| With the development of livestock industry, rice(Oryza sativa L.) straw as roughage to increase feed production in paddy field to solve the shortage of feedstuffs was needed in southeastern China. The objective of this study was to reveal the dynamics of feeding value related traits of rice straw during late growth period and the effects of applying gibberellic acid (GA) after anthesis and different cutting heights on the feeding value of rice straw.A set of111recombinant inbred lines (RILs)(F6/F7) rice population which were derived from a cross of’Nekken2’X’Gaya’and their parents were employed in2005and2006, and eight rice varieties in Jiangsu area (Liangyou108, Huaidao6, Nanjing43, Nanjing44, Wuyunjing7, Yangfujing8,86you8, Xudao3) in2008were employed to investigate the feeding value related traits of rice straw among different varieties:in vitro dry matter digestibility(IVDMD), the content of nonstructural carbohydrates (NSC), acid detergent fibre (exclusive of residual ash, ADFom) and crude ash (CA) in dry matter of rice straw. The plants were cultivated in experimental field of Jiangsu Academy Institute under common management of Jiangsu area. The results indicated that differences of IVDMD, NSC, ADFom and CA among varieties were significant(p<0.01); IVDMD positively correlated with the content of NSC(p<0.01), and negatively correlated with the content of ADFom and CA(p<0.01).Eight rice varieties in Jiangsu area (Liangyou108, Huaidao6, Nanjing43, Nanjing44, Wuyunjing7, Yangfujing8,86you8, Xudao3) in2008, four rice varieties in Jiangsu area (Liangyou108, Huaidao6, Nanjing43, Nanjing44) in2009and2010were employed to investigate the changes of the content of NSC, crude protein (CP), hemicelloluse, ADFom and CA in dry matter of rice straw from weeks1to5after anthesis. The plants were cultivated in experimental field of Jiangsu Academy Institute under common management of Jiangsu area, and were sampled from weeks1to5after anthesis in2008,2009and2010, and the content of NSC, CP, hemicellulose, ADFom and CA in tillers (panicle removed) were determined. The content of CP in tillers was assayed in2009and2010. The results showed that the content of NSC decreased sharply from week1to3, and increased to week5after anthesis, and the rebounding rate of NSC (NSCRR) among varieties was different; the content of CP decreased from week1to5after anthesis; hemicellulose content in week5kept at an approximate level with that of week1after anthesis; ADFom and CA content kept at a constant level from week1to5after anthesis.In2009and2010, NSC, CP, hemicellulose, ADFom and CA in stems(plus sheathes) and leaves were assayed. NSC content in stems was higher than in leaves in week1and2after anthesis, and was lower than in leaves in week3after anthesis, and was higher than in leaves in week4and5after anthesis again. CP and hemicelloluse content in leaves were higher than in stems from weeks1to5, while ADFom and CA content were lower than in stems from weeks1to5. From week1to2after anthesis, starch was the main component of NSC, however, WSC was the main component of NSC from week3to5after anthesis.Three rice varieties in Jiangsu area (Nanjing46, Nanjing43and Huaidao6) in2009and four rice varieties in Jiangsu area (Liangyou108, Huaidao6, Nanjing43and Yangfujing8) in2010were employed to investigate the effects of applying GA after anthesis on the feeding value of rice straw. The plants were cultivated in experimental field of Jiangsu Academy Institute under common management of Jiangsu area. They were applied15,30,45g/hm2GA on the15th day after anthesis in2009, and applied15,30,45g/hm2GA on the1st day,7th day,15th day after anthesis in2010. At harvest, the content of NSC, CP, hemicellulose, ADFom and CA in dry matter of rice straw were assayed in two years. In2010, the area of green leaves per tiller and the SPAD of green leaves were assayed. The results in2009showed NSC and CP content in rice straw were increased by applying GA on the15th d after anthesis. The results in2010showed that applying GA after anthesis on the1st,7th and15th d with3different concentrations could all improve the feeding value of rice straw by increasing the content of NSC and CP in rice straw, especially on the15th d with45g/hm2GA.In2010, the rice straw were harvested at10cm,20cm and30cm cutting heights, and were silaged with application of lactic acid bacteria (105cfu·g-1,fresh weight). The results indicated that the content of NSC and ADFom in rice straw decreased with the increasing of cutting height; CP content in rice straw increased with the increasing of cutting height. The content of NSC and CP in rice straw before silage were positively correlated with the fermatation quality and feeding value of rice straw silage. In conclusions, the differences of feeding value of rice straw among varieties were significant; NSC content was positively correlated with the digestibility of rice straw; NSC content in rice straw decreased from week1to week3after anthesis, then increased to week5after anthesis, and NSCRR among different varieties was different; applying GA after anthesis especially on the15th day after anthesis with concentration45g/hm2could significantly increase the NSC and CP content in rice straw, thus improving the feeding value of rice straw; CP increased with the increasing of cutting height and ADFom decreased with the increasing of cutting height, so increasing cutting height could also improve the feeding value of rice straw. The content of NSC and CP in rice straw before silage were positively correlated with the fermentation quality and the feeding value of rice straw silage. |
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