Asian-Aust. J. Anim. Sci. Vol. 22, No. 11 : November 2009

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1 52 Asin-Aust. J. Anim. Sci. Vol. 22, No. : Novemer Conjugted Linoleic Acid in Rumen Fluid nd Milk Ft, nd Methne Emission of Lctting Gots Fed Soyen Oil-sed Diet Supplemented with Sodium Bicronte nd Monensin* X. Z. Li,3, C. G. Yn, R. J. Long 2, G. L. Jin, J. Shine Khuu, B. J. Ji, S. H. Choi, H. G. Lee 4 nd M. K. Song** Deprtment of Animl Science, Chunguk Ntionl University, Cheongju, Chunguk, , Kore ABSTRACT : A metolic study ws conducted with four ruminlly-cnnulted lctting gots (Snen, 29 weeks lcttion, 65± 5 kg) in 4 4 Ltin squre design with 4 dietry tretments. The gots were fed sl mixed diet consisting of 80% concentrte nd 20% chopped rye grss hy (DM sis, CON). The gots were lso fed the CON diet supplemented with soyen oil t 5% level of the concentrte (SO), the SO diet supplemented with 0.5% of sodium icronte (SO-B) or the SO-B diet supplemented with 30 ppm monensin (SO-BM). The gots were housed in individul pen nd the study ws conducted for 8 weeks. An incresed molr proportion of propionte (C 3 ) ws oserved t h (p<0.003) nd 6 h (p<0.029) post-feeding from ll the supplemented diets. Clculted methne emission ws mrkedly decresed prior to morning feeding (p<0.0), nd t h (p<0.05) nd 6 h post-feeding (p<0.05) in gots fed the supplemented diets. All the supplements incresed (p<0.000) cis9, trns-cla content in rumen fluid. Concentrtions of oth cis9, trns-cla (p<0.000) nd trns0, cis2-cla (p<0.026) were lso incresed in the milk ft of lctting gots fed the supplemented diets. The SO-B nd SO-BM diets further incresed CLA content in got milk compred to the SO diet. All supplements incresed unsturted (UFA, p<0.002), monounsturted (MUFA, p<0.002) nd polyunsturted ftty cids (p<0.04) nd reduced SFA to UFA rtio (p<0.023). The concentrtion of MUFA ws even greter (p<0.002) for SO-BM thn for the SO-B diet. In conclusion, feeding soyen oil (5% of concentrte) to lctting gots ws useful wy to improve milk ft nd to improve ftty cid profile in the milk y incresing potentilly helthy ftty cids such s CLA. Supplementtion of sodium icronte or sodium icronte with monensin to the soyen oil-sed diet incresed CLA content further in got milk. Supplementtion of soyen oil my e n effective method to reduce methne emission in lctting gots. (Key Words : Lctting Got, Soyen Oil, Monensin, CLA, Milk, Methne Emission) INTRODUCTION Helth-conscious consumers re demnding milk with higher proportion of helthy ft. An improvement in the nutritionl vlue of got milk is of importnce to humn helth. Dietry mnipultion with lipid could improve got * This work ws supported y the reserch grnt ( ) of the Rurl Development Administrtion. ** Corresponding Author: Mn K. Song. Tel: , E-mil: mksong@cnu.c.kr Deprtment of Animl Science, Ynin University, Ynji, Chin. 2 Interntionl Centre for Tietn Plteu Ecosystem Mngement, Lnzhou University, Chin. 3 College of Grsslnd Sciences, Gnsu Agriculturl University, Lnzhou, Chin. 4 Deprtment of Bio-Resources nd PNU-Specil Animl Biotechnology Center, College of Nturl Resources & Life Science, Pusn Ntionl University, Kyung Nm, , Kore. Received Jnury 28, 2009; Accepted April 0, 2009 milk composition nd my indeed chnge ftty cid composition in milk ft (Chillird, 982), nd thus is one wy to lter the ftty cid profile of milk ft. Since conjugted linoleic cid (CLA) ws identified s n ntimutgenic sustnce (H et l., 987), it hs een shown to e potent nti-crcinogen in severl cell culture nd niml models (Kritchevsky, 2000). Other enefits ttriuted to CLA consumption include effects on ody composition, the immune system, therosclerosis nd one helth (McDonld, 2000). Vrious ttempts to increse CLA content in ruminnt products hve included the ppliction of lipid source. Supplementtion of linoleic cid (C 8:2 ) nd linolenic cid (C 8:3 ) in the form of oil or oil seeds to the diet hs een shown to enhnce the CLA content of rumen fluid (Dhimn et l., 2000; Wng et l., 2003; Choi nd Song, 2005), milk of diry cttle (Dhimn et l., 2000; Loor et l., 2005), nd ft tissues of sheep (Choi et l., 2006) nd eef cttle (Wng et l., 2006). Feeding moderte dose of plnt oil to lctting gots ws

