Effect of dietary regimen and of feeding maltodextrins and dextrose on meat and fat quality of immunocastrated pigs

This research aimed to verify the effects of restricted vs ad libitum feeding and of the dietary inclusion of maltodextrins (M) and dextrose (D) on the qualitative traits of muscle longissimus dorsi (LD) and on fatty acid (FA) composition of backfat lipids of immunocastrated intermediate pigs. To this goal, 36 male pigs (Italian Duroc x Italian Large White) were used. The animals, after having received the second immunocastrating injection at 162 days of age, had been allocated for 5 weeks, till slaughtering (144.51 ± 9.70 kg live weight (l.w.)), to one of the three experimental dietary treatments: basal diet given either ad libitum (CL), or restricted at 7.5% l.w.0.75 (CR), or with M and D (3.5% + 3.5%, balanced for energy and protein levels) provided ad libitum (MD). At slaughter, a sample of LD muscle and backfat were collected from each left-half carcass, at the last rib level. At 24h post mortem on the LD samples, pH, colour (CIEL*a*b*, 1976) were determined, further, protein (CP) and intramuscular lipid (IMF) contents (on the fresh and cooked muscle), drip and cooking loss, oxidative stability (TBARS) and tenderness (WBSF) were measured. Moreover, FA composition of backfat was analyzed. The data were submitted to ANOVA with the dietary treatment as independent variable. The two degrees of freedom of the treatment effect were split up a priori in two orthogonal contrasts: CR vs the average of CL+MD and CL vs MD. The CR pigs, compared with ad libitum subjects, exhibited lower IMF (P<0.05), both in the fresh (2.75% vs 3.41%) and cooked muscle (3.83% vs 5.15%), higher CP in the fresh muscle (24.04% vs 23.36%, P<0.05) and higher Hue value (P<0.05), indicating a slightly decoloured meat. Indeed, CR group showed a higher content of polyunsaturated FA (15.50% vs 13.23%, P<0.01) and a lower content of saturated FA (41.46% vs 42.91%, P<0.05) in backfat lipids. The feeding regimen did not affect pH, drip loss, cooking loss, TBARS and tenderness of LD muscle. No difference was found between CL and MD pigs, except for the ω-6/ω-3 ratio in backfat lipids, lower in MD (15.54 vs 16.70, P<0.01). Thus, in our experimental conditions, the dietary inclusion of M and D did not markedly affect meat quality characteristics and the FA composition of backfat of immunocastrated intermediate pigs fed ad libitum, whereas the dietary regimen exerted a considerable influence, especially on CP and IMF contents of LD and on lipid FA composition of subcutaneous adipose tissue.