Behavior of immunologically castrated barrows in comparison to gilts, physically castrated barrows, and intact male pigs.

The behavior of immunologically castrated barrows (IC; with Improvest; Zoetis, Parsippany, NJ) was compared with that of intact males (IM), physically castrated barrows (PC), and gilts (G). The study used 160 commercial crossbred pigs in a randomized complete block design (blocking factor was start date of study) and was performed over an 8-wk period from 16 wk of age (67.2 ± 2.50 kg BW) to a final BW of 126.5 ± 6.05 kg. The first Improvest dose was given to IC at the start of the study (d 0), and the second dose was given 28 d later. Pigs were housed in single-gender groups of 4 and had ad libitum access to feed and water. General, aggressive, and sexual behaviors were observed over a 12-h period from 0600 to 1800 h by the same trained investigators on d -1 (d prior to first dose), 13, 27 (day prior to second dose), 34, 41, and 55 of study (end of test). General behaviors (number of pigs lying, sitting, standing, at feeder, and at drinker) were recorded every 10 min in all pens (10 pens/gender), and aggressive (bites, head butts, and fights) and sexual (mounts) behaviors were recorded continuously over the 12-h period on a subsample of 4 pens/gender. There was no difference ( > 0.05) between the genders for lying, sitting, or drinker-related behavior. For the 4-wk period prior to second dose, a greater percentage of PC and G were at the feeder ( < 0.05) than IC or IM (8.0%, 7.4%, 10.2%, and 9.3% for IC, IM, PC, and G, respectively; SEM = 0.44). However, after the second dose, the percentage of pigs at the feeder was similar ( > 0.05) for IC, PC, and G and was greater ( < 0.05) for those genders than IM (10.1%, 7.1%, 10.0%, and 8.8%, respectively; SEM = 0.50). Prior to the second dose, the incidence of aggressive behaviors was generally greater for IC and IM compared with PC and G; however, after the second dose, the incidence of aggressive behaviors was similar for IC and PC and lower ( < 0.05) for those genders than for IM. The frequency of mounts for IC was greater ( < 0.05) than for PC before (25.5, 27.3, 2.5, and 1.5 total mounts/pen, respectively; SEM = 4.37) but not after ( > 0.05; 3.3, 33.3, 0.25, and 0.25 total mounts/pen, respectively; SEM = 1.15) the second dose. These results suggest that prior to the second Improvest dose, the behavior of IC was similar to that of IM and transitioned to become more similar to the behavior of PC after the second dose.

Effects of ractopamine hydrochloride on the growth performance and carcass characteristics of heavy-weight finishing pigs sent for slaughter using a 3-phase marketing strategy.

A total of 2,158 crossbred pigs was used to evaluate the effects of feeding 7.4 mg/kg ractopamine hydrochloride (RAC) on the growth performance and carcass characteristics of heavy-weight finishing pigs sent to slaughter using a 3-phase marketing strategy. The study was performed from 121.0 ± 4.28 kg to 144.5 ± 4.73 BW using a randomized complete block design (blocking factor was d of start on test) with 2 treatments (0 vs. 7.4 mg/kg RAC). Pigs were housed in a commercial wean-to-finish facility in groups of approximately 25 (44 groups/treatment), with ad libitum access to feed and water throughout the study, and pen weights of pigs were recorded at the start (d 0), and on d 7, 21, and 35 of study. Pigs were sent for slaughter according to the following marketing strategy: 1) after 7 d on RAC, the heaviest 16% of each pen was sent for slaughter (Phase 1), 2) after 21 d on RAC, the next 40% of each pen was sent for slaughter (Phase 2), and 3) after 35 d on RAC, the remaining 44% of each pen was sent for slaughter (Phase 3). Pigs were selected for slaughter by visual appraisal and shipped to a commercial facility where standard carcass measurements (HCW, LM depth, and backfat depth) were measured. Overall, feeding RAC increased (P < 0.001) ADG (18.8%) and G:F (23.7%) compared to the control, but lowered (P < 0.001) ADFI (3.3%). In addition, feeding RAC increased (P < 0.001) HCW (3.9 kg), carcass yield (0.7% units), LM depth (5.0%), and predicted lean content (1.0% units), and reduced backfat depth (6.3% lower) compared to controls. With each subsequent phase of marketing, the magnitude of improvements in response to feeding RAC decreased for ADG (43.1, 20.9, and -3.1% for Phase 1, 2, and 3, respectively) and G:F (37.5, 25.8, and 6.4% for Phase 1, 2, and 3, respectively); however, improvements in HCW (1.6, 4.5, and 4.2 kg for Phase 1, 2, and 3, respectively), carcass yield (0.2, 0.6, and 0.9% units for Phase 1, 2, and 3, respectively), LM depth (2.3, 5.7, and 5.2% for Phase 1, 2, and 3, respectively), and predicted lean content (0.2, 1.0, and 1.3% units for Phase 1, 2, and 3, respectively) generally increased from feeding RAC. These results suggest that while improvements in growth performance from feeding RAC will generally decline after 21 d of feeding, improvements in carcass traits, particularly carcass yield and lean content, will continue with feeding RAC until d 35.

