Sciences Agronontiques et Dâteloppement 6 (l): 5 - 11,2011ISSN 1814-6112

Effect of incorporating maize cobs (Zea mais) as a source of crude fïbre onthe growth performance of grower rabbits

H.F. Defang, A. Teguia, F. Ngoula, A.T. Niba, A. Kenfack, J.R. Kana, F. Tendongkeng,J. Tchoumboue & J. Ndessap

Depaftment of Animal Production, Faculty of Agronomy and Agricultural Sciences, University ofD schang, Cameroon. E- mai I : fciefan g@yah oo. corn

ABSTRACTA nine - week feeding trial was conducted to evaluate the effect of maize cobs (Zea mais) as a

source of crude hbre on the growth performance of local rabbits. Thirty-two-grower (16

males and 16 females) rabbits were randomly allotted to four dietary treatments of 8 (4 males

and 4 females) rabbits per treatment in a completely randomised design experiment with 4

replicates per treatment. The matze cobs were included at 0, 8, 13 and 21o in diets. The

results showed that average feed intake, mean body weight and weight gain did not differsignificantly between rabbits fed, the control diet and those fed diet containingl3o maize cobinclusion rate. However, they were significantly reduced in rabbits fed diets containing 8 and

27o crude fibre content. The feed efficiency (g feed: g gain) values and cost per kilogram livebody weight were comparable in all the treatments. Dietary treatments did not significantlyaffect carcass and organ characteristics. It was concluded that maize cobs are potential sourceof crude frbre and can be used up to 13o in the diet for grower rabbit without adverse effecton the performance of the animals.Key words z maize cobs, crude fibre, rabbits

RESUMEUn essai d'alimentation d'une durée de neuf semaines a été conduit pour évaluer l'effet deraffles de maïs comme source de cellulose sur les performances de croissance des lapereauxde race locale. A cet effet,32lapereaux (16 mâles et 16 femelles) ont été repartis de manièrealéatoire dans quatre groupes de 8 lapereaux (4 mâles et 4 fèmelles) chacun dans un dispositifcomplètement randomisé avec 4 répétitions par traitement. Les raffles de maïs ont été incluesà raison de 0, 8, 13 et 2Io dans la ration. Les résultats ont montré que la consommationalimentaire moyenne, le poids vif et le gain moyen quotidien des lapereaux de la rationtémoin étaient comparables à ceux des lapereaux ayant reçu la ration conteneant 13o deraffles de maïs, mais significativement moins élevés que ceux des lapereaux soumis auxrations contenant 8 et 21 o de raffles de maïs. L'indice de consommation, le coût deproduction du kilogramme de poids vif, le rendement carcasse et les caractéristiques desorganes n'ont pas été affectés de manière significative par les rations considérées. Il a étéconclu que les raffles de maïs constituent une source potentielle de cellulose et peuvent êtreinclues dans la ration des lapereaux en phase de croissance jusqu'à 13oZ sans effets néfastessur les performances des animaux.Mots clés: rffies de mals, cellulose bute, lapins

6 Defang et al.

INTRODUCTIOI{

Rabbits (Oryctolagus cuniculus) are herbivorous non ruminant animals withfunctional caecum, which have the capacity to extract nutrients of fibrous aliments andconveft them in high value proteins (De Toledo et a|.,2008). Its production has over the yearsgained popularity in many tropical countries especially in Africa and Central Africa inparticular. Currently, rabbit meat consumption is increasing because of its low cholesterolcontent. The meat does not form uric acid during metabolism therefore, it is being advocatedto people for good health. The meat is prescribed for diabetic, hypertensive and middle agedpeople. To meet the rising demand for rabbits there is need to increase production. However,one of the major constrains for rabbit production in developing countries is the high cost offeed.

As pseudo-ruminants, rabbits are capable of valorising large quantities of feed andforages rich in crude fibre content. Fibre regulates digestive disorder that can retardperformance or even cause fatal diarrheas, mainly at the growing phase (Santomia et al., 1993& Ferreira, 2008).

A decrease in crude fibre content in rabbit diet leads to an increase ofrisk ofdigestivedisorders through the decrease of volatile fatty acids concentration in the Çaecum (De Blas,\999). Conversely, high levels of crude fibre intake have an adverse effect on the effrciencyof feed utilisation (Mar1y and Vernay, 7984 & Yu et al., 1994) but the mechanism is unclear.After long - term feeding of high - fibre diet in rats, the absorption of nutrients wassignificantly decreased (Freeman, 1984).

