great enough to negatively affect drop credit of stomachs. In conclusion, feeding pelleted diets improved growth performance and increased carcass weight and fatness without causing the development of gastric lesions that would reduce the value of the stomach to packers. Furthermore, inclusion of DDGS in diets reduced HCW and dressing percent and increased GI tract and GI tract contents weight but had no effect on gastric lesion development or LM quality.

Desempenho, características de carcaça e qualidade de carne de suínos sob castração cirúrgica ou imunológica

RESUMO Objetivou-se com o estudo avaliar o desempenho e as características quantitativas e qualitativas de carcaça de suínos machos castrados cirurgicamente e imunocastrados em terminação. Foram utilizados 32 animais obtidos do cruzamento entre Landrace e Large White com peso inicial médio de 92 kg, sendo 16 machos castrados cirurgicamente e 16 machos imunocastrados. Os animais foram distribuídos em delineamento de blocos casualizados, com dois tratamentos, machos castrados cirurgicamente ou machos imunocastrados, com oito repetições e dois animais por repetição. Não foi constatada diferença (P>0,05) no consumo de ração diário entre os animais castrados e imunocastrados. Entretanto, observou-se aumento (P=0,05) no ganho de peso diário dos machos imunocastrados em relação aos castrados cirurgicamente. Constatou-se ainda que suínos imunocastrados obtiveram uma espessura de toucinho inferior em relação aos suínos castrados cirurgicamente (P<0,05). A forma de castração não influenciou as demais características de carcaça. As características qualitativas não foram influenciadas (P>0,05) pelo método de castração. Conclui-se que a imunocastração aumenta o ganho de peso diário, reduz a espessura de toucinho e não afeta as características qualitativas de carcaças.

Growth responses of entire and immunocastrated male pigs to dietary protein with and without ractopamine hydrochloride

The interaction between dietary balanced protein, ractopamine (RAC) and Improvac (IMP) on the growth response of 120 individually penned male PIC© pigs was evaluated. The pigs entered the trial at 16 weeks of age and were assigned to 12 treatments using a 2×2×3 factorial design. Three balanced protein diets, formulated with standard illeal digestible lysine levels of 7.50 (low), 9.79 (medium) and 12.07 g/kg (high), were fed from 20 weeks. Improvac was administered at 16 and 20 weeks, the booster being given 4 weeks before slaughter. Ractopamine was supplemented at 10 mg/kg to the applicable treatments from 20 weeks. Live weight, backfat depth and food intake were measured on a weekly basis. Primary vaccination had no influence on the parameters measured. Immunocastration, RAC and higher protein diet treatments increased weight gain, but food intake was increased only with the use of IMP. Although weight gain increased in IMP-treated males, the increased feed intake resulted in their feed conversion efficiencies (FCE) being inferior to the intact controls. Feeding RAC only benefitted FCE when a high or medium protein diet was fed. Immunocastrates deposited more backfat after the booster vaccination than did entire males. Thus the cost of using RAC, IMP and of increasing dietary protein content needs to be weighed up against the additional revenue generated through the use of these interventions.

A summary review of carcass cutability data comparing primal value of immunologically and physically castrated barrows

