Antinociceptive effects of intrathecal 5-HT agonists in sheep

Objectives To examine the role of spinal 5‐hydroxytryptamine (5‐HT) binding sites in nociceptive processing in conscious sheep and to study the role of 5‐HT agonists in mediating analgesia. Study design Prospective controlled study. Animals Nine adult healthy female sheep (Swaledale, Swaledale‐cross or Clun Forest) weighing 45–65 kg. Methods Intrathecal (IT) catheters were implanted at the cervical (n = 5) or lumbar (n = 4) level of the spinal cord under general anaesthesia. At least 1 week later, and at 1 week intervals thereafter, the effects of intrathecal Ringer's solution (control), xylazine (100 µg), 5‐HT creatinine sulphate (200, 400 and 800 µg), RU24969 (200 µg), α‐Methyl‐5‐HT and 1‐(3‐Chlorophenyl)‐biguanide (CPBG) on the mechanical nociceptive threshold (MT) were studied. Results were plotted as mean variable versus time curves. Areas under portions of the curves (0–30 and 0–60 minutes) were measured and expressed as mean ± standard error. Differences between values for control and drug trials were examined using the two‐tailed Student's t‐test. Results Baseline values of MT were lower on the hind limbs than on the forelimbs. Intrathecal Ringer's solution did not alter MT in the cervical or lumbar region. Xylazine (100 µg) produced a characteristic elevation in MT between 5 and 60 + minutes. Lumbar IT injection of 5‐HT (800 µg) raised the MT more than cervical injection, while cervical injection of RU24969 (200 µg) raised the MT more than lumbar administration. Cervical IT injection of α‐Me‐5‐HT (500 µg) produced a marked and significant increase in MT while lumbar application had no effect. CPBG (500 µg) injection caused no significant effect on MT with either cervical or lumbar applications. Conclusions The activation of 5‐HT₁ and 5‐HT₂ receptors particularly at the cervical level appears to be involved in spinal nociceptive processing in the sheep. Clinical relevance These effects, which lasted about 60 minutes, may have an implication in the development of new analgesic strategies for animals.     

Effect of preslaughter feed withdrawal period on longissimus tenderness and the expression of calpains in the ovine

The objective was to study the role of calpains in meat tenderness. Lambs were fasted for various periods of time to generate differences in meat tenderness and to determine in tandem the expression of calpain 1, calpain 2, calpain 3, and calpastatin. The assumption has been that increased calpain expression associated with an increase in tenderness indicates a role for calpain in the tenderization process and vice versa. Fasting lambs for 1 day caused a significant improvement in longissimus (LD) tenderness compared to the control. Correlations between the tenderness of the LD and the expression of the calpains and calpastatin were significant for calpains 1 and 3 but not for calpain 2 or calpastatin. Consequently, this study supports a role for calpains 1 and 3, but not for calpain 2, in the tenderization of the LD from fasted lambs during post-mortem aging.     

HARVESTING TETRAPLOID RYEGRASS FOR SEED

Sequential harvests of two tetraploid ryegrasses have shown that the commercially critical level of 90% germination was attained early in the ripening process. For the greater part of the maturation period the moisture level was maintained at 60% as in diploid grasses, but the rate of moisture loss during the latter part of ripening proved to be slower than in diploids. The large seeds are more susceptible to mecbanical damage at harvest and therefore require lower drum speed.     

The aetiology of spinal deformity in Atlantic salmon, Salmo salar L.: influence of different commercial diets on the incidence and severity of the preclinical condition in salmon parr under two contrasting husbandry regimes

