不同收割时间和收割高度对全株小麦发酵营养价值和奶牛生产性能的影响

Effects of different harvest time and cut length on the fermented nutritive value of whole crop wheat and production performance of daily cows

本研究开展了3个试验来评估影响全珠小麦发酵营养价值的因素及其对奶牛产奶量的影响。试验1:选择两个不同收割时间(成熟度)的全珠小麦(低淀粉和高淀粉)进行发酵,干物质含量分别是29.5%和37.0%,淀粉含量分别是5.0%和22%。90头早期泌乳奶牛被分成3组,分别饲喂低淀粉、高淀粉和青贮草粉。结果发现,各组日粮对产奶量无显著影响(P>0.05),但低淀粉日粮组显著降低了奶中蛋白含量(P<0.05),较高淀粉组显著提高了血浆尿酸含量(P<0.05)。试验2:90头早期泌乳奶牛饲喂3种日粮:发酵高秸秆长度收割的全珠小麦+淀粉浓缩物或纤维浓缩物或发酵矮秸秆长度的全珠小麦+纤维浓缩物。整个试验期间各组对奶牛产奶量、奶成分、体况评分均无显著影响(P>0.05)。在哺乳期第10周,饲喂发酵高秸秆全珠小麦+淀粉浓缩物或发酵矮秸秆全珠小麦+浓缩纤维的奶牛血浆游离脂肪酸浓度较低。试验3:评估了青贮草粉、发酵高秸秆和矮秸秆全珠小麦的营养价值。青贮草粉的消化率显著高于发酵全珠小麦饲料,其中纤维组分的消化率最高(P<0.05)。3种发酵全珠小麦日粮的淀粉消化率均较高,平均为0.96 kg/kg,但不同秸秆长度之间无显著差异(P>0.05)。结果表明:发酵的全珠小麦与优质青贮牧草对奶牛产奶量无显著影响,成熟后期的收割全珠小麦发酵后对产奶量几乎无影响,但可以提高奶中蛋白含量。发酵全珠小麦的秸秆切割高度对表观消化率无显著影响。

This study conducted 3 experiments to evaluate the factors affecting the nutritive value of fermented whole crop wheat(WCW)and milk production in dairy cows.In trial 1,WCW was harvested at one of two maturities:at a dry matter content of 29.5%and 37.0%,starch contents of 5.0%(low starch,LS)and 22%(High starch,HS).A total of 90 early lactation dairy cows were allotted to 3 groups and fed either LS,HS or grass silage.There was no significant effect among the groups on milk production(P>0.05),while cows fed the low starch WCW had the lowest milk protein concentration(P<0.05).Plasma urea levels were significantly lower in cows fed the HS goup diet compared with the LS group diet( P<0.05).In trial 2,ninety early lactation dairy cows were fed three dietary treatments:WCW harvested at a long straw length and supplemented with either a starchy concentrate(LW)or a more fibrous concentrate(LF)or a short straw length and supplemented with a fibrous concentrate(SF).There was no significant effect of dietary treatment groups on milk production,composition or body condition score over the experimental period(P>0.05).The lower plasma free fatty acid concentration in cows fed LW or SF during week 10 of lactation phase.In trial 3 the apparent digestibility of the grass silage,long straw whole crop wheat or short straw WCW fed was determined.Digestibility coefficients of the grass silage were significantly higher than those of any of the WCW forages,especially for the fiber fractions(P<0.05).The digestibility of starch was high in all three WCW treatments and averaged 0.96 kg/kg but was not affected by straw length or feeding level(P>0.05).The results indicate that fermented whole crop wheat can provide a comparable milk production to a good quality grass silage and that harvesting at a later stage of maturity had little effect on milk production although milk protein levels tended to be higher.There was little advantage to altering cutting height of fermented WCW on apparent digestibility.