Evaluation of the effects of Spinosum Seaweed on the growth performance of broiler chickens: A case study in Zanzibar

F A Kessi and L C Mwaipopo¹

Ministry of Agriculture, Irrigation, Natural Resources and Livestock
kessifaki@yahoo.com
Department of livestock Development (DLD), P O Box 159, Zanzibar
¹ Tanzania Livestock Research Institute (TALIRI Uyole) P O Box 6191, Mbeya, Tanzania

Abstract

An experiment was conducted at the Poultry unit of Kizimbani Agriculture Training Institute in Zanzibar to evaluate the effect of seaweed as mineral source in the growth performance of broiler chickens Two hundred and forty (240) broiler chickens were fed four dietary treatments (Sw0, Sw0.9, Sw1.5 and Sw2), containing 0, 0.9, 1.5 and 2% seaweeds. Feed intake was measured daily while live weight was measured on a weekly basis. Proximate and mineral analysis of seaweed, individual feed ingredients and experimental diets were determined. The results showed that CP was highest (21.84%) in Sw2 and lowest (17.66%) in Sw0.9. Highest energy was observed in Sw1.5 (3019.55 kcal/kg DM) and lowest (3007.35 kcal/kg DM) in Sw0. TDMI per bird was lowest (4.0kg) in Sw0 and highest (4.6kg) in Sw1.5. Proximate analysis of seaweed showed high ash content (47.65%) low levels of CP (5.42%) and CF (3.29%). Mineral analysis in seaweed showed that it is rich in both macro and micro elements and low in amino acids. Differences for FCR between treatments were insignificant (р > 0.05). Body weight was difference (р < 0.05) higher in Sw1.5 and lower for Sw2. Final body weight was lower in Sw0 (2229.4g) and high in Sw1.5 (2481.9g).It is concluded from the current study that, seaweed inclusion at 1.5% had significant positive effects on growth rate and increased weight of broiler chickens. In view of this, poultry farmers should be educated on the importance of using seaweed as feed ingredient or feed additive in their feed formulation.

Keywords: experimental diets, growth rate, feed conversion rate, feed ingredients, poultry

Introduction

Poultry industry is very important in our country since it generates income, provides employment and contributes in poverty reduction. Statistics available indicate that, Tanzania has 83.28 million of which 38.77 million local and 44.51 exotic chickens (MLFD, 2021). However, the industry is faced with many challenges as far as poultry production is concerned, the crucial one being feed component. Feed is a major cost in the industry and normally accounts for about 70-80% of the entire production expenditure (Ademola and Farinu, 2006).

Different feed ingredients are used in formulating poultry diets. Studies have shown that, the inclusion levels of each feed ingredient vary with type of ingredient. Maize meal is the commonest (40%), maize bran (25%), fish meal (5%) and oil seed cakes like sunflower seed cake, and cotton seed cakes (15%) (Chiba, 2009; Afolayan et al 2012). The inclusion level of mineral premix in broiler diets is 0.25%, so in every 1 ton of feed the inclusion of mineral premix is about 2.5kgs (Biotech, 2014). A micronutrient is defined as a substance needed only in small amounts in the diet which enables the animal to carry out normal body functions (Woodside et al., 2005). Although the amount for premixes seems to be very small compared to other ingredients during feed formulation, they play a significant role as far as animal performance is concerned. Micronutrients facilitate absorption of nutrients in the system and synthesis of body enzymes. Vitamin-mineral premix is the mixture of vitamin and minerals which is added to the formulated diet to meet the requirements of vitamins and minerals that are deficient in the formulated diet (Asaduzzaman et al 2005). Inclusion of vitamin-mineral premix in the compounded diet has become indispensable practice since feed ingredients don’t contain all essential vitamins and minerals at the right amount needed by the chicken. Critical vitamins include choline, folic acid, pantothenic acid, pyridoxine, riboflavin, Vit-A, Vit-D₃ and Vit-E whereas minerals include Calcium, Phosphorus, Copper, Iodine, Iron, Manganese, Sodium and Zinc these components should be adequately supplied in the diet (Asaduzzaman et al 2005).

