Değişik sınırlı yemleme yöntemlerinin gökkuşağı alabalıklarında (Oncorhynchus mykiss) nicel ve nitel verim kriterleri üzerine etkileri

Aç bırakma, sınırlı yemleme ve protein sınırlamasına maruz bırakıldıktan sonra, gökkuşağı alabalıklarının (Onchorhynchus mykiss) telafi büyüme tepkileri incelenmiştir. Çalışmada üç deneme yürütülmüştür. Deneme Iʼde, başlangıç ağırlığı 54,21±0,34 g olan toplam 1125 gökkuşağı alabalığı 5 muameleye 3 tekerrürlü olarak rasgele dağıtılmıştır. Balıklar 0 (kontrol), 1, 2, 3 ve 4 hafta aç bırakıldıktan sonra 8 hafta doyana kadar yemlenmişlerdir. Yeniden besleme döneminde daha önceden aç bırakılan balıklar telafi büyümesi göstermişlerdir. 1 ve 2 hafta aç kalan balıkların deneme sonunda sürekli yemlenen kontrol grubunu yakaladıkları, 3 ve 4 hafta aç kalanların ise kısmi telafi büyümesi gösterdikleri ve kontrolün gerisinde kaldıkları tespit edilmiştir (P<0,05). Sınırlı yemlenen balıkların gösterdikleri telafi büyümesi daha yüksek yem tüketimlerinden kaynaklanmıştır. Yem tüketimi ile canlı ağırlık arasında oldukça önemli bir ilişki (R2=0,97) tespit edilmiştir. Açlık dönemi sonunda, grupların vücut kompozisyonu, organ indeksleri ile kas ve karaciğer RNA/DNA oranları arasındaki farklılıklar, deneme sonunda ortadan kaybolmuştur. Deneme IIʼde başlangıç ağırlığı 51,84±0,22 g olan toplam 840 gökkuşağı alabalığı 7 muameleye 3 tekerrürlü olarak rasgele dağıtılmıştır. Balıklar 0 (kontrol), 1, 2, 3, 4, 5 ve 6 hafta sınırlı yemlemeye (canlı ağırlığın %0,5ʼi) tabi tutulduktan sonra 8 hafta boyunca doyana kadar yemlenmişlerdir. Sınırlı yemleme periyodu sonunda, yetersiz beslenen balıkların ağırlıkları kontrol grubundan önemli derecede daha düşük bulunmuştur (P<0,05). Serbest yemleme dönemi sonunda 1 ve 2 hafta sınırlı yemlenen balıklar sürekli yem alan kontrol grubunu yakalamışladır. Diğer sınırlı gruplar ise, kontrol grubunun önemli ölçüde gerisinde kalmışlardır (P<0,05). Daha önceden sınırlı beslenen balıklar yüksek iştah göstermişlerdir. Deneme IIIʼte, proteince yetersiz beslemenin daha sonraki telafi büyümesine etkisini incelemek için 62,10±0,38 g başlangıç ağırlığı olan toplam 1125 balık kullanılmıştır. Üç hafta %15, 22,5, 30 ve 37,5 düzeyinde proteinli yemle sınırlanan balıklar, 9 hafta boyunca kontrol grubu yemi (%45 proteinli) ile yemlenmişlerdir. Deneme sonunda, sınırlı protein alan tüm gruplar kontrol ile benzer canlı ağırlık göstermişlerdir. %15 ve 22,5 proteinle sınırlanan balıkların, standart yemle besleme döneminde, kontrolden daha iyi (P<0,05) yemden yararlanma gösterdikleri belirlenmiştir

Use of Natural Zeolite for Ammonia Removal during Simulated Transport of Live Juvenile Sea Bass (Dicentrarchus labrax)

This study was conducted to determine the effects of zeolites on total ammonia nitrogen (TAN) removal during a 24-hour-sea bass transport. Five experimental treatments (0 (control), 10, 20, 30 and 40 g/l zeolite) with 3 replications were applied in 14 l plastic tanks. 90 sea bass (total weight 175.07 ± 0.49 g) were stocked in each tank. The zeolites were placed in mesh bags and renewed 8 and 16 hours (h) after the commencement of transfer. TAN contents of tank waters were measured after 8, 16 and 24 h. The results revealed that at the 8th h, 20, 30 and 40 g/l zeolite doses were significantly effective compared with the control. At the 16th and 24th h the lowest zeolite level (10 g/l) was also effective in TAN removal. In general highest TAN removal was achieved with 40 g/l treatment with efficiencies of 18.33%, 34.08% and 20.96% at the 8th, 16th and 24th h respectively. Overall, the results suggest that the use of zeolite in sea bass transportation could bring remarkable benefits and thereby increase fish transportation density and welfare

