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A family-based selection program was initiated at the National Center for Cool and Cold Water Aquaculture in 2005 to improve resistance to bacterim cold water disease (BCWD) in rainbow trout. The objective of this study was to estimate response to 2 generations of selection. A total of 14,841 juvenile fish (BW = 3.1 g; SD = 1.1 g) from 230 full-sib families and 3 randomly mated control lines were challenged intraperitoneally with Flavobacterium psychrophilum, the bacterium that causes BCWD, and mortalities were observed for 21 d. Selection was applied to family EBV derived from a proportional-hazards frailty (animal) model while constraining rate of inbreeding to [less than or equal to] 1% per generation. After adjusting for nongenetic effects, survival rate of select-line families increased by 24.6 [+ or -] 6.8 and 44.7 [+ or -] 6.7 (cumulative) percentage points after 1 and 2 generations of selection, respectively (P < 0.01). Genetic trend, estimated from a linear animal model that fit genetic group effects, was 19.0 [+ or -] 4.1 percentage points per generation and approached significance (P = 0.07). Heritability estimates from the proportional-hazards frailty model and linear animal model were similar (0.22 and 0.23, respectively), and family EBV from both models were highly correlated (-0.92). Accuracy of selection, estimated as the correlation between midparent EBV and progeny survival rate, was 0.20 (P < 0.01) for the proportional-hazards frailty model and 0.18 (P = 0.01) for the linear animal model. Accuracy estimates were not different (P = 0.81) between the models. This study demonstrates that selective breeding can be effective for improving resistance to experimental BCWD challenge in rainbow trout. Key words: disease resistance, Flavobacterium psychrophilum, heritability, rainbow trout, selection, survival doi: 10.2527/jas.2009-2538

As a first step toward the genetic mapping of QTL affecting stress response variation in rainbow trout, we performed complex segregation analyses (CSA) fitting mixed inheritance models of plasma cortisol by using Bayesian methods in large full-sib families of rainbow trout. To date, no studies have been conducted to determine the mode of inheritance of stress response as measured by plasma cortisol response when using a crowding stress paradigm and CSA in rainbow trout. The main objective of this study was to determine the mode of inheritance of plasma cortisol after a crowding stress. The results from fitting mixed inheritance models with Bayesian CSA suggest that 1 or more major genes with dominant cortisol-decreasing alleles and small additive genetic effects of a large number of independent genes likely underlie the genetic variation of plasma cortisol in the rainbow trout families evaluated. Plasma cortisol is genetically determined, with heritabilities of 0.22 to 0.39. Furthermore, a major gene with an additive effect of -42 ng/mL (approximately 1.0 genetic SD) is segregating in this rainbow trout broodstock population. These findings provide a basis for designing and executing genome-wide linkage studies to identify QTL for stress response in rainbow trout broodstock and markers for selective breeding. Key words: Bayesian analysis, major gene, plasma cortisol, rainbow trout, segregation analysis, stress response doi: 10.2527/jas.2008-1616

The contribution of sex steroids to nutrient partitioning and energy balance during gonad development was studied in rainbow trout. Specifically, 19-mo old triploid (3N) female rainbow trout were fed treatment diets supplemented with estradiol-17β (E2), testosterone (T), or dihydrotestosterone at 30-mg steroid/kg diet for a 1-mo period. Growth performance, nutrient partitioning, and expression of genes central to growth and nutrient metabolism were compared with 3N and age-matched diploid (2N) female fish consuming a control diet not supplemented with steroids. Only 2 N fish exhibited active gonad development, with gonad weights increasing from 3.7% to 5.5% of body weight throughout the study, whereas gonad weights in 3N fish remained at 0.03%. Triploid fish consuming dihydrotestosterone exhibited faster specific growth rates than 3N-controls ( P < 0.05). Consumption of E2 in 3N fish reduced fillet growth and caused lower fillet yield compared with all other treatment groups ( P < 0.05). In contrast, viscera fat gain was not affected by steroid consumption ( P > 0.05). Gene transcripts associated with physiological pathways were identified in maturing 2N and E2-treated 3N fish that differed in abundance from 3N-control fish ( P < 0.05). In liver these mechanisms included the growth hormone/insulin-like growth factor (IGF) axis ( igf1 , igf2 ), IGF binding proteins ( igfbp1b1 , igfbp2b1 , igfbp5b1 , igfbp6b1 ), and genes associated with lipid binding and transport ( fabp3 , fabp4 , lpl , cd36 ), fatty acid oxidation ( cpt1a ), and the pparg transcription factor. In muscle, these mechanisms included reductions in myogenic gene expression ( fst , myog ) and the proteolysis-related gene, cathepsin-L, suggesting an E2-induced reduction in the capacity for muscle growth. These findings suggest that increased E2 signaling in the sexually maturing female rainbow trout alters physiological pathways in liver, particularly those related to IGF signaling and lipid metabolism, to partition nutrients away from muscle growth toward support of maturation-related processes. In contrast, the mobilization of viscera lipid stores appear to be mediated less by E2 and more by energy demands associated with gonad development. These findings improve the understanding of how steroids regulate nutrient metabolism to meet the high energy demands associated with gonad development during sexual maturation. [ABSTRACT FROM AUTHOR]

