Introduction

The poultry industry in India has shown remarkable progress in the last few decades, attaining the status of a full-fledged industry. Among them broiler farming is one of the promising and sustainable businesses in agricultural sector but one of the great economic problem of the broiler production is that all broilers are not the same weight at the market age. It is because broilers are being raised as straight run or mixed sex population. Because of difference in their sex, male and female broiler differs from each other in many aspects. Under similar management condition, compared to females the males grow faster, converts feed more efficiently, achieve marketable weight earlier than females, and have less carcass fat (Kalita and Sapcota, 2014). On comparison, males vary more than females within a given flock because the males are heavier. Females are usually small, medium and large in size, so also in males. Normally, the extremes are about 30 to 35 percent above and below the average weight of each sex. A flock can be called uniform, when approximately 75 % of each sex will be within 10% of the average weight of each sex for the flock (Kalita and Sapcota, 2014). Uniformity in the final body weight of the broilers as well as other economic advantages can be attained by growing flocks in single-sex population from day old age (Narahari and Kumararaj, 2008). The objective of the investigation was to evaluate the performance of the broilers and their uniformity at various weeks of age by raising each sex separately and compare them with the counterparts raised as mixed sex population.

Material and Methods

The experiment was conducted in the Instructional Poultry Farm, C.V.Sc, AAU, Khanapara, Assam (for 42 days) from the month of August to October 2015. A total numbers of 210 day-old commercial broiler chicks (Cobb-400 Y) having similar body weight from a single hatch was procured. Wing banding of the chicks were done on the1^st day of arrival. The straight run commercial broiler chicks were reared from day-old to 21 days of age under standard managemental practices. Sex separation was done by observing the early appearance of comb in case of male birds. At 22 days of age, 180 birds were randomly allotted into three treatment groups viz., T₀ (60 Straight run i.e. 30 males and 30 females), T₁ (60 males) and T₂ (60 females). Each group was divided into 3 replicates with 20 chicks each. The weight of individual bird was recorded at the start of the trial and then weekly interval up-to 6^th week in the morning hour before offering any feed and water with the help of standard weighing scale. From these records, average weekly and final body weights of individual birds under each and every treatment groups were calculated. Uniformity of the body weight of broilers of different treatment groups was calculated on the basis of number of broiler within 10% above and below the mean body weight of the group. According to Narahari and Kumarraj (2008) a flock is termedas having body weight uniformity if 75% of the broilers of the flock are within 10%above and below of the mean body weight.

Data were analyzed by using standard statistical method.

Result and Discussion

The male broilers had significantly (P≤0.05) higher body weights in all the weeks of experiment compared to female (T₂) and straight run (T₀) groups. Table 1 recorded significantly (P≤0.05) higher mean body weight than the female (T₂) group in 4^th, 5^th and 6^th week of experiments. This could be due to the presence of only male bird in T₁ group and 50% male inT₀ group. This is indicative of an advantage by rearing broilers sex-separated after the end of brooding period. The female group of broiler could not grow fast as compared to the other two groups. This could be due to their genetic make-up. The male broilers usually grow faster compared to female probably because of their genetic capability (Kalita and Sapcota, 2014).

Table 1: (Mean ±SE) weekly body weight (g/bird) of broilers under different treatment groups

Means bearing different superscripts within a row differ significantly (P≤0.05)

Table 2: Anova for weekly body weight (g/bird) of broilers under different treatment groups

* P≤0 .05 significant

Significantly heavier average body weight in male broilers compared to their female counterparts was also reported by Veerapen and Driver (1999), Narahari and Kumararaj (2008), Ojedapo et al. (2008), Lopez et al. (2011), Amponsah et al. (2012), Hernawan et al.(2012), Sogunle et al.(2013) and Kalita and Sapcota (2014), Beg et al. (2016). Similarly, Narahari and Kumararaj (2008) also reported that male chicks are not only capable of growing at a faster rate, but also grow well for a longer period. According to them, the growing of female broiler is slower beyond seven week of age. The uniformity of broilers at the end of 4^th week of age was found to be almost similar being 90% in both T₀ and T₂ group and 91.6% T₁ group (Table 3).

Table 3: Uniformity percentage (%) of the broilers under different treatment groups

The similar kind of percentage (%) uniformity without much or no difference observed in all the three groups could be due to lower range of weight at 4^th week of age. However, with comparatively higher rate of growth during the 5^th week of age, the uniformity percentage (%) came down drastically in all the 3 groups at the end of 5^th week. At 5^th week of age, the highest percentage (%) of uniformity was observed in T₁ (male) group (78.33%) followed by T₂ (76.67%) and T₀ group (48.33%) respectively. The lowest uniformity observed in T₀ group at 5^th and 6^th week of age could be due to presence of both the sexes in the mixed-sex group, where the female birds grew comparatively slower than their male counterparts results lesser uniformity in the group. However, at the time of marketing both the sex separated groups had the highest average uniformity being 90% in T₁ group and 80 % T₂ group. As both the groups comprised of single sex population, these might be lesser competition for feeder space or peckorder resulting in the uniformity of body weights in both the groups (Kalita and Sapcota, 2014). Lower uniformity percentage is observed in T₀ group (70.17%) was probably due to the presence of both sexes in this group, resulting competition for feeder space and peck order among the large, medium and small birds. This resulted in lower uniformity in T₀ group. Less uniform final body weight at the time of marketing in mixed population could also be due to inadequate nutrient intake and lack of adequate feeder space without competition was reported by Singh and Nagra (2006). According to them, better uniformity observed in the sex separated group at the time of marketing could be due to rearing each sex separated flocks, which helps to reduce feed competition between large, medium and small sized birds. They further reported above 90% uniformity in male broiler and 85% uniformity in female broiler. Result of the study indicated that sex-separated rearing of commercial broiler is useful for uniform body weight at the time of marketing.Better uniformity is owed by maintenance of sex separated rearing was also reported by Toudic (2006), Narahari and Kumararaj (2008) and Kalita and Sapcota (2014).

Conclusion

At all the weeks of age, highly significant difference (P<0.05) was observed in body weight among the three experimental groups. The T₁ (male) groups showed the highest body weight at of 1460.17 ± 11.05, 2254.67 ± 28.13 and 2509.17 ± 22.24 g for 4^th, 5^th, and 6^th week respectively followed by T₀ (mixed-sex) and T₂ (female) group. At the age of 4^th week under three different treatment groups, the highest uniformity, was found in T₁ (male) (91.6 %) and lowest uniformity found in both T₀ (mixed-sex) and T₂ (female) groups (90%). During 5^th and 6^th week of age the highest uniformity was found in T₁ (male) (78.33 % and 90 %) followed by T₂ (female) (80 % and 76.67 %) and T₀ (mixed-sex) (48.33% and 70.17%).

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