Effects of zinc-methionine and feed restriction on performance, immunocompetence and gut content osmolality of broilers challenged with a mixed coccidial infection

Abstract

An experiment was conducted in which 378 broilers received a basal diet (74 mg kg-1 zinc) supplemented with 0, 40 or 60 mg Zn kg-1 as zinc-methionine (Zn-Met) and with or without early Feed Restriction (FR) to investigate their effects on performance, humoral immunity, intestinal immune responses and gut content osmolarity especially in coccidiosis condition. Chicks consumed feed ad libitum or were restricted on alternate days from 11 to 18 day of age. To simulate a coccidiosis challenge, on day 28 of age the chickens were inoculated with a mixed culture of E. tenella and E. acervulina via drinking water. Antibody response to Sheep Red Blood Cell (SRBC) was determined on day 21. The immunoglobulin A (IgA) content was quantified in sera and mucous membrane tissue of intestine. Ileum and cecum content were measured for osmolarity at 21 and 42 day of age. Zn-Met could not affect average daily gain and feed intake but FR birds that dietary supplemented with 40 or 60 mg kg -1 Zn-Met had significantly (p<0.01) lower feed conversion ratio on 7 to 42 day period comparing to level 0 mg kg-1 of Zn-Met. Antibody response to SRBC increased by 60 mg kg-1 Zn-met supplementation and administration of FR (p<0.01). Sera IgA content increased after the coccidio-infection which its amount either in sera or gut tissue increased by adding Zn-Met to diet. Also, FR led to more IgA production (p<0.01). Variations in osmolarity of ileum and cecum content were similar and they were significantly lower in FR group on day 42, after the coccidiosis challenge. In conclusion, FR early in life enhanced immunity and gut condition later in life. Dietary supplementation with Zn-Met, in a level higher than common practical level, enhanced immunocompetence but not performance. © 2009 Asian Network for Scientific Information.