Effect of protein-restricted diet during growing period on performance and carcass quality traits of Duroc x Iberian crossbred barrows under different management conditions.

• Overall growth of Duroc x Iberian pigs was not affected by dietary protein level. • Reducing protein in growing diets had minor effects on meat quality. • Low-protein diets may increase intramuscular fat depending on production system and level of protein reduction. • Production system should be consider when using low protein diets in crossbred pigs. This study investigated the effects of feeding protein-restricted diets during the growing period on performance and carcass quality traits of Duroc (boars) x Iberian (sows) crossbred pigs slaughtered at commercial weight for local pig production. Two trials were conducted in different management conditions, with 28 and 33 barrows, respectively. In each trial, pigs were divided into two dietary groups, one group received a control diet (CD, 16.5 % crude protein, CP) and the other one was fed a protein restricted diet (PRD_1 for Trial 1: 12.4 % CP; and PRD_2 for Trial 2: 10.0 % CP). At 100 kg of body weight (BW), five pigs per group and trial were slaughtered, while the remaining pigs were fattened on a standard finishing diet until reaching 160 kg BW before slaughter. No significant changes in growth, carcass and ham composition or backfat thickness due to decreased protein supply during the growing period were observed. However, the intramuscular fat content increased in Longissimus thoracis et lumborum (LTL) and ham muscles of PDR_2 pigs. Furthermore, the backfat fatty acid (FA) profile presented higher proportion of oleic and monounsaturated FAs in pigs fed PRD diets, while polyunsaturated FA decreased in PDR_2 pigs. The PRD_1 group exhibited higher redness and thawing water loss in LTL, while PDR_2 group showed greater redness, yellowness and thawing water loss values compared to the CD group. Overall, the results indicate that feeding protein-restricted diets during growing period did not have a substantial impact on growth or meat quality. The success of implementing such diets may be influenced by factors such as the protein restriction level and the animal management conditions. [ABSTRACT FROM AUTHOR]