Effects of pre-slaughter feed withdrawal on live weight loss, bacterial population and pH of crop, carcass water uptake and dressing percentage in broiler chicken

This study was carried out to investigate the effects of different preslaughter fasting (PF) periods (0, 4, 8, 12, 16, 20 and 24 h) on live weight loss (LWL), dressed (DCY) and chilled (CCY) carcass yields, water up take ratio (WU) during chilling, crop pH and crop bacterial population of broiler chicken. A sample of 98 mixed-sex Ross broilers provided from a commercial broiler breeder flock at age of 49 days were chosen and randomly allocated to 7 pens; each pen consist of 7 males and 7 females. Prolonged PF significantly decreased the mean live weight of the fasted birds (P<0.05). When data were pooled for male and female birds, live weight loss was 1.902 per cent in 4-h PF and increased to 5.387 per cent after 24-h PF. Chilled carcass yields significantly dropped by 2.5 per cent at 20 h of PF compared to the other treatments. Mean carcass WU with a non linear trend significantly increased for the birds subjected to PF periods either less than 12 or greater than 20 h (P<0.05). The mean pH value of 4.8 for crop contents in control birds significantly increased to 5.75 by 4-h PF (P<0.05), with no considerable changes afterwards. Bacterial count for crop contents revealed a significant increase from 250 (basal count for control group) to 420 cfu/ml in 4-h PF. No significant alteration in bacterial count was observed for prolonged PF periods (P>0.05). The results from this study recommend that duration of feed removal period for commercial broiler chicken prior to slaughter must not exceed 12 h. The negative impacts of pre-slaughter fasting in female broiler chicken were greater than the males.