Influence of temperature and humidity manipulation on chicken embryonic development

Abstract

Background: Temperature and relative humidity (RH) are very important factors affecting embryo development, hatchability, and posthatch performance. This study aimed at characterizing embryonic metabolic and behavioural response to a harsh incubation environment generated by manipulations (elevations and drops) in these two key factors. This study was aimed at establishing patterns of metabolic and behavioural response, as well as mortality and the development of malformations, all of which can potentially be used in monitoring incubating operations and diagnosing problems with faulty equipment.

Results: Of all the parameters monitored throughout embryonic development the ones shown to be most affected were: albumen-weight to egg-weight ratio (AR); yolk-weight to egg-weight ratio (YR); embryo-weight to egg-weight ratio (ER); heart rate (HR); voluntary movements per minute (VMM); mortality rates; malformation prevalence and type. The most significant changes in the evolution of AR and YR throughout incubation involved delay and reduction in the amplitude of the expected drop in albumen and yolk levels, reflecting lower nutrient consumption by the embryo. ER tended to grow more slowly and remain lower than the established normal, especially in embryos challenged with temperature treatments. HR and VMM were considered to be strong indicators of embryonic stress, as all treatments applied resulted in elevated heart rate and decreased embryo movement. Mortality rates for both temperature-related treatments were higher during the first four days of incubation. Changes in relative humidity have produced less radical effects on mortality. Malformation rates were higher for embryos subjected to high incubation temperatures and were most prominently related to the abdominal wall, head, skull and limbs. Overall, manipulations in environmental (incubator) temperature during incubation produced more drastic changes in embryo development than humidity-related manipulations, especially where mortality and malformation rates were concerned.

Conclusions: This paper describes changes in embryonic metabolism and behaviour, as well as in mortality and malformation rates, in response to manipulations in environmental temperature and relative humidity. Together with further studies, these patterns may prove helpful in the diagnosis of equipment malfunctions relating to temperature or relative humidity.

Figure 1

Evolution of the albumen -to- egg- weight ratio throughout incubation. Evolution of the ratio of total albumen weight in proportion to egg fresh weight throughout twenty days of incubation (values displayed are the average for each sample of viable eggs per day of sampling).

Figure 2

Evolution of the yolk- to- egg- weight ratio throughout incubation. Evolution of the ratio of yolk albumen weight in proportion to egg fresh weight throughout twenty days of incubation (values displayed are the average for each sample of viable eggs per day of sampling).

Figure 3

Evolution of the embryo- to- egg- weight ratio throughout incubation. Evolution of the ratio of total embryo weight in proportion to egg fresh weight throughout twenty days of incubation (values displayed are the average for each sample of viable eggs per day of sampling).

Figure 4

Embryonic heart rate throughout incubation. Average embryonic heart rate for each sample of viable embryos per day of sampling, as detected via candling and visual inspection from days 0–5, and via digital heart rate monitor from day 6 onward.

Figure 5

Voluntary movements per minute throughout incubation. Average voluntary embryonic movements for each sample of viable embryos per day of sampling, as detected via candling and visual inspection.

Figure 6

Mortality distribution for each treatment according to incubation period. Mortality curves for each treatment throughout 20 days of incubation. Values are displayed as percentage of embryos dead at each day of incubation (time of death established by visual inspection of the embryo and comparison with normal embryos) per total of fertile eggs incubated.

Figure 7

Malformation rates by treatment and by organ/ tissue affected. On the left: Percentage of malformation occurrence by treatment. Values are displayed as percentage of embryos carrying one or more malformations per total of fertile eggs incubated. On the right: Percentual distribution of systems, organs and tissues prefferentially affected by malformations, in relation to each of the treatments applied.