THE EFFECT OF PHASE-FEEDING ON EGG PRODUCTION AND EGG QUALITY OF WINTER-HOUSED WHITE LEGHORN HENS

Transcription

1 TH CT O PHAS-DIG O GG PRODUCTIO AD GG QUALITY O WITR-HOUSD WHIT LGHOR HS. A. CAV and R. M. c. HAMILTO Animal Research Centre, Research Branch, Agricul.ture Canada, Ottawa. Ontari KlA 0C6. Cntributin n. 1034, received 24 v. 1981, at:r'epred 4 Mal' Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. Crve,. A.,q Her,rrrr, R. M. G The effect f phase-feeding n egg prductin and egg quality f winter-hused White Leghrn Hens. Can. J. Anim. Sci Tw experiments with nine strains f Single Cmb White Leghrn hens were cnducted t cmpare laying huse perfrmance f hens given a diet f unifrm prtein cntent r a phase-feeding diet in which prtetn cntent was reduced frm 156 t 148 and then t 140 g/kg at 273 and 414, r 273 and 384 days f age. Perfrmance criteria were egg prductin, feed and prtein intake, egg, quality, egg weight, mrtality and bdy weight. Phase-feeding allwed reductins f 4.2 and 4.3c/ in prtein cnsumptin withut reducing egg prductin, mrtality r, except in ne strain, bdy weight. There was an increase f 0.57c in f-eed cnsumptin, but feed cst was reduced by l.3a/a. Phase-feeding increased Haugh units by 0.37c and decreased specific gravity f eggs in ne experiment, decreased percent visibly-cracked eggs in the ther experiment and had n effect n percent bld spts. Depending n strain, phase-feeding had a variable eftect n egg weight in exp. 1 but had n effect in the secnd experiment. Deux exp6riences nt 6t6 r6alis6es avec 9 suches de pules pndeuses. Leghrn blanches, pur cmparer le cmprtement en pullailler des pules aliment6es par deux didtes sit (1) une ratin cnstante de 156 g prt6ine par kg et (2) une diete A tris 6tapes pur laquelle la tenue de prt6ine est r6duite de 156 i 148 et ir 140 g/kg aux Ages de 2'73 et 414 u de 273 et 384 jurs. Les charactdres de perfrmances 6taient: la prductin d'eufs, cnsmmatin d'aliments et de prt6ines, pids et qualit6 des eufs, mrtalit6 et pids crprel. L'utilisatin d'alimentatin b tris 6tapes a permis de r6duire la cnsmmatin de prt6ine par 4,2 et 4,37a, sans le d6savantage de r6duire la taux de pnte, u, avec I'exceptin d'une seule suche, le pids crprel. Il y avait une hausse en cnsmmatin d'aliments de 0,5Vc, n6anmins le ctt des aliments a 6t6 r6duit par 1,3Vc. L'alimentatin I tris 6tapes a augment6 I'unit6 Haugh paro,3a/mais n'a eu aucun effet sur l'incidence des taches de sang dans les eufs. Ce traitement a fait d6critre la gravit6 sp6cifique dans une exp6rience mais a dnn6 lieu ir une chute du num6r des cquilles visiblement craqu6es. Seln la suche de pule, l'alimentatin ) tris 6tapes avait un effet variable sur pids d'euf dans la premidre exp6rience mais n'avait nul effet significatif dans l'autre exp6rience. Key wrds: Phase-feeding, prtein utilizatin, egg prductin, hen The practice f reducing dietary prtein ment at abut 40 wk f age, cinciding level as egg prductin declines (phase- with a higher energy requirement asscifeeding) is widely used fr summer-hused ated with lwer temperatures f winter, hens. A decline in prductin is cnsidered cmbines t increase the ptimum dietary t reduce the daily prtein requirement f energy: prtein (:P) rati at this age. the hen. A reductin in prtein require- The :P rati indicated as apprpriate Can..J. Anim. Sci. 62: (Sept. 1982) i82/ acl 1982 Agricultural Institute f Canada 887

2 888 CAADIA JOUR\AT- O AI{AI- SCIC Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. fr laying hens by atinal Academy f Sciences-atinal Research Cuncil (AS- RC) (1977) is 79.5 MJ metablizable energy per gram f prtein. Phase-feeding regimens brught abut by making minr increases f the :P rati frm this level during declining egg utput have enabled prtein saving t be made withut adverse effect n egg prductin (e.g. ernandez et al. 1913) r n yield f egg mass (Richter 1978). Attempts t increase :P rati substantially belw the AS-RC level in prprtin t declining egg prductin have nt been successfui since reductins in yield f egg mass (isher and Mrris 196'7) r egg numbers (Christmas et al. 1979) ccurred. The age f hens when