Epsilon Open Archive

Abstract

The aim of this study was to investigate the effects of prepubertal or early pubertal vaccination against GnRH using Improvac® (Pfizer Ltd.) on boar taint, reproductive organs, anabolic hormones, cytochrome P450 enzymes, performance and behaviour. Crossbred male pigs (n=192) were randomly allocated to four groups: one group surgically castrated without anaesthesia, a second group receiving early vaccination (at ages 10 and 14 weeks), a third standard vaccinated group (at ages 16 and 20 weeks), and a fourth group of entire male pigs.

After the second injection, antibody titres increased rapidly and testicular steroids decreased to the low levels of castrates. Reproductive organs were small in vaccinated pigs and smaller after early vaccination. Spermatogenesis and steroidogenesis were disrupted with a more severe, possibly irreversible effect after early vaccination. Oestradiol was suppressed for castrated and vaccinated pigs. IGF-1 was lowest for castrates and highest for entire male pigs, with vaccinated pigs at an intermediate level.

Hepatic CYP450 mRNA expression was highest for castrated and early vaccinated pigs, and lowest for entire male pigs, suggesting suppression at the transcriptional level of CYP1A2, CYP2A and CYP2E1 by testicular steroids. This did not correspond exactly with protein expression and activities, suggesting other regulations for some CYP450s. The levels of skatole and androstenone in adipose tissue were low in castrated and vaccinated pigs, whereas entire male pigs had elevated levels.

Daily weight gain and feed conversion did not differ between groups and income per carcass did not differ between castrated or vaccinated pigs. The income was lower for entire male pigs, due to the additional cost for boar taint analyses and reduced payment for tainted carcasses. After vaccination, the frequency of interactions, both problematic and non-problematic, decreased from the levels of entire males to those of surgically castrated pigs.

Under these conditions, early vaccination with Improvac can be used to control boar taint, testicular function and behaviour with unaffected profitability. Thus, the flexi¬bility of vaccination may be extended, implying advantages in terms of animal welfare and sustainability.