Moss Moss Otoshi Arce Lightner
ROLE OF SELECTIVE BREEDING IN BIOFLOC SHRIMP PRODUCTION & DISEASE MITIGATION
Shaun M. Moss Dustin R. Moss Clete A. Otoshi Steve M. Arce Donald V. Lightner
Presentation Overview • Selective Breeding in Biofloc Systems • Selective Breeding in Disease Mitigation • Genetic Diversity and Inbreeding
Selective Breeding in Biofloc Systems
Biofloc Systems
Heterotrophic System
Photoautotrophic System
Biofloc Particle crude protein = 26.0 – 41.9% crude fat = 1.2 – 2.3% ash = 18.3 – 40.7%
Characteristics of Biofloc Systems (data from OI research trials)
• High shrimp stocking densities (> 300/m2) • High bacterial concentrations (> 1011 cells/L) • High TSS concentrations (> 1,000 mg/L)
Selective Breeding for Growth
Moderate to high heritability (h2 > 0.3) Genetic gains: 3 - 25% per generation High levels of between and within family variation for growth Harvest Weight (g) Top 3 families: 25.13 23.63 24.46 Bottom 3 families: 19.37 18.52 18.57
Growth Rate (g/week)
Minimum Size (g)
Maximum Size (g)
2.19 2.09 2.07
18.66 15.94 16.56
33.56 30.54 30.45
1.68 1.66 1.59
13.81 11.08 12.95
26.70 24.26 26.34
Selective Breeding in Biofloc Systems (growth = g/wk)
Trial 1
Trial 2
Trial 3
Trial 4
Selected
1.79
1.65
1.69
1.79
Unselected
0.85
1.13
1.09
1.33
% Difference
+110
+46
+55
+35
75-m2 biofloc systems stocked at 304 – 410 shrimp/m2
Physiological Mechanisms • Hyperphagy = increased food intake • Reduced maintenance demands for energy • Improved nutrient and energy efficiencies novel suite of digestive enzymes
(Glencross et al. 2013)
Possible Feeding Mechanisms in Biofloc Systems Scanning EM photos of maxillipeds Observed “sweeping” behavior of 3rd maxillipeds when exposed to diatoms
3rd maxillipeds may form a filter-feeding “net”’ with a mesh size of ~10 μm in 2g shrimp.
This “net” could trap diatoms, but probably not smaller cells like Nannochloropsis and Synechococcus. (Kent et al. 2011)
Selective Breeding in Disease Mitigation
Taura Syndrome Virus (TSV) • • • •
ssRNA virus h2 estimates ~ 0.2 (low - moderate) Good selection response (>10% per generation) Commercially available families exhibit >90% survival in per os laboratory challenges 100 80 60
Generation 7 Mean = 84% CV = 13.6%
40 20 0 100 80
Generation 2 Mean = 44% CV = 43.3%
60 40 20 0
Shrimp families
White Spot Syndrome Virus (WSSV) • dsDNA virus • h2 estimates typically < 0.1 (very low) • Mass selection attempts in the Americas Family
WSSV virion mean size = 275 nm
Treatment
Survival
LP-1
Negative control
49 of 50 (98%)
LP-2
Negative control
91 of 96 (95%)
LP-3
Negative control
68 of 68 (100%)
Kona
WSSV positive control
0 of 20 (0%)
LP-1 (2 tanks)
WSSV challenge
24 of 104 (23%)
LP-2 (2 tanks)
WSSV challenge
74 of 129 (57%)
LP-3 (2 tanks)
WSSV challenge
34 of 130 (26%)
Modified from Cuéllar-Anjel et al. 2012
Breeding for Bacterial Resistance • Lessons learned from insect literature – pest insects bred for toxin resistance (Bt endotoxin)
• Need data on quantitative genetics – phenotypic variation – heritability estimates – correlation with other traits
• Possible pathways for selection – Resistance (host “fights” pathogen and reduces pathogen load) – Tolerance (limit the harm caused by a given pathogen burden – reduced effect of toxin)
UAZ’s AHPND Challenge Room • 90-L aquaria and 1000-L tanks • Internal biological filter with crushed oyster shell
• Feed pellets immersed in culture of V. parahaemolyticus • Culture contains known concentration of bacterial cells, so bacterial dose/gram feed is known • Preliminary results: – – – –
LD50 = 105 cells/mL All shrimp died at 106 cells/mL 108 cells/mL common in ponds Generation time of 8-10 minutes
Biofloc System Pathogens Vibrio spp. - gram-negative bacteria - ubiquitous in Biofloc systems - cuticle infection appears as melanized lesions, can also infect a single organ or be systemic - treatment may include medicated feed (various UAZ cases – Biofloc systems in USA)
Biofloc System Pathogens Fusarium spp. - naturally occurring saprophytic fungi - infection facilitated by cuticle wounding - infection appears as melanized, nodular lesions on cuticle, gills, or appendages - fungal hyphae visible by wet mount (UAZ case from 2008 – Biofloc farm in USA)
Challenges with Multi-trait Selection There are always tradeoffs when adding trait(s) to a selection program!
