Abstract

---

The study investigates effects of feed withdrawal time on stress indices in broilers. Ross 308 broilers (n=10), aged 6 weeks were obtained from a commercial farm and transported to KNUST-Kumasi. The birds were placed in pens and provided water ad-libitum but without feed. Sample of birds (n=2) were withdrawn randomly on arrival and every 4 hours following feed withdrawal (0 hours, 4 hours, 8 hours, 12 hours and 16 hours) corresponding to 4pm, 8pm, 12am, 4am and 8am. Blood samples were drawn from the brachial veins under the wings of the two birds using a syringe and pooled together into an evacuated heparinized tubes with EDTA and Serum. The EDTA tubes were shaken to prevent coagulation of the blood. The blood samples were stored at 4°c and analysed at the Clinical analysis laboratory, KNUST for the concentrations of hormones: triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormones (TSH) as indicators of stress. The T3/T4 ratios were calculated. Relationships between blood thyroid hormone levels and feed withdrawal time impact on body weight were established. The results showed a decrease in T3 and T4 concentration during the first four hours. After the 4 hours T3 rapidly increased and after 8 hours feed of withdrawal it decreased sharply. The T4 gradual increased may indicate increased stress and perhaps preparation for conversion of T4 to T3, the active form of the hormone to increased metabolism to compensate for increasing feed withdrawal loss. The T3/T4 ratio and TSH of 1.71 and 0.1 was highest and lowest respectively at 8 hours. There was high positive relationship between feed withdrawal time and T4 concentration (Y=0.5275x+5.94, R² = 0.7431). Body weight decreased with increasing T4 concentration (y = -0.0469x+2.2535R² = 0.45). As T4 increases following feed withdrawal, body weight reduces by 4.6%. The study revealed that feed withdrawal duration of 16 hours leads to 44.9% decrease in body weight of broilers. It appears that beyond 8 hours of feed withdrawal birds were physiologically stressed and could be subject to negative welfare conditions which leads to body weight loss and reduced meat yield

---