ELBA BI OFLUX
Ex t r e m e Lif e , Biospe olog y & Ast r obiolog y
I n t e r n a t ion a l Jou r n a l of t h e Biof lu x Socie t y
I n t e r a ct ion of br e e ds, ye a r s, a ge of bir d a n d pe n
e ffe ct s on h e n da y la y of t h r e e la y e r br e e ds a n d
t h e ir a d a pt a t ion in t h e de r ive d Sou t h e r n Gu in e a
Sa v a n n a h of N ige r ia
Deeve S. Gwaza, Terzungwe Ahem en, and J. Ochoche Egahi
Depar t m ent of Anim al Br eeding and Phy siology , Univ er sit y of Agr icult ur e Mak ur di, Nigeria. Cor r esponding aut hor : D. S. Gw aza, Gw azadeeve@y ahoo. com
Abst r a ct . Egg pr oduct ion of Haco black , Shav er ’s br own, Lohm an br own and Oly m pia black wer e collect ed fr om pr oduct ion r ecor ds at Big Bam com m er cial farm Mak ur di fr om 1 997 t o 20 04. The m ean hen day lay of t he br eeds wer e est im at ed in per cent ages at 49- 52, 56- 60 and 6 9- 73 week s. The m ean hen day lay of effect s of br eed by y ear and br eed by pen by age of bir d int er act ions wer e est im at ed. The hen day lay of Haco black by y ear int er act ion wer e low v ar ied significant ly ( P<0. 05) acr oss t he y ear s; while t hat of Sh av er s br own wer e significant ly higher and consist ent . Oly m pia black and Lohm an br own hen day lay due t o int er act ion wit h y ear wer e also high wit h m inim um v ar iat ion acr oss t he y ears. The m ean hen day lay due t o effect s of int er act ion of Haco black at 56- 60 and 69- 73 week s by pen L1,
L2, and L3, wer e significant ly lower t han t hat at 49- 56 week s. The m ean hen day lay due t o ef fect s of
int er act ion of Shav er s br own at 56- 60 and 6 9- 73 week s by pen L1, L2, and L3, wer e significant ly higher
t han t hat at 49- 56 week s. The m ean hen day lay of int er act ion of Lohm an br ow n and Oly m pia black at 69- 73 week s by Pen L1, L2, and L3, wer e significant ly higher t han t hat at 56- 60 week s. This r esult
indicat ed t hat t he r esponse t o t he r est r ict ions of t he y ear s and t heir effect s on t he st r at egies of aging of t he br eeds on t heir hen lay v ar ied acr oss t he genet ic gr oups. Haco black was m or e suscept ible t o t his st r ess especially at t he adv anced age. Lohm an br own and Oly m pia black wer e bet t er t han Haco black . Shav er ’s br own was super ior in t his t r ait as neit her t he r est r ict ions of t he y ear s n or t he st r at egies of aging affect ed it s hen day lay . I n or der of fit ness, Shav er s br own, Lohm an br own and Oly m pia black wer e m ost adapt ed t o t his r egion. Thus, Shav er s br own which is bet t er adapt ed t o t he pr ev ailing env ir onm ent al condit ions in t he Sout her n Guinea Sav an nah is r ecom m ended f or poult r y far m er s in t his localit y .
Ke y W or ds: cage- posit ion, hen- day lay , int er act ion, Guinea Sav annah.
I n t r odu ct ion. The per for m ance of a lay er br eed is t he j oint act ion of it s genot y pe and
env ir onm ent al t oler ance of com m on br eeds t hat can t oler at e pioneer ing envir onm ent al condit ions in t heir localit ies. The st udy t her efor e int ends t o pr ovide com par at iv e infor m at ion on t he effect of br eed by y ear and br eed by age of bird by pen int er act ion on hen day lay of t he br eeds.
M a t e r ia ls a n d M e t h ods. Dat a for t his st udy w er e collect ed fr om Big Bam com m ercial
poult r y far m on egg pr oduct ion of Haco black, Shav er s br ow n, Lohm an br ow n and Oly m pia black lay er br eeds fr om 1997 t o 2 00 4.
