Differences in swimbladder volume between Baltic and Norwegian spring-spawning herring: Consequences for mean target strength

Fish swimbladders, where present, contribute most to the scattering of sound by fish, as measured by the target strength (TS). The volumes of the swimbladders of two different European stocks of Atlantic herring were compared to consider the effect on estimates of TS. Swimbladder volumes of Baltic and Norwegian spring-spawning herring (Clupea harengus) were measured, together with individual herring fat content. Swimbladder volumes were found to differ significantly between the two herring stocks. Baltic herring have a larger swimbladder volume, which is suggested to be associated with the fish's low fat content, which in turn may be linked to its specific energy budget and the low salinity of the Baltic Sea. A buoyancy model that considered the different salinity conditions and fat proportions was used to evaluate the observed differences in swimbladder volume. The swimbladder volume data were subsequently used to model the mean target strength as a function of depth and growth pattern. Backscattering of the swimbladder was modelled using the modal-series-based deformed-cylinder model (MSB-DCM), describing the swimbladder as a gas-filled, elongated prolate spheroid. The fish body component was modelled as a fluid-filled ellipsoid using the distorted wave Born approximation (DWBA). Modelling results support a different TS-to-size relationship for Baltic herring, with a stronger echo, due to the larger swimbladder. Depth- and length-dependent TS relationships based on the model results are suggested.     

Investigation of relationships between cell and pulp properties in Eucalyptus by examination of within-tree property variations

 Relationships between cell and pulp properties were investigated by examining the within-tree property variations in Eucalyptus camaldulensis and Eucalyptus globulus. Properties investigated included proportions of ray and axial parenchyma, thickness of cell walls and cell wall percentages. The characteristics of the ray and axial parenchyma (their proportions and wall thickness) were found to have a significant influence on all measured pulp properties, including paper strength properties. Multiple regression of pulp properties in relation to cell properties revealed that nearly all measured pulp properties were explained by cell properties at the 1% significance level. It was concluded, therefore, that all cell types are important for predicting pulp properties, and it is strongly recommended that tree breeding programs for Eucalyptus include the measurement of all cell types. Received 6 July 1999     

Multiple-locus variant-repeat assay (MLVA) is a useful tool for molecular epidemiologic analysis of Streptococcus agalactiae strains causing bovine mastitis

Group B streptococci (GBS) were considered a major cause of mastitis in cattle until preventive measures succeeded in controlling the disease in the 1970s and 1980s. During the last 5-6 years an increasing number of cases have been observed in some Scandinavian countries. A total of 187 GBS isolates from mastitis cases were collected from 119 animals in 34 Norwegian farms in the period from April 2007 to November 2010. 133 (71%) of the isolates were from farms with automated milking systems. The strains underwent typing of capsular polysaccharides (CPS) and surface proteins, and were analyzed by multi-locus variable repeat assay (MLVA) to investigate the epidemiological relationship of strains within and between farms. The GBS strains were differentiated into 12 types by CPS and surface protein analysis, with CPS types V (54%) and IV (34%) predominating. MLVA was superior to CPS and protein typing for strain differentiation, resolving the 187 strains into 37 types. In 29 of 34 farms all GBS strains had identical MLVA profiles specific for each farm. However, in one farm represented with 48 isolates, four MLVA variants with differences in one repeat locus were observed during the almost 3-year long collection period. Similar variations were observed at four other farms. This might reflect the stability of repeat loci under in vivo conditions. Farms with automated milking systems were overrepresented in this material. In conclusion, the five-loci MLVA allowed rapid high-resolution genotyping of the bovine GBS strains within and between farms.     

Evaluation of Ewe Performance in 795 Selected Sheep Flocks in South-Eastern Norway

