Peri- and postpubertal boars accumulate substances (e.g., androstenone and skatole) in their fatty tissue that are responsible for boar taint in pork. The objective of this study was to assess the efficacy of a GnRH vaccine, Improvac, in eliminating boar taint. Three hundred male (200 intact boars, 100 barrows) crossbred (Large White x Landrace) pigs were used in a 2 x 3 factorially arranged experiment. The respective factors were sex group (barrows, boars treated with placebo, or boars treated with Improvac) and slaughter age (23 or 26 wk). Vaccines were administered 8 and 4 wk before slaughter. All Improvac-treated pigs exhibited anti-GnRH titers. Testes and bulbo-urethral gland weights in treated pigs were reduced by approximately 50% (P < 0.001) and serum testosterone levels were below 2 ng/mL in the majority of treated boars (94 and 92% across both age groups at 2 and 4 wk, respectively). Boar taint, as assessed by the concentration of androstenone and skatole in s.c. fat, was suppressed to low or undetectable levels in 100% of Improvac-treated boars. No Improvac-treated pigs had significant concentrations of either androstenone (> 1.0 microg/g) or skatole (> 0.20 microg/g). In contrast, 49.5% of placebo-treated controls had significant androstenone and 10.8% had significant skatole levels, resulting in 10% of the control boars with high concentrations of both compounds. The mean concentrations of taint compounds in the Improvac-treated pigs were not significantly different from those in barrows. Improvac-treated boars grew more rapidly (P = 0.051 and < 0.001 for pigs slaughtered at 23 and 26 wk of age, respectively) than control boars over the 4 wk after the secondary vaccination, possibly because of reduced sexual and aggressive activities. Compared with barrows, Improvac-treated boars were leaner and had superior feed conversion efficiency. The vaccine was well tolerated by the pigs, and no observable site reactions could be detected at the time of slaughter. Vaccination of boars with Improvac allows production of heavy boars with improved meat quality through prevention and control of boar taint.

Das Ziel dieser Studie war, die Wirkung der aktiven Immunisierung gegen das Gonadotropin Releasing Hormon (GnRH) bei männlichen Schweinen zu untersuchen und mit der chirurgischen Kastration zu vergleichen. Ferkel wurden randomisiert und in zwei Gruppen unterteilt: 263 Tiere für die chirurgische Kastration (SC) und 270 für die Immunokastration (IC). Der chirurgische Eingriff wurde in den ersten 14 Lebenstagen durchgeführt und die Impfung mit Improvac®, CSL, Australia, zweimal im Abstand von 4 bis 5 Wochen; die zweite Impfung (Booster) erfolgte 4 bis 7 Wochen vor dem geplanten Schlachttermin. Bei der Schlachtung wurde das Hodengewicht gewogen und Fettproben für die Bestimmung von Androstenon gesammelt. Zusätzlich wurde Androstenon auch olfaktorisch nach Erhitzung der Speicheldrüsen im Mikrowellenofen getestet. Weiter wurden die Tageszuwachsrate und Fleischqualität aller Tiere bestimmt. Die durchschnittliche Androstenon-Konzentration im Rückenfett beider Gruppen (SC und IC) wies keine signifikanten Unterschiede auf (0.042 (0.041; 0.044) µg/g vs. 0.058 (0.044; 0.071) µg/g; Durchschnitt (95 % Konfidenzinterval). Das Hodengewicht von immunisierten Ebern war signifikant (P<0.001) kleiner (230.8 (218.23; 243.52) g) als bei normalen Ebern gleichen Alters (761.8 (722.77; 801.01) g). In dieser Studie konnte bewiesen werden, dass die Androstenon Produktion in allen geimpften Tieren deutlich gehemmt war und alle Schlachtkörper konsumtauglich waren. Der durchschnittliche Tageszuwachs war zwischen SC (0.817 (0.804; 0.830) kg) und IC (0.827 (0.814; 0.840) kg) nicht signifikant verschieden, obwohl letztere Gruppe eine bessere Zuwachsrate zeigte. Der Magerfleischanteil war bei IC (54.50 (54.26; 54.73) %) im Vergleich zu SC (53.76 (53.53; 54.00) %) signifikant (P<0.001) erhöht. Aus unseren Ergebnissen kann gefolgert werden, dass die Impfung gegen GnRH eine praktische und effiziente Methode ist, um die Androstenon Synthese erfolgreich zu unterdruecken. Angst und Stress, die vor allem bei der chirurgischen Kastration auftreten, können auf diese Weise vermieden werden. The objective of this study was to investigate the efficacy of active immunization against gonadotropin releasing hormone (GnRH) in male pigs and to compare it with surgical castration. Piglets were randomly assigned to two groups, one of 263 animals for surgical castration (SC) and one of 270 animals for immunocastration (IC). Surgery was done at 14 days of age and vaccination (Improvac®, CSL, Australia) performed twice at an interval of 4 to 5 weeks with the second injection given 4 to 7 weeks before slaughter. At slaughter, testes were weighed and fat samples collected for androstenone analysis. Androstenone was tested olfactorially by heating salivary glands in a microwave oven. Daily growth rate and meat quality were assessed in all animals. Regarding mean androstenone concentrations in backfat, no significant difference was found between SC and IC (0.042 (0.041; 0.044) µg/g vs. 0.058 (0.044; 0.071) µg/g; mean (95 % confidence interval)). Testes weight was signific...