Loca t ion . Big Bam com m er cial far m is sit uat ed at Mak ur di Benue St at e, in t he
der iv ed sout her n Guinea Sav annah r egion of Niger ia. Mak ur di is locat ed bet w een Lat it ude 6º 29̋, 8º 7̋ Nor t h and Longit ude 7º 44̋ and 9º 5 5̋ East . The clim at e is char act erized by t r opical w eat her condit ions com prising of low alt it ude, low r ainfall and m oder at e hum idit y at v ar ying t im es of t he y ear. Ther e ar e t w o seasons, dr y ( Nov em ber t o April) and w et ( May t o Oct ober ) . Mak ur di has an av er age r ainfall t hat r anges fr om 800 t o 1, 500m m . The annual av er age t em per at ur e r anges fr om 2 1º C t o 33º C and t he av er age hum idit y also r anges fr om 45% t o 6 8 per cent .
Flock M a n a ge m e n t. The chick s wer e acquir ed at day - old and br ooded on t he
far m . They w er e m aint ained on hom e m ix chick m ash for m ulat ed fr om soy a bean cak e, m aize, r ice br an, bone m eal, salt and vit am in m iner al pr em ix , w at er w as supplied ad-libit um for t he fir st fiv e w eek s. Medicat ion and v accinat ion schedules w er e car efully follow ed dur ing br ooding and r ear ing. At eight w eek s, t he hom e m ix chick m ash w as r eplaced wit h hom e m ix gr ow er m ash cont aining 16 per cent cr ude pr ot ein and 4. 07 Kcal/ g m et abolisable ener gy using t he sam e init ial ingr edient s. The bir ds w er e m aint ained on t his diet unt il t hey w er e ninet een w eek s of age. At t w ent y w eek s, t he bir ds w er e t r ansfor m ed t o t he cages in t he laying pens. The hom e m ix gr ow er s m ash w as r eplaced wit h hom e m ix lay er s m ash cont aining 56. 27% nit r ogen fr ee ex t r act , 90. 95% ash, 3. 98% cr ude fibr e and 4. 08% fat s also form ulat ed fr om t he init ial ingr edient s and fed at 0. 12 5k g per day . Wat er w as supplied ad-libit um t hr oughout t he lay ing phase. Feed w as ser v ed t wice a day at 5 hour s GMT ( 6 am local t im e) and at 14 hour s GMT ( 3. 00 pm local t im e) . Eggs w er e collect ed in t he m or ning 7. 00 h our s GMT ( 8. 00am local t im e) and at ev ening 15 hour s GMT ( 4. 00 pm local t im e) .
H ou sin g. The flock w er e housed in t hr ee pens designat ed as L1 ( pen I ) , L2 ( pen
I I ) and L3 ( pen I I I ) . All t he pens w er e built fr om cem ent block and w er e m ade of dw ar f
w all scr eened wit h wir e m esh and zinc r oof, t he or ient at ion w as east t o west . The dist ance bet w een t he pens w as about 70m . The floor lev el v aried fr om L1 t o L3. I n pen L1,
t he floor lev el w as elev at ed such t hat y ou clim b up int o t he pen; t he floor lev el window m ar gin w as low. Ther e w er e t w o cages one each at eit her sides of t he pen designat ed as L1C1 ( cage I ) and L1C2 ( cage I I ) int o w hich t he bir ds w er e r ear ed. The floor lev el r oof
m ar gin w as low . I n pen L2, The floor lev el w as sunk dow n; such t hat y ou w ould hav e t o
descend dow n int o t he pen. The floor level window m ar gin w as high. Ther e w er e t hr ee cages. Cage I ( L2C1) follow ed by cage I I ( L2C2) in t he m iddle and cage I I I ( L2C3) at t he
opposing side. The floor lev el r oof m ar gin w as very high. I n pen L3, t he floor lev el w as at
gr ound lev el. I t s floor lev el window m ar gin w as low . I t also lies close t o t he open riv er Benue. Pen L3 also cont ain t hr ee cages. Cage I ( L3C1) , Cage I I ( L3C2) m iddle cage and
Cage I I I ( L3C3) .
