Physiological response of chickens to heat stress measured by radio telemetry

Effects of electrolyte and lighting regimen on growth of heat-distressed broilers

The purpose of this study was to investigate possible interactions between photoschedules [23 h light (L):1 h dark (D); 16L:8D] and electrolytes provided by KCl and NaCl in the drinking water of broilers grown at elevated temperatures. Birds raised on each photoschedule were exposed to 8 h of 23.9 C, 4 h of 23.9 to 35 C, 4 h of 35 C, and 8 h of 35 to 23.9 C. Photoschedule had no effect on body weight gain, feed consumption, or carcass characteristics. Male birds that received NaCl gained 10.5% more (P < .05) weight than those receiving no water additive. Male birds consumed up to 37% more water (P < .05) and gained up to 21% more weight (P < .05) than similarly raised females. There was no effect of electrolytes on carcass characteristics.

Performance and immunity of heat-stressed broilers fed vitamin- and electrolyte-supplemented drinking water

The efficacy of different vitamin and electrolyte treatments of drinking water for heat-stressed broilers was studied in two experiments. In Experiment 1, commercial broilers (50% male, 50% female, sexed), were subjected to four drinking water treatments: 1) unsupplemented water (control); 2) B-vitamins plus electrolytes (B+E1); 3) vitamins A, D, and E, B-vitamins plus electrolytes (ADEB+E1); and 4) vitamins A, D, and E and B-vitamins (ADEB). Each treatment group was replicated in eight pens containing 70 birds. All birds were provided ad libitum access to feed through to 43 days of age and subjected to the water treatment from 16 to 21 days and 38 to 43 days. The birds were exposed to the 35 C ambient temperature during the last 72 h of each period. Immune function was tested on the males in each pen while they received the water treatments from 24 to 34 days of age. In comparison with the control, feed conversion was improved 5.6% by ADEB+E1 and ADEB, and body weight gain was improved 6.7% by ADEB (P less than .05). Total and IgG antibody response against SRBC after primary immunization was improved by B+E1; whereas, B+E1 and ADEB treatments improved IgG after secondary immunization. The highest numbers of Sephadex-elicited peritoneal macrophages were found among ADEB-treated birds, but neither adherence nor phagocytic ability of macrophages from either group was affected. Natural killer cells from all except ADEB+E1-treated birds exhibited comparably high tumoricidal activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Caloric value of cardiac response to hot environments

Single Comb White Leghorn hens were placed in a controlled temperature chamber, initially at 26 C and subsequently raised to 35 C. Recordings of the surface and rectal temperatures, respiratory rate, heart rate, and oxygen consumption were made at the 26 C basal temperature and compared with those made at the 35 C ambient temperature. Sequential doses of saline and atropine were injected following the thermoregulatory response of birds to 35 C. The thermal challenge resulted in an average increase of 53 breaths per minute in the respiratory rate during the pre-injection period at 35 C and rose steadily to the end of the thermal challenge. The saline elicited no effects on any parameter measured; however, the atropine resulted in a mean increase of 62 beats per minute in the heart rate. There was no difference in the pre-atropine heart rate at 35 C and the basal heart rate at 26 C. Following the atropine induced increase in heart rate there was a 13% increase in energy expenditure. Thermal-bradycardia in hot environments may represent a first line of defense against hyperthermia by reducing the added heat load.

Electrocardiographic and respiratory responses to viscerotropic and neurotropic strains of Newcastle disease virus measured by radio telemetry

Two groups each of White Rock chickens from 6 to 23 weeks old were monitored by radio telemetry to determine their electrocardiogram and respiration response after they were infected with either a velogenic viscerotropic isolate of Newcastle disease virus (VVND) or the neurotropic GB strain of Newcastle disease virus (NGB). Significant changes were found in the heart rate, R wave amplitude, ST segment elevation, T wave amplitude, RS complex interval, ST segment duration T wave interval, TP segment duration, PR segment duration and TP interval of the birds infected with VVND, but no significant ECG changes were found in the birds infected with NGB. There were no significant changes in respiration rate in any birds.