Reproductive Development and Performance of Male Native Chickens Raised under Natural Day Length and Photoperiod of Fifteen Hours a Day

Abstract

To study the effect of photoperiod on growth and development of male reproductive organs and change of plasma testosterone levels, two groups of a hundred each of 12-week-old male native chickens were used. During 12-20 weeks of age both groups were kept under the same photoperiod of natural day length (NDL) and from 20 weeks of age onwards one group was assigned to the photoperiod of 15 hours a day (15L : 9D) while the other was remained under the NDL. It was found that, at some age levels, the 15L : 9D group had greater values (P<0.05) of the following characteristics than the NDL group, they were testicular weight (at 22 w, 12.25g vs 8.56g) vas deferens weight (at 22 w, 0.71g vs 0.35g),and testosterone level (at 22 w, 7.58 nmol/l vs 1.73 nmol/l; at 24 w, 8.46 nmol/l vs 4.21 nmol/l). Body weight, vas deferens length and comb weight of the two groups were not different (P>0.05). To study the effect of photoperiod on semen production and quality, ninety-six of 20-week-old cockerels were allocated into 2 photoperiods of NDL and 15L : 9D with 4 replications of 12 each. Although the 15L:9D and NDL groups had their onset of semen ejaculation occurred at the same age of 23 weeks and with similar (P>0.05) body weights (2.37 kg vs 2.34 kg), their first semen volumes (0.18 ml/bird vs 0.10 ml/bird), number of birds with synchronous entry into the onset of semen ejaculation (10.42% vs 2.08%) and ages at 100% ejaculation of flock (34 w vs 36 w) were different (P<0.05). In term of semen quality, the two photoperiods yielded similar results. Semen volume, spermatocrit value, and semen concentration of the male native chickens were within concentration in this experiment was determined via the spermatocrit value of semen which was measured and then substituted for the x value in regression equation of y = -0.7318846+0.56000099x. The regression equation was acquired earlier by the means of regression analysis of semen concentration (dependent variable, y) on spermatocrit value (independent variable, x). The method was proved highly reliable with correlation coefficient, r = 0.988 (P<0.001). In addition, sperm fertilizing ability of the two groups was not diferent. Fertility rates of the 15-month-old Isa Brown hens artificially inseminated with semen obtained from cockerels of different photoperiods were comparable and ranged from 60 to 79 per cent.