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This article in JAS

  1. Vol. 89 No. 9, p. 2782-2792
    Received: June 24, 2010
    Accepted: Apr 07, 2011
    Published: December 4, 2014

    2 Corresponding author(s):


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 pigs1

  1. A. K. Lealiifano*,
  2. J. R. Pluske,
  3. R. R. Nicholls,
  4. F. R. Dunshea§,
  5. R. G. Campbell#,
  6. D. P. Hennessy,
  7. D. W. Miller,
  8. C. F. Hansen and
  9. B. P. Mullan 2
  1. Research and Innovation, Rivalea Australia Pty Ltd., Redlands Road, Corowa, New South Wales 2646, Australia;
    Animal Research Institute, School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia;
    Animal Research and Development, Department of Agriculture and Food, Bentley Delivery Centre, Western Australia 6983, Australia;
    Department of Agriculture and Food Systems, The University of Melbourne, Parkville, Victoria 3052, Australia;
    Pork CRC, University of Adelaide Roseworthy Campus, Roseworthy, South Australia 5371, Australia;
    Private Consultant, Warrandyte, Victoria 3113, Australia; and
    Department of Large Animal Sciences, Faculty of Life Sciences, University of Copenhagen, DK-1870 Frederiksberg C, Denmark



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.

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