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1 Met Science 84 (2010) Contents lists vilble t ScienceDirect Met Science journl homepge: Feeding co-extruded flxseed to pigs: Effects of durtion nd feeding level on growth performnce nd bckft ftty cid composition of grower finisher pigs M. Juárez, M.E.R. Dugn, *, N. Aldi, J.L. Alhus, J.F. Ptience b, R.T. Zijlstr c, A.D. Beulieu b Agriculture nd Agri-Food Cnd, Lcombe Reserch Centre, 6000 C & E Tril, Lcombe, Albert, Cnd T4L 1W1 b Pririe Swine Centre, Inc., Ssktoon, SK, Cnd S7H 5N9 c University of Albert, Edmonton, AB, Cnd T6G 2P5 rticle info bstrct Article history: Received 16 June 2009 Received in revised form 2 October 2009 Accepted 13 October 2009 Keywords: Omeg-3 Flx Regression Linseed Pork To exmine the effect of co-extrusion on subsequent n-3 ftty cids in pig tissues, 8 pigs (brrows nd gilts) were ssigned to either control tretment or one of nine tretments rrnged in 3 3 fctoril design with 3 levels of co-extruded flxseed (5%, 10% nd 15%) nd 3 durtions of feeding (4, 8 nd 12 weeks). Feed conversion improved slightly (P = 0.01) with incresing dietry flxseed but feeding flx for more thn 8 weeks reduced verge dily gin (P = 0.02). In generl, the durtion nd level of coextruded flxseed feeding ffected (P < 0.05) most ftty cids except for 22:6n-3 (P > 0.05). Incresing the durtion of flx feeding led to significnt qudrtic effects in bckft 18:3n-3 (P < 0.001) nd totl n-3 ftty cids (P = 0.002) when feeding 5% co-extruded flxseed. Those increses were liner (P < 0.001) when feeding 10% nd 15% co-extruded flxseed. Consequently feeding higher levels of flx for shorter periods vs. lower levels for longer periods ppers to be more efficient t incresing n-3 ftty cids in pig bckft, but increses ppered to be less consistent. Moreover the ddition of 50:50 mix of extruded flx/pes to pig diets provided highly vilble source of 18:3n-3 yielding n-3 ftty cid enrichments in bckft comprble to studies where extrcted flxseed oil ws fed. Feeding flx coextruded with field pes cn be used to optimize consistent enrichments of n-3 ftty cids in bck ft nd reltively smll mounts of this ft could be used to mnufcture pork products to meet Cndin stndrds for n-3 ftty cid enrichment. Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. 1. Introduction Historiclly humns consumed diets with n n-6 to n-3 ftty cid rtio of 1:1. In Western diets, this rtio hs incresed over the lst 100 yers to n verge of 15:1 (Simopoulos, 2008). Consuming n-3 ftty cids my provide helth benefits by reducing the risks for severl diseses including hert disese (Ruxton, Reed, Simpson, & Millington, 2004), cncer (Lrsson, Kumlin, Ingelmn- Sundberg, & Wolk, 2004) nd inflmmtory diseses (Clder & Grimble, 2002). Thus the potentil use of livestock products s vehicles to deliver n-3 ftty cids hs been the subject of intensive reserch (Moghdsin, 2008). In this context, dietry strtegies used to customize ftty cid composition of pig ft hve been proven to be very effective becuse dietry ftty cids cn be incorported into pig ft with little modifiction (Bee, Jcot, Guex, & Biolley, 2008; D Arrigo et l., 2002; Wood et l., 2008). However, differences in the reltionships between intke nd deposition exist, nd these relte to whether the specific ftty cid cn be synthesized in vivo. A strong reltionship is seen for essentil ftty * Corresponding