Effect of narasin (Skycis) or zinc bacitracin (Albac) inclusion on the growth performance and carcass characteristics of finishing pigs sent for slaughter using a 3-phase marketing strategy.

The objective of this study was to evaluate the effect of dietary inclusion of narasin or zinc bacitracin on the growth performance and carcass characteristics of finishing pigs sent for slaughter using a 3-phase marketing strategy. The study used 2,219 crossbred pigs in a randomized complete block design (blocking factor = start date) with 3 dietary treatments: 1) Control (no feed additive), 2) 15 mg/kg narasin (Skycis, Elanco Animal Health, Greenfield, IN), and 3) 28 mg/kg zinc bacitracin (Albac, Zoetis, Parsippany, NJ). Pigs were housed in single-sex pens of 25 pigs in a commercial wean-to-finish facility and there were 30 pen-replicates of each dietary treatment. All pigs were weighed as a group (i.e., pen) on d 0 (start of experimental feeding period), 77, 91, and 105 (end) of study. Pigs had ad libitum access to feed and water throughout the study period; all feed additions to the feeder were recorded. Pigs were sent for slaughter according to the following marketing strategy: 1) after 77 d on study, the heaviest 20% of each pen was sent for slaughter (Phase 1), 2) after 91 d on study, the next heaviest 48% of each pen were sent for slaughter (Phase 2), and 3) after 105 d on study, the remaining 32% of each pen was sent for slaughter (Phase 3). Pigs within each pen were selected for slaughter by visual appraisal of weight and shipped to a commercial slaughter facility where standard carcass measurements (HCW, LM depth, and backfat depth) were measured. Feeding narasin increased (P < 0.05) final live BW (1.3 kg) and overall ADG (1.1%) compared to the other treatments, which were similar (P > 0.05). Dietary treatment did not impact (P > 0.05) overall G:F. Feeding narasin increased (P < 0.05) HCW (1.4 kg) and carcass yield (0.3% units) compared to the other dietary treatments, which were similar (P > 0.05) for these traits. Overall, these results demonstrate that narasin-fed pigs had improved overall growth rate, HCW, and carcass yield compared to controls or pigs fed zinc bacitracin.

Impact of ractopamine hydrochloride on growth performance, carcass and pork quality characteristics, and responses to handling and transport in finishing pigs.

The effect of feeding ractopamine hydrochloride (RAC) on growth performance, carcass and pork quality, and blood acid-base and catecholamine responses to handling and transport in finishing pigs was evaluated using a randomized complete block design to compare 2 RAC levels (0 vs. 10 mg/kg). Crossbred pigs ( = 144) were housed in single-sex pens (barrow or gilt) of 3 with 24 pens/RAC level. The study was carried out for a 28-d period from 104.0 ± 5.99 to 136.7 ± 6.44 kg BW. At the end of the growth study, pigs were subjected to handling and transport procedures that involved an initial aggressive handling procedure (pigs moved 50 m with 8 shocks from an electric prod) followed by a 30-min transport on a standard livestock trailer at a floor space of 0.46 m/pig followed by a final gentle handling procedure (pigs moved 100 m using sort boards and slap paddles). A blood sample was taken and rectal temperature was measured 2 h before (baseline) and immediately after the final handling procedure (final). Barrows ( = 72) were harvested and carcass and pork quality were measured. Feeding RAC increased ( ≤ 0.05) ADG (19.6%), ADFI (4.2%), and G:F (14.8%). The increase in plasma epinephrine levels from baseline to final was greater ( ≤ 0.05) for pigs fed RAC; there was a trend ( ≤ 0.10) for pigs fed RAC to have greater final blood lactate and to show a greater change from baseline to final in blood bicarbonate, partial pressure of and total carbon dioxide, and oxygen saturation levels. However, there were no differences between treatments for changes from baseline to final in rectal temperature, blood pH and lactate, and plasma norepinephrine levels. The incidence of physical indicators of stress and of nonambulatory, noninjured pigs during the handling and transport procedures was similar for the 0 and 10 mg/kg RAC levels. Final farm BW was 4.1 kg heavier, carcass yield was 1.4 percentage units greater, and LM area was 5.18 cm greater for pigs fed RAC compared to the control ( ≤ 0.05). Minolta a* and b* values were lower ( ≤ 0.05) and ultimate pH (0.05 units) and Warner-Bratzler shear force (0.43 kg) were greater ( ≤ 0.05) for pigs fed 10 compared to 0 mg/kg RAC. These results confirm the substantial improvement from feeding 10 mg/kg RAC in growth performance and carcass yield and suggest relatively limited effects on pork quality and on responses to the handling and transport procedures used in this study.