2 522 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): useful wy to increse milk ft nd CLA content in milk (Bouttour et l., 2008; Bernrd et l., 2009). Menwhile, ionophoric ntiiotics such s monensin hve een found to interfere with the io-hydrogention of cis-9, cis-2 C 8:2 with n ccumultion of intermedite products including CLA (Fellner et l., 997). Incresed CLA concentrtion in milk ft of diry cttle (Suer et l., 998) nd eef ft (Wng et l., 2006) were lso reported when the diet ws supplemented with monensin, ut its effect on CLA enrichment in milk ft hs een controversil (Chouinrd et l., 998; Dhimn et l., 999). In ddition, sodium icronte, hving uffering ctivity (Erdmn, 988), my lso influence CLA formtion in the rumen since the io-hydrogention is ffected y ruminl ph (Wng et l., 2003). Most previous experiments with lctting gots hve exmined the CLA in milk ft in response to plnt oil supplementtion of the diet. Therefore, the ojective of the current study ws to exmine the comined effect of soyen oil, sodium icronte nd monensin in the diet on fermenttion chrcteristics in the rumen, nd CLA content in rumen fluid nd milk ft of the lctting got. Methne emission from the rumen ws lso estimted since C 8:2 supplementtion reduces fermenttion rte (Prins et l., 972) nd depresses CH 4 genertion in the rumen (Broudiscou et l., 990). dietry tretments. The gots were fed sl mixed diet consisting of 80% concentrte nd 20% chopped rye grss hy (DM sis, CON). The gots were lso fed the CON diet ut supplemented with soyen oil t 5% level of the concentrte (SO), the SO diet supplemented with 0.5% of sodium icronte (SO-B) or the SO-B diet supplemented with 30 ppm monensin (SO-BM). Experimentl diets were prepred t 5 dy intervls. Cr 2 O 3 s externl mrker ws dosed (0.% of diet, DM sis) to individul gots through the rumen cnnul twice dily during feeding throughout the whole experimentl period for the exmintion of whole trct digestiility. Concentrte constituents nd nutrient composition of the totl diet re shown in Tle. Ftty cid composition of soyen oil nd the sl diet re shown in Tle 2. Feeding mngement The lctting gots were housed in individul pen nd fed.6 kg (DM sis) of the mixed diets twice dily (08:00 nd 8:00) in equl mounts, nd were llowed free ccess to wter nd trce-minerlized slt lock. The feeding level of the sl diet (CON) ws sed on nutrient requirements for lctting gots (AFRC, 993). The study ws conducted for 8 weeks in totl, with 0 dys for diet dpttion nd 4 dys for smpling in ech experimentl period. MATERIALS AND METHODS Animls nd diets The metolic study ws conducted with four ruminlly-cnnulted lctting gots (Snen, 29 weeks lcttion, 65±5 kg) in 4 4 Ltin squre design with 4 Mesurements nd nlysis Feed residues were collected dily t 30 min prior to morning feeding (08:00) to estimte feed intke nd digestiility. Lctting gots were mchine- milked twice dily (08:00 nd 8:00). Milk yield ws recorded dily during smpling dys of ech experimentl period nd Tle. Ingredients of concentrte nd nutrient composition of the totl diet (DM sis) Ingredients of concentrte Tretments Commercil concentrte (%) Soyen oil (SO, %) Sodium icronte (B, %) Monensin (M, ppm) Nutrient composition of totl diet (%) 2 Dry mtter Crude protein Ether extrct Neurl detergent fier Crude sh CON = Commercil concentrte without supplements; SO = Supplemented with soyen oil (5%) to the concentrte; SO-B = Supplemented with soyen oil (5%) nd sodium icronte (0.5%) to the concentrte; SO-BM = Supplemented with soyen oil (5%) nd sodium icronte (0.5%), monensin (30 ppm) to the concentrte. 2 Mixed diet of concentrte nd forge.

