WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2025 41 groups. Families with GEBVs ranging from -0.13 to <0.0 were categorized as “worst,” from 0.0 to <0.13 as “bad,” from 0.13 to <0.26 as “good,” and from 0.26 to <0.39 as “best.” The survival of their progeny was subsequently assessed in the batch 49 EHP challenge test. Results Genotyping results Family assignments using the SNP array were highly successful. In batch 48, after initial quality control, 99.7% of the animals from the growth test and 96.2% from the challenge test were assigned to both parents, lower rates of assignment were found in the dead animals in the challenge test due to DNA degradation. In batch 49, family assignment improved even further, reaching 100% in the animals from the growth tests and 98.5% in the animals from the challenge tests. Growth tests Batch 48: In Punta Canoa Colombia (PC), shrimp were harvested after 86 days, at an average harvest weight of 19.44 grams (ADG 0.23). The mean family harvest weight ranged from 16g to 24g, with a coefficient of variation of 8%. Shrimp from 46 out of the 47 families were recovered, with the number of animals harvested per family ranging from 2 to 459 (8 families had fewer than 15 animals). Pond survival in Colombia averaged 92% across three tanks. In Vietnam, shrimp were harvested after 93 days in the ponds. The average harvest weight was 19.82 grams, indicating an average daily growth rate (ADG) of 0.21 grams. The mean family harvest weight in Vietnam was also variable (range 14g – 23g), with a coefficient of variation of 10%. Shrimp from 45 families were recovered, and the number of animals harvested per family ranged from 1 to 267 (9 families had fewer than 10 animals). In Vietnam, average pond survival across two ponds was 25%. WFD was confirmed in both ponds, while EHP was detected in one pond. Batch 49: In Punta Canoa, sentinel shrimp were harvested after 95 days in the ponds. The average harvest weight was 26.3 grams (0.28 ADG), with individual weights varying from 9.9 to 38.6 grams. The mean family harvest weight ranged from 19g to 32g, with a coefficient of variation of 9%. Animals from all 67 families were represented, with an average of 14 animals per family harvested (ranging from 2 to 34). Only five families had fewer than 5 animals harvested. In Vietnam, animals were harvested after 76 days in ponds, at an average age of 122 days. The average harvest weight was 15.4 grams (0.20 ADG), varying from 4.6 to 25 grams. Animals from all 67 families were represented, with an average of 15 animals per family harvested (ranging from 3 to 31). Mean family harvest weights varied from 11g to 18.5g, with a coefficient of variation of 10%. Challenge tests Both challenge tests produced high mortality in the infected tanks, and histopathology and qPCR analysis confirmed the presence of EHP and WFD in the infected animals. In batch 48, the final survival rate was 18.7%, while in batch 49, it was 13.03%, showing the high impact of the combined EHP + WFD infection. On the other hand, survival rates were above 80% in the negative controls in both trials (Figure 1). Mean family survival for EHP + WFD revealed significant variability in both batches, ranging from 0% to 77% in batch 48 and from 0% to 53% in batch 49 (Figure 2). FIGURE 3. Percent differences in the productive parameters of the infected vs negative control challenge test tanks in batches 48 and 49. Orange boxes show a decrease while the blue boxes show an increase in the respective parameters; FCR= food coversion rate. CV= Coefficient of variation in weight of the survivors. FIGURE 4. Size distribution of survivors in all harvested tanks from the challenge tests (a) batch 48 and (b) batch 49. (CONTINUED ON PAGE 42)
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