Effect of feeding ractopamine hydrochloride on growth performance and responses to handling and transport in heavy-weight pigs.

The impact of feeding ractopamine hydrochloride (RAC) on growth performance and responses to handling and transport in heavy BW pigs was evaluated in a study performed as a split-plot design with a 3 × 3 factorial arrangement of treatments: 1) RAC level (0 vs. 5 vs. 7.5 mg/kg of feed) and 2) handling intensity (HI; gentle vs. moderate vs. aggressive); RAC level was the main plot and HI was the subplot. A total of 288 pigs housed in groups of 8 were used to evaluate growth performance over a 28-d RAC feeding period (98.5 ± 4.58 to 131.5 ± 7.45 kg BW). On d 29 of the study, the HI treatment was applied to 216 pigs (6/pen; 2/pen on each HI). This was followed by transportation for 1 h on a livestock trailer at the end of which pigs were subjected to a final handling procedure. Blood samples (to measure acid-base, cortisol, and catecholamine levels) were collected and rectal temperature was measured 2 h before the HI treatment (baseline) and after the final handling procedure (final). Feeding RAC (5 and 7.5 mg/kg) improved ( < 0.01) ADG (9.9 and 9.0% for 5 and 7.5 mg/kg RAC, respectively) and G:F (8.8 and 11.8%, respectively) compared to controls, with no differences ( > 0.05) between the 2 RAC levels. Increasing the intensity of handling decreased ( < 0.001) final blood pH, bicarbonate, and base excess and increased ( < 0.001) final blood lactate and plasma cortisol and norepinephrine levels. Aggressive compared to gentle handling increased ( < 0.05) the incidence of pigs exhibiting open-mouth breathing and skin discoloration after the final handling procedure but had no effect ( > 0.05) on the incidence on nonambulatory, noninjured pigs. There was no effect ( > 0.05) of feeding RAC on final rectal temperature or blood acid-base measurements. Feeding 7.5, but not 5, compared to 0 mg/kg RAC increased ( < 0.05) final plasma epinephrine levels and the incidence of nonambulatory, noninjured pigs. This study confirms the improved growth performance of pigs fed RAC and the negative effects of aggressive handling on physical, metabolic, and physiological responses of pigs. It also suggests that pigs fed 5 compared to 0 mg/kg RAC showed similar responses to transport and handling. However, pigs fed 7.5 mg/kg of RAC had a greater incidence of nonambulatory, noninjured pigs when subjected to the handling/transport model and this warrants further investigation.

Effects of ractopamine on growth performance and carcass characteristics of immunologically and physically castrated barrows and gilts.

The study was performed to evaluate the effect of feeding ractopamine (RAC) to physically castrated barrows (PC), immunologically castrated barrows (IC), and gilts (gilts) using a randomized complete block design with a 3 × 3 factorial arrangement of treatments: 1) sex (PC, IC, and gilts) and 2) RAC inclusion level (0, 5, and 7.5 mg/kg). The IC received 2 doses of gonadotropin releasing factor analog-diphtheria toxoid conjugate (Improvest; Zoetis, Kalamazoo, MI) at the start of the study (wk 16 of age; 69.6 ± 2.96 kg BW) and 4 wk later. The study used 180 pigs housed in groups of 4 (5 groups/sex × RAC subclass) and was performed over a fixed time of 61 d with RAC being fed for the final 26 d of study. Diets were formulated to meet requirements of intact males for the first 35 d and of intact males fed 7.5 mg/kg RAC for the remainder of the study. Pigs had ad libitum access to feed and water throughout the study period. At the end of the study, pigs were harvested at a commercial facility and HCW and last rib backfat thickness were measured. There were no treatment interactions (P > 0.05) for any variables. For the overall study period, IC had greater (P ≤ 0.05) overall ADG compared to PC, which grew faster (P ≤ 0.05) than gilts (1,246, 1,083, and 1,025 g/d for IC, PC, and gilts, respectively; SEM = 20.3); ADFI was lower (P ≤ 0.05) for gilts than IC and PC, which had similar ADFI (3.36, 3.37, and 2.87 kg/d, respectively; SEM = 0.051); and G:F was greater (P ≤ 0.05) for IC than gilts and greater for gilts than PC (0.371, 0.322, and 0.358 kg/kg, respectively; SEM = 0.0039). For the period from the second dose to the end of study, IC had greater (P ≤ 0.05) ADG (28.6%), ADFI (12.3%), and G:F (14.3%) than PC. Carcass yield was lower (P ≤ 0.05) for IC compared to PC and gilts (72.8, 75.0, and 74.6%, respectively; SEM = 0.25). Feeding RAC increased (P ≤ 0.05) ADG (15.7 and 14.5% for 5 and 7.5 mg/kg, respectively), G:F (17.1 and 16.4%, respectively), carcass weight (3.7 and 3.2 kg, respectively), and carcass yield (1.0 and 1.0 percentage unit, respectively) compared to the control. These results highlight sex differences in and effects of RAC on growth and carcass characteristics and suggest that the relative response to RAC is similar in IC and PC.

