Effect of Progesterone Secretion on Egg Production in the Grey Helmet Guinea Fowl (Numida meleagris galleata)
The effect of progesterone (P4) on egg production was investigated
using twenty female guinea fowls raised on deep litter. The birds were
given feed and water ad-libitum. They were routinely bled by wing
jab between the hours of 9.00 and 10.00 am twice a month for P4
determination. Sera harvested from the samples were stored at -20°C
until assayed for P4 by Radio-Immuno-Assay method (RIA). Egg
production had a very high (p<0.001) and positive correlation with
progesterone level. A high value of coefficient of determination (R2
value) was observed, which implies that there is a high accuracy of prediction
of egg production from progesterone level.
The traditional source of animal protein include eggs, meat and milk.
One of the major sources of eggs in the rural parts of Nigeria is the
guinea fowl eggs. Its attractive plumage and value as a table bird with
game-type flavour and high meat to bone ratio has led to its worldwide
acceptance (Embury, 2001). They are widely consumed by a large number
of Nigerians because of the meat and egg which possess distinct flavour
and taste (Ayeni and Ayanda, 1982). However egg production is seasonal
in guinea fowls (Ogwuegbu et al., 1988). Sonaiya and Swan (2004)
also reported that Guinea fowl are seasonal breeders, laying eggs only
during the rainy season, under free-range conditions. This is because
successful poultry species instinctively lay and incubate their eggs at
a time of the year when newly hatched chicks will have a better supply
of high protein and energy food provided by the environment. Saina et
al. (2005) reported 5±1 months breeding season in Zimbabwe,
Southern Africa. The laying season in the flock of guinea fowls studied
were between October 2002 and March 2003.
Progesterone which is one of the most important steroid hormones affecting
reproduction in livestock and poultry has been reported to be positively
related to egg production in turkeys (Mashaly et al., 1979). Tanabe
et al. (1981) reported a positive correlation between circulatory
levels of progesterone and egg production in laying hens in pureline.
However, there is virtually no information on the effect of the progesterone
level on either production or reproductive traits in guinea fowls. In
this study, we have attempted to look at the progesterone levels in the
indigenous guinea fowl, throughout the year and correlate it with the
egg production. This is with the intention of using the information gathered
to attempt to break the seasonality of egg production as currently found
in the guinea fowls raised in Nigeria through a probable introduction
of exogenous source of progesterone to stimulate all year round egg production.
MATERIALS AND METHODS
This experiment was carried out at the Experimental Unit of the Poultry
Production Research Programme of National Animal Production Research Institute,
Ahmadu Bello University, Shika, Zaria. Shika is geographically situated
between latitude 11°12` N and longitude 7°33` E at an altitude
of 640 M above sea level (Akpa et al., 2002). It is located 22
km northwest of Zaria city and is vegetationally in the northern guinea
savannah zone of Nigeria. The Shika climate is characterized by a well
defined dry seasons. Details of Shika location, rainfall and climate has
been described by Kabir et al. (2006). Twenty native female guinea
fowls obtained from the local market were used in this study. The birds
were raised on deep litter at the poultry unit of National Animal Production
Research Institute of Ahmadu Bello University, Shika, Zaria. The birds
were provided with a layer ration containing 16% crude protein and 2,594
kcal ME kg-1 and water ad libitum. The experiment lasted
from January 2001 to December 2002.
Egg were collected within the hours of 12.00 to 1.00 pm and recorded
daily and the mean monthly production was recorded. The birds were routinely
bled twice a month via a wing jab using vacutainer needles and tubes between
the hours of 9.00 and 10.00 am. The serum samples were stored in a freezer
at -20°C until hormonal concentrations were determined by a Radio-immuno-assay
(RIA) technique (IAEA/FAO kit).
The procedure of general linear model of SAS Computer software package
(SAS, 1995) was used for the analysis of data generated in this study.
The model used for the is study is
Where Yij is the jth record of the ith month, μ is the
over all mean, mi is the effect of month and eij
is the random error assumed to be randomly and normally distributed with
expectation = 0.
The regression analysis to predict egg production from serum progesterone
level was also fitted using the following model
Where Yij is the egg production, a and b are the intercept
and slope, respectively and Xi is the guinea fowl`s serum progesterone
level and eij is the random error assumed to be randomly and
normally distributed with expectation = 0.
There was an increase in the progesterone level (Fig. 1 and Table 1)
during the months of June to August 1.05-1.16 ng mL-1. Egg
production commenced in this flock of guinea fowls towards the end of
April. The last few eggs were collected in September. The egg production
followed a similar trend with the highest total egg production of 250
recorded in August.
Egg production had a very high (p<0.001) and positive correlation
of 0.89 with progesterone level (p<0.001). A prediction equation was
also estimated for egg production using progesterone level as the predictor.
This equation is:
||Hormonal profile of the native guinea fowl kept on deep litter
||Progesterone (P4) level and monthly total egg production
by the native Guinea Fowl (Numidia meleagris galeata)
|The regression equation has an R-square value of 0.80.
The regression coefficient is highly significant (p<0.01).
There were seven months of egg production coinciding
with the raining season. This is similar to the report of Saina et
al. (2005) who reported 5 months of egg production among guinea fowls
kept semi intensively in Zimbabwe. It also supported the fact that guinea
fowls` egg production in Nigeria is limited to rain season (Saina et
al., 2005; Sonaiya and Swan, 2004). The increase in progesterone level
in the native guinea fowl coincides with an increase in egg production
during the months of June-September (breeding season). This is similar
to an earlier report on pheasant (Mashaly et al., 1979) and on
native guinea fowl (Ayorinde and Okaeme, 1984). Johnson and van Tienhoven
(1984) suggested that progesterone may directly regulate the fundamental
functions of growing follicular cells and ovulation. The current findings
in this study also indicates that progesterone is an important factor
in egg production in guinea fowl hens. This result supports the suggestions
of Bluhm et al. (1983) who noted that the cessation of egg laying
induced by stress was associated with low levels of progesterone and estradiol
in mallard ducks. Mashaly and Wentworth (1974) has earlier concluded that
eggs production appears to be more strongly associated with circulatory
progesterone rather than with oestrogen.
The high value of coefficient of determination represented by the R2
value implied that there is a high accuracy of prediction of egg production
from progesterone level. It is concluded from the results of this study
that serum progesterone level is a good estimator of egg production in
the grey helmet guinea fowl. It has been demonstrated in this study that
since progesterone level is highly related to egg production, the seasonality
of egg production in helmet guinea fowls in the tropic may be broken and
the number of egg produced increased by giving progesterone in food or
in water whichever is convenient and stable. However, investigation into
the possibility of an all year round egg production through exogenous
administration of progesterone is recommended.
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