change in dietary prtein level is made can influence feed efficiency and egg prductin. The rati f gram egg:gram prtein cnsumed was nt maintained when nly a shrt time (10-12 wk) elapsed between nset f lay and change in dietary :P rati (Sharpe et al. 1965), but when the change was made at 14.5 m f age a large change, frm 71 t 105 MJ/g prtein. culd be made withut adverse influence n egg prductin (Rlands 1980a). r winter-hused hens, ambient temperature is higher as egg prductin is declining. nergy and prtein requirements decrease simultaneusly and the ptimum :P rati may vary by nly a small degree. There is uncertainty abut the extent f decrease in efficiency f prtein utilizatin with age and abut the effect f temperature n the ptimum :P rati fr winterhused hens during the pstpeak prductin perid. Hence, the effects f phasefeeding n egg laying perfrmance and feed efficiency were studied with nine strains f hens hused in vember r December. MATRIALS AD MTHODS xperiment 1 Birds fr this experiment were grup-hused in wire cages during the brding and rearing perids (1 140 days) and managed as described by Hamiltn (1978). There were 8192 pullets hused in individual wire cages (20.3 x 40.6 cm) in a windwless huse prir t the start f the experiment at 141 days f age (29 v. 1975). These cmprised 1125 birds frm each f six lng-term selected Single Cmb White Leghrn (SCWL) strains (1,2,3,4,8 and 9) and 480 birds frm each f three unselected SCWL strains (5, 7 and 10) (Gwe and airfull 1980), plus tw SCWL hens chsen at randm The dietary treatments invlving 4096 hens each were randmly assigned within each f eight replicates. Hens frm each strain were equalll distributed between treatments and replicates, except thse tw hens chsen at randm. Hens f the cntrl treatment (treatment I ) received the same diet (diet I, Table 1) thrughut the laying perid, whereas hens n treatment 2 were subjected t phase-feeding f diet I frm l4l t 273 days, diet 2 frm 274 t 414 days and diet 3 frm 415 t 497 days l' age. Thus. dietarl prtein level was reduced frm 156 t 148 t 140 g/kg; the calculated reductin in the first limiting amin acid, lysine, fim 1.l I 6.6 t 6.2 g/kg, was relatively greater than the reductin fr prtein, because f the different prprtins f ingredients used. Dietary calcium level was raised frm 30.6 t 31.2 glkg fr the secnd (summer) perid t adjust fr the reductin in feed intake expected during the warmer summer mnths. The three diets were frmulated t be iscalric. eed and water were supplied ad libitum. Samples f each mix f feed were analyzed fr Kjeldahl nitrgen, calcium and phsphrus by the methds f the Assciatin f Official Agricultural Chemists ( I 970). The hens were weighed individually at the beginning f the experiment (141 days) and nce during each feeding perid (at 265, 365 and 49'r' days). Quantity f feed given each day and mrtality were recrded 7 days a week and egg prductin 5 days a week. Cracked and sft-shelled eggs were recrded 5 days a week, but included nly thse with visible cracks and thse nt lst thrugh the lwer cage flr f tw-tier cages. gg mass was determined n eggs laid n I day each week t facilitate calculatin f mean egg weights and cmmercial grading dne n tw 2-day cllectins during each perid. When hens were 240, 339, 388 and 450 days f age, eggs laid ver 5-day perids were used t assess shell quality frm specific gravity (SG). This was

3 CAV AD HAMILTO - PHAS-DIG O HS 889 Table l. Cmpsitin f diets (kgitnne) Ingredient Diet 1 Diet 2 Diet 3 Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. Grund crn Grund wheat Grund ats Grund barley Sybean meal (49Vc prtein) ish meal (637c prtein) Stabilized tallw Animal fat Dicalcium phsphate (22% Ca, l8.5a P) Limestne, pulverized (38ch Ca) Salt Micrnutrientsf Cmpsitin (calculated) M (MJ/kg) Prtein (g/kg) Lysine (g/kg) Methinine + cystine (g/kg) Calcium (g/kg) Phsphrus (gikg) Cmpsitin (analyzed) Prtein (gikg) (exp. 1) Prtein (g/kg) (exp. 2) Calcium Price (g per rnne in 1981) r.' l5 l ' t l.2 isupplied per tnne f diet: vitamin A, IU; viramin D,r, ICU; vitamin K, l.l g; vitamin, 3300 IU; ribflavin, 4.4 g; calcium pantthenare, 5.5 