The effect of timing of Improvest administration on growth performance and carcass characteristics in gilts

Improvest (IMP; Zoetis Inc., Parsippany, NJ) has been approved by the U.S. Food and Drug Administration for use in gilts. Improvest is administered twice: the first dose should be administered no earlier than 9 wk of age and the second dose (D2) at least 4 wk after the first dose. The aim of this study was to determine how the timing of IMP before harvest affects growth performance and carcass characteristics in gilts. A total of 1,632 gilts were allocated to four groups (12 pens/treatment; 34 gilts/pen): 1) a control group did not receive IMP; 2) T-early gilts received IMP on day 7 (day 0 = 10 wk postweaning), and D2 on day 40 (i.e., 35 d prior to first removal for harvest); 3) T-medium gilts received IMP on day 21 and D2 on day 56 (i.e., 19 d prior to first removal for harvest); 4) T-late gilts received IMP on day 35 and D2 on day 70 (i.e., 5 d before first removal for harvest). Pigs were selected for harvest by visual observation on days 75, 89, 103, and 117: 1) the heaviest 7 gilts/pen for each treatment on day 75; 2) the heaviest 10 gilts/pen of each treatment at day 89; 3) the heaviest 10 gilts/pen of each treatment on day 103; and 4) the remaining 7 gilts/pen on day 117. Weights and feed disappearance were recorded every 2 wk and during harvest dates to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (Gain:Feed; G:F). Generalized linear mixed models of SAS were used to analyze all variables. The increase in ADFI over Control gilts was observed 15 d post D2 and continued through 77 d post D2, with advantages in ADG occurring between 15 and 35 d post D2. Control and IMP treated gilts had similar G:F 15 to 33 d post D2. The overall ADG and ADFI from day 0 to market, final live weights, and hot carcass weights were significantly greater (P ≤ 0.05) in IMP gilts compared to Control. When G:F based on live weight was averaged across all groups (i.e., from day 0 to market), T-early had the lowest (P ≤ 0.05) G:F compared to Control, T-medium, and T-late gilts, which did not differ. Carcasses from IMP gilts had increased (P < 0.01) backfat, but similar (P = 0.5) Longissimus muscle depth, compared to Control. Within a cohort of similar aged gilts finishing during the summer, this study indicates that the trajectory of growth is enhanced within a similar window post D2 of IMP. Gilts treated with IMP had heavier carcasses with increased backfat and similar Longissimus muscle depth.

Relationship between energy intake and growth performance and body composition in pigs selected for low backfat thickness

Genetic selection of pigs over recent decades has sought to reduce carcass fat content to meet consumer demands for lean meat in many countries (e.g.: Australia). Due to the impacts of genetic changes, it is unknown whether the carcass fat measures are still responsive to energy intake. Thus, the present experiment aimed to quantify the relationship between tissue composition and dietary energy intake in finisher pigs selected for low carcass backfat. Intact male and female pigs (n=56 for each sex; PrimegroGenetics, Corowa, NSW, Australia) were fed seven different amounts of an amino acid adequate wheat-based diet containing 14.3 MJ digestible energy (DE)/kg to provide the following daily DE intakes- 25.8, 29.0, 32.6, 35.3, 38.5, 41.5 and 44.2 (ad libitum) MJ DE/d for males, and 25.8, 28.9, 32.0, 35.6, 38.3, 40.9 and 44.5 (ad libitum) MJ DE/d for females between 60 kg and 108 kg live weight. Body composition of anaesthetised pigs was measured using the Dual Energy X-ray Absorptiometry (DXA) method when individual pigs reached 108 kg, and protein, fat and ash deposition rates were calculated. Pigs were slaughtered on the 2nd day post-DXA scan for carcass backfat measurement. The results showed that the carcass backfat thickness (standardized at 83.7 kg carcass) increased by 0.125 mm for every MJ increase in daily DE intake in male pigs (P = 0.004; R2 = 0.130), but carcass backfat of female pigs (standardized at 85.1 kg carcass) was not responsive to daily DE intake. Whole-body fat composition and fat deposition rate increased linearly (both P < 0.01) in male pigs but quadratically (both P < 0.01) in female pigs in response to DE intake. Every MJ increase of daily DE intake increased the rate of daily protein deposition by 3.8 g in intact male pigs (P < 0.001; R2 = 0.781) and by 2.5 g in female pigs (P < 0.001; R2 = 0.643). In conclusion, the selection for low backfat thickness over the last two decades has altered the response of fat deposition and backfat thickness to energy intake, particularly in female pigs. Despite this change, the linear relationship between DE intake and protein deposition rate was maintained in these modern genetics.

Immunization against gonadotropin-releasing factor (GnRF) in market gilts: Effect on growth and carcass parameters, and impact of immunization timing

Reproductive cycling in fattening gilts can be associated with undesirable effects, such as estrus-related aggressive behavior, reduced feed intake and, in production systems where gilts are co-housed with entire males, unwanted pregnancy. Immunization against Gonadotrophin Releasing Factor (IM) can temporarily suppress ovarian activity, including related negative consequences on animal welfare and productivity. Feed intake has been shown to be higher after IM, resulting in both increased growth and increased carcass fat. A series of studies was conducted to confirm these effects on production and look at their dynamics over time. Three trials were performed to a similar design, each involving 240 gilts divided into 4 experimental groups at 12 weeks of age. One group remained untreated while the others had the two dose, IM course completed 8, 6 or 4 weeks before harvest, which was on a single day at 24, 25 or 26 weeks of age depending on the study. Feed intake was measured daily and bodyweight weekly, allowing growth parameters to be calculated on a weekly basis and for specific longer periods. Carcass weight, backfat depth and lean meat percentage were recorded at harvest. No effects were observed before the second application of the immunological product (V2) and completion of the IM course. Starting in the second week after V2 all IM groups showed a marked and consistent increase in Average Daily Feed Intake (ADFI), typically peaking at over 120% of the control group 3 to 4 weeks after V2 and then slowly declining, but still remaining elevated at 8 weeks. Weekly Average Daily Gain (ADG) showed a similar pattern but with a faster decline, resulting in the initially favorable impact on feed efficiency becoming less favorable as the V2 to harvest interval (V2H) progressed. Carcass weights were higher in IM gilts and backfat depths were greater, with the effects increasing with increasing V2H. Correspondingly, carcass lean meat percentage tended to decrease, although the higher carcass weights meant that the absolute weight of lean meat remained similar or higher. Carcass yield was generally unaffected by IM, but some between-group differences were statistically significant, and it is possible that different factors predominated at different times after V2, creating a complex relationship with V2H duration. The optimum IM protocol will depend on local conditions and production objectives but, as a generalization and assuming ad libitum feeding, a shorter V2H will favor efficient growth, while a longer duration will maximize carcass changes, such as increased fat coverage. It is suggested that the growth performance changes seen after IM in gilts might be viewed as a process of adjustment to a heavier and fatter target body type.