3 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): Tle 2. Ftty cid composition of feed nd soyen oil Ftty cids Feeds nd soyen oil (% of totl ftty cid) Concentrte Ryegrss hy Soyen oil Dodecnoic cid (C 2:0 ) Myristic cid (C 4:0 ) Pentdecnoic cid (C 5:0 ) Plmitic cid (C 6:0 ) Plmitolic cid (C 6: ) Mrgric cid (C 7:0 ) Steric cid (C 8:0 ) Oleic cid (C 8: ) Linoleic cid (C 8:2 ) Lenolenic cid (C 8:3 ) Archidonic cid (C 20:0 ) Eicosenoic cid (C 20: ) Eicostrienoic cid (C 20:3 ) Archidonic cid (C 20:4 ) ND Henecosnoic cid (C 2:0 ) Behenic cid (C 22:0 ) Docosenic cid (C 22: ) ND Docosdienoic cid (C 22:2 ) Tricosnoic cid (C 23:0 ) Tetrcosnoic cid (C 24:0 ) Sum of other ftty cids ND = Not detected. 00ml of milk ws smpled t ech milking for 2 consecutive dys throughout the tril. The m nd pm milk smples were then comined for ech got on every smpling dy. The collected milk smples were freeze dried nd then sujected to nlyses of ft, protein nd lctose content nd ftty cid composition of ft. Ruminl contents were collected on 2 consecutive dys in ech period through the rumen fistul prior to morning feeding, nd t, 3 nd 6 h post-feeding, nd were strined through 4 lyers of cheese cloth to collect the rumen fluid t ech smpling time. The ph of rumen fluid ws mesured instntly, nd 5 ml rumen fluid ws collected for mmoni nd voltile ftty cid (VFA) nlysis. All rumen fluid smples collected were kept frozen t -20 C until nlyzed. Approximtely 50 g of fresh feces ws lso collected t 6 h post-feeding fter the collection of ruminl contents for two consecutive dys in ech experimentl period. Proximl nlysis of the diets nd feces, nd of Cr in feces followed the methods of AOAC (995). Neutrl detergent fier (NDF) content ws estimted y the method of Vn Soest et l. (99). Ammoni-N concentrtion ws determined y the method of Fwcett nd Scott (960) using spectrophotometer (DU-650). Rumen fluid (4 ml) ws mixed with ml 25% phosphoric cid nd 0.5 ml pivlic cid solution (% w/v) s n internl stndrd for VFA nlysis. The mixed solution ws centrifuged t 5,000 g for 5 min. nd the superntnt ws used to determine the concentrtion nd composition of VFA using gs chromtogrph (GC, HP5890 seriesii, Hewlett Pckrd Co.) equipped with flme ioniztion detector (FID). Methne production ws estimted from the molr proportion of mjor VFAs y the following eqution of Moss et l. (2000). CH 4 (mmoles/00 mmoles rumen fluid) = 0.45C C C 4 An liquot of got milk ws freeze dried nd contents of ft nd protein were determined y the method of AOAC (995). Dried milk ws deftted using Soxhlet pprtus. Five grms of the deftted milk powder ws dissolved in 00 ml of distilled wter, deproteinized with 0% sulfoslicylic cid (Whiting et l., 97), nd centrifuged (20,000 g, 20 min). The superntnt ws filtered with millipore syringe driven filter unit (Hydrophilic PTEE 0.45 μm) nd then milk lctose content ws mesured y Highperformnce Liquid Chromtogrph (HPLC Acme9000, Yonglin Co., Kore) equipped with n ELS detector. A column (Lun 5μ NH 2 00A, mm) ws used, nd effluent of cetonitrile: wter (80:20) ws chosen s the