g; niacin, 22 g; flacin, 1.1 g; chline chlride, 220 g; vitamin Br2,5.5 mg; manganese, 55 g; zinc,44 g; cpper,5.5 g; idine, 1.1 g. determined by fltatin f eggs in a series f salt slutins that varied in specific gravity (SG) frm t 1.102, by increments f Internal quality measurements fr Haugh units and bld spts were made n eggs cllected during the 5-day perids at arund 240 and 450 days f age. eed and prductin data were analyzed accrding t a split-plt in time design (Steel and Trrie 1960) fr which phases ( days, 2' days and days) were cnsidered as whle plts and dietary treatments as subplts. The feed intake and egg-grade data were cllected by dietary treatment grup within replicates. Hens frm each strain were equally distributed amng treatments and replicates, hence these data were nt available by strain f bird. The data fr egg prductin, egg quality, bdy weight and percentage mrtality were analyzed using a methd f fitting cnstants (Li 1964). Mrtality, cracked and sft-shelled egg and egg-grade percentage data were transfrmed t arcsine values fbr analysis. Minimum and maximum temperatures were recrded daily 211 at 10 lcatins in the pultry huse t permit calculatin f mean dailv temeratures. xperiment 2 The secnd experiment was cnducted with 8192 pullets using the same number f each strain as in exp. 1. Management and data cllectin were unchanged except that phases were redefined t encmpass a yunger age at husing (133 days at l9 Jan. 1979) and s that phase 2 cincided with the summer perid. Thus, the three phases extended frm 134 t 213 days, frm 274 t 383 and frm 384 t 497 days. Dietary prtein levels were altered at the start f phases 2 and 3. Bdy weights were recrded at 265, 365 and 497 days, and eggs were cllected fr grading at 263, 368 and 487 days f age, and fr SG and eggweight determinatins at 240, 324 and 450 days f age. Analysis f data was the same as in exp. 1. RSULTS Dietary treatment had n significant effect (P>0.05) n hen-day r hen-hused egg

4 Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. 890 caadta JuRAr- O AI\,IA[- SCItiC prductin in either experiment (Table 2), althugh prductin was marginally higher amng hens receiving the lw-prtein diet during phase 3 ( days) f exp. 1. The quantity f feed cnsumed by hens given the phase-feeding diet was higher (P<0.05) than that f cntrl diet hens fr bth experiments. When phases f exp. I were examined separately, the difference in feed intake was evident nly during phase 3 (Table 2). A diet x phase interactin was significant. A similar trend was fund in exp. 2. Despite the increased feed intake, daily prtein intake by phase-fed hens during phases 2 and 3 was lwer (P<0.01) than that f cntrl hens, as was planned. fficiency f prtein utilizatin fr egg prductin was crrespndingly imprved, grams f prtein per kilgram egg and grams f prtein per egg being lwer (P<0.01) fr phase-fed hens than fr cntrl hens fr phases 2 and 3 f bth experiments. Dietary treatment had n significant (P >0.05) effect n feed efficiency as determined by grams f feed per gram egg r grams f feed per egg, (Table 2) except during phase 2 f exp. 2. ln this perid, grams feed cnsumed per gram egg prduced was greater fr phased-fed than fr cntrl hens. This difference was cnfirmed by a significant diet x phase interactin. There was n significant (P>0.05) difference in egg weight due t the main effect f diet (Table 3). Hwever, there was a significant interactin between diet and strain in exp. 1. gg weight was significantly greater fr phase-fed cmpared with cntrl diet hens f strains 4 and 8 but significantly lwer fr strains 4 and 7 given this treatment (Table 4). Analysis f egg grades indicated a different distributin amng grades in exp. 2 nly. Phasefed hens had a significantly higher percentage medium and significantly lwer percentage extra large eggs than cntrl hens (Table 5). data were available amng strains fr percentage f eggs with size grades. Haugh units were increased (P<0.05) by phase-feeding but there was n change in incidence f bld spts (Table 3). Shell quality as measured by SG appeared t be lwer fr phase-fed hens in exp. l Hwever, this