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Print version ISSN 0102-0935
Arq. Bras. Med. Vet. Zootec. vol.64 no.4 Belo Horizonte Aug. 2012
ANIMAL SCIENCE AND TECHNOLOGY AND INSPECTION OF ANIMAL PRODUCTS
Effects of cashew nut shell liquid (CNSL) on the performance of broiler chickens
Efeitos do líquido da casca da castanha de caju (LCC) sobre o desempenho de frangos de corte
C.A.A. LópezI; K.R.S. LimaII; M C. MannoII; F.B. TavaresII; D.L. Fernandes NetoII; M.L.C. JesusII; M.A.O. VianaII; L.A.B. FonsecaII
IRegional Scientific Development - CNPq/SEDECT/UFRA - Belém, PA
IIUniversidade Federal Rural da Amazônia - Belém, PA
The effects of cashew nut shell liquid (CNSL) on growth performance, carcass yield, relative weight of internal organs and microbiology of digestive tract of broiler chickens were investigated. Five hundred and forty male broiler chicks at one day of age were arranged in a completely randomized design with six treatments and six repetitions with 15 broiler chicks each. The treatments were: control (T1 - without growth promoter virginiamycin and CNSL); inclusion levels of 0.10mL (T2), 0.20mL (T3), 0.30mL (T4) and 0.40mL (T5) of CNSL/kg of feed; and commercial promoter virginiamycin (T6). At 21 and 40 days of age, body weight, feed intake, feed conversion and viability of birds were similar in all treatments. Carcass yield was higher in the treatment with the growth promoter when compared to the control treatment. There was a linear increase in carcass yield when the level of CNSL was increased in the diet. The relative weight of the intestine was lower in the treatment containing virginiamycin when compared to the treatment without the inclusion of additives. The relative weight of the intestines decreased when the levels of inclusion of CNSL were increased. There was a gradual reduction of Escherichia coli concentration reaching the lowest number on the CNSL level of 0.30mL/kg. It was concluded that CNSL showed similar performance and slaughter yield as the growth promoter and reduced the concentration of Escherichia coli in the intestinal contents.
Keywords: feeding, feed conversion, nutrition, vegetable extract
Um estudo foi conduzido para investigar os efeitos do líquido da casca da castanha de caju (LCC) sobre o desempenho, o rendimento de carcaça, o peso relativo dos órgãos internos e a microbiologia do trato digestivo de frangos de corte. Foram utilizados 540 pintos machos de um dia de idade, distribuídos num delineamento inteiramente casualizado, com seis tratamentos e seis repetições de 15 aves cada. Os tratamentos consistiram em: controle (T1 - sem promotor comercial e sem LCC), níveis de inclusão de 0,10mL (T2), 0,20mL (T3), 0,30mL (T4) e 0,40mL (T5) de LCC/kg de ração e T6 (promotor comercial - virginiamicina). Aos 21 e 40 dias de idade, o peso corporal, o consumo de ração, a conversão alimentar e a viabilidade das aves foram semelhantes em todos os tratamentos. O rendimento de carcaça foi superior no tratamento com promotor de crescimento em relação ao tratamento-controle. Ocorreu uma resposta linear de incremento no rendimento de carcaça com o aumento do nível de LCC na dieta. O peso relativo dos intestinos foi menor no tratamento com virginiamicina em relação ao tratamento-controle. O peso relativo dos intestinos diminuiu com o aumento do nível de inclusão do LCC. Houve uma redução gradual da concentração de Escherichia coli, cuja menor concentração atingiu o nível de 0,30mL/kg. Conclui-se que o LCC mostrou desempenho e rendimento de abate semelhantes ao promotor de crescimento e reduziu a concentração de Escherichia Coli no conteúdo intestinal.
