WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2019 41 tables are used, usually based on a percent of body weight. In the months that follow, feeding is done conventionally by broadcasting. This practice is inefficient because it increases the cultivation time in grow-out ponds. Raceways are tanks where larvae from larviculture hatcheries (stage PL12) are held for 7 to 14 days for acclimation. Stocking density varies between 10 to 40 PL/L. Harvest size varies between 20 and 60 PL/g (16-50 mg). Raceways have controlled oxygen and temperature conditions and can handle nitrogen waste easily. The nutrition provided is much better utilized by the larvae, as well as disease control. Larvae are then transferred to grow-out ponds. Nursery ponds are smaller than grow-out ponds, usually close to 1 ha in area. Larvae from hatcheries (stage PL12) are stocked and grown for 10-25 days to a size of about 0.2 g, when they are stocked into grow-out ponds. Nutrition provided can be better utilized, as well as better disease control and prevention. It allows a significant reduction in the cultivation time in the grow-out ponds. For direct stocking (Table 5), when comparing automatic feeding (acoustic and timer) with traditional and multi-feeding, increasing the stocking density by 9 percent, the growth rate was 1.27-1.31 g/week, similar due to a greater survival of 45 to 58 percent that possibly generated under feeding, reaching a greater biomass (+33 percent). When survival and production biomass are correctly estimated, the improvements in growth rate and FCR are clear. Stocking densities increase by 9 percent in automatic feeding (acoustic or timer), compared to traditional feeding (<6 times/day and multi-feeding). Likewise, the greatest survival (57-59 percent) is observed for automatic feeding, while in conventional feeding and multi-feeding it is 44-46 percent. Many producers lack experience with automatic feeding management and lack confidence in achieving greater survival, which has not allowed more optimal feeding management, leading to under-feeding. Shrimp growth rate was 1.27-1.34 g/wk with automatic feeding, 1.23 g/wk with conventional feeding and 1.30 g/ wk with multi-feeding. With automatic feeding, stocking density was higher by 9 percent, with greater survival (+22 percent), higher biomass (+33 percent) at harvest, resulting in a lower production cost (-21 percent). For stocking from raceways (Table 6), when comparing automatic feeding (acoustic and timer) with multi-feeding and broadcast feeding, the stocking density was higher by 12 percent, with greater survival (+5 percent), greater growth rate (+7 percent), higher biomass (+10 percent), resulting in a lower production cost (-12 percent) from US$1.91/lb to US$1.70/lb). The use of raceways does not make the advantages of using automatic feeding so obvious. SIZE 10 MAXUM 80 160 0 NORGREN MAX. MIN. 393.31 [9990] 391.31 [9939] 48.00 [1219] 52.19 [1325] DCC Inlet CYL. Disch. End of Head BIN Inlet 53.25 [1353] 57.69 [1465] 102.13 [2594] 111.12 [2822] 2 18.00 [457] 1.93 [49] 256T 0 60 15 45 30 195.72 [4971] F085 SHIMPO 64.83 [1647] 108.59 [2759] 15.00 [381] 36.91 [937] 31.19 [792] 29.19 [741] MAX. MIN. 19.16 [487] 30.00 [762] 39.00 [991] Ă12.00 [305] 2.00 NPT [WATER] 2.00 NPT [STEAM] 1.00 NPT [STEAM] 66.50 [1689] 12.56 [319] 24.59 [625] 15.88 [404] 284.00 [7214] 1.00 NPT 2.00 NPT 3/4 NPT 101.44 [2577] 30.38 [772] 88.00 [2236] 108.28 [2750] 278.03 [7062] 199.38 [5064] 269.88 [6855] 67.28 [1709] 15.00 [381] P.O. Box 8 100 Airport Road Sabetha, KS 66534, USA Phone: 785-284-2153 Fax: 785-284-3143 extru-techinc@extru-techinc.com www.extru-techinc.com Are You Crushing Pellets to Achieve Sub 1.0mm Feed? There is an alternative. An Extrusion Processing System from Extru-Tech can consistently provide fine feed. Key advantages include: • Advanced screw, knife and dies engineered exclusively for sub millimeter production • Eliminates re-processing heat damage and nutrition loss • Exclusive extrusion process provides on size yields over 95% If you’re currently crushing larger pellets to achieve sub 1.0mm feed, eliminate the spec loss and make the investment in an Extru-Tech Extrusion Processing System. In the aquafeed business, you either sink or swim. Contact Extru-Tech today at 785-284-2153 or visit us online at www.extru-techinc.com You Could Be Experiencing Up to 45% Off Spec Product Loss. ET-297D.indd 1 1/19/18 3:11 PM (TEXT CONTINUED ON PAGE 42)
RkJQdWJsaXNoZXIy MjExNDY=