It is well known that trace elements (Co, Cu, Fe, I, Mn, Mo, Se, and Zn), and among others are vital for the normal functioning of most biochemical processes in the body. They are part of several enzymes and coordinate many biological processes as such they are essential for maintaining animal health and productivity (López-Alonso, 2012). Optimal nutrition with adequate trace elements level in the diet, guarantee proper performance and functions of living organisms, among which the most important are structural, physiological, catalytic and regulatory (Suttle, 2010).

Synthetic mineral premixes are commonly used in poultry feed formulation, however, local feed formulators, tend to apply very little amount or sometimes, they don’t put mineral premix in the diet, because of unreliable availability, high cost and poor quality. Consequently, feed manufacturers produce substandard poultry diets (DLP, 2012). This gap can be reduced by using natural substances believed to contain high levels of macro and micro elements, vitamins, protein and essential amino-acids such as seaweed (Rimber, 2007). Seaweed is readily available in Zanzibar at village level and is cheaper when compared with commercial premixes. Seaweeds are microscopic algae which are commonly grown in the coastal areas of many countries in the world and it is commonly used as human food in some countries (Jacquine, 2014). It is a multipurpose product which is used in various industries, including fertilizer production, skin care products, cosmetics, soap making, also as an important active ingredient in some medicine and animal feeds and other food processed products (Msuya, 2013). It is estimated that, there are about 10 000 kinds of seaweeds in the world, which fall into three main groups characterized by their colour i.e. green, brown and red. The pigmentation that these groups have in their cells is the one that make big differences between them (Wei et al 2013). Green seaweeds mainly have chlorophyll a green pigment that captures sunlight for photosynthesis, while brown and red seaweeds also contain chlorophyll, but their cells also have other pigments that mask the green colour (David, 2009). Red and brown seaweeds are used in the production of various products that include hydrocolloids, alginate, gelling agent, agar and carrageenan as thickening and stabilizing food agent such as ice cream and chocolate in milk (Jaspars and Folmer, 2013).

In Zanzibar, seaweed is a famous crop which is grown along the coastal area of many villages, its production is dominated by women where it provides employment and income. In some villages dried seaweed is processed to get powder which is used for soap making, preparation of confectioneries, as well as salad making. Seaweed production in Zanzibar has been increasing annually from 9261 tons in 2003 to 11 177 tons in 2008 (Economic Survey, 2008). A large proportion of produced seaweed is sold in the local market within the islands but eventually it is exported, and only a small amount is processed. Currently, it is estimated that, approximately 1 million tons of fresh/wet seaweeds are harvested worldwide and extracted to produce about 55 000 tons of hydrocolloids, value at almost US$ 600million (McHugh, 2003). Use of seaweeds as food has strong root in Asian countries such as China, Japan and Republic of Korea, but has now also spread to North America, South America and Europe (McHugh, 2003). Seaweeds has also been used as a feed ingredient in animal diets and studies to investigate the substitution of seaweeds in broiler diets found no adverse effects on performance. Addition of 4% seaweed in the chicken’s basal diet led to increased body weight gain (Abudabos et al 2013). Despite these numerous studies there is still limited information on the use of seaweed as a mineral source in broiler diets in Zanzibar and Tanzania as a whole. Thus, the objective of the current study was to evaluate the effect of using the seaweed (Spinosum) as a mineral source in broiler diets.

Materials and methods

Area of experiment study

The study was conducted at Kizimbani Agriculture Training Institute in Zanzibar (KATI) about 5 kilometers from Zanzibar Town. The Institute is situated at latitude 6⁰ South, longitude 39⁰ East and 20 m above sea level. The area receives an average rainfall of 1564 mm/annum and annual average temperature of 25.7⁰C.

Experimental diets and preparations

Dried Seaweed was obtained at the selling point i.e Zanzibar East Africa Company (ZANEA), from Unguja Island. The obtained seaweed was sun dried one day before grinding after which it was well packed in polythene bags and stored at room temperature. Other feed ingredients including maize bran, sunflower meal, fish meal, maize meal, broiler premix, DL- Methionine, salt, limestone and other were purchased from Agro vet shops and were then stored at room temperature.