4 524 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): moile phse t flow rte of 0.7 ml/min. Ftty cid nlyses For the mesurement of CLA production in rumen fluid, lipids in culture solution were extrcted using Folch s solution (Folch et l., 957), nd methyltion of ftty cid followed the method of Lepge nd Roy (986) prior to injecting into GC (Agilent 6890N) equipped with HP chemisttion softwre for pek integrtion. A 00 m fused silic cpillry column (Supelco SP TM -2560, 0.25 mm i.d. USA) ws used with high purity (99.999%) He s crrier gs t flow rte of 45 ml/min. Injector nd detector tempertures were 240 nd 250 C, respectively. The split rtio to the FID detector ws :00. The oven temperture ws mintined t 40 C for 2 min, incresed to 240 C t rte of 4 C/min, nd mintined t 240 C for 40 min. Lipids in milk powder for ftty cid nlysis were extrcted using Folch s solution. Preprtion of FA methyl esters of milk ft followed the method of ISO 5884 (2002) prior to injecting into GC (Agilent 6890N). Cpillry column, crrier gs nd split rtio to the FID detector were the sme s for lipids in rumen fluid. Injector nd detector tempertures were 270 nd 280 C, respectively. The oven temperture ws multi-step progrmmed s follows: initil oven temperture ws mintined t 40 C for 2 min, incresed to 30 C t rte of 0 C/min. nd held for min, then incresed t rte of 6.5 C/min to 70 C, followed y rte of 2.75 C/min to 25 C nd held there for 2 min, then incresed t 40 C/min to 230 C nd held for 0 min, nd finlly incresed to 240 C nd mintined for 5 min. Cis9,trns-CLA nd trns0,cis2-cla isomers (Sigm, USA) were used to identify nd quntify ech CLA isomer. Other FA stndrds were otined from Supelco Co. (899, USA). Tridecnoic cid (C 3:0 ) ws used s n internl stndrd nd ll CLA isomers nd other FAs in rumen fluid were quntified using FA stndrds. Sttisticl nlysis The results were nlyzed s 4 4 Ltin squre design using the generl liner procedure of SAS (985) with model tht included diet effect (min effect), nd row nd column effects (lredy known source of vrition). Significnces were compred y S-N-K Test (Steel nd Torrie, 980) with the following sttisticl model: y ijk = μ+α i +τ i +β k +ε ijk Where: y ijk : oservtion vlue in row i, column k, tretment j μ : overll men α i : i th row effect τ j : j th tretment effect(min effect) β k : k th column effect ε ijk : rndom error ~ NID(0, σ 2 ) RESULTS Intke nd whole trct digestiility The dily intkes of dry mtter (DM), crude protein, orgnic mtter nd NDF y lctting gots were slightly reduced y feeding the supplemented diets of soyen oil (SO), soyen oil with sodium icronte (SO-B) nd soyen oil with sodium icronte nd monensin (SO- BM) compred to the CON diet, ut whole trct digestiility of these constituents ws not different mong tretments except tht lipid digestiility ws higher Tle 3. Dily intke nd whole trct digestiility of the diets y lctting gots s influenced y soyen oil supplementtion with sodium icronte or with sodium icronte nd monensin Dily intke (kg) Tretments SEM 2 Pr<F 3 Dry mtter Orgnic mtter Crude protein Ether extrct Neutrl detergent fier Whole trct digestiility (%) Dry mtter Orgnic mtter Crude protein Ether extrct Neutrl detergent fier Referred to Tle. Mens in the sme row with different superscripts differ significntly. 2 Stndrd error of the men. 3 Proility levels.