D a t a An a ly sis. The hen- day lay of t he br eeds w as est im at ed in per cent age
( num ber of eggs collect ed divided by num ber of bir ds housed m ult iplied by 100) at 4 9-52, 56- 6 0 and 69- 73 w eek s. Mean hen- day lay of effect s of br eed by y ear and br eed by pen by age of bir d int er act ions and t heir st andar d er r or of m eans ( SE) w er e also est im at ed using t he m odels below. Duncan’s m ult iple Range Test w as used t o separ at e m eans of effect s t hat w er e significant .
Yij k = µ + Bi + eij
Yij k = µ + Bi + ( By )ij + eij k
Yij kl = µ + Bi + ( BPA)j k l + eij kl
Wher e:
Yij kl = obser v ed hen day lay
Bi = effect of br eed ( i= 1, 2, 3, 4)
eij kl = er r or assum ed nor m ally and independent ly dist ribut ed wit h m ean zer o and
v ar iance t hat of t he populat ion.
( By )ij = effect of int er act ion bet ween br eed by year .
( BPA)j kl = effect of int er act ion bet w een br eed by ben by age of bir d.
Re su lt a n d Discu ssion
Br e e ds by Ye a r s I n t e r a ct ion Effe ct s. Ther e w her e significant ( p<0. 05) effect of br eed by y ear int er act ion on hen hen- day lay of t he br eeds. I n 199 7, 199 8 and 19 99, Haco black hen day due t o br eed by y ear int er act ion w er e least and significant ly ( P<0. 05) differ ent fr om t hat of t he ot her br eeds ( Table 1) . Shav er s br ow n and Oly m pia black hen-day lay due t o br eed by year effect s in 1997, 19 98, 19 99 and 200 3 w er e not significant ( P˃0. 05) . The effect of y ear by br eed int er act ion on hen- day lay of Shav er s br ow n and Lohm an br ow n in 19 98 and 1 999 w er e also not significant ( P˃0. 05) . Oly m pia black and Lohm an br ow n hen- day lay in 1999, 2000 and 2 004 w er e also not significant ( P<0. 05) ( Table 1) . The highest hen- day lay due t o t his effect w er e r ecor ded in 2001 and 200 2, ( 77. 6 and 73. 2 per cent ) f or Haco black and Lohm an br ow n in 20 01 r espect iv ely and ( 76. 7 and 6 9. 0) per cent in 2002 for Oly m pia black and Lohm an br ow n r espect iv ely ( Table 1) . An incr ease in t em per at ur e t hat affect ed Lohm an br ow n and Haco black r esult ing t o a decr ease in t heir hen- day lay, did not affect t hat of Oly m pia black and Shav er s br ow n.
Table 1 Br eeds and y ear s int er act ion effect on hen day lay of Haco black ,
Oly m pia black , Shav er s br ow n and Lohm an br ow n at 50- 5 5 w eek s old
Year Breed
1997 1998 1999 2000 2001 2002 2003 2004
HB 52.3a±
0.01 ( 2136)
49.6a±
0.03 ( 1981)
52.6a±
0.02 ( 2356)
58.5a±
0.03 ( 1628)
77.6a±
0.02 ( 1782)
58.2a±
0.03 ( 1354)
64.4a±
0.01 ( 1900)
61.75a
± 0.02 ( 1249)
SB 62.3b±
0.00 ( 3224)
66.22b±
0.02 ( 1281)
63.42b±
0.02 ( 1318)
60.45a±
0.00 ( 3080)
47.6b±
0.00 ( 6148)
57.02b
± 0.00 ( 6130)
56.0b±
0.00 ( 5132)
62.8a±
0.02 ( 1163)
OLPB 63.4b±
0.02 ( 1021)
76.3c±
0.05 ( 936)
65.4b±
0.03 ( 1110)
63.8b±
0.02 ( 1320)
68.4c±
0.02 ( 1348)
76.7b±
0.01 ( 2514)
55.8b±
0.01 ( 2632)
68.8b±
0.01 ( 2918)
LOHB 69.3c±
0.03 ( 1018)
64.5b±
0.02 ( 1239)
58.6b±
0.03 ( 1240)
68.6b±
0.04 ( 1129)
73.2b±
0.03 ( 1008)
69.0c±
0.03 ( 928)
63.2c±
0.02 ( 1126)
67.0b±
0.08 ( 1023)
a, b, c - Figur es wit h differ ent superscript s acr oss t he gr oups ar e significant ly differ ent . Figur es in par ent hesis ar e num ber s of obser v at ions.
