Early vaccination with Improvac®: effects on performance and behaviour of male pigs

Abstract

The aim of this study was to investigate the effect of giving a two-dose regimen of gonadotropin-releasing hormone vaccine, Improvac R (Pfizer Ltd), earlier than currently recommended, on performance and behaviour of growing/finishing pigs. Cross-bred male pigs (n 5 192) were randomly allocated, within a litter, into four groups at birth: one group of pigs surgically castrated without anaesthesia before one week of age, a second group of early vaccinated pigs given Improvac at 10 and 14 weeks of age, a third group of standard vaccinated pigs given Improvac at 16 and 20 weeks of age, so that the second vaccination was given 4 to 6 weeks before slaughter as recommended by the manufacturer, and a fourth group of entire male pigs. The experiment started when the pigs were 12 weeks old and lasted until 25 weeks of age, when the pigs were slaughtered. The pigs were fed restrictedly. Daily weight gain and feed conversion during the entire raising period did not differ significantly between groups. Estimated lean meat content of early vaccinated and surgically castrated pigs was lower when compared with entire male pigs, whereas standard vaccinated pigs did not differ from entire males. Dressing percentage was higher in early vaccinated and surgically castrated pigs than in standard vaccinated and entire male pigs, partly because of lower size and weight of reproductive organs. For both groups of vaccinated pigs, both problematic and non-problematic behaviours decreased after their second injection, from the levels of entire males to those of surgically castrated pigs. After the second injection, pigs of both vaccination groups performed no mountings, in contrast with entire male pigs of the same age. Skin lesions at slaughter were fewer and less severe for vaccinated pigs compared with entire male pigs. No difference in income per carcass was observed for surgically castrated or vaccinated pigs. However, for entire male pigs the income was lower, as the payment system in Sweden also takes into consideration the additional cost for boar taint analyses and reduced payment for tainted carcasses. Under our experimental conditions, early vaccination with Improvac can be used as an alternative to the recommended schedule to minimise problematic behaviour with unaffected profitability.Keywords: male pigs, early vaccination against GnRH, performance, behaviour ImplicationsThis study showed that an earlier than recommended vaccination of male pigs with a gonadotropin-releasing hormone vaccine, Improvac, yielded results similar to surgical castration and the recommended vaccination schedule regarding production and behaviour. This implies that the vaccination can potentially be administered at a younger age, and the flexibility of vaccination increased for pig farmers who find the manufacturer's recommended vaccination schedule impractical. Although early vaccination is a potential alternative to the currently recommended vaccination schedule, it needs to be more extensively studied for different breeds under different practical...

Welfare of entire male pigs is improved by socialising piglets and keeping intact groups until slaughter

“…Thus, we assume that the aggressive interactions observed in groups of familiar pigs at the end of the growing-finishing phase are less problematic than those observed at mixing. Compared with previous studies (Rydhmer et al, 2010;Andersson et al, 2012), the frequency was rather low for both treatments. However, because of heavy body weight and limited space available in the pen at this stage, this unexpected result should not be ignored.…”

“…They probably had less need for resting as they spent less energy on fighting, which is an energyconsuming activity (Lepron et al, 2007). Except for the newly mixed control pigs, the distribution of activities during the day observed in this study was in accordance with previous studies (Bolhuis et al, 2005;Andersson et al, 2012); young pigs spend approximately half of the day lying down and the time increases with increasing age during the growing-finishing phase. Even so, they have plenty of time for social interactions such as nibbling, belly suckling and ear and tail manipulating.…”

“…The frequency of sexual behaviour (mounting) in our study was of the same size as in previous Swedish studies (Rydhmer et al, 2006 and2010;Andersson et al, 2012). Non-litter mates were mounted more often than litter mates in both treatments (significant at two of three occasions per treatment).…”

“…We have previously suggested that these behaviours, which are performed to a higher degree by entire males than females, reduce calmness, and thus may decrease welfare (Rydhmer et al, 2010). The frequency of these behaviours were, however, lower in this study than in the studies by Rydhmer et al (2010) and Andersson et al (2012) and there was no difference between treatments.…”

“…Skatole, but especially androstenone levels were alarmingly high in our study, resulting in 89% of all pigs above the threshold levels for boar taint. In a recent study at the same research station, the corresponding rate was 66% (Andersson et al, 2012). The study by Fredriksen et al (2008) was a field study and they found large differences between herds.…”