Effects of pig genotype, immunological castration, and use of ractopamine on growth performance, carcass traits, and pork quality for entire male pigs

Entire male (EM) pigs (152; ∼30 kg body weight) were used to examine immunocastration using Improvest and feeding ractopamine on growth performance, carcass and meat quality, and fatty acid composition. Timing for administering second dose of Improvest compared dosing at 4 and 8 wk pre-slaughter. A factorial arrangement evaluated two genotypes [Large Whites and Duroc crossbreds (Durocs)] by five management regimens (EM fed control diet, EM fed ractopamine, second dose Improvest 4 wk pre-slaughter, second dose Improvest 8 wk pre-slaughter, second dose Improvest 4 wk pre-slaughter plus ractopamine). Average daily gain and gain to feed (G:F) were generally greater (P ≤ 0.01) in Durocs. Immunocastration increased (P < 0.01) dry matter intake (DMI); feeding ractopamine decreased (P < 0.02) DMI and increased (P < 0.03) G:F. Immunocastration decreased (P < 0.04) carcass and lean yields; feeding ractopamine increased (P < 0.04) carcass weights, lean yield, muscling, and longissimus shear force while decreasing (P < 0.01) backfats. Immunocastration did not affect loin pH, color, drip loss, and shear force. Timing for second Improvest dose did not affect most growth performance, carcass, and meat quality traits except for greater (P < 0.02) backfats when administering dose 8 wk pre-slaughter. Effects of immunocastration and (or) feeding ractopamine were relatively consistent in both genotypes evaluated.

Effect of immunocastration on growth performance, gonadal development and carcass and meat quality of SuHuai female pigs

The present study was aimed to compare growth performance, gonadal development, carcass characteristic and meat quality among SuHuai entire, immunocastrated and surgically castrated female pigs. Eighty 12-week-old SuHuai gilts were randomly assigned to the following four treatment groups with four pigs per pen and five replicate pens per treatment: control (PBS injection), two-dose Improvac regimen (V2), three-dose Improvac regimen (V3) and surgical castration (S). All pigs had ad libitum access to standard diets and water. The performance and occurrence of oestrus were recorded in the trial. Backfat thickness and loin eye muscle area were recorded ultrasonically. The pigs were slaughtered to measure the weight and size of the uterus, and the weight and activity of the ovaries, to determine the serum concentrations of progesterone, and to evaluate the quality of carcass and meat. There were no significant differences in growth performance among the four groups, except for the V2, which had a better average daily feed intake (P &lt; 0.05). Carcass and meat quality were comparable among the four groups; however, the intramuscular fat in control was higher than the V2 and V3 (P &lt; 0.01). Mean ovary and uterus weights and oestrus of female pigs in V2 and V3 were significantly (P &lt; 0.01) lower than in control, but the difference between the V2 and V3 was not significant. The concentration of progesterone in the control was significantly higher than that in the V2, V3 and S (P &lt; 0.05). These results indicated that immunocastration successfully suppressed gonadal development and had no adverse effects on growth performance, or carcass or meat-quality traits in Chinese SuHuai female pigs.

Effect of feed restriction and initial body weight on growth performance, body composition, and hormones in male pigs immunized against gonadotropin-releasing factor

Pigs immunized against gonadotropin-releasing factor (GnRF) have increased carcass fatness compared to entire males; however, the timing of this increase in fatness after the second immunization against GnRF has not been determined. An experiment was conducted to identify and compare the growth performance, body composition, and physiological changes in immunocastrated males (IC males) at different BW and feeding levels. A total of 64 pigs were used in a 2 × 2 × 2 factorial experiment with the treatments being 1) sex (entire males or IC males), 2) initial BW (45.9 kg [light] or 78.3 kg [heavy]), and 3) feeding regime (2.5 times maintenance [restricted] or ad libitum). The pigs were individually housed, and the diets were fed for 4 wk after the second immunization against GnRF until slaughter at either 68.4 kg BW (light) or 105.8 kg BW (heavy). Immunocastrated males on a restricted feed intake had a lower ADG compared to entire males from d 15 to 28 and d 0 to 28 ( 0.011 and 0.011, respectively). Fat deposition was not affected by sex from d 0 to 14, but from d 15 to 28 IC males deposited 45 g/d more fat than entire males ( = 0.025). Immunocastrated male pigs fed ad libitum deposited 87 g/d more fat from d 15 to 28 than entire males fed ad libitum ( = 0.036). However, there was no difference in fat deposition between IC males and entire males when feed intake was restricted from d 15 to 28. Plasma urea nitrogen levels were greater in IC males compared to entire males from d 7 after the second immunization against GnRF ( 0.05 for d 7, 10, 14, 21, and 28). Plasma concentrations of IGF-1 were lower for IC males compared to entire males on d 3, 7, 10, and 28 ( 0.05 for all days). The following conclusions were made: 1) when pigs are immunized at a light BW (50 kg) and/or are on a restricted feed intake, they have a reduced propensity to deposit fat; however, the restriction in feed intake adversely affects growth rate. 2) The majority of fat deposition for males immunized at heavy BW (80 kg) occurs from d 15 to 28 after the second immunization against GnRF.

