Voluntary feed intake and growth of broilers on Acacia angustissima leaf meal based starter and finisher diets

S Ncube, H Hamudikuwanda* and P T Saidi

University of Zimbabwe, Faculty of Agriculture, Department of Animal Science, Box 167, Mt. Pleasant, Harare, Zimbabwe
sharaincube7@gmail.com   ;   sncube@agric.uz.ac.zw
* Current address: ABSTCM UDCP, PO Box 35, Nyagatare, Rwanda

Abstract

One hundred and fifty unsexed Ross broiler chicks were used to determine voluntary feed intake and growth  of broiler chicks fed diets containing  Acacia angustissima leaf meal at levels of 0% (AA0) , 5% (AA5) and 10% (AA10) from day old to 7 weeks of age. The experiment was arranged in a completely randomized design with three treatments, each replicated five times with ten chicks per replicate. Weekly feed intake and body weight were measured and these were used to calculate feed conversion ratio.

Feed intake for birds on Acacia diets was greater (P < 0.05) than in the control group. Body weight gain of birds on Acacia diets was greater  (P < 0.05) than in the control group during Week 3. During Week 6 body weights for broilers on diet AA5 were lower (P < 0.05) than in the control and both AA5 and AA10 had lower (P < 0.05) body weight gains than the control during the seventh week. During the last 3 weeks, feed conversion rates for birds fed Acacia were poorer (P < 0.05) than in the control group. It was concluded that, Acacia angustissima based diet can be successfully incorporated in broiler starter at 10% inclusion level but continued use of the diets from the starter to finisher phase will compromise the final body weight.  

Keywords: Chicks, feed conversion, fodder trees, weight

Introduction

Among the challenges affecting the poultry production sector, feed availability remains an important challenge in most developing countries (Girma et al  2011) such that there is a continued scarcity and consequently high prices of the conventional protein and energy sources for livestock in the tropics. This has stimulated a lot of interest in the search for alternative sources of feeds, particularly for non-ruminants (Udedibie and Opara 1998). For sustainable poultry production systems in developing countries the approach should be to match production with available resources as opposed to comparing with benchmarks obtained in the western countries. This is because production conditions in many developing countries do not allow poultry to reach their full genetic potential. As such a wider range of ingredients should be used in poultry feed formulations some of which include legume tree species. While the potential of leguminous leaf meals has long been recognized, considerable research has concentrated on Leucena leucocephala.  More recent research has looked at other species including Gliricida sepium, Robina pseudoacacia, Cajanus cajun and Sesbania sesban (D’Mello 1995). Little research has been done using Acacia angustissima leaf meal in poultry diets. 

Acacia aungustsisima has been mainly recommended for ruminant feeding systems, but current research interest is in using the tree as protein sources for non-ruminant animals (Mashamaite et al  2009), due to its  ability to survive in harsh environments (D’Mello et al 1987).  It been relatively recently been widely propagated in agroforestry. It is a member of the Mimosaceae family and is thought to have originated in Belize, Central America (Dzowela 1994). Coupled to its high potential growth rate and nitrogen fixing capabilities (Preece and Brook  1999), Acacia aungustissima  tolerates occasional freezing conditions, withstands periods of drought, and responds well to regular cutting (Dzowela 1994). Acacia angustissima grows as a thornless shrub or small tree mostly 2-7 m high with a single short trunk. Biomass production can be up to 12.4 tonnes DM/ha depending on tree spacing and cutting back height after each harvest (Preece and Brook  1999). In a study by Hove et al  (2003) assessing the fodder trees planted by farmers in Zimbabwe, Acacia angustissima was grown by 78% of the famers, second to Leucena leucocephala with 88% of the farmers growing it, making it a locally available  resource.  The potential of Acacia aungustissima leaf meal as a broiler feed ingredient was assessed by Ncube et al  (2011) and they concluded that the leaf meal can be included in broiler finisher diets up to 15%, however there is need to test the continuous use of the leaf meal based diet from the starter to the finisher phase. Based on the known effects of A. angustissima in broiler finisher diets we hypothesize that A. angustissima can be included up to 10% in broiler starter and finisher diets without detrimental effects on feed intake and growth. Consistent with this hypothesis, the main objective of this study was to determine the growth and voluntary feed intake effect of feeding Acacia angustissima based diets from the starter to the finisher phase.

Materials and Methods

Study site

The study was conducted at Henderson Research Station, Mazowe, Zimbabwe (17º35’S, 30º58’E). The predominant vegetation is tree savanna or bush clump savanna with tall perennial grasses such as Hyparrhenia filipendula on red clay soils. Associated woody species include various Acacia species and Brachystegia spiciformis. The station is located on the watershed of Zimbabwe at an altitude of 1200 m. Rainfall is confined to summer (November through to March) and is moderately high (750 to 1000 mm). The mean annual temperature ranges from 20 to 30 ºC. 

Harvesting and preparation of A. angustissima leaf meal

The A. angustissima leaves were harvested from Domboshawa, 25 km northeast of Harare, at mid-maturity stage. Domboshawa is 31º13´E and 17º30´S and has an altitude of 1530 m. Soils at the site are sandy-loam in texture and largely of granitic origin. Mean monthly summer temperatures rise up to a maximum of 28 °C in October while mean monthly winter temperatures fall to a minimum of 5.5 °C in July. The predominant natural vegetation is tree savanna with Brachystegia and Hyparrhenia species as the dominant tree and grass species, respectively. Leaves were harvested by cutting branches at least 1 m above the ground to allow for re-growth. After cutting, the leaves were pruned from the branches, air-dried in a shed to less than 13% moisture content. The dried leaves were then ground to pass through a 1mm sieve using a hammer mill and proximate analysis was carried out to determine chemical composition of the leaf meal (Table 1). The ground A. angustissima leaf meal (leaf meal) was then incorporated in starter and finisher diets at 0, 5 and 10 % of the total diet by weight (Table 2 and 3).

