Effect of relative humidity on incubation of Japanese quail eggs

J M Romao*, T G V Moraes*, R S C Teixeira*, C Buxade** and W M Cardoso* 

* Laboratório de Estudos Ornitológicos - Universidade Estadual do Ceara

** Escuela Técnica Superior de Ingenieros Agrónomos, Universidad Politécnica de Madrid

josueromao@yahoo.com.br

Abstract 

This research aimed to verify the effect of relative humidity during incubation of Japanese quail eggs on hatchability, egg weight loss, hatch weight, and embryo mortality. A total of 150 Japanese quails (Coturnix japonica) were used for egg collections. The eggs were divided into three experimental groups: low humidity group (36.05±6.06% RH; n=100), intermediate humidity group (52.25±4.99% RH; n=100) and high humidity group (76.50±4.44% RH; n=100). Each group of eggs was incubated in an individual incubator, according to its experimental relative humidity during incubation. Incubation process was done by automatic incubators with temperature of 37.5°C, and egg turning every 30 minutes. At the 15^th day of incubation (360h) egg turning was stopped and the eggs were transferred to the hatcher that maintained the same temperature and relative humidity until hatch. All eggs were weighted on 1^st, 5^th, 10^th, and 15^th day of incubation and quail chicks at hatch.

Japanese quail eggs incubated at the lower humidity presented the highest level of hatchability (79%) compared to intermediate and high humidities. Egg weight loss was respectively 11.96%, 8.94%, and 4.89% for low, intermediate and high humidity groups. Futhemore, the weight at hatch was influenced by the different incubational humidities. Embryo mortality presented no statistical difference among the different humidity treatments.

Key-words: Coturnix japonica, egg weight loss, embryo mortality, hatch weight, hatchability

Introduction 

Japanese quail raising is an important poultry business in Brazil. The quails have been reared for both egg and meat production all over the country, mainly by small and medium breeders. Incubation procedures are important to maintenance and improvement of quail egg production in Brazil, which is increasing over the last years. One of the key points of incubation is the humidity control of incubators to allow a successful incubation performance.

Water accounts for 68.25% of total eggs mass before incubation (Martin and Arnold 1991). The amount of moisture lost from the eggs during incubation can affect hatchability (Lundy 1969) and chick weight (Burton and Tullett 1985).

During incubation, a certain amount of water must be around the embryos to protect them from drying out at an early stage of development (Yoshizaki and Saito 2002). Conversely, at a late stage of development, the drying of embryos is necessary to initiate air breathing (Bainter and Fehér 1974).

Usually 12 to 14% of water is lost during incubation of broiler and turkey eggs (Rahn et al 1981). Too low or too high water loss influences embryo development (Rahn and Ar 1974), and, consequently, egg hatchability (Meir et al 1984). The rate of water loss from eggs during incubation can be regulated through changes in incubator relative humidity (Peebles et al 1987; Tullett 1990).

The temperature can highly influence the relative humidity, and both contribute to water loss during incubation, this way temperature and humidity must be carefully monitored during incubation, because the embryo is not able to control the water loss of egg (Ar 1991).

The relationship between temperature and relative humidity was studied and standardized for duck (Cheng et al 2005), turkey (Applegate et al 1999) and broiler incubation (Van Brecht et al 2003), even though it was not sufficiently studied this relationship on Japanese quail incubation.

The objective of this research was verifying the effect of relative humidity during incubation of Japanese quail eggs on hatchability, egg weight loss, hatch weight, and embryo mortality.

Material and methods 

A total of 150 Japanese quails were used for egg collections. The birds were reared in experimental cages in the Laboratório de Estudos Ornitológicos- UECE and they were lodged at a ratio of two females and one male in each cage. The Japanese quails were 22 week old and averaged 90% of egg production. All quails were supplied with balanced feed, water ad libitum and 17 hours/day of light.

The eggs were collected and submitted to selection according to industrial parameters for egg incubation, verifying egg shape, extreme sizes and eggshell integrity by candling. They were divided into three experimental groups: low humidity group (36.05±6.06% RH; n=100), intermediate humidity group (52.25±4.99% RH; n=100) and high humidity group (76.50±4.44% RH; n=100). Each group of eggs was incubated in an individual incubator, according to its experimental relative humidity during incubation. Incubation process was done by automatic incubators with temperature of 37.5ºC, and egg turning every 30 minutes. At the 15^th day (360h) of incubation egg turning was stopped and the eggs were transferred to the hatcher which maintained the same temperature and relative humidity until hatch.

All eggs were identified, individually, and weighted with a precision balance (0.001g), on 1^st, 5^th, 10^th, and 15^th day of incubation. All quail chicks were weighted after hatching.

The eggs that failed to hatch were opened for macroscopically observation. Thus they were classified according to time of embryonic mortality. The eggs staged as infertile were the ones with true infertility or pre-incubation mortality. They were also staged as early dead embryos or intermediate dead embryos according to embryo mortality stage. Unhatched eggs classified as late dead were the ones with final stage mortality or pipped eggs with dead embryos.

A total of 300 eggs was divided into 3 experimental groups according to the humidity during incubation. Five replications of twenty eggs per group were followed for each experimental group and data were analyzed using the Statistix software 8.0 (2003). The results were submitted to Analysis of Variance through general linear model and the means egg weight loss and hatch weight were compared with the test of Tukey The means of hatchability and embryo mortality were compared using Kruskal Wallis test.. Statements of significance were based on p<0.05.