The chemical composition of both seaweed meal and other feed ingredients were determined at the DASP Laboratory for Proximate analysis and at Soil Science Laboratory for minerals analysis before the diets were compounded. Four dietary treatments (Sw0, Sw0.9, Sw1.5 and Sw2) were locally compounded and their chemical and minerals compositions were determined, using AOAC (1995). The dietary treatments contained different levels of seaweed as mineral premix, Treatment one (Sw0) no seaweed (0% seaweed) it contained (0.25% commercial premix as control), Treatment two (Sw0.9) had 0.9% seaweed, Treatment three (Sw1.5) 1.5% seaweed and Treatment four (Sw2) contained 2% seaweed. All experimental diets were thoroughly mixed, well packed in 50kg bag, and marked accordingly for easy identification i.e. Sw0, Sw0.9, Sw1.5 and Sw2, and were then stored at room temperature ready for feeding.

The estimated Crude Protein (CP) and Metabolizable Energy (ME) of each ingredient in the diet was calculated by taking the estimated values of Crude Protein and Metabolizable Energy of the ingredients multiplied by the inclusion level in the diet. Calculated CP and ME of each experimental diet were obtained by adding calculated CP and energy of all ingredients present in the diet. Table I shows physical composition of the experimental diets and their calculated CP and energy.

Experimental design and birds’ management

The experiment involved the evaluation of the effect of seaweed on growth performance and carcass quality of broilers birds. A total of two hundred and forty (240), day old broiler chicks were purchased from “Thuirachicks and Company” in Zanzibar and were brooded together for one week at Kizimbani poultry unit. Before placing chicks in the brooder room the initial weight of each chick was taken and recorded, and chicks were provided with “Vitalyte” (feed additive containing some minerals, electrolyte and essential amino-acids) during the first 5 days. During the preliminary period i.e. first week of age brooding period all chicks were offered a commercial diet ad libitum purchased from one Agro vet shop in Zanzibar. At the same time the brooder was provided with drinkers to meet the requirement of chicks as far as water was concerned. The inside temperature was maintained at 35^ºC, the electric bulbs were well placed in the brooder to ensure the constant supply of the required heat.

After one week, the chicks were assigned to their respective treatments and each treatment was replicated four times with fifteen (15) chicks in each replicate making total of (240 chicks). The rearing rooms floor were covered with wood shavings and feeding and drinking equipment’s were put in place. During the growing period day light was used as source of light during day time whereas electrical bulbs were used at night. All chicks were vaccinated against Newcastle disease on day seven, and on day twelve they were vaccinated against Infectious Bursa disease and it was repeated at day 19. At four weeks of age all chicks were provided with amprolium (ant-coccidios is) as prophylaxis for 3 days.

Experimental procedure and data collection

The broiler chick’s performance was evaluated by using change in body weight (growth rate), feed intake and feed conversion ratio.

Growth rate

As mentioned before, all chicks were initially weighed on individual basis and their weights were recorded before being introduced in the brooding room. During this time chicks were wing tagged for easy identification. Weighing of chicks was done on a weekly basis to get weekly weight of each bird. Weight difference between t₁ and t₂ was used to calculate weight gain as shown in formula.

The Growth rate was calculated as follows:

Where by:

W = average daily weight gain g/d (growth rate)

Wt₁ = Initial live weight

Wt₂ = Final live weight

T₁ = Time 1 (day zero)

T₂= Number of days at disposal

Feed intake and feed conversion ratio

Feed intake was determined by weighing the amount of feed offered and feed refusal in each pen (replicate) on a daily basis. Feed intake per pen was obtained by calculating the difference between the total weight of feed given and weight of the refusal feed (left over feed). However, Feed conversion ratio (FCR) was obtained by dividing the total feed intake with total weight gain of all birds in each pen as shown in formula.

