Effect of cocoa husks diet on lipid metabolism and liver composition in fattening pigs during the hot season

Cocoa husks are byproducts from chocolate production, characterized by high contents of proteins, lipids, dietary fibre and antioxidants, polyphenols in particular. The present study evaluated the effect of cocoa husks feeding on lipid metabolism and liver composition in finishing pigs. Eight castrated male Duroc x Large White pigs (135 ± 4.06 kg, mean ± SE) were randomly assigned to one of two groups: CTRL, fed a conventional pelleted diet based on cereals, and COCOA, fed a diet obtained by substitution of 10% of the conventional diet with coarsely-ground cocoa husks. The experimental diets were isoproteic and isoenergetic, but EE (4.53 vs. 3.60 % DM), NDF (14.2 vs. 12.8 % DM), ADF (7.19 vs. 5.03 % DM), ADL (2.22 vs. 1.21 % DM) and total polyphenols (15.4 vs. 8.18 g/kg DM) were higher in COCOA than CTRL diet. The trial was conducted during the hot season (T = 27.1 ± 2.49 °C; Ur = 65.0 ± 4.65 %) and lasted 6 weeks, after which blood samples were taken before the first meal of the day, and analyzed for lipid parameters. Pigs were then sent to the slaughter house, where body and liver weights were recorded and liver samples were collected and analyzed for composition. Obtained data were analyzed by one-way ANOVA. Consumption of cocoa husks for 6 weeks reduced (P<0.01) by 10 % DM and energy intake, but had no effect on body and carcass weights and hot dressing percentage. Cocoa husks diet increased plasmatic level of HDL cholesterol (38.5 vs. 25.9 mg/dL, SE=5.34, P<0.05), without affecting total and LDL cholesterol. In humans, increased HDL cholesterol is associated with reduced risk of cardiovascular diseases. The intake of polyphenols has been shown to increase plasma HDL cholesterol in both humans and animals, but the mechanism by which polyphenols stimulate HDL cholesterol synthesis by the liver remains unclear. Cocoa husks feeding did not affect liver cholesterol, but reduced liver weight (1634 vs. 1833 g, SE=88.5, P<0.05) and liver content of soluble protein (66.7 vs. 84.8 mg/g, SE=4.43, P<0.01), DNA (3.20 vs. 4.74 mg/g, SE=0.34, P=0.01) and glycogen (24.6 vs. 88.4 mg/g, SE=10.7, P=0.01). By contrast, cocoa husks increased liver ether extract (15.1 vs. 11.8 mg/g, SE=1.13, P=0.05). Previous studies showed that liver weight decreases in pigs exposed to high/discomforting temperatures, in order to reduce endogenous heat production. For the same purpose, animals decrease protein synthesis and store energy in the form of fats, because protein synthesis is energetically expensive and largely contributes to total heat production, whereas fat deposition is a more efficient and less thermogenic process. This leads to a shift toward the use of carbohydrates as energy substrate and a consequent reduction in glycogen storage in the liver. Results suggest that, during the hot season, cocoa husks diet may foster liver metabolism, in order to promote animal coping with environmental conditions. This hypothesis is supported by the fact that COCOA pigs needed less feeding to reach similar body and carcass weight of the CTRL ones.