Effect of supplementing wheat bran, Acacia albida leaf meal and their mixture on feed intake and carcass characteristics of Horro sheep fed vetch (Lathyrus sativus) haulm basal diet

Takele Feyera and Getachew Animut*

Ambo University, Department of Animal Science, P.O.Box 19, Ambo, Ethiopia
feyera.takele2008@gmail.com
* Haramaya University, School of Animal and Range Science, P.O.Box 138, Dire Dewa, Ethiopia

Abstract

Twenty five yearling male Horro lambs with initial body weights (IBW) of 23.14±2.45 kg (mean±SD) were used to determine effect of supplementation of wheat bran (WB), Acacia albida leaf meal (AA) or their mixture on nutrient  and carcass characteristics of yearling Horro lambs fed a basal diet of vetch (Lathyrus sativus) haulm (VH). Animals were blocked into 5 based on IBW and were randomly assigned to one of the following treatments: ad libitum feeding of VH either without supplement (CTL) or with daily supplement of 300 g DM of sole WB (300WB), sole AA (WB-AA), or mixture of the two at 2:1 (300AA) or 1:2 (WB-AA) ratios of WB:AA and fed for 84 days followed by carcass evaluation.

Intake of the basal diet DM was not affected by supplementation but intake of total DM and nutrients increased by supplementation. Differences in carcass characteristics followed the trend observed for feed intake conditions. Supplementation improved hot carcass weight and dressing percentage (P < 0.05) compared to the non-supplemented group. Among the supplemented groups 300AA had greater hot carcass weight (P < 0.05) than WB-AA.

Supplementation of WB, AA and their mixture to VH basal diet can be employed to enhance intake and carcass character of Horro sheep.

Key words: Legume, primal cuts

Introduction

In one way or another, the quantity and the quality of feed resources available and the feeding systems employed have great impact on livestock production and productivity. In areas where livestock are closely integrated with crop production, crop residues are considered as valuable sources of ruminant feeds. The tendency of increased acreage of cropping land is always at the expenses of decreased available grazing lands, thus boost the importance of crop residues as animal feed resources. However, crop residues are of generally low in nutritive value and are fibrous having low digestible organic matter (OM) per kg dry matter (DM)) and low crude protein (CP) content (Emyr 1994). The increasing pressure on land and the growing demand for livestock products makes it crucial to ensure the effective use of feed resources, including crop residues and other agro-industrial by-products. With the increasing need of human population for animal products, there is a need of matching feed resources available with animal nutrient requirements. Nevertheless, pulse crop resides/haulms have relatively better nutritive value than cereal straws but hardly supply animals’ maintenance requirement (de Leeuw 1997) which implies that there is a need of looking for some supplement options. Thus, supplementation of crop residues with agro-industrial by-products and/or plant protein sources will alleviate CP deficiency in fibrous feeds (Solomon 2001).

Use of improved forage and tree legumes as supplementary options for livestock have been investigated in Ethiopia (Melese et al 2002; Jemal et al 2004; Solomon et al 2004; Ajebu et al 2008). However, the information on the feeding value of most indigenous multipurpose trees and their concomitant effect on growth and carcass characteristics in Ethiopia are scanty and need further documentation. To this end FAO (2002) suggested that the urgent need of the farmers for high quality feed for ruminants in developing countries can be achievable through intensive utilization of multipurpose trees and shrubs as they have better nutritional quality nearly equivalent to grain based concentrates. According to Shayo (1998), leaves of multipurpose trees are highly digestible; contain high concentration of CP and minerals, and low cell wall contents. Among the well known indigenous multipurpose trees in Ethiopia, Acacia albida is one potential multipurpose tree capable of producing leaves and pods of high nutritive value. According to Hassan et al (2007) and NFTA (1997) A. albida is known to produce leaves and pods during dry season when most trees shade their leaves. This important characteristic of the plant is a key attribute that makes A. albida worthy of investigation as feed alternative for ruminants. Therefore, this study was carried out with the objective of investigating the effect of supplemental wheat bran, A. albida leaf meal and their mixtures on feed intake and carcass characteristics of yearling Horro sheep fed vetch (Lathyrus sativus) haulm basal diet.  A few lines on the current level of Lathyrus sativus cultivation in Ethiopia and its use may be included.
 

Materials and Methods

Study site, feeds and feed preparation

The study was conducted at Ambo University, Ambo Woreda, Oromia Region, Ethiopia which is located at 115 km West of Addis Ababa.  The site is situated at 8^o17’N-9^o56’N latitude and 37^o1’E-38^o45’E longitude and at mid altitude that ranges from 1,380 to 3,300 meter above sea level. The mean annual rainfall was 1079 mm and the mean minimum and maximum daily temperatures of the area were 12 and 26 ^oC, respectively.