uthor. E-mil ddress: Mike.Dugn@AGR.GC.CA (M.E.R. Dugn). cids [linoleic (18:2n-6) nd -linolenic (18:3n-3) cids] nd their n-3 nd n-6 elongtion nd desturtion products. On the other hnd, sturted nd monounsturted ftty cids re synthesised in vivo nd their deposition is less influenced by diet (Enser, Richrdson, Wood, Gill, & Sherd, 2000). Flx is the richest oilseed source of 18:3n-3 nd feeding flx to pigs hs been used to increse levels of n-3 ftty cids in pork, s reviewed by Nguyen, Nuijens, Everts, Slden, nd Beynen (2003). Recently Thcker, Rcz, nd Soit (2004) reported feeding flx coextruded with field pe could void problems with grinding nd storge nd Htoo, Meng, Ptience, Dugn, nd Zijlstr (2008) investigted extrusion techniques for flx/pe mixture to optimize 18:3n-3 vilbility. Htoo et l. (2008) fed pigs 50:50 mixture of flx nd pes tht ws either ground through knife mill with 2 mm sieve or co-extruded using single or double screw techniques. Single screw extrusion with miniml wter input incresed 18:3n-3 vilbility in the flx/pe mix by 16% reltive to ground flx/pes nd by 10% reltive to other extrusion techniques. In contrst, Thcker et l. (2004) found feeding 12% flx s 50:50 mix of flx/pes reduced rtes of body weight gin in finisher pigs wheres most other studies hve found pigs cn be fed up to 15% flx without ffecting performnce (e.g. Romns, Johnson, Wulf, /$ - see front mtter Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. doi: /j.metsci

2 M. Juárez et l. / Met Science 84 (2010) Libl, & Costello, 1995; Romns, Wulf, Johnson, Libl, & Costello, 1995b). However, regionl vritions in oil content nd ftty cid distribution in flxseed (Hll Iii, Tulbek, & Xu, 2006) mkes comprison of results from different loctions difficult. Moreover incorportion rtes of 18:3n-3 when feeding flx hve been quite vrible nd this cn prtly be ttributed to processing chllenges due to its high oil nd 18:3n-3 content, but little ttention hs been pid to optimizing 18:3n-3 vilbility. The objectives of the present reserch were, therefore, to feed single screw extruded flx/pes (50:50) to grow/finish pigs for different durtions nd levels nd exmine the effects on niml performnce nd n-3 ftty cid incorportion into bckft. The dietry inclusion nd the durtion of flx feeding were similr to those fed by Thcker et l. (2004) to determine if nd when single screw extruded flx would negtively influence niml performnce. In ddition, 3 3 fctoril design ws employed to determine if 18:3n-3 nd n-3 ftty cids levels in bckft would plteu (Fontnills, Brroet, Bucells, & Gurdiol, 1998; Mtthews, Homer, Thies, & Clder, 2000) or remin liner (Cherin & Sim, 1995; Riley, Enser, Nute, & Wood, 2000; Romns et l., 1995, 1995b) when feeding to slughter end point typicl for Cnd (i.e. 115 kg). 2. Mterils nd methods 2.1. Animl mngement Animls involved in this study were cred for ccording to the guidelines set out by the Cndin Council of Animl Cre (CCAC, 1993) under protocol pproved by the University of Ssktchewn Committee on Animl Cre nd Supply. The study included 80 pigs from the Pririe Swine Centre (Ssktoon, SK, Cnd) with n initil body weight of 31 ± 3 kg (men ± SD). All the nimls were produced on-site nd fed the sme bckground diet prior to the experiment. Animls were strtified by weight, prentge Tble 1 Ingredient composition nd nutrient contents of experimentl diets; weeks 1 4. Flx (%) Ingredients (% s fed) Whet Brley Soyben mel Field pe Co-extruded flxseed nd field pe Tllow Di-clcium phosphte Limestone Vitmin premix b Minerl premix c Slt l-lysine-hcl l-threonine DL-methionine Clculted nutrient content (s fed) DE d (Mcl kg 1 ) Digestible lysine: DE (g Mcl DE 1 ) e Crude protein (%) Clcium (%) Phosphorus, totl (%) Co-extruded 50% flxseed nd 50% field pe (Linpro; O&T Frms, Regin, Ssktchewn, Cnd). b Provided per kilogrm of diet: vitmin A, 8250 IU; vitmin D 3, 825 IU; vitmin E, 40 IU; nicin, 35 mg; d-pntothenic cid, 15 mg; riboflvin, 5 mg; mendione, 4 mg; folic cid, 2 mg; thimine, 1 mg; d-biotin, 0.2 mg; nd vitmin B 12,25lg. c Provided per kilogrm of diet: Zn, 100 mg s zinc sulfte; Fe, 80 mg s ferrous sulfte; Cu, 50 mg s copper sulfte; Mn, 25 mg s mngnous sulfte; I, 0.50 mg s clcium iodte; nd Se, 0.10 mg s sodium selenite. d Digestible energy. e Other mino cids were formulted s rtio to lysine (set t 100%): threonine, 62; methionine, 30; nd tryptophn, 20 (NRC, 1998). nd gender nd included 4 gilts nd 4 brrows per tretment. Pigs were housed individully in m (1.67 m 2 ) pens with fully sltted floors nd ech pen ws equipped with single spce feeder nd nipple drinker. Tble 2 Ingredient composition nd nutrient contents of experimentl diets; weeks 5 8. Flx (%) Ingredients (% s fed) Whet Brley Soyben mel Field pe Co-extruded flxseed nd field pe Tllow Di-clcium phosphte Limestone Vitmin premix b Minerl premix c Slt l-lysine-hcl l-threonine DL-methionine Clculted nutrient content (s fed) DE d (Mcl kg 1 ) Digestible lysine: DE (g Mcl DE 1 ) e Crude protein (%) Clcium (%) Phosphorus, totl (%) Co-extruded 50% flxseed nd 50% field pe (Linpro; O&T Frms, Regin, Ssktchewn, Cnd). b Provided per kilogrm of diet: vitmin A, 8250 IU; vitmin D 3, 825 IU; vitmin E, 40 IU; nicin, 35 mg; d-pntothenic cid, 15 mg; riboflvin, 5 mg; mendione, 4 mg; folic cid, 2 mg; thimine, 1 mg; d-biotin, 0.2 mg; nd vitmin B 12,25lg. c Provided per kilogrm of diet: Zn, 100 mg s zinc sulfte; Fe, 80 mg s ferrous sulfte; Cu, 50 mg s copper sulfte; Mn, 25 mg s mngnous sulfte; I, 0.50 mg s clcium iodte; nd Se, 0.10 mg s sodium selenite. d Digestible energy. e Other mino cids were formulted s rtio to lysine (set t 100%): threonine, 62; methionine, 30; nd tryptophn, 20 (NRC, 1998). Tble 3 Ingredient composition nd nutrient contents of experimentl diets; weeks Flx (%) Ingredients (% s fed) Whet Brley Soyben mel Field pe Co-extruded flxseed nd field pe Tllow Di-clcium phosphte Limestone Vitmin premix b Minerl premix c Slt l-lysine-hcl l-threonine DL-methionine Clculted nutrient content (s fed) DE d (Mcl kg 1 ) Digestible lysine: DE (g Mcl DE 1 ) e Crude protein (%) Clcium (%) Phosphorus, totl (%) Co-extruded 50% flxseed nd 50% field pe (Linpro; O&T Frms, Regin, Ssktchewn, Cnd). b Provided per kilogrm of diet: vitmin A, 8250 IU; vitmin D 3, 825 IU; vitmin E, 40 IU; nicin, 35 mg; d-pntothenic cid, 15 mg; riboflvin, 5 mg; mendione, 4 mg; folic cid, 2 mg; thimine, 1 mg; d-biotin, 0.2 mg; nd vitmin B 12,25lg. c Provided per kilogrm of diet: Zn, 100 mg s zinc sulfte; Fe, 80 mg s ferrous sulfte; Cu, 50 mg s copper sulfte; Mn, 25 mg s mngnous sulfte; I, 0.50 mg s clcium iodte; nd Se, 0.10 mg s sodium selenite. d Digestible energy. e Other mino cids were formulted s rtio to lysine (set t 100%): threonine, 62; methionine, 30; nd tryptophn, 20 (NRC, 1998).

