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Effects of supplementary feeding and suckling intensity on postpartum reproductive performance of small East African Zebu cows
Theriogenology
38:97-106,
1992
AsageTegegne,1r2,K.W. Entwistle2and E. Mukasa-Mugemal 1InternationalLivestockCentre for Africa(ILGA) P.O.Box 5689, Addis Ababa, Ethiopia 2craduateSchoolofTropicalVeterinaryScienceandAgriculture James CookUniversity,TownsvilleQld 4811, Australia Received for publication:September 6, 1991 Accepted:ApriL 25, 1992
Small EastAfricanZebucows(n=120)whichcalvedduringthed_ryseason wereusedtodetermine theeffectsofpostpartusnutritionalsupplementation and suckling intensityon bcdy weight,body conditionscore, reproductive perfc~~~andoncalfmortalityandpreweaninggrowthperformance. Cows were allocated based on calving bcdy weight to either receive a supplementaryfeed of molasses blocks containing10% urea or to serve as con~-olsandtobegrazedonly.Withinnutritio~lgroups, axswerefurther assigm3d either to continuoussuckling or to restrictedsuckling twice daily. Intactbullswereintroduced21daysafterthefirstcawhadcdlved, anddatawerecollected for8 nmths. Calvingbodyweightandbodycondition score of dams ranged from 186 to 192 kg and from 3.8 to 4.2 and did not differ amng the treatment groups. Supplemantaryfeedingsignificantly (p
Key wo?zds:Zebu cow, postpartum,reprcduction,nutrition,suckling INTROMJC!I'ION Postpartum anestms and low fertilityare the major causes of poor reproductiveperformance in cattle in tropical regions (1, 2). Factors influencing postpartum reproductive perforsance have been reviewed previously (3 - 6). Grazing cows calving durirq the dry season are often faced with inadequatenutrition (7, 8) while their nutrient demand for tissue repair and lactationare high. Lactatingems establishtheir Acknowledgements TheauthorsthanktheEthiopianMinistryofAgricultureforaccesstothe facilitiesandanimals,Mr. KassahunZewdiefortechnicalassistance,and Mr. Solcmmn Zewdie andMr. G. De'ath for advice on statisticalanalyses.
Copyright
0
1992
Butterworth-Heinemann
98
Theriogenology
priorities in nutrient utilization (9), and during periods of severe undernutritionsurvival of the cow and the calf become primary issues. Resumptionof ovarianactivityoftendoes not commence untilafterthe calf is weaned, and there are strong interactingeffects of nutrition and suckling (5). Rothbodyweightandbcdycondition (10)aswellas andthe rates of body wei~tand~conditionchangesduringthepostpartumperiodinfluenCethe anestrus interval and subseguent fertility (11). However, precalvirq nutritionallevelsandbodyconditionalsoinfluencethepos@&xmanestrus interval (12). Suckling increasesthe intervalfrom parturitionto first estrus (13) by delaying the release of gonadotrophinreleasing hormone from the hypothalamusand by modifying the responsivenessof the pituitary to steroids (14, 15). An increase in suckling intensityalso increasesthe postpartumanestrusintervaland is dependenton nutritionallevels (5). Hence,managementoptionseitherthroughnutritionalmanipulationand/or reducingsucklingintensitycouldreducethepost~anestrus interval and improve subsequent fertility (16, 17). This study was designed to examine two management options which may be applicable in snmll-holder situationsin Ethiopia,namely, the effects of supplementaryfeedingwith molassesblockscontaininglO% urea ortheuseoftwice-dailysucklingon postpartumreprcductiveperfomanceof Zebucowswhichcalve during the dry season. MATEIRDLS AND METHODS
The study was undertakenat Gobe Ranch of the EthiopianMinistry of Agriculture,located350 km southwest of Addis Ababa, atan altitudeof 2660 m. The area experiencesa bimcdal rainfall pattern, with a mean annual rainfallof 1543 mm. A short rainy seasonlasts fromMarchtoMay, followed byalongrainyseasonfromJunetoSepte.n&er.Adryseasonintervenesfrom oCtobertoFebruary.Meanmonthlymin~andmax~temperatureSrange from 4.2 to 9.2OC and from 16.5 to 28.3OC,respectively(2). Atotalof150 cows, intheirlastmonthofpregnancy, wereselected from Small FastAfricanZebucowsbasedonexpect&calving dates. At calving, the cows (n = 120) were allocated to either receive supplementaryfeed or to serve as controls.Within each nutritionalgroup, the cows were allocatedat random either to the continuousor twice-daily sucklinggroup.Allcowsgrazednaturalpasturecamprisedofgrassessuch as Chlorisqavana.Setariasnhacelata,and Panicumcoloratumandof legumes suchasTrifoliumsem.ioilosum, Glvcinewightii,andTt-ifoliumburchellianum. abreediqherdof
Supplemented cows were provided ad libitum with molasses blocks containing10% urea. Composition(w/w) of the blocks was molasses (42%), wheat bran (25%), urea (lo%), Diammoniumphosphate (3%) and salt (5%). PaJdered cement (15%)was also incorporatedasahardeniq agenttoprovide better weathering properties of the block under the generally humid environmentalconditions. Restricted suckling groups suckled their calves twice daily for 30 minutesat7a.m. andat5p.m.Calvingbcdyweightandbcdyconditionscores
Theriogenology
99
(E!CS; l=thin, 9= fat) of cows (18)andcalfbirhhweightswererecmrded, and subsequent data on weight and condition changes were collezted at mnthly intervalsuntil weaningat 8 months of age.
