Outdoor finishing of intact male pigs of local breed on a high fibre diet: effects on growth, carcass, and some meat quality traits

Abstract

Thirty male pigs of the Portuguese Alentejano (AL) breed raised outdoors with ad libitum water and feed were used to test the effects of a new high soluble dietary fibre feed on animal performance and carcass traits. From 40 to 130kg body weight, surgically castrated (group C) and intact pigs (groups I and IE) were fed with commercial feeds. From 130kg until slaughter (160kg), groups C and I ate a commercial diet, while group IE was fed the isoproteic and isoenergetic experimental diet, with the incorporation of agro-industrial by-products. Average daily gain (ADG, g/d) was different between groups, with IE pigs presenting a higher ADG than C (691±15 in IE, 649±22 in I, and 610±12 in C pigs, p=0.008). This led to fewer days on trial of IE and I pigs, when compared to C pigs (167±4 in IE, 175±2 in I, and 193±5 in C pigs, p<0.001). Feed conversion ratio was different in all groups, with the lower value in IE and the higher in C group (3.9±0.1 in IE, 4.2±0.1 in I, and 4.6±0.1 in C pigs, p<0.0001). Commercial yield (%) was higher in IE and I groups (48.9±0.3 in IE, 48.8±0.3 in I, and 46.6±05 in C pigs, p<0.001), mainly due to their higher proportion of untrimmed ham. The opposite happened with the fat cuts (%) (24.7±0.4 in IE, 25.0±0.4 in I, and 28.7±0.3 in C pigs, p<0.0001), due to a lower proportion of belly and backfat cuts in IE and I groups (p<0.001 and p=0.002 respectively). ZP fat depth and average backfat thickness were also lower in IE and I groups than in C group (p<0.0001). Overall, these data show that the experimental diet had no effect on growth and carcass traits of intact AL pigs when compared to the ones obtained in intact AL pigs consuming commercial diets. On the other hand, intact AL pigs raised outdoors reached slaughter weigh faster and produced leaner carcasses than castrated ones. Further studies will test the effect of the experimental high fibre feed on pork boar taint and meat quality of intact AL pigs raised outdoors.