3.0 Meat Quality and Carcass Composition of Pigs Fed Full Fat Canola Seed
Similar carcass compositional changes were found with the inclusion of full fat canola seed as with canola oil. Diets containing RS did not change backfat thickness or percentage of muscle but had an impact on FA composition. Higher polyunsaturated fatty acid (PUFA) in the feed passes unchanged into the body fat. Despite the beneficial reduction in the n6 to n3 fatty acid ratio (8.05 - 3.95), back fat consistency declined, oxidative stability is reduced and long term storage shortened (Raj et al. 1995 {1647}. Busboom et al. 1990 {1795}) identified that different tissues respond differently to canola addition with perirenal adipose tissue being the most responsive, followed by subcutaneous adipose tissue then longissimus dorsi and finally intramuscular adipose tissue.
Up to 18g PUFA/kg feed (105-150g kg-1
rapeseed) can be fed to pigs 25-105 kg without adverse effect
on backfat color, consistency or storage stability. At this level
intrinsic meat quality is unaffected (Warnants et al. 1995
{1639}). In agreement, Kracht et al. (1996 {1614}) recommended
that whole RS not exceed 100g kg-1 of the diet. However,
they found that RS moistened with water and heated to 105C for
5 minutes was successful in diminishing the level of PUFA possibly
through hydrogenation. If the RS was removed from the diet at
day 70 as opposed to being fed for the entire 126 days, PUFA levels
declined by as much as 300g kg-1 even when RS was included
at 200g kg-1 of the diet. This was confirmed by Gill
et al. (1995 {1628}) who recorded that the undesirable
trend to softer backfat was partly reversed by withdrawing full
fat rapeseed at 70kg liveweight. As well, Busboom et al.
1990 {1795}) found vitamin E supplementation in the form of 1
gram per day a-tocopherol (plus the high inherent -tocopherol
of full fat rapeseed 27 mg kg-1) increased vitamin
E concentrations in the backfat which resulted in improved oxidative
stability with no effect on fatty acid pattern (Flachowsky et
al. 1997 {1600}).
Studies show little evidence to suggest that glucosinolates
in whole canola seed negatively affect the performance of pigs
at levels below 150-200g kg-1 of the diet. Nonetheless,
undesirable changes to the organoleptic and storage properties
of pork may be the first limiting factor when full fat canola
levels exceed 100g kg-1 of the diet. Despite these
limitations, full fat canola seed provides an economical and
manageable method to incorporate fat into the pig diets with overall
beneficial effects on performance.