Twoweeksbeforethestartofmati~~~, twosetsof semensampleswere collated by electroajaculation from 15 mature bulls (aged 6 to 8 years) selected frm a bull herd. Eight bulls with apparantly normal tastes, accsptablesemenquality, andwithamsan (+SEM)scrotalcirclrmferenceof 31.42:0.5 an were used for breeding.'Ihebulls were fitted with chinball ~k~rS,and2bullswereintroducedintoeachofthe4treatmentgroups21 days after the first cm had calved. The bulls were rotated between treatmtgroupsat2-weekintervals. Cows were under 24-hourcontinuousobservationby experiencedherdsmen for estrus detection and mating activitiesthroughoutthe study period. Weekly palpations per rectum were also parformad to examine wariah structures.Pregnancy was determinad45to 60 days after mating. Cata fromatotalof 38 animals frmthe4 differenttreatmntgroups were removed frum the analysis due to cow and/or calf mortalities.The effsc~ofsupplementation,suckling, timeandtheirinteractionsonchanges in bcdy weight, body conditionscore and calf bcdyweightwere analyzedby repeatedmeasu?zesanalysis, usingtheGenera1 LinearModels (GLM)prccedure of the SAS prcgram (19).Mortalityand reprcductiondata were analyzedby analysisof variance,with nutritionalsupplementation and sucklingas the main effects.Polymn.ialregressionanalyseswerealsousedtodeterminethe effectsof body weight and conditionon reproductivetraits.
M~dailymolassesblockintakewas1.8kg/head.Dataoncalvingbody weight and body conditionscore, cow aridcalf sunfival,and calf weaning weightandpreweaningaveragedailygain (AM;)arepresentedinTable1. The patternsof changes in cowbcdyweight andbody conditionscore and in calf preweaningbcdyweight are also presentedin Figures 1 to 3. Calving bcdy weight and body condition score did not differ between supplemented and control ems or between continucxsly and restrict& suckXrigcows. Themortalityratesofcmiswerelow, ranging from O.Oto 6.7%, and were not influehcsd by either supplementationor suckling reginlens.Calfrmxtalityrates,however,weresignificantlyreducedby20% throughsupplementation, ahdwhiletherewas adifference insurvival rates of l:#%in favor of the restrictedsucklinggroup, this differencewas not signj.ficant. Body weights increasedby 38 and 14 kg between calving and weaning in supplemanted and control cows, respectively, but these differehceswere not significantnor were there any effectsof sucklingon bcdyweightchanges. Overall trends inpostpartumbcdyweightchahgesare shown in Figure 4. Preweaning calf growth rates ahd weaning weights (adjust&to 240 days) were not influencedbyeitherdamsupplsmahtationor by restrictedsuckling (Figure3). There were significant(PcO.05)nutrition-by-time interactioneffects on changes in ccw body weight and body conditionscore (Figures1 and 2), with these differencesoxurringduringthewet seasonaftersupplcmantary feedjnghadceased.Similarpatternswerealsoobservedinpreweaningcalf growth~f0nnance (Figure3).
100
Theriogenology
Table 1. Least squares means (+SEM) for cow and calf survival rates, adjustedcalfweaningweightto 240 days,preweaningaveragedaily weight gain (AM;),ccw b&y weight and body conditionscore and reprcductiveperfomance in postpartumSmall East African Zebu cawsundertwonutritionaltreatmentsandtwosuckling reginms.
Supplementedmws Continuous Restricted suckling suckling (n = 19) (n = 27)
Variables
Controlcows Continuous Restricted SUCklins
Suckling
(n = 17)
(n = 19)
Survivalrate (%) Cow Calf
93.3a 70.0a
Weaningweight (kg) 64.8+ 2.ga -
(g/day)
100.0a 9o.Ob 58.25 3.4a
96.7a 60.0a
96.7a 66.7a
59.5+ 2.2a
66.8+2.3a
232.2+15.5a 255.1+14.1a 229.6+12.5a 254.9+11.4a
Cow bcdy weight (kg) at calving atweaning
192.2+ 5.Ba 185.5& 4.ga 217.4+ 4.1a 233.6+ 3.5a
190.1+ 6.1a 217.3+ 4.4a
188.95 5.Ba 189.e 4.1a
4.2+ 0.2a 5.42 0.1a
4.1+ 0.2a 4.35 0.1a
Cow bcdy conditionscore at calving atweaning EIstrus(%)
4.22 0.2a 5.75 0.1a 52.6a
3.82 0.2a 5.9+ 0.1a 74.1a
29.4b
73.7a
Calvingto 159.3+26.ga 127.62 6.Ba 202.qt_14.2a190.3+12.2a estrus (days) conception(days)172.3+19.4a 138.3+11.2a 206.5+_25.5a196.6+10.3a pregnancy (%)
31.6a
40.7a
11.8b
52.6a
arb Within a row, means followed by different sqerscripts differ significantly(EO.05). 'Ihenm&erofanimalsreferstoanhlswhichsumiveduntiltheendofthe expximent. Approximately35% of supplementedarid41% of control ems remained anestrous for the duration of the study (8 months), while restricted sucklingsignificantly (RO.05) increas&thepercentageofcycliccows from 42to74%. Regular ovariancyclicactivitydidnotwmence untiltheendof the fourth month post partm. Supplementationreduced the posm anestrusintervalby54daysardrestrictedsucklingby13 days,butth~ trendswerenotsignificant.The overallmeanpregnancyratewas 35% andwas
101
Jheriogenology
I
250
250
FiguIre
0 -0 0-O A-A A-A
1. changes
Supplement-Continuous Supplement-Restricted Control-Continuous Control-Restricted
inpostparhrm
ba3y
suckling suckling
weight
O-
0 Supplement-Contlnuoua
l-
l Supplement-Restricted
A-A A-
Control-Continuous A Control-Restricted
Figure 2. changes in pcetpartm zeb.lccws.
