EFFECT OF COLD EXPOSURE ON MILK PRODUCTION AND ENERGY BALANCE IN THE LACTATING EWE

EFFECT OF COLD EXPOSURE ON MILK PRODUCTION AND ENERGY BALANCE IN THE LACTATING EWE G. E. McBRIDE a R. J. CHRISTOPHERSON Departmet f Aimal Sciece, Uiversity f Alberta, Emt, Alberta T6G 2E5. Receive 28 July 1983, accepte 19 Dec. 1983. Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. McBre, G. E. an CrsrpEsN, R. J. 1984. Effect f cl expsure milk pructi a eergy balace i the lactatig ewe. Ca. J. Aim. Sci. 64: 379_389. The lactatial perfrmaces f shr ewes chrically expse t a thermeutral (21 + l"c) r cl (0 + 1"C) evirmet were cmpare i tw experimets. Heat pructi measure after 1, 2r a 41 ays f cl expsure was icrease by 20V (P<0.05), 43V (P<0.01) a 55V (P<0.001), respectively, ver thermeutral ctrl values. I bth experimets, cl expsure icrease milk fat ccetrati (P<0.05). Milk prtei a lactse ccetratis were maitaie i exp. lbutteetbeicreaseiexp.2asaresultfclexpsure.milkbtaie frm the cl-expse ewes was characterize by a relative ecrease i shrt-chai fatty aci secreti (P<0.01). Althugh milk cmpsiti was affecte by cl stress, aily milk pructi was t sigificatly altere; as a csequece, ttal eergy lst i the milk tee t be slightly higher fr the cl-stresse ewes. The icrease eergy lst as heat a i the milk urig cl expsure resulte i a et eergy eficit thrughut mst fthe experimetal peri. The preset ata suggest that the lactatial perfrmace f a ewe ursig a sigle lamb is t impaire by chric expsure t a ambiet temperature f 0"C. Key wrs: Cl, milk pructi, milk cmpsiti, ewes, eergy balace [Effets e I'expsiti au fri sur la pructi laitire et le bila 6erg6tique chez le brebis e lactati.l Titre abrg6: R6acti es brebis au fri. O a cmpar6 le reemet laitier e brebis tues exps6es e fag chrique i u milieu thermeutre (21+ l'c) u fri (0+ l'c) as le care e eux exp6rieces. La chaleur pruite aprs l, 2l et 41 jurs 'expsiti au fri avait respectivemet augmet6,e 2OVa (p<0,05), e 43V (p<0,01) et e 55V (P<0,001) par rapprt aux t6mis e milieu thermeutre. Das les eux exp6- eces, I'expsiti au fri accrit la teeur e matire grasse u lait (p<0,05). La ccetrati es prties et u lactse 'a pas vari6 lrs e la premire expriece, mais a eu teace i augmeter as la sece la suite Jl'expsiti au fri. Le lait es brebis exps6es se caract6rise par ue baisse relative e la ccetrati es acies gras i chaie curte (p<0,01). Bie que la cmpsiti u lait sit affect6e par le fri, tel 'est pas le cas e la pructi qutiiie e lait. Par cs6quet, l'6ergie ttale perue as le lait a teace i 6ire l6gremet plus 6lev6e chez les brebis exps6es au fri. La hausse e la quatit6 'eereie perue sus frme calrique a etrai u ficit et sur le pla 6erg6tiqu" pjut la majeure partie es essais. Les 6es recueillies suggret que l- reemet laitier e la brebis qui allaite u seul ageau e subit pai le ctiecup 'ue expsiti chrique i ue temprature e 0C. Mts cl6s: Fri, pructi laitire, cmpsiti u lait, brebis, bila 6erg6tique Ca. J. Aim. Sci. 642379-JB9 (Jue 1984) 379

380 CANADIAN JOURNAL OF ANIMAL SCIENCE Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. At ambiet temperatures belw the lwer limit f the thermeutral ze, sheep cvert mre chemical eergy t heat (Graham et al. 1959) a may igest their fee less efficietly (Natial Acaemy f Scieces- Natial Research Cucil (NAS-NRC) 1981). Uless aitial f eergy ca be prvie t cmpesate fr the icrease eergy emas i a cl evirmet, the availability f metablizable eergy fr pructive prcesses may be limite. Durig lactati, whe fee itake may alreay be at r ear a maximum level, the impsiti f cl citis cul therefre have severe csequeces the lactatial perfrmace f the ewe. I aiti, cl expsure may irectly limit the sythetic capacity f the mammary gla by reucig mammary gla temperature, as suggeste by Jhs (1976), r may act iirectly, by affectig the uer's bl supply (Thmps a Thms 1977; Thms et al. 1979; ThmPs 1980). As well, chages i ecrie balace iuce by cl expsure might sigificatly alter the metablism f the mammary gla (Faulker et al. 1980; Rbertshaw l98l). These evelpmets - may als serve t limit the milk-prucig capacity f the cl-stresse ewe. I a evirmet where bth the ffsprig a ewe are cl stresse, a reucti i milk supply is i irect cflict with the icrease eergy emas f the lamb. A cl-iuce epressi i milk yiel may be ffset, at