Results (
Thai) 1:
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Materials and methodsExperimental design and animal managementAnimal care and procedures were approved and conductedunder established standards of the College of Animal Science& Technology, China Agricultural University.Eight multiparous Holstein-Friesian cows (568.5±34.7 kgof BW; 164±15 DIM; mean±SD), four of which were fittedwith ruminal cannulas (10 i.d; Bar Diamond, Parma, ID),were fed a series of diets (Table 1) during four successiveperiods in this experiment: an initial baseline period with0% finely ground wheat (FGW, geometric mean particlesizes: 600 μm) and starch provided as ground corn, aslowly fermented starch diet (W0 treatment, Baselineperiod); a second period with 10% FGW, a section of rapidlyfermented starch diet (W10 treatment); a third periodwith 20% FGW, a diet containing a large amount of rapidlyfermented starch (W20 treatment, Challenge period); anda final period in which the W20 diet was amended by replacing10% ground corn with 10% dried, pelleted BP(BP10 treatment). The specific diets were fed sequentiallyto all eight cows over four 17-d periods (12d adaptation,5d of measuring), because previous reports suggest thatSARA was not immediately and easily reversible [15,16],making other experimental designs (e.g., a Latin square)problematic (e.g., carry-over effects).The four diets (Table 1) were formulated to meet or exceedthe NRC [3] guidelines for 600 kg multiparous Holsteindairy cows producing 27 kg of milk/d with 4.0% fat. Thediets were fed as a total mixed ration (TMR) (CAU-mixerwagon model JZC-200, Beijing, China), and the forage componentof the diet was a mixture of corn silage, chopped alfalfahay, and Chinese wild rye. The moisture content ofcorn silage was determined weekly and used to adjustthe ration. During each data collection period, the particlesize distribution of TMR (Table 2) was determinedusing a Penn State Particle Separator (PSPS) asdescribed by Lammers et al. [17].The experiment was conducted at the dairy farm of theState Key Laboratory of Animal Nutrition (Beijing, China).The cows were housed in individual tie-stalls bedded withrubber mattresses, and had free access to drinking waterthroughout the trial. They were fed twice daily, in equalamounts, at 0700 and 1900 h. The diets were fed adlibitum to allow for at least 5–10% orts on an as-fed basis.The cows were milked twice daily at 0630 and 1830 h.
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