Altering the timing of an immunocastration vaccine to optimise pig performance

Entire male pigs are more efficient and leaner than surgical castrates, but ’boar taint’ can compromise eating quality. Vaccination of boars with a gonadotropin releasing hormone (GnRH) vaccine (Improvac®, Pfizer Ltd, Parkville, VIC) can eliminate boar taint, and allows pigs to retain all of the performance attributes of entire males up until the time they receive the second vaccination, normally four to five weeks pre-slaughter (Dunshea et al., 2001). However increases in backfat depth (P2) and feed conversion ratio (FCR) compared to entire males has limited the uptake of this technology. If giving the second vaccination closer to the time of slaughter could eliminate boar taint, there would be less of a cost in lost production to producers. An experiment was conducted to test the hypothesis that reducing the time between administration of the second vaccination with the GnRH vaccine and their slaughter will reduce the impact on P2 and FCR while still reducing boar taint

Variation in weights of primal pork cuts

The payment system used in Australia uses the weight of the carcase and fat depth at the P2 site to determine the price per kg carcase weight paid to producers. This economic incentive for a specific weight range and a higher overall lean meat content in the carcase has resulted in larger and leaner cuts available to consumers across Australia in comparison to pork cuts available in the 1980s and 1990s (Müller et al., 2009). The study also found only small differences in the lean meat content of pork cuts between states and areas of different socio-economic status 'due to breeding and feeding for large, lean pigs by the Australian pig industry' as the authors concluded. While the variation in the proportion of lean in each raw cut was modest, considerable variation was observed in the weight of cuts, fat thickness and slice thickness due to differing butchering practices. This aspect of variability has been addressed by Australian Pork Limited (APL, 2012) by providing the PorkStar training manual which outlines the various retail cuts in detail. Different prices are paid for individual pork cuts. Price differences between cuts increase as the carcase is broken down. For example, the rolling annual average wholesale price varied from $3.55 for forequarters to$ 7.77 for bellies for broken sales and from $3.92 for boneless middles above 13 mm fat depth to$ 15.07 for US ribs for carton sales (APL, Eyes and Ears, Issue #502, October 2012). At the farm gate level, carcases may be broken down to the primal cuts and the return per carcase may be increased by optimising the weight in each primal cut. Mérour and Hermesch (2008) demonstrated variation in primal cuts for carcases with similar weight and fatness levels. This variation in primal cuts resulted in an additional return per carcase of $7 at the farm gate level and$ 21 at the wholesale/retail level for the top 10% of pigs in comparison to the average. This evaluation was based on French data as similar data were not available in Australia at the time. Information has been collected about primal cut weights in Australian pigs and a first description of these data and evaluation of the variation in primal pork cuts is provided in this study

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 x 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 mu g/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 mu g/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

Field experience with surgical castration with anaesthesia, analgesia, immunocastration and production of entire male pigs: performance, carcass traits and boar taint prevalence

Male piglets are castrated to reduce boar taint and also to reduce aggressive and sexual behaviour. However, the procedure as traditionally performed is painful and negatively affects performance. Large-scale results about the consequences of implementing alternatives on farms are lacking. We, therefore, investigated the practical applicability of the following five alternatives that can be implemented in the short term: surgical castration (1) without pain relief (CONT, control group), (2) with analgesia (MET, Metacam, 0.2 ml, 10 to 15 min before castration), (3) with general anaesthesia (CO2, inhalation, 100% CO2, 25 s, 3 l/min), (4) vaccination against boar taint (IM, two injections with Improvac) and (5) production of entire males (EM). The study consisted of the following two trials: (1) an experimental farm trial with 18 animals/treatment and (2) a large field trial on 20 farms with similar to 120 male pigs/farm per treatment and all treatments performed on each farm. Performance results as well as data on carcass traits, boar taint (hot-iron method) and testes development and weight were collected in both trials. Neither castration nor administration of analgesia or anaesthesia had an effect on daily gain of the piglets in the farrowing crates (P>0.05). Farmer records indicated that mortality in the farrowing crates (1.1%), nursery pens (1.8%) and fattening stable (2.2%) was not influenced by MET or CO2 compared with EM, IM or CONT (P>0.05). No significant differences were found for daily gain (P>0.05) nor slaughter age (P>0.05). Immunocastrates and EM had a better gain-to-feed ratio (P<0.05) compared with the groups of barrows (CONT, MET and CO2). Lean meat percentage was higher for EM compared with the barrows, and intermediate for IM (P<0.05). Carcass yield was lowest for IM (P<0.05). The hot-iron method indicated that boar taint was eliminated in barrows and IM compared with EM (P<0.001). Average prevalence of strong boar taint was 3% for EM, but varied from 0% to 14% between farms. As the effect of treatment on performance as well as the level of boar taint of EM was farm dependent, farmers should be encouraged to pre-test the different alternatives in order to make a well-considered choice for the best practical and profitable alternative for their farm