Abstract: Canthaxanthin (CXN) is a red pigment, which is broadly used in broiler chickens for skin pigmentation, in laying hens for the coloration of egg yolks and in poultry breeders for improving the antioxidant status of eggs. In order to investigate the safety of this feed additive under conditions of an accidental oversupply, studies in all target poultry categories were performed, comparing a non-supplemented control to treatments with the respective recommended dietary supplementation of CXN and a ten times overdose of the recommended CXN level. Performance, mortality and a number of hematological and blood biochemical variables as well as post-mortem evaluations were taken as parameters to assess the effects of CXN overdosing. In broilers performance was not influenced by treatment with CXN at 25 or 250mg/kg feed. The hematological traits of the CXN groups were either not different from the control or remained within the normal physiological range. Concentration of CXN in blood plasma increased (P<0.001) in a proportional manner to the CXN supplementation in the feed. Some blood chemistry variables responded to the CXN treatments, but remained close to normal values. No mortality occurred in the overdose treatment and neither regular health examination nor post-mortem evaluation revealed any detrimental effects of CXN on broiler health. Laying performance of hens was not influenced by CXN supplementation with 8 or 80mg/kg feed. The CXN content in eggs responded linearly to supplementation (P<0.001). None of the measured blood variables were affected by treatment. The dissection of experimental birds showed indications of friable livers in the CXN supplemented hens, but no other effects on gross-morphology were observed. In breeders body weight and productive performance were not different among treatments. Egg weight with 6mg CXN/kg feed was higher (P=0.045) than in the control group. The CXN content in eggs increased proportionally to CXN supplementation (P<0.001). No differences in fertility were observed among the treatments, but hatchability of fertile eggs was depressed by overdosing CXN (P<0.001). Certain hematology and blood chemistry traits differed between the treatments, but the values remained within the normal range. The final post-mortem examination did not reveal any health problems in these breeders, which were related to the dietary treatments or attributable to the high CXN contents. In summary CXN at dietary supplementation doses of up to ten times the recommended levels is safe for broilers, laying hens and poultry breeders. [Copyright &y& Elsevier]

An adequate supply of all nutrients, including proteins, fats, carbohydrates, vitamins, minerals and water, has to be provided to support maximum productivity of laying hens. Among these nutrients, vitamins are particularly important, since they are essential for optimum health as well as normal physiological functions of the hens. As most vitamins cannot be synthesized by poultry in sufficient amounts to meet physiological demand, they must be obtained from the diet. The absence from feed or impaired absorption or utilization of vitamins can lead to specific deficiency disorders. This review reports on the occurrence and the physiological functions of all vitamins and summarizes research related to the requirements for and the beneficial effects of supplemental vitamins for laying hens. The recommendations for dietary supplementation of vitamins from various organizations are compared and put into perspective of modern poultry genotypes and current husbandry conditions. As there is good evidence that the minimum dietary vitamin levels, required to prevent clinical deficiencies may not support optimum health, performance and welfare of poultry under today's conditions it is recommended to include a safety margin to the vitamin requirements of laying hens. [ABSTRACT FROM PUBLISHER]