The basal diet, vetch haulm (VH) used in the present study was collected from randomly selected peasant association in Ambo Woreda and hand chopped approximately to 4-5 cm length to increase its intake and decrease rate of selectivity by lambs and the processed haulm was thoroughly mixed and stored on concrete floor house until used. Acacia albida leaf meal was collected from Ambo University campus. Small side branches containing the green leaf was cut when leaf mass was maximal. The branches were stripped off the leaves and were air dried by spreading them thinly on plastic sheets under a shade for a period of 5-6 days. Dried leaves were finally ground with traditional mortar to prepare the leaf meal that was used as supplement for the study. Leaf meals prepared in different batches were mixed at the end to have a uniform leaf meal supplement. Wheat bran was purchased from Teltele flour factory found in Ambo town.

Experimental animals, experimental design, treatments and feed intake

Twenty five yearling entire male Horro lambs with initial body weights of 23.1±2.45 kg (mean±SD) having relatively similar body condition were used for the study. The lambs were in quarantine for 21 days and treated with 300 mg albendazole bolus for internal and with acarimic spray for external parasites, respectively. They were adapted to experimental feeds for 15 days followed by 84 days of feeding period to determine effect on feed intake and carcass parameters. The supplements were offered in two equal portions at 0800 and 1530 hours daily while the basal diet was offered once in the morning. Water and mineral salt licks were accessed freely to all lambs. 

A complete randomized blocked design with five treatments of five animals each was employed and lambs were blocked on the basis of  their initial body weight ( overnight fasting) and the five treatments were randomly assigned to animals in the block. Lambs were housed in concrete floor that penned individually. Treatments were ad libitum feeding of VH either without supplement (CTL) or with daily supplement of 300 g DM of sole wheat bran (300WB), sole A. albida leaf meal (AA), or mixture of the two at 2:1 (300AA) or 1:2 (WB-AA) ratios of wheat bran: A. albida. Feeds offered to experimental lambs and corresponding refusals were weighed and recorded daily throughout the experimental period to determine daily feed intake of experimental lambs.

Carcass measurements

At the end of the feeding trial, all lambs were slaughtered to assess treatment effect on carcass characteristics. Feed was withheld for 16 hours prior to slaughter and the next morning weight was taken as slaughter weight. The lambs were slaughtered following “Manual for the slaughter of small ruminants in developing countries” (Clotter 1985).

Empty body weight was calculated as slaughter weight less gut content. Hot carcass weight was estimated after removing weight of the head, skin, thoracic, abdominal and pelvic cavity contents, and the limbs. Dressing percentage was calculated as a ratio of hot carcass weight and slaughter weight or empty body weight basis. Finally, the carcass was split in the dorsal midline (Picture 1a) into right and left half and the left half was cut into the five primal cuts: neck and shoulder, breast and shank, rack, loin and leg (Picture 1b), respectively and weighed separately. Then the 11^th, 12^th, and 13^th ribs were separated and refrigerated at 4⁰C for 24 hours. After chilling for 24 hours the ribs was dissected between the 12^th and 13^th ribs and measurements on the 12^th and 13^th ribs were taken as average value for fat thickness (Picture 1c) and rib eye area (Picture 1d) based on the recommendation of Torell and Suverly (2004).

Data analysis

Data collected in the experiment were subjected to analysis of variance (ANOVA) using the GLM procedure of Statistical Analysis System (SAS 1999, version 6.12). Treatment means were separated using LSD test. The ANOVA model used for data analysis was:

Y_ij   =  µ + α_i + β_j + e_ij

Where Y_ij is response variable in i^th treatment and j^th block, µ is the overall mean, α_i is the i^th treatment effect, β_j is the j^th block effect and e_ij is random error.

Results and Discussion

Effect of supplement on feed and nutrient intake

Supplementation resulted in higher total DM intake, but did not have an effect  on the intake of the basal diet. Like that of the total DM intake, intakes of nutrients were generally greater for the supplemented animals compared to the ones fed VH alone. Intake of CP in the supplemented groups was around 10% of the total DM intake which is above the 7% limit for efficient utilization of feeds at the levelof the rumen (Ibrahim and Tibin 2003). Therefore, the improvement in intake of most of the nutrients in the supplemented groups can be justified by the relatively higher intake of CP. The lack of difference in intake of total nutrients between 300WB and WB-AA suggests that A. albida leaf can at least be a good substitute to wheat bran if available and price is feasible.

