In Pakistan poultry sector is playing a vital role in bridging the gap between supply and requirement of animal protein food for its ever increasing human population. The contribution of poultry sector in agriculture and livestock is about 6.4 and 11.5 percent, respectively (Anonymous, 2012). Poultry meat contributes about 25.8 percent of the total meat produced in the country. This sector has been growing at an annual rate of 8 to 10 percent, producing 131.4 million eggs and 0.834 million metric tons of poultry meat (Anonymous, 2012). However, despite this tremendous growth rate, this sector is facing many challenges which may badly influence its future pace of development. The most important of these is escalating cost of poultry feed which is considered to be the major cost item involving more than 60 to 70 percent share of production cost (Khan et al., 2010). Many of the traditional protein sources used in poultry diet formulations such as soybean, fish, sunflower meal and groundnut meal are becoming extremely expensive.
Rapid growth of human, livestock and poultry population has increased the demand for food and feed which has necessitated that alternative feed resource should be identified and evaluated. Therefore, the search for alternative protein sources has become urgent, and in this context, algae are worthy of consideration. The possibility of using fat-extracted algae (a by-product from bio-fuels production) as a source of protein and other nutrients in poultry feeds appears to be of great significance. The use of algae as a source of nutrients can benefit poultry and bio-fuel industry.
Diatoms are a major group of unicellular algae, and are one of the most common types of phytoplankton. They differ from other algae in the presence of substantial amounts of silicon in their cell membranes. The diatom, Nanofrustulum is currently under investigation as a potential source of oil for bio-fuel production. However, effect of dietary inclusion of defatted algae supplements by replacing soybean meal and corn on the performance of broilers has not yet been thoroughly investigated. The present study was therefore under taken at Poultry Research Farm, Department of Animal Science, University of Cornell, USA, to investigate effect of defatted algae Nanofrustulum meal on the growth performance, blood biochemical composition and gross pathology of tissues in broilers.
For this purpose, two levels of defatted algae Nanofrustulume 7.5 and 10 percent were used. Four different, iso-caloric and iso-nitrogenous experimental rations were prepared. The diet A was prepared without inclusion of algae (control), whereas in diets B and C the same algae at the rate of 7.5 percent were incorporated to replace soybean meal and soybean meal + corn, respectively. In diet D, algae at the rate of 10 percent replaced soybean meal and corn. Eighty, commercial (Ross), day-old, broiler chicks, 40 each of both sexes, were randomly divided into to 4 treatment groups (A, B, C and D) with two replicates each of 5 male and female birds per treatment. They were initially weighed and wing banded individually for identification and then maintained in thermostatically controlled battery cages. The birds were provided 22 hours light: 2 hours darkness schedule. All the experimental birds were fed a balanced broiler starter ration and water ad libitum until 21 days of age. All the experimental rations were supplemented with additional quantity of potentially limiting amino acids, lysine and methionine. The amount of corn oil in all the rations was adjusted to maintain metabolizable energy contents at 3000 and 3200 Kcal/Kg for the chick starter and grower rations, respectively. The amino acid contents of starter and grower diets were kept higher than NRC (1994) standards. On day 22nd, the birds were transferred to growing cages maintained at room temperature and similarly fed grower diets ad libitum until 42 days of age. The data on feed intake, body weight gain were collected. Feed conversion efficiency were calculated. On day 42nd of the experiment, the experimental birds were fasted for 3 hours and blood samples were collected from the wing vein from randomly selected, 2 birds each of both the sexes per replicate for determination of blood biochemical composition following standard laboratory procedures. Gross pathology of tissues obtained from slaughtered birds was also performed. The study was conducted according to Randomized Complete Block. Design (RCBD). The data thus recorded was subjected to statistical analysis using Analysis of Variance Technique (Steel et al., 1997). The means were compared using Duncan's Multiple Range (DMR) Test (Duncan, 1955).
The results of this study showed significant (p?0.01) difference in average feed intake among treatments and between sexes of broilers. In male broilers, the significantly highest feed intake was observed in birds fed diet C followed by those fed diets D, A and B, whereas in female broilers the highest feed intake was recorded by the birds fed diet A and then followed by those fed diets B, C and D. The results further showed non-significant differences in feed intake of male broilers between treatment groups C & A and C & D, whereas significant difference was recorded between group B and C. Significantly lowest feed intake was recorded in female broilers fed diet D which was also significantly different from treatment groups A and B. The results also showed that with increase in inclusion levels of algae in female broilers depression in feed intake increased. The results in respect of average weight gain showed that male and female broilers fed the control diet attained the highest weight gain, followed by those fed diets C, D and B, respectively in male broilers and fed diets C, B and D in female broilers, respectively. The male broilers attained significantly (p<0.01) better weight gain than female broilers. The weight gain in broilers fed the control diet was not significantly (p?0.05) different from those fed diet C. The overall results of the study showed depression in weight gain of birds fed diets containing different levels of algae in comparison to those fed control diet.
In the present study, the feed conversion ratio was significantly (p< 0.05) influenced by the diets, however it was not significantly different between sexes. In male broilers the poorest FCR was observed in group D followed by in groups B, C and A. The best FCR in male broilers was recorded in group A which was significantly better than that of treatment groups A and D, however non- significant difference between FCR of groups A and C was recorded. In female broilers, the best FCR was observed in birds fed diet C followed by those fed diets A, D and B, however, non- significant difference in FCR among diets was recorded.
Non- significant (P > 0.05) differences in plasma alkaline phosphatase (AKP), alanine transferase (ALT), serum cholesterol, tri glycerides (TG) and non-esterified fatty acids (NEFA) levels among diets and between sexes were detected. Significant (P > 0.05) differences in serum uric acid among diets and between sexes were detected. Female broilers had significantly higher uric acid levels than male broilers. In male broilers fed diet A, plasma uric acid value was observed to be significantly higher than those fed diet D but it was not significantly (P>0.05) different from those fed diets B and C. In female broilers fed diet A, plasma uric acid concentration was significantly higher than those fed diets C and D, however the differences were observed to be non-significant. Significant (P?0.05) difference was observed between uric acid values both in male and female broilers fed diets B and D, however, female broilers fed diet C differed non- significantly (P?0.05) from those fed diet D. On overall basis, there was significant (P?0.05) reduction in uric acid concentration by addition of 7.5 percent algae in the diets. No gross pathological lesions were seen on internal and outer surfaces of gizzard and proventriculus and these were normal in size, however, the internal membrane of gizzard was darker yellow color in birds fed diets containing algae. No lesions were noticed on liver, spleen and intestines and liver and spleen were normal in size. Liver was also of normal color.