Thermal stress effects on certain blood characteristics of adult male turkeys

Cloacal and surface temperatures of tom turkeys exposed to different rearing temperature regimes during the first 12 weeks of growth

Years of genetic selection have caused an increase in growth rate and market body mass in agricultural poultry species compared to earlier genetic strains, potentially altering their physiological requirements. The objective of this study was to expose Hybrid Converter tom turkeys on a weekly basis to the recommended rearing temperature regime (TCON: control) or 4°C below the recommended standard (TTRT: treatment) to determine their thermal responses. Once per week for 12 weeks, 12 turkeys were individually exposed to either TCON or TTRT for a 2-h period. Surface temperatures of the breast (TBREAST), wing (TWING), drumstick (TDRUM), head (THEAD), and shank (TSHANK) were measured at 20-min intervals using an infrared camera, while a thermal data logger measured the skin surface temperature under the wing (TLOGGER) at 30-s intervals. The cloacal temperature (TCORE) was measured using a medical thermometer at the start and end of the exposure period. Regardless of exposure temperature, the TBREAST (TCON: P<0.001 and TTRT: P<0.001), TWING (TCON: P<0.001 and TTRT: P<0.001), and TDRUM (TCON: P<0.001 and TTRT: P<0.001) decreased from weeks 4 to 6 and remained constant from weeks 1 to 3 and 8 to 12. THEAD was elevated in week 2 (TCON: P<0.001) or week 3 (TTRT: P<0.001), TSHANK increased slightly during week 3 for both TCON (P<0.001) and TTRT (P<0.001), and TLOGGER (TCON: P<0.001 and TTRT: P=0.001) and TCORE (TCON: P<0.001 and TTRT: P<0.001) were lower during the first week. Thereafter, THEAD, TSHANK, TLOGGER, and TCORE remained constant. Exposure to TTRT resulted in lower TBREAST, TWING, and TDRUM compared to TCON. Generally, THEAD, TSHANK, TLOGGER, and TCORE were not affected by the different exposure temperatures. The data demonstrated that the degree of thermal response expressed is dependent on the location of measurement, age, and exposure temperature.

Interrelationship between environmental temperature and dietary nonphytate phosphorus in chicks

Four levels of nonphytate P (NPP; 0.2, 0.3, 0.4, and 0.5%; total P = 0.46, 0.56, 0.66, and 0.76%) and two temperatures (25 and 37 degrees C) were evaluated in chicks from 8 to 22 d. In experiment 1, crossbred male chicks (New Hampshire x Columbian) housed at 25 degrees C increased weight gain at all increasing NPP levels, but chicks exposed to 37 degrees C did not show increased weight gain beyond 0.3% NPP. In experiment 2, environmental temperature was not increased until d 15. Weight gain of crossbred male chicks fed the 0.2% NPP diet was similar at both temperatures, but chicks exposed to 37 degrees C had lower weight gains than chicks housed at 25 degrees C for all other NPP levels. On d 22 to 24, chicks that had been housed at 25 degrees C and fed 0.2, 0.3, and 0.5% NPP were moved to the 37 degrees C chamber to evaluate heat stress on older chicks. Chicks fed the 0.2% NPP diet showed 35% mortality within 6 h. In experiment 3, both male commercial (Ross x Ross) and crossbred chicks that had been housed at 25 degrees C and fed 0.2% NPP from 8 to 22 d showed increased signs of severe heat distress when exposed to 37 degrees C on d 22. Our results suggest that the NPP requirement for growth of 8-to-22-d-old chicks may be reduced by high temperature. However, a NPP deficiency may result in increased mortality or severe heat distress in older chicks that are exposed to an acute increase in temperature.

Effects of ambient temperature, arginine-to-lysine ratio, and electrolyte balance on performance, carcass, and blood parameters in commercial male turkeys

The effects of ambient temperature (T; 15 C vs. 30 C from 6 wk of age onwards), dietary Arg:Lys ratio (Arg:Lys ratio; 1.00 vs. 1.25), dietary electrolyte balance (DEB: 164 vs. 254 meq/kg), and their interactions on growth performance and carcass yields of male turkeys were studied. The experiment was designed as a split plot, including T x DEB as the main plot and Arg:Lys ratio as the sub-plot, with 24 pens containing 35 male turkeys each. Feed consumption, BW gain, mortality, and processing yields were measured. Temperature had a clear effect on performance during all age periods. Feed intake was significantly lower for the high T group compared with the low T group (322.7 vs. 432.3 g/bird per day; P < 0.001). Consequently, BW gain during the experimental period (28 to 140 d of age) was significantly lower for the high T group compared with the low T group (14.54 vs. 18.74 kg; P < 0.001). Feed:gain during the period of 28 to 140 d of age was significantly lower for the high T group compared with the low T group (2.51 vs. 2.61; P < 0.001). The high dietary Arg:Lys ratio increased feed intake significantly until 56 d of age (200.6 vs. 197.6; P < or = 0.034). A high Arg:Lys ratio resulted in significantly higher BW gain until 98 d of age (10.03 vs. 9.84 kg; P < or = 0.024). The Arg:Lys ratio did not affect feed:gain throughout the experiment. Dietary electrolyte balance did not affect performance parameters. No consistent two- or three-way interactions were observed. Processing yields were only affected significantly by T, and not by Arg:Lys ratio or DEB main effects. High T resulted in lower cold carcass (73.2 vs. 74.9%) and breast meat yields (33.5 vs. 36.0%), and higher thigh (18.9 vs. 18.1%), drumstick (14.5 vs. 13.2%), and wing yields (11.7 vs. 10.6%) compared with low T. We concluded that growth performance is compromised by higher T, and altering the Arg:Lys ratio or DEB does not alleviate this impaired performance. Dietary Arg levels seem to be important when dietary Lys is marginal relative to the requirement.