Palavras-chave: alimentação, conversão alimentar, nutrição, extrato vegetal
The most widely used additives in poultry feed are the antibiotic growth promoters (AGP), which act in the intestine of birds reducing the population of certain types of commensal bacteria, promoting better growth performance. However, the use of AGP is being banned in animal feed due to the possibility of the emergence of resistant microorganisms. Therefore, it is necessary to study in vivo various natural additives that have similar characteristics to the growth promoters, in order for them to be used in poultry feeding in the future (Langhout, 2000).
The cashew (Anacardium occidentale L.) is a tropical plant, native of Brazil, scattered in almost all its territory. The fruit of the tree consists of an outer shell (epicarp), a tight-fitting inner shell (endocarp) and a strongly vesicant cashew nut shell liquid (CNSL). The CNSL is contained between the inner and outer shell (pericarp) in a honeycomb matrix. CNSL is a unique natural source of meta-alkyl phenols with a variable degree of unsaturation attached to the benzene ring. Based on the mode of extraction from the cashew nut shell, CNSL is classified into two types: solvent-extracted immature CNSL (iCNSL) and technical CNSL. A typical solvent-extracted material contains anacardic acid (60-65%), cardol (15-20%), cardanol (10%) and traces of 2-methyl cardol. Depending on the conditions of the roasting process, the composition of the technical CNSL can change and have higher cardanol content (83-84%), less cardol (8-11%) and maintain polymeric material at 10% and 2-methyl cardol content at 2% (Kumar et al., 2002).
Laboratory pharmacological tests showed the antiseptic properties of CNSL acting against the microorganisms responsible for tooth decay (Streptococcus mutans) and acne (Propionibacterium acnes). In addition, the CNSL is moderately effective in treatments against eczema, psoriasis and leprosy (Sousa et al., 1991).
In short, the positive effects observed in vitro motivates further research in this area to determine the ideal dietary inclusion level and the mode of action of these plant products to achieve optimal growth performance.
The purpose of this study was to verify the performance, carcass yield, relative weight of internal organs and intestine microbiology of broiler chickens fed diets containing different inclusion levels of CNSL.
MATERIAL AND METHODS
The experiment was performed using 540 male chicks with one day of age, distributed in a completely randomized design with six treatments and six replications, each replication consisting of fifteen birds. The treatments were: control (T1 - without growth promoter virginiamycin and CNSL); inclusion levels of 0.10mL (T2), 0.20mL (T3), 0.30mL (T4) and 0.40mL (T5) of CNSL/kg of feed; and commercial promoter virginiamycin (T6). These supplements were added to basal diets.
The extraction of CNSL occurred through the thermal-mechanical (hot oil) process, in which very hot CNSL is used as a means to heat the nuts in nature to approximately 190ºC; at this temperature, the outer shell breaks down and releases the alkyl phenols present in the porous shell (mesocarp), followed by the removal of the inner bark, which allows the recovery of almonds.
The birds were reared in 30 floor pens of 1.5m2 each, with water troughs and hanging feeder, a source of infrared heating lamps of 250W, receiving water and feed ad libitum. The bed of shavings was used at a height of 5cm. The birds were vaccinated against Newcastle and Gumboro diseases at fourteen days of age.
The feeding program consisted of a starter diet (until 21 days of age), a growing diet (22-35 days of age) and a finisher diet (36-40 days of age). The composition of the experimental basal diets is shown in Table 1. All diets for each period were prepared with the same batch of ingredients, and all diets within a period had the same composition. Diets were formulated to meet requirements of the "Brazilian tables for poultry and swine - Feed composition and nutritional requirements" (Rostagno et al., 2005) for broilers of those ages. The antibiotic growth promoter virginiamycin was used in the amount of 10ppm.
In the experimental period, body weight, feed intake, feed conversion and viability were evaluated at 21 and 40 days of age. At 40 days old, two birds per replicate (12 birds per treatment) were selected and after a six hour fast they were slaughtered to determine yields of carcass and commercial cuts (breast, thigh and drumstick, back, wings, feet, head and neck), which were expressed as percentage of body weight before slaughter. In addition, proventriculus, gizzard, intestines, pancreas, spleen, heart and liver were removed to determine the relative weight of internal organs (% of body weight).