Stewart et al. 1999
Number of Traits Selected by Species (modified from Gjedrem et al. 2012) Species
# programs
Common carp Rohu carp Silver barb Tilapia Nile Tilapia blue Tilapia red Tilapia O. shiranus Channel catfish African catfish Striped catfish Atlantic salmon Chinook salmon Coho salmon Rainbow trout European whitefish Turbot Atlantic cod European seabass Sea bream Freshwater prawn P. monodon P. vannamei Abalone Oysters Mussel
8 1 1 20 2 4 1 1 1 1 13 2 4 13 1 2 3 3 4 2 3 4 3 3 1
# families per program 76 60–70 – 229 90 125 51 200 70 182 280 100 133 206 70 60 110 100 100 82 212 197 210 48 60
Average # traits 2.0 2 1 3.6 2.0 4.0 1.0 4 1 3 5.4 1.5 2.7 5.2 2.0 1.0 4.0 5 6 1 – 2.0 1.7 4.3 3.0
Genetic Diversity & Inbreeding
Possible Limited Genetic Diversity • Breeding companies limit diversity of broodstock for germplasm protection (narrow genetic base) • Random loss of diversity (genetic drift) • Inbreeding – High fecundity – Intense selection – Unknown pedigree
Inbreeding Inbreeding can accumulate rapidly in non-pedigreed populations – especially those with a narrow genetic base
0
0
Broodstock
0
0
1st generation
.125
.125
2nd generation
.375
.375
3rd generation
0
0
0
0
.188
.5
0
Breeding at GN
0
0
0
.125
0
0
.250
.250
.125
.312
On-farm breeding
Inbreeding
Negatively impacts commercially important traits (inbreeding depression) Trait
Inbreeding Depression (%)
Hatch Rate
-13
Survival – Hatchery
-11
Survival – Growout
Shaun M. Moss Dustin R. Moss Clete A. Otoshi Steve M. Arce Donald V. Lightner
Presentation Overview • Selective Breeding in Biofloc Systems • Selective Breeding in Disease Mitigation • Genetic Diversity and Inbreeding
Selective Breeding in Biofloc Systems
Biofloc Systems
Heterotrophic System
Photoautotrophic System
Biofloc Particle crude protein = 26.0 – 41.9% crude fat = 1.2 – 2.3% ash = 18.3 – 40.7%
Characteristics of Biofloc Systems (data from OI research trials)
• High shrimp stocking densities (> 300/m2) • High bacterial concentrations (> 1011 cells/L) • High TSS concentrations (> 1,000 mg/L)
Selective Breeding for Growth
Moderate to high heritability (h2 > 0.3) Genetic gains: 3 - 25% per generation High levels of between and within family variation for growth Harvest Weight (g) Top 3 families: 25.13 23.63 24.46 Bottom 3 families: 19.37 18.52 18.57
Growth Rate (g/week)
Minimum Size (g)
Maximum Size (g)
2.19 2.09 2.07
18.66 15.94 16.56
33.56 30.54 30.45
1.68 1.66 1.59
13.81 11.08 12.95
26.70 24.26 26.34
Selective Breeding in Biofloc Systems (growth = g/wk)
Trial 1
Trial 2
Trial 3
Trial 4
Selected
1.79
1.65
1.69
1.79
Unselected
0.85
1.13
1.09
1.33
% Difference
+110
+46
+55
+35
75-m2 biofloc systems stocked at 304 – 410 shrimp/m2
Physiological Mechanisms • Hyperphagy = increased food intake • Reduced maintenance demands for energy • Improved nutrient and energy efficiencies novel suite of digestive enzymes
(Glencross et al. 2013)
Possible Feeding Mechanisms in Biofloc Systems Scanning EM photos of maxillipeds Observed “sweeping” behavior of 3rd maxillipeds when exposed to diatoms
3rd maxillipeds may form a filter-feeding “net”’ with a mesh size of ~10 μm in 2g shrimp.
