With high density confinement rearing of livestock, an additional important role of nutrition is that animals are not only fed for production or reproductive performances but must also be fed to minimize infectious disease and their concomitant stresses. In context of Indian Poultry Industry, problem of immunosuppression has been felt to be prominent due to various factors viz., managemental conditions, nutritional status, intensive production system, high density rearing and infectious diseases. Therefore, it is highly essential to find ways and means for enhancement of immune response by nutritional manipulation. Substantial information is available in literature to indicate that administration of certain vitamins, minerals, amino acids and their different combinations to mammals and chicken in excess of their supposed requirements enhances their disease resistance. This increased resistance has been attributed to significant stimulation of humoral and cellular immunity and phagocytosis. Since, the use of antibiotics has been limited, better use of supplementary immuno-stimulatory nutrients has to be made in poultry feeding. Hence, reports of studies undertaken in this direction have been summarized hereunder.
Low and very high dietary vitamin A decreases body weight gain in broilers. Low dietary vitamin A causes depression in in vitro T-Lymphocytes responses and in vitro antibody production to defined protein antigens. Excess vitamin A intake also decreases immune responses. Maximum T-cell proliferative responses to antigen have been observed at vitamin A levels considerably above NRC (1984) recommended level. Vitamin A is required for intestinal absorption of zinc (Zn) in poultry while zinc influences vitamin A utilization by affecting retinol binding protein (RBP) synthesis and release from liver. However, the combined level effect of vitamin A and Zn has not been examined on performance and immune response of broilers. Therefore, a study was conducted to find out the effect of supplementation of vitamin A (0, 4500, 8500 and 12500 IU/kg) and Zn (0, 30 and 60 mg/kg) to a basal diet containing vitamin A, 1500 IU/kg and zinc, 35 mg/kg in a factorial experiment design. Chicks were immunized against New Castle Disease Virus (NDV) F-strain by S/C route at day 21. Blood samples were collected at 0, 10 and 21 days of post-immunization (PI) and serum antibody titers to NDV were determined. For serum antibody titers HI test and ELISA were employed. Optimum growth, best feed efficiency and maximum cellular response was observed in chicks fed diet supplemented with 12500 IU/kg vitamin A and 60-mg/kg zinc. Both HI and ELISA titres were peaked at 10 d post-immunization on diet supplemented with vitamin A and Zn levels of 12500 IU/kg and 30 mg/kg, respectively.
Vitamin E enhances specific humoral and cell-mediated immune responses as well as native resistance to disease, particularly phagocytosis. Supplemental levels of vitamin E have an immuno-stimulatory effect, increase delayed hypersensitivity and affect mitogenic responsiveness. Dietary supplementation of Se at levels above those recommended as nutritional requirements (0.1 ppm) enhances the primary immune responses. Vitamin E and Se appear to participate in similar nutritional and bio-chemical relationships. Supplementation of vitamin E in the diet of chicks enhances humoral immunity, which may be due to destruction of peroxides by vitamin E. Vitamin E and Se play a role in protecting against oxidative damage. Free radicals are scavenged by vitamin E as a first line of defense and then glutathione peroxidase of which Se is a part destroys any peroxides formed before they can damage the cell. Nutritional deficiencies of vitamin E or Se or both impair immune function as measured by humoral response to sheep red blood cells in young chicks.
Accordingly studies have been conducted with various levels of Se, vitamin E and their combinations to examine the effect on performance and immune response of broilers. Effect of supplementation of vitamin E, selenium and their combinations suggested that maximum body weight gain and best efficiency of feed utilization were observed in broilers fed diets containing 0.50 mg/kg Se and 300 IU/kg vitamin E. Significantly higher antibody titres (HI and ELISA) at 10 d PI were attributed to 0.06 mg/kg and 150 IU/kg Se and vitamin E, respectively. Hence, optimum growth and immune response may be achieved at supplemental level of Se of 0.06 mg/kg and vitamin E at 150 IU/kg. The vitamin E level is higher than that of recommended by NRC (1984, 1994).
