Performance, Immunity and Blood Biochemical Parameters of Broiler Chickens Fed Diets Containing Kappaphycus Alvarezii

Kappaphycus alvarezii (KPA) is a red alga that is also called Eucheuma cottonii. Seaweeds have received significant attention for their potential as sources of natural antioxidants attributed to the carotenoids, tocopherols and polyphenols present which contribute to inhibition or suppression of free radical generation (Athukorala et al. 2006). Kappaphycus alvarezii is rich in enzymes, nutrients, minerals, calcium, iron, fibres and jelly forming proteins. Typical analysis of KPA shows it contains 64.2% carbohydrate, 4.5% protein, 0.9% fat, 1.07% calcium, 9.3mg/kg iron, 1520 mg/kg magnesium and 22 mg/kg niacin (Qadri et al., 2019). The total chlorophyll and carotenoid contents of KPA were 0.180 and 0.634 mg/g of fresh weight, respectively (Abirami and Kowsalya, 2011). Therefore, seaweeds are sources of nutrients as well as nutraceuticals having antioxidant, anti-mutagenic, anticoagulant, anti-cancerous and antibacterial activity and can be grown artificially and thus can be produced in aquatic farms. The objective of the present study was to evaluate the effect of KPA on the performance, immune-response, blood biochemical and gut health status of broiler chickens.

Two hundred and eighty (280) day old straight run (sex ratio ≈ 1) chicks (CARIBRO-Vishal) were housed and distributed randomly into thirty-five groups each of 8 chicks (7 treatments × 5 replicates). The experiment was conducted strictly in accordance with the guidelines of the Institutional Animal Ethics Committee (IAEC).

The experimental diets (T₂-T₇) were supplemented with 0.25 % KPA (T₂), 0.50% KPA (T₃), 0.75% KPA (T₄), 1.00% KPA (T₅), 1.25% KPA (T₆) and 1.50% KPA (T₇) respectively and the basal (T₁) was prepared without any addition of KPA. The source of the KPA was the M/s Aquagri Processing Pvt. Ltd., New Delhi, India. The basal and experimental diets contained 21.51% crude protein, 2950 kcal/kg metabolizable energy, 0.98% calcium, 0.43 % available phosphorus, 1.21% lysine, 0.48% methionine and 0.96% threonine respectively.

Table 1 - Ingredient of starter diet (0-21d).

Table 2 - Ingredient of finisher diet (22-42d).

Body weight changes were recorded every three weeks (0-3 and 4-6 wks) during the experimental period. A weighed quantity of the respective diet was offered ad-lib daily in the morning and the residue was weighed next day to determine pen feed intake. Weekly and period wise feed conversion ratio (FCR) of birds was determined.

At 28 d of age, 8 birds/dietary treatment (56 birds in all) were inoculated intravenously with 1.0 ml of 1% sheep red blood cells (SRBC) suspension to investigate the effect on the humoral immune response and, at 35 d of age, 0.2 ml PHA-P mitogen (1 mg/ml PBS) was injected intra-dermally into the left foot web (another 8 birds/dietary treatment) for measurement of the cell-mediated immune response. Blood samples from 10 birds/treatment (n=70) were randomly collected at 42 d into sterile glass tubes without anticoagulant. Serum was separated by centrifugation at 1512 g for 10 minutes and decanted into plastic vials, and then stored at -20ºC for estimation of serum enzymes alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), kidney function test (creatinine and uric acid), total cholesterol, total protein and albumin using commercially available biochemical kits (Span Diagnostics, India).

Data were tested for significance by SPSS- 20 in a completely randomized design, and means were compared using Duncan’s (Duncan, 1955) multiple range test at P < 0.05.

Body weight gain (g) was significantly (P< 0.05) improved in growing (21-42 d) and overall (0-42 d) phases in T₇ compared to the control and other treated groups; however feed intake (g) and feed conversion ratio (FCR) did not differ significantly (P> 0.05).

Table 3 - Effects of dietary inclusion of Kappaphycus alvarezii on production performance of broiler chickens.

The haem agglutination (HA) titre to sheep red bold cells (SRBC), an index of humoral immunity, and the mitogenic response to PHA-P measured as the foot pad index (FPI), an index of cell-mediated immunity were significantly improved (P< 0.05) by dietary supplementation of 1.5% KPA when compared to other treated groups.

Table 4 - Effects of dietary inclusion of Kappaphycus alvarezii on immune response and blood biochemical parameters of broiler chickens.

No significant (P> 0.05) differences were observed in total protein, creatinine and alkaline phosphatase (ALP) concentration; however, significant (P< 0.05) increases in albumin and aspartate aminotransferase (AST) concentration, and decreased (P< 0.05) alanine amino transferase (ALT), cholesterol and uric acid concentrations in T₇ (1.5% KPA) group compared with control birds and other KPA treated groups were observed.

There are very few reports available in the literature regarding the effect of KPA in poultry diets. In the present study, KPA had a positive effect on growth performance, which was associated with improved immunity. Microalgal KPA had excellent antioxidant properties in the linoleic acid system, and also, ferrous ion-chelating activity which may influence production performance and immune response of broilers (Abirami and Kowsalya, 2011).

It is not clear how KPA enhances immune responses; one possibility is through greater antioxidant property which may protect the membranes and organelles of the lymphocytes from the detrimental effects of pro-oxidants. Moreover, KPA has some beneficial effect on immune characteristics i.e., lymphocytes, IgA, IgM and IgG concentrations which may be involved in modifying the metabolism of arachidonic acid to prostaglandin precursors or related compounds, enhancing immune responses by reducing the endogenous production of prostaglandin (Kang et al. 2013). KPA is rich in polysaccharides, minerals, proteins and vitamins. The inclusion of 1.5% KPA in broiler chicken diets was associated with significant decreases in blood concentration values of cholesterol, uric acids and alanine amino transferase (ALT). The decreased blood cholesterol seen in the present study was presumably due to the presence of more fibre, which may have inhibited hepatic cholesterol synthesis from fermentation metabolites by intestinal microflora. Fibre fermentation produces volatile fatty acids, including propionic acid, which is immediately absorbed through the hepatic portal vein and is transported to the liver where it inhibits the activity of HMG-CoA-reductase and, in turn, the rate of cholesterol biosynthesis (Stipanuk, 2012). In the present study, albumin level increased significantly after supplementation with 1.5% KPA suggesting that KPA had hepato-protective effects which may be exploited as growth promoters in the broiler chicken; positive outcome on the performance, irrespective of the type and level of seaweed used, might be due to a beneficial antimicrobial effect apart from positive impact on structural health of the small intestines, thereby facilitating nutrient absorption and growth performance in broiler chickens.

Thus it is concluded from this study that Kappaphycus alvarezii (KPA) @ 1.5% inclusion in the diet improved performance, immunity and blood biochemical parameters of broiler chickens.