| This study com silage and rumen protected fat were selected to regulate the low and high energy level, ground com and steam-flaked com were used as different com processing based on com stover for the main forage resources in 2*2 factorial experiment. Diets were com stover and ground com for LEGC; Com stover and steam-flaked com for LESFC; Com stover, ground com, com silage and rumen protected fat for HEGC; com stover, Steam-flaked com, com silage and rumen protected fat for HESFC. Though established three trials at the follows:CNCPS system, in vitro gas production and animal feed test to evaluate the effects of different energy level and com processing on lactation performance of dairy cows.Trial 1 This part was to evaluate the nutrition level of 4 diets which combined by different material in CNCPS system. The result showed that CNSC, CA and CB1 of com silage were higher than com stover,CB2 and CC of com silage were lower than corn stover; CNSC, CA and CB1 of steam-flaked com were higher than ground com. Therefore, high energy diets which combined the com silage and com stover have more degradable carbohydrate than low energy. CB1 of steam-flaked com was higher than ground com.Trial 2 The experiment was designed to research the effect of different energy level and com processing diets on rumen fermentation parameters in vitro.3 Holstein cows fitted with permanent ruminal cannulas were selected as fumenfluid donor animal, combined the dynamic gas production real-time recording technology, recorded 48 h cumulative gas production and fermentation kinetic parameters, analyzed rumen fermentation indexes. The result demonstrated that theoretical maximum gas production,48 h total gas production, dry matter degradability(DMD) of high-energy diets were higher than the low energy (P<0.05), acetate and propionate of high-energy were greater than the low-energy in ground corn(P<0.05). Under the same energy level,48 h total gas production (GP) deal with steam-flaked com were higher than ground com (P<0.05) just under low-energy level, total volatile fatty acid(TVFA) and propionate of Steam-flaked com were higher than ground corn(P<0.05). Correlation between different diets chemical compositions and fermentation parameters in vitro analysis showed that 48 h total gas production was a significant negative (P<0.05) related to neutral detergent fiber (NDF), both had a significant positive correlation (P<0.05) to neutral detergent soluble (NDS), non-fiber carbohydrate (NFC) and NDS/CP. Steam-flaked corn and high-energy level diets which increased the 48 h total gas production in vitro fermentation. Steam-flaked corn improved the ruminal fermentation more evidently in low-energy level.Trial 3:This part was to evaluate the effect of different energy level and corn processing diets on total-tract apparent digestibilities and lactation performance though animal feed test. Eight multiparous Holstein dairy cows were randomly assigned to 2 of 4 treatments feeding the above 4 diets,and were used in 4 replicated 4*4 Latin squares with 21-d periods, with the first 14-d for adaptation, the last 7-d for taking samples about TMR(Total Mix Ration) and ort diets, milk sample, total feces lasted three days. Beside, taken milk sample two times per week and recorded milk yield per day. The result showed that DM.OM and CP of dry matter intake were highly significant higher in cows fed diets of high energy than diets of low energy (P<0.01). DM,OM,CP,NDF and ADF of total-tract apparent digestibilities in high energy were highly significant higher than low energy (P<0.01). Under low energy level, OM and CP of total-tract apparent digestibilities in steam-flaked corn were highly significant higher than in ground corn (P<0.01). Milk yield, milk protein content and protein percentage were highly significant higher in high energy diets than in low energy(P<0.01),milk fat was highly significant lower in high energy diets than in low energy (P<0.01); Under the low energy, fed steam-flaked corn with highly significant higher milk yield, milk and protein percentage than in ground corn (P<0.01).It is indicated that supplement energy in diets based on corn stover as the main roughage source could improve lactation performance; steam-flaked corn substituted with ground corn could improve lactation performance in low energy. |
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