This “net” could trap diatoms, but probably not smaller cells like Nannochloropsis and Synechococcus. (Kent et al. 2011)
Selective Breeding in Disease Mitigation
Taura Syndrome Virus (TSV) • • • •
ssRNA virus h2 estimates ~ 0.2 (low - moderate) Good selection response (>10% per generation) Commercially available families exhibit >90% survival in per os laboratory challenges 100 80 60
Generation 7 Mean = 84% CV = 13.6%
40 20 0 100 80
Generation 2 Mean = 44% CV = 43.3%
60 40 20 0
Shrimp families
White Spot Syndrome Virus (WSSV) • dsDNA virus • h2 estimates typically < 0.1 (very low) • Mass selection attempts in the Americas Family
WSSV virion mean size = 275 nm
Treatment
Survival
LP-1
Negative control
49 of 50 (98%)
LP-2
Negative control
91 of 96 (95%)
LP-3
Negative control
68 of 68 (100%)
Kona
WSSV positive control
0 of 20 (0%)
LP-1 (2 tanks)
WSSV challenge
24 of 104 (23%)
LP-2 (2 tanks)
WSSV challenge
74 of 129 (57%)
LP-3 (2 tanks)
WSSV challenge
34 of 130 (26%)
Modified from Cuéllar-Anjel et al. 2012
Breeding for Bacterial Resistance • Lessons learned from insect literature – pest insects bred for toxin resistance (Bt endotoxin)
• Need data on quantitative genetics – phenotypic variation – heritability estimates – correlation with other traits
• Possible pathways for selection – Resistance (host “fights” pathogen and reduces pathogen load) – Tolerance (limit the harm caused by a given pathogen burden – reduced effect of toxin)
UAZ’s AHPND Challenge Room • 90-L aquaria and 1000-L tanks • Internal biological filter with crushed oyster shell
• Feed pellets immersed in culture of V. parahaemolyticus • Culture contains known concentration of bacterial cells, so bacterial dose/gram feed is known • Preliminary results: – – – –
LD50 = 105 cells/mL All shrimp died at 106 cells/mL 108 cells/mL common in ponds Generation time of 8-10 minutes
Biofloc System Pathogens Vibrio spp. - gram-negative bacteria - ubiquitous in Biofloc systems - cuticle infection appears as melanized lesions, can also infect a single organ or be systemic - treatment may include medicated feed (various UAZ cases – Biofloc systems in USA)
Biofloc System Pathogens Fusarium spp. - naturally occurring saprophytic fungi - infection facilitated by cuticle wounding - infection appears as melanized, nodular lesions on cuticle, gills, or appendages - fungal hyphae visible by wet mount (UAZ case from 2008 – Biofloc farm in USA)
Challenges with Multi-trait Selection There are always tradeoffs when adding trait(s) to a selection program!
Stewart et al. 1999
Number of Traits Selected by Species (modified from Gjedrem et al. 2012) Species
# programs
Common carp Rohu carp Silver barb Tilapia Nile Tilapia blue Tilapia red Tilapia O. shiranus Channel catfish African catfish Striped catfish Atlantic salmon Chinook salmon Coho salmon Rainbow trout European whitefish Turbot Atlantic cod European seabass Sea bream Freshwater prawn P. monodon P. vannamei Abalone Oysters Mussel
8 1 1 20 2 4 1 1 1 1 13 2 4 13 1 2 3 3 4 2 3 4 3 3 1
# families per program 76 60–70 – 229 90 125 51 200 70 182 280 100 133 206 70 60 110 100 100 82 212 197 210 48 60
Average # traits 2.0 2 1 3.6 2.0 4.0 1.0 4 1 3 5.4 1.5 2.7 5.2 2.0 1.0 4.0 5 6 1 – 2.0 1.7 4.3 3.0
Genetic Diversity & Inbreeding
Possible Limited Genetic Diversity • Breeding companies limit diversity of broodstock for germplasm protection (narrow genetic base) • Random loss of diversity (genetic drift) • Inbreeding – High fecundity – Intense selection – Unknown pedigree
Inbreeding Inbreeding can accumulate rapidly in non-pedigreed populations – especially those with a narrow genetic base
0
0
Broodstock
0
0
1st generation
.125
.125
2nd generation
.375
.375
3rd generation
0
0
0
0
.188
.5
0
Breeding at GN
0
0
0
.125
0
0
.250
.250
.125
.312
On-farm breeding
Inbreeding
Negatively impacts commercially important traits (inbreeding depression) Trait
Inbreeding Depression (%)
Hatch Rate
-13
Survival – Hatchery
-11
Survival – Growout
