ارزيابي زيستي اقتصادي پرورش جوجه هاي گوشتي بر اساس نسبت هاي مختلف جنسيتي

Bio-economic evaluation of broiler production with different sex ratios

زمينه مطالعاتي: پرورش جوجه هاي گوشتي به تفكيك جنسيت يا به نسبت هاي مختلف جنسيتي موضوعي است كه در تحقيقات مختلف، نتايج متفاوتي دربرداشته است. هدف: اين تحقيق به منظور مقايسه شاخص هاي زيستي اقتصادي پرورش نسبت هاي مختلف جنسيتي جوجه هاي گوشتي از روز يازدهم پرورش انجام گرديد. روش كار: آزمايش با استفاده از 180 قطعه جوجه گوشتي سويه راس 308 در 5 گروه مختلف نسبت جنسي (گروه 1: 25 درصد نر و 75 درصد ماده؛ گروه 2: 50 درصد نر و 50 درصد ماده؛ گروه 3: 75 درصد نر و 25 درصد ماده؛ گروه 4: 100 درصد ماده و گروه 5: 100 درصد نر) با 3 تكرار و 12 جوجه در هر تكرار در قالب طرح كاملاً تصادفي انجام گرديد. نتايج: بر اساس نتايج، خوراك مصرفي فقط در دوره رشد (11 تا 24 روزگي) بين گروه هاي مختلف جنسيتي تفاوت معني داري داشت (05/0P<) و گروه هاي 1 و 3 بيشترين مقدار مصرف را نشان دادند. در دوره رشد و كل دوره (11 تا 42 روزگي)، گروه حاوي نر خالص، بيشترين افزايش وزن روزانه و بهترين ضريب تبديل غذايي را داشت (05/0P<). از ميان پارامترهاي لاشه، فقط بازده لاشه تحت تاثير تيمارهاي آزمايشي قرار گرفت و گروه 3 بيشترين بازده لاشه (06/73%) را دارا بود (05/0P<). شاخص اروپايي جوجه هاي گوشتي در گروه هاي 5 و 3 بيشترين مقدار را نسبت به گروه هاي ديگر نشان داد (05/0P<). سود محاسبه شده در 9 حالت ارزيابي اقتصادي (سه روش تعيين قيمت شامل ميانگين قيمت سال 1394، ميانگين قيمت بدترين و بهترين دوره پرورش دو سال 1393 و 1394) و 3 روش فروش (فروش مرغ زنده، مرغ كشتار شده و به تفكيك قطعات لاشه) با كاهش درصد جوجه هاي نر در گروه هاي مورد مطالعه روند نزولي داشت (05/0P<) و كاهش تا 50 درصد نر، تفاوت معني داري را نشان نداد. نتيجه گيري نهايي: با توجه به نتايج حاصل از مقايسه سود روش هاي مختلف ارزيابي اقتصادي مي توان پرورش مخلوط را تا زماني كه درصد نرها از 50 درصد پايين تر نباشد، توصيه نمود.