Maize-soybean diets are first limiting in the sulphur containing amino acids and thus require methionine supplementation. In addition to other functions, methionine serves as donor of methyl groups and a source of sulphur. Addition of methionine over and above, the recommended requirement of broiler improves their performance in terms of body weight gain and feed conversion efficiency (FCI). Enhanced antibody titre and increased mitogen stimulation by phytohaemaglutinin-P (PHA-P) in chicks have also been reported due to methionine supplementation of maize-soyabean diet. Choline can spare methionine for growth of broiler chicks. Choline is capable of increasing the FCI to the same degree as L-methionine. Improvement in body weight gain and FCI has also been observed with choline supplementation of chick diet either alone or in combination with methionine. Keeping the above results in view, the present study was undertaken to find out the effect of methionine and choline, either singly or in combination, on the performance and immune response of broilers.
A study was conducted with broilers to find out the effect of addition of methionine (0.0, 1.5, 3.0 and 4.5 g/kg) and choline (0.0, 1000 and 2000 mg/kg) to a basal diet containing crude protein, 221 g/kg; ME, 12.25 MJ/kg; methionine, 3.6 g/kg and choline, 1300 mg/kg. Supplemental levels of methionine and choline were found to be ineffective in improving the growth, food consumption and food conversion efficiency of broilers. However, a higher value for leucocytes migration inhibition was observed in chicks fed on the diet containing 6.5-g/kg methionine and 1300 mg/kg choline, indicating significantly improved cellular immune response. HI test and ELISA indicated enhanced antibody titres in chicks receiving 3.0 g/kg methionine and 3,300 mg/kg choline, showing a significantly better humoral immune response. Methionine and choline should be supplemental at levels higher than the recommended level of BIS for better health and production in chicks.
Various studies conducted on the effect of supplementation of different combinations of some selected nutrients immune response suggested better cellular and humoral immune responses in broilers fed diets containing combinations different nutrients at levels given in Table 1. Results suggested that supplementation of combination of many above given nutrients could be beneficial for cellular and humoral immune response.
Table 1. Effect of supplementation of combinations of many nutrients and combination of two nutrients at different levels on the present improvement in LMI and antibody titres (HI & ELISA) of broilers
|
Nutrients and their levels |
LMI% |
Percent increase over control |
HI titre |
Percent increase over control |
ELISA titre |
Percent increase over control |
Vitamin A & Zn1 8500 IU/kg, 30 mg/kg |
53.46± 2.27 |
45.78 |
6.25± 0.29 |
31.57 |
2.56± 0.06 |
13.27 |
Vitamin A & Zn2 12500 IU/kg, 30 mg/kg |
58.25± 2.00 |
58.85 |
7.75± 0.29 |
63.15 |
2.72± 0.04 |
20.35 |
Vitamin E & Se1 150 IU/kg, 0.10 mg/kg |
52.98± 1.49 |
36.48 |
8.80± 0.33 |
88.88 |
2.87± 0.06 |
49.58 |
Vitamin E & Se2 300 IU/kg, 0.00 mg/kg |
51.41± 0.80 |
32.43 |
7.50± 0.33 |
66.67 |
2.56± 0.06 |
33.33 |
Methionine & choline1 0.15%, 2000 mg/kg |
61.53± 4.57 |
57.81 |
7.35± 0.66 |
37.90 |
2.62± 0.06 |
15.93 |
Methionine & choline1 0.30%, 2000 mg/kg |
56.69± 1.90 |
45.40 |
8.33± 0.33 |
56.28 |
2.72± 0.04 |
20.35 |
1 + 4 + 6 |
57.37± 1.73 |
56.56 |
9.00± 0.47 |
34.93 |
2.87± 0.66 |
16.60 |
2 + 4 + 6 |
64.33± 2.17 |
76.00 |
9.00± 0.47 |
34.93 |
2.87± 0.06 |
16.60 |
