The influence of feeding fresh liquid whey on some blood metabolites, insulin, and cecal fermentations of growing pigs

Two experiments were conducted to measure cecal fermentation and glucose, non-esterified fatty acids (NEFA), urea, and insulin plasma concentrations of growing pigs fed fresh liquid whey. Experiment 1 involved a 24 h in vitro cecal fermentation of a growing pig diet that had been previously predigested to simulate ileal digestion. The residue of the predigested diet was used with or without the addition of fresh liquid whey at 3 ml/g of diet. In Experiment 2, eight growing pigs (average live weight 126 kg) were fitted with a vena cava catheter and fed the same amount of dry matter with 3.2 kg of the same diet used in Experiment I added with 12.81 of water (control diet) or 2.25 kg of the diet added with 12.81 of fresh liquid whey. In Experiment 1, the addition of whey increased the final total gas production by 22%, the maximum rate of gas production by 12%, and the duration of the logarithmic phase by 9%, and decreased the duration of the lag phase (P < 0.05). At 4 h of fermentation, ammonia was higher in vessels containing whey than in control (+ 14%; P < 0.001) but no differences were observed after 8 and 24 h. At 8 h, whey tended to increase propionic acid concentration (+11%; P=0.10) while the acetic to propionic acid ratio was reduced by whey at 4 and 8 h of fermentation (P < 0.05). In Experiment 2, average plasma glucose postprandial concentrations tended to be lower in whey fed animals (-8%; P=0.08). Insulin secretion was not influenced by dietary treatment. Feeding whey reduced average plasma urea (-21%; P < 0.01) and increased average plasma NEFA postprandial concentrations (+29%; P < 0.05). In conclusion, adding fresh liquid whey to pig diets enhanced cecal fermentation and determined significant metabolic changes in pigs, increasing plasma NEFA and reducing plasma glucose and urea. In particular, the lower urea plasma concentrations may indicate that feeding whey reduces intestinal proteolysis and endogenous protein catabolism in pigs. (c) 2006 Elsevier B.V. All rights reserved.