3 580 M. Juárez et l. / Met Science 84 (2010) Tble 4 Crude ft nd ftty cid composition of diets. Weeks 1 4; flx (%) Weeks 5 8; flx (%) Weeks 9 12; flx (%) Item Crude ft (g kg 1 ) Ftty cid (%) 16: c-16: : c-18: :2n :3n c-20: Mesured. The study included control tretment (fed for 12 weeks) nd nine tretments rrnged in 3 3 fctoril design with 3 levels of extruded flxseed (5%, 10% nd 15%) nd 3 durtions of feeding (4, 8 nd 12 weeks). Pigs on the 4 nd 8 week tretments received control diets for 8 or 4 weeks, respectively prior to receiving their tretment diets. Pigs hd d libitum ccess to feed nd wter. Pig weights nd feed consumption were mesured every two weeks nd used to clculte verge dily gin (ADG), verge dily feed intke (ADFI) nd feed conversion. Diets were formulted nd djusted every 4 weeks (0 4, 4 8 nd 8 12 weeks; Tbles 1 3) to meet the nutrient requirement of the pigs over the experiment (NRC, 1998). Diets were bsed on whet, brley nd soyben mel. Field pes were dded to diets t constnt level within ech feeding period tking into considertion the field pe included in co-extruded product, nd tllow ws used to blnce energy levels mong diets within phse. Diets within ech feeding period hd equl pprent ilel digestible lysine per Mcl of digestible energy (DE). Experimentl diets included LinPro Ò, commercil product (O&T Frms, Regin, Ssktchewn, Cnd) contining 50:50 mixture of co-extruded flxseed nd field pes using single screw extrusion t 400 psi without wter nd brrel temperture of 135 C (Htoo et l., 2008). Tble 4 shows the crude ft content nd ftty cid composition of the different diets Adipose tissue collection One dy prior to slughter in commercil bttoir, subcutneous ft from ech pig ws collected using n 8 mm biopsy punch (Acuderm Inc., USA) t the 10th rib, pproximtely 5 cm from the bckbone. The biopsy site ws scrubbed nd clened with isopropyl lcohol nd iodine solution before injecting locl nesthesi [2 cc of 2% Lidocine, (Gtlin, See, Hnsen, Sutton, & Odle, 2002)]. An incision (3 4 cm) ws mde t the biopsy site before pplying the biopsy punch in order to minimize the quntity of intct skin with the ft smples. The subcutneous ft smples were stored in freezer t 80 C until nlyzed Chemicl nlyses Feed ftty cid methyl esters (FAME) were prepred ccording to Sukhij nd Plmquist (1988) nd bckft (inner lyer) FAME were prepred using the procedure described by Dugn et l. (2007). Feed nd bckft FAME were nlyzed ccording to Dugn et l. (2007) Sttisticl nlysis The dt were nlyzed using the MIXED procedure within SAS (SAS, 2001). Individul pigs were the experimentl unit. The sttisticl design used in the present experiment ws n ugmented fctoril [i.e. 3 levels of flxseed 3 durtions of flxseed feeding 2 genders nd single control group (i.e. 4 gilts nd 4 brrows) fed the control diet for 12 weeks]. The sttisticl model included flxseed level, length of feeding, gender nd the interctions. Initil sttisticl nlysis exmined the min effects of flxseed inclusion, length of feeding nd the interctions. As such min effects could not be computed when the control ws included in the model, therefore, initilly control dt were not used nd the model included gender, diet, weeks of feeding nd ll their interctions. To further explore the effects of feeding flx t different levels for different durtions on bckft ftty cid composition, liner nd qudrtic contrsts were conducted nd this included dt from control nimls. 3. Results nd discussion 3.1. Growth performnce There were no two or three-wy interctions for ADG, ADFI or feed conversion (P > 0.05). As expected, brrows hd higher ADG (7.8%), ADFI (14.3%) nd lower feed conversion (7.9%) thn gilts (P < 0.01; Tble 5). With incresing dietry flxseed, ADFI decresed from 2.62 to 2.45 kg/d (P=0.01, Tble 5) but ADG ws unffected (P = 0.40) nd thus feed conversion improved slightly (from 0.38 to 0.39; P = 0.01). The lck of, or slight positive effects of dding flx to the diets on niml performnce is in greement with the mjority of studies (Corino, Musell, & Mourot, 2008; Fontnills et l., 1998; Koub, Enser, Whittington, Nute, & Wood, 2003; Mtthews et l., 