The Effect of Lupinus albus and Calcium Chloride on Growth Performance, Body Composition, Plasma Biochemistry and Meat Quality of Male Pigs Immunized Against Gonadotrophin Releasing Factor

Simple Summary

Pigs immunized against gonadotrophin releasing factor (immunocastrated (IC) males) have an increased feed intake, growth rate, back fat and fat deposition compared to entire males. It is desirable to develop management strategies to limit the increase in feed intake and fat deposition in IC males. This experiment used in-feed ingredients (Lupinus albus (albus lupins) or a combination of calcium chloride and sodium tri-polyphosphate (mineral salts)) to try to suppress the voluntary feed intake of IC male pigs and subsequently fat deposition. Mineral salts decreased feed intake with no effect on fat deposition while albus lupins reduced both feed intake and fat deposition in pigs.

Abstract

Two hundred and ninety-four pigs were used to assess the effect of two ingredients (Lupinus albus (albus lupins) or a combination of calcium chloride and sodium tri-polyphosphate (mineral salts)) on growth performance, body composition and objective meat quality of pigs immunized against gonadotrophin releasing factor (immunocastrates) and entire male pigs in the late finishing phase. Pigs fed mineral salts ate less feed than those fed the control diet with no effect on growth rate (p > 0.05), backfat (p > 0.05) or fat deposition (p > 0.05). Pigs fed albus lupins had a reduced feed intake (p < 0.001 for all time periods), lower growth rate (p < 0.001 for all time periods), lower backfat (p < 0.005) and decreased fat deposition (p < 0.001 for all time periods) compared to those fed the control diet or mineral salts. From day (d) 0–28 pigs fed mineral salts had a better feed conversion ratio (p = 0.001) than those fed albus lupins who in turn had an improved feed conversion compared to the control diet. Immunocastrates had thicker backfat than entire males at the end of the experiment (p < 0.001), however, feeding albus lupins to immunocastrated males reduced backfat thickness to similar to entire males fed the control diet (p = 0.01). With the exception of the increased muscle pH at 45 min post-exsanguination in mineral salts and albus lupins compared with the control diet (p = 0.03) there was no effect of diet on objective pork quality. Pork from IC males had a higher ultimate pH (p < 0.001), was lighter (L*; p = 0.003), more yellow (p = 0.008) and had a higher drip loss (p < 0.001) compared to entire males. Albus lupins show potential in reducing the increase in feed intake and backfat associated with immunocastration. Mineral salts may be useful in situations where a reduction in feed intake and an improvement in feed conversion is desired and reducing fat deposition is not the objective.

Carcass characteristics and qualitative attributes of pork from immunocastrated animals

An investigation was carried out to assess the carcass characteristics and meat quality aspects of immunocastrated male pigs of medium genetic potential for lean meat deposition in carcass (53 to 55%). When the crossbred Large White x Landrace pigs (n = 45) were 70 days old, they were distributed in a totally randomized design in three treatments (castrated males, females and immunocastrated males) with three replicates of five animals. The pigs were slaughtered when they were 140 days old. Carcass temperature and pH were recorded twice, at 45 min and 24 h after slaughter. The carcasses were evaluated for hot and cold carcass yield, commercial cuts yield, length and depth, back fat thickness, loin eye area and lean meat percentage. The Longissimus dorsi muscle was extracted for analysis of color (L*, a*, b*), exudate loss, cooking loss and centesimal and sensorial analysis of the meat. There were no significant differences for the evaluated parameters between castrated males, immunocastrated males and females, except for backfat thickness between the 7th and 8th thoracic vertebra and the point P2 (lower for immunocastrated males) and carcass temperature at 45 min post slaughter (higher in immunocastrated males), however, this did not interfer with the rate of pH decrease post mortem and the meat quality. The results from this research did not indicate a benefit of immunocastration on carcass characteristics of pigs of medium genetic potential for lean meat deposition in carcass, when compared to surgical castration.

Meta-analysis of the effect of immunocastration on production performance, reproductive organs and boar taint compounds in pigs

Meta-analytical approach was used to quantitatively synthesize the effect of immunocastration on growth, carcass, meat quality, reproductive organs and boar taint compounds. Altogether, 41 papers were collected for effect size (θ) calculation and the comparisons were made with entire males (EM) and surgical castrates (SC). The data for reproductive organs and growth performance are numerous enough to draw firm conclusions. In contrast, data for carcass and meat quality are more limited. Results of meta-analysis show efficient immunocastration with the magnitude of the response being by far the largest for reproductive organs (θ = -2.8 to -5.0) and boar taint substances (θ = -2.8 and -0.8 for androstenone and skatole, respectively). However, compared with SC, the immunocastrates exhibit larger bulbourethral glands (θ = 1.3) and slightly higher concentrations of androstenone and skatole (θ = 0.1 and θ = 0.2, respectively). The impact of immunocastration is also remarkable on performance, where the main advantage of the immunocastrates is their boar-like performance until revaccination. In the period following the second vaccination, they eat much more than EM (θ = 2.1), resulting in large effect size for growth rate compared with both EM and SC (θ = 1.1 and θ = 1.4, respectively). Considering the whole fattening period, their feed conversion ratio is higher compared with EM (θ = 0.6) and much lower than that of SC (θ = -1.3), although exhibiting moderately faster growth compared with both (θ = 0.6 and θ = 0.2, respectively). With regard to carcass quality, the immunocastrates take intermediate position between EM and SC. Besides, our analysis suggests no difference in meat quality with SC and some meat quality advantages of immunocastrates over EM because of higher intramuscular fat content (θ = 0.4) and lower shear force (θ = -0.6).

