Performance, carcass and ham traits of heavy pigs managed on different targets for age and weight at slaughter

The Italian pig sector, mostly devoted to the production of Protected Denomination of Origin (PDO) dry-cured hams, must comply with technical specifications established by the PDO regulations. Weight and age at slaughter are key husbandry features in such production, with a minimum of 160 kg and 9 months, respectively, which have been established to attain an acceptable degree of maturity of meat. Changes in feeding strategies and in the genetic background of pigs may affect the appropriateness of the standard weight/age target in providing green hams with optimal dry-curing properties. This study investigated the effects of variation in age and/or weight at slaughter on live performance, carcass and green ham traits of finishing heavy pigs. A total of 112 C21 Goland pigs (58 gilts and 54 barrows) of 90 ± 10 kg initial body weight (BW) were allotted to the following groups (2 pens/group): i) pigs fed a ad libitum diet (10 MJ NE and 153 g CP per kg) and slaughtered at 170 kg, regardless of the age (AL170), or at 9 months of age, regardless of the weight (AL9M); ii) pigs fed a restricted diet (10 MJ NE and 122 g CP per kg) to reach 170 kg BW at around 9 month of age, which is the current target for PDO heavy pigs (RE9M); iii) pigs fed a restricted diet (10 MJ NE and 107 g CP per kg) to reach 170 kg around 9.5 months of age (RE9.5M). Feed intake, weight gain, carcass and cuts weights were recorded, and green thighs were measured for subcutaneous fat thickness and scored for ham characteristics. Data were analysed with a mixed model including pen as random effect and sex and group as fixed effects. Weight gain exceeded 0.9 kg/d in AL170 and AL9M pigs, whereas it was 0.74 and 0.64 kg/d in RE9M and RE9.5M pigs, respectively. As a consequence, the target weight of 170 kg was reached after 85, 113 and 127 days in feed for AL170, RE9M and RE9.5M, whereas AL9M reached a final BW of 194 kg. RE9M, the control group for the PDO condition, had feed efficiency comparable to ad libitum fed pigs, carcasses showing the lowest backfat thickness and the greatest incidence of loins and dressed hams, and green hams with the lowest marbling scores and dressing losses. Increasing the age at slaughter decreased feed efficiency and incidence of dressed hams on carcass, and increased marbling score, but not the subcutaneous fat thickness of hams compared to RE9M pigs. Ad libitum fed pigs showed the lowest uniformity in body, carcass and dressed ham weight, and the greatest subcutaneous fat thickness of hams. Beyond performance and carcass traits, manipulating weight and/or age of heavy pigs at slaughter can affect green hams suitability for dry-curing.