least i part, by chages i milk cmpsiti, icreasig the eergy value f the milk (Clarke et al. 197 6;Thms et al. 1979; Faluker et al. 1980). Aitially, cl stress may iuce a icrease appetite rive i the yug sucklig lambs, as has bee shw t ccur i clstresse mature sheep (Baile a Frbes 1974) a i a lib bttle-fe lambs (Gibb a Peig 1972), which may stimulate mammary metablism. The et effect f these factrs bth the quatity a quality f milk pruce by the cl-stresse lactatig ewe is ifficult t preict. The preset stuy was esige t examie the ifluece f prlge cl expsure urig lactati the metablism' milk yiel a milk cmpsiti f ewes ursig sigle lambs. MATERIALS AND METHODS Experimet I ANirraels. Five mths prir t the start f the experimet estrus was sychrize usig a hrme treatmet (merxyprgestere-acetateimpregate vagial spge, 500 ru PMSG ijecli) i a grup f 16 Sufflk-crss 2-yr-l ewes. Seve t te ays prepartum' the ewes were itruce t the experimetal rati, csistig f a pellete'l5vabarley-25v alfalfa meal mixture (ctaiig apprximately 4.lV crue prtei a ry matter basis). Oe t three ays pstpartum, fur ewes ursig sigle lambs a iu. e*., ursig twi lambs were selecte; ewes ursig tw ffsprig were reuce t a sigle lamb at this time. The ewes were stratifie accrig t by weight a sex f lamb' type f birth (sigle, twi) a materal by weight' a assige fr a 8-wk peri t either a ctrl (CON) (huse at 2l-r 1'C)' r cl-expse (CE) (huse at 0 + lc) treatmet grup' The experimet was esige t etermie the effect f cl expsure the heat pructi, milk pructi a cmpsiti f lactatig ewes. Each ewe-lamb pair was cfie t a 7.2x1.2-m metablic crate withi a ctiuusly-lit metablism rm r temperature-ctrlle chamber. Durig a 5- t 7-ay aaptati peri, bth treatmet grups were kept at a imbiet temperature f 2l'+ l'c while the aimals were accustme t the experimetal prceures a equipmet' Aitially, the ewes receive i.m. ijectis f retil (75 mg)' chlecalciferl (0.94 mg) a a-tcpherl (16 mg) a were shr t a fleece epth f apprximately I cm. T maitai a relatively cstat level f isulati, the ewes were reshr at 2- wk itervals. Durig the aaptati a experimetal peris, fee was ffere twice aily (0800 i 1600 h) at a level f 100 8'kg-rs'6ut-r t the CON ewes a 112 g'kg - '4ut-r t the CE ewes i rer t maiiaiby weight. Free access t water a cbalt-iize salt was als prvie. Her puctln. The heat pructi (Hp) f the ewes was mitre ays l,2l a 4l f the experimetal peri, crrespig re-

MCBRIDE AND CHRISTOPHERSON - RESPONSES OF EWES TO COLD 381 Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. spectively t wk 2, 5 a 8 flactati. The first set f measuremets was perfrme after the CE ewes ha bee expse ft 24 h t 0'C. Estimati f heat pructi was base the measuremets f respire gas, V, a Vcr, ver a 24-h peri usig a pe-circuit respiratry patter aalyzer (Yug et al. 1975) cecte t a respiratry h (75 x 70 x 45 cm), thrugh which air was raw at a rate f 70-15 L'mi t, crrecte fr staar temperature a pressure. This apparatus allwe rmal access f the ewe t fee a water but i t restrict lyig, staig r ursig activities. Mrr-r pucrln AND cmpsitin. Pretreatmet iffereces i milk yiel a cmpsiti were assesse by milkig the ewes at the e f the aaptati peri, prir t reucig the temperature t 0'C i the tw chambers husig the CE ewes. Durig the experimetal peri milk pructi a cmpsiti were assesse ce weekly (wk 3-8 f lactati). Milk yiel was etermie usig a xytcihamilkig prceure. Betwee 0800 a 0900 h the ay f cllecti each lamb was cfie t a wire cage withi its am's pe. Milk was cllecte by ijectig 5 USP xytci i.m. a rapily ha-milkig bth halves f the uer. After milk flw ha cease, a aitial 2.5 USP xytci was give i.m. a ay resiual milk strippe frm the uer. The milk btaie frm this first cllecti was iscare. The xytci-hamilkig prceure was repeate 2.5 h later a the cllecte milk was weighe t the earest gram. Daily milk yiel was estimate by multiplyig the 2.5-h level f milk pructi by a factr f 9.6. Subsamples f the cllecte milk were immeiately straie thrugh cheeseclth, place i sample vials ctaiig ptassium ichrmate as a preservative a stre at 4"C. Subsequetly, percet fat, prtei a lactse f each milk sample were etermie i uplicate usig ifrare aalysis (Assciati f Official Agricultural Chemists (AOAC) 1980). The grss eergy value f the milk was calculate accris t the frmula