suckling suckling
in Small
East
African Zebu cows.
suckling suckling
suckling suckling
bcdy cmdition score in 31~111 East African
Theriogenology
102
100 0
0 -
0 Supplement-Restricted
A-A
60 G & 2
0 -
A-
Supplement-Continuous Control-Continuous
A Control-Restricted
suckling suckling
suckling suckling
60
.o, f Q
40
tz
20
t 0
0
1
I I
I
+
I
I I
4 1
I
2
3
4
5
6
7
6
Age Figure
3.
Ihe effects prewWrling
(montW
of dam supplementation gxWth performance.
0
Supplement-Continuous
I
Supplement-Restricted
lz9 Control-Continuous 5
Control-Restricted
and suckling
intensity
on calf
suckling suckling
suckling suckling
d li postpartum Figure
4.
period
(months)
cIlmnges in postpartum body weight in
Small
East
African
Zebu CCIWS.
relative
to calving
body
weight
103
Theriogenotogy
notsignificantlyinfluencedbyeithersupplementationorsucklingregimens, al~l~ughtwiceasmanyrestrictedsucklingcawsconceivedthanwntinuously suckling animals. No significantassociationswere found between body weight, bcdy conditionscore, calf growth rate and reproductivetraits. DISCUSSION ~=alvingsoccurredbetweenJanuaryandFebruaryafter~hadundergone 3to4monthsofnutritionalstressduringthedry season.Studieselsewhere (20) have indicateda significantrelationshipbetween the severity and durationof dry season nutritionalstressand subsequentconceptionrates: morenrertheserelationshipsmayhavecontributedtotheresultsfoundhere. Cow body weight and body conditionwere low at calving, and relativeto weight and condition at calving, the cows also continued to loose body weight and conditionduring the first 4 to 5 months post partum. Neither supplementaryfeedingnorrectucedsucklinginfluencedtheselossesduring the postpartumperiod, when the cows had to cope with both lactational demandsandmainlx.nanceofbodyweightduringthepericdofdeteriorating pasture~lity.Supplementaryfeedingwithmolassesblockscontainingurea hasinlsofailedto~r~ebodywei~tperformanceinBosindicusrrosscows during the dry season in northernAustralia (21, 22). During periodsof inadequatenutritioncows determinetheir priorities in nutrientallocationand utilization(9). In this study, prioritiesfor nutrientutilization appeared to be those of cow survival,milk production to ensure calf survival,body repair andmaintenance,accumulationof body reserveand, finally,reproduction.Cows calvingat a lowerbcdyweightand in~oorbody conditionhavebeen observed to takelongerto recover and resume ovarian activitythan ccws at a higher body weight and in good bcdy condition (3, 4, 23). Use of molassesblocks containingurea has failedto improvepostpartumreproductiveperformancein previousstudiesusing m indicus cattle in tropical Australia (22, 24, 25). Both body weight and fertilityresponsemaydependontheweightandconditionofcows at calving (26, 27). Neither low nor high energy diets influencedthe interval from calvingto firstestrus inGyrccwsthatcalved inagoodbady condition (28).Similarly,provisionofahighproteinsupplemantfor28 days fromCay 30 postpart~tobeef cowswhichcalvedwithahighbcdyccndition scoredid not influencethe conceptionrate and the calving to conceptioninterval (29). Part of the explanationfor this absence of response may be that substantialallocationof nutrientstowardmilkproduction(andhence calf gravth) cccurs in anir&s supplementedpost partum (30). Alternatively, sucklingeffectsmayoverridethemodulatirq influenceofnutritionalstatus on postpartumreproductiveperformance(5).
