Introduction

Guinea fowl rearing was only a sporadic rural occupation of weaker sections in many states of India. Guinea fowl is a promising genetic resource for evolving a low input grain saving poultry alternative for production in the developing world. Attractive plumage of the guinea fowl and its value as a table bird with high meat to bone ratio and game type flavor has led global acceptance (Embury, 2001). Birds are semi domesticated; well thrive under semi-captive conditions in hot and cool climates, relatively disease-free and need very little care. Guinea fowls are kept for both meat and egg productions. There are hardly any cultural barriers against consumption of guinea fowl products (Saina et al., 2005). White breasted guinea fowl is a strain developed from the common Pearl guinea fowl and this bird is being widely accepted among guinea fowl farmers due its size and laying capacity. Guinea fowl breeding hens produce thicker shelled eggs in comparison to that of a regular chicken. Kusina et al. (2012) reported the aaverage productivity indices of guinea fowl are 8 birds per flock, 89 eggs/hen, 64% hatchability and 60% of keet survival rate. An eggshell makes up 15% of the total weight of the guinea fowl egg which is 9% of that of a regular chicken egg (Yildirim, 2012). Various pre-incubation and storage practices for hatching eggs have considerable influence on the hatching results, chick quality and their performance afterwards. Kingori (2011) have stated that fertility and hatchability are two major parameters that highly influence the supply of day-old chicks. The storage periods of different days could influence the incubation characters of guinea fowl. The present study was therefore conducted to observe the effect of storage period on hatchability under specific temperature and humidity.

Materials and Methods

Hatching eggs from guinea fowls of 32-35 weeks of age, reared on deep litter were collected twice a day and fumigated. These eggs were categorized into three different storage periods of zero, four and eight days. Zero day storage eggs, were transferred to the forced draft automatic chicken incubator immediately after egg collection, while the other two groups were transferred to the egg storage room maintained at 18°C with 75–80 percent relative humidity. Four and eight day’s storage category was transferred on the respective days to the setter for incubation. Total number of hatching eggs set under zero, four and eight days are 338, 322and 342 respectively. The temperature and relative humidity in the setter and hatcher were maintained at 37.5±0.3°C and 60%; and 37.0°±0.3°C and 70% respectively. The eggs in the setter were turned by 45° angle on either side at hourly interval until they were transferred to the hatcher. After 24 days of incubation, the eggs were transferred from setter to hatcher and eggs were placed in pedigree boxes treatment wise to record the respective fertility and hatchability. Fumigation was carried out at 1x concentration at the 25^th day, immediately after transferring the eggs to the hatcher. The hatch was taken on day 28. Other standard hatchery sanitation procedures were followed uniformly throughout the experiment.

Hatchability

Hatchability was computed as per the following formula;

Total no. of healthy Guinea fowl chicks

Percent Total Hatchability = ——————————————— X 100

Total no. of Guinea fowl eggs set

Total no. of healthy Guinea fowl chicks

Percent Fertile Hatchability = ——————————————— X 100

Total no. of fertile Guinea fowl eggs

The collected unhatched eggs were broke open at their broad end and checked for any changes. It was considered that eggs without any visible growth or changes as infertile, a dark spot on yolk with area of pellucida and area opaca as early embryonic mortality, a fully grown embryo with feathers that had not hatched as dead-in-shell and rest with visible growth as late embryonic mortality. All the statistical analyses were performed by using SPSS (IBM Corp. Release 2011) software (version 20.0). Results were expressed as the mean± S.E., and in all applications (ANOVA) the differences were considered statistically significant at P< 0.05 and highly significant at P<0.01.

Results and Discussion

Hatchability and embryonic mortality of Guinea fowl eggs observed in three system of rearing is presented in Table 1 and the effect of rearing system on the type of embryonic mortality is furnished in Fig.1.