The low est significant hen- day lay of Haco black by 199 7, 19 98 and 1 99 9 int er act ion m ay be r elat ed t o t he int er act ive effect s bet ween high t em per at ur e and r elat iv e hum idit y ( 27. 82º C, 52.6 7% , 29. 59º C, 50. 92% and 2 8. 14º C, 54. 75% ) r espect iv ely ( Mak ur di 2005) on egg pr oduct ion. This m ay be due t o t he inabilit y of Haco black t o cope w it h t her m al st r ess w hich depended on t he black insulat ion pr ov ided by t he bir d coat , r at e of feat her ing as w ell as it s behavior t o elim inat e ex cess body heat . Webst er & Wilson ( 199 2) and Leng ( 1 991 ) also r epor t ed t he effect of dom est ic anim als phy siological behav ior s in elim inat ing ex cess body heat on t heir pr oduct ion per for m ance.
The significant differ ence in t he hen- day lay due t o br eed by y ear int er act ion effect of Oly m pia black and Lohm an br ow n in 19 97 and 1 99 8 w as also under st andable because, t he incr ease in t em per at ur e fr om 27. 8 2 º C and r elat iv e hum idit y of 52. 67% t o 28. 39º C r elat iv e hum idit y of 50. 92% in 1 99 8 ( Mak ur di 2005) r educed hen- day lay of Lohm an br ow n fr om 69. 3 t o 6 4. 5 per cent w hile t hat of Oly m pia black incr eased fr om 63. 4 t o 76. 3 per cent . Thus Oly m pia black wit h super ior addit iv e and non addit iv e genet ic effect on t his t r ait is m or e able t o cope wit h t her m al st r ess t han Lohm an br ow n w hose inferior addit iv e and non addit iv e genet ic effect s on t his t r ait m ade it suscept ible t o t he incr ease in t em per at ur e. I t will t her efor e be heat st r essed, consum e less feed and hence a fall in t he egg pr oduct ion as observ ed. Johnson ( 198 7) and Leng ( 19 91) also r epor t ed significant effect of incr eased t em per at ur e on anim al’s abilit y t o r educe body heat and it s per for m ance.
The highest hen- day lay r ecor ded in 200 1 and 20 02 w er e due t o low hum idit y of 48. 83 and 4 7. 17 per cent ( Mak ur di 2005) r espect iv ely t hat enhanced body heat lost ev en at higher t em per at ur e by ev apor at ive cooling. The r educed hum idit y ex ploit ed fully t he genet ic pot ent ials of Haco black and Lohm an br ow n on t his t r ait . Lande & Shannon ( 199 6) also r epor t ed t hat im pr ov ed envir onm ent al condit ions ex ploit t he full pot ent ials of a br eed.
