| Three corn varieties, Xundan 20, Xianyu 335 and Zhengdan 958, which comes from Hebei province, Henan province and Shandong province, were collected to study the nutritional value for dairy cows.The main nutrient content of corns was determined by chemical analysis.The rumen degradation was measured by Nylon Bag technique.The apparent digestibilities of the mian nutrient and bioavailble energy of corns were measured through the digestion trial.Experiment 1: The main nutrient content of different corns was determined by chemical analysis. The results showed that, the whole range of variation of DM, CP, EE, NDF, ADF, Ash, Ca and P in different regions was 83.63%～86.57%, 7.91%～10.41%, 3.39%～4.21%, 10.76%～13.60%, 2.95%～4.63%, 1.17%～1.59%, 0.02%～0.04% and 0.20%～0.31%, respectively. The content of CP, EE, P for Xundan 20, DM, CP, NDF, ADF ,Ash, P for Xianyu 335 and DM, CP, EE, NDF, ADF, Ash, P for Zhengdan 958 in different regions had significant difference(P<0.05). Most of the nutrient content of different varieties in the same area had significant difference (P<0.05), the content of CP for Hebei Xianyu 335 (10.41%) was significant 31.61% higher than Hebei Zhengdan 958 (7.91%) and significant 17.10% higher than Hebei Xundan 20, the content of NDF for Shandong Zhengdan 958 (12.35%) was significant 14.78% higher than Shandong Xianyu 335 (10.76%).Experiment 2: Four healthy ruminally cannulated Holstein cows (average 600 kg) were used, fed at 1.3 times of maintainance requirement.The degradation of different corns at different time points (2, 4, 8, 16, 24, 36 and 48 h ) was determined by the technology of Nylon Bag .The result showed that, the effective degradation of DM, CP, NDF and ADF of corns in different region was 54.72%～66.99%, 39.04%～49.94%, 44.30%～46.17% and 42.32%～46.70%, respectively. The effective degradation of DM , CP for Xundan 20, Xianyu 335 and Zhengdan 958 in different regions had significant difference (P<0.05), the effective degradation of NDF, ADF for Zhengdan 958 and ADF for Xianyu 335 in different regions had significant difference (P<0.05), NDF, ADF for Xundan 20 had no significant difference (P>0.05). The effective degradation of DM and CP in Hebei and DM and ADF in Henan had significant difference (P<0.05), the effective degradation of Shandong had the same trend with Hebei. The effective degradation of DM, CP for different corns in Hebei and Shandong had significant difference (P<0.05), NDF, ADF had no significant difference (P>0.05). The effective degradation of DM, ADF for different corns in Henan had significant difference (P<0.05), CP, NDF had no significant difference (P>0.05). The effective degradation of DM, CP for Hebei Xundan 20, Shandong Xianyu 335 and Hebei Zhengdan 958 was the highest, the effective degradation of NDF for Henan Xundan 20, Hebei Xianyu 335 and Hebei Zhengdan 958 was the highest, the effective degradation of ADF for Hebei Xundan 20, Hebei Xianyu 335 and Hebei Zhengdan 958 was the highest. This experiment had obtained the prediction model of effective degradation and the whole predictive effect was well.Experiment 3:Twenty Holstein cows ,14～16 month-old , average 300 kg body weight,healthy and well-developed, were divided into 4 groups each group with 5 duplicates. The trial corn replaced 20% of the basic ration in the feeding experiment. the apparent digestibility of the main nutrient and bioavailble energy of corn was determined by the methods of collecting whole feces.The result showed that, the apparent digestibility of DM, CP, NDF, ADF, Ca, P and GE for different test diet and corn raw materials was 64.25%～66.41%, 65.35%～67.01%, 47.94%～49.81%, 44.49%～46.03%, 29.25%～32.82% , 66.82%～67.81% and 80.58%～88.68%,70.42%～74.49%, 74.04%～78.67%, 75.22%～79.67%, 63.27%～70.92%, 77.04%～84.37%, 84.74%～88.85%, respectively.The Gross Energy(GE), Digest Energy(DE) and Net Energy for Lactating (NEL)of corns was 18.66MJ/kg～18.94 MJ/kg, 16.00 MJ/kg～16.59 MJ/kg and 8.41 MJ/kg～8.73 MJ/kg, respectively. The apparent digestibility of the main nutrient in Hebei showed significant difference (P<0.05), the apparent digestibility of energy, GE, DE and NEL had no significant difference (P>0.05). The apparent digestibility of the main nutrient and energy, DE and NEL in Henan showed significant difference (P<0.05), except DM and P, DE and NEL of Xianyu 335 was 3.69% and 3.80% higher than Zhengdan 958 (P<0.05), DE and NEL of Xundan 20 was 3.5% and 3.57% higher than Zhengdan 958 (P<0.05), respectively.The apparent digestibility of other nutrient, GE,DE and NEL in Shandong had significant difference (P<0.05), GE of Zhengdan 958 was 1.23% higher than Xianyu 335, DE and NEL of Xianyu 335 was 2.60% and 2.83% higher than Zhengdan 958 (P<0.05), respectively. The growth region had a significant effect on the apparent digestibility of the main nutrient of different corns (P<0.05), had a significant effect on DE and NEL of Xianyu 335(P<0.05), Henan area was 2.41% and 2.46% higher than Hebei, Shandong was 2.35% and 2.46% higher than Hebei, respectively. The growth region had no significant effect on Xundan 20 and Zhengdan 958 (P>0.05). This experiment had obtained three prediction models of NEL and the predictive effect was well (R2 was 0.9720, 0.9716 and 0.9582, respectively). |
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