Effects of different processing techniques of palm kernel cake on processing quality of pellet feed, nutrient digestibility, and intestinal microbiota of pigs

The present study was conducted to investigate the effects of extrusion, fermentation, and enzymolysis of palm kernel cake on processing quality of pellet feed, nutrient digestibility, and intestinal microbiota of pigs. First, the pretreatment parameters of extrusion, enzymolysis, and fermentation of palm kernel cake were optimized. Then, PKC after three processing techniques were used to prepare pellet feed. A total of 160 crossbred piglets (Duroc × Landrace × Yorkshire) with an average body weight of 28 ± 0.5 kg were used in an 8-wk feeding experiment. Pigs were randomly assigned to five treatments with four replicates per treatment and eight pigs per replicates. The five experimental groups were as follows: basal diet group (whole corn-soybean meal), 10% PKC group (PKC), 10% extrusion PKC group (PPKC), 10% enzymolysis PKC group (EPKC), and 10% fermented PKC group (FPKC), respectively. At the end of the experiment, four pigs from each treatment (randomly collected one pig per pen) were sacrificed by administering a pentobarbital overdose, the gut and blood samples were collected for the quantification analysis of microbiota, hematological parameters, and apparent total tract nutrient digestibility. The results showed that all three processing techniques significantly decreased the contents of crude fiber of PKC (P < 0.01), pulverization rate (P < 0.01), powder content (P < 0.01), and increased the hardness and gelatinization starch of pellet feed (P < 0.05) compared to PKC group. In addition, PPKC significantly improved the dry matter, crude protein, and ether extract content, blood indices and average daily feed intake compared to PKC group (P < 0.01), while the parameters were similar among FPKC, EPKC, and control group (P > 0.01). Furthermore, all three processing techniques significantly increased the Lactobacillus and decreased the Escherichia levels in feces or gut compared to PKC. Collectively, extrusion, fermentation, and enzymolysis of PKC had positively enhanced the pellet quality, growth performance, nutrient digestibility, and gut microbiota, extrusion exhibited a superior feeding effect compared to fermentation and enzymolysis.Palm kernel cake (PKC) has lower nutritional value compared with soybean meal, cottonseed meal, and rapeseed meal, but its cost advantage is great, and it has been gradually used in the ruminant feeding. Due to its high crude fiber content, the processing technique applied to the PKC has a significant impact on its effectiveness. However, the different processing techniques of PKC on pellet quality, and performance of pigs have been poorly reported. The present study was conducted to investigate the effects of extrusion, fermentation, and enzymolysis pretreatment of PKC on processing quality of pellet feed, nutrient digestibility (in vivo), and intestinal microbiota of growing–finishing pigs. This study provides the optimal processing parameters of the three processing techniques, and demonstrated that PKC after processing could significantly improve the pellet quality, performance, and intestinal microbiota of growing–finishing pigs, while extrusion exhibited a superior feeding effect compared to fermentation and enzymolysis.