use by Kleiber (1975). Experimet 2 ANIIraeLs. Te yearlig Sufflk-crss ewes ursig sigle lambs were use i a experimet esige t measure milk pructi a cmpsiti by cl-expse ewes. The ewes were selecte, average, 12 ays after parturiti a assige fr a 56-ay peri t e f tw treatmet grups, as escribe i exp. 1. Each ewe-lamb pair was cfie t a 0.9 x 1.8-m pe bee with w shavigs. A rati f 75V rlle barley a 25V alfalfa pellets (ctaiig apprximately 14.0V crue prtei a ry matter basis) was fe t each ewe i tw equal alltmets (0800 a 1600 h) at a level f 112 B.kg-.r.4ut-t a free access t water a cbalt-iize salt was prvie. By weight chages were mitre by weekly weighigs. Other maagemet practices icluig shearig a vitami ijectis were as escribe previusly. Mrr-r pucrrn AND cmpsrrrn. Milk pructi was estimate ce weekly urig wk 4-8 f lactati usig a weigh-suckle-weigh techique. At 0700 h the ay f measuremet the lamb was separate frm the ewe by placig it i a wire cage withi its am's pe. At 0800 h the lamb was permitte t suckle a ay milk remaiig i the uer was strippe by ha. The lamb was the replace i the cage a allwe t suckle at 3-h itervals ver a ttal eri f 24 h. The quatity f milk pruce- at each sucklig peri was etermie by weighig the lamb t the earest gram immeiately prir t a fllwig ursig, the ifferece i weight beig take as the weight f milk csume. Ay feces r urie vie by the lamb urig the sucklig peri were als cllecte a weighe. Daily milk pructi was estimate by ttallig the results frm the eight separate sucklig peris. Twety-fur hurs fllwig the etermiati f milk yiel, a milk sample was cllecte fr aalysis. By separatig the ewe a lamb, milk was allwe t accumulate i the mammary gla ver a 3-h peri a was the cllecte by ijectig 5 USP xytci i.v. (ugular vei) a rapily ha-milkig bth halves f the uer. Subsamples fr aalyses f fat, prtei a lactse were prepare a stre as i exp. 1. Separate, uplicate l0-ml subsamples f milk were freeze-rie t etermie the ttal slis ctet r were frze a kept at -40"C fr later aalysis f fatty aci cmpsiti. Milk eergy values were estimate base aalyze cmpsiti (Kleiber 1975). Mrlr rerry AcrD cmpsrrrn. Samples f milk fat fr etermiati f fatty aci cmpsiti were extracte accrig t the meth f Rese-Gttlieb (AOAC 1980) a methyl esters prepare as escribe by Mrris a Smith (1964). The resultig hexae sluti f methyl

382 CANADIAN JOUR.NAL OF ANIMAL SCIENCE Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. esters was ijecte irectly t a Varia Mel 3700 gas chrmatgraph fitte with a flame iizati etectr a aalyses carrie ut usig quarex gas capillary clums (60 m x 0.25 mm i..) cate with Silar 10C. Clum temperature was hel at 100'C fr 6 mi, the prgramme t rise at a rate f l2"clmi t a fial temperature f 198"C, which was maitaie fr 20 mi. Ijectr a etectr temperatures were kept at 250'C. The peak areas f the separate fatty acis were measure usig a Hewlett-Packar 3353 Data System a ietificati f the peaks was mae the basis f reteti time a cmparis with kw methyl esters. The l2 largest fatty aci peaks were chse fr measuremet a these represete greater tha90v f the ttal fatty acis i the milk. Statistical Aalysis I each f exps. I a 2 treatmet iffereces fr each samplig peri were cmpare usig the Stuets /-test (Steel a Trrie 1980). Withi a treatmet grup, ata cllecte frm several samplig peris were aalyze usig least squares aalysis f variace a, where sigificat iffereces existe, meas were cmpare usig the Stuet-Newma-Keuls test f mea iffereces (Steel a Trrie 1980). RESULTS Experimet 1 Bv wbrcr. Iitial mea by weight f the CON a CE grups, respectively, average 56.8 + 1.4 kg a 55.5 I 1.0 kg a i t chage sigificatly (P>0.05) thrughut the experimet. HsRr pucrrn. Heat pructi measure after 24 h, 21 ays a 41 ays Stage f lactati (wk) 2 5 8 f cl expsure respectively, was 1.76 kj.kg-t.h ' (P<0.05), 3.85 kj'kg-t'6*t (P<0.01) a 5.31 kj'kg - t '6- t (P<0.001) greater i the CE ewes tha the ctrl aimals (Table 1). While the heat pructi f the CON ewes i t vary ver the curse f lactati (P>0.10), heat pructi i the CE ewes rse (P<0.05) with icreasig urati f the experimet. MILx prucrln. Pretreatmet milk yiels were similar fr bth grups (P>0.10), averagig 1662-t 179 glay a 15'76-r2ll glay fr the CON a CE ewes, respectively. Milk pructi (g/ay) results cllecte thrughut the