| The present study was conducted to compare the nutritive values of steam-flaked (SF) maize, wheat and rice (with whole hulls) grains and to provide information about SF-treated wheat or rice as alternative feed sources to maize grain for ruminant animals by analyzing chemical composition, starch gelatinization degree (SGD), in vitro fermentation characteristics, rumen digestion fatures and using methods of CNCPS and PDI system.Expt.1. Intact and steam-flaked grains of maize, wheat and rice (with whole hulls) were analyzed for chemical composition, starch gelatinization degree (SGD) and carbohydrate components to investigate the influence of cereal type and steam-flaking (SF) processing on their nutritive values. The treatments were arranged in a3×2factorial design. Obvious differences (P<0.001) in crude protein, crude fat, crude ash, neutral detergent fiber, acid detergent fiber, neutral detergent insoluble nitrogen and the content of starch were observed among the different cereal types. SGD was significantly increased (P<0.001)by SF processing (55.2,55.2and42.3percent value for maize, wheat and rice, respectively). The content of carbohydrate components was calculated according to CNCPS, non-structural carbohydrates (CNSC) content and medium speed degradation components (CB1) of maize were higher than wheat and rice (with whole hulls), suggesting that maize could provide more available energy in rumen fermentation process.Expt.2. Intact and steam-flaked grains of maize, wheat and rice (with whole hulls) were analyzed for in vitro fermentation characteristics and energy values by using method of Menk et al(1979). The treatments were arranged in a3x2factorial design. Gas production (GP) rate were significantly increased (P<0.001) by SF processing. SF processing also increased (P<0.01) the proportion of propionic acid and decreased the acetic:propionic acid ratio in vitro. Steam flaking also increased organic matter digestibility and the energetic value of the cereal grains (P<0.01), especially rice. The results suggest that it maybe feasible to partially replace maize grain with wheat or rice in ruminant diets, and steam-flaking can significantly improve the nutritional value of wheat and rice grains.Expt.3. Intact and steam-flaked grains of maize, wheat and rice (with whole hulls) were analyzed for degradation rate and degradation parameters by using the nylon bag method. The treatments were arranged in a3×2factorial design. The results show that the rumen effective degradation rate of dry matter, organic matter, starch and crude protein of the grains were:wheat (80.91%,81.34%,87.68%and81.34%)> rice (71.10%,72.84%,84.79%and72.84%)> maize (65.80%,63.99%,74.60%and63.99%). The rumen degradation rate from fast to slow were:rice> wheat>maize. DM, OM, Starch and CP effective degradability of maize were increased by SF processing. SF processing also increased DM, OM, Starch and CP degradation rate of maize and wheat, decreased DM, OM, Starch and CP degradation rate of rice (with whole hulls). Expt.4. Intact and steam-flaked grains of maize, wheat and rice (with whole hulls) were predicted for protein digested in the small intestine (PDI) using the method of Franch PDI system. The treatments were arranged in a3×2factorial design. Results show that PDIA (rumen nondegradable nitrogen from feed) and PDI(50.07and99.97g/kg DM) of wheat were significantly higher (P<0.001) than maize (34.83and55.03g/kg DM) and rice (23.16and46.27g/kg DM).PDI of maize was reduced (P<0.01) by SF processing, while no significant differences were observed between PDI of intact and steam-flaked wheat or rice. Summary:PDI of wheat was higher than maize and rice, steam flaking procesing did not change PDI of maize, wheat and rice.Conclusion:maize can provide more effective nenergy value than wheat and rice, PDI of wheat was higher than maize and rice. Steam-flaking processing effectively improved nutritional value of cereal grains, but degradation rate of maize and wheat were also accelerated, thus increased the risk of rumen acidosis. Opposite effects were observed on rice. Considering the market price trends and the ruminal fermentation characteristics, it is feasible to use steam-flaked wheat and rice grains to partly substitute maize grain in ruminant diet. |
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