Although restricted sucklirg increasedboth the proportion of ccx.xs exhibitingestrusandthepregnancyrate,themeanintezvalfrmncalvingto estrus was notdecreasedtoless than 5 months. Tfiemlete absence of ovarianactivityinnearly60%ofthecontinuouslysuckledcowsdemonstrates the suppressiveeffectsof suckLingon the hypothalamic-pituitary-gonadal axis (5).Theeffectsofweanirqstrategiessuchastemporaryweaning,early weaniq,partialweaningardreduci.ngsucklingintensitiesonreproductive performanceof cows have been variable.Sucklingaffectsthe intervalfrom calving to first estrus (31), and direct relationshipsbetween suckling intensityand postpartumanestrusintervaland subsequentpregnancyrates have been reported (16,17, 32, 33,). Incontrast,reducingsucklingtoonce
104
Theriogenology
daily did not influencethe mean postpartumintervalto primary ovulation in Africanerccws, but conceptionrates were u~@rovedby 40% (34). Althouqhcawmrtalitywas relativelylow,calfmortalitywasveryhiqh. In both small-holderfanningand pastoralproductionsystem in Ethiopia, calf mortality could be as hiqh as 50%. While it was not possible to undertake a detailed study of the aetioloqy of calf mortality,general minations indicatethat the major causes of observationsand postrnortemex calf mrtality are pneumonia, qeneral weakness and, in the case of continuouslysuckled calves, the inabilityto walk lonq distancesto and fromgrazingareas.Inrestrictedfllcklingcalves,poorhygienicconditions a&overcrowdedness contributedtolosses. The absence of differencesin calfgrowthpatternsduringthefirst4monthsalsoindicatesthatneither supplementationnor sucklinq re$m.ns influencedcalf qrwth until the beqinninqof the wet season. Under the conditions in which this study was undertaken&ostpartum supplementaryfeeding with molasses blocks containing 10% urea did not improvebcdyweiqht,badyconditionorreprcductiveperfomenoeofZebucms that calved at a low body weight and in poor body condition.However, a restrictedsucklinqreqimmtendedto improvethe proportionof cycliccams andenhanmdsubsequentpregnancyrates.Manaqenientintenrentionofeither supplementationor restrictedsuckling reduced calf mortality;however, there were no obvious effects on calf qrowth rates. Additionalmnaqmt options which need to be explored in this system should concentrateon approaches to improve precalvinqbody weight and condition and on the development of better calf raising and manaqement strategies aimed at reducingcalfmortalityand~r~ingpreweaninggraJthperf0~~.
1.
Entwistle,K.W. Optimizingreproductiverates incattle on low quality forage-baseddiets. Prcc. Int. Symposium in Animal Prcduction arxl Health, IAEA/FAo (Vienna)April, (1991).
E., Teqeqne,A., Mesfin,T. andTeklu, Y. Reproductive 2. Mukasa-Muqerwa, efficiencyof Bos imdicus (Zebu)cows under artificialinsemination managementin Ethiopia.Anim. Reprcd. Sci. a:63-72 (1991). 3. Entwistle, K.W. Factors influencing reprcduction in cattle in Review No. 43 (1983). Australia.AustralianMeatResmrch carmnittee 4. Randel, R.D. Nutritionand postpartumrebreedihqin cattle.J. Anim. Sci. =:853-862 (1990). 5. Williams, G.L. Sucklinq as a regulatorof postpartumrebreeding in cattle:a review.J. Anim. Sci. =:831-852 (1990). 6. Short,R.E., Bellows,R.A., Staiqmiller,R.B., Berardinelli,J.G. and Custer, E.E. Fhysioloqical mechanisms controllinq anestrus and infertilityinpxtpartumbeafcattle. J. Anim. Sci.=:799-816 (1990). 7. Lamond, D.R. The influenceof under nutritionon reproductionin the cow. Anim. Breed.Abstr. =:359-370 (1970).
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Toppe, J.H. The relationshipbetweenreproductionandunder-nutrition inbeef cattle.Wld. Anim. Rev. =:43-49 (1977).
9.
Peters,A.R. and Larmning, G.E. Regulationof ovarian functionin the postpartumcow: an endocrinemodel. Vet. Rec. =:236-239 (1986).
10. IXnn, T.G., Ingalls, J.E., Zm,
D.R. and Wiltbank, J.N. Reproductiveperfomance of 2-year-oldHerefordand Angus heifers as influenced by pre- and post-calvingenergy intake. J. Anim. Sci. a:719-726 (1969).
11. Rakestraw,J., Usby, K.S.,Wet-,
R.P. andwagner, J.J. Fostpartuo weight and body conditionloss and performanceof fall-calvingcows. lhericgenologya:461-473 (1986).
12. Holness, D.H., Hopley, J.D.H. and Hale, D.H. The effect of plane of nutrition,liveweight,temporary weani.ng and breed on the occurrence of cestrus inbeef cows during thepostpartunpericd. Anti. Prcd. &Y:47-54 (1978). 13. Oxenreider,S.L. &Wagner, W.C. Effectoflactationandeneqy intake on postpartumovarian activityin the cow. J. Anim. sci. =:1026-1031 (1971). 14. Forrest,P.K., Rhodes, R.C., III and Rardel, R.D. Effect of variable sucklingintensityand estrogenadministration upon serum luteinizing hormone in Brahrancows. Theriogenology~:333-339 (1980). 15. Stevenson, J-S., Spire, M.F. and Britt, J.F. E&radio1 induced luteinizinghormone(IH)inpostpartuosuckled(S)andmilked (M)cows: ovariandependence.J. Anim. Sci. ~(Suppl. 1):394abstr. (1982). 16. Randel,R.D. Effect of once-dailysucklingon postpartunintervaland ccw-calfperfonrance offirst-calf Brahman ~Herefordheifers.J. Anim. Sci. 53:755-757 (1981). 17. Reeves, J.J. and Gaskins, C.T. Effect of once-a-day nursing on rebreedingefficiencyof beef co&. J. Anim. Sci. =:889-891 (1981). M.H. A guide to conditionscoringof 18. Nicholson,M.J. and Butter-worth, Zebu cattle. InternationalLivestockCentre for Africa (IICA),Addis Abeba, Ethiopia (1986). 19. SAS User's Manual. Statistical Analysis Systems,Gary, NC, USA, 1987. 20. Anderson,V.J. Statistical Models of Factors AffectingconCeptionRate of Beef Cattle in Northern Queensland. M.Sc. ?he.sis.James Ccok University,Australia,1990. 21. Holroyd, R.G., Allen, P.J. and O'Rourke,P.K. Effect of pasture type and supplementaryfeedingon the reproductiveperformanceof cattle in the dry tropics of North Queensland.Au&. J. Exp. Agric. Anti. Husb. =:197-206 (1977).
