Exogenous estradiol improves shell strength in laying hens at the end of the laying period

Background

Cracked shells, due to age related reduction of shell quality, are a costly problem for the industry. Parallel to reduced shell quality the skeleton becomes brittle resulting in bone fractures. Calcium, a main prerequisite for both eggshell and bone, is regulated by estrogen in a complex manner. The effects of estrogen, given in a low continuous dose, were studied regarding factors involved in age related changes in shell quality and bone strength of laying hens. A pellet containing 0.385 mg estradiol 3-benzoate (21-day-release) or placebo was inserted subcutaneously in 20 birds each of Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) at 70 weeks of age. Eggs were collected before and during the experiment for shell quality measurements. Blood samples for analysis of total calcium were taken three days after the insertion and at sacrifice (72 weeks). Right femur was used for bone strength measurements and tissue samples from duodenum and shell gland were processed for morphology, immunohistochemical localization of estrogen receptors (ERα, ERβ), plasma membrane calcium ATPase (PMCA) and histochemical localization of carbonic anhydrase (CA).

Results

Estrogen treatment increased shell thickness of both hybrids. In addition, shell weight and shell deformation improved in eggs from the brown hybrids. The more pronounced effect on eggs from the brown hybrid may be due to a change in sensitivity to estrogen, especially in surface epithelial cells of the shell gland, shown as an altered ratio between ERα and ERβ. A regulatory effect of estrogen on CA activity, but not PMCA, was seen in both duodenum and shell gland, and a possible connection to shell quality is discussed. Bone strength was unaffected by treatment, but femur was stronger in LSL birds suggesting that the hybrids differ in calcium allocation between shell and bone at the end of the laying period. Plasma calcium concentrations and egg production were unaffected.

Conclusions

A low continuous dose of estrogen improves shell strength but not bone strength in laying hens at the end of the laying period.     

Effects of adult stocking density on egg production and viability in cultures of the calanoid copepod Acartia tonsa (Dana)

The effect of stocking density of the calanoid copepod Acartia tonsa was evaluated in a 96 h rearing experiment. Possible density‐dependent egg production and egg viability were analysed at stocking densities of 100, 200, 300, 400 and 600 adults L⁻¹. Temperature, oxygen saturation and algal concentration were kept optimal. A non‐density‐dependent mortality rate of 15–19% day⁻¹ was documented. A non‐significant density‐dependent egg production was observed between 100 and 600 adults L⁻¹. The average egg production was 22.5±8.8 egg female⁻¹ day⁻¹ in all densities. The average egg hatching success was 84.7±4.8% and was never observed below 76.1%, with no significant differences across the stocking densities. Conclusively, as a practical recommendation for the aquaculture industry, copepod cultures with densities ranging from 100 to 600 adults L⁻¹ and presumably even more dense cultures are possible with the studied species obtaining a steady egg production and still high egg viability.     

The development of pyrethrum-based treatments against the ectoparasitic salmon lice Lepeophtheirus salmonis in sea cage rearing of atlantic salmon Salmo salar L.

Motile salmon lice Lepeophtheirus salmonis were successfully removed by an oil-based pyrethrum treatment mixture. The experiments described here are all based on skin exposure of the salmon Salmo salar L. The in-cage method, in which salmon would delouse themselves by jumping through a layer of treatment mixture, gave up to 86.9% delousing effect under low levels of solar radiation (October). However, at higher levels of radiation (May), the comparable effect decreased to 31.8%. Studies of exposure time vs. delousing effect showed no difference between 2-s and 10-s exposure and gave an overall delousing effect of 89.5%. Individual delousing procedures have thus been developed with a 4- to 6-s dip in the pyrethrum treatment mixture. A commercial method is described based on commercial Py-Sal 25 mixed with an anaesthetic bath before a vaccination or sorting operation. The overall delousing efficiency with this large-scale method was 85%. This is the method now used in commercial delousing with pyrethrum as the active component.     

Predation on native fish eggs by invasive round goby revealed by species‐specific gut content DNA analyses

1. Conservation of riverine fish often aims to improve access to spawning grounds and restore longitudinal connectivity by removing migration barriers, and involves substantial investments. However, these investments also enable non‐native predators to invade upstream into spawning areas and potentially adversely affect the recruitment of threatened freshwater fish through egg or fry predation.
2. Detecting egg predation is often challenging. Visual inspections of fish gut contents may underestimate predation of soft materials such as eggs and fry, which limits the discovery of predators preying upon these life‐stages. DNA‐based detection assays may offer a more sensitive tool to assess predation of soft materials.
3. A conservation issue was confirmed by developing and applying a species‐specific DNA‐based detection assay: invasive round goby (Neogobius melanostomus) prey on the eggs or fry of the threatened common nase (Chondrostoma nasus) in Switzerland.
4. DNA‐based detection assays were also developed for five other valuable native fish species, including endangered salmonid and cyprinid river spawners. The applicability of the assays was confirmed in a series of laboratory and field feeding experiments involving eggs and fish tissue. In addition, this work provides a guiding framework for conservation managers regarding the use and applicability of different DNA‐based detection approaches for gut content analysis.
5. The results of this study could inform local conservation measures – such as temporary reductions in the density of round goby at spawning sites prior to spawning – and demonstrate how targeted application of species‐specific molecular markers may advance freshwater fish management.