difference was small and was significant (P<0.01) nly fr the egg test ar 339 days f age. A diet x phase interactin was significant. difference in shell quality was evident (P>0.05) frm limited data n incidence f cracked r sft-shelled eggs fr any phase f exp. I (Table 6). In cntrast t shell quality results f the first experiment, there was n significant difference in egg SG due t diet in exp. 2. Hwever, pultry-huse recrds indicate a lwer incidence f visibly cracked eggs fr phasefed hens than fr cntrl diet hens. A significant diet x phase interactin indicates that this difference ccurred during phase 3 nly. xcept as nted belw, dietary treatment had n significant effect n mean bdy weight at any age r n mrtality in either experiment ttable 6t. The main effects f diet and diet x phase interactins are given abve. r sme traits, fr which data fr individual strains are available, ne r tw strarns respnded t the phase-feeding regimen differently frm ali ther strains and demnstrated significant effects f diet n that trait. In exp. I such a diet x strain interactin was evident fr egg weight. As described abve in exp. 2 (Table 4), significant diet x strain interactins were identified fr egg specific gravity and bdy weight. ln additin, Duncan's test indicated highly significant differences in egg prductin due t diet. Cmpared with cntrl hens, pens f strain 5 given the phase-feeding diet prduced eggs f lwer (P<0.01) specific gravity ( vs ) and strain t hens had higher (P<0.01) hen-day percentage egg prductin (74.8 vs.72.87), whereas strain 7 phase-fed hens had lwer (P<0.05) egg prductin (63.4 vs. 65.4Vc). Bdy weight

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6 892 CAADIA JOURAL O AIMAL SCIC q O,rn --9 A -/i-y - Table 4. ffect f feeding prcedure n egg weight (g) fr nine strains f White Leghrn hens (exp. 1) Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. il J 5 d d,s) rrl 9. s a p 6 + n ::8R:: nh d +6 O 6ii \O\O rr an 6i6i tr :-. rr * +O d t r;-; eq d == -. : I 3 x -O --Y n r- <' dd 9l ici O rn n c ;ri nf ci hn == :- n - 6@ f i mn =X. Q. L). (JO. e2 r> aa + l- Strain I Mean SM+ Cntrl diet 'I ',7't r s r Phase Significancet feeding f difference S S S S S is - P>0.05; x : P<0.05; ** P<0.01. istandard errr f the mean. S f hens f strain 3 was higher (P<0.01) (1.84 vs kg), whereas bdy weight f strain 7 hens was lwer (P<0.01) (1.77 vs kg), relative t thse f cntrl hens, when subjected t the phase-feeding regimen. r ther strains, diet had n significant effect n these three traits. DISCUSSIO In bth experiments, adptin f the phasefeed regimen had n majr effect n quantity r quality f eggs prduced, but permitted substantial imprvement in efficiency f prtein utilizatin. An effect f diet n egg prductin was nted in exp. 2. r nly ne f nine strains tested, egg prductin was decreased (by 2V). xcept in the case f strain 5, these results (Tables 2, 3, 4) agree with thse f Deatn and Quisenberry (1965), ernandez et al. (1913), Sznv (1974) and Hamiltn (1978), but disagree with thse f Sharpe et al. (1965) and isher and Mrris (196'7) wh fund that reducing dietary prtein level caused a decrease in egg prductin. isher and Mrris (1967) bserved that when hens were prvided with a prtein intake knwn t supprt a given yield f egg mass in 33-wk-ld pullets the ratin was nt able t supprt the same yield f egg mass in 47-wk-ld hens. The authrs cncluded that the apparent efficiency f

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8 894 CAADIA JOURAL O A\I\,IAt- SCIC Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. utilizatin f ingested prtein was lwer in ld birds and stated that prtein requirements fr hens during the perid f declining utput shuld nt be estimated frm respnses bserved in yunger birds. Pilbrw and Mrris (1914) inferred a decline in net efficiency f lysine utilizatin fr egg prductin frm the bservatin f a prgressive displacement in curves representing respnse f daily egg mass t daily lysine intake, as hens aged. Based n their data, they recmmend that lysine level shuld nt be decreased in the diet f lder hens. The age-related respnse f egg yield t lysine intake has been