experimetal peri are shw i Table 2. Theevelpmet f mastitis i 2 CE ewes a 1 CON ewe ear the e f the trial reuce the umber f aimals available fr aalysis f milk pructi. Milk yiel i t iffer betwee grups (P>0.10) except fr wk 5 f lactati whe milk pructi tee t be epresse i the CE ewes (P<0.06) a urig wk 8 f lactati whe milk yiel measure i 2 CE ewes was lwer (P<0.05) tha that measure i 3 CON aimals. Overall mea milk pructi values faile t reveal ay ifluece f temperature treatmer (P>0.10). Mrr-r cupsltln. Ccetratis f fat, prtei a lactse i the milk cllecte prir t the start f the temperature treatmet were similar fr bth treatmet grups. There was a efiite tre twars i- Table 1. Heat pructi f the ctrl a cl-expse ewes, experimet I Heat pructif (kj'kg r'h r) Durati f cl expsure (ays) cn (4)+ ce (4) I 2l 4l 8.87!0.42* 9.04 + 0.29** 9.63!0.42 9.17!0.21 t Values redreset mea + SEM. * Number 1 aimals per treatmet i paretheses. a-c Meas withi a clum fllwe by a ifferet letter are sigificatly ifferet (P<0.05). x,** Treatmet meas are sigificatly ifferet at P<0.05 a P<0.01, respectively. c Treatmet meas,ue sigificatly ifferet (P<0.001) 10.63 t 0.50 t2.89 + O.67b 14.94 t0.35c 12.81 i 0.59

McBRIDE AND CHRISTOPHERSON - RESPONSES OF EWES TO COLD 383 Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. Table 2. Daily milk pructi f the ctrl a clexpse ewes, exp 1 Stage f Milk pructi (g/ay)i lactati CON (4)f CE (4) 3 5 6 7 8 Overall Mea 1586+ 69 1671 + 103 1797 + 92 144t + t48 1253t 80$ 1398+ 66$ 1561 + 52 1895+215 1588 + 74 1482 + 19'19 1555 + 175$ 1308+ 69$ l, + 15llx 1541 + 68 t Values represet mea + SEM. * Number f aimals per treatmet i aretheses. $ Value represets mel * SEM f three aimals. fl Value represets mea t SEM f tw aimals. p Treatmet meas are sigificatly ifferet (P<0.06). x Treatmet meas are sigificatly ifferet (P<0.05). crease milk fat ccetrati i the clexpse ewes (Table 3); verall milk fat ccetrati average i.2o-r0.45va fr the CON ewes a 9.1I +- O.42V fr the CE ewes (P<0.01). Overall milk prtei a lactse ccetratis measure urig the treatmet peri were similar fr bth grups f aimils (P>0.0s). MIlx Becy value. The aily eergy utput i milk tee t be higher (p<0. t0) as a result f cl expsure. averagig 7.67'+0.41 MJ.ay-'fr the CON ewei a 8.62 -r 0.32 MJ. ay - t fr the CE ewes. Experimet 2 By werchr. As i exp. 1, the iitial mea by weights f 38.0 -+ 2.lkgfr the CON grup a 39.8-F3.1kg frthe CE grup, i t chage sigificatly (P>0.05) urig rhe experimer. MIlr prucrrn. The milk pructi f bth treatmet grups i exp. 2 was markely lwer tha urig exp. I (Table 4). Develpmet f hypthermia i I CE ewe urig wk 4 f lactati resulte i the remval f the ewe frm the experimet fr a 24-h peri; csequetly, mea milk pructi urig this e peri reflects the results btaie frm fur CE a five CON ewes. Althugh milk pructi tee t be slightly lwer i the CE ewes, the effect f temperature was t sigificat. Mx cupsrrrn. Percetage milk fat tee t be elevate i the CE grup (wk 5, P<0.10; wk 7, P<0.01) (Table 5) a rse slightly i bth grups f aimals ver the curse f lactati. Overall, mea milk fat ccetrati was greater (P<0.05) fr the CE ewes. Milk prtei ccetrati als tee t be elevate i the cl-expse aimals a was sigificatly greater (P<0.05) urig wk 7 f lactati, after 5 wk f cl expsure. Data ple frm 5 wk f sample cllecti reveale a sigificat (p<0.001) elevati i milk prtei ccetrati as a result f cl expsure. Except urig wk 4 f lactati, whe milk lactse ccetrati tee t be higher i the CE ewes (P<0.10), weekly aalysis f the milk faile t reveal ay treatmet-iuce iffereces i percetage milk lactse. Hwever, ple aalysis frm 5 wk f sample cllecti suggeste a slight icrease (P<0.10) i lactse ccetrati as a result f cl expsure. Mrr-x BNecy value. Daily eergy utput i the milk average 3.36 -r O.23 MJ a 3.63-r 0.31 MJ fr the CON a CE ewes, respectively (P>0. 05). Mr arry ACrD cmpsrrrn. As there were chages i milk fatty aci cmpsiti ver time (P>0.05), the results frm 5 wk f sample cllecti were ple fr each treatmet grup a mea values are shw i Table 6. I the CON a CE ewes? respectively, shrt-chai fatty acis (less tha 16 C i legth) frme 32.9V a 26.3V f the tral milk fatty acis (P<0.01) whereas the prprti f lgchai fatty acis (greater tha r equal t 16 C i legth) was, respectively, 67.l% a 73.3V (P<0.02). Alteratis i fatty aci cmpsiti reflecte lwer percetages f C4:0, C6:0, C8:0 (P<0.01), Cl0:0, Cl2:0, a Cl4:0 (P<0.05) fatry acis bur higher prprtis f C18:0 (P<0.06) a

