Effect of low-protein diets on carcass traits and ham quality of heavy pigs

A trial was conducted to evaluate the effect of low-protein diets on carcass traits and ham quality of heavy pigs. A total of 160 ani- mals, divided in two cycles (80 individuals per cycle), were blocked by weight in a randomized block design (10 pigs per pen and 2 pens per dietary treatment). Four iso-energetic diets (ME= 12.9 MJ/kg) were formulated to contain 14.2, 13.2, 11.9, and 11.4% of crude protein (CP) and 45.8 g of lysine per kg of CP, achieved by a progressive replacement of soya-bean meal with wheat grain. Animals were slaughtered at 9 months of age (aver- age BW of 168.9±9.0 kg) in the same abattoir and on a single day. During the first hour after slaughter, hot carcass weight was recorded and all carcasses were dissected into typical commer- cial cuts. Carcass yield (%), backfat (mm), lean (%) and fat cuts (%) were measured. After the 24-h chilling period, fresh hams were trimmed to produce the typical round-shape of San Daniele ham. At the end of the trimming line, hams were weighed and evaluated for overall fatness and marbling. All left hams were then cured according to the San Daniele ham procedure. Measures of ham quality traits were: fat covering measured by ultrasound (mm), iodine number, initial weight (kg), intermedi- ate weight (kg) and final weight (kg) after the ripening process. All traits were analyzed by ANOVA. No significant effects due to the treatment were observed on carcass traits except for the inci- dence of lean cuts: carcasses from pigs fed with lowest CP had lower incidence of lean cuts than carcasses from pigs fed highest CP ration (61.3% vs 62.3%, respectively; P<0.05). Backfat was higher for pigs fed with low than with high CP rations (32.1 mm vs 27.7 mm, respectively; P<0.05). Results suggest that pigs can be fed with 11.4% of CP without detrimental effects on carcass traits and ham quality.