Genomic polymorphisms at the crhr2 locus improve feed conversion efficiency through alleviation of hypothalamus-pituitary-interrenal axis activity in gibel carp(Carassius gibelio)

Improvement in fish feed conversion efficiency(FCE)is beneficial for sustaining global food fish supplies.Here,we show that a set of polymorphisms at locus of the corticotropin releasing hormone receptor 2(crhr2),which is involved in hypothalamuspituitary-interrenal(HPI)axis signaling,is associated with improved FCE in farmed allogynogenetic gibel carp strain CAS Ⅲ compared with that in the wild gibel carp strain Dongting(DT).This set of polymorphisms downregulates the expression levels of crhr2 mRNA in the brain and pituitary tissues in gibel carp strain CAS Ⅲ compared with those in strain DT.Furthermore,compromised HPI axis signaling is observed in gibel carp strain CAS Ⅲ,such as decreased α-melanocyte stimulating hormone protein levels,plasma cortisol content,and stress responses.Moreover,enhanced activation of protein kinase B/mammalian target of rapamycin complex 1 signaling observed in the muscle tissue of strain CAS Ⅲ in comparison to that in strain DT indicated elevated anabolic metabolism in strain CAS Ⅲ.Thus,these studies demonstrate that the genetic markers associated with compromised HPI axis signaling,such as crhr2,are potentially useful for genetic selection toward improvement in farmed fish growth and FCE,which would reduce fishmeal consumption and thereby indirectly facilitate sustainable fisheries.

Growth and Diet Utilization Efficiencies of Overwinter Juvenile Mud Crabs Fed with Different Diets

[Objectives]To study the utilization efficiency of different diets for juvenile Scylla paramamosain.[Methods]Low-value fish,shrimp,clam and clamworm were fed to overwintering young mud crabs,and the performance of the feed was evaluated by growth,feed utilization and energy allocation.[Results]Shrimp-fed mud crabs showed the best growth performance,while fish-fed mud crabs showed the worst growth performance and converted the least protein and energy for growth.Shrimp-fed mud crabs molted more frequently,and the dry matter mass and energy of Exuviation were significantly higher than those of fish-fed mud crabs.The shrimp-fed crabs also had significantly higher food intake than those fish-fed crabs.The order of feed conversion efficiency(FCE)of fish-fed mud crabs was Polychaete>clam>shrimp>fish,while the order of FCE calculated with FCE-P and FCE-E was Polychaete>clam>shrimp>fish.Fish-fed mud crabs had the least energy intake and the least energy for growth,molting,excretion,metabolism,and feces.Among the four treatments,the mud crabs fed on Polychaete had the largest proportion of energy used for growth,while the mud crabs fed on fish had the largest proportion of energy used for molting.The proportion of energy consumed by mud crabs fed on Polychaete was the smallest,which may be the main reason for the higher FCE-P and FCE-E of mud crabs fed on Polychaete.[Conclusions]The results of this experiment showed that the utilization of low-value fish by mud crabs was the worst,suggesting that fish should not be used as control or reference food when studying the formula feed of mud crabs.

Study of the Compensatory Growth Following Starvation of Juvenile Golden Pompano Trachinotus ovatus

A starvation trial was conducted to determine compensatory growth of the juvenile golden pompano Trachinotus ovatus which were deprived of food for 1, 2, 5 and 7 days respectively. The results of tests in outdoor cement pools and net pens showed that, in the first 15 days and 30 days, the growth of 1 day and 2 days-deprived groups was probably the same with that of control group, which accorded with fully compensatory description. However, the weight of 5 days and 7 days-deprived fingerlings were lower than that of the control group, which accorded with the description of the partial compensatory growth. As the starvation prolonged, feed conversion efficiency of the starved groups increased and was higher than the control group. Meanwhile, feeding rate also increased, but the fish of 1 day and 2 days-deprived groups was lower than that of the control group, and feeding quantity reduced and was lower than that of the control group. It suggested that the mechanism of compensatory growth was mainly due to improving feed conversion efficiency. Fish biochemical composition was analyzed： the water content and ash of fish sample increased due to starvation, while the lipid and protein decreased. The loss of lipid was greater than that of the protein, and the biochemical composition of fish in each group was restored to the control level by the end of the experiment. It suggested that Trachinotus ovatus may mainly consume lipid during the period of starvation.

Feed profile analysis of oil palm‐integrated beef cattle farming systems by metabolic energy budgeting and implications for beef production and pastoral system design

Background:Oil palm is a tropical crop with worldwide plantings approaching 20 million ha and large areas in Indonesia,Malaysia and Thailand.The plantations are readily managed as silvopastoral systems incorporating cattle grazing(Oil Palm Silvopastoral System for Cattle,OPSC)but there is a need for analytical tools and data to understand system herbage supply and feed conversion efficiency(FCE).Methods:Metabolic energy budgeting was used to estimate herbage harvested by cattle in three OPSC subsystems,9 and 12 years after oil palm establishment,and FCE of the subsystems was determined.Understorey herbage was also analysed for nutritive value,botanical composition and herbage accumulation within one grazing‐regrowth cycle.Results:The herbage‐harvested estimate was 2.0−2.4 t dry matter(DM)ha^(-1) year^(-1) for 9 year old subsystems and 1.4-1.7 tDMha^(-1) year^(-1) for a 12 year old subsystem.Herbage metabolisable energy(ME)was 8.3−8.5 MJ kg^(-1) DM and crude protein(CP)was 15%-16%DM.FCE values for subsystems ranged from 32 to 94 kg DM kg^(-1) liveweight‐gain.Conclusions:Herbage DM yield is declining,while herbage ME is marginal but CP is adequate.FCE is suboptimal but can be optimised by defining the trajectory of declining herbage production with canopy closure as plantations age and matching stocking rate to herbage supply using a comparativestocking‐rate‐type statistic.