Dietary Protein Requirements of Zebrafish (Dania rerio)

Zebrafish (Danio rerio) with an initial weight of 88.61±0.82 mg were fed eight isoenergetic diets containing dietary protein levels ranging from 20 to 55 % by 5 % increments. Each diet was feed in triplicate of fish for 6 weeks. Specific growth rates (SGR) at week 2 and 4 were quadratically affected by the treatments but this trend disappeared at the end of the experiment. Dietary protein levels linearly reduced the values of daily feed intake, feed conversion ratio and protein efficiency rate. The whole body dry matter, ash and lipid concentrations linearly decreased with dietary protein levels whereas whole body protein was quadratically affected. The second order polynomial and two break point linear models (TBPLM) were used to estimate dietary protein requirements. The later model generated lower residual sum of squares when SGRWeek4 and SGRFinal valueswere used as a response. Minimum dietary protein requirements for SGRWeek4 and SGRFinal were estimated by the TBPLM as 27.69 and 28.93 % respectively. Briefly, results of the study suggest a minimum dietary protein requirement of zebrafish is about 29 % for maximum growth rate

Effect of Different Inorganic Substrates on Growth Performance of African Catfish (Clarias gariepinus, Burchell 1822) and Lettuce (Lactuca sativa L.)

Lettuce (Lactuca sativa L.) and African catfish (Clarias gariepinus) were preferred to grow in aquaponics due to their high and fast productivity growth. However, limited research was conducted on the impact on different inorganic substrates’ growth performance in aquaponics. In this study, lettuce’s growth performance was determined in four different kinds of inorganic substrates in Nutrient Film Technique (NFT) aquaponics by measuring final weight, daily growth rate, stem diameter, plant and root lengths, leaf number per plant and shoot/root ratio. Polyester fiber, rock wool, zeolite, and gravel were used as inorganic substrate materials. A constant flow rate of 0.3 L/min was maintained using with a submersible pump motor. At the end of the study, the African catfish’s feed conversion ratio was estimated to be 0.66, while the specific growth rate (SGR) was 2.3%. Total lettuce yields for polyester fiber, rock wool, zeolite and gravel were obtained as 5.072,22 kg/m2 , 4.934,03 kg/m2 , 6.067 kg/m2 , and 5.382,64 kg/m2 respectively. There were statistically significant differences for daily growth rate between the inorganic substrates that the significantly highest values were recorded in the zeolite. The results revealed that initial plant length and shoot/root ratio were the significant factors on the growth performance for lettuce in aquaponic system tested. The best lettuce yield performance was observed in zeolite substrate but, economically available option was found as gravel for hydroponic troughs

Effects of mixed feeding schedules on growth performance, body composition, and nitrogen- and phosphorus balance in rainbow trout, Oncorhynchus mykiss

Background. Reducing feed cost and the pollution originating from feed have been principal matters in fish nutrition. Mixed feeding schedules have been proposed as one of the methods to reduce both of them and successfully tested in many fish species. The aim of the present study was to determine the mixed feeding schedules′ suitability for culture of rainbow trout. Materials and methods. Five different feeding schedules were tried by alternating the presentation of a low-protein (28.1%) diet (A) and a high-protein (49.9%) diet (B). The feeding schedules employed were 1A/1B, 1A/2B, 1A/3B, 2A/2B, and 2A/3B where the numerical values refer to the number of days each diet (A and B) was offered continuously. Fish given diets A and B continuously served as controls. Totally, seven dietary treatments were tested in triplicate for 10 weeks. Results. The fish maintained on the different mixed feeding schedules exhibited lower weight gain than those fed continuously on the high-protein diet (P < 0.05). The fish reared on schedule 1A/3B (1 day diet A alternated with 3 days diet B) had similar specific growth rate (SGR), feed conversation ratio (FCR), and protein efficiency ratio (PER) to those fed diet B continuously and was best among all mixed feeding schedules. However, the most cost-effective treatment was 2A/2B. In addition, this group compared to B resulted in significant increase and reduction of phosphorus retention and discharge, respectively (P < 0.05). The treatments significantly effected body moisture, fat- and ash levels (P < 0.05), but not protein. Conclusion. The study shows that mixed feeding schedules are promising for use in rainbow trout culture as they result in feed cost saving and reduced phosphorus discharge in the effluents