Changes in Production Parameters, Egg Qualities, Fecal Volatile Fatty Acids, Nutrient Digestibility, and Plasma Parameters in Laying Hens Exposed to Ambient Temperature

Abstract

The present study was undertaken to investigate the impact of heat stress on nutrient digestibility and tibia and reproductive traits, and changes in laying performance, egg qualities, fecal volatile fatty acids, and plasma parameters in laying hens. One-hundred twenty 52-week-old laying hens were raised in three temperature-controlled facilities with constant humidity (50% RH), either normal temperature (LT; 22 • C) or heat stress considered being moderate (MT; 27 • C) or severe (HT; 32 • C) for 42 days. Feed intakes were consistently low (p < 0.01) in HT hens compared with those in LT or MT over the period of 42 days. Egg production kept markedly (p < 0.05) or numerically (p > 0.05) low in hens exposed to HT vs. LT or MT. Egg mass and egg weight were consistently low (p < 0.01) in hens exposed to HT compared with those raised under LT or MT. On the other hand, feed conversion ratio and frequency of dirty and cracked eggs were not significantly affected (p > 0.05) during the experimental period. HT-exposed hens consistently had lowered (p < 0.05) eggshell thickness and breaking strength, eggshell weight, and plasma Ca, P, and Mg levels compared with LT-or MT-treated hens. HT hens had lower (p < 0.01) relative oviduct weight and less number of large yellow follicles compared with those raised under LT or MT conditions at 42 days. Tibia traits measured at 42 days were not affected by any of heat treatments. Fecal volatile fatty acids tended to be higher in HT-exposed laying hens throughout the experiment. It was noted that digestibilities of neutral detergent fiber and dry matter were lowest (p < 0.05) in hens exposed to HT vs. LT or MT environments. Our study suggests that heat stress could lower laying performance, egg quality, and physiological parameters that are coupled with alterations in gut metabolites and mineral/lipid metabolism. The findings emerged from this study will help us design the nutritional and environmental strategies to mitigate the negative effect of heat stress on laying hens.

High Temperature With Low Humidity or Vice Versa Does Not Affect Performance and Physiology of Laying Hens

“…However, the earlier study reported that laying hens housed at 30ºC vs. 24ºC performed less and exhibited altered nutrient digestibility [20]. Similarly, we observed the negative effect of heat stress on laying hens when they were exposed to 32ºC vs 27ºC [21]. In addition, temperature and RH that were reached to target range (LH75 and HL75) maintained continuously throughout the experiment, which might be more stressful to hens than cyclic or intermittent regimes.…”

“…It is well known that laying hens exposed to heat stress lower feed intake to minimize heat production, and change blood flow from organs to body surface area to dissipate sensible heat [3]. In addition, heat stress impairs the ovarian function by lowering ovarian weight and number of large follicles [6,21,24].…”

The Impact of Temperature and Humidity on the Performance and Physiology of Laying Hens

“…However, an earlier study reported that laying hens housed at 30 °C had a poor performance and exhibited altered nutrient digestibility [ 23 ] compared to hens housed at 24 °C. Similarly, we observed a negative effect of heat stress on laying hens when they were exposed to 32 °C vs. 27 °C [ 24 ]. Thus, the selected response indicators (i.e., performance, egg quality, serum parameters, and stress indicators) could have been altered if temperature, but not RH, played an essential role in influencing the performance, behavior, or physiology of laying hens in this study.…”

“…It has been established that laying hens exposed to heat stress reduce feed intake to minimize heat production and change blood flow from the organs to the body surface area to dissipate sensible heat [ 4 ]. In addition, heat stress impairs ovarian function by lowering ovarian weight and the number of large follicles [ 7 , 24 , 28 ] as well as plasma concentrations of minerals, including calcium, magnesium, and phosphorus [ 24 ]. As observed in this study, none of the environmental treatments affected blood biochemical parameters, indicating that neither environmental regime affected heat stress’s physiological indicators in laying hens.…”

The role of corticosterone in the regulation of the cellular composition of chicken blood during the stress reaction

“…This affects the productive qualities of poultry, including growth processes, reproductive abilities and egg production, and product quality. [1,3,5,6], as a result of the predominant direction of the body's energy resources to the course of adaptation processes [7]. In addition, heat stress leads to an increase in the morbidity and mortality of poultry [8].…”