cnfirmed (McDnald 1979) with ne imprtant difference. The regressin f rate f egg prductin n dietary lysine cntent was linear as pltted fr each mnth but the regressin cefficient decreased frm the third mnth f lay and lysine level did nt significantly affect rate f lay after the fifth mnth. Assuming that the nutritinal values f the diets were limited by lysine cntent, accrding t the design f the experiment reprted by McDnald (1919), it can be inferred that the lder hen is unable t respnd t high levels f lysine fr reasns that are independent f efficiency f lysine utilizatin. An actin cnsistent with this interpretatin wuld be t reduce the lysine and prtein levels f the laying diet fbr the perid f declining egg utput. An apprpriate reductin wili avid wastage thrugh prvisin f prtein at levels higher than that t which the lder hen can respnd, but it wuld make allwance fr a reduced efficiency f prtein utilizatin within the range f prtein levles t which it can respnd. This interpretatin f experiments with lder hens is supprted by results f the present experiment in which prtein level was reduced frm 15.5 t withut decrease in utput f eggs. eed intake per bird day appeared t be higher fr exp. 1 than fr exp. 2, except during phase 3 and grams feed per egg ancl grams prteln per egg were crrespndingly lwer. This may be due t the lwer temperatures experienced during exp. l, in , cmpared with thse f the secnd experiment 1n 19'79, althugh the summer perid (phase 2) fr bth years wuld be cnsidered as cl fr Ontari. The mean daily temperatures fr the three phases in each experiment were 14.0 and 15.8"C, 21.2 and 22.1'C, and 15.7 and 15.6"C, respectively, there being nly 7 and 9 wk fr which the average f mean daily temperatures in the pultry huse was abve 24'C. The increase in feed intake bserved fr phase-fed hens cmpared with cntrl hens agrees with the reprts f Aitken et al. (1973) and ivas and Sunde (1969) that an increase in feed cnsumptin ccurred when dietary prtein level was decreased. Sharpe et al. (1965) and isher and Mrris (1961), hwever, reprted a decrease in feed and prtein intake fbllwing a marked reductin f the prtein level f the diet frm 14.7 t l0.l% and frm l6 t 12Vc. A discrepancy between exps. 1 and 2 in the effects f diet n feed intake per gram egg appears t be due nly t the ccurrence f lwer variability within exp. 2 fr this trait. The difference between mean values fr diets 1 and 2 is the same fr bth experiments. The results f exp. 2 agree with thse f Hamiltn (1978) in which level f dietary prtein had a significant effect n gram feed per gram egg. The effect f the phase-feeding regimen n reducing grams f prtein per egg and per gram egg was substantial, cnsistent and is regarded as the majr advantage f phase-feeding. r exps. I and 2 the prtein savings btained during phases 2 and 3 average l4l and 128 g per hen, r apprximately 47c f the prtein used during the entire laying perid. The significant effects f diet n egg size and quality were neither large nr cnsistent between phases and experiments and in sme instances were l:imited t nly ne r tw f the strains tested. The in-

9 Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. fluence f diet n egg size was nt expressed in the same manner in bth experiments. Data analysis fr exp. I indicated that egg weight was decreased by diet fr tw strains, 4 and 7, and increased fr strain 5. Only a minr change in grade distributin was fund fr exp. 2. Tkadev et al. (1973), Hamilrn (1978) and Richter (1978) reprted n adverse effect n egg weight f reducing dietary prtein after wk f age, whereas reductins in egg weight were fund when prtein level was reduced at earlier ages frm 33 t 36 wk (Cligad and Quisenberry 1961; Sharpe et al. 1965; isher and Mrris 1967) and when the final dietary prtein level was very lw (Sharpe et al. 1965; Rlands 1980a). Shell quality was beneficially affected by phase-feeding in exp. 2 nly. A decrease in incidence f visibly cracked eggs ccurred in phase 3, when shell quality is mst critical because f large egg size in this perid. The decrease was assciated with a slightly lwer egg weight, apparent