A study of ewe performance was undertaken in 795 sheep flocks based on data from the Norwegian Sheep Recording System. Herd level data included in the annual report for 1998 were used as the basis for the study. Average flock size was 75.3 ewes. The material was considered as representative of the better and more motivated sheep farmers in the mountain valley regions in south-eastern Norway. The average number of lambs born per ewe, inclusive (and exclusive) of barren ewes, was 1.89 (2.02), and of autumn lambs (those surviving from birth in the spring to autumn) 1.60 (1.66). The average autumn weight of the lambs corrected to 145 days of age was 42.4 kg, giving an overall performance of 67.9 kg lambs live weight per ewe. When including artificially reared lambs, overall performance was 70.4 kg per ewe. Artificial rearing of lambs, mostly triplets which had been removed from the ewe, was practised on 395 of the farms. In the 74 flocks with a rate of artificial rearing of more than 10% of all lambs, overall performance per ewe was 13.3 kg higher than in flocks with no artificial rearing. Total lamb mortality from birth to autumn recording, including stillborn lambs, was 12.44%. Mortality had a skewed distribution, some flocks having very high mortality figures. The arithmetic means (and medians) for mortality were as follows: 2.75 (2.29)% stillbirths, 2.93 (2.30)% died during the indoor feeding period, 0.88 (0.00)% at spring pasture, and 6.16 (4.40)% at summer pasture. In regression models using Proc Genmod in SAS^®, it was found that average number of autumn lambs per ewe was negatively associated with the rate of barren ewes, late lambing date (flock average day in year when lambing took place), and total lamb mortality. The corrected autumn weight of the lambs was positively associated with the average number of lambs born per ewe and non-fertility rate, and negatively associated with flock size and total lamb mortality. The Dala breed had a positive effect on number of autumn lambs per ewe, and Spæl breed a negative effect on corrected autumn live weight of the lambs.     

Photosynthetic responses of spring barley varieties to different stand densities under field conditions

Abstract

Photosynthesis is affected by many factors on which plant productivity depends; however, little is known about the variation of spring barley photosynthetic characteristics under the influence of different stand densities. A 2-year field study was conducted to determine the photosynthetic rate (A), efficiency of excitation capture by open PSII reaction centres (F'v/F'm) and chlorophyll index (SPAD) response of various spring barley varieties to different stand densities (SDs) under field conditions. Three seed rates were used (200, 400 and 600 plants m^?2) and three varieties (Aura DS, Barke and Gustav). The measurements were made three times during the growing season. Varietal effect was significant on all indicators, the influence of the factors' interaction was significant on A, but SD influence was not significant. Varieties differed in tolerance to weather conditions. Maximum A was established for Gustav in wet year, but for Barke in dry year. The highest F'v/F'm was observed for Gustav under dry and warm conditions. The lowest F'v/F'm across varieties was for the lowest SD. The highest SPAD was observed for Gustav, the lowest for Aura DS. SPAD increased with decreasing SD. The correlation between the indicators and grain yield was positive. Meteorological conditions influenced the A data variation by 46.4–82.5%, 60.9–87.8% and 61.9–83.9% for the Aura DS, Barke and Gustav, respectively. Our research showed that under Central Lithuania's weather conditions the most effective photosynthetic process was recorded in the intensive variety Gustav, which is recommended to be grown at a medium crop density of 400 plants m^?2.     

Electronic feed stations for feeding concentrates to pregnant ewes on commercial sheep farms

ABSTRACT

The aim of this study was to investigate the use and capacity of electronic feed stations (EFS) on commercial sheep farms. The study was conducted on four commercial farms and the numbers of pregnant ewes per EFS were 36, 70, 72 and 80, respectively. Each farm was visited once and behavioural observations were carried out. In addition the date and time for both entering and leaving the EFS and the amount of concentrates dispensed at each visit for extracted. The vast majority of the ewes used the EFS regularly. The number of rewarded visits per ewe per day varied from 3.2 to 5.9, whereas the number of unrewarded visits ranged from 6.0 to 21.5 per ewe per day. We conclude that feeding concentrates to groups of pregnant ewes in EFS function satisfactory, but the design of the entrance and exit gate still have to be improved considerably.     

Heart splitting at crosscutting of eucalypt logs

The occurrence of heart splitting during the crosscutting of logs was discussed in relation to the released strain on Eucalyptus spp. logs. The strains released in the longitudinal and tangential directions were measured by the strain-gauge method and were correlated with the length of the heart split measured on the same logs. There were differences in the longitudinal strain; however, no significant correlation was found with the diameter that could be converted to a mean annual increment (i.e., a relation with the growth rate). The initial splits expand with the time after felling. The longer the initial split, the longer is the length 1 week after felling. The split length was significantly smaller at the butt end of the first log of every tree than at the other end, but there were no significant differences between the split length at the top of the first logs and at either end of the second logs, although there were differences among individual trees. The length of the heart split correlated with the released strain near the pith, which was estimated using Kublers equation. The longitudinal released strain measured on the surface of logs is a good indicator of the heart splitting when crosscutting logs.Part of this paper was presented at the 52nd Annual Meeting of the Japan Wood Research Society