Relationship Between Age and Body Weight at Sexual Maturity and Some Egg Production Traits In Three Varieties of Japanese Quails

A study was conducted to determine the relationship between age and body weight at sexual maturity and some egg production traits in varieties of Japanese quails. A total of 60, five week old female Japanese quails were selected randomly from an existing flock in the Animal Pavillion, University of Ilorin. The birds were grouped into three according to their plumage colour variety: A & M white (White), Machurian gold (Brown) and Pharaoh quail (Black). Data obtained on age at sexual maturity (ASM), body weight at sexual maturity (BWSM), average egg weight (AEW), hen day production (HDP), weight of first twelve egg (WFTE) and body weight at peak production (BWPP) were subjected to one-way analysis of variance. Phenotypic correlations between age at sexual maturity and some egg production traits were also determined. Age at sexual maturity was significantly lower (P<0.05) in the White than the Brown and Black varieties. Average BWSM was also found to be significantly lower (P<0.05) in the White than in the Brown and Black varieties. BWPP however showed no significant differences (P>0.05) among varieties. HDP was highest in the White than the Brown and Black varieties and WFTE was lowest for the White and largest for Black variety. ASM was positively correlated with BWPP, WFTE but negatively correlated with HDP in all varieties. BWSM was positively correlated with AEW, BWPP. The result showed that early maturing quails had smaller body weight, higher HDP but smaller egg weight. It was concluded that plumage colour variety has an effect on ASM, BWSM, AEW, BWPP and HDP with the white variety having better ASM and HDP.


INTRODUCTION
The marked advantages of the Japanese quail over other poultry birds such as its fast growth, early sexual maturity, high rate of egg production, short generation interval, short incubation period, its high resistance to most notorious poultry diseases and discoveries of its health benefit has made it is to assume a worldwide importance not only as a research animal but also as a good source of animal protein.
Age and body weight at onset of puberty in poultry birds have been established to have a significant influence on most egg production traits (Camci et al.2002;Metin, 2007 andAgaviezor et al., 2008).According to Sezer et al. (2006), the initial growth pattern and body weight at sexual maturity are the main factors which affect the performance of birds in the laying phase.There is no doubt that bird's live body weight at the time of commencement of egg-laying determines its age at first egg, age at peak production and the overall performance of the hen (Oruwari and Brody, 1988).
Egg production traits such as egg number, egg and body weights at sexual maturity have been reported to be influenced by age at sexual maturity in chickens and quails (Ghanem, 1995;Camci et al., 2002 andMetin, 2007) and the relationship existing between age, bodyweight at sexual maturity and egg production traits have been documented in quails (Aly, 1992;Camci et al., 2002)  Several plumage colour variants have been identified in the Japanese quail and its effects on hatchability, body weight and some egg production traits have been reported (Minvielle et al., 2007;Islam et al., 2014;Rahman et al., 2010).However there have been conflicting reports on variants' suitability for egg or meat production purpose; as environmental effect seems to come into play.There is paucity of records on the influence of plumage colour on age and body weight at sexual maturity and production traits in the Japanese quail in Nigeria.
This study was therefore aimed at investigating the relationship between age and body weight at sexual maturity and some egg production traits in the varieties of Japanese quail.

Experimental birds and management
A total of 60 female Japanese quails (comprising 20 birds from each variety of A & M White, Machurian Gold, and Pharaoh Quail) of five weeks of age were selected from existing flock at the Department of Animal Production poultry section, Teaching and Research Farm, University of Ilorin.The birds were housed separately based on plumage colour.Each individual bird was wing-tagged for proper identification and kept in individual cage.The birds were fed diet containing 18% crude protein and 2700 kcal metabolizable energy.Both feed and water were provided ad libitum throughout the 10weeks of experiment.

Data collection
Age at sexual maturity was determined by taking record of the age in days at which the first egg was laid by each hen.
Body weight at sexual maturity was taken as the weight of each bird at first egg.This was obtained using a sensitive digital electronic weighing scale with a sensitivity of 0.1g.
The first egg laid by each hen was also weighed to determine the weight of the first egg using a sensitive digital electronic weighing scale with a sensitivity of 0.1g to determine the first egg for each variety.Also weights of first twelve eggs were taken using the same method.
Body weight at peak production was taken as the average weight of birds in each variety when they were all in full egg production.The average egg laid by birds in each variety was calculated as the hen day production (HDP).This was taken as the ratio of the number of eggs produced by individual hen to the number of days in lay.i.e.

HDP =
No. of egg produced by individual hen for a period No. of days in lay Data obtained from the experiment were subjected to analysis of variance in a Completely Randomized Design using the SAS software (2012) and significant means were separated using Duncan's Multiple Range Test.Correlation analysis was used to detect the relationship between age at sexual maturity and other egg production traits using the same soft.