The objectives were to 1) assess cutability, quality, and value of carcasses from immunologically castrated (IC) barrows compared with carcasses from physically castrated (PC) barrows and 2) evaluate the effect of hot carcass weight (HCW) on cutability and value of IC barrows summarizing U.S. data. Lean cutting yield (LCY) was defined as: LCY = [(whole ham + trimmed loin + Boston butt + picnic + spareribs)/chilled side wt] x 100. Carcass cutting yield (CCY) was determined using the following equation: CCY = [(lean cutting yield components + natural fall belly)/chilled side wt] x 100. To evaluate the effects of HCW of IC barrows on carcass cutting yields, IC barrows were grouped by HCW: light ( < 90.9 kg), average (90.9–97.7 kg), or heavy ( > 97.7 kg). Differences in the value of the carcass components for IC and PC barrow carcasses were calculated using a 5 yr average of meat prices from the USDA Agriculture Marketing Service and the carcass cutting yield estimates generated from this summary. Data were analyzed using the MIXED procedure of SAS with fixed effects of Improvest treatment or HCW group. Study was included as a random effect. This review allowed for a summarization of the treatment averages of 851 IC and PC barrow carcasses. Lean cutting yield of IC barrows was 1.41 units greater (P < 0.0001) than PC barrows (70.97 vs. 69.56%). Similarly, CCY of IC barrows was 1.29 units greater (P < 0.001) compared with PC barrows (87.27 vs. 85.98%). As HCW of IC barrows increased, both CCY and LCY declined (P < 0.01), with light IC barrow carcasses having a 1.43 unit advantage in CCY compared with heavy IC barrow carcasses (P < 0.01). Natural fall bellies of PC barrows comprised a greater (P < 0.05) percentage of side weight than those from IC barrows (15.81 vs. 15.50%). A reduction in belly primal value was confirmed by a 3.43 unit reduction in the commercial bacon slicing yields of IC barrows. However, belly yield and slicing yield differences were minimized when IC barrows were marketed at a heavier weight. Using carcass cutout estimates determined in the summary as the foundation for value calculations, lean cuts of IC barrow carcasses were worth $2.66 to $3.80 more than PC barrow carcasses. Therefore, after adjustment for the reduction in belly primal value, the primal value of an IC barrow carcass was $2.08 to $3.13 greater than a PC barrow carcass.

Color stability and sensory characteristics of fresh and enhanced pork loins from immunologically castrated barrows

Our objective was to evaluate color changes during storage of fresh pork chops and enhanced and nonenhanced loin quality from anti-gonadotropin-releasing factor (Improvest) immunologically castrated (IC) barrows. In study 1, treatments evaluated were IC barrows, IC barrows fed ractopamine (IC+RAC), physically castrated (PC) barrows, intact males (IM), and gilts. Fresh loins were evaluated for sensory characteristics and instrumental tenderness including both Warner-Bratzler Shear force (WBSF) and star probe force. In study 2, treatments evaluated were IC barrows fed 0.55% and 0.65% standard ileal digestible (SID) lysine and PC barrows fed 0.55% SID lysine. Loin chops were displayed for 7 d, and color was evaluated. The remaining loin was halved, and one half was enhanced with a 3.5% salt and phosphate solution. Enhanced loins were evaluated for sensory characteristics and instrumental tenderness. In both studies, pen served as the experimental unit for all traits measured. Data from individual animals were averaged by pen and analyzed, per study, as a 1-way ANOVA using the MIXED procedure of SAS. In study 1, there were no differences ( 0.05) between treatments for juiciness, tenderness, chewiness, or off-flavor. Intact males had the most intense ( 0.05) boar aroma. Gilts had the most intense ( < 0.05) pork flavor, whereas IM had the least intense pork flavor; all other treatments were intermediate. Tenderness (WBSF) was similar between treatments at 1 d of aging; however, at 7, 14, and 21 d of aging, loins from IC barrows were more tender ( 0.05) than those from gilts, IM, and IC+RAC but were similar ( 0.05) to those from PC. In study 2, discoloration of fresh loin chops during storage was similar ( 0.42) between PC and IC barrows. Chops from enhanced loins were more tender and juicy but had more off-flavor than nonenhanced loins ( 0.01). Star probe and WBSF were also reduced ( 0.01) in enhanced loins compared with nonenhanced loins. Sensory characteristics and tenderness were not different between treatments of IC and PC barrows ( > 0.05), and there were no interactions of enhancement with castration treatments. These data suggest that immunological castration does not negatively impact the color stability, sensory characteristics, or tenderness of enhanced or nonenhanced pork loins.