Reducing the length of time between slaughter and the secondary gonadotropin-releasing factor immunization improves growth performance and clears boar taint compounds in male finishing pigs

The objective of this study was to evaluate whether altering the timing of the secondary anti-gonadotropin-releasing factor (GnRF) immunization closer to slaughter in male finishing pigs would reduce the increase in P2 fat depth (6.5 cm from the midline over the last rib), while still limiting the incidence of boar taint. Entire male pigs are immunized against GnRF to reduce the concentration of testicular steroids that in turn limits the incidence of boar taint. Additionally, testicle measurements and color measurements were taken to examine whether they could be used to differentiate nonimmunized entire males from immunized male pigs. A total of 175 Large White × Landrace entire male pigs aged 16 wk (59 kg of BW) were used in a completely randomized design with 5 treatment groups based on the time that pigs received the secondary immunization before slaughter. Pigs were housed in groups of 7 and randomly allocated to 1 of 5 treatments with 5 replicates per treatment. The treatment groups were as follows: no secondary immunization before slaughter, and the secondary immunization given at 2, 3, 4, or 6 wk before slaughter. The P2 fat depth levels were reduced (P = 0.054) with the secondary immunization closer to slaughter (11.7, 11.3, 12.8, 12.6, and 13.7 mm for no secondary immunization, secondary immunization at 2, 3, 4, and 6 wk before slaughter, respectively). Androstenone concentration did not exceed the generally accepted industry sensory threshold of 1.0 µg/g of fat, and both androstenone concentration in the adipose tissue and testosterone concentrations in the blood were suppressed (P < 0.001) in all immunized pigs regardless of timing of the secondary immunization compared with pigs that did not receive the secondary immunization. Skatole concentration of all pigs in the experiment did not exceed the generally accepted industry sensory threshold of 0.2 µg/g. Testes weight was reduced (P < 0.001) with increased time between slaughter and the secondary immunization. Immunized pigs, regardless of time before slaughter, had greater L* (lightness) and b* (yellowness) color of the testicle surface (P < 0.001 and P = 0.020, respectively), and less a* (redness) color compared with entire males (P < 0.001). The study provides further evidence of the efficacy of the anti-GnRF immunization and indicates that the secondary immunization can be moved closer to slaughter, while still limiting the incidence of boar taint. Testicle measurements and color measurements together could provide a method of discrimination between carcasses from immunized entire males clear of boar taint and tainted carcasses.

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

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would increase percentage fat free lean and carcass cutting yields when compared with physical castrates. The anti-gonadotropin-releasing factor (GnRF) immunological product (Improvest, Pfizer Animal Health) is used worldwide to immunologically castrate entire male pigs to control boar taint and take advantage of the inherent ability of the entire male to deposit more muscle, less fat, and grow more efficiently than physically castrated males. The immunization process essentially allows the pig to grow as an entire male pig for most of its life and then removes any boar odor (boar taint) before slaughter. Reported lean meat advantages may also provide economic benefits to the domestic meat industry. Approximately 1,200 male pigs [physical castrates, IC males, and entire males] were each assigned to 1 of 4 diet programs which differed in lysine content. In each case, lysine was fed in a conventional step-down program that culminated with the following concentrations in the late finishing diet: physical castrates fed low lysine (0.7%), IC fed low lysine (0.7%), IC fed low/medium lysine (0.8%), IC fed medium/high lysine (0.9%), IC fed high lysine (1.0%), and entire males fed high lysine (1.0%). At 25 wk of age (5 wk post-second injection), pigs were individually weighed and the 2 pigs (n=96) in each pen closest to the median pig BW were selected and slaughtered. The right side of each carcass was dissected into soft tissue, skin, and bone. Proximate composition was determined on the soft tissue to determine percentage fat-free lean. The left side of each carcass was weighed and initially fabricated into ham, loin, belly, and whole shoulder. Each primal piece was weighed again and further fabricated into respective subprimal cuts. Immunological castration did not change (P>0.05) shear force values or ultimate pH when compared with either physical castrates or entire males. Marbling appeared to decrease as dietary lysine was increased among IC males. As expected, IC males had a greater (P<0.05) percentage fat-free lean than physical castrates but less (P<0.05) than entire males. Immunologically castrated males fed diets with medium/high and high lysine had greater (P<0.05) lean cutting yields and carcass cutting yields than physical castrates. Lean cutting yield and carcass cutting yields appeared to increase as dietary lysine was increased among IC males. Overall, immunological castration improved carcass cutability, increased percentage fat free lean, and had no effect on pork quality when compared with physical castrates.

Immunisation against gonadotrophin-releasing hormone (GnRH) increases growth and reduces variability in group-housed boars

It is generally accepted that entire boars are leaner and more efficient than barrows but that they have poorer meat quality with an increased risk of boar taint. An additional issue in producing boars to meet market specifications is variation in growth performance, which may be exacerbated by high levels of aggression and mounting behaviour in group-housed animals. Immunisation against gonadotrophin-releasing hormone (GnRH), leading to immunological castration, offers a means of reducing aggression and mounting behaviour while maintaining most of the production efficiencies associated with entire boars. A total of 120 control boars, 120 immunised boars and 60 barrows (physically castrated at 5 days of age) were used in a study conducted in two replicates. Each replicate consisted of two pens each of boars, immunised boars and barrows, each pen containing 15 pigs, and two blocks of 15 individually-housed boars and immunised boars. The group-housed pigs had access to two single place electronic feeders per pen. Immunised boars were given the anti-GnRH vaccine (Improvac) at 14 and 18 weeks of age. In the 2 weeks immediately after the secondary immunisation at 18 weeks, average daily gain was greater in the immunised boars than the boars or barrows, particularly in those that were group housed, as indicated by the interaction (P = 0.035). From 18 to 23 weeks of age average daily gain was greater (P = 0.005) in immunised boars than in control boars and barrows and was greater (P < 0.001) in individually- than in group-housed pigs. The average daily gain of group-housed immunised boars and individually-housed control boars were similar over the 5-week period after secondary immunisation (1090 vs 1099 g/day), being ~20 and 15% higher than the group-housed control boars and barrows, respectively. The average daily feed intake was greater (P = 0.011) in immunised boars than in control boars with barrows intermediate. The standard deviation of bodyweight increased with age but was lower (P from 0.032 to 0.09) in immunised boars than in control boars and barrows between 18 and 22 and 17 and 21 weeks of age. Carcass fighting damage and pork pH were higher (P < 0.05) for control boars than for immunised boars or barrows. In conclusion, immunisation against GnRH increased average daily gain and average daily feed intake while decreasing variation in bodyweight and improving carcass and pork quality.