Feed intake was obtained by using formula

Feed intake (FI) = Feed offered – Feed refusal

Feed Conversion ratio (FCR) = Feed intake/Average daily gain

Chemical analysis of individual feedstuff and dietary treatments

Samples of individual feed ingredient and experimental diets were analysed for their content of DM, CP, CF, EE, ME, AA, ASH, MC, Ca, P, Fe, Mn, etc; according to AOAC (2005) and Atomic Absorption Spectrophotometer (for macr0 and micro elements analysis)

Data processing

Collected data from each treatment were entered into the computer data base (excel sheet) ready for statistical analysis (SAS, 2000).

Statistical analysis

The obtained data were analyzed using 2 models. Dietary treatments were regarded as independent variables while weight gain, feed intake, and feed conversion ratio (FCR) were dependent variables. The data were analyzed by using the General Linear Model (LGM) procedure of (SAS, 2000). The statistical models used are shown below

Yijk =µ+ Swij+(X₂ —X₁) + eijk

Where; Yijk = Effect of the i^th dietary treatments on the j ^th bird in k^th period

µ =General mean effect

Swij = Effect of i^th dietary treatment on j^th birds

X₂ = Final group mean weight after k^th period

X₁ = Initial group mean

Eijk = Random error.

Analysis of feed intake

Yij =µ+ Swi+ßj + eij

Where; Yij = expected observation in each experimental unit

µ = General mean for all observation

Swi = effect of i^th treatment in the j^th replication

ßij = effect of j^th replication within treatment i^th

eij = experimental random error.

Results

General condition of the birds

The results were gathered based on real situation which took place at the experimental site, Kizimbani Agriculture Training Institute. Generally all chicks were in good health and there was no death throughout the experimental period. This showed that, the survival of the birds and health status were not affected by the addition of the seaweeds in the diets of broilers.

Chemical composition of feed ingredients used in compounding experimental diets

The chemical composition of feedstuffs used in the preparation of the experimental diets are summarized in Table 2, CP content was highest in fish meal (47.55%) and lowest in seaweed (5.42%). Highest CF (26.33%) was noted in sunflower meal whereas it was lowest in fish meal (0.93%). EE was higher in maize bran (14.73%) and lower in seaweed (0.3%) whereas DM was almost similar in most ingredients but was high (97.68%) in fish meal and lower (94.59%) in the seaweed. lysine was highest (4.53%) for fish meal and lowest in seaweed (0.69%). tryptophan was highest (0.7%) in maize bran and lowest (0.03) in maize meal. No methionine/cystine was detected in seaweed, however the highest was 2.13% in fish meal and lowest was 0.12% in maize meal. Ash content was higher in seaweed 47.65% and lowest 1.35% in maize meal.

Chemical composition of the feed ingredient (Seaweed spinosum)

The results for chemical composition (mineral composition) of the tested feed ingredient (seaweed) as mineral premix is presented in Table 3.

Chemical Composition of the Treatments Compounded diet for Broilers

The chemical composition of compounded diets is shown in Table 4. There was no significant difference for Dry matter (DM) content observed between the experimental diets. Crude protein was similar for Sw0 and Sw2 and was slightly lower for Sw0.9 and Sw1.5. The level of Ether Extract (EE) was similar for Sw0, Sw0.9 and Sw2 treatments but slightly lower for Sw1.5. Additionally, Sw0.9 and Sw2 had higher crude fibre (CF) compared to Sw0 and Sw1.5. An increase in moisture content with increasing seaweed inclusion was noted.

Effect of dietary treatments on growth performance

Body weight

Table 5 shows the least square means for body weight of broiler chicken fed the experimental diets. Differ (р < 0.05) in growth performance of broiler chicken between the dietary treatments were noted. Body weight was higher for Sw1.5 and Sw2, lower for Sw0 throughout the experimental period. The inclusion of seaweed resulted in increased body weight. However, minor differences in weight gain between Sw1.5 and Sw2 were also noted.

