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Effect of early feed restriction programs on IgY production of broiler chickens
It is known that feed restriction increases antibody production in poultry; but very little research exists exploring the after effects of feed restriction on the adaptive immune system. The objective of this experiment was to evaluate the effects of different programs of early feed restriction on IgY production in broiler chickens. A total of 384 Cobb 500 male broiler chicks were randomly assigned to 24 pens at day 1 of age. The study lasted 42 days. After a week adaptation period, four treatments were applied from day 8 to 16: T1 – control group, standard diet (SD); T2 – quantitative feed restriction (80% of ad libtum feed intake of the SD, according to the breeder management guide); T3 – feed restriction by time (SD offered during 8 hours/day); and T4 – qualitative feed restriction (80% of the limiting nutrients - SD was diluted by the addition of 10% kaolin and 10% rice husk). At day 7 and 21, birds were injected with bovine serum albumin (BSA) and blood samples were collected weekly from day 7 to 42 for assessment of IgY anti-BSA production. There was no effect (P > 0.05) of the first BSA inoculation between treatments; however at 28 days of age, birds in all the three early feed restriction programs had higher IgY anti-BSA than the control group (P < 0.05). At day 35, the quantitative and the by time feed restriction groups still showed residual effects of the BSA injection, but no difference (P > 0.05) was observed between the four treatments at 42 days. It is concluded that the three different programs of early feed restriction had beneficial effect on the humoral immune system after the restriction program had ended. Overall, the quantitative and the by time feed restriction programs promoted the longer lasting responses.
Keywords: chicken, feed restriction, IgY