In the microbiological evaluation one bird per replicate was chosen for the collection of the gastrointestinal tract (small and large intestines). For this purpose, the birds were euthanized through cervical dislocation and a cut in the abdominal cavity was immediately done to expose the intestines. Three ligatures were performed at the beginning of the small intestine, rectum and ileocecal junction with suture material. Respective cuts were performed on both extremities and in the ileocecal junction and immediately placed into zip lock bags (10cm x 14cm x 0.1). Possible residues of cuts on the extremities were removed with distilled water. The samples were identified in the outer and inner part of the zip lock bags and introduced in polystyrene boxes containing ice. Sample collection lasted approximately one hour. After the collections were completed a thermal polystyrene box with a 50 liter capacity containing the samples was completely filled with ice and enveloped to transport via airway to the JFLAB - SP laboratory. The samples were collected according to septic procedures and with sterilized material. The broilers were subjected to a two hour ration fast. The period between the collection and the processing of the samples in the laboratory was about 20 hours.
Samples of 25g of intestinal contents were placed in vials containing 225mL of saline solution at 0.85% resulting in a 10-1 dilution. From this dilution consecutive decimal dilutions were performed using the same proportion. The presumptive test was done from 10-1 to 10-7 dilutions of the contents from intestinal samples. For each dilution a inoculum of 1.0mL was used in the petri dish for each microorganism under evaluation. Escherichia coli was enumerated on Mac-Conkey Agar (Difco) after aerobic incubation at 37ºC for 24h. For the growth of Clostridium perfringens, each dilution was inoculated into fluid Thioglycolate media. For assessment of Salmonella intestinal contents of birds were inoculated in test tubes containing enrichment media Rappaport Vassiliadis, Selenite-Novobiocin and Tetrationate and incubated for 24h. The colony count data was expressed as the number of colony forming unit (CFU) per gram of intestinal content. These values were transformed into log10 for analysis and interpretation of results (APHA, 2001).
This study was composed of a randomized complete design with six treatments. The number of replicates varied according to the data assessed, including six for performance and microbiological count data and 12 for the slaughter yield and relative weight of internal organs. All data was analyzed through the GLM SAS procedure (Statistical..., 2000). Treatment means were compared through the Tukey test at 5%. The regression analysis was used to determine linear and quadratic responses to 5%. This assessment left out the treatment with growth promoter. The microbiological count data (Escherichia coli) was transformed into the square root of (X+1).
The results of broiler performance at 21 days of age are presented in Table 2. The results of body weight, feed intake, feed conversion and viability of birds were not significantly affected by treatments (P>0.05).
The data corresponding to five levels of inclusion of cashew nut shell liquid (CNSL) were subjected to regression analysis. The results showed no linear and quadratic effects in the variables under study.
In the present study there were no significant differences (P>0.05) for the body weight, feed intake, feed conversion and viability of birds variables at 40 days of age (Table 3).
Carcass yield was significantly influenced (P<0.05) by treatments (Table 4). Birds fed the growth promoter had higher carcass yield when compared to the treatment without the inclusion of additives (P<0.05).
The data subjected to regression analysis showed a linear effect (P<0.05) for carcass yield (Y = 79.8 + 17.8X R2 = 0.65). According to the data we can infer that the increase in the level of inclusion of CNSL increases carcass yield. Feet yield was greater for treatment with virginiamycin in relation to the group that received the CNSL level of 0.30mL/kg (P<0.05). Neck yield showed a linear effect (P<0.05). The results showed that the relative weight of the neck decreased with increasing levels of CNSL inclusion (Y = 3.89 - 0.73X R2 = 0.82). The regression analysis for the other slaughter yield parameters showed no significant effect (P>0.05).
