玉米芯与苜蓿、精料配比对饲粮组合效应的影响

Evaluation using a gas production technique in vitro of associative effects on digestibility of corn cob, alfalfa and concentrate in mixed rations

为了探讨玉米芯与苜蓿、精料间不同配比对饲粮组合效应(associative effects, AE)的影响。采用体外产气法测定在精粗比40∶60和30∶70时,精料∶玉米芯∶苜蓿分别为40∶60∶0、40∶45∶15、40∶30∶30、40∶15∶45、40∶0∶60和30∶70∶0、30∶55∶15、30∶40∶30、30∶25∶45、30∶10∶60、30∶0∶70时各饲料组合及各种单独原料分别培养2,4,6,9,12,24,36,48 h的产气量(gas production, GP),培养结束后的上清液及残渣用以测定pH、挥发性脂肪酸(volatile fatty acids,VFA)、氨态氮(NH_3-N)、干物质降解率(dry matter digestibility, DMD)和有机物降解率(organic matter digestibility, OMD),并通过各组合的加权估算值计算出各指标的单项组合效应指数(single factor AE indexes, SFAEI)和综合组合效应指数(multiple-factors AE index, MFAEI)。结果表明:当精粗比为40∶60和30∶70时,玉米芯比例为30、15和10、25、40、55的组在GP、DMD、OMD、NH_3-N、TVFA上显著高于其他组,且有较高的SFAEI (P<0.05,P<0.01),30和10组的MFAEI极显著高于其他各组(P<0.01)。结论:当精料∶玉米芯∶苜蓿为40∶30∶30、30∶10∶60时,饲粮的综合组合效应值最大。

This experiment was conducted to investigate, using an in vitro gas production (GP) technique, the associative effect (AE) when corn cob (CC) was added as a supplement to an alfalfa (A) and commercial concentrate (C) feed mix. A series of rations was formulated with concentrate-roughage ratio (C:R) of either 40:60 (n=5), or 30:70 (n=6). Specifically, the C:CC:A ratios for the 11 ration formulations tested were: 40:60:0, 40:45:15, 40:30:30, 40:15:45, 40:0:60, 30:70:0, 30:55:15, 30:40:30, 30:25:45, 30:10:60 and 30:0:70. Gas production (GP) was recorded at 0, 2, 4, 6, 9, 12, 24, 36, 48 h. After incubation, the incubation fluid and residues were used to determine pH, volatile fatty acids (VFA), ammonia nitrogen (NH3-N), dry matter digestibility (DMD) and organic matter digestibility (OMD). The single factor AE index (SFAEI) was defined as the difference between the observed value and the predicted value for an individual feed fermented alone. Also, the multiple-factor AE indexes (MFAEI) of the 11 rations were calculated. It was found that when C:R was 40:60 those rations with 15% or 30% CC had a higher GP, DMD, OMD, NH3-N, and TVFA, as well as higher SFAEI of GP, DMD, OMD, NH3-N, and total VFA (P<0.05 or P<0.01). When C:R was 30:70, then rations with 10%, 25%, 40%, or 55% CC generally performed well. Meanwhile, the ration formulations C:CC:A of 40:30:30 and 30:10:60 had a significantly higher MFAEI (P<0.01) than other rations. It was therefore concluded that the greatest AE occurred when C:CC:A ratios were 40:30:30 and 30:10:60.