| Forage source in total mixed ration of lactating cows are maily crop straw(corn stover or rice straw),Chinese wild ryegrass hay,whole corn silage and alfafa hay in China.There are significantly differences for fatty acid content and fermentation kinetics.However,they have not been clear the effect of different forage combination on rumen fermentation kinetics and microbial community structure,fatty acid metabolism regulation in rumen and intestine,milk fatty acid profile and transfer efficiency of linoleic and linolenic acid from feed to milk.In this paper,the main forage source in China,corn stover,rice straw,Chinese wild ryegrass hay,whole corn silage and alfafa hay,used as the forage composition in total mixed ration to study ruminal fermentation kinetics,rumen microbial community structure,digestive tract and milk fatty acid profile,and to further research fatty acid metabolism regulation and their correlations.The first part was to determine the effect of different forage combination of total mixed ration on ruminal and milk fatty acid profiles.A 5 x 5 Latin square experiment was designed and five TMRs were formulated in fixed ratios of concentrate to forage of 61:39.The combination treatments on dry matter basis were as follows:390 g/kg of corn stover dry matter(TMR1);195 g/kg of corn stover DM and 195 g/kg of ensiled corn stover(TMR2);195 g/kg of ensiled corn stover and 195 g/kg of Chinese wild ryegrass(TMR3);195 g/kg of Chinese wild ryegrass DM and 195 g/kg of whole corn silage(TMR4);and 134 g/kg of Chinese wild ryegrass plus 128 g/kg of whole corn silage plus 128 g/kg of alfalfa hay(TMR5).The result showed that NDF:NFC of the TMRs was decreased from 1.52 to 0.74.and linearly increased the dietary TFA,C 16:0,C18:2n-6 和 C18:3n-3 intake(P<0.10);and linearly increased the yield of milk fat,C8:0,C10:0,C12:0,C14:0,C16:0,C16:cis-9.C18:2cis-9,12 and C18:3n-3 and transfer efficiency of C18:2n-6 and C18:3n-3(P<0.10);and also linearly increased the rumen content of TFA,C8:0,C11:0,C13:0,C14:0、C14:1cis-9,C15:0,C16:0,C16:Icis-9,C18:0,C18:1cis-9,C18:2n-6 and C18:3n-3(P<0.10).Ruminal content of C16:0,C18:2n-6 and C18:3n-3 was positively correlated with their intake and yield in milk(P<0.10).And content of C11:0,C14:0,C15:0,C16:0,C16:1cis-9,C18:0 and C18:3n-3 in rumen metabolism was affected by the time and the peak values were occurred at the feeding time.The second part was to determine the effect of different forage combination on rumen microbial structure,in vitro gas production kinetics,rumen enzymes activity and fatty acid profile in the rumen.Forty-five multiparous Holstein dairy cows(body weight = 607 士 55.6 kg,days in milk ＝164 ± 24.8)arranged into three groups were designed to investigate.The result showed that a-diversity and relative abundance of pylum and genus were not different among diet treatments(P>0.10);72 h cumulative gas production,average gas production rate(AGPR),in vitro dry matter disappearance(IVDMD),and activity of FAE.CMC and XYL were greater for alfalfa hay treatment comparison with the corn stover and rice straw treatments(P<0.05),whereas,the above results were not different between corn stover and rice straw treatments.Compared with corn stover and rice straw treatments,synthetic odd chain fatty acid in the rumen from propionic and valerate could be greater,and unsaturated fatty acid C18:1trans-11,C]8:1cis-9 and C18:2cis-9,12 content and saturated fatty acid C14:0 and C16:0 content were greater for alfalfa hay treatment.The third part was to determine the fatty acid intake,forestomach and abomasum digesta fatty acid content based on the second part experiment design.The results showed that intake of C18:2n-6 and C18:3n-3 was the greatest for alfalfa hay treatment,and C18:1cis-9,C18:2n-6 and C18:3n-3 intakes were the lowest for corn stover treatment.Content of fatty acid in forestomarch and abomasum was greater for alfalfa hay treatment than that of corn stover and rice straw treatment,and content of TFA and some saturated fatty acid in forestomarch were greater than those in abomasum,but contents of UFA,C18:1cis-9,C18:2n-6 and C18:3n-3 were greater in abomasum than those in forestomarch.And also found that C15:0,C18:1cis-9,C18:3n-3 in rumen digesta and IVDMD were positively correlated with fermentation parameters(P<0.10).but C16:1cis-9 content was negatively correlated with IVDMD,c and AGPR(P<0.10).Apparent hydrogenation of C18:1cis-9,C18:2n-6 and C18:3n-3 in forestomach was decreased when corn stalk and rice straw treatment