384 CANADIAN JOURNAL OF ANIMAL SCIENCE sss-q%%f \Oq9!! * ; x +r +t +l +l +l +l +l +l Oi-O\r\O Nr @ r r h Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. a B X E () F s s c s * z U s s-$-q B%?. @$@; OOO--C)6 r O +l+t+l+l+ +l+ +l \ONS$r\O- i@64* h6h6h -s-s (! cs 5S :336 - NiN*r* - cic; +t +r +l +l +l +l +l +l qe\iiqq 3.+* s B g ${%q **6*-N- -r@+r -: +l +l +l +l +l +l +l +l rrr6o* 6 r\$ h+h '' * N @4= * --N 5ie+rir i + cjjj +t+r+l +l+l+l +l r<fr\ * -Orh r i6is. @4 -Nrf Cl 6O * rf N\O t J-J-j +t +r +l +l +l +l +l +l i \f\ohro,o N ; 6..ss e,i,6 5 0 t E 4!^^ 9Vq =\e 9.,i2: ih- ;i: -- =E9 E'= =F: ' g;i g E E -fl.b q Eg) '' >=E '!!= c! ) Fc >" EbE E A FE > E>E!=E,e f! Fi:=s- EE "a v i'. ".'. E! F. +l - +l +l 6 E-4.: E E F F-: g; 9:9 9r. U : H*EE-62; F i I I! c F tr ;i.= q tr ".= 9l:,i 3 F e 3 F= H E a'th.+e:eh H! y y- c F: EEzz$gEE SZSs6tiF ++a- \ B* 6

McBRIDE AND CHRISTOPHERSON - RESPONSES OF EWES TO COLD 385 Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. Table 4. Daily milk pructi fthe ctrl a clexpse ewes, exp. 2 Stage f lactati (wk) ^ ) 6 7 8 Overall mea Milk pructi (glay)+ cn (5)+ ce (5) '753 + 6l 67'1! 56 65'7 + 95 662+ 102 605 + 104 6'71+ 37 719+ 10lS 516+110 602+ t10 630 + 121 636 + 102 616+ 47 1 Values repeset mea + SEM. { Number f aimals per treatmet i paretheses. $ Value represets mei * SEM f fui aimals. C18: l(cis) (P<0.10) fatty acis i the milk cllecte frm the CE ewes. DISCUSSION Heat Pructi The heat pructi (Hp) ata fr the ctrl lactatig ewes i exp. I clsely agree with previus results btaie by Thmps et al. (1981) a by Dege a Yug ( l e82). Cmpare t the lactatig ewe, Dege a Yug (1982) reprte a icrease i Hp f 50-62V ue slely t lactati, thus eablig the lactatig ewe t withsta a greater egree fcl expsure befre becmig stresse. Hwever, the results f the curret experimet iicate that a ambiet temperature f OC is belw the lwer limit f the thermeutral ze f the shr, lactatig ewe; after 24-h expsure t OC, the Hp f the CE ewes was elevate by 20V ver the ctrl value. The greater fee csumpti a assciate heat icremet f feeig f the CE ewes ca accut fr less tha a 2V icrease i Hp ver the ctrl level (Kleiber 1975). Similarly, Thmps et al. (1981) reprre that a 48- h expsure t l"c icrease the Hp f the shr lactatig ewe by 32V, iepeet f ay utritial factrs. As the legth f cl expsure icrease, Hp measure after 2I a 41 ays f cl expsure, respectively, was l43% a l55v f the ctrl values. The rise i Hp + N ' a a (J F 6 (t),6 @* q': c'l': -: q +t +t +t +t +t +l N\OONO N 09909v? 9 hhhh \r $ -i:-i-i-i -i +l +t +l +t +l +l *N\ \ 9! 1 hhh h * @** *r *-v * -i,i -i -{ -{ ; +t +t +t +t +t +l 6NC)C) @ f - +-;r;r;r; r; \\h qa:-q q r +t +t +t +r +t +l N NNC) * rr : +.+.++r; + x lj*q-qx % inro\$ \l al-$ a * \O lc?q c-! +t +l +t +t +t +l 6 ** O -*$$ 6irci i \rcllcl 9cl\9 a +t +l +t +t +t +l \+ c) 6 q\9 9 r r <lh\r r a,1 ^,!l i.10 a h,< 9-r65 tr v:y -i 9.YV u 6-v. 6:EEtf E:i!- I= E)t F:i q =q ts _Y ZsiE = =: >E>Eqsg H 6H -eq'= 9.q E 'E E h +l : +l 5.9.gr'A C i e- q 6 -. 11 E* U p, E F-F-=E." E- C'-'-!w 6 E E ; E F E 6a>Fc/-se q:!=-tr I - +C F E O ::.1HFP9E YiX..YlcE= 5=;EEEE ; >Z>aFt-: == e I,E ++@ B + *

386 CANADIAN JURNAL F ANIMAL sclence Table 6. Fatty aci cmpsiti f the milk btaie frm the ctrl a cl-expse ewes, exp. 2l Percet f ttal milk fattv acis Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. C4:0 C6:0 C8:0 C10:0 Cl2:0 Cl4:0 C16:0 C16:1 Cl8:0 Cl8:1 (lras) C18:1 (cis) Cl8:2 shrt-chai fatty acis (<16C) Lg-chai fatty acis (>16C) 1.7 + 0.10 2.5 + 0.15 3.t!0.24 9.9 + 0.82 5.5 + 0.47 10.1 + 0.40 25.2!0.17 2.0 + 0.12 9.6 + 0.72 3.3 + 0.43 22.8 + 1.52 4.2+0.24 32.9 + 1.83 6'7.t!t.82 1.3 + 0.09 2.0 + 0.09 2.4 + O.15 7.9 + 0.55 4.3 + 0.31 8.4 t 0.48 26.2!0.62 2.0 + 0.07 11.2 + 0.45 3.0 + 0.35 26.5 + 1.41 4.3 + 0.32 26.3!1.51 73.3! 