Carcass and meat quality characteristics of immunocastrated male, surgically castrated male, entire male and female pigs

The aim of the study was to evaluate the effect of immunocastration on meat and carcass quality compared with meat from females, entire and surgically castrated males. One hundred and eighteen (LandracexDuroc)xPietrain crossbred pigs were assigned to four experimental groups: entire males (EM), females (FE), surgically castrated males (CM) and vaccinated males (IM). Pigs were reared in two pens per sex and slaughtered at an average of 180 days of age. Carcass and meat quality characteristics such as testis size and length, fat depth, lean content, proportion of the carcass represented by each joint, pH, colour and intramuscular fat were evaluated. There was a significant reduction in the size of these sexual organs in IM compared with EM. CM and IM were fatter than FE and EM in the loin area but, in the ham area, CM was the fattest and EM the leanest, while IM and FE were in between. Intramuscular fat of IM (2.1%) was no different from the other sexes evaluated, although it was higher in CM (2.5%) with respect to FE (1.7%) and EM (1.8%). There was no difference between the IM and other treatment groups in meat quality. Regarding ours results we can conclude that from the point of view of meat and carcass quality the immunocastration could be a good alternative to the surgical castration.

Sensory characterization of meat from pigs vaccinated against gonadotropin releasing factor compared to meat from surgically castrated, entire male and female pigs

Boar taint is a sensory defect mainly due to androstenone and skatole. The most common method to control boar taint is surgical castration at an early age. Vaccination against gonadotropin releasing factor (also known as immunocastration) is an alternative to surgical castration to reduce androstenone content. In this experiment, loins from 24 female (FE), 24 entire male (EM), 24 vaccinated males (IM) and 23 surgically castrated males (CM) were evaluated by eight trained panellists in 24 sessions. Loins were cooked in an oven at 180°C for 10min. Furthermore loins were evaluated by consumers and its androstenone and skatole content were also chemically determined. Meat from EM had higher androstenone and skatole odour and flavour than meat from FE, IM and CM and lower sweetness odour scores. High correlations were found between androstenone and skatole levels assessed by trained panelists, chemical analysis and consumers' acceptability. Moreover meat from EM is mainly related to androstenone and skatole attributes.

Ractopamine supplementation increases lean deposition in entire and immunocastrated male pigs

Sixty entire male pigs (Large White × Landrace × Duroc crossbred) were individually reared from 45 to 114 kg liveweight in a 2 by 3 factorial experiment to determine the interactive effects of sex (entire male pigs v. male pigs immunologically castrated using Improvac with vaccinations administered at 13 weeks of age and 5 weeks before slaughter) and a ractopamine feeding program (constantly fed 0 or 5 ppm ractopamine for 26 days before slaughter v. a step-up program where 5 ppm of ractopamine was fed for 14 days followed by 10 ppm ractopamine for the final 12 days before slaughter) on growth performance, carcass composition and pork quality. Following the second vaccination, immunocastrated pigs ate more (P < 0.001) and grew faster (P < 0.05) than entire male pigs without affecting feed conversion efficiency. Dietary ractopamine supplementation for the last 26 days before slaughter improved feed conversion ratio (P = 0.024) and daily gain (P = 0.046). Dietary ractopamine supplementation also increased carcass total tissue (P = 0.023) and total lean (P = 0.027) content without affecting the objective meat quality (P > 0.05) in both entire and immunocastrated male pigs. The effects of dietary ractopamine and immunocastration were additive, such that pigs that were immunocastrated and received ractopamine grew 18% faster than control entire males. However, a step-up program of ractopamine supplementation did not provide further improvements in growth performance and carcass composition when compared with constant 5 ppm ractopamine supplementation. These findings indicate that ractopamine supplementation improved growth performance in entire and immunocastrated male pigs, thereby offering a means of improving growth performance of entire males without detrimental effects on pork quality.

Dietary betaine and ractopamine combine to increase lean tissue deposition in finisher pigs, particularly gilts

Dietary ractopamine increases lean tissue deposition, with the responses most evident at ad libitum feed intakes whereas dietary betaine can improve growth by reducing maintenance requirements, with the greatest responses occurring when energy is limiting. This study was conducted to investigate the interactions between dietary ractopamine and betaine on growth and carcass characteristics in restrictively fed [31.0 MJ digestible energy (DE)/day for 14 days followed by 36.8 MJ DE/day for 21 days] boars and gilts. Forty individually penned pigs (58.4 kg) were allocated to a 2 × 2 × 2 factorial arrangement of treatments, with the respective factors being sex (gilt or boar), dietary betaine (0 and 1.5 g/kg betaine) and dietary ractopamine (0 and 10 ppm ractopamine) for 35 days. Over the first 14 days of the study when the restriction was greatest, daily gain was greater in pigs fed betaine (+8%, P = 0.04) and in boars (+12%, P = 0.005) but was not affected by ractopamine (P = 0.18). Lean deposition was greater in pigs fed betaine (+5%, P = 0.08) and in boars (+6%, P = 0.006) but was not affected by ractopamine (P = 0.57). However, there was an interaction (P = 0.03) between ractopamine and sex such that ractopamine increased lean deposition in gilts but not boars. Thus, betaine and ractopamine had additive effects on lean mass in gilts (+5.1 kg) but not boars. Fat deposition was less in pigs fed ractopamine (–8%, P = 0.05) and in boars (–17%, P < 0.001) but was not affected by betaine (P = 0.81). However, there was an interaction (P = 0.04) between dietary ractopamine and sex such that ractopamine decreased fat deposition in gilts (–14%) but not boars. In conclusion, dietary betaine and ractopamine may have additive effects on lean deposition and improve body composition in gilts but responses in boars are more equivocal.