Effects of immunocastration and time after second Improvest dose on adipose tissue fatty acid profile of finishing barrows.

The effects of immunocastration and time after second Improvest dose on proximate composition and fatty acid profile of adipose tissue from jowl and belly of finishing barrows were determined. Physically castrated (PC) and immunologically castrated (IC) barrows were assigned to treatments at birth. Within 5 d of age, PC barrows were physically castrated and IC barrows were administered Improvest (gonadotropin-releasing factor analog; Zoetis, Kalamazoo, MI) at 16 and 20 wk of age. Diets were formulated with corn and soybean meal and did not contain ethanol coproducts. Subsequently, PC (n = 23) and IC (n = 24) barrows were slaughtered biweekly from 22 to 28 wk of age, 2 to 8 wk following second Improvest dose. Adipose tissue samples were collected from the jowl and belly. Main effects of castration method and time after second Improvest dose and their interaction were analyzed with the MIXED procedure of SAS. Overall, IC barrows were heavier at slaughter (136.1 vs. 100.6 kg; P < 0.01), had similar HCW (P = 0.13), and were leaner (50.9 vs. 48.9%; P < 0.01) than PC barrows. In jowl adipose tissue, IC barrows had less lipid content (64.7 vs. 80.2%; P < 0.01) than PC barrows at 2 wk. However, there were no differences (P ≥ 0.75) in lipid content between IC and PC barrows from 4 to 8 wk. Total MUFA content was reduced (42.5 vs. 44.8%; P = 0.04) and PUFA content was greater (16.9 vs. 14.8%; P < 0.01) in IC compared to PC barrows. Increasing time after second dose reduced (P = 0.04) PUFA content from 17.5% at 2 wk to 15.4% at 8 wk. In IC barrows, iodine value (IV) was increased by 6.9 and 3.3 g/100 g compared with PC barrows at 2 and 4 wk, but IV was not different between castration methods (P ≥ 0.95) at both 6 and 8 wk. Meanwhile, in belly adipose tissue, IC barrows had less lipid content than PC barrows (75.3 vs. 82.7%; P < 0.01). Lipid content was unchanged over time (P = 0.34) in either PC or IC barrows. Total SFA and MUFA content of the belly were similar for both IC and PC barrows. Belly adipose tissue from IC barrows had greater concentrations of PUFA than PC barrows (16.2 vs. 14.7%; P < 0.01). In IC barrows, IV was increased by 5.3 g/100 g compared with PC barrows at 2 wk, but IV was not different between castration methods (P ≥ 0.91) from 4 to 8 wk. Results indicate that as time after second Improvest dose progressed, IV of jowl and belly was reduced. This was accompanied by an increase in lipid deposition in jowl, while lipid content remained constant in belly.

Growth performance of immunologically castrated (with Improvest) barrows (with or without ractopamine) compared to gilt, physically castrated barrow, and intact male pigs.

