Evaluation of β-(1 → 3, 1 → 6)-glucans and High-M alginate used as immunostimulatory dietary supplement during first feeding and weaning of Atlantic cod (Gadus morhua L.)

Stimulation of the non-specific defence enhances the disease resistance and growth, and has good potentials as a measure for increased microbial control in juvenile production of marine fish and shellfish. So far, the most commonly used immunostimulants are β-(1 → 3, 1 → 6)-glucans, and in this study the stimulatory potential of a β-(1 → 3, 1 → 6)-glucan of marine origin, the storage polysaccharide from the marine diatom Chaetoceros mülleri, was examined. The glucan (chrysolaminaran) was extracted from cultures of C. mülleri, and used as a dietary supplement in two first feeding experiments with larvae of Atlantic cod Gadus morhua L. In one experiment the microalgal glucan was compared to the commercial yeast-glucan product MacroGard®, and in the other to an alginate with a high content of mannuronic acid (High-M alginate) isolated from Durvillaea antarctica. The stimulants were given via rotifers, and weaning to formulated feed was initiated at day 17 or 18 after hatching. The survival ± SEM at day 27 after hatching was 24.5 ± 2.0%, 14.8 ± 4.5% and 13.1 ± 1.4% for the groups fed C. mülleri-glucan, yeast glucan and for the control, respectively, in the first experiment. The group fed C. mülleri-glucan group had higher survival compared to the control (P < 0.05) group, whereas the yeast glucan had no positive effect on the survival (p > 0.05). The dry weights of the groups at day 27 were low, with 203.2 ± 52.2, 165.2 ± 43.4 and 198.5 ± 58.1 μg per larva for the C. mülleri-glucan, yeast glucan and control groups, respectively. In the second experiment the survival in the period of feeding formulated feed (days 18-30) were 44.6 ± 4.3%, 44.7 ± 1.3%, and 33.8 ± 4.1% survival for the C. mülleri-glucan, High-M alginate and control group, respectively. The cod larvae fed C. mülleri-glucan reached an average weight of 531.6 ± 17.2 μg at day 30, which was significantly higher (p < 0.05) than the control group that had an average of 473.6 ± 3.5 μg. The larvae fed High-M alginate had an average weight of 470.3 ± 31.6 μg per larva at day 30, and not significantly different from the control (p > 0.05). The early weaning to formulated diet had detrimental effect on the growth of the larvae. In both experiments the C. mülleri-glucan group was the only group showing a positive growth rate in the period of weaning to dry feed. The microbial conditions in larval gut and water were monitored with respect to total colony forming units on Marine agar, and Vibrio- and Pseudomonas-like species on selective agars (TCBS and marine Pseudomonas Agar with CFC-supplement). The larvae were rapidly colonised after hatching, but no or weak effects of the stimulants were observed on the colonisation rates or the composition. The total CFU varied from 10¹ to 10² CFU per μg larva after initiation of the first feeding. The percentages of Pseudomonas-like bacteria increased throughout the period, whereas the levels of Vibrio-like bacteria were low and stable. The chrysolaminaran from the diatom C. mülleri was shown to be a promising candidate for use as an immunostimulatory feed additive, and which should be further explored.     

Osteochondrosis and arthrosis in pigs. 3. A comparison of the incidence in young animals of the Norwegian Landrace and Yorkshire breeds

An investigation concerning the occurrence of osteochondrosis and arthrosis in 2 materials totalling 63 pigs of the Landrace breed and 63 of the Yorkshire breed is described. The animals were bred under the same conditions of feeding and housing. The differences should therefore mainly be of genetic origin. Both breeds were highly improved, Landrace the most. In general, Yorkshire pigs showed a lower incidence and a less marked degree of osteochondrosis and arthrosis than Landrace pigs. Statistically significant differences (P < 0.01) were demonstrated in the distal epiphyseal plate of the ulna, in the intervertebral joints of the lumbar region and in the medial condyle of the femur in 1 of the materials. The Landrace pigs had longer bodies, broader hindquarters, shorter femurs, and the stifle had a different shape as compared with Yorkshire pigs. There thus seemed to be a connection between exterior features, joint and bone shape and the occurrence of joint lesions. Differences among litters within breed were also demonstrated.     