In the sub-Saharan and Central Africa regions in particular, formulated rabbit mash isusually deficient in the crude fibre content. Fresh forage or hay (basal diet) is usually servedfree choice to booster this deficiency in intensive production. During the dry season the foragequantity and quality is low and forage conservation is hardly practiced in the tropics. It istherefore imperative to search for unconventional fibre sources that can replace forage duringperiod of scarcity. Among the potential sources of crude frbre, maize cob serves as analternative to tropical graminae because of its similarities in chemical composition. Maizecobs have high potentials and desirable agronomic and nutritive characteristics as fbedstufïs.Maize is widely cultivated in all the agro-ecological zones of Cameroon. It serves as a staplefood in Africa and it is a good source of income to farmers. Maize cob, the by-product, isusually used as fuel after the grains have been removed or discarded in the farm as organicmanure. Maize cobs are available, cheap and rich in crude fibre (35 - 3l%).In this context,maize cob with extraordinary potentials as crude fibre source appears like a viable alternativethat can substitute tropical fodder and help in the formulation of complete rabbit mash.

The present trial was designed to evaluate the effect of utilizing maize cob as a sourceof crude fibre on the growth performance of local rabbits.

MATERIALS AND METHODS

Study site

The study was conducted between October and December 2010 in the rabbitry unit ofthe Teaching and Research farm of the Faculty of Agronomy and Agricultural sciences(FASA) - University of Dschang, (The area is located at an altitude of 1420m above sea level,between longitude I0" 26'E and latitude 5" 26'N). The area receives an annual rainfall that

Sci. Agron. & Dév. 6(l): 5-l l, 20l l jrange between 1500 - 2000mm spread between mid March and mid November. Thetemperature varies between l0 and 25 'C

Processing of plant materials

Maize cobs of variety Kassai'used for this experiment were collected lrom Foumbotsub Division, Noun Division, West region of Cameroon. The cobs were dried in the sun forfour days then milled using a hammer mill of sieve size 2 mm. Samples of the milled maizecobs were analysed using the method AOAC (2000) and latter used for feed formulationTable2.

Animals and management

Thirly * two local (16 males and 16 females) rabbits aged between 72 - 13 weeks withaverage weight 983.44+45.359 were used for this trial. The experimental animals wereobtained from the parent stock in the rabbitry of the University of Dschang Teaching andResearch farm. The rabbits were raised in a well - ventilated house. The entire house, feeders,drinkers and hutches were previously cleaned and disinfected before receiving the animals.On anival at the unit, the animals were given prophylactic treatment against internal andexternal parasites by subcutaneous injection of Ivomec@ (0.Zmlkabbit). Fresh cool water andoral anti-stress were also administered to the animals on arrival. The rabbits were housed in atwo layer battery cages measuring 45 x 35 x 45cm with facilities for feeding, drinking andtrays for the collection of faeces and urine. The cages were kept in semi-closed rabbitry 1.5mhigh and the upper part 1m high closer to the roof was completed with wide open windowscovered with wire mesh and asbestos roofing sheets. Routine management procedures inintensive rabbit production were maintained to ensure disease management and comforl of theexperimental animals.

Experimental diets and design

At the commencement of the trial, the chemical composition of lhe maize cobs wasanalysed by the method AOAC, (2000) as shown in Table 1. Four diets were formulatecl. Thecontrol diet was composed of maize, wheat brand, palm kernel cake, cotton seed cake,groundnut cake, fish meal, molasses, premix (5%), bone meal, table salt and free maize cobswith crude fibre content of 7.7o/o while in other treatment groups the concentrate meal wasformulated such that the percentage of maize cobs in each of the diet was 8, l3 and 2lo withdietary crucle fibre content of 10.9,72.5 and 14.50 respectively. The percentage compositionand analysed nutritive values of the experimental diets are given on Table Z. the diéts wereiso-caloric and iso-nitrogeneous and were made in batches and offbred at a daily rate ofl5Ogianimal' In addition, each animal in the control group was given a daily allowance ofwilted Guatemala grass (Trypsacum laxum) free choice to booster the fibre conient of the diet.The grass was bundle - wrapped and hung in the cages. Water was provid ed acl- tibitum. AIIfeeds were offered in the morning after collection of the left over and wastage. Feeds offèredand left-over were recorder daily for each treatment to determine feed intàke. Live weightchange and fèed intake were recorded weekly until the end of the trial. Feed conversion ratior,r'as determined by dividing the unit of feed intake by that of life weight gain.