Ham and belly processing characteristics of immunological castrated barrows (Improvest) fed ractopamine hydrochloride (Paylean)

Effects of sex class (physically castrated, PC or immunologically castrated, IC) and diet (0 or 5mg/kg ractopamine hydrochloride, RAC) on characteristics of ham and bellies were determined from pigs slaughtered in three groups with similar ending live weights. One carcass per pen per marketing group (n=8) was selected to evaluate further processing characteristics. Data were analyzed as a 2×2 factorial design with a split plot in time and fixed effects of sex, diet, marketing group, and their interactions. IC fresh bellies were thinner (P<0.01) and softer (P<0.01) than PC bellies. IC hams and bellies were leaner (P<0.05) than those from PC pigs. RAC feeding did not affect (P>0.05) fresh ham or belly characteristics but decreased (P<0.01) fat in cured PC bellies. Marketing group affected (P<0.05) fresh quality, processing characteristics, and composition of hams and bellies. Immunological castration and RAC produced leaner finished products but did not alter processing yield of hams or bacon.

Lipid oxidation, sensory characteristics, and color of fresh pork sausage from immunologically castrated pigs stored frozen for up to 12 weeks

Two studies were conducted to evaluate the quality characteristics of fresh sausage manufactured from immunologically castrated (IC) pigs, an emerging technology in the pork industry. Study 1: Fresh sausage patties from ground Boston butts fabricated from PC (physically castrated) pigs fed 0.55% SID (standard illeal digestible) lysine, IC pigs fed 0.55% SID lysine, and IC pigs fed 0.65% SID lysine were made and not standardized to a similar content of fat content. Study 2: fat and lean trim obtained from IC and PC pigs was made into fresh sausage patties, targeting 25% lipid. Patties (1.25 cm) were placed on trays and assigned to 0, 4, or 12 weeks frozen storage and then, after frozen storage, placed in simulated retail display conditions for 5 days. Patties were evaluated for color stability, sensory and textural properties, and lipid oxidation. Data were analyzed as a one way ANOVA with repeated measures where appropriate. In both studies, sausage discolored with both increased time in frozen storage and with increased time in retail display (P < 0.01). However, within each week of frozen storage, all treatments were equally discolored in both studies. Treatment did not affect the sensory characteristics or textural properties of fresh sausage in either study. Lipid oxidation did not differ by treatment in study 1. In study 2, lipid oxidation was reduced (P < 0.05) in IC compared to PC by approximately 0.1 mg malonaldehyde/kg meat, but there were no differences within each storage week. Increasing frozen storage time increased lipid oxidation an off‐flavor scores in both studies (P < 0.05). Overall, immunological castration had no detrimental effects on color stability, sensory characteristics, or textural properties of fresh pork sausage.

Effects of time after a second dose of immunization against GnRF (Improvest) independent of age at slaughter on commercial bacon slicing characteristics of immunologically castrated barrows

The objective was to determine the effects of time after a second dose of anti-GnRF immunization on fresh belly characteristics and slicing yields of immunologically castrated (IC) barrows, physically castrated (PC) barrows and gilts slaughtered at 24 weeks of age. The second dose was staggered so that IC barrows were slaughtered at 4, 6, 8, or 10 weeks after the second dose. Fresh belly characteristics (N=141) were collected at slaughter and bacon was manufactured commercially. The main effects in the model were treatment and the random effects of block and block within replication. Thickness, flop distance, and lipid content increased (L; P<0.04) and iodine value tended to decrease (L; P=0.08) with time after the second dose in IC barrows. Slicing yields increased with time after the second dose (L; P<0.01), but were similar (P=0.11) among sexes. Increasing time of slaughter after second anti-GnRF dose improves fresh belly and bacon slicing characteristics in IC barrows.

Physical meat quality and chemical composition of the Longissimus thoracis of entire and immunocastrated pigs fed varying dietary protein levels with and without ractopamine hydrochloride

Physical and chemical attributes of the Longissimus thoracis (LT) of 96 PIC(©) entire (E) and immunocastrated (C) pigs were evaluated. The study followed a 2 × 2 × 3 factorial design where three diets of low, medium and high proteins (7.50, 9.79 and 12.07 g digestible lysine/kg) were fed either with (10mg/kg) or without ractopamine (RAC) for the last 28 days of growth. Vaccination of C occurred at 16 and 20 weeks and slaughtering at 24 weeks of age. The LTs were analysed for moisture, protein, fat and ash contents as well as CIE L*, a*, b* colour, drip loss, cooking loss and Warner-Bratzler shear force (WBSF). Various sex and protein interactions were observed for LT protein content, L* values and WBSF. Cooking loss was decreased in C and by the medium protein diet. Feeding RAC increased WBSF values, whilst decreasing a* and b* values. However, the differences observed are minor and might be considered negligible when evaluated by a consumer.