5 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): ph * c c * (p<0.008) for SO, SO-B nd SO-BM diets thn for the CON diet (Tle 3). c c * -0.5 h h 3 h 6 h Smpling time Figure. ph of rumen fluid in lctting gots when fed soyen oil supplemented diet either with sodium icronte or with sodium icronte nd monensin. CON = Commercil concentrte without supplements; SO = Supplemented with soyen oil (5%) to the concentrte; SO-B = Supplemented with soyen oil (5%) nd sodium icronte (0.5%) to the concentrte; SO-BM, supplemented with soyen oil (5%) nd sodium icronte (0.5%), monensin (30 ppm) to the concentrte. Mens t the sme smpling time with different superscripts differ significntly. * p<0.05. NH 3 -N (mg/00 ml) h h 3 h 6 h Smpling time Figure 2. Ammoni-N concentrtion in rumen fluid of lctting gots when fed soyen oil supplemented diet either with sodium icronte or with sodium icronte nd monensin. CON, commercil concentrte without supplements; SO, supplemented with soyen oil (5%) to the concentrte; SO-B, supplemented with soyen oil (5%) nd sodium icronte (0.5%) to the concentrte; SO-BM, supplemented with soyen oil (5%) nd sodium icronte (0.5%), monensin (30 ppm) to the concentrte. Rumen fermenttion, methne estimtion nd CLA production in rumen fluid Supplementtion of sodium icronte (SO-B) or sodium icronte with monensin (SO-BM) to the soyen Tle 4. Totl concentrtion nd proportions of mjor VFA in rumen fluid of lctting gots when fed soyen oil supplemented diet either with sodium icronte or with sodium icronte nd monensin Tretments Time SEM 2 Pr<F 3 30 min prior to feeding Totl VFA (mmole/00 ml) Molr proportion (mmoles/00 mmoles) Acetic cid (C 2 ) Propionic cid (C 3 ) Butyric cid C 2 /C h post feeding Totl VFA (mmole/00 ml) Molr proportion (mmoles/00 mmoles) Acetic cid (C 2 ) Propionic cid (C 3 ) Butyric cid C 2 /C h post feeding Totl VFA (mmole/00 ml) Molr proportion (mmoles/00 mmoles) Acetic cid (C 2 ) Propionic cid (C 3 ) Butyric cid C 2 /C h post feeding Totl VFA (mmole/00 ml) Molr proportion (mmoles/00 mmoles) Acetic cid (C 2 ) Propionic cid (C 3 ) Butyric cid C 2 /C Refer to Tle. 2 Stndrd error of the men. 3 Proility levels.

6 526 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): oil (SO) dded diet incresed (p<0.05) ruminl ph t h-6 h post-feeding compred to CON nd SO diets (Figure ), ut mmoni concentrtion in rumen fluid ws not influenced y the supplements lthough it ws slightly incresed on the SO diet t 3 h nd 6 h post-feeding compred to the other diets (Figure 2). Feeding SO, SO-B nd SO-BM diets slightly incresed totl VFA concentrtion in the rumen fluid of lctting gots for ll smpling times compre to the CON diet (Tle 4). Incresed molr proportion of propionte (C 3 ) ws oserved t h (p<0.003) nd 6 h (p<0.029) post-feeding from the SO, SO-B nd SO- BM diets without difference mong supplemented diets. While molr proportion of cette (C 2 ) ws not influenced y the diets, tht of utyrte (C 4 ) ws lower (p<0.020) for the SO diet t the 6 h smpling time thn for the CON diet. The C 2 /C 3 rtios were lower t h (p<0.003) nd 6 h (p<0.029) post-feeding for ll the supplemented diets thn for the CON diet. Clculted molr proportion of methne sed on mjor VFAs ws mrkedly decresed prior to morning feeding (p<0.0), nd h (p<0.05) nd 6 h postfeeding (p<0.05) for gots fed ll supplemented diets (Figure 3). Feeding the SO, SO-B or SO-BM diet incresed (p<0.000) cis9, trns-cla concentrtion in rumen fluid from h to 6 h post-feeding compred to the CON diet nd incresed trns0, cis2-cla t 3 h post-feeding (Tle 5). Thus, the sum of oth CLA isomers ws gretly incresed (p<0.000-p<0.0006) from h to 6 h post-feeding y feeding the supplemented diets compred to the CON diet. Concentrtions of cis9, trns-cla (p<0.000) nd the sum of oth CLAs (p<0.0006) were even greter in the CH 4 (mmoles/00 mmoles) ** * * -0.5 h h 3 h 6 h Smpling time Figure 3. Estimtion of methne emission (mmoles/00 mmoles VFA) from