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22. Holroyd,R.G.,Mason,G.W.J.,Lcxtcn,I.D.,Knights, P.T. andOQourk, P.K. Effects of weaningand supplementation on performanceof Brahmm cross cum and their progeny.Aust. J. Expt. Agri. a:ll-20 (1988). 23. McClure, T.J. Infertilityin beef cattle. AustralianMeat Research ConmutteeReview No. 11 (1973). 24. Siebert,B.D., Playne,M.J. and Edye, L.A. The effectsof climate and nutrient supplementon the fertilityof heifers in north Queensland. Proc. Au&. Sot. Anim. Prcd. =:249-252 (1976). 25. Holroyd,R.G., O'Rourke,P.K., Clarke,M.R. andLcxton, I.D. Influence ofpasturetype and supplementon fertilityandliveweightofems, and progenygrowthrateinthedrytrOpicsofnorthernQueens1and.AuSt.J. Exp. Agric. Anim. Hush. 23:4-13 (1983). 26. Dunn, T.G. and Kaltenbach,C.C. Nutritionand the postpartuminterval inthe ewe, sow, mare andcow. J. Anim. Sci. ~(Suppl. 2):29-39 (1980). 27. Fkhards, M.W., Spiker, J.C. andWarner,M.B. Effectofvaryinglevels of postpartumnutritionand body conditionat calving on subseqent reproductiveperformance in beef cattle. J. Anim. Sci. =:300-306 (1986). 28. Moore, C.P. and da Rmha, C.M.C.Reprcductiveperformance 0fGyrccws: the effect of weaning age of calves and postpartumenergy intake.J. Anim. Sci. 57~807-814 (1983). 29. Wettemnn, R-P., Hill, G.M., EDyd, M.E., Spitzer,J.C., Forrest,D.W. and Beal, W.E. Reprcductiveperfonxanceofpostpartumbeefcows after short-term calf separation and dietary energy and protein supplementation. Qx?riogenolcgy&:433-443 (1986). 30. McSweeney,C-S., Jolly, P.D. and Entwistle,K.W. Effects of suckling vs undernutritionon postpartumancestrus interval in Bos indicus cows. Prcx. Aust. See. Reprcd. Biol. a:138 abstr. (1990). 31. Short, R.E., Bellows,R.A., Moody, E.L. and Howland, B.E. Effects of suckling and mastectcmyon bovine pxkpartm reprcduction.J. Anim. Sci. 34:70-74 (1972). 32. Wettemnn, R.P., Turman, E-J., Wyatt, R.D. and Tutusek,R. Influence of sucklirq intensityon repr&uctiveperformance of range ccws. J. Anim. Sci. 47~342-346 (1978). 33. Bluntzer,J-S., Beverly,J.R., Ha?ms, P.G., Fleeger,J.L. and Forrest, D.W. Effectsof once-dailysucklingon return to estrus and pregnancy in postpartum primiparous Brahman-percentagecows. J. Anim. Sci. 55(Suppl.1):50 abstr. (1982). 34. Wells, P.L., Holness, D.H., McCabe, C.T. and Lishn?an, A.W. Fertility in the Africaner cm. 3. Once-a-daysuckling and its effect on the patternof remnption of ovarianactivityand conceptionrate in early lactation.Anim. Reprcd.Sci. u:l-12 (1986).
38:97-106,
1992
AsageTegegne,1r2,K.W. Entwistle2and E. Mukasa-Mugemal 1InternationalLivestockCentre for Africa(ILGA) P.O.Box 5689, Addis Ababa, Ethiopia 2craduateSchoolofTropicalVeterinaryScienceandAgriculture James CookUniversity,TownsvilleQld 4811, Australia Received for publication:September 6, 1991 Accepted:ApriL 25, 1992
Small EastAfricanZebucows(n=120)whichcalvedduringthed_ryseason wereusedtodetermine theeffectsofpostpartusnutritionalsupplementation and suckling intensityon bcdy weight,body conditionscore, reproductive perfc~~~andoncalfmortalityandpreweaninggrowthperformance. Cows were allocated based on calving bcdy weight to either receive a supplementaryfeed of molasses blocks containing10% urea or to serve as con~-olsandtobegrazedonly.Withinnutritio~lgroups, axswerefurther assigm3d either to continuoussuckling or to restrictedsuckling twice daily. Intactbullswereintroduced21daysafterthefirstcawhadcdlved, anddatawerecollected for8 nmths. Calvingbodyweightandbodycondition score of dams ranged from 186 to 192 kg and from 3.8 to 4.2 and did not differ amng the treatment groups. Supplemantaryfeedingsignificantly (p
Key wo?zds:Zebu cow, postpartum,reprcduction,nutrition,suckling INTROMJC!I'ION Postpartum anestms and low fertilityare the major causes of poor reproductiveperformance in cattle in tropical regions (1, 2). Factors influencing postpartum reproductive perforsance have been reviewed previously (3 - 6). Grazing cows calving durirq the dry season are often faced with inadequatenutrition (7, 8) while their nutrient demand for tissue repair and lactationare high. Lactatingems establishtheir Acknowledgements TheauthorsthanktheEthiopianMinistryofAgricultureforaccesstothe facilitiesandanimals,Mr. KassahunZewdiefortechnicalassistance,and Mr. Solcmmn Zewdie andMr. G. De'ath for advice on statisticalanalyses.