Introduction: Sex of birds creates a fundamental difference in the physiological and nutritional requirements. For example, the feed conversion ratio of female broiler chicks is higher than that of males (over 30 days of age), which results in more fat storage in the body of females (Verapeen and Driver 2000). Although there are several reports on the superiority of male chicks to females in various economic traits such as average daily gain (Verapin and Driver 2000; Ojedapo et al. 2008; Zamani et al. 2012); feed intake (Fischer 1985; Laseinde and Oluyemi 1994; Zamani et al. 2012) and carcass traits (Verapeen and Driver 2000; Ojedapo et al. 2008; Zuowei et al. 2011; Taghan Agh et al. 2011), on the contrary, it has been shown that the mixed rearing of males and females leads to stimulation of protein anabolism, nitrogen uptake and mineral retention and so a higher weight gain at the end of the breeding period (Iyeghe –Erakpotobor 2001). This study was conducted to compare the bio-economic indexes of broiler production with different sex ratios from 11 to 42 days of age. Material and methods: The experiment was done using 180 Ross 308 broilers in 5 sex ratio groups (Group 1: 25% male and 75% female, Group 2: 50% female and 50% male, Group 3: 75% male and 25% female, Group 4: 100% female and Group 5: 100% male) with 3 replicates and 12 birds per replicate by employing a completely randomized design. Grower (11-24 days) and finisher (25-42 days) periods’ ration of broilers were balanced based on Ross-308 catalog. Feed intake (FI), average daily gain (ADG) and feed conversion ratio (FCR) were measured for each experimental group at the grower (11-24 days), finisher (25-42 days) and total (11-42 days) periods based on the hen- day method. At the end of the experiment (forty-second day), European Production Efficiency Factor (EPEF) and European Broiler Index (EBI) and also carcass traits after 9 hours starving were calculated by selecting 4 chicks per pen considering the sex ratio of each group. For economic evaluation, an index was formulated to determine the worst and best rearing periods (2014-2015) and then costs of grower and finisher rations based on 3 ways of pricing (Rials/kg) contains mean price of 2015, mean price of worst period and mean price of best period were estimated. To estimate income and profit, 3 methods of sale methods were included sale of live chicken, sale of carcass and Half-split sale. So, means of income and profit (Rials/chick) in studied groups were estimated based on 9 economic evaluation methods (3 sale methods×3 pricing methods). Results and discussion: Feed intake was significant only in grower period (11-24 d) and groups with 25% and 75% males had the highest amount of feed intake (P<0.05). Several studies have reported the differences in feed intake between male and female broiler chicks (Fischer 1985; Henrry and Burke 1998; Laseinde and Oluyemi 1994; Rondelli et al. 2003; Zamzni et al. 2012). They reported a difference in the feed intake of broiler chickens reared only one sex with a mixed sex, that the results of our study did not perfect match their reports. During the grower and whole experimental (11-42 d) periods, full male broilers’ group had the greatest average daily gain and the best feed conversion ratio (P<0.05). The final weight (42 day) of the group with 100% males was significantly higher than the rest of the groups (P<0.05). Our results in weight gain was in accordance with the results of some researchers (Fischer 1985; Verapeen and Driver 2000; Jaafari Sayyadi and Ohadi Hayeri 2001; Zamani et al. 2012; Benyi et al. 2015). Male broiler chickens are more active than females (Fischer 1985) and also they are more likely to grow due to genetic characteristics (Ojedapo et al. 2008), hence, feed intake and weight gain in male broiler chickens are higher. None of the groups showed significant differences in survival percentages and EPEF (P<0.05). But, EBI of groups with 100% and 75% males were significantly higher than other groups. Among the carcass traits, only the carcass efficiency showed a significant difference and group with 75% male chicks showed 73.06% i.e. the highest carcass efficiency (P<0.05). Non-significant effects of sex on the most carcass traits such as abdominal fat percent in this study may be justified by the lack of sex effects on energy and fat metabolism reported by Jia et al. (2014). Comparison of nutritional and major inputs costs based on three different pricing methods did not show any significant difference among the groups (P<0.05). The average sales income of each broiler chicken in the different groups showed that the highest income from full male group is achieved, although the difference in income from this group compared to other groups in the live sales method was significant (P<0.05), but it was not significant with group 75% males in the carcass sales method; and in the half-split sale method, it showed no significant difference compared to groups 75% and 50% males. The calculation of the net profit per a chick in 9 methods of economic evaluation showed that the development of full male broiler chicks in all evaluation methods was more profitable than other groups, but its difference with groups 50% males and 75% males was not significant (P<0.05). Earlier economic evaluation indicators provided for the broiler breeding systems have minimized the cost of breeding, while now more emphasis is placed on maximum profits (income minus costs) (Mosavi et al. 2012). Considering that the manipulation of external factors (economic growth, product processing) with internal factors that improving the performance of broilers in breeding period can result in greater profitability (Groen et al. 1998), which is consistent with the results of the present study. Conclusion: According to the results of comparing profit using different economic evaluation methods, it can be recommended that mixed sex production of broiler chickens will be alright when the proportion of males not to be less than 50%.