Influence of a gonadotropin-releasing hormone vaccine and dietary standardized ileal digestible lysine level on growth performance and carcass quality of grower-finisher pigs

The aim of this study was to assess the effect of standardized ileal digestible (SID) Lys levels of the diet on the growth performance, carcass characteristics, and meat quality of entire males (EM), surgical castrates (SC), and males vaccinated with a gonadotropin-releasing hormone (GnRH) vaccine (GV). In total, 252 crossbred pigs were fed 6 different experimental diets consisting of 3 sexes (EM, SC, and GV pigs) and 2 dietary SID Lys levels (2008 CVB standard SID Lys recommendation [Std] or 15% extra SID Lys [+15]) according to a 3-phase feeding scheme (d 0 to 35, 35 to 70, and 70 to 105 of experiment) with 6 pens per treatment and 6 pigs per pen. To determine if dietary SID Lys could be reduced for GV males after the second vaccination, an additional dietary treatment was included (GV+15-Std). The GV males on the GV+15-Std were fed the diet with 15% extra SID Lys in the starter and grower phases and the standard SID Lys level in the finisher phase. First vaccination was administered to pigs at the start of the experiment (23.4 kg BW and 63.6 d of age), and the second vaccination occurred 6 wk before slaughter (77.2 kg BW and 126.6 d of age). Until the second vaccination, GV pigs showed a lower (P ≤ 0.05) ADFI than SC but similar to EM. After the second vaccination, GV pigs had an intermediate (P ≤ 0.05) G:F between EM and SC. The GV+15 pigs showed a better G:F (P ≤ 0.05) than GV pigs fed the GV+15-Std diet in the finisher phase. No differences in the growth rate of the pigs were observed. The SC had a greater (P ≤ 0.05) carcass weight and dressing percentage than EM and GV pigs. The GV-Std pigs had a lower (P ≤ 0.05) meat percentage and greater (P ≤ 0.05) backfat thickness than the GV+15 pigs. The GV pigs and SC fed the standard SID Lys diet had a greater (P ≤ 0.05) percentage of SFA in the subcutaneous fat than EM+15 pigs. On the other hand, SC showed the greatest (P ≤ 0.05) concentration of MUFA compared to EM and GV pigs. The SC and GV pigs had a lower (P ≤ 0.05) PUFA percentage in the subcutaneous fat than EM fed the standard SID Lys diet.

Effects of feeding ractopamine hydrochloride (Paylean) to physical and immunological castrates (Improvest) in a commercial setting on carcass cutting yields and loin quality

Effects of feeding ractopamine (RAC; 5 mg/kg) to physically castrated (PC) and immunologically castrated (IC) pigs on carcass characteristics, cutting yields, and loin quality were evaluated using 285 carcasses. Male pigs were randomly assigned to sex treatments (PC and IC) at birth and fed the same nursery diets before allotment into 32 pens with 22 pigs per pen in a grow-finish barn. Pigs in the PC group were physically castrated at approximately 5 d of age, and pigs in the IC group were administered Improvest at 11 and 18 wk of age. Diet treatments (control or RAC) were initiated on study d 87. Pigs were marketed at 12 d (4.5 wk post-second Improvest dose), 19 d (5.5 wk post-second Improvest dose), and 33 d (7.5 wk post-second Improvest dose) following the start of final diet treatments. Three carcasses per pen were selected for evaluation of cutting yields and loin quality. Data were analyzed using PROC MIXED in SAS with fixed effects of sex, diet, market group, and their interaction; carcass (N = 285) was the experimental unit. Carcasses from RAC-fed pigs were heavier (P < 0.01) and had deeper (P = 0.02) loins than control-fed carcasses. Carcasses from IC pigs were similar (P = 0.22) in weight but had less (P < 0.01) fat and shallower (P = 0.02) loins when compared to PC carcasses. There were differences (P < 0.05) among market groups for carcass weights, fat depths, loin depths, and estimated carcass leanness. For cutting yields, RAC-fed carcasses had greater (P ≤ 0.03) bone-in lean and total carcass cutting yields than control-fed carcasses while there were no differences (P > 0.05) between RAC-fed and control-fed carcasses when evaluating LM color, marbling, firmness, pH, drip loss, and tenderness. Carcasses from IC pigs had greater (P < 0.05) boneless lean yields, bone-in lean yields, and total carcass cutting yields than PC carcasses. There were minimal differences (P < 0.05) in LM marbling, firmness, composition, and tenderness between PC and IC pigs. There was an interaction (P = 0.03) between sex and diet for LM composition. Control-fed PC loins had more (P < 0.01) lipid than all other treatment combinations. Market group had effects (P < 0.05) on carcass cutting yields, LM color, marbling and firmness scores, pH, purge loss, composition, and tenderness. The results from this study indicated RAC and immunological castration were additive in terms of improving carcass cutting yields while having minimal effects on pork quality.

