This study investigated the effects of regular visual contact at various ages on tonic immobility (TI) and heterophil/lymphocyte ratio (HLR) reactions to handling and crating, antibody production, growth performance, and feed conversion ratios in commercial broiler chicks. Broiler chicks were exposed to (1) visual contact with an experimenter for 10 min twice daily from 0 to 3 weeks (V0-3), (2) visual contact with an experimenter for 10 min twice daily from 0 to 6 weeks (V0-6), (3) visual contact with an experimenter for 10 min twice daily from 3 to 6 weeks (V3-6) and (4) no visual contact (NV), as control. At 42 days of age, the birds were captured and crated for 10 min. Following, the 10 min crating, the V0-3 and V0-6 birds had shorter TI duration and lower HLR than those of NV. Although, the HLR response of V3-6 birds to crating were similar to their V0-3 and V0-6 counterparts, the latter two groups were less fearful, as measured by TI duration. Subjecting birds to V0-3 and V0-6 enhanced antibody response to Newcastle disease vaccine. Regular visual contact had negligible influence on body weight, feed conversion ratios and survivability of birds. Collectively, the results suggest that regular visual contact from 1 to 21 days of age is sufficient to reduce fear and stress reactions to handling and crating, and improve antibody response in broiler chickens.

We examined the effects of early age feed restriction and heat conditioning on heterophil/lymphocyte ratios (HLR), heat shock protein (hsp) 70 expression and body temperature of heat-stressed male broiler chickens. On day (d) 1,chicks were subjected to (1) 60% feed restriction on d 4, 5, and 6 (FR); (2) exposure to 36±1°C for 1 h from d 1 to 21 (HT); (3) both FR and HT (FRHT); or (4) control. On d 35, all the birds were exposed to 39±1°C for 6 h. Subjecting chicks to FR, HT and FRHT reduced HLR response to the heat challenge. The FR and FRHT birds had improved hsp 70 response and the latter were more hyperthermic than controls during the heat exposure.

The effects of early age feed restriction and heat conditioning on heat shock protein (HSP) 70 expression, antibody production, resistance to infectious bursal disease (IBD), and growth of heat-stressed male broiler chickens were investigated. Chicks were divided into 4 groups: 60% feed restriction on d 4,5, and 6 (FR); exposure to 36 +/- 1 degrees C for 1 h from d 1 to 21 (HT); combination of FR and HT (FRHT); and control. From d 35 to 50, heat stress was induced by exposing birds to 38 +/- 1 degrees C and 80% RH for 2 h/d. On d 36, each bird was administered 10 times the normal dose of live IBD vaccine. After heat exposure, the FRHT birds had higher HSP 70 density (d 41) and weight gain (from d 35 to 49) and lower bursal histological score (BHS) (d 51) than their HT and control counterparts. The HSP 70 expression and BHS of FR birds were not significantly different from those of the other 3 groups during the heat exposure period. Heat shock protein 70 and BHS data were negatively correlated (r = -0.33, P = 0.0008). We concluded that FRHT could improve weight gain and resistance to IBD in male broiler chickens under heat stress conditions. The improved heat tolerance and disease resistance in FRHT birds could be attributed to better HSP 70 response.