The significant higher hen- day lay of Shav er s br ow n and Oly m pia black ov er t hat of Haco black and Lohm an br ow n in 1998 ( 66. 8 ± 0. 01, 76. 3± 0. 00) 1 999 ( 63. 4 2 ± 0. 02, 65. 4 ± 0. 01) and 200 4 ( 62. 8 ± 0. 00, 68. 8 ± 0. 00) in t he sam e y ear s m ay be r elat ed t o t heir superior addit iv e and non addit iv e genet ic effect s t hat enhanced t heir abilit y t o cope wit h t her m al st r ess and t oler at ed t he incr ease in t em per at ur e ( Mak ur di 200 5) w it h m inim um r est rict ions on t heir genet ic pot ent ials in t his t r ait . Engst r om ( 199 2) , Rahm an ( 2 00 2) and Lande ( 19 92) also r epor t ed t hat t he pot ent ials of t he bet t er genot y pe is alw ay s ex pr essed ir r espect iv e of envir onm ent al r est rict ions.
The significant higher hen- day lay of Haco black and Lohm an br ow n in 20 03 ev en at 32. 53º C ( Mak ur di 2005) ov er t hat of Shav er s br ow n and Oly m pia black m ay be r elat ed t o t heir st ocking r at e and t he low hum idit y ( 46. 75% ) ( Mak ur di 20 05) w hich r ender s heat dissipat ion by ev apor at iv e cooling t hr ough pant ing v er y effect iv e. Far ooq et al ( 2002) , Aw oniy i et al ( 2003) also r epor t ed t hat low st ocking r at e at low hum idit y enhances ev apor at iv e cooling and im pr ov ed egg pr oduct ion. On t he ot her hand, t he low hen- day lay of Shav er s br ow n and Oly m pia black in 2003 m ay be due t o t he cum ulat iv e effect of high st ocking r at e and t he incr eased t em per at ur e, w hose int er play enhances heat build up and t her m al st r ess. Car ew et al ( 198 0) , Lai & Kan ( 2000) also r epor t ed significant effect of int er act ion bet w een high st ocking r at e, high t em per at ur e and hum idit y on hen- day lay of w hit e leghor n hens an d Tsainy a lay er duck s r espect ively .
Br e e d by Age by Pe n I n t e r a ct ion Effe ct s. Ther e w er e int er act ion effect s
bet w een t he br eed by age by pen condit ions on hen- day lay per for m ance. While Haco black t oler at ed pen L1, L2 and L3 condit ions at 48- 52 w eek s ( Table 2) . The sam e pen
condit ions r educed it s per for m ance significant ly ( P< 0. 05) at 56- 60 and 69 - 7 3 w eek s of age ( Table 2) . The hen day lay per for m ance due t o Oly m pia black by ages by pen int eract ion at 49- 52, 5 6- 6 0 and 69- 73 w eek s w er e how ev er not significant ( P> 0. 05) ex cept in pen L2 w her e hen day lay at 49- 52 w eek s differ ed significant ly fr om t hat of
ot her ages ( Table 2) . The hen- day lay of Shav er s br ow n by 56- 60 and 6 9- 7 3 w eek s int er act ions wer e highest and significant ly ( P< 0.05) differ ent from t hat at 49- 52 w eek s ( Table 2) . This sam e t r end w as also obser v ed for Lohm an br ow n by Age by Pen t hough at low er v alues.
The significant low er hen- day lay of Haco black due by age by pen effect at 56- 60 and at 69- 73 w eek s of age com par ed t o 48- 52 w eek s indicat ed t hat it addit ive genet ic effect s on t his t r ait decreases wit h age. Thus it s abilit y t o t oler at e envir onm ent al hindr ance w as gr eat ly r educed wit h adv ancing age. This result agr eed wit h t he r epor t of Ledur et al ( 200 3) . This also indicat ed t hat t he econom ic pr oduct ion lev el of Haco black is shor t - liv ed especially under har sh env ir onm ent al condit ions.
black and Lohm an br ow n hen- day lay due t o t he abov e effect s follow ed t he t r end obser v ed on Shav er s br ow n; t he v alues w er e how ev er low er t han t hat r ecor ded for Shav er s br ow . Ledur et al ( 2003) also r epor t ed t his observ at ion. This m ay be due t o v ar ied st r at egies of aging for each genet ic gr oup on t his t r ait . Shav er s br ow n t oler at ed t he int er act ive effect s wit hout appr eciable decline in egg pr oduct ion. I t pr oduces at econom ic lev el over longest period t han Lohm an br ow n and Oly m pia black under sam e st r essful condit ions.
