ABSTRACT
The study investigated the effects of a potent antioxidant, quercetin, on some physiological parameters, performance, and carcass and meat pH in broiler chickens, raised at different stocking densities. A total of 60 one-day-old Ross 308 broiler chicks were randomly assigned to four treatment groups based on stocking density (12 birds/m2 or 18 birds/m2) and 50 mg/kg body weight quercetin treatment (quercetin-treated or untreated).
Quercetin was administered per os once daily for 28 consecutive days at 18:00 h. The stocking density of 12 birds/m2 was categorised as low stocking density (LSD) condition while 18 birds/m2 represented high stocking density (HSD) condition. The circadian cloacal temperature was recorded at 2 h interval, three times, one-week apart on days 22, 29 and 36 while the haematological profile and erythrocyte osmotic fragility (EOF) were recorded on days 28, 35 and 42.
Broiler performance was recorded daily. The carcass characteristics and meat pH was determined at the end of the study period. Fluctuations in diurnal cloacal temperature (CT) showed that increasing stocking density induced an elevation (P < 0.05) in the overall mean CT of untreated HSD group (40.96 ± 0.02 ºC) while the CT was lower (P < 0.05) in the treated HSD group (40.72 ± 0.02 ºC). The CT of the untreated LSD group (40.88 ± 0.02 ºC) was lower (P < 0.05) when compared with the untreated HSD group (40.96 ± 0.02 °C). On day 28, the total white blood cell count (TWBC), heterophils and H:L ratio (8.50 ± 0.67 x 109/L, 1.35 ± 0.30 x 109/L and 0.19 ± 0.03 respectively) were significantly lower (P < 0.05) in the quercetin-treated HSD group when these parameters were compared with those of the untreated HSD group (12.36 ± 1.22 x 109/L, 3.91 ± 0.79 x 109/L and 0.53 ± 0.13 x109/L respectively). The overall mean variation in percentage erythrocyte osmotic fragility (EOF) was significantly higher (P < 0.05) at 0.5 %, 0.3 % and 0.1 % NaCl concentrations in the quercetin-treated LSD group with corresponding values of 10.29 ± 6.09 %, 67.41 ± 3.30 % and 88.93 ± 3.47 % respectively, while the EOF was 0.24 ± 0.16 %, 62.21 ± 4.22 % and 85.50 ± 3.56 % in the untreated LSD group. HSD condition caused a higher (P < 0.05) erythrocyte osmotic fragility at 0.5 %, 0.3 % and 0.1 % NaCl concentration. The final live body weight (1,344.0 ± 54.22 g) and weight gain (1,120.0 ± 52.48 g/chick) of quercetin-treated HSD was significantly higher (P < 0.05) when compared with the final live body weight (1,071.0 ± 60.76 g) and weight gain (842.50 ± 57.07 g/chick) of the quercetin-treated LSD group. The feed conversion ratio was significantly lower in the quercetin-treated HSD group (1.43 ± 0.07) when compared with untreated HSD (1.79 ± 0.10), LSD (2.20 ± 0.10) and quercetin-treated LSD (2.10 ± 0.12) groups. A higher viability ratio was recorded in the quercetin-treated groups. Quercetin administration had a weight-enhancing effect, correlated directly with the increasing age of broiler chicks in quercetin-treated HSD (r = 0.950; P < 0.01) and quercetin-treated LSD (r = 0.968; P < 0.01) groups. Low stocking density condition and quercetin administration enhanced meat quality by preventing early rise in pH. This is beneficial to consumers that may wish to refrigerate meat for future consumption. The results suggest that quercetin was most beneficial in conditions of discomfort and, may, be useful as a supplement in broiler chicken production, especially in stress due to HSD. It was concluded that the administration of quercetin at 50 mg/kg body weight enhanced performance through efficient feed utilisation, alleviated stocking density-induced social and physiological stress and prolonged the shelf-life of stored broiler breast meats.