rumen fluid of lctting gots when fed soyen oil supplemented diet either with sodium icronte or with sodium icronte nd monensin. CON = Commercil concentrte without supplements; SO = Supplemented with soyen oil (5%) to the concentrte; SO-B = Supplemented with soyen oil (5%) nd sodium icronte (0.5%) to the concentrte; SO-BM = Supplemented with soyen oil (5%) nd sodium icronte (0.5%), monensin (30 ppm) to the concentrte. Mens t the sme smpling time with different superscripts differ significntly. * p<0.05; ** p<0.0. rumen fluid of lctting gots fed the SO-B nd SO-BM diets t h post-feeding thn the SO diet. Milk components, C 8 -ftty cid profile nd CLA content in milk ft Milk yield, nd contents of ft nd lctose in got milk were not influenced ut milk ft ws incresed (p<0.035) y feeding of SO, SO-B or SO-BM diets compred to the CON diet (Tle 6). Tle 7 shows C 8 -ftty cid profile in Tle 5. CLA production in rumen fluid of lctting gots when fed soyen oil supplemented diet either with sodium icronte or with sodium icronte nd monensin Tretments (mg/50 ml rumen fluid) SEM 2 Pr<F 3 30 min prior to feeding cis9,trnscla trns0,cis2cla Sum of CLAs h post feeding cis9,trnscla 0.5 c <0.000 trns0,cis2cla Sum of CLAs 0.25 c h post feeding cis9,trnscla 0.37 c <0.000 trns0,cis2cla 0.06 c Sum of CLAs 0.43 c h post feeding cis9,trnscla <0.000 trns0,cis2cla Sum of CLAs Refer to Tle. 2 Stndrd error of the men. 3 Proility levels.

7 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): Tle 6. Yield nd composition of lctting got milk when fed soyen oil supplemented diet either with sodium icronte or with sodium icronte nd monensin Items Tretment SEM 2 Pr<F 3 Milk yield (kg/d) Milk DM (%) Milk protein (%) Milk ft (%) Milk lctose (%) Refer to Tle. 2 Stndrd error of the men. 3 Proility levels. milk ft s influenced y the supplementtion of soyen oil lone (SO) or with sodium icronte (SO-B) or with sodium icronte nd monensin (SO-BM). Concentrtions of steric cid (p<0.00), elidic cid (p<0.020), oleic cid (p<0.046), vccenic cid (t-c 8:, p<0.00) nd C 8:2 (p<0.009) were incresed in the milk ft of gots fed the supplemented diets compred to those fed the CON diet. The highest concentrtion of tc 8: ws otined from the SO-BM diet followed y the SO-B diet. As expected, concentrtions of oth cis9, trns-cla (p<0.000) nd trns0, cis2-cla (p<0.026), nd the sum of oth CLAs (p<0.00) were lso incresed in the milk ft for ll supplemented diets (Tle 7). When compred with the CON diet, ll supplements incresed the concentrtions of sturted ftty cids (SFA, p<0.038), unsturted ftty cids (UFA, p<0.002), monounsturted ftty cids (MUFA, p<0.002) nd polyunsturted ftty cids (p<0.04) ut reduced SFA to UFA rtio (p<0.023, Tle 7). The concentrtion of MUFA ws even greter (p<0.002) for the SO-BM thn the SO-B diet. DISCUSSION The present study ws conducted to exmine CLA production in the rumen nd in milk ft, nd to evlute methne production in the rumen of lctting gots when vrious dietry supplements were pplied. Soyen oil dded to the diet should increse energy density nd hs een useful s source of C 8:2, which is one of the two mjor precursors of CLA. Sodium icronte cted to control ph in rumen fluid (Schmidely et l., 2005), nd monensin modified ruminl fermenttion (Wng et l., 2005) nd ffected, to some extent, CLA production in the rumen (Wng et l., 2006). Supplementtion of high level of ft or oil to the diet generlly reduces intke nd digestiility, depending upon level of ddition. Reduction in DM intke hs een widely Tle 7. C 8 ftty cid profiles nd CLA (mg/g milk powder, DM) concentrtion in milk ft of lctting gots when fed soyen oil supplemented diet either with sodium icronte or with sodium icronte nd monensin Tretments (mg/g milk powder) SEM 2 Pr<F 3 C 8: c9-c 8: t9-c 8: t-c 8: 0.69 c C 8: Sum of CLAs.22 c c9,tcla <0.000 t0,c2cla c C 8: others SFA UFA c MUFA 3.88 c PUFA SFA/UFA Refer to Tle. 2 Stndrd error of the men. 3 Proility levels.