8 Defang et al.

Table 1: Proximate composition of maize cobsChemical characteristics %DMDry matterAshOrganic matterNitrogenCrude proteinCrude fibreDigestible energy Kcal/kg (calculated)

96.23

2.4697.530.090.54

37.103013

Table 2: Ingredients and composition of the diets used in the trialsMaize cob incorporation rates (0%) 21I3Maize (kg)Wheat brand (kg)Plam kernel meal (kg)Cotton seed cake (kg)Groundnut cake (kg)Fish meal (kg)Molasses (kg)Maize cob (kg)Premixr (5%) (kg)Bone meal (kg)Table salt (kg)TotalDetermined chemical analysisMetabolizable energy Kcal/kg2Crude protein (%)CrLrde fibre (%)Calcium (%)Phosphorous (%)EIPCost per kg of feed (FCFA)3

35JJ

18

42aJ

2

0.5

2

0.sr00

300916.31

1.720.15i.01

t84.49189.15

301015.1210.860.150.91

199.07178.30

300612.0510.050.760.96

191 "95180.80

306215.23

14.080.61

0.11201 .0s17 4.3s

25

2214

41

2.52

2l0.5

2

0.5

100

242419

4

1

J

J

13

0.52

0.5

r00

3031

1B

J

2

3

2

B

0.52

0.5

100

' premix (composition) g/kg: protein (500). fibre (30), Ca (85). p (3j) Na (i3I b,sine G0),nrethionine (19), methionine * cystine (24), M.E. (23O0kcal kg-r;, vitamine (100kg): A (l5x106lU),D3 (3xlo6 tu;, E (t.5x106 rng), vitamin (mg/kg): K3 (30), stQÉ1,82 (60), 83 (100), 86 (30), 812(i 50), Biotin (500), folic acid (10), niacin (350), rrace minerals (mg kg-r;: cl (4000), Mn (800), Fe(250), Cu (50),Zn (600), Co (5), I (2), Mg (850), Se (t)." rlatabolizable energy Kcal/kg was calculated according to Sibbald (1980) quored by INRA (19S9)' l€:655"95FCFA

Slaughter experiment and carcass analysis

At the end of the experiment 6 rabbits (3 males and 3 females) per treatment wererandomly selected staved for 24 h and the pre-slaughter weight taken. They were slaughteredaccording to Eschborn (1985). The dressing percentage was calculated while head, skin andinternal organs including heart, liver, lung, kidney and stomach were carefully removed andtrimmed of adhering tissues, weighed and expressed as percentage of live body weight. Thelength of the caecum and the gastro-intestinal track were taken using a meter tape and ratiocalculated.

Sci. Agron. & Dév. 6(l): 5-l I, 201 I 9Data analysis

Data were subjected to analysis of variance using SPSSS 12.0 for Windows. Wheresignificant differences were indicated, they were separated by Duncans Multiple Range Testat P : 0.05.

RESULTS AND DISCUSSION

The crude fibre and ash content of the analysed maize cobs was higher compared to31.6 and 1.65% reported by NRC (1977) but comparable to 39.2 and 2.7o reported byAdebowale (1988). The average data on feed consumption, weight gain, feed conversion ratio(g feed/g gain) and feed cost for the production of 1kg live body weight of grower rabbits feddiets containing graded levels of maize cobs are presented on Table 3. The mean feed intakewas significantly lower for rabbits fed diets containing 8 and 27Yo maize cobs enclosurecompared to rabbits fed the control and that containing 73o maize cobs. The results of thepresent study disagreed with the findings of Hoover et al. (1972) who reported that the meanweekly feed consumption of grower rabbits increased with the level of crude fibre content inthe diet. However, the results obtained for rabbits fed rations containing 8.0 and 2I.0% maizecobs and 8.87 and I4o dieLary crude fibre were comparable with the results obtained byHoover et al. (1995). Although the amount of feed consumed by the rabbits increased withage in all the treatments, means, live body weight was significantly higher for rabbits fed thecontrol diet compared to rabbits fed diet containing 8% maize cobs enclosure. These resultsare in conformity with those of Biyu et al. (1995) but lower than the norms established byGaracia et al. (1999) for fattener rabbits. The differences could be attributed to theheterogeneous nature of the breed. Body weight gain was significantly higher for rabbits fedthe control diet and that containing 130 maize cobs enclosure but comparable with rabbitsfed diet containing 13o maize cobs enclosure. No significant diflèrence was observedbetween the control diet and diet containing 21o maize cobs, diet containing 8 and 2lYomaize cobs. The results obtained are similar to the findings of Gidenne et at. (2002) and Khucet al. (2006) who reported that rabbits fed diet with fibre content of 1 1, 12 and l4o obtainedbody weight of 825, 923, and 9009 respectively thus suggesting that the crude fibre content inrabbit diets could be a determining factor on the performance of the animals. No significantdifference was observed between treatments groups for feed conversion ratio and the ieed costof producing 1kg live weight. The results on feed conversion ratio disagree with the resultsobtained with dietary crude fibre content higher than I0o as reported by Anington & Kelley(1976). The difference could be attributed the breed and diet used. Although, the feed cost perkg live body weight was comparable in all the treatments, it increased numerically with thelevel of maize cobs inclusion in the diets. This is probably due to the aclditionai simpleingredients of protein origin added to equilibrate the ration