Copyright
0
1992
Butterworth-Heinemann
98
Theriogenology
priorities in nutrient utilization (9), and during periods of severe undernutritionsurvival of the cow and the calf become primary issues. Resumptionof ovarianactivityoftendoes not commence untilafterthe calf is weaned, and there are strong interactingeffects of nutrition and suckling (5). Rothbodyweightandbcdycondition (10)aswellas andthe rates of body wei~tand~conditionchangesduringthepostpartumperiodinfluenCethe anestrus interval and subseguent fertility (11). However, precalvirq nutritionallevelsandbodyconditionalsoinfluencethepos@&xmanestrus interval (12). Suckling increasesthe intervalfrom parturitionto first estrus (13) by delaying the release of gonadotrophinreleasing hormone from the hypothalamusand by modifying the responsivenessof the pituitary to steroids (14, 15). An increase in suckling intensityalso increasesthe postpartumanestrusintervaland is dependenton nutritionallevels (5). Hence,managementoptionseitherthroughnutritionalmanipulationand/or reducingsucklingintensitycouldreducethepost~anestrus interval and improve subsequent fertility (16, 17). This study was designed to examine two management options which may be applicable in snmll-holder situationsin Ethiopia,namely, the effects of supplementaryfeedingwith molassesblockscontaininglO% urea ortheuseoftwice-dailysucklingon postpartumreprcductiveperfomanceof Zebucowswhichcalve during the dry season. MATEIRDLS AND METHODS
The study was undertakenat Gobe Ranch of the EthiopianMinistry of Agriculture,located350 km southwest of Addis Ababa, atan altitudeof 2660 m. The area experiencesa bimcdal rainfall pattern, with a mean annual rainfallof 1543 mm. A short rainy seasonlasts fromMarchtoMay, followed byalongrainyseasonfromJunetoSepte.n&er.Adryseasonintervenesfrom oCtobertoFebruary.Meanmonthlymin~andmax~temperatureSrange from 4.2 to 9.2OC and from 16.5 to 28.3OC,respectively(2). Atotalof150 cows, intheirlastmonthofpregnancy, wereselected from Small FastAfricanZebucowsbasedonexpect&calving dates. At calving, the cows (n = 120) were allocated to either receive supplementaryfeed or to serve as controls.Within each nutritionalgroup, the cows were allocatedat random either to the continuousor twice-daily sucklinggroup.Allcowsgrazednaturalpasturecamprisedofgrassessuch as Chlorisqavana.Setariasnhacelata,and Panicumcoloratumandof legumes suchasTrifoliumsem.ioilosum, Glvcinewightii,andTt-ifoliumburchellianum. abreediqherdof
Supplemented cows were provided ad libitum with molasses blocks containing10% urea. Composition(w/w) of the blocks was molasses (42%), wheat bran (25%), urea (lo%), Diammoniumphosphate (3%) and salt (5%). PaJdered cement (15%)was also incorporatedasahardeniq agenttoprovide better weathering properties of the block under the generally humid environmentalconditions. Restricted suckling groups suckled their calves twice daily for 30 minutesat7a.m. andat5p.m.Calvingbcdyweightandbcdyconditionscores
Theriogenology
99
(E!CS; l=thin, 9= fat) of cows (18)andcalfbirhhweightswererecmrded, and subsequent data on weight and condition changes were collezted at mnthly intervalsuntil weaningat 8 months of age.
Twoweeksbeforethestartofmati~~~, twosetsof semensampleswere collated by electroajaculation from 15 mature bulls (aged 6 to 8 years) selected frm a bull herd. Eight bulls with apparantly normal tastes, accsptablesemenquality, andwithamsan (+SEM)scrotalcirclrmferenceof 31.42:0.5 an were used for breeding.'Ihebulls were fitted with chinball ~k~rS,and2bullswereintroducedintoeachofthe4treatmentgroups21 days after the first cm had calved. The bulls were rotated between treatmtgroupsat2-weekintervals. Cows were under 24-hourcontinuousobservationby experiencedherdsmen for estrus detection and mating activitiesthroughoutthe study period. Weekly palpations per rectum were also parformad to examine wariah structures.Pregnancy was determinad45to 60 days after mating. Cata fromatotalof 38 animals frmthe4 differenttreatmntgroups were removed frum the analysis due to cow and/or calf mortalities.The effsc~ofsupplementation,suckling, timeandtheirinteractionsonchanges in bcdy weight, body conditionscore and calf bcdyweightwere analyzedby repeatedmeasu?zesanalysis, usingtheGenera1 LinearModels (GLM)prccedure of the SAS prcgram (19).Mortalityand reprcductiondata were analyzedby analysisof variance,with nutritionalsupplementation and sucklingas the main effects.Polymn.ialregressionanalyseswerealsousedtodeterminethe effectsof body weight and conditionon reproductivetraits.
