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Streptococcus iniae and S. agalactiae are both economically important Gram positive bacterial pathogens affecting the globally farmed tilapia (Oreochromis spp.). Historically, control of these bacteria in tilapia culture has included biosecurity, therapeutants and vaccination strategies. Genetic gains in performance traits have been realized for Nile tilapia (Oreochromis niloticus) and interest in breeding for disease resistance has recently received attention. The goal of this study was three fold: 1) to verify previous results demonstrating heritability of S. iniae resistance in Nile tilapia families using increased numbers of fish per family; 2) to determine if realized genetic gain in resistance and/or susceptibility to S. iniae can be obtained following positive assortative mating between parents with high or low estimated breeding values (EBV); and 3) to determine if resistance to S. iniae and S. agalactiae capsular type Ib is genetically correlated. A total of 144 and 130 full sib families were challenged intraperitoneally with S. iniae and intramuscularly with S. agalactiae Ib, respectively. Cumulative mortality at test end was 46% for S. iniae and 68% for S. agalactiae. There was a high additive genetic component found for survival in fish injected with S. iniae (estimated heritability 0.52 ± 0.12) and with S. agalactiae (estimated heritability 0.38 ± 0.11). The S. iniae challenge results confirmed additive genetic variation in resistance of Nile tilapia to S. iniae. We also demonstrated via assortative mating that genetic gain for survival to S. iniae is possible. The genetic correlation between resistance to S. iniae and S. agalactiae Ib was not significantly different from zero (r g =-0.30 ± 0.19). The lack of correlation suggests if resistance to both Streptococcus sp. is desired, selection for both traits must be simultaneous. Selection of fish to improve survival to Streptococcus sp. may require a thorough understanding of the type of pathogen prevalent in the region so that custom genetic material may be tailored to meet the needs of the individual farm and/or region.

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Streptococcus iniae is an etiologic agent of streptococcal disease in tilapia and is one of several Streptococcus spp. that negatively impact worldwide tilapia production. Methods for the prevention and control of S. iniae include vaccines, management strategies, and antibiotics. A complimentary preventative approach may include selective breeding for disease resistance, but the potential for this is unknown in tilapia. This study was initiated to challenge Nile tilapia (Oreochromis niloticus) families for estimation of genetic parameters for resistance to S. iniae. A total of 143 full-and paternal half-sib families (avg. 176 g, sd = 50 g) were divided into two groups with each containing on average 9 fish per family. The challenge was designed with the intent to utilize fish injected with S. iniae (Group 1) as shedder fish to transfer the bacterium to cohabitated fish (Group 2). Tilapia from Group 1 were challenged by intraperitoneal injection with a volume containing 1.15 × 10 8 colony-forming units S. iniae per fish, and then cohabitated with tilapia from Group 2 in a single tank. Accumulated mortality at the end of the experiment was 60% for the fish challenged by injection and 6.4% for fish challenged by cohabitation. The results revealed high variation for mean survival of the families injected with S. iniae (range from 0% to 100%, CV 69%). The estimated heritability of post-challenge survival in Group 1 was 0.42 ± 0.07 on the observed binary scale and 0.58 ± 0.09 on the underlying liability scale, derived from fitting a linear animal model and a sire-dam threshold model, respectively. In summary, substantial additive genetic variation in resistance to S. iniae was observed when fish were challenged by injection, and this suggests promise for genetic improvement of tilapia for resistance to S. iniae through selective breeding.

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-Feed withdrawal during the warmest part of the day (09:00 to 16:00 h) was compared with the distribution of ground corn and commercial feed consumed ad libitum by control broilers from 28 to 42 d exposed to tropical climatic conditions (averaged Ta = 25 °C; Relative Humidity (RH) = 72%). From 16:00 to 09:00 h, a continuous illumination was in the poultry shed and the chickens received a commercial diet. Each diet was supplied to 7 pens of 14 unsexed broilers. Both feed withdrawal and corn distribution during the day period reduced growth (P < 0.01) and deteriorated feed conversion (P < 0.01) compared to the ad libitum control. At the age of 41 d, the average body temperature (Tb) at 14:00 h in the control group was 42.56 °C. It was higher (P < 0.002) than that recorded in the corn fed group (42.27 °C) and the feed withdrawal chickens (42.11 °C). These effects measured in 4-6 week-old broilers exposed to a moderate tropical climate, illustrate the limitation of feed restriction and sequential feeding under practical conditions. Further research is needed to study the diurnal distribution of corn or feed withdrawal coupled with a balanced diet richer in essential amino acids than the commercial diet during the nocturnal period. les phases les plus chaudes de la journée (09:00 à 16:00 h) a été comparé à la distribution ad libitum de maïs broyé ou d'un aliment commercial pendant la même période, chez des poulets de chair élevés en milieu tropical (Température moyenne = 25 °C ; HR moyenne = 72 %) entre 28 et 42 jours d'âge. Entre 16:00 et 09:00 h tous les poulets recevaient l'aliment commercial ad libitum et le poulailler était continuellement éclairé. Chaque régime expérimental a été distribué à 7 parquets de 14 poulets non sexés. Le retrait d'aliment comme la distribution de maïs ont réduit la croissance (P < 0,01) et détérioré l'indice de consommation (P < 0,01) par rapport aux témoins nourris ad libitum. A l'âge de 41 jours, la température corporelle moyenne mesurée à 14:00 h était de 42,56 °C chez les témoins. Elle était supérieure (P < 0,002) à celle mesurée chez les poulets recevant du maïs (42,27 °C) ou mis à jeun (42,11 °C). Ces effets mesurés entre 4 et 6 semaines d'âge chez des poulets exposés à un climat tropical modéré, illustrent les limites du retrait de l'aliment ou l'alimentation séquentielle dans des conditions pratiques. Des recherches complémentaires associant à la distribution de maïs ou au jeûne diurne, un régime complémentaire nocturne plus riche en acides aminés indispensables que le régime commercial sont souhaitables.poulet de chair / température corporelle / alimentation séquentielle / rythme / climat chaud

For a long time, the planning of power systems has considered technical and economic aspects related to Supply Side Management. Given that this traditional planning approach is not very flexible, and due to new technological trends like the adoption of smart grids, it has become necessary for demand to play an active role in the operation of power systems. This raises the need to implement a new process for power system planning, focusing on technologies such as microgrids with Demand Side Management, which contribute to the sustainable development of communities. In this paper, a comprehensive review of microgrid planning, considering energy end‐user participation through Demand Response, is carried out. In addition, the main features and implications of Demand Response programs in microgrid planning are presented. As a contribution, in order to trigger a paradigm shift on how power systems are planned, the benefits of bottom‐up microgrid planning are presented.