1.47 P<0.01 P<0.01 P<0.01 P<0.05 P<0.05 P<0.05 P<0.06 P<0.10 P<0.01 P<0.02 tvalues represet mea t SEM f ata cllecte frm five aimals per treatmet ver 5 wk f lactati. f the chrically cl-stresse ewes presumably is eviece f the evelpmet f metablic acclimati, similar t the prcess that ccurs i sheep expse t witer citis (Webster et al. 1969). As well, by fat i the CE ewes may have bee icreasigly lst ver the curse f the experimet, resultig i less isulati a a greater susceptibility t cl. This pssibility was t irectly examie i the preset experimet a was t reflecte by ay chage i by weight, althugh it is suggeste by the cl-iuce chages i milk fatty aci cmpsiti. Net Eergy Balace Frm the measuremets f heat pructi a milk eergy utput, the ttal eergy expeiture f the ewes i exp. 1 was estimate a cmpare t their metablizable eergy itake, calculate frm publishe estimates f the ME value f barley a alfalfa pellets fr sheep (NAS-NRC l9l5). Assumig that the ME value f the iet was similar fr bth treatmet grups, average et eergy balace urig the experimet was calculate t be - 0.24 MJ/ay a - 1.80 MJ/ay fr the CON a CE ewes, respectively. This agai suggests that the cl-stresse ewes must have relie the mbilizati f by stres t a greater extet tha the CON aimals t meet their maiteace a lactatial requiremets. Milk Pructi The milk pructi ata cllecte urig exp. I clsely agree with Dege a Yug's (1982) estimate f milk pructi i ewes btaie frm the same flck, base water turver i the sucklig lambs. The level f milk pructi measure urig exp. 2, hwever, is lwer tha previus values. The lwer milk pructi i exp. 2 cmpare t exp. 1 may have bee relate t the yuger age, lighter by weight a umber f cmplete lactatis f the experimetal ewes. It may als have bee, i part, a result f the ifferet techiques emplye t estimate milk pructi (McCace 1959; Cmbe et al. 1960). I bth f the preset experimets, milk pructi f the ewe was t affecte by prlge cl expsure espite sigificat temperature-iuce chages i the ewe's eergy balace. I ctrast, previus stuies have shw that milk secreti ca be epresse i cws by lw temperatures experiece urig witer citis

McBRIDE AND CHRISTOPHERSON - RESPONSES OF EWES TO COLD 387 Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. (MacDal a Bell 1958) a i the labratry, by lcal clig f the uer (Hlmes 19'71). Uer labratry citis, acutely cl-stresse sheep a gats, milke twice aily, reuce their milk secreti (Clarke et al. 1976; Thmps a Thms 19771, Thms et al. 1979, 1980; Faulker et al. 1980; Thmps et al. 198 1). The iscrepacy betwee the preset results a previusly reprte bservatis with cl-stresse lactatig aimals is mst likely relate t the urati f cl expsure a the ifluece f the sucklig yug. Recet research by Thmps (1983) iicate that acute expsure t - l'c f ewes ursig sigle lambs resulte i ly a small epressi i milk secreti, althugh milk yiel i ewes sucklig twi lambs was greatly reuce. Bth ur results a thse f Thmps (1983) suggest that whe the eergy balace fthe ursig ewe is t severely taxe (i.e. ursig a sigle lamb), expsure t a merately cl evirmet es t etrimetally affect milk pructi. Milk Cmpsiti I the ewes huse at a thermeutral temperature, prtei, lactse a fat ccetratis f the milk average 5.O9V, 5.60V a 7.4l%a, respectively, i exp. 1, while i exp. 2, average values f 4.80V, 5.46V at.9l%, respectively, were fu. Similar estimates f ewe's milk cmpsiti have bee previusly reprte (Williams et al. 1976; Trres-Heraez a Hhebke 1979). Cl expsure resulte i a sigificat icrease i percet milk fat. Chages i milk prtei a lactse ctet were icsistet i the tw experimets but suggeste that lactse a prtei ccetratis were maitaie r slightly icrease urig chric cl expsure. N ther stuies have examie chaqes i milk cmpsiti urig prlge c"l expsure. I acutely cl-stresse gats, ttal lactse yiel ecreases urig cl ex- psure (Clarke et al. 1976; Faluker et al. 1980) but is relate t a sigificat reucti i ttal milk yiel rather tha i lactse ccetrati (Faulker et al. 1980). Clarke et al. (I97 6) fu that milk prtei a fat yiels were sigificatly epresse after 24 h f cl expsure but shwe sme recvery after 48 h f treatmet, espite a ctiue epressi i the rate f milk secreti. Althugh t reprte, these ata may iicate that fat a prtei ccetratis were icrease i the milk cllecte after 48 h f thermal treatmet. Thms et al. (1979) als etermie that ttal milk fat secreti i the cl-stresse gat was maitaie althugh milk secreti was epresse. Aitially, several stuies have etermie that milk butterfat percet icreases whe cws are expse t a lw ambiet temperature (see review by Jhs (1976)). Milk Fatty Aci Cmpsiti I rumiats, milk fatty acis ragig frm 8 t 14 C