Nutritional Evaluation Of Brittle Culm1 Crop Rice As Feed And Its Effect On Growth Performance And Intestinal Microbial Community Of Pigs

The brittle culmI (bc1) rice variety was a fragile rice mutant isolated from an M2 population of indica variety Shuang Ke Zao (wild-type) treated withγ-rays. The bc1 plant has a special physical characteristic with brittle culms and leaves, and can be broken easily by bending. Reduction in the mechanical strength of culms and leaves may reflect alterations in cell wall structure, composition, or fiber length. Brittleness is one of the most important agronomic traits that affect not only grain production but also the usefulness of cereal straws as animal forage. With the aim of explorioting the brittle culm1 whole crop rice (WCR) as feed for growing-finishing pigs, this study mainly includes the following: (1) The nutritional evaluation of bc1 rice straw in terms of morphological fractions, chemical composition and in vitro gas production as well as histological microstructure and fiber structure; (2) The effect of feeding WCR on pigs: the influence was evaluated of feeding WCR substituting wheat by-product or corn but supplementing with soybean oil on performance, nutrient digestibility, intestinal development, carcass quality and fatty acid composition of growing-finishing pigs; (3) The intestinal bacterial community of pig fed WCR to substitute wheat by-product was analyzed. The results obtained are as follows:1. The comparison was made between wild and gene mutant variety bc1 rice straw harvested at four different growth stages in terms of morphological proportion, chemical composition and in vitro gas production. Both varieties were harvested on day 73, 95 (anthesis), 105, and 116 (physiological maturity) of growth post-sowing, designated as Cut 1, Cut 2, Cut 3 and Cut 4, respectively. During the growing stage, the bc1 variety had significantly higher proportion of stem, but lower proportion of leaf blade than the wild. The rice straw and straw fractions for bc1 variety were significantly lower in acid detergent fiber and ash contents, and higher in lignin (pm) and crude protein contents than those for wild variety. The bc1 rice straw was significantly higher in gas production rate, but was lower in potential gas production and lag time than the wild, with little varietal difference in organic matter digestibility between two varieties. With the increasing harvest date, the lignin content increased, while the crude protein content decreased for both rice straws. No drastic variation was showed on gas production and organic matter digestibility of rice straw near physiological maturity from Cut 3 to Cut 4. The neutral detergent fiber and silica insoluble in acid detergent and neutral detergent were lower for stem than those for the other fractions. The gas production and estimated organic matter digestibility of the stem were significantly higher than those of other straw fractions. The result indicated that the gene mutant led to a reduction in gas production and an increase in gas production rate. The physiological maturity stage was optimal harvesting time for both grain and straw production.2. The histological microstructure and fiber structure of stem were analyzed by scaning electronic microscopy (SEM) and atomic force microscopy (AFM), respectively. For bc1 stem, the sclerenchyma was thin, phloem and xylem of vascular tissue was incompact, and parenchyma was attenuated and irregular. The cuticle micro-hair scattered on the epidermis, wart-like structures was big and grey, papilla was relative bigger, took on a cluster and lined like a strip along longitude regularly. AFM image of bc1 stem fiber structure showed that the micro-fibril bundles had inhomogeneous diameter (about 427 nm), resolved zigzag structure and held incompactly each other. From histological microstructure and fiber structure of stem, it is inferred that the bc1 rice straw is easier to be attached and digested by the microbe. For wild stem, the epidermis was distinct, sclerenchyma was heavily thickened, phloem and xylem of vascular tissue were tight and parenchyma had regular shape. The cuticle micro-hair cell was exiguous, wart-like structures was small and bright, and papilla took on a cluster and lined along longitude. AFM image of stem fiber structure for wild variety showed that the micro-fibril bundles had uniform diameter (about 313 nm) and resolved fibrillar fine structure and hold tight each other.3. A feeding trial was conducted to determine the effect of feeding diets with WCR to replace wheat by-products on growth performance, nutrient digestibility, intestinal tract development, carcass traits and meat quality of growing-finishing pigs. Fifty-four female pigs (Duroc), with initial mean weight of about 29 kg, were divided into three equal groups and the dietaries were infused with 0, 10 or 20% WCR, respectively. During the growing period, the pigs fed 10 or 20% WCR diet were not significantly different in feed intake, average daily gain and gain-to-feed ratio from those on the control. During the finishing period, the feed intake and average daily gain of pigs fed 20% WCR diet was significantly lower than that of animals fed the control (P<0.05), while the pigs fed 10% WCR diet were not significantly different in these two parameters from those on the control, nor was there significant difference in gain-to-feed ratio among pigs fed different diets. The digestibilities of nutrients in 10 or 20% WCR diets were lower than those of the control during the growing period, while little difference was found in the digestibility of nutrients except NDF between WCR and control diets during the finishing period. The dressing percentage and mean backfat thickness of pigs fed 10 or 20% WCR