8 528 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): reported fter the inclusion of high levels of oils to ruminnt diets (Sutton et l., 983; Sutter et l., 2000; Jordn et l., 2004). In the present study, however, DM intke nd whole trct digestiility of most mjor dietry components, except for lipid, were not gretly ffected y ddition of soyen oil t 5% level (DM) to the concentrte (Tle 3). This result might e due to the low level of oil ddition. Incresed ruminl ph of lctting gots fed SO-B nd SO-BM diets (Figure ) ws likely due to the ddition of sodium icronte (0.5% of `concentrte) s reported y Hdjipnyiotou (988). Schmidely et l. (2005) lso found tht soyen oil supplementtion with sodium icronte slightly incresed rumen VFA concentrtions nd the molr proportion of cette. In the present study, feeding of ll supplemented diets slightly incresed totl VFA concentrtion nd molr proportion of propionte in the rumen (Tle 4). The incresed propionte proportion ws ssocited with decresed proportions of cette nd utyrte. In the current study, the reduction in CH 4 output (Figure 3) s clculted y molr proportion of mjor VFAs t indicted smpling times of rumen fluid ws more likely to e result of supplementtion of oils with sodium icronte nd monensin, nd shifted molr concentrtion of VFA from cette to propionte (Tle 4). Such theoreticl clcultions hve een confirmed y in vitro study where the end products were esily quntified (Moss et l., 2000). Acette nd utyrte promote methne production while propionte formtion cn e considered s competitive pthwy for hydrogen use in the rumen (Moss et l., 2000; Newold et l., 2005). This result is consistent with the ide tht propionte production nd methne genertion re competing for hydrogen in the rumen. Monensin depressed methne production y mixed rumen microes in vitro (Vn Nevel nd Demeyer, 992). In ddition, reductions in CH 4 emissions in the rumen hve een widely reported when vriety of plnt oils were dded to the diet (Cies lk, 2003; Jordn et l., 2004) nd the level of methne emission in ruminnts is directly proportionl to io-hydrogention of UFA (Plscenci et l., 999). It ws lso found tht the ddition of soyen oil in the diet (6% of DMI) decresed 40% of CH 4 output without decresing the intke (Jordn et l., 2006). Otherwise, Chen nd Wolin (979) reported tht methne depression y oil supplementtion might result from shift in cteril popultion from grm positive to grm negtive orgnisms with concurrent shift in fermenttion from cette to propionte. The incresed content of CLA in rumen fluid of lctting gots fed the supplemented diets (Tle 5) might e siclly due to the soyen oil supplementtion, nd monensin could lso contriute indirectly to CLA production in the rumen. Supplementtion of plnt oil to the diet hs een shown to increse CLA production in rumen fluid (Dhimn et l., 2000; Wng et l., 2003). The monensin effect on CLA production y microes, however, hs een controversil. Monensin incresed the proportion of cis-9,trns-cla in vitro (Fellner et l., 997) nd in vivo (Suer et l., 998; Wng et l., 2006) y interfering with the io-hydrogention of cis-9, cis-2 C 8:2, with n ccumultion of intermedite products, including CLA (Fellner et l., 997). In contrst, Wng et l. (2005) did not find ny effect of monensin (0 ppm) on CLA production when incuted with sfflower oil in vitro. Jin et l. (2008) lso found smll effect of monensin on CLA production in the rumen of Holstein cows when fed diet supplemented with C 8:2 -rich soyen oil nd sodium icronte. In the present study, content of milk ft ws mrkedly incresed nd content of milk