Aflatoxins (AF) are a group of closely related biologically active mycotoxins produced by
Aspergillus flavus and
Aspergillus parasiticus. They commonly occur as natural contaminants of poultry feeds
(Sapcota et al., 2006). Fungi or mould growth in feedstuff is associated with the utilization of nutrients from the host. Consequently, alterations in the nutritional content of the feedstuff are expected. The extent of mould growth determines the degree of depletion in the nutrient content of the feedstuff. Aflatoxins are highly hepatotoxic, neurotoxic, teratogenic and carcinogenic imparting various deleterious effects on vital organs such as the liver and kidney resulting in a reduction of body growth, poor feed utilization and lowering immunogenesis leading to mortality
(Girish and Devegowda, 2006). The AFB1 decreased contents of Hb and C3bRR and ICR increased the number of RBCs and impaired the erythrocyte functions
(Tingting et al., 2015). The significant changes in serum biochemical and haematological parameters are seen in aflatoxicated broiler chickens
(Kumar et al., 2016). Affected birds show poor vaccine response and low antibody titre, as both cellular and humoral immunities are affected
(Corrier, 1991).
Certain studies have been performed for removing AF from contaminated feed and minimizing the toxicity of AF using Zeolites
(Miazzo et al., 2000), bentonites
(Oguz and Kurtoglu, 2000), inorganic sorbents
(Baily et al., 1998), esterified glucomannan
(Girish and Devegowda, 2004) and diatomacious earth
(Lakkawar et al., 2016) to reduce the AF absorption from the gastrointestinal tract in poultry. Mycosorb is a cell wall derivative of
Saccharomyces cerevisiae, has shown considerable binding ability with several commonly occurring mycotoxins and is also found beneficial as a low-inclusion binder in minimizing the adverse effects of aflatoxins present in contaminated livestock and poultry feeds
(Girish and Devegowda, 2006; Yildirim et al., 2011 and
Maldhure et al., 2015). Studies regarding the effect of mycosorb on nutrient utilization in aflatoxicated broiler chickens received very little attention. Hence, this study has been designed to through some light on this aspect.
Aflatoxin B1 was produced in the laboratory through solid substrate fermentation in broken rice using a pure culture of
Aspergillus parasiticus, NRRL 2999 strain
(Shotwell et al., 1966). The fermented rice was autoclaved (15 lbs pressure for 15 min) to kill the fungi, dried, (55-60°C overnight), ground to powder form and its AFB1 content was measured by the method described by
Romer (1975) using TLC. A standard basal diet was prepared with toxin-free conventional feedstuffs (Table 1) and the rice powder grown with a known amount of AFB1 was incorporated into it to provide the desired level of 300 ppb of toxin per kg of diet. Mycosorb
(
Esterified glucomannan) required for the experiment was procured from M/s Alltech Biotechnology Pvt. Ltd, Bangalore and used in the experiment as per the following schedule:
Altogether 270 Nos of day-old commercial chicks with uniform body weight were distributed randomly into 6 treatment groups. Each group had a total of 45 Nos of chicks in triplicates of 15 Nos, housed in an iron cage battery under optimal managemental conditions from day-old to 42 days. The birds were offered water and feed
ad libitum throughout the experimental period of 6 weeks. A balance trial of three days duration at the 6th week of age was conducted for the determination of a dry matter, protein, calcium and phosphorus retentions. The study started with five-hour starvation at the beginning and the birds were given weighed experimental diets daily for 3 days at a fixed hour in the morning. The polythene sheets were spread on the faecal tray for the collection of excreta. The excreta were collected and weighed. The samples of faecal material after mixing it well were collected for further analysis. Feed and faecal samples were weighed and oven-dried in the laboratory. The samples were later analyzed for the proximate composition according to the methods of
AOAC (2005). Calcium and phosphorus were separately analyzed using standard methods
(Talapatra et al., 1940; AOAC, 2005). The nutrient retention of dry matter, crude protein, ether extract, crude fibre, calcium and phosphorus were calculated by using the following formula:
The data obtained were subjected to statistical analysis as described by
Snedecor and Cochran (1994).
