Reduced growth,condition factor and body energy levels in Atlantic salmon Salmo salar L. during their first spring in the sea

We have investigated the feed intake and growth in autumn‐transferred Atlantic salmon (S0) during their first spring in the sea, a period of low performance in commercial production. We have compared the results with those obtained from spring‐transferred smolt (S1), in order to determine whether this reduction in performance is accompanied by changes in nutrient retention, levels of muscle fat, energy status or condition factor (CF). The practical importance of the results obtained in the small‐scale experiments was evaluated by studies performed at two commercial farms, both using S0 salmon. The feeding rate, rate of growth and degree of feed utilization were low during the first spring in sea, for both S0 and S1 smolt. In both commercial farms, the apparent feed intake in S0 was reduced by approximately 50% in the spring. This low‐performing period coincided with reduced fat and energy retention, low levels of muscle fat and poor CF. Fat retention was reduced from 44.8% (March–May) to 15.4% (May–June) in S0, whereas protein retention did not change, indicating that the energy demand was high during the first spring in sea.     

Metals in sediment of lakes in Northern Sweden

The concentrations of Pb, Cu, Zn, Cd, and Fe were measured in sediment from 54 soft water lakes in the inland part of central and northern Sweden in order to study the regional impact of metals to lakes. An evident regional distribution due to environmental pollution was found concerning Pb, Cd, Zn, and Cu. In the southern part of the studied region, the enrichment factors in the top sediment layers were about 50, 7, 4, and 2, respectively. Further to the north, the contamination of the top sediments gradually decreased. In a large part of the northern region, the sediment analyses showed no general vertical gradients of Zn and Cu, indicating non-polluted conditions. Lead was the most widespread and pronounced pollutant with marked enhancements in most parts of the region. In the northernmost areas, the top sediment showed increased concentrations of Pb and Cd of about a factor of 2, suggesting that strictly non-polluted conditions concerning these two metals can not be found anywhere in the studied region. The regional distribution of Fe differed from the other metals and gave no evidence of a large-scale anthropogenic contribution. The natural enrichment of Pb, Cu, Zn, and Cd in the surface sediment is probably of minor importance in these kinds of lakes. The regional distribution of metals in sediments indicate that there is a large scale impact of Ph, Cd, Zn, and Cu on Swedish forest lakes, caused by anthropogenic factors.     

Maternal effects on daily weight gain and ultrasonically recorded backfat in swedish landrace,swedish yorkshire,and swedish hampshire purebred pigs

The aim of this study was to estimate the genetic association between direct and maternal effects for important economic traits measured early and late in the growth period; daily gain (DG) between birth and 12 weeks of age (DG_0-12), between 12 weeks of age and ultrasonic test (at approx. 100 kg; DG_12-UT), between birth and ultrasonic test (DG_0-UT); and backfat at ultrasonic test (BF). Records from Landrace (L; 39,130), Yorkshire (Y; 33,737), and Hampshire (H; 17,832) pigs born between 1997 and 2001 from the Swedish breeding organization Quality Genetics databank were available. Univariate and bivariate analyses were applied. Two statistical models were used. The first model applied for all traits, included the random effect of herd-birth year-birth month combination, the litter environmental effects, and the direct genetic effects. The second model applied only for DG_0-UT and BF, and included also the maternal genetic effects. Based on the first single-trait model, estimates of direct heritability (h²) were 0.12, 0.09, and 0.43 for DG_0-12; 0.16, 0.22, and 0.41 for DG_12-UT; 0.18, 0.24, and 0.28 for DG_0-UT; and 0.37, 0.42, and 0.43 for BF in the L, Y, and H breeds respectively. Estimates of litter environmental effects ranged from 0.05 to 0.17. Based on the second single-trait model, the maternal genetic effects were 0.03, 0.05, and 0.09 for DG_0-UT, and 0.02, 0.01, and 0.04 for BF. Estimates of direct h² from the second model were lower and ranged from 0.14 to 0.42 for all traits across breeds. Moderate-low genetic correlation between DG_0-12 and DG_12-UT (?0.25 to 0.40) and high correlation between DG_12-UT and DG_0-UT (0.84 to 0.96) were noted in all three breeds together with less maternal influence on traits expressed late in life. This indicates the possibility to treat early growth rate as a maternal trait, and late or overall growth rate as a direct trait in the breeding evaluation.     

Effect on Carcass Traits of Selection for Increased Lean Tissue Growth Rate in Swine on Low or High Dietary Protein Levels

Pigs were selected for lean tissue growth rate (LTGR) in two lines, fed low (LP line) or high (HP line) protein levels. This investigation comprised 92 and 95 pigs, respectively, from generation 3 of the two lines, tested on low, medium and high protein diets between 25 and 105 kg body weight. HP compared to LP line pigs had higher ham percentage (P=0.02), thinner backfat (P=0.003) and lower intramuscular fat content (P = 0.01). A positive correlated response (P=0.02) in osteochondrosis score of femur (OCDf) was found in the HP line. There were unfavourable correlations (P<0.05) between OCDf and performance in the LP line. There were numerically negative correlations between length of the small intestines (LSI) and feed conversion ratio in both lines, and a numerically positive correlation between LSI and daily weight gain in the HP line. There were no interactions between selection lines and test diets. The present results indicate that selection for LTGR ought to be performed on a high protein feeding regime.     