2000; Riley et l., 2000; Romns et l., 1995, 1995b; Wisemn, Redshw, Jgger, Nute, & Wood, 2000). This is in contrst with Thcker et l. (2004) who found tht pigs could tolerte up to 15% dietry flx in the grower period but 12% flx in the finishing diet reduced ADG. In the present experiment, incresing levels of co-extruded flxseed, tended to reduce ADFI (P = 0.06; Tble 5), but did not ffect ADG. Prolonged feeding of co-extruded flxseed, independent of its level of dietry inclusion, reduced ADG (P = 0.01). This observtion together with the results of Thcker et l. (2004) would then suggest tht long-term feeding of co-extruded flxseed my mrginlly reduce ADG, but short-term feeding does not, even t high inclusion levels Bckft ftty cid composition Diet by gender, feeding durtion (weeks) by gender or diet by feeding durtion by gender interctions were not found for bckft ftty cid composition (P > 0.05). Gender influenced bckft ftty cid composition with gilts hving less (P = 0.04) sturted ftty cids (SFA) nd more (P = 0.03) n-6 ftty cids (Tble 6). Similr results were reported by Nuernberg et l. (2005) nd likely relte to

4 M. Juárez et l. / Met Science 84 (2010) Tble 5 Performnce of grower finisher pigs fed different levels of extruded flxseed for different durtions. Vrible Control Diet (% flx) Weeks Gender SEM c P vlue Gilt Brrow Diet Weeks Gender Initil weight (kg) Finl weight (kg) b < ADG (kg d 1 ) b < ADFI (kg d 1 ) b 2.47 b < Feed efficiency b 0.39 b < No two or three-wy interctions were observed (P > 0.05). b Mens in rows with different letters re significntly different (P < 0.05). c Stndrd error of the men. Tble 6 Gender effects on the percent ftty cid composition of bckft. Ftty cid (%) Gender SEM P vlue Gilt Brrow 18:2n :3n :2n :3n :4n :5n :5n :6n n n n-6/n SFA MUFA PUFA SFA: sturted ftty cids; MUFA: monounsturted ftty cids; PUFA: polyunsturted ftty cids. Stndrd error of the men. brrows being ftter with lrger dipocytes. This would result in greter neutrl lipid to phospholipid rtio in brrow bckft with neutrl lipids being reltively rich in SFA nd phospholipids reltively rich in n-6 ftty cids (Riley et l., 2000). All differences between genders were, however, less thn 1% of totl ftty cids nd would be of limited prcticl significnce. Significnt min effects (P < 0.05) for diet (% flx) nd feeding durtion (week) were found, in ddition to diet by week interctions for most individul ftty cids except for 22:6n-3 (P > 0.05; Tble 7). Severl uthors hve reported lck of effect of flx diets on tissue levels of 22:6n-3 (Ahn, Lutz, & Sim, 1996; Cherin & Sim, 1995; Fontnills et l., 1998; Hk, De Smet, Fremut, Vn Wlleghem, & Res, 2008; Res, De Smet, & Demeyer, 2004; Riley et l., 2000), nd only few studies hve reported incresed levels of 22:6n-3 fter feeding reltively low level (2 2.5%) of dietry flx (Corino et l., 2008; Enser et l., 2000). Long chin ftty cid metbolism is controlled by complex enzymtic system, consisting of desturses nd elongses (Res et l., 2004). These enzymes ct both on the n-6 nd n-3 ftty cids but hve preference for the n-3 (Brenner, 1989). The lck of effect on 22:6n-3 ftty cid my be explined by competition for D6 desturse ctivity between 18:3n-3 nd the precursor for 22:6n-3 (i.e. 24:5n-3), when the dietry concentrtion of 18:3n-3 is high (Cmeron et l., 2000). Diet, feeding durtion nd diet by feeding durtion effects (P < 0.05) were found for totl polyunsturted ftty cids (PUFA), monounsturted ftty cids (MUFA), SFA, n-3 nd n-6 ftty cids nd the n-6/n-3 rtio (Tble 7). In generl, feeding flx contining diets for incresing durtions prior to slughter led to liner (P < 0.05) increses in 18:2n-6, 20:3n-3, 20:5n-3, 22:5n-3, totl PUFA nd n-6 ftty cids nd reductions in 20:4n-6 nd totl MUFA (Tble 8). The liner increse (P < 0.001) for 20:2n-6 nd the liner decrese (P < 0.001) in SFA were only observed when 10% nd 15% flx ws included in the diet. The n-6/n-3 rtio decresed qudrticlly (P < 0.001), while the qudrtic reltionship for totl n-3 content ws stronger when feeding 5% (P = 0.002) thn when feeding 10% (P = 0.192) or 15% (P = 0.041) co-extruded