Dry matter, crude protein and crude fibre retentions
The dry matter (DM) retention was significantly (P<0.05) affected due to aflatoxicosis (Table 2). The reduction was 5.62 per cent as compared to the control group. However, improvement in DM retention was noticed after the dietary inclusion of Mycosorb in toxin-fed birds. The toxin binder with a dose of 0.10 per cent yielded significantly higher DM retention, making the value comparable to that of the control group. Similarly, the protein retention was also reduced due to aflatoxicosis to the extent of 7 per cent. Using Mycosorb in the diet of aflatoxin-fed birds the improvement in protein retention was noticed in a dose dependent-manner. The lower dose of Mycosorb was ineffective whereas, the medium or higher doses,
i.
e., 0.05 or 0.10 per cent could significantly (P<0.05) improve protein retention.
Aflatoxicosis lowered the ether extract retention to the extent of 6.25 per cent in the toxin-alone fed group as compared to the normal birds of the control group. However, the incorporation of Mycosorb in the diets of aflatoxin-fed broilers significantly improved the ether extract retention. The lower and medium doses of Mycosorb yielded comparable results whereas; significantly more retention was noticed with the higher dose (0.01 per cent). Nevertheless, even with the highest dose of Mycosorb the counteraction of aflatoxicosis was not complete since the ether extract retention values remained significantly lower than that of the control group. Using dietary aflatoxin (300ppb) in commercial broiler chickens
Ahmed et al., (2007) and
Gogoi (2003) noted significantly (P<0.05) lower retention of dry matter, crude protein and ether extract in their 6-week-old trials. Similar findings were observed by
Shamsudeen and Shrivastava (2013).
It is a fact that the liver is the main organ where various digestive enzymes are synthesized. Further, aflatoxin is reported to be a hepatotoxic and cytotoxic agent as it directly affects the liver resulting in various pathological conditions depending upon its doses and severity of stress. Thus, the decline in the digestibility of dry matter, crude protein and ether extract might be due to the pathological conditions of the liver. The aflatoxin might have caused alteration in intestinal physiology and intestinal mucosal damage due to chronic inflammation which might have led to decreased absorption of nutrients. This is supported by earlier findings of
Kelly and Arora (1976) who observed hemorrhage on intestinal organs due to AF and
Balachandran and Ramakrishnan (1987) who observed catarrhal inflammation in intestinal mucosa Addition of Mycosorb might have helped the liver to revitalize its digestive function at varying degrees in proportion to its doses. Among the three graded dietary doses of Mycosorb (0.025, 0.05, or 0.10 per cent) the highest one showed significantly (P<0.05) better results in retention of dry matter, crude protein and ether extract. No significant difference was observed in CF retention among all the six groups. This might be because the CF digestion takes place in the caeca, which might not have been affected due to aflatoxicosis. However, the available literature is limited to elucidating the matter.
Calcium and phosphorus retentions
The dietary inclusion of aflatoxin in broilers significantly reduced (P<0.05) calcium retention to the extent of 6.04 per cent as compared to the control group. The result is in agreement with the observations of
Ahmed et al., (2007) and
Shamsudeen and Shrivastava (2013). This might be due to the action of aflatoxin hampering the process of calcium digestion and absorption resulting in lower calcium retention. Reduced feed intake by the birds consuming dietary aflatoxin might have contributed to lower calcium retention. However, when toxin-fed broilers were treated with Mycosorb the calcium retention was improved significantly in a dose dependent-manner. Among three doses of Mycosorb the highest dose (0.10 per cent) gave significantly (P<0.05) more calcium retention and the value was found to be comparable with that of the control group.
The phosphorus retention was lowered (P<0.05) to the extent of 6.06 per cent in aflatoxin-alone fed broilers as compared to control birds (Table 2). Similar observations were noted by
Ahmed et al., (2007) and
Shamsudeen and Shrivastava (2013). This might be due to lower feed intake and poor absorption of nutrients in the aflatoxin-treated birds. However, the incorporation of Mycosorb in the aflatoxin-containing diets improved phosphorus retention. It could be noted that a lower dose (0.25 per cent) could not significantly improve the phosphorus retention, whereas medium and higher doses significantly improved the condition with comparable results. Mycosorb, with medium or high doses, gave complete counteraction since the phosphorus retention value was found to be at par with that of the control group.