diet were lower than those of pigs on the control, whereas the lean percentage and loin eye area were superior in the WCR diets to those in the control, though the differences were not statistically significant. The longissimus muscles of pigs fed 20% WCR diet had higher protein and lower fat content (P<0.05) and higher 24 h postmortem pH value (P<0.05) than that of control. There was no significant difference in drip loss and marbling and color scores for longissimus muscles among pigs fed different diets. With the inclusion of WCR in the diet, the pH value in distal colon significantly decreased. The villus height of colon for pigs on 10 or 20% WCR diet was significantly lower than that of pigs on the control diet.4. A second feeding trial was conducted to determine the effects of feeding WCR supplemented with soybean oil to replace corn on growth performance, serum parameters, carcass quality and fatty acid composition for growing-finishing pigs. Forty-eight pigs (Duroc×Landrace×Yorkshire, 36 kg) were randomly assigned to four treatments with three replications each. The diets included the ground WCR at levels: 0, 8, 12 or 16%, accordingly supplemented with soybean-oil at levels: 0, 2, 3 and 4 %, and designated as control, W8O2, W12O3 and W16O4, respectively. All pigs were slaughtered at about 90 kg to determine carcass characteristics and meat quality. In growing period, the daily feed intake was significantly lower for pigs fed the diets containing WCR than for those on the control. The pigs on W16O4 diet had significantly lower average daily gain than those in other treatments (P<0.05). The feed conversion ratio was significantly lower in pigs on W8O2 or W12O3 diets than on the control (P<0.05). No significant difference was found in daily feed intake, average daily gain and feed conversion ratio among pigs on different diets in finishing period (P>0.05). In overall period, the daily feed intake of pigs on diets containing WCR was significantly lower than that of pigs on the control (P<0.05). The average daily gain and feed conversion ratio showed no significant difference among different treatments (P>0.05). Concentrations of total protein, glucose, urea nitrogen, triglycerides, total cholesterol and alanine aminotransferase in serum showed no significant differences (P>0.05) among pigs on different diets. The carcass weight of pigs on W16O4 diet was significantly lower than that of pigs on control and W12O3 diets (P<0.05). No significant difference was found in other carcass characteristics among different treatments (P>0.05). The water holding capacity of loin muscle was significantly lower for pigs fed diets containing WCR than for those on the control (P<0.05). There were no significant differences in meat color, marbling, pH and cooking loss among pigs on different diets. The contents of polyunsaturated fatty acid (PUFA), PUFA n-6 and PUFA n-3 in loin muscle and backfat of pigs fed on diet with WCR and soybean oil were significantly higher than those of pigs on control (P<0.05), but the contents of saturated fatty acid and monounsaturated fatty acid were lower for the formers than the latter. It is inferred that the WCR could be used as feed ingredient for growing-finishing pigs with soybean-oil as energy supplement, and the content of polyunsaturated fatty acid in carcass increased with the inclusion of WCR and soybean oil.5. The effect of feeding britte culm1 whole crop rice for growing-finishing pigs at three levels 0 (Control), 10 and 20% on bacterial communities in colon content and feces was analyzed using 16S rDNA-based techniques. Amplicons of the V6-V8 variable regions of bacterial 16S rDNA were analyzed by denaturing gradient gel electrophoresis (DGGE), cloning and sequencing. The total number of DGGE bands and Shannon index of diversity for feces samples were higher in the pigs fed WCR-containing diets compared with the control, while a decrease trend was observed in these two parameters for colon content samples with the inclusion of WCR in the diets, although statistical differences were not significant. The similarity indices analysis suggested that two clearly different clusters were present for colon content and feces, respectively. Feeding of WCR induced the presence of special DGGE band with the sequence showing 99% similarity to that of Lactobacillus reuteri (DSM 20016T). The sequences of seven amplicons in total nine clones showed less than 97% similarity with those of previously identified or unidentified bacteria, suggesting that most bacteria in gastrointestinal tract have not been cultured or identified. It is indicated that the diet containing WCR affect the bacterial communities of colon content and feces to some extents, and that feeding of WCR may benefit for health of animal gastrointestinal tracts by inducing the presence of Lactobacillus reuteri.In summary, the brittle culm1 rice straw is prone to be attached and digested easily by the microbe compared with its counterpart. The WCR can be used in growing-finishing diet substituting wheat by-products, and the inclusion of WCR at level 20% in growing period and 10% in finishing period had no adverse effect on performance. In terms of overall period, the performance was ideal for pigs fed diet including 16% WCR with soybean oil as energy supplement to replace corn. The feeding of WCR induced the presence of Lactobacillus reuteri and had a good effect on the intestinal bacterial community to an extent, which benefited the intestinal healthy of pig. The results indicated that the brittle culm1 rice took on the variety characteristic as forage rice. It is an efficient mode to use rice in form of whole for forage rice exploriation and utilization, which will provide a efficient way to solve the shortage of feed resource.