The risk of boar taint in meat from organic entire male pigs can be reduced if the pigs are kept clean from manure and if the live weight at slaughter is lower than usual, according to a PhD project that studied approaches that can be included in an overall concept of organic male pig production.

- This finding provides organic pig farmers with good management possibilities for setting up a production of male pigs for slaughter. The greatest obstacle in such a production is the necessity of sorting pigs due to boar taint which in turn leads to economic loss, says Rikke Thomsen from the Department of Animal Science at Aarhus University and author of the PhD thesis.

The goal is that surgical castration should stop in the EU from 2018. This harmonises with the animal welfare values of organic pig production. However, the issue of boar taint still remains. The PhD project therefore focused on investigating the effect of live weight at slaughter and soiling with manure of  pens and pigs on the prevalence of boar taint in the meat.

Rikke Thomsen also studied the importance of grouping strategy and group size in relation to animal welfare. The study was carried out on five commercial organic farms and included 1,700 male pigs.

Reduced boar taint with reduced weight  

Reduced live weight at slaughter led to a reduced prevalence of boar taint measured as androstenone and skatole concentration in the carcass. The threshold for androstenone of one ppm was already reached at live weights of 60 and 80 kg for the winter and summer periods, respectively. The effect varied between farms and there was also a large variation in the level of boar taint in animals with a low slaughter weight.

Skatole can presumably be absorbed from manure through the skin or lungs. .

- We found that increased soiling in the outdoor area led to a higher concentration of skatole, although the effect varied between farms and between the summer and winter seasons, says Rikke Thomsen. Soiling of the pens had no effect on the concentration of androstenone, but the dirtier the animals the higher the concentration of skatole and androstenone.

There was a great variation in the various measurements for boar taint in both low and high levels of soiling. However, reducing the amount of manure in the pigs’ area could be useful in combination with other measures to reduce boar taint.  

Effect of group size and grouping strategy on welfare

Previous studies on conventional farms have shown that increased aggression and mounting in entire male pigs reduces animal welfare. In the present study, regrouping of male pigs at 30 kg did not result in more lesions compared to groups that were merely reduced in size. In general, however, there were slightly more lesions in groups of 30 animals compared to groups of 15 animals.

Group size did not affect mounting frequency and there was no clear effect of grouping strategy between farms.

- This indicates that the sexual behavior that leads to mounting is not particularly affected by the pigs’ environment but more by the individual traits of the pigs, says Rikke Thomsen and continues:  

- Our results show that organic entire male pigs generally experience good animal welfare because elements from organic production systems encompass the behavioural needs of entire male pigs.

The PhD thesis “Management of organic entire male pigs – boar taint and animal welfare issues” can be downloaded here.  

For more information please contact: Rikke Thomsen, Department of Animal Science, telephone +45 8715 7925, e-mail: rikke.thomsen@anis.au.dk