flxseed contining diets. The qudrtic reltionship for n-3 ftty cids when feeding 5% flx in the diets ws lso observed for 18:3n-3 (P < 0.001), while increses in other 18:3n-3 elongtion nd desturtion products (20:3n-3, 20:5n-3 nd 22:5n-3) were found to be liner. Tble 7 Diet, feeding durtion nd diet by feeding durtion effects on percentges of ftty cids in bckft. Flx (%) Control SEM h P vlue Week Diet Weeks Diet week 18:2n e 10.9 de 10.6 e 10.1 e 11.9 cd 13.2 b 11.7 cd 12.8 bc <0.01 < :3n f 4.95 e 5.87 e 5.52 e 9.78 c b 8.37 d b <0.01 < :2n cd 0.50 bcd 0.49 cd 0.46 d 0.54 b 0.54 b 0.51 bcd 0.51 bc < :3n f 0.80 e 1.00 d 0.76 e 1.40 c 1.80 b 1.00 d 1.70 b <0.01 <0.01 < :4n b 0.18 b 0.14 d 0.18 bc 0.15 cd 0.12 d d 0.09 e 0.01 <0.01 <0.01 < :5n e 0.08 d 0.10 cd 0.07 de 0.12 c 0.19 b 0.09 d 0.18 b <0.01 <0.01 < :5n g 0.27 ef 0.29 de 0.22 fg 0.34 cd 0.42 b 0.23 fg 0.36 bc 0.41 b 0.01 <0.01 < :6n n f 6.18 e 7.30 e 6.63 e c b 9.79 d b <0.01 < n e 11.5 de 11.3 e 10.7 e 12.6 cd 13.9 b 12.4 cd 13.4 bc <0.01 < n-6/n b 1.55 c 1.64 c 1.07 e 0.88 f 1.29 d 0.84 f 0.68 g <0.01 <0.01 <0.01 SFA b 36.8 b 34.9 b 34.3 b 31.6 cd 29.2 e 31.8 cd 29.2 de 26.9 e 0.48 <0.01 <0.01 <0.01 MUFA b 44.8 cd 45.8 bc 47.6 b 43.4 d 40.3 e 45.2 cd 40.5 e 36.3 f 0.67 <0.01 < PUFA e 17.8 d 18.7 d 17.5 d 24.4 c 29.8 b 22.3 c 29.6 b <0.01 <0.01 <0.01 SFA: sturted ftty cids; MUFA: monounsturted ftty cids; PUFA: polyunsturted ftty cids. g Mens in rows with different letters re significntly different (P < 0.05). h Stndrd error of the men.

5 582 M. Juárez et l. / Met Science 84 (2010) Tble 8 Liner nd qudrtic contrsts for ftty cids in bckft for length of feeding 5%, 10% or 15% flx to grower finisher pigs prior to slughter (0, 4, 8 nd 12 weeks). P vlue Flx (%) Contrst L Q L Q L Q 18:2n < < :3n-3 <0.001 <0.001 < < :2n < < :3n-3 < < < :4n-6 < < < :5n-3 < < < :5n-3 < < < :6n n-3 < < < n < < n-6/n-3 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 SFA < < MUFA < < < PUFA < < < SFA: sturted ftty cids; MUFA: monounsturted ftty cids; PUFA: polyunsturted ftty cids. Contrst: L = liner nd or Q = qudrtic reltionship (P < 0.05). The effect of feeding flxseed on tissue deposition of n-3 ftty cids in pigs hs been found to be quite vrible (Nguyen et l., 2003). Feeding extrcted flxseed oil likely provides the most digestible form of 18:3n-3, but would be reltively expensive for inclusion in swine diets. D Arrigo et l. (2002) fed 3% flxseed oil (equivlent to 7.5% flxseed contining 40% oil) to gilts for 8 weeks from 48 to 100 kg nd found 9.29% n-3 ftty cids in bckft ftty cids. Results from the present experiment indicte co-extruded flx/pe mixture hd comprbly high n-3 ftty cid vilbility yielding 6.2% nd 11.7% (verge 8.9%) n-3 ftty cids when feeding 5% nd 10% flxseed for 8 weeks. Fontnills, Brroet, Bucells, nd Codony (1997) fed 4% flxseed oil, equivlent to 10% flxseed to brrows for 12 weeks nd found 13.5% n-3 ftty cids in bckft nd present results were eqully s impressive yielding 15.8% n-3 ftty cids in bckft when feeding 10% flx for 12 weeks. Present findings of 9.79%, 16.1% nd 21.6% n-3 ftty cids in bckft when feeding 15% co-extruded flxseed for 4, 8 nd 12 weeks, respectively pper higher thn those reported by severl uthors. Romns et l. (1995b) found 6.92% n-3 ftty cids in inner bckft when feeding 15% flx to pigs for 4 weeks, while Thcker et l. (2004) found 13.5% n-3 ftty cids in bckft when feeding 15% flx for close to 14 weeks nd Specht-Overholt et l. (1997) found 12% n-3 ftty cids in bckft when feeding 15% flx to finisher pigs for 7 weeks. Finlly, Hung, Zhn, Luo, Liu, nd Peng (2008) found 9.72% n-3 ftty cids in bckft ftty cids when feeding 10% flx to pigs for close to 13 weeks. Hence co-extruding flx with pes cn, therefore, be used to optimize n-3 ftty cid vilbility from flx nd optimiztion of flxseed processing will no doubt hve n importnt influence on the profitbility nd vibility of producing n-3 enhnced pork. In Cnd, 300 mg n-3 ftty cids per serving (100 g) is required for n enrichment clim (CFIA & Helth-Cnd, 2009). Thus, when co-extruded flx/pe mixture ws used s source of dietry 18:3n-3: 