Effect of dietary treatments on growth rate of broilers

The effect of dietary treatments on weight gain in broilers chickens is shown in Table 6. The results showed progressive increase in weight from week 2 to week 7. Weight in Sw1.5 and Sw2 at the second week of age (2wk) was the effect of experimental diets, since chickens were subjected to the experimental diets from day 7 of age. Significant differences in live weight gain throughout the experimental period between the dietary treatments were noted. Sw0 (control) had higher weight gain at week 7 compared to the other experimental treatments (р < 0.5). However, Sw0 compared to Sw1.5 and Sw2 had insignificant weight gain (р > 0.05).

Effect of dietary treatment on dry matter intake

The least square means on DM intake are presented in Table 7. An increase in Dry matter (DM) intake with age of chickens was noted in the dietary treatments. Throughout the experimental period intake was highest for Sw1.5 but inconsistent variations were observed between the other dietary treatments.

Effect of dietary treatment on average daily gain, dry matter intake per bird and feed

conversion rate

The least square means on average daily gain (ADG), dry matter intake per bird (DMINT/B) and feed conversion ratio (FCR) are presented in Table 8. The effect of dietary treatments on average daily gain was insignificant (р > 0.05) although minor differences were noted whereby Sw1.5 was a higher, followed by Sw2 and Sw0.9 and the lowest was Sw0. A similar trend was noted for dry matter intake per bird. No significant difference between dietary treatments was observed for overall feed conversion rate. Results from regression equations in Figure 1 and 2 shows clearly very minor degree of response in the change of ADG and FCR, the latter which is very important sign to show the efficiency of feed utilization and are of biological and economic important.

Figure 1. Regression equation showing response of treatment (seaweed %) on Average Daily Gain	Figure 2. Regression equation showing response of treatment (seaweed %) on Feed Conversion Ratio

Effect of Dietary Treatments on Final weight gain on Broiler Chicken

Final body weight was affected by inclusion of seaweed in the diet whereby a higher weight was noted for Sw1.5 and Sw2 and was slightly lower for Sw0 and Sw0.9.

Photo 1- 2. Show broiler chicken fed seaweed for seven weeks at different ages

Discussion

Chemical composition of feed ingredients used in the experimental diet

With the exception of seaweed as one of the feed ingredients used in the preparation of diet, which has already been explained above, other chemical compositions of feed ingredients used, i.e. Maize meal, Maize bran, Sunflower Cake, Fish meal, some of the compositions were within the range as reported in other studies (Mlay et al 2005, Olugbemi et al 2010; Kakengi et al 2007).

The CF content of 26.33 % and 10.15 % for sunflower and maize bran respectively obtained in the present were significantly different from values of 59.1% sunflower and 31.9% maize bran obtained by Mlay et al (2005). These differences could be due to processing methods such as decortication/dehulling before extracting oil from sunflower. Likewise chemical compositions of fish meal reported by Kakengi et al (2007) was different from the one obtained in present study.

The present study obtained the chemical compositions of fish meal, as 47.55% CP; 0.925% CF; 2.68% EE; 97.68% DM; 46.16% ASH, while reported by Kakengi et al (2007) were 56.6% CP; 1.4% CF; 9.95% EE; 87.9% DM; 30.3% ASH. The variations in chemical composition of fish meal, could be due to the size and origin of the fish, (i.e. sea or fresh water) since salinity of the water plays a significant role in mineral composition of fish, the issue of quality parameters such as muscle composition, fat deposition, muscle fat acid composition, type of fish, either cultured or wild can also affect content (Grigorakis et al 2002).

Chemical composition Spinosum seaweed

The chemical compositions particularly minerals of the seaweed (spinosum) obtained in the present study were within the range reported in other studies (Norziah and Cheng 1999; Rupérez 2002). However, variations for trace elements from the same studies were noted. The variations in the nutrient composition of the seaweed in the present study compared to findings reported in other studies might be due to differences in varieties, growing condition, sea salinity, geographical area and method used for harvesting and processing (Marinho-Soriano et al 2006; Chan et al 1997).