A large-scale trial of the effect of different commercial diets on the incidence of preclinical spinal deformation, as assessed by radiography, and the influence of two contrasting rearing systems was carried out. Two sets of three populations of Atlantic salmon, each of 20 000 first feeding fry of identical hatchery origin, created from equal numbers of eggs from 15 different families, were reared under commercial conditions on two different farms. Three commercial (closed formula) extruded fish meal-based diets were used in this study (diets A, B & C). Each diet was fed to one population of 20 000 fish at each site. Fish were fed a percentage of their body weight per day, with feeding rates set at commercial levels, based on water temperature, day length and fish biomass. Additional hand feeding was used to ensure satiation in all tanks. Fish in each tank were bulk-weighed and counted at the beginning and at 2-week intervals throughout the study. The fish were grown for 30 weeks. In addition, phosphorus (P) digestibility was evaluated by in-feed absorption testing in rainbow trout. The morphology of the radiographic lesions conformed to those described previously. Statistical analysis using multivariate regression analysis showed that date of sampling, site and diet were all statistically significant (P < 0.001) on univariable analysis. Farm A had significantly more affected fish than farm B (P < 0.001), which may have been attributable to variation in dissolved oxygen levels. The available dietary P levels were low in each diet. The number of fish affected in the group of fish being fed diet B was significantly lower than in the groups being fed diets A or C (P < 0.001). It appears most likely that the occurrence of preclinical radiographically apparent defects in parr which are believed to lead to the condition known as 'spinal deformity' is predominantly caused by a deficiency of available dietary P in first-feeding fry. The availability of dietary P may also vary considerably between diets formulated using different ingredients. Phytate-P associated with plant ingredients may affect the availability of P as well as other essential dietary nutrients. Additionally, diets for the production of salmonids in fresh water are currently formulated to keep P effluent to a minimum compatible with healthy spinal development. These various factors combine to make it crucial that small Atlantic salmon, especially first-feeding fry, are provided with carefully formulated diets fortified to an adequate level with a high quality source of available P.     

Modelling transport of inshore and deep‐spawned chokka squid (Loligo reynaudi) paralarvae off South Africa: the potential contribution of deep spawning to recruitment

The South African chokka squid, Loligo reynaudi, spawns both inshore (≤70 m) and on the mid‐shelf (71–130 m) of the Eastern Agulhas Bank. The fate of these deep‐spawned hatchlings and their potential contribution to recruitment is as yet unknown. Lagrangian ROMS‐IBM (Regional Ocean Modelling System‐Individual‐Based Model) simulations confirm westward transport of inshore and deep‐spawned hatchlings, but also indicate that the potential exists for paralarvae hatched on the Eastern Agulhas Bank deep spawning grounds to be removed from the shelf ecosystem. Using a ROMS‐IBM, this study determined the transport and recruitment success of deep‐spawned hatchlings relative to inshore‐hatched paralarvae. A total of 12 release sites were incorporated into the model, six inshore and six deep‐spawning sites. Paralarval survival was estimated based on timely transport to nursery grounds, adequate retention within the nursery grounds and retention on the Agulhas Bank shelf (<200 m). Paralarval transport and survival were dependent on both spawning location and time of hatching. Results suggest the importance of the south coast as a nursery area for inshore‐hatched paralarvae, and similarly the cold ridge nursery grounds for deep‐hatched paralarvae. Possible relationships between periods of highest recruitment success and spawning peaks were identified for both spawning habitats. Based on the likely autumn increase in deep spawning off the Tsitsikamma coast, and the beneficial currents during this period (as indicated by the model results) it can be concluded that deep spawning may at times contribute significantly to recruitment.     

Laboratory trials on the effects of different diets on growth and survival of the common whelk, Buccinum undatum L. 1758, as a candidate species for aquaculture

Newly hatched juvenile Buccinum undatum can be reared under laboratory conditions. Good was growth is achieved when juveniles were fed on combined diets (blue mussel, cod, and fish pellets). Juveniles reached shell heights of 33.0 ± 4.2 mm, 26.9 ± 3.8 ± mm, 23.2 ± 2.2 mm, and 20.1 ± 1.6 mm, after 14 months of fedding on a combined diet, blue mussel, cod, and fish pellets, respectively under ambient sea temperature and salinity. After 14 months juveniles fed blue mussel had the highest survival rates (67%) followed by those fed a combination of all other experimental diets (61%), cod waste (53%) and fish-feed pellets (46%). High mortalities were recorded in most treatments during the summer months between June and September. This species appears to have an aquaculture potential, as juveniles readily feed on artificial diets at an early age, show high survival rates and could potentially reach market size in 2 years or less. The major constraint in realising this potential at present, is the relatively low value of the species; if market values increased as a result of serious depletion of natural populations, hatchery production of juveniles for intensive aquaculture or restocking could become economically viable.