The average daily DM intake of the VH in the present study was comparable with the 581 g/day intake reported for chickpea but was lower than the 632 and 839 g/day intake noted for lentil and VH reported by Likawent et al (2004) for yearling Menz lambs. On the other hand intake of total DM for the non-supplemented group in the current study was relatively greater than the 477 g/day intake of hay (Mulu 2005) and the 567 g/day urea treated wheat straw (Getahun 2006) used as basal diet for sheep. This indicated that VH is a good replacer/ substitute for urea treated wheat straw as option for reducing livestock feed resource production costs. Tesfaye et al (2002) indicated the significant impact of wheat bran supplementation on intake of teff straw DM and OM, in agreement with results of the present study. Supplemented groups of this study had by far greater than the 274-522 g/day DM intake reported by Melese et al (2002) for the same breed of lambs supplemented with improved forage and/or concentrate.

Similar to the present findings, Ibrahim and Tibin (2003) indicated that replacing pods of A. albida at 0, 15, 30 and 45% for sorghum gain in total mixed ration resulted in significant improvement in daily feed intake. Moreover, Berhan and Getachew (2009) indicated a significant improvement in total DM, OM and CP intake when hay basal diet was supplemented with different forms of A. saligna which is inline with the present findings. Navas-Camacho et al (1993) indicated that inclusion of tree legumes up to 10% of the total ration as protein supplement increased total DM intake than at 34% level. In agreement with this, the 10.9% intake of A. albida leaf meal (300AA) resulted in higher (P < 0.05) total DM and OM intakes than when A. albida accounted 35.3% (WB-AA) of the total DM intake. The slight decline in total DM intake (Table 1) at high level of A. albida leaf meal inclusion (WB-AA) in the present study may probably due to an increment in tannin level with the leaf meal inclusion and its possible concomitant impact on nutrient digestibility and/or on rumen ecosystem. The pattern of lambs feed intake during the experimental period is presented in Figure 1 below.

The closeness of the intake curve for the supplemented groups in the above figure can also support the reason for the absence of significant difference among treatments during the trial. As all of the supplemented diets (300 g/day) were consumed completely (300WB through WB-AA), a clear gap between the supplemented and non-supplemented curve was observed.  

Effect on main carcass traits

Effect of different option of supplements on main carcass characteristics is presented in Table 2. The main carcass components were evaluated as slaughter weight, empty body weight, hot carcass weight, dressing percentage expressed as percent slaughter weight and empty body weight, fat thickness and rib eye area between the 12^th and the 13^th ribs of the left half of the carcass. Supplementation resulted in significantly improved (P < 0.05) main carcass components compared to non-supplemented group (Table 2). Except for dressing percentages 300AA was significantly higher (P < 0.05) than WB-AA in all main carcass components considered. Among the supplemented groups, no significant difference (P > 0.05) was observed on dressing percentage expressed as percent slaughter weight.

Positive effect of supplementation on slaughter weight, empty body weight and hot carcass weight was expected as better nutrition would improve growth rate and hence carcass yield (Tesfaye et al 2002; Ulfina et al 2004; Kashan et al 2005; Archimede et al 2008). Comparable to the present study Jemal et al (2004) reported a dressing percentage of 41.6-45.2 when Horro rams were supplemented with maize grain and molasses. Similarly, Ulfina et al (2004) reported dressing percentage values comparable to the present study, and noted more carcass weight and dressing percentage of growing ram lambs due to supplementation.

Fat thickness and rib eye muscle area between the 12^th and 13^th ribs were higher (P < 0.05) for the supplement groups as compared to the non-supplemented lambs. The third treatment option had greater (P < 0.05) fat thickness among the supplemented treatments. This may be due to the relatively better DM intake for animals in 300AA which is expected to increase nutrient utilization thereby increasing fat thickness (Ryan et al 2007).

 

No significant difference (P > 0.05) was observed among 300WB, 300AA and WB-AA for rib eye area but values for 300AA and WB-AA were higher than that for WB-AA. The positive correlation between rib eye muscle area and fat thickness with slaughter weight were also reported (Park et al 2002; Shadnoush et al 2004; Fernandes et al 2008) which will be impacted by nutrition. However, Chestnut (1994) and Kirton et al (1995) reported that plane of nutrition and breed to have little impact on rib eye muscle area which is not supported by the present study.

Effect on primal cuts

The five primal cuts were greater for the supplemented compared to the non-supplemented group (P < 0.05) inline with the significance observed in main carcass components (Table 3).

As it was true for the main carcass components, 300AA showed significantly higher (P < 0.05) primal cuts of rack, loin and leg than WB-AA. Obviously, slaughter weight determine the relative weight of each primal cuts (Karim et al 2007; Galvani et al 2008), which may explain the reason for differences between 300AA and WB-AA in such carcass parameters. However, 300WB, 300AA and WB-AA were not significantly different (P>0.05) for rack, loin and leg.