Experimental design and procedure

One hundred and fifty unsexed Ross broiler chicks of mean body weight 36.87 ± 1.51 g were randomly allocated to 15 groups consisting of 10 birds per group. The groups were randomly allocated to 3 iso-nitrogenous and iso-energetic diets, 0 % leaf meal (AA0), 5% leaf meal (AA5), and 10% leaf meal (AA10) (Table 3 and 4) in a completely randomized design. The birds were group-fed ad libitum and water was freely available. The starter diets were used from day old up to three weeks of age and the finisher diets were given from the beginning of the fourth week up to the seventh week of age when birds were slaughtered.

Measurements and statistical analysis

Weekly replicate (group) bodyweights and feed intake were recorded in order to calculate feed conversion ratio (feed conversion). The effect of dietary treatments on feed intake and bodyweights was determined by repeated measures ANOVA using the PROC MIXED procedure of SAS (1998). Pairs of means were compared using the Predicted Difference (PDiff) statistic of SAS (1998).

Results

Feed intake

There was an interaction  between dietary treatment and age of birds on feed intake (P < 0.05).  For the first two weeks of the trial period, feed intake did not differ (P > 0.05) across treatments (Table 4). From the end of the starter period (Week 3) to the end of the trial, feed intake for the broilers on Acacia-based diets was higher (P < 0.05) than for the control group.

Weekly body weights

Dietary treatment and age (week) of birds had an interaction (P < 0.05) on body weights. During the third week of the trial period (which was the end of the starter period), body weights of birds on the AA5 and AA10 were higher (P < 0.05) (Figure 1) than those in the AA0 group.  During Week 6, birds in the AA0 group weighed more (P > 0.05) than those on AA10. However, during the last week of the trial the AA0 birds weighed more (P < 0.05) than those in both Acacia treatments (Figure1).

Figure 1: Growth curves of broilers on different levels of Acacia aungustisima

Feed conversion ratio

There was an interaction (P < 0.05) between diet and age of birds on feed conversion.  For the first four weeks of the experiment, feed conversion for all treatment groups were not different (P > 0.05). During Weeks 5 and 6, feed conversion for the AA0 diet was less (P < 0.05) than that for Diets AA5 and AA10 (Table 5).  By the last week of the experiment, feed conversion for the AA0 diet was lower (P < 0.05) than those for Diets AA5 and AA10 while that for Diet AA5 was lower (P < 0.05) than feed conversion for Diet AA10.

Discussion

Feed intake was the same for all treatments during the first two weeks. For the last five weeks birds on the leaf meal based diets had higher feed intake than that for the control diet probably because the crude fiber content of the Acacia based diets (Tables 3 and 4) could have reduced the release of energy and other nutrients from the diets, consequently more feed was required to provide adequate energy for growth.  According to Teguia and Beynen (2005) high fibre levels in poultry diets lead to poor digestibility of the diets and are associated with a higher feed intake as was the case with the Acacia based diets. In another study by Hetland and Svihus (2001), feed consumption increased significantly when fiber level was increased through the addition of oat hulls in the diet of broilers.    

By the end of the starter period, the birds on Acacia based diets weighed more. This is in agreement with Jimenez-Moreno et al  (2010) who reported that fiber inclusion in poultry diets improved body weight gain during the starter period, but the beneficial effects were less evident after this age.  The voluntary feed intake during the starter period could easily compensate for the nutrient requirements during the starter phase. 

By the end of the finisher phase even though the birds on diet AA5 and AA10 consumed more than those on the AA0 diet, birds on the AA0 diet performed better. Ferket and Gernat (2006) said that for meat type poultry the amount of feed consumed is associated with growth performance, in this study, this was not the case in the finisher diets as birds needed more energy for growth during this stage of growth. As noted by Jimenez-Moreno et al  (2010) the dietary fiber in the acacia based diets could have acted  as a diluent in the diets, thus  feed intakes for groups on Acacia based diets could meet the protein and low energy requirements during the starter phase. However the diets failed to satisfy the energy requirements during the last week of finisher phase for Diet AA5 and the last two weeks for Diet AA10. This confirms that energy shortage became more critical as the content of Acacia angustissima increased and at later stages of the finisher period.  These results also support what D’Mello et al (1987) concluded with L. leucocephala leaf meal. The authors concluded that although the feed intake of broilers on a diet containing 10% leaf meal of L. leucocephala leaf meal was similar to the control group, the body weight gain of birds was lower than in the control group. 

Feed conversion for Acacia-based diets during the starter period was the same as the control diet. Later, the Acacia based diets became less efficient than the control diets. This also agrees with the report by Ash et al (1992) who observed that leaf meals from Sesbania sesban and Sesbania grandiflora depressed feed utilization efficiency in chickens. This could have been due to tannins and/or crude fiber content of the diets compared to the control diets. Tannins are known to bind to nutrients and enzymes of digestion thus reducing the release of nutrients (Fleury 2004), and consequently reducing efficiency of utilization of feed.

Conclusion

• Based on the voluntary feed intake, weekly weights of birds and feed conversion, Acacia leaf meal can be included up to 10 % level during the starter period, however prolonged use of the leaf meal throughout the growth period compromises final weights and feed conversion rate.

References

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Received 17 April 2012; Accepted 26 June 2012; Published 1 August 2012

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