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 หัวเรื่อง:การเจริญเติบโตและคุณภาพซากของไก่พื้นเมือง เลี้ยงภายใต้ชั่วโมงแสงธรรมชาติ และชั่วโมงแสงยาว 23 ชั่วโมงต่อวัน ผู้เขียน: Ratana Chotesangasa, Nirat Gongrattananun สื่อสิ่งพิมพ์:pdf AbstractThe effect of long photoperiod on growth, carcass yield, and carcass composition in native chickens were examined. Two lighting programmes of natural day length (NDL) and photoperiod of 23 hours/day (23L:1D) were set. It was found that the 23L:1D group tended to have better growth than the NDL group. Average body weights of the 23L:1D and NDL groups at 16 weeks of age were 1,508 g and 1,451 g and at 20 weeks of age were 1,803 g and 1,746 g, respectively, while feed conversion ratios of the two groups were not different (P>0.05). Both groups had low mortality rate of only 2-3% with no sign of leg disorder, ascites, and breast blister. In term of carcass yield, males responded to the long photoperiod more than females. As carcass weights of the females of both groups were not different (P>0.05), carcass weights of the male of 23L:1D group were higher than (P<0.05) those of the NDL group. Higher yields were found of those killed at 16 weeks of age in chilled carcass weight (1,606 g, 1,479 g, P<0.05), breast weight (317.9 g, 269.3 g, P<0.05), and drumstick weight (232.5 g, 208.0 g, P<0.05), and of those killed at 20 weeks of age in breast weight (378.4 g, 344.9 g, P<0.05). When compared between age, killing at the older age yielded more meat in term of actual carcass weight (P<0.05) but not in term of percentage of chilled carcass weight (P>0.05) except for the drumstick weight in the male (P<0.05). Chemical compositions of the carcass did not change due to photoperiods (P>0.05) but changed considerably due to ages at killing. In general, meat protein was increased from about 61.0% to 65.2% (P<0.05), meat ash was decreased from about 3.9% to 3.4% (P<0.05), and meat fat showed no noticable change (P>0.05) when compared between killing at 16 and 20 weeks of age. |
หัวเรื่อง:พัฒนาการและความสามารถทางการสืบพันธุ์ของไก่พื้นเมืองเพศผู้ เลี้ยงภายใต้ชั่วโมงแสงธรรมชาติและชั่วโมงแสง 15 ชั่วโมงต่อวัน ผู้เขียน:Ratana Chotesangasa, Nirat Gongrattananun สื่อสิ่งพิมพ์:pdf AbstractTo 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 the range of 0.34-0.41 ml/bird/ejaculation, 13.10-14.92%, and 6.60-7.62 million/mm3, respectively. The semen 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. |
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 Researcherดร. ปิยะ กิตติภาดากุล, ผู้ช่วยศาสตราจารย์ที่ทำงาน:ภาควิชาพืชไร่นา คณะเกษตร สาขาที่สนใจ:การปรับปรุงพันธุ์พืช (Plant Breeding), การประยุกต์ใช้เทคโนโลยีชีวภาพในการปรับปรุงพันธุ์ พันธุศาสตร์ปริมาณ, Quantitative Genetics and Molecular Approaches in Plant Breeding, การใช้สถิติขั้นสูงในงานวิจัยเกษตร (Advance Statistics in Agriculture) , การจัดการและการผลิตมันสำปะหลังและพืชพลังงาน (Crop Management and Production) Resume |