M~dailymolassesblockintakewas1.8kg/head.Dataoncalvingbody weight and body conditionscore, cow aridcalf sunfival,and calf weaning weightandpreweaningaveragedailygain (AM;)arepresentedinTable1. The patternsof changes in cowbcdyweight andbody conditionscore and in calf preweaningbcdyweight are also presentedin Figures 1 to 3. Calving bcdy weight and body condition score did not differ between supplemented and control ems or between continucxsly and restrict& suckXrigcows. Themortalityratesofcmiswerelow, ranging from O.Oto 6.7%, and were not influehcsd by either supplementationor suckling reginlens.Calfrmxtalityrates,however,weresignificantlyreducedby20% throughsupplementation, ahdwhiletherewas adifference insurvival rates of l:#%in favor of the restrictedsucklinggroup, this differencewas not signj.ficant. Body weights increasedby 38 and 14 kg between calving and weaning in supplemanted and control cows, respectively, but these differehceswere not significantnor were there any effectsof sucklingon bcdyweightchanges. Overall trends inpostpartumbcdyweightchahgesare shown in Figure 4. Preweaning calf growth rates ahd weaning weights (adjust&to 240 days) were not influencedbyeitherdamsupplsmahtationor by restrictedsuckling (Figure3). There were significant(PcO.05)nutrition-by-time interactioneffects on changes in ccw body weight and body conditionscore (Figures1 and 2), with these differencesoxurringduringthewet seasonaftersupplcmantary feedjnghadceased.Similarpatternswerealsoobservedinpreweaningcalf growth~f0nnance (Figure3).
100
Theriogenology
Table 1. Least squares means (+SEM) for cow and calf survival rates, adjustedcalfweaningweightto 240 days,preweaningaveragedaily weight gain (AM;),ccw b&y weight and body conditionscore and reprcductiveperfomance in postpartumSmall East African Zebu cawsundertwonutritionaltreatmentsandtwosuckling reginms.
Supplementedmws Continuous Restricted suckling suckling (n = 19) (n = 27)
Variables
Controlcows Continuous Restricted SUCklins
Suckling
(n = 17)
(n = 19)
Survivalrate (%) Cow Calf
93.3a 70.0a
Weaningweight (kg) 64.8+ 2.ga -
(g/day)
100.0a 9o.Ob 58.25 3.4a
96.7a 60.0a
96.7a 66.7a
59.5+ 2.2a
66.8+2.3a
232.2+15.5a 255.1+14.1a 229.6+12.5a 254.9+11.4a
Cow bcdy weight (kg) at calving atweaning
192.2+ 5.Ba 185.5& 4.ga 217.4+ 4.1a 233.6+ 3.5a
190.1+ 6.1a 217.3+ 4.4a
188.95 5.Ba 189.e 4.1a
4.2+ 0.2a 5.42 0.1a
4.1+ 0.2a 4.35 0.1a
Cow bcdy conditionscore at calving atweaning EIstrus(%)
4.22 0.2a 5.75 0.1a 52.6a
3.82 0.2a 5.9+ 0.1a 74.1a
29.4b
73.7a
Calvingto 159.3+26.ga 127.62 6.Ba 202.qt_14.2a190.3+12.2a estrus (days) conception(days)172.3+19.4a 138.3+11.2a 206.5+_25.5a196.6+10.3a pregnancy (%)
31.6a
40.7a
11.8b
52.6a
arb Within a row, means followed by different sqerscripts differ significantly(EO.05). 'Ihenm&erofanimalsreferstoanhlswhichsumiveduntiltheendofthe expximent. Approximately35% of supplementedarid41% of control ems remained anestrous for the duration of the study (8 months), while restricted sucklingsignificantly (RO.05) increas&thepercentageofcycliccows from 42to74%. Regular ovariancyclicactivitydidnotwmence untiltheendof the fourth month post partm. Supplementationreduced the posm anestrusintervalby54daysardrestrictedsucklingby13 days,butth~ trendswerenotsignificant.The overallmeanpregnancyratewas 35% andwas
101
Jheriogenology
I
250
250
FiguIre
0 -0 0-O A-A A-A
1. changes
Supplement-Continuous Supplement-Restricted Control-Continuous Control-Restricted
inpostparhrm
ba3y
suckling suckling
weight
O-
0 Supplement-Contlnuoua
l-
l Supplement-Restricted
A-A A-
Control-Continuous A Control-Restricted
Figure 2. changes in pcetpartm zeb.lccws.
suckling suckling
in Small
East
African Zebu cows.
suckling suckling
suckling suckling
bcdy cmdition score in 31~111 East African
Theriogenology
102
100 0
0 -
0 Supplement-Restricted
A-A
60 G & 2
0 -
A-
Supplement-Continuous Control-Continuous
A Control-Restricted
suckling suckling
suckling suckling
60
.o, f Q
40
tz
20
t 0
0
1
I I
I
+
I
I I
4 1
I
2
3
4
5
6
7
6
Age Figure
3.
Ihe effects prewWrling
(montW
of dam supplementation gxWth performance.