Table 2
Br eed by age by pen int er act ion effect s on hen day lay per for m ance of t he br eeds
Age Breed
L1
Pen
L2 L3
Shavers brown
49- 5 2 “ 56. 0a± 02 ( 18 62) 60. 0a± . 09 ( 3 38 9) 62. 0a± 0. 12( 284 9)
56- 6 0 “ 74. 0b± 0. 1 2( 5 121 ) 68. 0b± 0. 0 2( 5 412 ) 57. 0a± 0. 01( 313 6)
69- 7 3 “ 78. 0b± 0. 0 1( 4 244 ) 68. 0b± 0. 0 3( 1 156 ) 74. 0b± 0. 0 0( 5 120 )
Lohm an brown
49- 5 2 “ 65. 0a± 0. 03( 2840) 55. 0b± 0. 0 1( 4 233 ) 58. 0a± 0. 01( 122 2)
56- 6 0 “ 54. 0b± 0. 2 1( 2 134 ) 53. 0b± 0. 1 2( 3 528 ) 57. 0b± 0. 1 0( 2 229 )
69- 7 3 “ 56. 8b± 0. 2 2( 1 948 ) 63. 0a± 0. 12( 211 4) 65. 0a± 0. 01( 223 1)
Olym pia black
49- 5 2 “ 57. 0a± 0. 02( 511 0) 63. 3a± 0. 01( 439 6) 60. 0a± 0. 00( 338 6)
56- 6 0 “ 60. 0a± 0. 12( 411 1) 54. 0b± 0. 0 1( 3 149 ) 57. 0a± 0. 00( 400 8)
69- 7 3 “ 63. 0a± 0. 04( 325 9) 53. 2b± 0. 0 1( 2 212 ) 59. 8a± 0. 03( 401 0)
Haco black
49- 5 2 “ 75. 0a± 0. 02( 313 70 ) 69. 0a± 0. 02( 314 8) 76. 0a± 0. 01( 144 5)
56- 6 0 “ 53. 0b± 0. 0 2( 3 122 ) 65. 0a± 0. 01( 244 0) 55. 0b± 0. 0 2( 1 681 )
69- 7 3 “ 48. 0b± 0. 0 1( 3 118 ) 43. 0b± 0. 0 2( 2 141 ) 45. 0c± 0. 03( 119 4)
a, b, c - Figur es wit h differ ent superscript s acr oss t he gr oups ar e significant ly differ ent ( P< 0. 05) . Figur es in par ent hesis ar e num ber s of obser v at ion.
Con clusion s. The int er act ion bet w een t he br eed by y ear and br eed by pen by age of
bir ds affect ed t heir egg laying pot ent ials at v aried m agnit ude. Haco black becom es highly suscept ible t o envir onm ent al st r ess as it adv ances in age wit h a shar p decline in egg pr oduct ion. This w as also t r ue for Lohm an br ow n t hough at low m agnit ude. An incr ease in envir onm ent al t em per at ur e t hat r est r ict ed t he full ex ploit at ion of t he genet ic pot ent ials of Haco black and Lohm an br ow n on t his t r ait did not r est r ict sam e in Shav er s br ow n and Oly m pia black . A poor ly designed pen aggr av at ed t he exist ing envir onm ent al st r ess w hich fur t her r est rict ed t he bir ds pot ent ials on hen day lay.
Re com m e n da t ion s. A w ell designed pen t hat enhances m axim al v ent ilat ion is a
pr er equisit e t o m axim al pr oduct ivit y of t he layer indust r y. Any of t hese four br eeds has t he pot ent ial for egg pr oduct ion. The m ost favour ed in or der of fit ness ar e Shav er ’s br ow n, Oly m pia black, Lohm an br ow n and Haco b lack. I f a lay ing flock of Haco black and Oly m pia black m ust be r ear ed in t he r egion, t he st ocking densit y m ust be low and ex t r a m anagem ent t echniques t o r educe heat build up and enhance feed int ak e m ust be encour aged.
