Influence of high levels of beet pulp in the diet on endocrine/metabolic traits, slaughter dressing percentage, and ham quality in Italian heavy pigs

Abstract

Seventy two Landrace × Large White barrows were divided into three groups and fed different diets: a control traditional diet based on cereals (C) and two with 15 or 30% dried sugar beet pulp (BP15 and BP30, respectively). Animals weighed 106 kg at start and 167 kg at the end of the experiment. Feeding was restricted (2.5 kg DM/head, on average). The aim of the present experiment was to investigate the influence of high levels of beet pulp in the diet of fattening heavy pigs on some endocrine/metabolic traits, on the slaughter dressing percentage and on some parameters related to meat quality, composition and on the ham quality, after 14 months of seasoning. During the experimental period, jugular vein blood samples were collected from C and BP30-fed pigs and plasma was analysed for several metabolic traits. BP30 diet initially increased the plasma glucose level and decreased free amino acids (P < 0.05), but this difference disappeared at the end of the experimental period, when insulin level was decreased (P=0.06) by beet pulp administration. During the entire period, 30% beet pulp diet increased total protein and albumin levels (P < 0.001) and decreased urea (P < 0.05) without affecting plasma leptin. At slaughter, pigs fed BP30 diet were lighter (P < 0.001) and with a lower dressing percentage (P < 0.001) in comparison with the other two treatments. Pigs fed BP30 diet also had lower ham and loin weights (P < 0.05) (but similar ham and loin percentages) and higher liver weight (P < 0.05), liver/carcass ratio (P < 0.001), gastroin-testinal-tract weight (P < 0.001) and gastrointestinal-tract/carcass ratio (P < 0.001). Pigs fed C diet had a higher dressing percentage in comparison with pigs fed BP15 diet (P < 0.01), but no other significant difference was found between pigs fed diets C and BP15. At slaughter, liver samples were taken from C and BP30-fed pigs in order to evaluate the effect of the diet on liver composition. BP30 diet increased dry liver weight (P < 0.05) and liver fat content (P < 0.01). The iodine value and the fatty acid composition of the backfat revealed no significant difference between pigs fed the control diet and those fed the high fibre diets. Finally, considering the economic importance of ham production, the characteristics of the seasoned hams were evaluated. No difference was observed on ham quality. In conclusion, feeding a diet with a high percentage of dried sugar beet pulp alters protein and energy metabolism and slaughter parameters, without affecting the quality of the seasoned ham.