protein ws slightly incresed y supplementtion of soyen oil t 5% level of concentrte (Tle 6). Incresed milk ft content of lctting gots s influenced y plnt oil supplementtion ws similr to the results reported y Dccord (987). However, Chillird et l. (2006) reported tht the ddition of poly-unsturted ftty cid rich-plnt oil to highconcentrte diets did not increse milk ft of lctting gots. Bumn nd Griinri (2003) lso reported tht got milk ft content ws not decresed when vegetle oils were dded to low-forge diet. Chillird nd Bocquier (993) found tht, lthough ft supplementtion to the diets of lctting cows nd ewes often decresed milk protein content nd ssocited cogultion properties, these negtive effects were not oserved in gots. Such differences in milk ft etween species (lctting got vs. diry cow) could e relted to differences in the metolism of ftty cids in the rumen or in the mmmry glnd (Schmidely nd Suvnt, 200). High levels of C 8:2 or C 8:3 in the form of oil seeds or oils re known to enhnce the CLA content in milk ft of diry cows (Loor et l., 2005; Shingfield et l., 2006; Bu et l., 2007; Chntprsrn nd Wnpt, 2008) nd in met (Choi et l., 2006; Wng et l., 2006). Bouttour et l. (2008) suggested tht feeding moderte dose of soyen oil to lctting gots would e useful wy to increse CLA content in milk, nd to reduce the therogenicity index without negtive effects on intke, milk yield, nd protein content. Gómez-Cortés et l. (2008) found tht CLA content in milk of lctting sheep cn e sustntilly incresed (more thn 3-fold) y dding high levels of soyen oil in the diet without ny negtive effects on niml performnce. In the present study, the significnt increse in concentrtion of cis9, trns-cla ws certinly due to the supplemented soyen oil. An increse in ruminl ph y

9 Li et l. (2009) Asin-Aust. J. Anim. Sci. 22(): ddition of sodium icronte might lso stimulte the rte of lipolysis nd CLA content in milk (Vn Nevel nd Demeyer, 996; Kennelly et l., 999; Khorsni nd Kennelly, 200) s ruminl ph modifies the extent of iohydrogention of dietry polyunsturted ftty cids in the rumen (Klscheur et l., 997). In ddition, Alzhl et l. (2008) found monensin intercted with PUFA rich-soyen oil, nd thus linerly incresed cis9, trns-cla concentrtion in milk ft of lctting gots. In contrst, Dhimn et l. (996) nd Chouinrd et l. (998) oserved no effect of monesin on CLA content in milk ft. In the current study, monensin supplemented with soyen oil nd sodium icronte slightly incresed cis9, trns-cla content in milk ft compred to other oil tretments. In conclusion, feeding moderte dose of soyen oil (5% of concentrte) to lctting gots ws useful wy to improve oth milk ft nd ftty cid profile in the milk y incresing potentilly helthy ftty cids such s CLA without ny detrimentl effects on milk production. Supplementtion of sodium icronte or sodium icronte with monensin to the soyen oil sed diet incresed CLA content. Supplementtion of soyen oil my e n effective mens to reduce methne emission in the lctting got. REFERENCES AFRC Energy nd protein requirements of lctting gots. Advisory mnul prepred y the AFRC technicl committee on responses to nutrients. pp CAB Interntionl, Wllingford, UK. Alzhl, O., N. E. Odongo, T. Mutsvngw, M. M. Or-Rshid, T. F. Duffield, R. Bgg, P. Dick, G. Vessie nd B. W. McBride Effects of monensin nd dietry soyen oil on milk t percentge nd milk ftty cid profile in lctting diry cows. J. Diry Sci. 9: AOAC Officil methods of nlysis, 5th ed. ssocition of officil nlyticl chemists, Wshington, DC. Bumn, D. E. nd J. M. 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