N ot e . Ther e w as no conflict of int er est in t he pr esent r esear ch. The aut hor s ar e not
im por t ant client s or em ployees of t he anim al pr oducer com panies.
Re fe r e n ce s
Aw oniyi T. A. M. , 2003 The effect of housing on lay er- chick en’s pr oduct ivit y in a t hr ee-t ier cage. I nee-t er naee-t ional Jour nal of Poulee-t r y Science 2 ( 6) : 43 8- 4 41.
Car ew L. B. , Foss D. C. , Bee D. E. , 1980 Diet ar y ener gy concent r at ion effect on per for m ance of w hit e Leghor n hens at v ar ious densit ies in cages. Poult Sci
5 9 : 1 09 0- 1 09 8.
Dafw ag I . I . , 198 7 Hot w eat her and it s effect s on p oult r y under Nigerian condit ions. Nigerian Liv est ock Far m er 7( no. 1- 4) : 10- 12.
Engst r om 199 2 Egg pr oduct ion per for m ance of com m er cial laying hens in Chak w al dist rict . Pakist an Liv est ock Resear ch for Rur al Developm ent 1 4 ( 2) .
Gillespie J. A, Tur elli M. , 1989 Genot y pe and envir onm ent al I nt er act ions and t he m aint enance of poly genic v ariat ion. Genet ics 1 2 1 : 112 9- 1 38.
Johnson H. D. , 1987 Bio clim at e and liv est ock in Bio clim at ology and t he adapt at ion of livest ock. World Anim al Science B5. pp. 3- 6 [ H. D. Johnson ed. ] . Am st er dam , Elser vier .
Lai M. K. , Kan C. C., 2000 Effect of cage floor ar ea and populat ion size on t he laying per for m ance of t he br ow n Tsaiy a laying duck s. Jour nal of Taiw an Liv est ock Resear ch 3 3 ( 3) : 28 1- 2 91.
Lande R. , 1988 Genet ics and dem ogr aphy in biological conser v at ion. Science 2 4 1 : 145 5-146 0.
Lande R. , Shannon S. , 1996 The r ole of genet ic var iat ion in adapt at ion and populat ion in a changing env ir onm ent . Ev olut ion 5 0 ( 1) : 43 2- 4 3 7.
Ledur M. C. , Faifully R. W. , McMillan I . , Gow e R. S. , Asselt ine L. , 200 0 Genet ic effect of aging on fer t ilit y and hat chabilit y in t he fir st laying cir cle of t hr ee w hit e Leghor n st r ains and t heir t w o w ay- Gossses. Br Poult Sci 4 1 : 55 2- 5 61.
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Receiv ed: 18 June 2 011. Accept ed: 12 Sept em ber 201 1. Published online: 1 5 Sept em ber 201 1. Aut hor s:
Deev e Sebast ian Gwaza, Depar t m ent of Anim al Br eeding and Phy siology , Univ er sit y of Agr icult ur e, P. M. B 2373, Mak ur di, Niger ia, e- m ail: Gwazadeev e@y ahoo. com
Ter zungwe Ahem en, Depar t m ent of Anim al Br eeding and Phy siology , Univ er sit y of Agr icult ur e, P. M. B 2373, Mak ur di, Niger ia.
Joseph Ochoche Egahi, Depar t m ent of Anim al Br eeding and Ph y siology , Univ er sit y of Agr icult ur e, P. M. B 2373, Mak ur di, Niger ia, e- m ail: egahij oseph@y ahoo. com
How t o cit e t his ar t icle:
Gwaza D. S. , Ahem en T. , Egahi J. O. , 2011 I nt er act ion of br eeds, y ear s, age of bir d and pen ef fect s on hen day lay of t hr ee lay er br eeds and t heir adapt at ion in t he der iv ed Sout her n Guinea Sav an nah of Niger ia. ELBA Bioflux