Consumers' sensory acceptability of pork from immunocastrated male pigs

Boar taint is the off-odour or off flavour of cooked pork. Currently, the most common method of controlling boar taint is surgical castration. However, immunocastration has been used in some parts of the world as an alternative to surgical castration. The aim of this study was to evaluate the sensory acceptability of meat from immunocastrated pigs (IM) compared with meat from females (FE), surgically castrated (CM) and entire males (EM). Twenty animals of each type were evaluated by 201 consumers in 20 sessions. Longissimus thoracis muscle of the different animals was cooked in an oven at 180°C for 10min. Consumers scored the odour and the flavour of the meat in a 9-point category scale without an intermediate level. There were no significant differences in consumer's evaluation of meat from IM, CM, and FE. In contrast, EM meat presented a higher percentage of dissatisfied scores and was significantly (P<0.05) less accepted than meat from CM, IM and FE. Consumers' acceptability of EM meat was always lower, independently of its androstenone levels. However meat with low levels of androstenone was more accepted that meat with medium or high levels of this substance. It can be concluded that immunocastration produced pork that was accepted by the consumers, and was indistinguishable from pork from CM or FE.

Effect of the GnRH vaccine GonaCon on the fertility, physiology and behaviour of wild boar

Fertility control has the potential to be used as an attractive alternative to lethal methods for limiting population growth in overabundant species. This study tested the effectiveness and potential side effects of the single-dose gonadotrophin-releasing hormone (GnRH) vaccine GonaCon on the physiology and behaviour of two groups of captive female wild boar in two sequential trials (Trial 1 and Trial 2). Following vaccination with GonaCon, data on contraceptive effectiveness were recorded as well as data on time budget, social rank, bodyweight, haematology and biochemistry. The concentration of GnRH-antibody titres peaked 2–6 weeks after vaccination and remained relatively high 12 weeks after vaccination. In Trial 1, all control females and none of the treated females gave birth. In Trial 2, faecal progesterone of treated females decreased to basal levels within a month of vaccination. No differences in time budget, social rank and blood parameters were observed between treated and control females. Bodyweight increased more in treated females than in controls. These results indicated that GonaCon can suppress reproduction of wild boar with no significant short-term effects on behaviour and physiology. GonaCon can be regarded as an effective, humane and safe contraceptive for managing wild boar populations.

Gene expression of 3beta-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase in relation to androstenone, testosterone, and estrone sulphate in gonadally intact male and castrated pigs

Androstenone is one of the main compounds responsible for boar taint, and 3beta-hydroxysteroid dehydrogenase (3betaHSD) might be involved in its metabolism. In this study, the gene expression of 3betaHSD and 17beta-hydroxysteroid dehydrogenase (17betaHSD) were determined by real-time PCR analysis and related to the concentrations of androstenone, testosterone, and estrone sulphate (E1S). The experiments were performed on gonadally intact male pigs classified based on high or low fat androstenone concentrations, as predetermined by HPLC, as well as on immunocastrated and surgically castrated male pigs. The male pigs with high androstenone concentrations in fat had low 3betaHSD gene expression in liver and testis. Moreover, the 17betaHSD gene expression in liver, but not in testis, varied negatively with fat androstenone concentrations. Immunocastrated and surgically castrated male pigs had nondetectable concentrations of fat androstenone and plasma testosterone and E1S, and the castration procedure induced a significant increase of 3betaHSD and 17betaHSD gene expression. The mRNA expression was generally much greater from the 3betaHSD than from the 17betaHSD gene. Furthermore, fat androstenone was negatively correlated with liver 3betaHSD gene expression (Pearson correlation, r = -0.69; P < 0.05), and the 17betaHSD gene expression in liver was negatively correlated with plasma E1S (r = -0.95; P < 0.001), indicating an important role of liver 17betaHSD in the estrogen metabolism of gonadally intact male pigs. Another strong correlation was found between 3betaHSD and 17betaHSD gene expression in liver of the gonadally intact male pigs (r = 0.86; P < 0.01), possibly reflecting similar regulation mechanisms of these genes.

A review of the welfare consequences of surgical castration in piglets and the evaluation of non-surgical methods

Male piglets are castrated primarily to prevent the unpleasant odours and flavours of entire male pig meat (boar-taint). Although castration can be legally performed without analgesia in the first seven days of life, available evidence shows that castration at any age is painful and may have a detrimental influence on health. Few anaesthetics or analgesics are licensed for use in piglets. The known methods for general and epidural anaesthesia cannot be run at the farm level for practical and/or legal reasons. Use of the local anaesthetic lidocaine is easy and allows the pain resulting from castration to be alleviated. Local destruction of testicular tissue by intra-testicular injection of chemical compounds (salts and acids) is an alternative to surgical castration but needs further investigation regarding welfare improvement and boar taint reduction. Immunocastration, by which castration is achieved using active immunisation (anti–GnRH immunisation) is an efficient alternative to surgical castration; however, there are no licensed vaccines in the EU and the consequences, in terms of pig welfare as well as its acceptability among EU consumers, need further evaluation.

