Heterosis and heritability estimates for the survival of the Pacific white shrimp(Litopenaeus vannamei) under the commercial scale ponds

The aim of the present study is to detect the potential of the base population from diallel crosses of eight introduced strains of the Pacific white shrimp（Litopenaeus vannamei） for improving the yield. Heterosis and heritability were estimated for pond survival at commercial farm conditions for the base population that included 207 full-sib families from a nested mating design by artificial insemination. Among all the hybrids,the heterosis ranged from –11.37%（UA1×UA2） to 20.53%（UA3×SIN） with an average of 0.953%. The results showed that more than half of the hybrids（51.85%） have negative heterosis for survival rate, but most of the hybrids with positive heterosis have high estimates. The high proportion of negative heterosis for survival rate reminders us that the survival trait also should be considered in the crossbreeding program to avoid yield decrease. However, high positive heterosis manifested in most of the hybrids for survival indicates the usefulness of these hybrids for improving the survival to obtain higher yield by crossbreeding in this breeding program. The heritability estimate for pond survival was 0.092±0.043 when genetic groups were included in the pedigree, and it was significantly different from zero（P〈0.05）. The results from this study also indicated that significant improvement for survival is possible through selection in L. vannamei.

The Positive Effects of Proprietary Undenatured β-Glucans on Stressed Marine Life

The safety of beta-glucans, including undenatured beta-glucan (UDBG), has been exhaustively studied over the recent past and has shown to be safe and efficacious in rodents as well as in humans with less than optimal immune systems. As such, we sought to find the effect of UDBG on certainly stressed crustaceans and fish. The survival of shrimp larvae fed the UDBG and other diets was measured on day 16. The diet containing 11.7% UDBG reduced larvae mortality by 18%;which is almost twice as much as the mortality reduced by the MacroGard diet, and up to 19.5% less than a standard Commercial Diet. In an effort to understand how UDBG protects against stressed marine life, UDBG was given to LPS-challenged trout. The UDBG positively influenced the level of transcription of several genes relevant to the immune system and overall health of the trout. The experimental findings indicated that UDBG: 1) modifies inflammatory responses, 2) makes responses more flexible and versatile, 3) protects from cellular stress, and 4) enhances “effector” mechanisms. Importantly, there was no evidence of immune system over-activity.