0
Supplement-Continuous
I
Supplement-Restricted
lz9 Control-Continuous 5
Control-Restricted
and suckling
intensity
on calf
suckling suckling
suckling suckling
d li postpartum Figure
4.
period
(months)
cIlmnges in postpartum body weight in
Small
East
African
Zebu CCIWS.
relative
to calving
body
weight
103
Theriogenotogy
notsignificantlyinfluencedbyeithersupplementationorsucklingregimens, al~l~ughtwiceasmanyrestrictedsucklingcawsconceivedthanwntinuously suckling animals. No significantassociationswere found between body weight, bcdy conditionscore, calf growth rate and reproductivetraits. DISCUSSION ~=alvingsoccurredbetweenJanuaryandFebruaryafter~hadundergone 3to4monthsofnutritionalstressduringthedry season.Studieselsewhere (20) have indicateda significantrelationshipbetween the severity and durationof dry season nutritionalstressand subsequentconceptionrates: morenrertheserelationshipsmayhavecontributedtotheresultsfoundhere. Cow body weight and body conditionwere low at calving, and relativeto weight and condition at calving, the cows also continued to loose body weight and conditionduring the first 4 to 5 months post partum. Neither supplementaryfeedingnorrectucedsucklinginfluencedtheselossesduring the postpartumperiod, when the cows had to cope with both lactational demandsandmainlx.nanceofbodyweightduringthepericdofdeteriorating pasture~lity.Supplementaryfeedingwithmolassesblockscontainingurea hasinlsofailedto~r~ebodywei~tperformanceinBosindicusrrosscows during the dry season in northernAustralia (21, 22). During periodsof inadequatenutritioncows determinetheir priorities in nutrientallocationand utilization(9). In this study, prioritiesfor nutrientutilization appeared to be those of cow survival,milk production to ensure calf survival,body repair andmaintenance,accumulationof body reserveand, finally,reproduction.Cows calvingat a lowerbcdyweightand in~oorbody conditionhavebeen observed to takelongerto recover and resume ovarian activitythan ccws at a higher body weight and in good bcdy condition (3, 4, 23). Use of molassesblocks containingurea has failedto improvepostpartumreproductiveperformancein previousstudiesusing m indicus cattle in tropical Australia (22, 24, 25). Both body weight and fertilityresponsemaydependontheweightandconditionofcows at calving (26, 27). Neither low nor high energy diets influencedthe interval from calvingto firstestrus inGyrccwsthatcalved inagoodbady condition (28).Similarly,provisionofahighproteinsupplemantfor28 days fromCay 30 postpart~tobeef cowswhichcalvedwithahighbcdyccndition scoredid not influencethe conceptionrate and the calving to conceptioninterval (29). Part of the explanationfor this absence of response may be that substantialallocationof nutrientstowardmilkproduction(andhence calf gravth) cccurs in anir&s supplementedpost partum (30). Alternatively, sucklingeffectsmayoverridethemodulatirq influenceofnutritionalstatus on postpartumreproductiveperformance(5).
Although restricted sucklirg increasedboth the proportion of ccx.xs exhibitingestrusandthepregnancyrate,themeanintezvalfrmncalvingto estrus was notdecreasedtoless than 5 months. Tfiemlete absence of ovarianactivityinnearly60%ofthecontinuouslysuckledcowsdemonstrates the suppressiveeffectsof suckLingon the hypothalamic-pituitary-gonadal axis (5).Theeffectsofweanirqstrategiessuchastemporaryweaning,early weaniq,partialweaningardreduci.ngsucklingintensitiesonreproductive performanceof cows have been variable.Sucklingaffectsthe intervalfrom calving to first estrus (31), and direct relationshipsbetween suckling intensityand postpartumanestrusintervaland subsequentpregnancyrates have been reported (16,17, 32, 33,). Incontrast,reducingsucklingtoonce
104
Theriogenology
daily did not influencethe mean postpartumintervalto primary ovulation in Africanerccws, but conceptionrates were u~@rovedby 40% (34). Althouqhcawmrtalitywas relativelylow,calfmortalitywasveryhiqh. In both small-holderfanningand pastoralproductionsystem in Ethiopia, calf mortality could be as hiqh as 50%. While it was not possible to undertake a detailed study of the aetioloqy of calf mortality,general minations indicatethat the major causes of observationsand postrnortemex calf mrtality are pneumonia, qeneral weakness and, in the case of continuouslysuckled calves, the inabilityto walk lonq distancesto and fromgrazingareas.Inrestrictedfllcklingcalves,poorhygienicconditions a&overcrowdedness contributedtolosses. The absence of differencesin calfgrowthpatternsduringthefirst4monthsalsoindicatesthatneither supplementationnor sucklinq re$m.ns influencedcalf qrwth until the beqinninqof the wet season. Under the conditions in which this study was undertaken&ostpartum supplementaryfeeding with molasses blocks containing 10% urea did not improvebcdyweiqht,badyconditionorreprcductiveperfomenoeofZebucms that calved at a low body weight and in poor body condition.However, a restrictedsucklinqreqimmtendedto improvethe proportionof cycliccams andenhanmdsubsequentpregnancyrates.Manaqenientintenrentionofeither supplementationor restrictedsuckling reduced calf mortality;however, there were no obvious effects on calf qrowth rates. Additionalmnaqmt options which need to be explored in this system should concentrateon approaches to improve precalvinqbody weight and condition and on the development of better calf raising and manaqement strategies aimed at reducingcalfmortalityand~r~ingpreweaninggraJthperf0~~.
1.
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