Effects of dietary factors and other metabolic modifiers on quality and nutritional value of meat

A number of technologies that increase feed efficiency and lean tissue deposition while decreasing fat deposition have been developed in an effort to improve profitability of animal production. In general, the mode of action of these metabolic modifiers is to increase muscle deposition while often simultaneously reducing fat deposition. However, there have been some concerns that the focus on increasing production efficiency and lean meat yield has been to the detriment of meat quality. The aim of this review is to collate data on the effects of these metabolic modifiers on meat quality, and then discuss these overall effects. When data from the literature are collated and subject to meta-analyses it appears that conservative use of each of these technologies will result in a 5-10% (0.3-0.5kg) increase in shear force with a similar reduction in perception of tenderness. However, it should be borne in mind that the magnitude of these increases are similar to those observed with similar increases in carcass leanness obtained through other means (e.g. nutritional, genetic selection) and may be an inherent consequence of the production of leaner meat. To counter this, there are some other metabolic factors and dietary additives that offer some potential to improve meat quality (for example immuncastration) and it is possible that these can be used on their own or in conjunction with somatotropin, approved β-agonists, anabolic implants and CLA to maintain or improve meat quality.

Porcine somatotropin alters body composition and the distribution of fat and lean tissue in the finisher gilt

The present study was designed to determine whether porcine somatotropin (pST) reduces whole animal and belly fat using dual energy X-ray absorptiometry and manual dissection. The study utilised 24 Large White × Landrace gilts selected at 16 weeks of age with an approximate liveweight of 80 kg and housed in individual pens. Gilts were stratified on liveweight into 8 blocks and 1 pig from each block was assigned to either 0, 5 or 10 mg per day of pST. Pigs were fed ad libitum a wheat-based diet containing 200 g crude protein, 10.2 g available lysine and 14.6 MJ DE/kg, to ensure that responses to pST were expressed. Feed intake and liveweight were measured on a weekly basis. An Hologic QDR4500A dual energy X-ray absorptiometer was used to determine lean, fat and ash composition of pigs initially and again 4 weeks later at the end of the experiment. After slaughter, the composition of the whole half carcass as well as the shoulder, ham, belly and loin primal cuts was determined with dual energy X-ray absorptiometry and verified with manual dissection. Daily pST treatment decreased feed intake (3440, 2710 and 2537 g/day for 0, 5 or 10 mg pST per day, respectively; P<0.001) and decreased feed conversion ratio (2.95, 2.18 and 2.03 g/g; P<0.001) even though there was no significant effect on daily gain. Pigs treated with pST deposited more lean tissue (620, 839 and 873 g/day; P<0.05) and less fat (384, 218 and 176 g/day; P<0.001) than control animals, but there was no effect of pST on ash deposition. As a consequence, pigs treated with 5 and 10 mg pST/day contained 5 and 9 kg less dissectible fat than control gilts, respectively. A dose dependent decrease in belly, loin, ham and shoulder fat was also observed, although the decrease in belly fat was more pronounced than for the whole carcass and other primal cuts. Overall, pST treatment has the potential to decrease carcass and especially belly fat in pigs and increase consumer acceptance of pork in markets that place a premium on carcass fat and lean yield in the belly region. The results determined with dual energy X-ray absorptiometry were confirmed by manual dissection.

Sex and porcine somatotropin impact on variation in growth performance and back fat thickness

Managing variation in carcass weight and composition is an enormous challenge for the pig producer. A means of improving growth performance and reducing back fat is porcine exogenous somatotropin (pST) treatment. It is possible that this technology may also reduce variation in these important growth and carcass parameters. This study was conducted to provide data on the effect of sex and pST on variation in growth and carcass characteristics. Sixteen on-farm studies involving 1495 pigs were conducted in various states within Australia. On each farm, groups of pigs were randomly assigned within sex to one of 2 management regimes (control or pST regime). The control regime consisted of feeding the typical finisher diet used on that farm while the pST regime involved feeding the typical grower diet used on the farm combined with daily injections of pST (5 mg/day). Data from individual pigs were collated and the summary descriptive statistics derived for each treatment group on each farm were then analysed. Daily liveweight gain was lower and feed conversion ratio (FCR) and back fat at the P2 site were higher in gilts than in boars. The pST regime increased average mean daily gain and reduced feed intake, FCR and back fat at the P2 site. The coefficient of variation (CV) around live daily gain was lower in gilts than in boars (19.3 v 22.3% for gilts and boars, respectively, P<0.001) and in pigs treated with the pST regime (22.1 v. 19.9% for the control and pST regimes, respectively, P<0.001). The CV around liveweight was higher in the control boars than in any of the other treatment groups as indicated by the main (P<0.001) and interactive (P<0.001) effects of both sex and pST regime. The coefficient of variation around P2 was reduced by pST (16.2 v. 14.2%, P<0.001) but was not different between gilts and boars. There was an interaction (P = 0.025) between pST regime and sex with the average kurtosis for the P2 distribution positive in gilts treated with pST but slightly negative in all the other groups. The distributions were on average skewed to the right, particularly in gilts (P = 0.017) and in pigs treated with pST (P<0.001). In conclusion, these data demonstrate that as well as improving mean final liveweight and P2 back fat, pST treatment can also reduce variation in these key production parameters that form the basis for economic returns to the producer.