RESULTS AND DISCUSSIONS
The mean values of some egg production traits in the three varieties of Japanese quails are shown in Table 1.Mean age at sexual maturity for the white variety was significantly (P < 0.05) lower than the brown and black varieties.The mean egg weight (g) of first eggs in the white variety of Japanese quails was significantly (P< 0.05) lower (7.44g)than Black and the Brown varieties, with no significant differences between the Brown (9.40g) and Black (9.73g) varieties.The trend was also the same for the weight of the first twelve eggs.Variations in egg weight among the White, Brown and Black varieties recorded in this study could be attributed to the variation in body weights of the different varieties.Positive relationships have been reported between egg weight and body weight in poultry birds (Benoff and Renden, 1983 In this study, body weight at peak production was significantly (P<0.05)affected by the Japanese quail varieties.The black variety had the highest body weight (141.31g) at peak production followed by the brown variety (128.43g), while the white variety had the least body weight (112.39g).Variations in body weight at peak production among the White, Brown and Black varieties recorded in this study could be attributed to variety differences.
Hen day production for the 10weeks of lay was significantly (P<0.05)higher for White variety than for Brown and Black varieties.The mean hen day productions observed in this study were 67.16% (white), 53.64% (brown) and 52.98% (black).The higher hen day and egg production in the white variety was probably because the white variety came into lay earlier (44 days).Hen day production values in this study is within range of those obtained by Prabakaran et al. (1992) who reported hen-day egg production of 49.2-79.3%.However, higher hen day production value of 77-94.8% was obtained by Kobayashi et al., (1994).The present findings were mostly supported by the findings of Table 2 shows the phenotypic correlations between production traits in the White, Brown and Black varieties of Japanese quail respectively.ASM in all the plumage varieties were positively correlated with other production traits except for HDP in all the varieties.HDP was however only significantly (P<0.05)correlated with the ASM in the Brown variety.For all the plumage varieties WFTE was positive and significantly correlated with ASM.The results indicate that within each variety, early maturing pullets had smaller body weight but laid more eggs while late maturing ones had larger body weight but laid fewer eggs.The positive and significant (P <0.05) correlation between ASM and WFTE indicates that it is possible to select for the two traits simultaneously and that they are not necessarily antagonistic.These results agree with the findings of Gunes and Cerit, (2001) who also reported negative correlation between ages at sexual maturity egg production.The positive correlation between ASM and BWSM also agrees with the reports of Koçak et al. (1995) and Marks (1991) who reported that long-term selection for high body weight delayed sexual maturity.
BWSM was positively correlated with AEW and BWPP for all the plumage colour varieties with significant (P<0.05)values in the White and the Black varieties.Relationship of the same with HDP was however either low (White and Black) or negative (Brown).This supports the findings of Sadeghi et al. (2013) who reported positive phenotypic correlation between body weight and total egg weight in three lines of Japanese quail.
AEW was positively correlated with BWPP and WFTE in the White and Black varieties but negatively correlated with the HDP in all varieties.Thus as selection is made for birds that peak early, egg number will also increase but egg size decreases probably due to the birds' smaller body weight.The negative correlation between AEW and egg production agrees with the general concept that prolific layers usually lay more but smaller sized eggs (Koçak et al., 1995).BWPP was negatively correlated with HDP in the White and the Brown varieties but low and positively correlated with HDP in the Black variety though the values were not significant.This implies that within variety, birds that were able to maintain higher body weights at peak production laid fewer but larger sized eggs.WFTE was positively correlated with most of the traits except BWSM, AEW and HDP and significantly (P< 0.05) with ASM and HDP.The size of the first twelve eggs however depended on BWSM and decreased with increased egg number.The positive correlation between WFTE and AEW indicated that breeders can be selected for good egg size soon after pullets come into lay.

CONCLUSION
The results of this study showed that plumage colour variety influenced age at sexual maturity and production traits in Japanese quail.The white variety of Japanese quail reached age at sexual maturity at an earlier age and had better egg production.Body weight at sexual maturity and at peak production and egg weight were higher in the Brown and Black varieties.Japanese quails are heavier when they reach sexual maturity later, but early sexual maturity increases egg production.
Black and Brown varieties of Japanese quail agrees with the reports of most authors for body weight at sexual maturity in Japanese quail (Gunes and Cerit 2001; Oguz et al., 2001; Karabag et al., 2010 and Sadeghi et al., 2013).These authors have reported an increase in body weight as the age at sexual maturity increases.
; Ayorinde et al., 1988 and Ojo et al., 2011).Smaller birds are therefore expected to lay smaller eggs while larger birds lay bigger eggs.The AEW obtained in this study however falls below the values observed by Camcı et al.

Table 1 : Mean values (±SD) of some egg production traits in different varieties of Japanese quails
Means in a row with no common superscripts are significantly different (P < 0.05).ASM = age at sexual maturity; BWSM = body weight at sexual maturity, AEW= average egg weight BWPP = body weight at peak production, HDP= hen day production WFTE = weight of first twelve eggs.

Table 2 : Phenotypic correlations between traits in White variety of Japanese quail
ASM = age at sexual maturity.BWSM = body weight at sexual maturity, AEW= average egg weight BWPP = body weight at peak production, HDP= hen day production WFTE = weight of first twelve eggs