| Master the grass advantage forage nutrition dynamic variation of great significance to improve and regulate the nutritional status of livestock,improve grass productivity,the development of China’s northern grassland animal husbandry.In order to provide the basal data for design feeding of ruminants,Three WuZhu MuQin sheep(30±2kg) and Liu-yang black goats(22±1.5kg),fitted with ruminal cannulas for these experiments were conducted to study the nutritional variation of two natural advantages forage(Ｌ. chinensis.M. ruthenicａ) at different growth period in the faiming pastoral zone of the Songnen Plain,ruminal degradation in situ and fermention gas production characteristics in vitro.In Exp1:Effects of different varieties and growth on the forage nutritive value.To quanitify the DM, Ash, CP, NDF, ADF concentrations between L. chinensis and M. ruthenica of different growth(May15, May30, June30, Jul30, August30, and September30,2012). The result showed that the orage nutritive value was significantly affected by varieties, growth, interaction between varieties and growth (P＜O.01).Within the same forage species, the CP, Ash concentration decreased and the ADF, NDF increased with the growth prolonged. Within the same growth, the CP concentration of L. chinensi was lower than M. ruthenica, whereas the Ash,ADF,NDF concentrations of L. chinensi was higher than M. ruthenica.In Exp2:Research on the rumen degradation of different varieties and growth for forage. DM,OM,CP,NDF and ADF of L. chinensis and M. ruthenica which in different growing period were tested to degradation rule by the method of rumen nylon bag. The results as follow:With prolonging growing period,each nutritive indexes of samples were gradually decreaseing in72h. Dynamic degradation model parameters a, b, c and P component were affected by the species of forage, growing were period and both of effects. Effective degradation rate P of L. chinensis and M. ruthenica were on downtrend (P<0.01) by prolonging growing period. But in the same period, each nutritive indexes of M. ruthenica were higher than that of L. chinensis (P<.01). It was indicated the feeding value of M. ruthenica be better than L. chinensis.Exp3:Research on the in vitro fermentation gas production characteristics different species and growth for foeage. The in vitro gas production technique was used to evaluate methane output, the rate of degradation, and fermentation parameters, including volatile fatty acid profile and ammonia N concentrations of72h, between Leymus chinensis and Medicago ruthenica differing in growth.To provide some references for rational used of the the two grass in the production of ruminants. Results showed that forage species and harvest had interactions (P<0.001) on all chemical variables of two forages. The L. chinensis produced more total gas and methane than those of M. ruthenica (P<0.001). Moreover, both total gas (P<0.001) and methane (P<0.01) outputs decreased with harvests prolonged. The forage species or harvests did not affect concentrations of volatile fatty acid, acetate, propionate, and butyrate. However, the concentrations of ammonia N (P<0.05), isobutyrate (P<0.01), valerate (P<0.001), and isovalerate (P<0.01) in M. ruthenica were significant higher than those of L. chinensis. Furthermore, their concentrations were influenced by growth period (P<0.05). In conclusion, M. ruthenica produced less methane than that of L. chinensis,this trend may be related to concentrations and fermentation process of crude protein.The conclusions were as follows:1) The nutritional value of L. chinensis and M ruthenica decreased with lengthening of growth stage,and within the same growth stages nutritional value of L. chinensis was lower than ruthenica.2) According to the change of nutrients variation during different growth stages, rumen degradability and fermention gas production characteristics in vitro,the two forage should be harvested in late July to early August at Changling. |
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