Effects of feeding ractopamine hydrochloride (Paylean) to physical and immunological castrates (Improvest) in a commercial setting on growth performance and carcass characteristics

Growth performance and carcass characteristics of physically castrated (PC) and immunologically castrated (IC) pigs fed ractopamine hydrochloride (RAC; 5 mg/kg) were evaluated in 64 pens of 22 pigs each. Male pigs were randomly assigned to castration method at birth. Pigs in the PC group were physically castrated at 5 d of age while IC pigs were administered Improvest at 11 and 18 wk of age. Pigs entered the grow-finish barn at approximately 9 wk of age (d 0). Dietary treatments (control or RAC) were initiated on d 87. Final treatment arrangement was a 2 × 2 factorial of castration method and diet. Data were analyzed using a mixed model with fixed effects of castration method, diet, market group, and all 2- and 3-way interactions. Pen was the experimental unit. From d 0 to 65, IC pigs had 11.2% greater (P < 0.01) G:F and 11.6% less (P < 0.01) ADFI than PC pigs, but ADG was increased 1.0% in PC pigs compared with IC pigs (P < 0.01). From d 65 to 87, IC pigs had 7.9% greater (P < 0.01) ADG and 12.1% greater (P < 0.01) G:F than PC pigs while having similar (P = 0.16) ADFI. At the initiation of diet (RAC) treatments, BW of all treatments were similar (P ≥ 0.32). From d 87 to 120 (RAC feeding period), IC pigs had 10.0% greater (P < 0.01) ADG and 10.5% greater (P < 0.01) ADFI than PC pigs while having similar (P = 0.64) G:F. Feeding RAC increased (P < 0.01) ADG by 16.9% and G:F by 17.9% while having no effect (P = 0.42) on ADFI from d 87 to 120. There were no significant interactions between castration method and diet on growth performance from d 87 to 120. For the entire study (d 0-120), IC pigs had 2.6% greater (P < 0.01) ADG, 4.6% less (P < 0.01) ADFI, and 7.3% greater (P < 0.01) G:F than PC pigs. Averaged over market groups, IC pigs were 2.5 kg heavier (P < 0.01) and had similar (P = 0.10) carcass weights and 1.8 percentage units less (P < 0.01) dressing yields than PC pigs. Additionally, IC pigs had 1.3 mm less (P < 0.01) fat and 1.7 mm less (P < 0.01) loin depth than PC pigs. Pigs fed RAC were 2.9 kg heavier (P < 0.01) and had 2.3 kg heavier (P < 0.01) carcasses and 2.2 mm deeper (P < 0.01) loins but similar (P = 0.21) dressing yields and tended (P < 0.10) to have 0.4 mm less fat than control-fed pigs when averaged over market groups. Group 3 pigs were the heaviest (P < 0.01) at slaughter and had the heaviest (P < 0.01) carcasses, greatest (P < 0.01) dressing yields, and the most (P < 0.01) carcass fat of all market groups. Overall, immunological castration and RAC were additive in terms of improving growth performance and carcass characteristics.

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

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.