     

Accelerated extractions of North Atlantic cod and herring, 1520–1790

We propose the concept of Accelerated Marine Extraction to signify two periods when rapidly increasing cod (Gadus morhua, Gadidae) and herring (Clupea harengus, Clupeidae) fisheries, c.1540–1600 and c. 1730–1790, exceeded human demographic growth. Total landings vastly exceeded previous assessments and more than doubled between 1520 and 1620 from about 220,000 metric tonnes (t) to 460,000 t. Supplies of cod and herring to the European market peaked in 1788 at more than 1 million t before the unrest connected with the French Revolution brought many fisheries to a temporary halt. Accelerated Marine Extractions increased European food security at times of human demographic growth by almost doubling the supplies of fish protein per capita. While herring was the most important species by 1520, cod dominated through the period 1540–1790, and the trajectories of cod and herring extractions differed significantly. Cod landings increased almost ten-fold between 1520 and 1790, driven by strong and sustained landings in the Northwest Atlantic. Herring landings remained stable through the 16th century but declined severely through the next 150 years. However, from 1750, herring landings quadrupled, largely because of Swedish west coast fisheries. The results fundamentally shift our understanding of the scale of Atlantic fisheries in the past and underline the role of marine resources for European societies.     

Milk production and composition in Danish Holstein,Danish Red,and Danish Jersey cows supplemented with saturated or unsaturated fat

The aim of the experiment was to study the response in milk production and composition of substituting barley with either saturated or unsaturated fat in mixed rations (MR) for dairy cows. The experiment included 35 Danish Holstein (DH), 39 Danish Red (DR), and 31 Danish Jersey (DJ) cows from parturition until week 30 of lactation. Cows were ad libitum fed one of the three MR based on maize and grass/clover silage, barley, soybean meal, and dried sugar beet pulp. In the saturated ration (SFA), C16 rich fat substituted barley on dry matter (DM) basis; in the unsaturated ration (UFA), ground rape and linseed (0.74:0.26 ratio) substituted barley on DM basis; and in the control ration (CO), no barley was substituted. Concentrations of crude fat (CF) of total ration DM was 3.03% in CO, and in diets supplemented to intended similar fat levels 5.65% (SFA) and 5.81% (UFA), respectively. Statistical analyses were performed within breed and random regression was used to test for differences between treatment responses throughout lactations.     

Bisection of post-compaction bovine embryos: the difference in viability between the two monozygotic halves

Bisection of bovine post-compaction embryos has become a useful tool for improving embryo transfer results. Compared to pre-compaction division, the technique is simpler but is does involve some cellular damage and rarely provides two completely identical “halves”. Monozygotic pairs can therefore be divided into “good” and “poor” half embryos. By 4–6 h of culture in vitro, “good” halves remained significantly more viable than their poorer counterparts. Gytological evaluation after 24 h culture shows that the morphologically better halves contain more cells (an average of 45.9 vs 23.0) and have a higher mitotic index (6.1 % vs 3.1 %) than the poorer halves. The single transfer of 26 half-embryos resulted in 15 pregnancies (55.6 %) but no difference could be demonstrated between the results obtained with halves of different sizes. Nevertheless, the in vitro results support the contention that bigger halves give better results and also demonstrate that one half-embryo cannot be used as a control for the other in viability studies.     

Relationship between scintigraphic and radiographic evaluations of spinous processes in the thoracolumbar spine in riding horses without clinical signs of back problems

REASONS FOR PERFORMING STUDY: Radiography and scintigraphy are used to aid diagnosis of the cause of back pain, but a large variation in appearance and radiopharmaceutical uptake in fully functioning horses make diagnosis difficult. OBJECTIVES: To describe the range of and compare scintigraphic and radiographic findings in the spinous processes of horses without clinical signs of back problems. METHODS: Thirty-three apparently normal riding horses underwent scintigraphic and radiographic examinations of the spinous processes in the thoracolumbar spine. Scintigraphic images were evaluated in a continuous blue, green and red colour scale, and the level of radiopharmaceutical uptake in the spinous processes from T10-L2 was graded into none, mild, moderate or severe increased radiopharmaceutical uptake. Structural changes along the borders of the spinous processes and the width of the interspinous spaces from T10-L2 were recorded. RESULTS: Only 7 horses had no scintigraphic or radiographic findings. Nine horses had no increased radiopharmaceutical uptake, 17 had no sclerosis, 21 had no radiolucencies and 11 had normal spacing of the spinous processes (>4 mm wide). The majority of findings in 26 horses were located from T13-18 and were mild. CONCLUSIONS: The findings of a wide spectrum of scintigraphic and radiographic changes leads to the conclusion that changes within this range found in affected horses cannot be interpreted as clinically significant. POTENTIAL RELEVANCE: To determine whether scintigraphy and/or radiography can be used to separate horses with back pain from horses without clinical signs, the results from this study should be compared to the scintigraphic and radiographic findings in horses with clinical signs.