Abstract
The aim of the present study was to evaluate the effect of feeding regime on changes in growth, mortality, carcass composition, and blood parameters of male and female broiler chickens during feed restriction and the realimentation period. In the experiment, males and females were split into three groups: i) ADL, a group fed ad libitum during the entire experiment; ii) R80, a group that received 80% ad libitum; and iii) R65, a group that received 65% ad libitum . Restriction was applied in both groups from 7 to 14 days old. Daily weight gain (DWG) was reduced significantly in males to 35% in R80 and 39% in R65, and in females to 40% in R80 and 45% in R65. Insignificant compensatory growth occurred in the last week of the growing period. Feed restriction reduced mortality, with a higher mortality reduction in the R65 groups. There was no effect of feed restriction on dressing percentage or thigh yield. However, breast yield was lower and abdominal fat yield was higher in restricted birds. There was a minor effect of feeding regime on blood biochemical and haematological measurements. Males showed significantly higher compensatory growth, feed intake, mortality and thigh yield than females, but dressing percentage and abdominal fat levels were significantly higher in females. Blood total protein and urea concentration were affected by the interaction between sex, group and age. Keywords: blood measurements, carcass yield, feed restriction, growth
Highlights
In the past, commercial strains of broilers suffered severely from metabolic disturbances, such as ascites and sudden death syndrome (SDS), as well as from weak leg bones caused by tibial dyschondroplasia
In the second week of the experiment, when feed restriction was applied, daily weight gain (DWG) was significantly lower in the restricted groups
Lower growth of the restricted chickens might be due to lower protein synthesis, which is indicated by the blood biochemical parameters of protein metabolism
Summary
Commercial strains of broilers suffered severely from metabolic disturbances, such as ascites and sudden death syndrome (SDS), as well as from weak leg bones caused by tibial dyschondroplasia. The feeding regime, namely ad libitum and feed restriction, affects growth, mortality, carcass composition and physiological measurements. Feed restriction may induce compensatory growth in the realimentation period (Govaerts et al, 2000; Tůmová et al, 2002; Van der Klein et al, 2017). Feed restriction has been shown to reduce the high mortality generally observed in commercial broiler operations (Tůmová et al, 2002). Lower mortality of restricted chickens is due to a decreased incidence of SDS and ascites (Lippens et al, 2000; Mohammadalipour et al, 2017) and leg problems (Lippens et al, 2000). Van der Klein et al (2017) did not find such an effect of feed restriction on carcass composition
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