Interrelationships between porcine somatotropin (pST), betaine, and energy level on body composition and tissue distribution of finisher boars

Fifty-six individually penned boars (initial weight 64 kg) were used to investigate the interactions between dietary betaine, dietary energy, and porcine somatotropin (pST) treatment. The study was a 2 × 2 × 2 factorial experiment with the respective factors being dietary betaine (0 or 1.5 g/kg) and energy level (80% or 100% ad libitum) and treatment with pST (0 or 5 mg/day). A Hologic QDR4500A Dual Energy X-ray Absorptiometer (DXA) was used to determine body composition of pigs at the beginning and end of the study at Day 35. After slaughter, the composition of the whole half-carcass as well as the shoulder, ham, belly, and loin primal cuts was determined with DXA and verified with manual dissection. The main effects of dietary betaine were most pronounced when dietary energy was restricted. Under these conditions, daily gain was increased by dietary betaine (1188 v. 1271 g/day, P = 0.049) and pST (1115 v. 1344 g/day, P < 0.001). When dietary energy was restricted, lean tissue deposition was increased by dietary betaine (830 v. 908 g/day, P = 0.032) and pST (764 v. 974 g/day, P < 0.001), and these effects were additive. As a result, the lean meat yield in the half-carcass was increased by both dietary betaine (23.9 v. 25.1 kg, P = 0.043) and pST (23.3 v. 25.7 kg, P < 0.001). Lean tissue responses in primal cuts were more variable but followed a similar pattern. There was little effect of either dietary betaine or pST on fat deposition. These data demonstrate that when energy intake is limiting the potential for growth (as is normally the case for the improved boar), then both dietary betaine and pST treatment, either alone or in combination, can increase lean tissue deposition without increasing fat deposition.

The influence of dietary energy intake on growth performance and tissue deposition in pigs between 80 and 120 kg liveweight

Eighty crossbred pigs of a composite genotype were allocated at 80 kg liveweight to a 2 × 5 factorial experiment involving 2 sexes (boars and gilts) and 5 levels of dietary energy intake ranging from about 55% estimated ad libitum up to 100% ad libitum intake. The diet was formulated to be protein-adequate and contained 14.4 MJ DE/kg and 0.55 g available lysine/MJ DE and the pigs were slaughtered at approximately 120 kg liveweight. Growth rate and food conversion efficiency increased linearly, in response to increasing digestible energy (DE) intake, with boars consistently out-performing gilts at each level of DE intake. Protein deposition rate in the whole empty body of pigs was consistently higher in boars than in gilts and linearly related to DE intake in both sexes, with no evidence of a plateau at high energy intakes, suggesting no intrinsic limit to protein deposition in these pigs up to 120 kg liveweight. When pigs were offered the protein-adequate diet ad libitum between 80 and 120 kg liveweight, boars and gilts consumed 47.7 and 40.9 MJ DE/day, respectively, and protein deposition rates in the whole empty body of pigs reached 247 and 182 g/day, respectively. Maintenance energy requirements were estimated to be 351 kJ DE/kg0.75.day for both boars and gilts [maximal model; including nominal DE level (treated as a 5-level factor), actual DE intake (treated as a continuous variable), and sex (treated as a 2-level factor)] or 506 and 566 kJ DE/kg0.75.day for boars and gilts, respectively [reduced model; including actual DE intake (treated as a continuous variable) and sex (treated as a 2-level factor)]. Statistical analyses show that the maximal model reflects the data more closely than the minimal model, suggesting that the lower maintenance estimate of 351 kJ DE/kg0.75.day could reflect reality better. In conclusion, genetically improved boars, and to a lesser extent gilts, have a high capacity for lean growth, and their upper limit to protein retention might not be reached below about 120 kg liveweight.

A gonadotropin-releasing factor vaccine (Improvac) and porcine somatotropin have synergistic and additive effects on growth performance in group-housed boars and gilts

Two hundred and twenty-four pigs (112 boars, 112 gilts) housed in pens of seven pigs per pen were used in a 2 x 2 x 2 factorial design, with the factors of vaccination with a gonadotropin-releasing factor (GnRF) vaccine (Improvac; 0 or 2 mL at 13 and 17 wk of age), porcine somatotropin (pST; 0 or 5 mg/d from 17 wk of age), and gender. Pigs were weighed and feed intake was measured from 17 wk of age until slaughter at 21 wk of age. Body composition was estimated by dual-energy X-ray absorptiometry in two focus pigs per pen at 17 and 21 wk of age. Testes and ovary weights at slaughter were decreased by Improvac treatment (P < 0.001), but were not altered by pST treatment (P > 0.44). Daily gain was lower for gilts than boars (1,128 vs. 1,299 g/d, P < 0.001) and was increased by pST (1,172 vs. 1,255 g/d, P = 0.003) and Improvac (1,150 vs. 1,276 g/d, P < 0.001) treatments. Feed intake (as-fed basis) was lower in gilts than in boars (2,774 vs. 3,033 g/d, P = 0.002), was decreased by pST (3,037 vs. 2,770 g/ d, P = 0.002), and was increased by Improvac treatment (2,702 vs. 3,105 g/d, P < 0.001). As a result of the differences in feed intake and daily gain, feed conversion efficiency (gain:feed) was lower for gilts than for boars (0.403 vs. 0.427 P = 0.025), was improved by pST (0.385 vs. 0.452, P < 0.001), but was unchanged by Improvac treatment (0.423 vs. 0.410, P = 0.22). Carcass weight was lower in gilts than in boars (75.3 vs. 77.0 kg, P = 0.012), was unchanged by pST treatment (75.9 vs. 76.4 kg, P = 0.40), and was increased by Improvac treatment (75.1 vs. 77.2 kg, P = 0.003). Lean tissue deposition rate was lower in gilts than in boars (579 vs. 725 g/d, P < 0.001), was increased by pST (609 vs. 696 g/d, P < 0.001) and by Improvac treatment (623 vs. 682 g/d, P = 0.014). Fat deposition rate tended to be lower in gilts than in boars (214 vs. 247 g/d, P = 0.063), decreased by pST treatment (263 vs. 198 g/d, P < 0.001), and increased by Improvac treatment (197 vs. 264 g/d, P < 0.001). For pigs treated with both pST and Improvac, daily gain and lean tissue deposition rate was greater than for pigs that received either treatment alone, whereas fat deposition rate and feed intake did not differ from untreated control pigs. In conclusion, Improvac increased growth rate through increased lean and fat deposition, but concomitant use of Improvac and pST increased lean gain above either alone, while negating the increase in fat deposition in pigs treated with Improvac.