i legth are rmally sythesize e v i the mammary gla frm carb skelets prvie by plasma B- hyrxybutyrate a acetate (Lizell et al. 1967),whereas fatty acis lger tha 16 C i legth are usually erive frm plasmafree fatty aci a triglycerie pls (Ais et al. 1967). Glucse carb cat be irectly use fr fatty aci sythesis i the rumiat mammary gla (see review by Lizell a Peaker (1911)); hwever, mammary glucse xiati via the petse cycle prvies a imprtat surce f reucig equivalets ecessary fr fatty aci sythesis (Bauma a Davis 1974). Stuies perfrme with rumiats huse i thermeutral evirmets have uifrmly reprte that lg-chai fatty acis frm the largest prprti fthe ttal fatty acis secrete i milk. I the ewe, Thmps a Ge (1981) fu that palmitate * leate cstitute apprximately 63.ZV f the ttal milk fatty acis a, i the preset stuy, they frme 5l.3V f the ttal milk fattv acis. Shrt-

388 CANADIAN JOURNAL OF ANIMAL SCIENCE Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. chai fatty acis (less tha 16 C i legth) have bee fu t cmprise 27.lV f the ttal fatty aci secreti i ewes (Thmps a Ge l98l), agai crrespig well with the average value f 32.9V etermie i the curret stuy. I the preset experimet, prlge cl expsure resulte i a relative ecrease i mammary secreti f all f the shrtchai fatty acis, but a icrease i lgchai fatty aci secreti, reflectig a teecy twars elevate secreti f stearate (Cl8:0) a the cls frm f leate (C18:1). Clarke et al. /1976) a Thms et al.,1919) have bth etermie that a shrtterm expsure (48 h f lactatig gats t a merate cl stress, sufficiet t icrease heat pructi by 28-467, ecrease milk secreti f shrt-chai fatty acis but icrease that f lg-chai fatty acis, especially f leic aci. The uerlyig mechaisms resultig i chages i mammary fatty aci metablism urig cl expsure have ly bee stuie i the acutely cl-stresse gat. A shift away frm shrt-chai fatty aci secreti i the milk f the cl-stresse gat ca be relate t a ecrease supply a uptake f acetate (Thms et al. 1979) a B-hyrxybutyrate (Faulker et al., upubl. ata, cite by Faulker et al. (1980)), a a reuce mammary uptake f glucse (Faulker et al. 1980), resultig i a ecrease supply f carb skelets a f reucig equivalets ecessary fr e v fatty aci sythesis. O the ther ha, free fatty aci supply a mammary uptake are icrease urig cl expsure (Thms et al. 1919), supprtig a icrease release f lg-chai fatty acis i milk. I summary, the ata cllecte i the preset experimets i t reveal ay etrimetal effect f prlge merate cl expsure f the lactatial perfrmace f the ewe ursig a sigle lamb. Our results suggest that, althugh the eergy balace f the ewe was altere by cl expsure, milk yiel a eergy utput were maitaie. Further wrk will be require t islate the factrs respsible fr the bserve respses. ACKNOWLEDGMENTS This research was supprte by peratig grats prvie by the Agricultural Research Cucil f Alberta a the Natural Scieces a Egieerig Research Cucil f Caaa a by a Natural Scieces a Egieerig Research Cucil f Caaa a by a Natural Scieces a Egieerig Research Cucil f Caaa Pstgrauate Schlarship (G.E'M.). Techical assistace prvie by W. Whitmre a A. Rjek is gratefully ackwlege. ANNISON, E. F., LINZELL, J. L., FAZAK. ERLEY, S. a NICHOLS, B' W. 1967. The xiati a utilizati f palmitate, stearate, leate a acetate by the mammary gla f the fe gat i relati t their verall metablism, a the rle f plasma phsphlipis a eutral lipis i milk-fat sythesis. Bichem. l- 102: 63',1-647. ASSOCIATION OF OFFICIAL AGRICUL- TURAL CHEMISTS 1980. Official meths f aalysis, 13th e. AOAC, Washigt, D.C. BAILE. C. A. a FORBES, J. M. 1974. Ctrl f fee itake a regulati f eergy balace i rumiats. Physil. Rev. 54: 160-214. BAUMAN, D. E. a DAVIS, C.L.1974.Bi' sythesis f milk fat. ib. L. Lars a V. R. Smith, es. Lactati. Vl' II. Acaemic Press, New Yrk. CLARKE, P. L., THOMSON, E. M. AN THOMPSON, G. E. 1976. Acute cl expsure a milk secreti i the gat. J. Physil. 263: t76-r'17. COOMBE, J. B., WARDROP, I. D. AN TRIBE, D. E. 1960. A stuy f milk pructi f the grazig ewe, with emphasis the experimetal techique emplye. J. Agric. Sci.' Camb. 54: 353-359. DEGEN, A. A. a YOUNG, B. A' 1982. Itake eergy, eergy reteti a heat pructi i lambs frm birth t 24 weeks f age. J. Aim. Sci. 54:353-362. FALUKNER. A., THOMSON, E. M., BAS- SETT, J. M. a THOMPSON, G. E. 1980' Cl expsure a mammary glucse metablism i the lactatig gat. Br' J. Nutr. 43: 163-170. GIBB, M. J. a PENNING, P. D. 1972. The effects f evirmetal temperature a feeig patter the perfrmace f artificially-

