Castration

Castrating male animals is considered less necessary than it used to be, and the growth advantage of the entire male outweighs its other disadvantages. Nevertheless, many countries still castrate pigs, lambs and cattle. In Australia, Eire, New Zealand, Spain and the UK most pigs are left entire, and in Denmark castration is no longer used on every farm. Castration is mainly done where there are concerns about boar taint, and this is associated with slaughtering at heavy weights.

The off odours and flavours associated with boar taint are linked to androstenone and skatole in the fat. The risk of skatole odours is increased if the boars are kept at high stocking densities and they lie in their own manure (Hansen et al ., 1997). Androstenone contributes to both boar odour and flavour, whilst skatole and its derivatives are quite volatile and so they are more likely to create odour problems during cooking.

The way the pig meat is presented determines whether boar taint is noticeable (Bañon et al ., 2003a). This is shown in the detection thresholds listed in Table 12.3. Dry cured meats contain oxidized fats, which help mask boar taint. Cooked ham is often eaten cold and so volatile off odours are also less obvious in this type of product. However, there are ethnic and gender differences in sensitivity to boar taint, and awareness of the odour is not always predictable (de Kock et al ., 2001).

Table 12.3. Threshold values for the organoleptic detection of androstenone and skatole in pig meats.

When castration increases the fat content of pig meat, salt uptake during dry-curing is reduced and saltiness can be less pronounced (Bañon et al ., 2003b). In other words, boar meat can carry a saltier flavour. In Canada, boar meat has been shown to be marginally tougher and paler, but this is not a widely recognized feature (Sather et al ., 1999). When boar carcasses are leaner, there can be less marbling. Including the Duroc in the sire line helps to reduce the adverse effect this has on eating quality (Channon et al ., 2004).

The Meishan breed reaches sexual maturity earlier than other breeds, and it is favoured by some breeding companies for female lines because of its prolificacy. The cross-bred progeny also express precocious puberty and the males are prone to developing boar taint by the time they reach market weight. In this situation, including sugarbeet pulp in the grower ration can help to correct the taint (Whittington et al ., 2004).

In cattle, castration helps to increase fat content of the meat. This is not always sufficient to improve juiciness, but there can be less cooking loss in meat from steers compared with bulls (Destefanis et al ., 2003).

The flavour difference between ram and castrate lambs is subtle and not easily distinguished. Ram lamb meat can have a sweaty odour, which is due to 4-methyloctanoic and 4-methylnonanoic acids in the fat (Sutherland and Ames, 1995). In Hispanic countries a substantial number of ram lambs are slaughtered at light weights (e.g. 10 kg carcass weight). It would be possible to slaughter ram lambs larger than this without incurring meat quality defects for this particular market (Sañudo et al ., 1996). There would, however, need to be changes in the way the carcasses are cooked and presented if these lambs are to be slaughtered at heavier weights.

Goat meat from intact males has a reputation amongst some consumers for its rank odour. However, objective trials have shown no difference in flavour from castrates up to the age of 310 days (Madruga et al ., 2000).