The level of 0.69% for lysine obtained in the present study was significantly lower than values reported elsewhere ranging from 1.13 to 7.0mg/100g. The reasons for these differences could be due to factors such as protein content of the seaweed species, time of harvesting as it is believed that during spring protein content of the seaweed is higher than in the summer and autumn (Khairy and El-Shafay, 2013). On the other hand the presence of tryptophan and lack of methionine/cystine observed in current study was contrary to the findings of other studies whereby substantial levels of methionine/cystine were detected ranging from 0.39% to 5.85 mg/100 g (E-L Deek and Brika, 2009; Ito and Hori,1989). The underlying cause for these differences is unclear although it could be varietal differences and analytical errors.

Most of the analysed chemical components in the present study were within the range Manivannan et al. (2009); Narasimman (2012); Manivannan et al (2008) and Murugaiyan et al (2012). However, for crude protein (CP %) wide variations have been noted ranging from 9.65 to 31.07% CP, this could be a reflection of differences in seaweed varieties. Carbohydrate (NFE) level of 56.66% obtained in the present study was higher than 43.33% reported by the above researchers. The variations in chemical composition in seaweed might be due to various factors that include species, time of harvesting, geographical area where seaweed is cultivated, and salinity of the sea (Marinho-Soriano et al 2006). Additionally, it is also believed that the drying methods can be among the factors contributing in minerals leakage, such as sun-drying which might cause leaching due to long exposure time to the sun (Chan et al 1997).

Chemical composition of the broiler dietary treatments

The chemical compositions of the compounded dietary treatments were mostly a reflection of individual feed ingredients used. The experimental diets were initially planned to contain 19% CP for all the dietary treatments with the exception of minor differences at Sw1.5 and Sw2 where it was 19.30% CP (T3) and 19.25% CP (Sw2). However, the analysed results of the compounded diet showed that CP % content was higher and lower in some dietary treatments from the original plan. The variation in CP content of the experimental diets was unexpected and reasons for this are unclear, although it could be due to mixing procedure of the dietary feeds, since it was done manually. On the other hand, the energy of the compounded diets was comparable to the calculated content and was within the range (Pantjawidjaja, 2011).

The variations between calculated and actual composition of the diets might be due to existing variation in feed composition, improper sampling for laboratory analysis or improper mixing since this was done manually. The differences in nutritive value of feed ingredients between published and actual are mostly caused by several factors that include plant variety, stage of maturity at harvesting, processing and storage condition (Tiwari et al 2006; Laswai et al 2002; Gerasimenko et al 2010). This feature shows the importance of analyzing feed components before feed formulation is done. The prolonged exposure to high temperature of tropical feedstuffs also has a negative effect on the nutritive value and therefore affecting the chemical composition of compounded diets. It has also been noted that most of the commercial broiler diets in tropical countries contain low CP (16 - 18%) probably due to the nature of the feed ingredients that are used. (Widyaratne and Drew, 2011). However, studies have shown that these levels of CP to some extent support optimal broiler growth, Azarnik et al (2010) and Rostagno et al (2007) reported that this could be due to high environmental temperature condition.

Effect of dietary treatments on growth rate of broilers

The mean weight gain of birds across the dietary treatments from the second to seventh week presented in Table 12, showed no significant difference between dietary treatments. The increased weight gain observed in the present study was an indication that, the quality and intake of dry matter for the dietary treatments was good. The weight gains obtained in present study were within the range reported by Hernández et al (2013). The observed trend for increased weight gain especially in the second week and fourth week of age was associated with increased dry matter intake. On other hand the observed decline in live weight gain during week 6 could be a reflection of normal growth pattern of animal. The rate of growth of animal accelerate during the early stages of growth and thereafter decline as mature weight is approached (McDonald et al 2010).

Effect of dietary treatment on dry matter intake

The present study showed that, feed intake of the broiler chicken at six weeks of age was between 3.2 to 3.7 kg. This value was similar to the values reported by Sundu and Dingle (2008) for the same age of broilers which ranged between 3.1 to 3.7 kg of feed per bird. The reason of this might be due to low CF and EE of the experimental diets which accelerated feed intake and digestion of the feed ingredient. The total feed intake on dry matter basis for the four dietary treatments ranging between 4.1 to 4.7 kg per bird for the whole experimental period and was within acceptable levels reported elsewhere (Yu et al 1990).