Table 3: Performance of rabbits fed diets containing maize cobs as a source of crude fibreMaize cob Feed intake (g) weight gain (g) Feed co"t.^i""incorporation ratio

Cost per kg liveweight +SEM

FCFA4775.00+309.56', 1018.33+193.55b 4.78+036a

B 3770.00+432.75a 755.00+104.90a 5.24+132a907.09+68.604

915,37J'247 .09^927.84i106.35u930.2211t7.54^

13

2I5285.00+213.27b I$6.67+87.23b 5.13+0,59"4169.67+335.05^ 878.33*97.18"b 4.94+0.82"

Means in the column followed by different subscripts are significantly different acôording to DrnôarilMultiple Range Test (P:0.05)

l0 Defang et al.

Carcass characteristics

The results of the carcass characteristics are presented in Table 4. The slaughter weightand carcass yield of rabbits fed the test diets containing 8, 13 and 2loÂmaizes cob enclosurewere numerically higher than those of rabbits fed the control group and increased withincreased percentages of maize cob in the diets however, no significant difference wasobserved between treatment groups for this parameters. The results obtained for carcass yieldin this study are contrary to the report of Fieling (1991) who opined that the dressingpercentage of rabbits normally ranged from 50 lo 560Â and tends to be greater if the rabbitsare fully grown and have some abdominal fat. The differences could be attributed to the breed

used. The proportion of the lungs, heart, liver, kidney stomach, skin and the ratio caecum

length: digestive track length in this study showed no significant difference among treatmentgroups. it is a common practice in feed trials to use weights of some internal organs like liverand kidney as indicator of toxicity, Our observations regarding these organs in rabbits ofdifferent treatment groups suggest that the test diet did not contained any appreciable toxin as

reported by Iheukwumere et al. (2008) The abnormalities arise because of increasedmetabolic rate of the organs in attempt to reduce these toxic elements or anti-nutritionalfactors to non-toxic metabolites. Our observations regarding liver and kidney weights inrabbits of different treatment groups suggest that the test diets did not contain any appreciabletoxin. Values obtained by Ekpo et al. (2009) did not show any significant difference amongtreatments for lungs, kidney and liver of rabbits fed cassava tuber meals.

Table 4: Carcass characteristics of rabbits fed diets containing maize cobs as a source of crudefibre.

Parameters Maize cob incorporation rates (%)t3 2t

Live weight (g)Carcass yield g (%)Head g (%)Lungs e(%)Liver g (%)Hearl e (%)Kidney s (%)Stomach e(%)Skin g (%)Ratio caecum lengh:digestive track

1g92.50+ 101 .63ub

47.90+0.41u9.1 80+57b

0.69+0.0542.ggÈ0.16u0.56+0.18'0.76+0.014r.69L0.12^9.82+0.98u8.43+0.59u

2075.00+193.55b 1750,83+86.80a 2064.17+86.13b45.21+5.064 46.28+L47^ 46.37t1.176ug.3g+0.40u g.7g+002b g.72+0.040ub

0.62+0.054 0.860+0.26u 0.77+0.15a2.66+0.12u 2.98+0.46^ 2.76+0.35u0.4010.1204 0.62+0.150 0.41+0.08u0.75+0.40u 0.71*0.240u 0.74+03041.54+0.094 7.5+0.26a 1.52+0.32^10.2+20.60u 10.07+0.484 g.g5+0.90u

8.90+0.34u 8.66*0.33" g.6g+Lg4u

Means in row followed by difTerent subscripts are significantly different according to DuncansMultiple Range Test (P:0.05)

CONCLUSIOI{

The results obtained have clearly demonstrated that maize cobs are potential source of crudefibre for rabbits and can be used up to 1 30Â in the diet for grower rabbit without adverse effecton the performance of the animals.

Sci. Agron. & Dév. 6(l); 5-l I,201 I

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