The results on the relative weight of internal organs are shown in Table 5. Results showed statistical differences in relative weight of the intestines between treatments with the growth promoter and control (P<0.05). Broilers fed the growth promoter had a lower relative intestine weight when compared to broilers fed the control diet.
The data on the relative weight of internal organs was submitted to regression analysis and the results showed that only the relative weight of the intestines had a linear effect (P<0.05) (Y=3.546 - 1.67X R2 = 0.98), while the other parameters showed no significant effect (P>0.05).
The concentration of Escherichia coli in the intestines of birds was not statistically affected by treatments (Table 6). However, there was a gradual reduction of the concentration of bacteria in the intestinal contents to the level of 0.30mL/kg (quadratic effect P<0.05). Salmonella spp. and Clostridium perfringens were not identified.
The vegetal extracts are a relatively young class of feed additives and in recent years these feed additives have gained considerable attention in the feed industry. They are a wide variety of herb, spices and products derived thereof and are mainly essential oils. Theses additives have been developed for use as alternatives to antibiotics in the animal industry partly due to their biological properties such as antimicrobial and antiseptic activities. However, limited studies are available to assess the possible application of theses extracts as alternatives to antibiotics in broiler chicken production (Langhout, 2000).
This study evaluated the inclusion of cashew nut shell liquid (CNSL) as a possible replacement for growth promoters in broiler chicken diets. The results showed that there was no improvement in body weight, feed intake, feed conversion and viability of the birds when growth promoter virginiamycin and different levels of inclusion of CNSL were added to the diet.
Presumably, the current study conducted with well nourished animals and disinfected environments might have not induced the improvement of growth-related parameters in birds fed the diet supplemented with antibiotics and the cashew nut shell liquid (0 to 0.40mL of CNSL/kg of diet). It has also been well documented that dietary antibiotics such as penicillin do not promote growth performance when animals are raised in germ-free conditions (Coates et al., 1963). Similar to antibiotics, dietary CNSL as a growth promoter could not give beneficial results when birds are kept at optimal conditions such as highly digestible diets and clean conditions (Jang et al., 2004).
Some experiments with broiler chickens also resulted in no statistical difference in the performance of animals supplemented with different species, concentrations and combinations of plant extracts in the diet. According to Lee et al. (2003), the absence of effect on broiler performance may be related to the composition of the basal diet provided and/or environmental conditions in which the experiment was conducted. Rations with ingredients with high digestibility limit the proliferation of bacteria in the intestinal tract, because there is no substrate available for bacterial growth, thereby reducing the antimicrobial potential of plant extracts. The same can be observed if the birds have been raised in places with low immune challenges and strict sanitary control (Simsek et al., 2007).
This is the first study conducted to evaluate the inclusion of CNSL in the diet of birds and there are no parameters to compare these results to in the current literature. However, the results show that bird performance was normal for the experimental conditions. This is an important indicator showing that the health, management and nutrition were adequate for animal growth, thus preventing the observation of possible benefits of tested treatments.
In this study, the carcass yield was higher in the treatment containing virginiamycin compared with the control. In addition, there was a linear upward effect with increasing inclusion levels of CNSL in the diet. The results are consistent with those observed by Manoj et al. (2008) who observed a higher carcass yield in broiler chickens fed virginiamycin when compared to control. In addition, Alçiçek et al. (2004) observed higher carcass yield when they added a mixture of essential oils in the diet. However, the results of the present study are in disagreement with the results of Garcia et al. (2007) who showed that the carcass, right breast, and right thigh yields of birds at 49 days of age were unaffected when broilers were fed avilamycin or 200ppm of blended oregano, cinnamon and pepper essential oils. Furthermore, Leeson et al. (2005) observed no effect on carcass weight when broilers were fed virginiamycin or 0.2 or 0.4% butyric acid. In addition, Isabel and Santos (2009) showed that the breast weight as a percentage of the carcass was significantly higher in birds fed supplements of 100 ppm of clove and cinnamon oils than in control.