Table 1: Effect of storage period on hatchability and embryonic mortality in guinea fowl

** = Highly Significant (P <0.01); * = Significant (P<0.05); ^NS = Non Significant; ^{a, b, c} = Mean values bearing different superscripts in a row differ significantly

The per cent hatchability for total eggs set was significantly (P<0.01) higher for zero day (59.43% ± 0.40) followed by four days (55.28% ± 0.18) and eight days storage (51.28% ± 0.61). However, the per cent hatchability of fertile eggs set was comparable for zero and 4 days storage, with eight days storage showing a significantly lower (P<0.01) hatchability. Overall hatchability and fertile hatchability in guinea fowls were 55.28% ± 1.04 and 80.71% ± 1.10 respectively.

Fig. 1: Effect of storage period on embryonic mortality and type in guinea fowl

Highly significant (P<0.01) variations were observed between storage period in early and late embryonic mortality. Early and late embryonic mortality was significantly (P<0.01) low in zero day stored eggs. No significant variation was observed between treatments for dead-in-shell or weak chicks. The overall percent early, late embryonic mortality and dead-in-shell were 9.63% ± 0.30, 6.21% ± 0.22, 2.09% ± 0.38, respectively.

Hatchability

Results on the influence of hatchability of storage period on guinea fowl eggs revealed that there was a significant (P<0.01) reduction in hatchability as the storage period increased. Maximum hatchability was observed on zero day (59.43% ± 0.40) of storage and minimum at eight days (51.28% ± 0.61) of storage.

A negative correlation between hatchability and storage period was observed in the present study and it is in agreement with the findings of Ayorinde (1987), Binali and Kanengoni (1998), Nwagu and Alawa (1995), Moreki and Ditshupo (2012), Brah et al. (1989) and Carole (2009) in Guinea fowl. In a similar way Petek et al (2003), Seker et al. (2004), Mani et al. (2008), Ramao et al. (2008) and Mahmud et al. (2011) also observed reduction in hatchability as the storage period increased in quail and broiler breeder respectively.

Gas exchange occurs through the pores in the egg shell during storage. Carbon dioxide diffuses out of the egg and its concentration declines rapidly during the first 12 hours after the egg is laid. Eggs also lose water vapour while in storage and this loss of both carbon dioxide and water contributes to the loss in hatchability and chick quality when storage is prolonged.

Embryonic Mortality

Guinea fowl eggs stored for zero day had significantly (P<0.01) low percent of early and late embryonic mortality while egg stored for eight days had highest early embryonic mortality, eggs stored for four days had significantly (P<0.01) high late embryonic mortality. No significant difference was noticed in dead in shell between the three treatments. Shorter storage time had lowered early and late embryonic mortality and this agrees with findings of Murial and Serrano (2007) in guinea fowl, Khan (2007) in Fayoumi chicken and Ipek et al. (2007) in pheasants. No significant difference was noticed in dead-in-shell, but numerically percent dead in shell was higher in zero day storage. This disagrees with the finding of Moreki and Ditshupo (2012) and partially with Moreki and Mack (2013).

Conclusions

Egg storage is a logistical necessity for the hatching egg industry both at the breeder farm and at the hatchery. However, it is well known that as the egg storage prolong, it negatively influences hatchability. Embryos of egg stored long term can be affected such, that they do not initiate growth after proper incubation temperatures are provided or they initiate growth, but grow at a slower rate than eggs stored short term or they could be affected both ways. It can be concluded that the hatchability on total and fertile eggs set was maximum (59.43% ± 0.40 and 84.07% ± 0.14) for zero day stored eggs, while it was the lowest (51.28% ± 0.61 and 76.72% ± 2.00) for eight days stored eggs. The study was conducted keeping the fact in mind that, the storage period may lead loss of germ plasm of guinea fowl. Therefore, it might be concluded that after a certain period of stocking the hatchability tremendously affected by the storage period, which can be prevented by quick processing and early hatching.

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