were replaced with alfalfa hay treatment and their hydrogenations were greatest for rice straw treatment.The fourth part was to determine the fatty acid profile of duodenum,jejunum,terminal ileum,colon and feces based on the second part experiment design.The result showed that fatty acid content of duodenum was greater than those of other intestine segments and abomasum content for all treatments,and their contents,except C 18:trans-11 were gradually reduced from duodenum to terminal ileum,but fatty acid contents in colon and feces were similar and greater than those in ileum.C15:0 was the main odd chain fatty acid of microorgnisms in duodenum digesta for all dietary treatments,but net flow C15:0 content was greatest for corn stover treatment and the lowest for rice straw treatment.Compared with corn stover and rice straw treatment,apparent digestibility of small intestine of TFA,C16:0,C18:0,C18:1cis-9,C18:ltrans-11,C18:2trans-9,12 and C18:2n-6 was decreased for alfalfa hay treatment.Comparison apparent digestibility of small intestine among C18 unsaturated fatty acid was as follow:C18:2n-6>C18:1cis-9>C18:3n-3>C18:1trans-11>C18:2trans-9,12.There were not differences for fatty acid content changes in large intestine among treatments(P>0.10).The fifth part was to determine the fatty acid profile,glucose,cholesterol and triglyceride content of caudal artery,jugular vain and mammary vein based on the second part experiment design.The result showed that fatty acid content in blood for alfalfa hay treatment was lower than that for corn stover and rice straw treatment,indicating that absorb of fatty acid for alfalfa hay treatment could be lower than that for corn stover and rice straw treatment.The sixth part was to determine the milk production and milk fatty acid profile to further study the correlations of milk fatty acid content with fatty acid intake and fatty acid content of rumen and duodenum digesta based on the second experiment disign.The results showed that milk yield and milk fatty acid yield for alfalfa hay treatment were the greatest as 25.3kg/d and 940g/d respectively,and the lowest for corn stover treatment as 19.3 kg/d and 787 g/d.Medium chain fatty acid content of C8:0,C10:0 and C12:0 were lowest for alfalfa hay treatment as 0.65,2.78 and 3.60%respectively,and they were not difference between corn stover and rice straw treatment.Unsaturated fatty acid of medium fatty acid C14:1cis-9 and C16:1cis-9 were not different among all treatments(P>0.10).C18:0 content was the lowest for alfalfa hay treatment as 9.13%,and the greatest for rice straw treatment as 12.98%;C18:2n-6 and C18:3n-3 content were the greatest for alfalfa hay treatment 3.70 and 0.77%respectively,whereas they were the lowest for corn stover treatment 2.71 and 0.26%.UFA and SFA were not different among all treatments(P>0.10).but their ratio UFA/SFA was the greatest for alfalfa hay treatment as 0.13,and the value was the same for corn stover and rice straw treatments as 0.11.Transfer efficiency of C18:2n-6 and C18:3n-3 were greates for alfalfa hay treatment as 37.10%and 19.81%,and they were the lowest for rice straw as 22.97%and 10.42%.Milk yield of C16:0,C18:0,C18:2n-6,C18:3n-3 and TFA were positively related with their Intake(P<0.05).Contents of some fatty acid of milk were negatively related with rumen acetate and butyrate(r>-0.46;P<0.10).However,positive correlation was occurred between some UFA of milk and rumen odd chain fatty acid(r>0.47.P<0.10).C14:lcis-9 content in milk was positively related with content of C10:0.C11:0.C13:0,C14:1cis-9,C18:2trans-9,12*and C18:2n-6 in duodenum content,and milk C18:1trans-11 was negatively with C 15:0、C16:1cis-9、C18:0、C18:1cis-9、C18:2trans-9,12 and C18:2n-6 content in duodenum.C18:1cis-9,C18:2n-6 and C18:3n-3 in milk were all positively related with C15:0 and C16:0 content in duodenum.Hence,compared with corn stover and rice straw treatment,alfalfa hay treatment was benefit for transfer efficiency from feed to milk of C18:2n-6 和 C18:3n-3.According to the above experiments,alfalfa hay and whole corn silage are the main sources of C18:2n-6 and C18:3n-3,and increased their content and yield in milk.So,alfalfa hay and whole corn silage combination was a strategy for increasing the milk C18:2n-6 and C18:3n-3 content and yield and the above results provide theoretical and scientific basis for optimizing the composition of roughage to regulate milk fatty acid composition in the future. |
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