In most countries, male pigs are physically castrated soon after birth to reduce the risk of boar taint and to avoid behaviours such as fighting and mounting. However, entire male pigs are more feed efficient and deposit less fat than barrows. In addition, many animal welfare organizations are lobbying for a cessation of castration, with a likelihood that this could lead to inferior pork unless an alternative method is used to control boar taint. An alternative to physical castration is immunization against gonadotrophin releasing factor (GnRF) which allows producers to capitalize on the superior feed efficiency and carcass characteristics of boars without the risk of boar taint. From a physiological perspective, immunized pigs are entire males until shortly after the second dose, typically given 4 to 6 weeks before slaughter. Following full immunization, there is a temporary suppression of testicular function and a hormonal status that resembles that of a barrow. Nutrient requirements will be different in these two phases, before and after full immunization. Given that there have been few published studies comparing the lysine requirements of entire males and barrows in contemporary genotypes, it is useful to use gilt requirements as a benchmark. A series of meta-analyses comparing anti-GnRF immunized boars and physical castrates and use of nutritional models suggest that the lysine requirement of entire males before the second immunization is 5% higher than for gilts, from 25 to 50 kg BW, and by 8% from 50 to 95 kg. Given that the penalty in growth performance for having inadequate dietary lysine is greater in males than in gilts or barrows, it is important to ensure that lysine requirements are met to obtain the maximum benefits of entire male production during this phase. After the second immunization, the lysine requirement of immunized males decreases and may become more like that of barrows. In addition, a consistent effect of full immunization is a marked increase in voluntary feed intake from about 10 days after the second dose. Putting these together, the estimated lysine requirement, expressed in terms of diet composition, falls to 94% of the gilt level. Although general principles can be described now, further research is needed to fully define the lysine requirements of immunized boars. It is important that the temporal pattern of tissue deposition rates and feed intake be explored to be incorporated into models to predict nutrient requirements over the period of rapidly changing metabolism.Keywords: finishing pigs, growth, boars, nutritional requirements, immunological castration. ImplicationsMale pigs immunized against gonadotrophin releasing factor are physiologically entire males for most of their life and as such they should be fed as entire males at least up until the second immunization. Shortly after that time, testicular function is suppressed and the hormonal and metabolic status rapidly adjusts to resemble that of a physical castrate. As a consequence, feed intake and tissue deposition ch...

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The blood clearance rate (BCR) of cortisol was measured in non-pregnant ewes and in pregnant ewes and their intact or bilaterally adrenalectomized fetuses. In pregnant sheep the placental transfer of cortisol in both directions was established. The BCR of cortisol in the non-pregnant sheep was 51.7 +2- 4.9 (S.E.M.) l/h (n = 36) or 1.15 l/h per kg body weight. This was lower than that in the pregnant ewe (97-143 days of gestation) of 76.9 +/- 4.21 l/h (n = 9) or 1.85 l/h per kg. In the intact fetus the BCR was 8.2 +/- 0.26 l/h (n = 10) over the same period of gestation. The percentage of the maternal production rate of cortisol transferred to the fetus was 1.4 +/- 0.11% (n = 9) and the placental transfer from fetus to mother was 19.5 +/- 1.5% (n = 8). The BCR in pregnant ewes bearing bilaterally adrenalectomized fetuses was not significantly different from that of mothers of intact fetuses (58.4 +/- 7.7 l/h; n = 6). The BCR of adrenalectomized fetuses was 8.4 +/- 1.37 l/h (n = 8). The placental transfer of cortisol from mother to fetus was sufficient to account for all the cortisol measured in adrenalectomized fetuses and in intact fetuses of 100-121 days of gestation. However, it accounted for only 37% of the cortisol measured in fetuses of 122-135 days of gestation and 12% or less in fetuses older than 136 days of gestation.