Effect Of Corn Oil On Rumen Fermentation And Enteric Methane Emissions In Goats

Objectives:The utilization of corn oil（CO）rich in linoleic acid（LA）and other sources of essential fatty acids（EFAs）by ruminants as a dietary fatty acid supplement is beneficial on microbial fermentative digestion in particular rumen fermentation and methane（CH₄）gas emission.In this study,it specifically investigated the potential effects of corn oil on:rumen fermentation based on the total digestibility,total volatile fatty acids,dry matter disappearance,organic matter digestibility and nutrient degradation;and,the enteric methane emission based on the total gas produced,methane gas emission（output）using gas analyzer,ammonia concentration,dissolved hydrogen and dissolved methane gas output.Methods:Six apparently healthy Liuyang black male native goats（castrated）of approximately 6 months old with an average body weight of 19 kg were used in the study.A50:50 feed concentrate/roughage（2%DM basis,BW）ration was used for the treatment and an additional fatty acid supplement using 3%CO（100%CO pure concentrated,Arawana brand,PSN GB191,Wilmar manufacturing company,Yi Hai Xi Li Wuhan grain and oil industry Co.,Ltd.）.A cross over experimental design was used in the study for 60 days.Two treatment diets were established:T₁ diet is composed of Feed B（98.33%DM,15.82%CP,1.00%EE,16.30 MJ/kg Crude Energy,42.67%NDF,6.95%ADF,3.08%ADL,7.56%Ash,92.56%ODM,and 22.8%Starch）along with 3%CO and untreated dry rice straw（99.17%DM,4.83%CP,1.03%EE,15.99 MJ/kg Crude Energy,74.44%NDF,45.83%ADF,28.61%ADL,10.19%Ash,89.89%ODM,and 0.64%Starch）;and,T₂ diet is composed of Feed A（97.95%DM,16.28%CP,1.01%EE,16.32 MJ/kg Crude Energy,44.59%NDF,7.06%ADF,3.96%ADL,7.90%Ash,92.26%ODM,and 24.2%Starch）along with an untreated dry rice straw.During the course of the study,feeds,rice straw,CO,fecal and urine outputs were sampled prior proximate analysis to measure digestibility.Rumen fluids were sampled in a time point observation（0 hr,2.5 hr and 6 hr after feeding）to investigate the production level of the total volatile fatty acid,ammonia,dissolved hydrogen and dissolved methane by using Gas chromatography（Agilent 7890A,Agilent Inc.,Palo Alto,CA）.Lastly,goats were transferred to a respiration gas chamber to investigate the methane gas emissions during the course of the treatment by using the Greenhouse gas analyzer（GGA-30p）for 48 hrs.Statistical analyses of the differences between groups were performed using Linear Mixed Model using IBM SPSS 19.0 software.Differences were regarded as significant at P<0.05 or highly significant at P<0.01.Result:Mean difference between two treatments on rumen fermentation and digestibility has shown no comparable significance in all parameters except for the starch digestibility（P=0.000）.CO treatment has shown similar effect on rumen fermentation and digestibility to the control.However,treatments on Total volatile fatty acid（TVFA）concentrations have shown a comparable significance where CO treatment has enhanced the effect on the concentration of TVFA in contrast to the control treatment.The concentration of Acetate,Isobutyrate,TVFA,Acetate/TVFA,Isobutyrate/TVFA,Butyrate/TVFA and Valerate/TVFA have shown a highly significant difference at P<0.01;whereas,the concentration of Propionate/TVFA and Isovalerate/TVFA have shown a significant difference at P<0.05.However,CO treatment is significantly higher in the concentration of Acetate,Propionate,Butyrate,Isovalerate,TVFA,Acetate/Propionate and Acetate/TVFA compared to the control.CO treatment has mitigated its’effect on CH4 gas emissions at 48 hr in vivo fermentation in contrast to the control treatment.The digestible energy（DE）,CH₄ emission,dry matter intake（DMI）,digestible organic matter（DOM）,CH₄ emission/gross energy intake（GEI）,CH4 emission/DE and CH₄ energy have shown a highly significant difference at P<0.01;whereas,the GEI and neutral detergent fiber intake（NDFI）have shown a significant difference at P<0.05.In addition,CO treatment is significantly lower in CH4 emission,DMI,NDFI,CH₄ emission/GEI,DOM,CH₄ emission/DE,and CH₄ energy compared to the control.Mean difference between two treatments on in vitro ammonia（NH₄⁺）concentration have shown significant difference at P<0.05.However,the effect of CO is significantly higher compared to the control.Results on the mean difference between two treatments on dH2 and dCH4 gas production（in vitro）in goats have shown a comparable significance where CO treatment has improved the effect on both on dH₂ and dCH₄ in contrast to the control.The extracted gas volume,pH,dH₂ and dCH₄ have shown a highly significant difference at P<0.01 in CO treatment compared to control.Meanwhile,CO treatment has shown no comparable significance on goats’productive performance and has shown similar effect on final BW and gained BW to the control.Conclusions:In this study,the effects of CO were considered positive where TVFA concentration and propionate proportion increased,and NH₄⁺concentration decreased except for the acetate proportion or acetate to propionate ratio.CO tended to reduce acetate proportion and increase the butyrate proportion without decreasing TVFA concentration.The reflected TVFA concentrations and VFA profiles in this study showed that the effects on fermentation depend on the dose of the supplemented CO and that affects individual VFAs differently.