frm egg grades. This benefit in shell quality was btained despite the existence f a lwer egg SG fr strain 5. In exp. 1, lw egg SG was bserved fr phase-fed hens (particularly strains 1, 5 and 7); hwever, this difference ccurred nly early in phase 2. There was n evidence that this affected incidence f visibly cracked eggs. An imprvement in shell quality btained with a phase-feeding regimen was nt previusly reprted. Shell thickness (Deatn and Quisenbeny 1965), egg SG (Hamiltn 1978) and egg breaking strengrh (Richter 1978) were nt fund t be increased by phase-feeding. Rlands (1980b) fund that when the rate f increase f egg size was limited in yung hens by a lw (17.56/a) dietary prtein level, egg SG increased rather than decreased with age. The authr was unable t demnstrate a cnsistent imprvement in egg SG when prtein level was reduced frm 17 t in the diet f lder hens (Rlands 1980a). PHAs-DTG HS 895 An imprvement in interir egg quality was bserved in bth experiments as an increased Haugh unit value fr eggs frm phase-fed hens. This agrees with reprts f Deatn and Quisenberry (1965) and Aitken et al. (19'73) wh fund that interir quality imprved when prtein level was decreased; Hamiltn (1918) fund that the imprvement was nt statistically significant. The magnitude f the difference bserved was lwer than that reprted by the frmer authrs, the increase f nly 0.3% Haugh unit value has limited practical significance. r sme traits, significant diet x strain interactins were bserved and individual strains culd be identified which respnded differently t the tw diets. Certain strains were invlved in these interactins, ntably the unselected strains 5 and 7. There was a tendency fr these unselected strains t respnd adversely t the phase-feeding diet cmpared with the cntrl diet, whereas selected strains respnded in a favrable manner t the phase-feeding diet r shwed n difference frm the cntrl diet. An example supprting this generalizatin is given by the decrease in egg weight n phase-feeding fr strain 7 hens cmpared with the increase fund fr selected strain 8 hens (Table 4). Signilicant prtein level x strain interactins fr egg prductin, egg weight, bdy weight r SG were reprted by Liljedahl et al. (1973), Christmas et al. (1919), and Aitken et al. (1973) wh cmmented that such interactins were e\ceptins, nt the rule. Sharpe et al. (1965) fbund a prtein level x breed interactin fr egg prductin and bdy weight in a phase-feeding study. It is apparent that selected strains are mre able t adjust prductively t nutritinally marginal diets than strains representing breeding standards f 1950 r When data fr unselected strains are mitted, few adverse effects n phasefeeding are evident. Sme general ecnmic cnclusins may

10 CAADIA JOUR\AL O AIIAL SCICL Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. be reached frm the results. At 1981 prices, the csts per tnne f diets 1, 2 and 3 were $225, $220 and $217, respectively. The amunts f each diet eaten in exps. 7 and 2 can be calculated frm feed intake data in Table 2, and the feed csts fr the experimentai perids can then be calculated as shwn in Table 7. It will be seen that the phase-feeding treatment f bth experiments resulted in an verall feed cst saving f sme l1q per bird, r apprximately 1.3V f the feed cst fr the experimental perid. Slight variatins in percent hen-hused prductin and egg gradings affected the dllar values f eggs sld per hen in the tw experiments, but the results were cnflicting (see Table 7). In exp. 1, phasefeeding resulted in 9l wrth greater egg sales per bird, based n ebruary 1981 prices. This cntrasted with 8d wrth less in egg sales frm exp. 2. Table 7. The ecnmics f hase feedins eed csts xp. I xp. 2 Avg gg sales xp. I xp. 2 AVg Avg cracked-egg csrs - Cntrl Phase-fed r'q l4 Plr urru/ The incidence f cracked eggs was reduced under phase-feeding as cmpared with the cntrl treatments. The saving was nt great, hwever, being abut 1l per bird. Other differences had minr ecnmic impact, with the result that verall average savings frm exps. 1 and 2 wuld amunt I 12.5Q per bird, r $1250 fr a flck f birds. The cst f feed during