The study used a randomized complete block design (blocking factor was date of start on test) with 5 treatments: 1) physically castrated barrows (PC), 2) intact males (IM), 3) gilts (G), 4) immunologically castrated barrows (IC), and 5) immunologically castrated barrows fed ractopamine at 5 mg/kg (IC+RAC). The study used 192 pigs and was performed from the 16 wk of age (67.2 ± 2.52 kg BW) to a pen mean BW of 132.5 ± 3.60 kg. For IC+RAC, ractopamine was fed for the final 23 d of the study. Pigs were housed in groups of 4 (10 groups for PC, IM, G, and IC and 8 groups for IC+RAC) in a finishing building at a floor space of 1.18 m(2)/pig. Diets were formulated to meet requirements of IM except that the diet for the IC+RAC fed during the ractopamine feeding period was formulated to meet requirements of pigs on that treatment. Pigs had ad libitum access to feed and water throughout the study period and were individually weighed at the start, wk 2 and 4, and subsequently every week until the end of study. For the overall study period, IC had greater (P ≤ 0.05) ADG than the other genders (1,150, 1,024, 1,064, and 954 g/d for IC, PC, IM, and G, respectively; SEM = 25.8) and required fewer days to reach slaughter weight than the other genders (58.1, 61.6, 61.6, and 66.5 d for IC, PC, IM, and G, respectively; SEM = 1.26). Overall ADFI was less (P ≤ 0.05) for IM and G than IC and PC, which were similar (P > 0.05) in this respect (3.11, 3.06, 2.68, and 2.75 kg/d for IC, PC, IM, and G, respectively; SEM = 0.061). Overall G:F was greater (P ≤ 0.05) for IM than the other genders; IC had greater overall G:F than PC and G, which were similar in this respect (0.371, 0.335, 0.397, and 0.347 kg/kg for IC, PC, IM, and G, respectively; SEM = 0.0068). Immunologically castrated barrows had greater (P ≤ 0.05) ADG (30.7%) and ADFI (22.5%) than PC from the second week following the second Improvest dose to the end of the study. During the ractopamine feeding period, IC+RAC had greater (P ≤ 0.05) ADG (11.6%) and G:F (17.3%) than IC. The results of this study confirmed previously observed gender differences and effects of ractopamine on growth performance and that IC grew faster and had greater feed efficiency than PC during the study period.

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.

Effect of distillers dried grains with solubles and ractopamine (Paylean) on quality and shelf-life of fresh pork and bacon.

Pigs (n = 240) were allotted in a 5 x 2 factorial arrangement with 5 levels of distillers dried grains with solubles (DDGS): 0, 15, 30, 45, and 60%, and 2 ractopamine (RAC) levels: 0 and 5 mg/kg. Four pigs per pen (2 barrows, 2 gilts) closest to pen mean BW were used for meat quality evaluation. Loins (n = 119) were evaluated for objective color; moisture and fat; subjective color, marbling, and firmness; and drip loss. Bellies (n = 119) were evaluated for weight, length, width, thickness, objective fat color, and firmness. Cured bellies were evaluated for pump yield, cook loss, and sliced bacon cook loss. Loin thiobarbituric acid reactive substances (TBARS) were evaluated on enhanced (salt and phosphate) boneless chops held in modified atmosphere (80% O(2)/20% CO(2)) packages for 0, 7, 14, and 21 d. Bacon TBARS were evaluated on sliced bacon held in vacuum packages for 0, 28, 56, and 84 d. Fat samples were collected from each jowl and belly and evaluated for fatty acid profile and iodine value (IV). Increasing DDGS decreased subjective marbling (P = 0.0134) and firmness (P = 0.0235), and increased drip loss (P = 0.0046). Distillers dried grains with solubles did not affect loin pH, subjective or objective color, percent moisture, or percent fat (P > 0.05). The RAC decreased subjective color (P = 0.0239), marbling (P = 0.0445), and a* (P = 0.0355). Increasing DDGS decreased belly weight (P = 0.0155), length (P = 0.0008), thickness (P = 0.0019), and firmness (P = 0.0054); decreased belly fat L* (P = 0.0818); and increased belly cook loss (P = 0.0890). Ractopamine did not affect any belly measurements, and there were no DDGS x RAC interactions (P > 0.05). Distillers dried grains with solubles did not affect loin TBARS at 0, 7, or 14 d. At 21 d, loin TBARS from 30, 45, and 60% DDGS groups were increased compared with 0 and 15% groups (P < 0.05). Ractopamine did not affect (P > 0.05) loin TBARS, and there were no (P > 0.05) DDGS x RAC interactions. Distillers dried grains with solubles and RAC did not affect bacon TBARS (P > 0.05). Increasing DDGS increased belly (P = 0.0207) and jowl (P < 0.0001) IV, and decreased MUFA:PUFA in belly (P < 0.0001) and jowl (P < 0.0001) fat. Ratio of SFA:unsaturated fatty acids decreased in jowl (P = 0.0002) and belly fat (P = 0.2815). Ractopamine did not affect fatty acid profiles or IV, and there were no DDGS x RAC interactions (P > 0.05). Results indicate that increased DDGS have minimal effects on loin quality, but decrease belly quality, bacon processing characteristics, and fat stability. Ractopamine does not negatively affect these characteristics and does not interact with DDGS.