The results of the present study showed increases in feed intake during the fourth, fifth and sixth weeks, in comparison with the second and third week. This was probably due to the acclimatization of the broiler chicks to the experimental diets containing seaweed. The lowest feed intake for Sw0 on dry matter basis in relation with other dietary treatment (Sw0.9, Sw1.5 and Sw2), as shown in Table 13 from the second up to seventh week of age was an indication of nutrient adequacy but this also showed that diets supplemented with seaweed (as premix) stimulated appetite of broiler chickens. However, high overall dry matter intake including the control diet, was a reflection of good energy balance. Since it is understood that, amongst dietary factors affecting feed intake is the concentration of energy in the diet (Eekeren et al 2006).

Effect of dietary treatments on average daily weight gain, dry matter intake per bird and feed conversion ratio

The gradual increase of average weight gains of birds with increasing seaweed in the diet compared to those fed the control diet was evidence that, seaweed inclusion did not affect feed intake and general performance. It was also speculated that seaweed might have a stimulatory effect for feed intake due to the presence of appreciable levels of sodium chloride. This further illustrated that the dietary treatments with seaweed inclusion (as mineral source), were better than the control diet. However, the difference observed between Sw1.5 and Sw2 indicated that the inclusion of 1.5% (seaweed spinosum) in combination with some low levels of commercial premix gave best results. However, in order to reach a valid conclusion further research is needed.

Overall feed conversion ratio of the present study showed that there was no significant difference in all dietary treatments. Values for FCR mainly depend on two factors, the growth rate and feed intake and both are mostly affected by the quality of the diet. High FCR is obtained when feed intake is high and growth rate is low as would happen with an unbalanced diet (Simol et al 2012). The study of Magala et al (2012) observed that higher dietary energy with low protein resulted into slow growth of the chicken and hence decreased weight gain. This was probably due to a decrease in intake of other nutrients such as amino acids which are essential for grow th in broiler chickens. The results shows very little response on ADG and FCR which suggest there are probability that feed is not economic to feed therefore there are need to evaluate cost benefit analysis on feeding seaweed inclusion in the broiler feeds.

Effect of dietary treatment on final weight gain

The final means of live weight of broiler birds across the experimental diets at seven week of age ranged from 2.2 in Sw0 and 2.5kg in Sw2. The higher final weight observed in seaweed based diets (Sw1.5 and Sw2) in the present study was probably due to physical properties of seaweed such as high solubility, high nitrogen free extract and low antinutritional factors (Rioux et al 2007; AL- Harthi and EL-Deek, 2012). Another reason could be that the level of seaweed in the diets of the present study was within the acceptable limit, since it is believed that seaweed promote growth rate up to 5%, when the level is beyond 5% decline in growth rate is noted, possibly due to increased level of antinutritional factors contained in some seaweed species (Zaki, 1994).

The results of the current study concur with the findings by El-Deek and Brikaa, (2009), who reported weight of 2.3kg of broiler birds during disposal. The minor differences in final body weight between findings of the present study and other studies was probably due to individual variation such observe since male animal have higher live weight gain and carcass weight compared to female (Broadbent et al 1981). Similar results of increasing body weight and other carcass components were also reported by El-Deek and Brikaa (2009) when inclusion of seaweed in pelleted diets result ed into better feed efficiency.

Conclusions

• The increase of seaweed level in the broiler diet moderately increased overall live body weight, feed intake and feed conversion ratio.
  
  
• Seaweed inclusion in the diet had effect on cumulative weight gain, average daily gain, and weekly weight gain and dry matter intake per bird.
  
  
• Seaweed inclusion at 1.5 % (Sw1.5) had overall positive effect on all dependent variables i.e. dietary treatments which contained 1.5 % can be considered as optimum in broiler diets.
  
  
• There is a small response on the value of ADG and FCR which suggest that the feeding seaweed in the broiler diet is not economic.

Acknowledgements

This research was supported by grants from the Tanzania Commission for Science and Technology (COSTEC).

Conflict of Interest

Authors declare that they do not have any conflict of interest regarding the material discussed in this paper

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