the experimental perid des nt f curse cver all csts f prductin ver the life f the bird. If these were t be estimated at $17.50 then the saving wuld represent 0.JV f the cst f prductin. It is cncluded that a phase-feeding prcedure in which dietary prtein level is reduced l a mderate degree at 273 and again 384 r 420 days f age can be used fr winter-hused SCWL hens withut adverse effect n egg prductin and with ptentially beneficial effect n net incme. Benefits in prtein prductivity and egg quality were als btained frm this prcedure. The wide genetic base f the experiment suggests that the cnclusins are bradly applicable t SCWL flcks in Canada and the nrthern United States. ACKOWLDGMTS The assistance f H. Mucha in perfbrming prgramming fr data prcessing and f Dr. S. C. Thmpsn in cnducting ecnmic assessment f treatment effects is appreciated. We are als indebted t Dr. R. S. Gwe fr all the individual bird data cllected in his selectin study and used here AITK, J. R., DICKRSO, G. R. and GOW, R. S ffect f intake and surce f prtein n laying perfrmance f seven strains under single and duble cage husing. Pult. Sci. 52: ASSOCIATIO O OICIAL AGRICUL- TURAL CHMISTS Official methds f analysis. llth ed. AOAC, Washingtn, DC. CHRISTMAS, R. B,, DOUGLAS, C, R., KALCH, I. W. and HARMS, R. H Perfbrmance f twelve strains f laying hens either phase fed r straight fed prtein fr a twelve mnth perid. Pult. Sci. 58: 1011 (Abstr. ). COLIGADO,. C. and QUISBRRY, J. H ffects f prtein level, surce and change f level during the laying perid n perfbrmance f incrss egg prductin stck. Pult. Sci. 40: 1388 (Abstr.). DATO, J. W. and QUISBRRY, J. H ffects f dietary prtein level n perfrmance f fwl cmmercial egg prductin stcks. Pult. Sci. 44: 93G942. RADZ, R.,.SALMA, A. J. Ad McGIIS, J. 19'73. ffect f feeding different prtein levels and f changing prtein leve1 n egg prductin. Pult. Sci. 52: ISHR, C. and MORRIS, T. R Sme

11 CAV AD HAMII,TO - PHAS-DIG O HS 89',7 Can. J. Anim. Sci. Dwnladed frm by n 12/21/17 r persnal use nly. effects f changing prtein levefs during the pullet laying year. Br. Pult. Sci. 8: GOW, R. S. and AIRULL, R. W Perfrmance f six lng-term multi-trait selected Leghrn strains and three cntrl strains and a strain crss evaiuatin f the selected strains. Prc S. Pacific Pultry Sci. Cnv. pp HAMILTO, R. M. c The effects f dietary prtein level n prductive perfrmance and egg quality f fur strains f White Leghrn hens. Pult. Sci. 57: LI, J. C. R Statistical inference. II. The multiple regressin and its ramificatins. dward Brs. Inc., Ann Arbr, Mich. LILJDAHL, L. 8., WILHLMSO, M. and CARLGR, A. B Gentype-nutritin interactins in White Leghrn strains. Acta Agric. Scand McDOALD, M. W Lysine cntent f the diet and the laying cycle - prductin and prfit. Prc. 3rd Austr. Pultry Stckfeed Cnv. pp. 8G90. ATIOAL ACADMY O SCICS - ATIOAL RSARCH COUCIL utrient requirements f dmestic animals. 1. utrient requirements f pultry. 7th ed. Washingtn, D.C. IVAS, S. C. and SUD, M. L Prtein requirements f layers per day and phase feeding. Pult. Sci. 48: 16' PILBROW, P. J. and MORRIS, T. R Cmparisn f lysine requirements amngst eight stcks f laying fwl. Br. Pult. Sci. 15: RICHTR, G Zweiphasenfiitterung der Legehybriden. Tierzucht. 32: ROLADS, D. A. 1980a. gg shell quality. I. ffect f dietary manipulatins f prtein, amin acids, energy, and calcium in aged hens n egg weight, shell weight, shell quality and egg prductin. Pult. Sci. 59: 203V2046. ROLADS, D. A. 1980b. gg shell quality. II. ffect f dietary manipulatins f prtein, amin acids, energy and calcium in yung hens n egg weight, shell weight, shell quality and egg prductin. Pult. Sci. 59: SHARP,., MORRIS, T. R. and OX, S Changes in dietary prtein level during the pullet year. Br. Pult. Sci. 6: SOZOOV, A. A Requirements f egg layers fr sme nutrients, depending n light regime. Prc. XV Wrld's Pultry Cngr. pp. 43V431. STL, R. G. D. and TORRI, J. H Principles and prcedures f statistics. McGraw- Hill Bk C. Inc., Trnt. TKACV, I.., CHOCHLOV, A. M. and AZAROV,. J Requirements f breeding hens fr prtein and amin acids during phase feeding. Bil. Chem. YyLivy Zviiat. 9: 29T301.