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Different scenarios for calculation of the feed conversion ratio (FCR)

 
Scenario Feed > 0 Feed = 0
ΔBiomass > 0 FCR > 0 FCR = (+)0
ΔBiomass = 0 FCR = x/0 = ∞ FCR = 0/0
ΔBiomass < 0 FCR < 0 FCR = (−)0



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Equations proposed for calculation of the feed conversion ratio (FCR) and the FCR index (iFCR)

 
ΔBiomass Feed FCR Formulas for FCR1 Formulas for iFCR
>0 >0 >0
0 = (+)0 0.1
= 0 >0 = x/0 EMFR×97+9
= 0 = 0/0 9
<0 > 0 <0
= 0 = (−)0
1EMFR = estimated monthly feeding rate.



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Exclusion rules for registers to calculate the production and management index (PMI)

 
Criteria1 Cause of exclusion Excluded
ADGr < 0 Loss of weight 52
ADGr ≥ 0.5 Growth rate too high 2
EMM ≥ 0.30 Excessive estimated mortality 41
EMM ≥ 0.20, period ≤ 7 d Excessive estimated mortality in a nonrepresentative period of time 16
FCR > 50 FCR too high 14
0.1 > FCR > 0 FCR too low 18
ΔBiomass = 0, feed = 0, period ≤ 15 d Noncalculable FCR and period too short 165
EMFR > 3 EMFR too high (equivalent to a daily feeding rate greater than 10% of biomass) 0
Density > 500 fish/m3, biomass > 200 kg/m3 Fish density too high 8
Density < 50 fish/m3, biomass < 10 kg/m3 Fish density too low 9
Density < 100 fish/m3, biomass < 1 kg/m3 Fish density too low 10
Fish movements Changes in population size 98
1ADGr = relative average daily growth; EMM = estimated monthly mortality; FCR = feed conversion ratio; EMFR = estimated monthly feeding rate.



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Weight (g) stratified by tilapia variety

 
Variety n % Mean1 SD Median Minimum CI95% Maximum
Black 4,476 52.0% 426.9a 315.1 365.0 2 11.0 1,085.0 1,590
Red 3,881 45.1% 156.8c 136.6 130.0 2 4.0 453.0 1,100
Spotted 143 1.7% 305.9b 259.0 271.0 2 3.0 903.4 1,035
Mixed 114 1.3% 280.5b 124.7 274.0 6 55.9 544.0 850
Total 8,614 100% 301.3 280.9 220.0 2 6.0 1000.0 1590
a–cDifferent superindexes in the same column show significant differences comparing pairs of results with the Mann-Whitney U test.
1Significance of the Kruskal-Wallis test, P < 0.001.



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PMI stratified by tilapia varieties

 
Variety n Mean1 SD Median Minimum 95% CI Maximum
Black 4,288 1.0248 0.3759 1.0243 0.2672 0.3693 1.8266 2.832
Red 3,660 1.1661 0.3493 1.1437 0.2633 0.4028 2.0158 3.550
Total 7,948 1.0898 0.3706 1.0894 0.2633 0.3758 1.9144 3.550
1Significance of Mann-Whitney U test, P < 0.001.



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Production and management index stratified by tilapia varieties and weight categories

 
Black tilapia
Red tilapia
Item n Mean SD Median n Mean SD Median P-value
Weight
    ≤20 g 136 1.1385b 0.5853 1.0292 448 1.0894c 0.4999 1.1662 0.360
    20–49 g 202 1.2495a 0.3360 1.2374 484 1.3509a 0.3401 1.3028 0.001
    50–119 g 416 1.1262b 0.3708 1.0846 750 1.2476a,b,c 0.2641 1.2018 <0.001
    120–299 g 1,054 1.0373c,d 0.3264 1.0305 1,453 1.1175c 0.3014 1.0826 <0.001
    300–599 g 1,163 0.9848d,e 0.3430 0.9802 498 1.0739c 0.3437 1.0570 <0.001
    600–999 g 1,103 0.9549e 0.3897 0.9710 22 1.1418b,c 0.2988 1.0783 0.021
    ≥1,000 g 214 1.0591c 0.4318 1.1176 5 1.3124a,b 0.7224 1.2809 0.376
    Total 4,288 1.0248 0.3759 1.0243 3,660 1.1661 0.3493 1.1437 <0.0011
P-value <0.0012 <0.0012
a–eSuperindexes in the same column show significant differences comparing pairs of results with the Mann-Whitney U test.
1Significance of the Mann-Whitney U test.
2Significance of the Kruskal-Wallis test.



View Full Table | Close Full ViewTable 7.

Production and management index stratified by season (using only black and red tilapias)

 
Variety n Mean1 SD Median Minimum CI95% Maximum
Rainy 5,455 1.0847 0.3787 1.0856 0.2633 0.3732 1.9216 3.5495
Dry 2,493 1.1011 0.3522 1.0944 0.2846 0.3815 1.8854 2.7735
Total 7,948 1.0898 0.3706 1.0894 0.2633 0.3758 1.9144 3.5500
1Significance of Mann-Whitney U test, P = 0.026.