Results 

Figure 1 shows the fertile and total hatchability of Japanese quail eggs incubated at different relative humidities.

 Figure 1 shows that the group incubated in the lower humidity (36.05±6.06% RH) presented the highest levels of fertile and total hatchability and the group incubated with the highest humidity (76.50±4.44% RH) presented the lowest levels of hatchability. The group of eggs incubated in intermediate humidity (52.25±4.99%) had hatchability levels between the two other groups. The means of hatchability were statistically different just for fertile hatchability (p<0.05).

Table 1 shows the egg weight loss of Japanese quail eggs incubated at different relative humidities.

Japanese quail eggs incubated at different humidities presented different  rates of egg weight loss during the incubation, at the 5^th , 10^th and 15^th day (p<0.05). The weight loss was directly influenced by humidity during incubation. The eggs submitted to the high humidity treatment showed more than twice the weight loss of eggs incubated in low humidity. The weight loss of eggs incubated in the intermediate humidity was between the losses of the two other goups. The eggs averaged aproximately 0.797, 0.596, and 0.326% daily weight loss for low, intermediate and high humidity treatments, respectively.

Figure 2 shows the percentual ratio between chick weight at hatch and initial egg weight of Japanese quail eggs incubated at different relative humidities.

The heavier chicks were the ones which eggs presented the lower egg weight loss. The percentual ratio between Japanese chick weight at hatch and initial egg weight decreased as the experimental humindities increased. The real chick weights were 8.89±0.80, 8.77±0.86, and 9.47±082g for low, intermediate and high humidities. The chick weight in the intermediate humidity group was slightly smaller than the chicks from the low humidity group because the initial egg weight of the low humidity group (12.70 ± 0.88g) was higher than the egg weight of the intermediate humidity group (12.20 ± 0.90g).

Table 2 shows the classification of the Japanese quail eggs that did not hatch in each humidity group.

It was not found intermediate embryo mortality. Infertility or pre-incubational mortality is not affected by incubational humidity.

Japanese quail eggs incubated at low humidity (36.05±6.06% RH) presented lower rates of early and late embryo death. The eggs incubated at high humidity (76.50±4.44% RH) presented the highest rate of late embryo death. Despite de great numerical differences, the embryo mortality categories were not statistical different (p<0.05).

Discussion 

Hatchability

Lundy (1969) reported 50 to 60% RH to produce the best hatchability in chicken eggs, and it was also verified that the best hatchability rate is obtained when the egg weight loss is around 12%. Pedroso et al (2006) found 77.85% ± 7.38 and 75.28% ± 12.07 for Japanese quail eggs incubated at 55% RH and 65% RH, respectively. We verified different hatch rates for fertile eggs (p<0.05).

Egg weight loss

The egg weight loss is an important parameter for incubation. It has been used to estimate vital gas exchange (Paganelli et al 1978; Rahn et al 1979) and has been correlated with the rate of embryonic metabolism and development (Rahn and Ar 1980; Burton and Tullet 1983).

Ar and Rahn (1980) examined the loss of mass in eggs during incubation and evidences showed that this was essentially due to loss of water. About 10 to 11% of the water is lost in domestic fowl eggs during the incubation period (Tullett and Deeming 1987). The temperature can highly influence the relative humidity, and both contribute to water loss during incubation, this way temperature and humidity must be carefully monitored during incubation, because the embryo is not able to control the water loss of egg (Ar 1991).

Soliman et al (1994) found an egg weight loss of 11.32% in Japanese quail eggs incubated 37.5°C dry bulb and 30°C wet bulb (56% UR). We verified that the different humidities highly influenced the egg weight loss. It was observed that the eggs incubated in low humidity lost more than twice the egg weight loss of eggs incubated in high humidities.

Chick weight

The weight of chicks at hatch can be affected by several factors, including species, breed, egg nutrient levels, egg environment, egg size (Wilson 1991), weight loss during incubation period, weight of shell and other residues at hatch (Tullet and Burton 1982), shell quality and, incubator conditions (Peebles and Brake 1987). In this experiment the only parameter that varied was humidity, this way chick weight was mostly influenced by this condition. The different humidities promoted different rates of eggs weight loss which were inversely proportional to chick weight at hatch.

Bruzual et al (2000) reported that relative humidity inferior to 63% during incubation decrease chick weight. Small chicks have higher surface area to weight ratios and are therefore more easily dehydrated than larger chicks. Dehydration has been reported to be associated with higher mortality of chicks from young breeders (Wyatt et al 1985).

Embryo mortality

The water loss is one of the most important processes that cause embryonic death (Tiwary and Maeda 2005). Romanoff  (1930) reported that insufficient egg weight loss during incubation can reduce the gas exchange through the egg membranes promoting a decreased hatchability. In the other hand, Soliman et al (1994) suggested that early deaths are result of excessive weight loss in Japanese quail eggs.

It was reported that high RH (75-80%) increased mortality and a low RH (40-50%) lowered late embryo death of eggs laid by older hens (Robertson 1961; Bruzual et al 2000). Pedroso et al (2006) observed 18.56% of early embryo mortality of Japanese quail eggs incubated at 55% RH.

Acknowledgments 

The author (JMR) thanks the Fundação Cearence de Apoio à Pesquisa-FUNCAP for the grant support.

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Received 15 September 2008; Accepted 2 December 2008; Published 10 March 2009

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