McBRIDE AND CHRISTOPHERSON - RESPONSES OF EWES TO COLD 389 Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. reare lambs fe cl milk substitute. Aim. Pr.15: 177-182. GRAHAM, N. McC., WAINMAN, F. W., BLAXTER, K. L. a ARMSTRONG, D. c. 1959. Evirmetal temperature, eergy metablism a heat regulati i sheep. I. Eergy metablism i clsely clippe sheep. J. Agric. Sci., Camb. 52: 13-24. HOLMES, C. W. 1971. Lcal clig f the mammary gla a milk pructi i the cw. J. Dairy Res. 38: 3-7. JOHNSON, H. D. 1976. Effects f temperature lactati i cattle. 1 Prgress i aimal bimeterlgy. The effect f weather a climate aimals, Vl. 1. Part 1. Swets azeitliger. B. V. Amsteram. KLEIBER, M. 1975. The fire f life. A itructi t aimal eergetics. Rbert E. Krieger Publishig C. Ic.. Hutigt. N.Y. LINZELL, J. L., ANNISON, E. F., FAZAK- ERLEY, S. a LENG, R. A. 1967. The icrprati f acetate, stearate a D(-)-Bhyrxybutyrate it milk fat f the islate perfuse mammary gla f the gat. Bichem. J. 104:3442. LINZELL, J. L. a PEAKER, M. 1971. Mechaism f milk secreti. Physil. Rev. 51: 56,1-597. MacDONALD, M. A. a BELL, J. M. 1958. Effects f lw fluctuatig temperatures farm aimals. IV. Ifluece f temperature milk yiel a milk cmpsiti. Ca. J. Aim. Sci. 3E: 160-170. McCANCE, I. 1959. The etermiati f milk yiel i the meri ewe. Aust. J. Agric. Res. 10:839-853. MORRISON, W. R. a SMITH, M. 1964. Preparati f fatty aci methyl esters a imethylacetals frm lipis with br fluriemethal. J. Lipi Res. 5: 600-608. NATIONAL ACADEMY OF SCIENCES- NATIONAL RESEARCH COUNCIL 1975. Nutriet requiremets f sheep. NAS-NRC, Washigt, D.C. NATIONAL ACADEMY OF SCIENCES- NATIONAL RESEARCH COUNCIL I98I. Effect f evirmet utriet requiremets f mestic aimals. Natial Acaemv Press. Washigt, D.C. ROBERTSHAW, D. 1981. The evirmeral physilgy f aimal pructi. I J. P. Clarke, e. Evirmetal aspects fhusig fr aimal pructi. Butterwrths a C., Publishers Lt., L. STEEL, R. G. D. a TORRIE, T. H. 1980. Priciples a prceures f statistics. McGraw Hill Bk C. Ic., New Yrk. THOMPSON, G. E. 1980. The istributi f bl flw i the uer f the sheep a chages brught abut by cl expsure a lactati. J. Physil. 302 379-386. THOMPSON, G. E. 1983. The itake f milk by suckle ewbr lambs a the effects f twiig a cl expsure. Br. J. Nutr. 50: l5 1-156. THOMPSON, G. E. a GOODE, J. A. 1981. Lactgeesis i ewes expse t eutral a cl evirmetal temperatures urig the last week f gestati. Aim. Pr. 32: 245-250. THOMPSON, G. 8., HARTMANN, P. 8., GOODE, J. A. a LINDSAY, K. S. 1981. Sme effects f acute fastig a climatic stresses up milk secreti i friesla sheep. Cmp. Bichem. Physil. 70A: 13-16. THOMPSON, G. E. a THOMSON, E. M. 1977. Effect f cl expsure mammary circulati, xyge csumpti a milk secreti i the gat. J. Physil. 272:187-196. THOMSON, E. M., FORSLING, M. L. a THOMPSON, G. E. 1980. The effect f cl expsure flui balace, circulatig argiie a vaspressi ccetrati a milk secreti i the gat. Pflugers Arch. 383: 241-244. THOMSON. E. M.. SNOSWELL. A. M.. CLARKE, P. L. a THOMPSON, c.e. 1979. Effect f cl expsure mammary gla uptake f fat precursrs a secreti f milk fat a caritie i the gat. Q. J. Exp. Physil. 64: 7-r5. TORRES-HERNANDEZ, G. a HOHEN- BOKEN. W. D. 1979. Geetic a evirmetal effects milk pructi, milk cmpsiti a mastitis iciece i crssbre ewes. J. Aim. Sci. 49: 410-417. WEBSTER, A. J. F., HICKS, A. M. a HAYS, F. L. 1969. Cl climate a cl temperature iuce chages i the heat pructi a thermal isulati f sheep. Ca. J. Physil. Pharmacl. 47 : 553-562. WILLIAMS, A. P., BISHOP, D. R., COCK- BURN, J. E. a SCOTT, K. J. 1976. Cmpsiti f ewe's milk. J. Dairy Res. 43: 325-329. YOUNG, B. A., KERRIGAN, B. a CHRIS- TOPHERSON, R. J. 1975. A versatile respiratry patter aalyzet fr stuies f eergy metablism f livestck. Ca. J. Aim. Sci. 55: r'7-22.

Ca. J. Aim. Sci. Dwlae frm www.rcresearchpress.cm by 148.251.232.83 04/27/18 Fr persal use ly. This article has bee cite by: 1. Ilaria Peaa, Aa Helea Dias Fracesci, Crra Dimaur, Atell Caas, Maria Sitzia. 2017. Effect f witer a sprig meterlgical citis milk pructi f grazig airy sheep i the Meiterraea evirmet. Small Rumiat Research 153, 194-208. [Crssref]