3.5 g of bckft from pigs fed 10% or 15% flx for 8 or 4 weeks, respectively, 2.5 g of bckft from pigs fed 10% or 15% flx for 12 or 8 weeks, respectively, or 2.0 g of bckft from pigs fed 15% flx for 12 weeks would chieve the n-3 ftty cid levels required for n enrichment clim (ssuming 85% ft in bckft). Additionlly, besides the potentil mnufcturing of pork products enriched in n-3 ftty cids using bckft, commercil len met from pigs fed flx co-extruded with field pes could likely chieve the required n-3 levels by including the mount of ft (subcutneous, intermusculr nd intrmusculr) usully present in retil cuts. Adding flx to pig diets, does not however only ffect bckft levels of n-3 ftty cids. Although there ws decrese in the reltive content of 18:2n-6 in dietry ft when flx ws dded to the diet, the incresed level of ft in flx contining diets ctully led to incresed bsolute mounts (mg/g) of 18:2n-6 in the diet s the level of flx incresed. Consequently this led to liner increses in bckft 18:2n-6 nd totl n-6 ftty cids when flx contining diets were fed for incresing durtions. A liner increse in 20:2n-6 ws, however, only found when the 10% nd 15% flx diets were fed for incresing durtions, nd bckft levels of 20:4n-6 were linerly reduced when flx contining diets were fed for incresing durtions (Tble 8). The decrese in 20:4n-6 levels my be due to the competition between 18:2n-6 nd 18:3n-3 for desturtion nd elongtion to form 20:4n-6 nd 20:5n-3 (Cherin & Sim, 1995). The decrese in 20:4n-6 levels might be considered s beneficil, since incresing concentrtions of this ftty cid in membrne phospholipids result in n overproduction of eicosnoids nd induce pltelet ggregtion (Kristensen, Schmidt, & Dyerberg, 1989), which my contribute to hrdening of the rteries nd other chronic conditions (Simopoulos, 2002). The overll chnges in bckft levels of n-3 nd n-6 when feeding the co-extruded flxseed contining diets for incresing durtions prior to slughter were well reflected by significnt liner (P < 0.001) increses in totl PUFA. In generl, increses in PUFA, however, ment either concomitnt reductions in SFA nd or MUFA. Remrkbly, the level of SFA only showed liner decline (P < 0.001) when feeding the 10% nd 15% co-extruded flx diets for incresing durtions. On the other hnd, increses in PUFA when feeding flx contining diets for incresing durtion were inversely mirrored by liner reductions in MUFA (P < 0.001), probbly due to inhibition of D9 desturse ctivity s the level of n-3 ftty cids incresed in the diet (Wters, Kelly, O Boyle, Moloney & Kenny, 2009) n-3 Ftty cid enrichment prdox Understnding the evolution of n-3 ftty cid enrichment in bckft is n importnt concept when trying to ttin certin level of enrichment for prticulr weight of pig. When following the enrichment of n-3 ftty cids in bckft over time in pigs fed flx from 26 to 95 kg, Fontnills et l. (1998) found rpid enrichment leding to plteu fter bout 4 weeks nd similr observtions were noted by D Arrigo et l. (2002). Bsed on these dt, the ssumption might be mde tht to enrich n-3 ftty cids in mrket weight pigs, feeding pigs during the lst 4 weeks of the finishing period would be enough to rech the mximum level of enrichment. The rte of enrichment nd durtion until plteu re however influenced by the level of flx supplementtion nd the strting weight of the pigs. The rte of ft deposition is higher in hevier pigs, nd hevier pigs lso hve more body ft to dilute n-3 ftty cids originting from dietry flx. On the other hnd, feeding higher levels of flx my provide 18:3n-3 in excess of its metbolism/ctbolism processes, resulting in higher rtes of n-3 ftty cid deposition. Thus, in the present study, when feeding 5% flx co-extruded with field pes plteu in totl n-3 ftty cids ws observed for periods longer thn 8 weeks, with no significnt increse when the feeding durtion ws incresed from 8 to 12 weeks (Tble 7; Fig. 1). However, when feeding 10% nd 15% flx the level of n-3 ftty cids did not plteu nd continued to increse (P < 0.01) between 8 nd 12 weeks. In ddition, the qudrtic component (Tble 8) ws stronger for the lowest level thn for the higher levels of flx ddition, which hd cler liner reltionships, indicting lower dilution effect with incresing dietry flx. Similr results hve been reported by Hung et l. (2008) when feeding 10% flxseed for different periods prior to slughter. n-3 Ftty cid levels cn, therefore, be rpidly enriched in young