Effects of food and water withdrawal and high temperature exposure on diurnal variation in blood viscosity of broiler chickens

1. Three experiments were conducted to investigate the diurnal variation of blood viscosity in broilers. In experiment 1 food and water were supplied freely at 20 degrees C (20-FW). In experiment 2 food and water were withdrawn at 20 degrees C (20-NFW), while in experiment 3 food and water were withdrawn at 30 degrees C (30-NFW). 2. Blood sampling time points were 09.00 h, 15.00 h, 21.00 h, 03.00 h and 09.00 h the next day in each experiment. 3. In all experiments, whole blood viscosity (WBV), red blood cell count (RBC) and haematocrit (HCT) were greater during the dark (21.00 h and 03.00 h) than during the light period. During the dark period, there were no differences in WBV, RBC and HCT between 20-FW and 20-NFW, or between 20-NFW and 30-NFW. At 09.00 h, WBV and HCT were higher in 20-FW than in 20-NFW. At 15.00 h and 09.00 h (day 2), WBV and HCT were greater in 20-NFW than in 30-NFW. 4. There were no light-dark differences in plasma viscosity (PV), plasma protein concentration (PPC) or mean corpuscular volume (MCV) in any experiment. However, 20-NFW birds had a lower PPC and higher MCV compared with 20-FW, and a higher PPC and lower MCV compared with 30-NFW, while no difference was found in PV. 5. WBV increased linearly with RBC and HCT. PV increased with PPC, while MCV decreased. 6. These results indicate that there is diurnal variation in whole blood viscosity, which is greater during the dark than during the light period. During the light period it is strongly influenced by high environmental temperature and food and water withdrawal.

Effect of fasting and acute heat stress on body temperature, blood acid-base and electrolyte status in chickens

1. The tolerance of chickens to acute heat stress, evaluated by the time required to reach the critical body temperature (Tr) of 44.5 degrees C, was markedly enhanced as the period of fasting was extended. 2. Fasting reduced the rates of heat-induced changes in blood acid-base and electrolyte status. 3. Changes in Tr were correlated with changes in blood pH, pCO2, [Cl-] and [Pi] but not with changes in [Na+] or [K+]. 4. Blood acid-base and electrolyte status were related to Tr rather than time of exposure to heat stress.

High chronic ambient temperature stress effects on broiler acid-base balance and their response to supplemental ammonium chloride, potassium chloride, and potassium carbonate

Four experiments were conducted to evaluate the effect of heat stress on acid-base status and the birds' response to supplemental KCl and KCO3. The corn-soybean meal fish-meal basal ration (.73% K+) contained more K+ and Cl- than is recommended by the National Academy of Sciences for chicks reared under near optimal conditions (24 C and 55% relative humidity). Chicks reared under continuous thermostress (35 C, 70% relative humidity) exhibited panting phase blood alkalosis (pH of 7.46). Supplementing drinking water with .2% NH4Cl reduced panting phase blood pH to normal values and increased live weight gain (23%) and feed efficiency (7.7%). Supplementing drinking water with .15% KCl also increased (P less than .05) live weight gain (46%) and feed efficiency (15.4%) but did not affect (P less than .46) blood pH. A significant (P less than .01) interaction existed between NH4Cl and KCl for body weight gain. Adding .2% NH4Cl to broiler drinking water reduced the level of KCl required in drinking water to optimize weight gain to .1% KCl. Potassium chloride alone, or with NH4Cl, can alleviate some consequences of heat stress, but supplementing drinking water with a high level of NH4Cl (.5%) decreased (P less than .05) blood pH to acidotic levels and reduced body weight gain. Potassium chloride supplementation exacerbated NH4Cl toxicity. Potassium carbonate reduced (P less than .05) body weight gain indicating that the response may not be attributed to K+ alone. Beneficial effects of NH4Cl therapy for heat stressed broilers are speculative.

Chronic heat stress and respiratory alkalosis: occurrence and treatment in broiler chicks

The occurrence of respiratory alkalosis and potential benefit derived from treatment were examined in thermostressed 4-week-old broiler chicks. Blood pH was greater (P less than .05) in heat-stressed (32 C) panting birds (7.395) than either nonpanting (7.28) or birds raised at 24 C (7.28). Acute thermostress, obtained by elevating ambient temperature from 32 to 41 C over a 20-min period further elevated (P less than .05) blood pH to 7.521. Chronic heat-stressed broiler chicks suffer from intermittent respiratory alkalosis during panting; with acute heat stress, chicks pant continuously and suffer from alkalosis. Including .5% sodium bicarbonate (NaHCO3) in the diet of birds subjected to chronic heat stress enhanced body weight gain by 9% even though it tended (P less than .10) to increase blood pH in nonpanting birds. Adding .3 or 1% ammonium chloride (NH4Cl) to diets decreased blood pH (P less than .01) to 7.194 and increased (P less than .05) body weight gains by 9.5 and 25%, respectively. Effects appeared linear with NH4Cl dose to 1% NH4Cl, but 3% NH4Cl elevated weight gains by only 8% and precipitated blood acidosis (pH 7.09) in nonpanting birds. Supplementing the 1% NH4Cl diet with .5% NaHCO3 increased weight gains an additional 9%. Manipulating sodium: chloride ratios by addition of calcium chloride increased body weight gain 8% and slightly reduced severity of alkalosis. Data indicate that blood alkalosis limits growth rate of broiler chicks reared under chronic thermostress and that the respiratory alkalosis and weight gain depressions attributed to thermostress can be partially alleviated dietarily.