添加剂对甘肃省高寒牧区不同刈割期小黑麦青贮饲料营养品质和青贮品质的影响

Effects of different additives and cutting dates on nutritional and silage fermentation quality of Triticale silage in an alpine pastoral area of Gansu Province

用甘农2号小黑麦于2017年在甘肃省甘南州合作市筛选小黑麦青贮的最佳刈割期和青贮添加剂,旨在丰富该地区牧草饲喂方式,为科学应用小黑麦提供技术支持。试验设2个因素,分别为小黑麦刈割期(A1:抽穗期;A2:开花期;A3:灌浆期;A4:乳熟期;A5:蜡熟期)和添加剂种类[B1:Sila-Max;B2:Sila-Mix;B3:CK(不添加)]。通过评价不同刈割期和添加剂间青贮饲料营养品质的差异,结合TOPSIS法进行综合评价,结果表明:随小黑麦的生长发育,CP含量逐渐降低,各刈割期小黑麦的WSC含量普遍较高且乳熟期达到最高,抽穗期小黑麦的NDF、ADF含量和DMD显著低于其他时期;开花期pH值最低,乳酸含量在灌浆期最高,乙酸含量随小黑麦的生长发育呈下降的趋势;在开花期以后,ADF含量显著降低,DMD显著升高;乳熟期和蜡熟期的丙酸含量显著低于其他刈割期。添加Sila-Max显著提升了小黑麦的青贮品质,提高了乳酸含量,降低了pH值和氨态氮/总氮,尤其在乳熟期和蜡熟期。以收获草产量为目的,则应该在蜡熟期刈割,要获得较优的营养价值以及青贮品质,兼顾较高草产量,则应在乳熟期刈割。

Triticale is a highly versatile cereal forage for grazing,silage,hay or as a cover crop.In the current study,×Triticosecale Wittmack‘Gannong No.2’was used to determine the best cutting period and silage additive for triticale silage in the Hezuo city of Gannan Prefecture,Gansu Province.The experiment comprised a factorial combination of silage additives[untreated control(CK)and two proprietary silage additives(Sila-Max and Sila-Mix released by Ralco Nutrition,USA)]and crop development stage when harvested[head emergence,HE;flowering,FL;grain filling,GF;ripening(milk stage),RM;ripening(wax stage),RW]derived from Lactobacillus and study was conducted during the 2016/2017 growing seasons,with planting in late September.A comprehensive evaluation of data on cutting date and additive effects on silage nutritive(crude protein,CP;neutral and acid detergent fibre,NDF and ADF;dry matter digestibility,DMD;water soluble carbohydrates,WSC)and silage quality parameters(lactic,acetic and propionic acid levels;NH4-N∶total-N)was carried out by the Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)method to estimate the differences of nutritional value and silage quality between different cutting dates and silage additive treatments.Hay yield cut at HE was 7.76 t DM·hm^-2,rising gradually to 19.31 t DM·hm^-2 when cut at RW.With respect to crop growth stage at cutting and silage nutritive value:CP fell gradually from 14.25%cut at HE to 8.66%at RW;NDF was lowest cut at HE(48.34%)and highest at FL(54.74%)with later crop growth stages intermediate;ADF values were similar(-29%)for HE,RM and RW cuts,but rose to 37.09%at GF;WSC values ranged between 4.82%-6.93%at all growth stages except RM(14.27%);and DMD was highest(72.06%)cut at HE,falling to 63.11%cut at FL,then gradually rising to 69.28%at RW.With respect to crop growth stage at cutting and silage fermentation parameters:pH ranged from 3.98 cut at flowering to 4.42 at RW with other values intermediate;lactic acid was highest(48.27%)cut at GF and notably lower than other growth stages(28.05%)cut at RW;acetic acid was highest(13.61%)cut at HE and lowest(5.36%)at RM with other cutting dates intermediate;propionic acid was>5%for HE,FL and GF cuts,but<2%for RM and RW cuts;NH4-N∶total-N gradually increased from 4.64%cut at HE to 5.97%at RW.Comparing silage additives;lactic acid contents averaged across cutting dates were 33.69%,34.59%and 50.18%for CK,Sila-Mix and Sila-Max,respectively,with other parameters showing expected changes linked to the higher lactic acid content in silage with Sila-Max additive.In conclusion,in order to obtain the highest hay yield,triticale should be harvested at RW growth stage,while in order to obtain better nutritional value and silage quality without excessively compromising high hay yield,it should be cut earlier at RM.