6 M. Juárez et l. / Met Science 84 (2010) % n-3 ftty cids Weeks to slughter Totl n-3: Σ(18:3n-3; 20:3n-3; 20:5n-3; 22:5n-3; 22:6n-3) 12 Dietry flx 15 % 10 % 5 % ods ppers to be more efficient t incresing n-3 ftty cids in pig bckft but more consistent enrichments were pprent when feeding lower levels of flxseed for longer durtions. Reching desired n-3 ftty cid levels in pork will, however, lso hve to be done in concert with dequte levels of ntioxidnt protection to mintin pork qulity. In the present experiment we dded 40 IU of vitmin E per kilogrm of feed, nd lthough this ppered dequte for niml growth nd performnce, it ws likely less thn dequte to chieve optiml pork qulity when feeding higher levels of flx for longer durtions (Pettigrew & Esnol, 2001). Designing flx feeding progrms to increse n-3 ftty cids in pork will, therefore, lso require optimiztion of vitmin E levels while tking into considertion economic returns to producers for dded investments. Acknowledgements Fig. 1. Effect (men ± stndrd error) of feeding 5%, 10% nd 15% co-extruded flx different periods prior to slughter on totl n-3 ftty cid content. pigs but prdoxiclly to chieve high levels of n-3 ftty cids in mrket weight pigs, reltively long feeding periods re still required. To yield the sme level of n-3 ftty cid enrichment in bckft, however, shorter feeding periods with higher levels of dietry flx pper to be more efficient thn longer feeding periods with lower levels of dietry flx. To produce n-3 enriched pork products, however, both the level nd consistency of enrichment re importnt. Consistency from feeding lower flx levels for longer durtions ws observed to be higher thn for high levels for shorter durtions. As shown in Fig. 1, feeding 5% co-extruded flx for 12 weeks resulted in lower stndrd error thn feeding 10% for 8 weeks or 15% for 4 weeks (0.26 vs vs. 0.64, respectively). When feeding 5% flx for 8 weeks, the stndrd error vlue ws lower thn feeding 10% flx for 4 weeks (0.25 vs. 0.30), even if both diets resulted in similr totl n-3 ftty cid content (Tble 7). A similr effect ws observed when the vribility from 10% to 12 weeks nd 15% to 8 weeks diets were compred (0.38 vs. 1.18). Hence to more consistently yield the sme level of n-3 ftty cid enrichment in bckft, shorter feeding periods with higher levels of dietry co-extruded flx pper to be more efficcious thn longer feeding periods with lower levels of dietry flx. In prcticl terms, to be ble to produce pork with consistently high levels of n-3 ftty cids, one will therefore likely need to strike blnce between feeding high levels of flx for short durtions, which provides efficient n-3 ftty cid deposition, nd feeding lower levels of flx for longer durtions, which provides more consistent rtes of deposition. 4. Conclusions Feeding up to 15% flx for 8 weeks hd no impct on live niml performnce. Feeding ny level of flx for 12 weeks reduced verge dily gin but feeding higher levels of flx improved feed efficiency. The ddition of 50:50 mix of extruded flx/pes to pig diets provided highly vilble source of 18:3n-3 yielding n-3 ftty cid enrichments in bckft comprble to reports when feeding supplementl flx seed oil. Enrichments of n-3 ftty cids, ccording to Cndin stndrds, cn be obtined in pork products when reltively low levels of bckft from pigs fed flxseed re included. Incresing the durtion of flx supplementtion resulted in plteu in bckft totl n-3 ftty cids when feeding 5% flx for 8 weeks but plteus were not evident when feeding either 10% or 15% flx for 12 weeks. Hence feeding higher levels of co-extruded flxseed for shorter periods vs. lower levels for longer peri- Finncil support ws provided by Ssktchewn Agriculture Development Fund nd Flx Cnd Dr. N. 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