Relative weights of the proventriculus, gizzard, pancreas, spleen, heart and liver were not affected by dietary treatment. The results of the present study are in agreement with the results of Hernandez et al. (2004) who found no differences in gizzard, liver and pancreas weights of broiler chickens fed diet containing an essential oil extract from oregano, cinnamon and pepper and a labiatae extract from sage, thyme and rosemary. Similar results were observed by Jamroz et al. (2005) who used essential oils in broiler diets based on maize and locally grown cereals.
Relative weight of intestines was lower in the treatment with a growth promoter when compared to control, and there was a reduction in this organ's weight with increasing inclusion levels of CNSL. Taking both statistical analyses into account, the inclusion of virginiamycin and CNSL reduced the relative weight of the intestines. Visek (1978) demonstrated that the inclusion of antibiotics reduces the weight and length of the intestines in poultry. An outstanding feature of germ-free animals are the greatly enlarged ceca which to date have not been explained. They are believed to contain biologically active substances based upon the behavior of the cardiovascular system after cecectomy (Gordon and Pesti, 1971).
It is known that some feed additives originating from plant products have a profound impact on gut microflora either directly or indirectly (Cowan, 1999), although birds have little nutritional advantage from intestinal microflora compared with other species of animals. In the current study, birds fed diets containing CNSL showed a similar magnitude of Escherichia coli when compared to those fed antibiotic-supplemented diet. However, there is a reduction in the concentration of bacteria when the level of inclusion of CNSL increased, reaching a minimum concentration to the level of 0.30mL/kg.
Almost all the CNSL commercially available is submitted to a heating process. In the thermal processing, the anacardic acids are easily decarboxylated to cardanols. As a consequence of this process, the strongest antibacterial activity of anacardic acid in CNSL is reduced because cardanols are less active. Thus, the antibacterial activity of CNSL is weakened by thermal processing verifying that the activity against Staphylococcus aureus and Bacillus ammoniagenes is reduced 32 times (Himejima and Kubo, 1991). In this study, probably because the CNSL had been subjected to heat, the lowest concentrations of CNSL (0 to 0.20mL/kg) failed to reduce the concentration of Escherichia coli in intestinal contents.
In addition, the tested Gram negative pathogen, Escherichia coli, was not particularly sensitive to virginiamycin. It is known to be active mainly against Gram positive microbes (Proudfoot et al., 1990) and this is therefore in agreement with the current findings. Moreover, the presence of Clostridium perfringens was not observed, and strains of Salmonella spp. were absent.
Antimicrobial activity has been recognized as the major beneficial effect of vegetal extract on animal production, although the exact antimicrobial mechanism has not been fully revealed. Numerous in vitro studies demonstrated that essential oils including thymol, carvacrol, etc., displayed antimicrobial activity against intestinal microbes such as Clostridium perfringens,Salmonella Typhimurium and Escherichia coli (Hammer et al., 1999). On the other hand, in an in vivo study, it seems that the effect of vegetal extracts on gastrointestinal microflora is not consistent, even though essential oils have been generally recognized as an antimicrobial agent. Therefore, it is speculated that the in vivo antimicrobial property of vegetal extracts in birds can be influenced by basal diet and environment conditions.
The present results clearly show that CNSL can control the proliferation of Escherichia coli in the broiler intestine. Moreover, it appears that CNSL in the current study prevents the presence of Clostridium perfringens and Salmonella spp. in intestinal contents of broilers.
The cashew nut shell liquid (CNSL) can be included in the diet of broiler chickens in the levels studied at different phases of growth without harming the performance and carcass yield of birds. Escherichia coli concentration in intestinal contents is reduced by the inclusion of CNSL in the diet.
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Recebido em 19 de outubro de 2010
Aceito em 9 de maio de 2012