Effect of quantitative feed restriction on growth and physiologic responses of broiler chicken

An experiment was conducted to determine the effect of sex, period and level of feed restriction on the growth performance, development of duodenum, immune responses and BUN [blood urea nitrogen] level of broiler chicken. Five hundred seventy six day-old chicks were assigned to twelve treatments with 4 replications in a 2x3x2 factorial arrangement in a completely randomized design. Factor A involved feed restriction periods on day 15-21 and day 22-27, factor B was feeding regimes: ad libitum feeding, 20% restricted and 40% restricted, and factor C was sex of chickens. The final body weight of broilers on ad libitum feeding was comparable with birds restricted by 20% but significantly higher than 40% feed-restricted birds. The total feed consumption and body weight gain of ad libitum-fed birds and feed-restricted birds were not significantly different but the total feed consumption was significantly highest in control birds, followed by birds on 20 and 40% restriction. Male birds had significantly higher body weight, feed consumption and better total FCR [feed conversion ratio] compared to female regardless of period and level of restriction. The highest mortality and incidence rates of leg deformities were observed in full-fed birds. During restriction and realimentation periods, the mucosal thickness and villus height of duodenum of ad libitum fed birds were higher than the restricted groups but on day 41, the mucosal thickness, villus height and width and crypt depth of feed-restricted birds were comparable with control birds. Male birds had significantly higher mucosal thickness, villus height and width than female birds. Feed restriction did not significantly affect the hemagglutination Inhibition antibody titer of birds against NDV [Newcastle Disease Vaccine]. The BUN levels appeared to be lower in ad libitum fed birds compared to birds on 20 and 40% restriction, although no significant difference was observed. The results of this experiment showed that birds restricted on the 3rd or 4th week of age at 20% level had comparable growth performance with ad libitum fed birds. Feed restriction at 20% level and on fourth week of age was economically beneficial because of lower mortality and incidence rates of leg deformities, feed cost and significantly lower feed consumption compared to full-fed birds. Feed restriction may be implemented without compromising production of antibodies against NDV, duodenal villus development and BUN level.