Prevalence and subtypes of Influenza A Viruses in Wild Waterfowl in Norway 2006-2007

The prevalence of influenza A virus infection, and the distribution of different subtypes of the virus, were studied in 1529 ducks and 1213 gulls shot during ordinary hunting from August to December in two consecutive years, 2006 and 2007, in Norway. The study was based on molecular screening of cloacal and tracheal swabs, using a pan-influenza A RT-PCR. Samples found to be positive for influenza A virus were screened for the H5 subtype, using a H5 specific RT-PCR, and, if negative, further subtyped by a RT-PCR for the 3''-part of the hemagglutinin (HA) gene, encompassing almost the entire HA2, and the full-length of the neuraminidase (NA) gene, followed by sequencing and characterization. The highest prevalence (12.8%) of infection was found in dabbling ducks (Eurasian Wigeon, Common Teal and Mallard). Diving ducks (Common Goldeneye, Common Merganser, Red-breasted Merganser, Common Scoter, Common Eider and Tufted Duck) showed a lower prevalence (4.1%). In gulls (Common Gull, Herring Gull, Black-headed Gull, Lesser Black-headed Gull, Great Black-backed Gull and Kittiwake) the prevalence of influenza A virus was 6.1%. The infection prevalence peaked during October for ducks, and October/November for gulls. From the 16 hemagglutinin subtypes known to infect wild birds, 13 were detected in this study. Low pathogenic H5 was found in 17 dabbling ducks and one gull.     

Modeling and Simulation of Food Products in Superchilling Technology

The food superchilling process is of increasing importance because of its benefit in achieving food quality and extending shelf life of food products. The rate of the superchilling process is critical to the products’ quality and to the productivity of the process, and therefore the superchilling dynamics are of extreme importance. The objective of this work was to develop a one-dimensional implicit finite difference numerical model for predicting partial freezing time necessary to achieve an optimal degree of superchilling in foods and to validate the model experimentally. The evaluation of degree of superchilling was determined using finite slab and measured by using a calorimetry method. There is a good level of agreement between numerical simulation and laboratory experimental results.     

Reduction of early sexual maturation in male S0 Atlantic salmon (Salmo salar L.) by dietary supplementation of tetradecylthioacetic acid (TTA)

Effects of dietary tetradecylthioacetic fatty acid (TTA) on muscle fat, development of gonads and early sexual maturation in S0 Atlantic salmon during the first year in sea were investigated. TTA (0.5% w/w) was added to the feeds for 8 weeks in the spring. In May, at the end of the TTA‐feeding period, the fish in the TTA group had significantly (P < 0.05) less fat (10.1%) stored in muscle compared with the control group (10.8%). In September, mean male gonadosomatic index (GSI) in maturing fish in the TTA group was found to be lower compared with the maturing fish in the control group (P = 0.05). On the basis of GSI values, male sexual maturation in September was 10.0% vs. 14.4% for the TTA and the control group respectively. Thus, relative to the control group, the incidence of male sexual maturation in the TTA group was reduced by about 1/3 (P = 0.002). Production data was not affected by dietary supplementation of TTA. This study reveals that TTA significantly reduces the incidence of male sexual maturation in S0 Atlantic salmon. A significant elimination model of TTA in fish muscle that takes into account, the growth rate of the fish was further developed in this study.     

Improving production efficiency of farmed Atlantic salmon (Salmo salar L.) by isoenergetic diets with increased dietary protein‐to‐lipid ratio

The effects of isoenergetic diets with high (HP) and low (LP) protein‐to‐lipid ratios on feeding rate (SFR), feed conversion (FCR), growth (TGC) and relative‐ and absolute nutrient retention were investigated using both whole‐body weight (BW) and carcass weight (CW) to assess the production efficiency. Three different feeding trials in seawater were conducted: two large‐scale trials with yearling smolt (S1) and under‐yearling smolt (S0) and one small‐scale with S1 smolt. The initial body weights in the trials were 105, 319 and 978 g, respectively, and the fish were fed and monitored until they reached harvest weights. In all three trials, the dietary HP group attained significantly higher (p < .05) CW at harvest based on fish with equal BW. Also, fish fed the HP diets significantly improved FCR (p < .05) when based on CW. In the small‐scale trial, fish fed HP diet, especially during late autumn and spring, significantly (p < .001) improved FCR_BW and FCR_CW. Improved FCR coincided with significantly higher (p < .05) relative energy retention in the dietary HP group. In all three trials, the HP groups had significantly higher (p < .05) TGC with regard to both BW and CW. Taken together, the present studies indicate that growth performance and feed utilization in modern salmon farming has the potential to be further improved by increasing the dietary protein‐to‐lipid ratio. In addition, dietary influence is more precisely assessed when using carcass as the weight denominator when analysing feed utilization and growth performance.