<Emphasis Type="Italic">Colletotrichum acutatum</Emphasis> occurs asymptomatically on sweet cherry leaves

Leaves of sweet cherry, exposed to either paraquat or freezing to quickly senesce the leaf tissue, were incubated in about 100% RH at 25°C for 6 d. Sporulating colonies of Colletotrichum acutatum, the cause of anthracnose, developed on up to 100% of the paraquat-treated and frozen leaves, and on none of the untreated controls. Number of leaves and leaf area containing C. acutatum on naturally infected leaves increased over time from May to September. Mean incidence of C. acutatum on leaf blades on fruit spurs and vegetative shoots from eight orchard/year samplings were 41 and 33%, respectively. Secondary conidiation (formation of short hyphae and new conidia) from conidia applied to detached leaves took place 6 h after inoculation, but only up to 3% of the conidia formed new conidia. It may be concluded that asymptomatic sweet cherry leaves frequently host C. acutatum and may be a potential inoculum source for cherry fruit.     

Non-abscised aborted sweet cherry fruits are vulnerable to fruit decaying fungi and may be sources of infection for healthy fruits

During three growing seasons (1999–2001), disease incidence of non-abscised aborted and normally developing (sound) sweet cherry fruits were investigated in a research orchard at Ullensvang, western Norway. To reveal possible fungal infections, aborted and sound fruits of two cultivars (cv. Van for three years and cv. Lapins for two years) were harvested over four to seven weeks in an experimental orchard during the green fruit phase and incubated at 20°C in moisture saturated air for 7 days. The most frequently observed fungal pathogens were Monilinia laxa, Colletotrichum gloeosporioides, and Botrytis cinerea. The mean of all observations (±standard deviation) over three years, showed that aborted and sound fruits had a disease incidence of 51.9% (±31.8) and 5.2% (±9.7), respectively, after seven days incubation. In 24 of 25 trials aborted fruits had significantly higher disease incidence than sound fruits after incubation. In one season, when fruits were collected from two commercial orchards, aborted fruits had much higher disease incidence than sound fruits (a mean of 6.5 and 4.5 times higher incidence for the two orchards, respectively). Time of fruit abortion varied with the years (two years observation) and the two cultivars, but the major abortion took place between the fourth and eighth week after anthesis. A higher disease incidence and more rapid disease development in non-abscised aborted fruits indicate that they are more vulnerable to fungal colonisation than sound fruits and may thus be potential incoulum sources for neighbouring, healthy fruits.     

Leg weakness in pigs. II. Litter differences in leg weakness, skeletal lesions, joint shape and exterior conformation

Investigations were carried out concerning possible litter differences in locomotory ability and exterior conformation, and possible litter and sire group differences in the occurrence of skeletal lesions and in joint shape. The animals were from a breed experiment involving 6 litters, 8 feeding experiments involving 64 litters, and a selection experiment totalling 70 litters and 25 sire groups distributed in 3 lines. One hundred and twenty-one out of 285 P values for litter or sire group differences were statistically significant (P < 0.05). This shows, with reservations concerning the possibility that different environmental conditions up to 20 kg live weight may have produced a litter effect on pigs from the breed and feeding experiments, that heredity plays a significant part in the leg weakness complex. It seems justified to conclude that it partly is the inheritance of certain joint shapes and exterior conformational features, which influence the degree of joint lesions and locomotory ability and give rise to litter differences. This gives the theoretical possibility of selecting for more lasting joints and better locomotory ability using criteria based on joint shape and exterior conformation.     

A NEW TYPE OF RADIOGRAPHIC BONE REMODELING IN THE DISTAL RADIAL AND ULNAR METAPHYSIS IN 54 NEWFOUNDLAND DOGS

In this longitudinal observational study, 118 growing Newfoundland dogs were followed with sequential radiographic examination of the right front limb, which were scheduled at ages 3, 4, 6, 12, 18, and 24 months to record evidence of skeletal changes. All affected dogs had evidence of changes at 6 months and dogs included in this study had radiographic examination at 6 months and at least two other scheduled examinations that included either 4 or 12 months. The dogs were privately owned and had individualized nutrition and environment with no maintenance protocol required by the project leaders. Irregularities in bone remodeling in the distal radius and ulna were seen in radiographs of 54 of 118 (45.8%) dogs. These irregularities differ from changes previously described in the Newfoundland dog. The reported irregularities were seen as islands of reduced opacity outlined by thickened, radiopaque osseous trabeculae, which were aligned with the axis of stress. All the 54 dogs with irregularities during some phase of development consistently had changes at 6 months of age. Reorganization of the changes in the bone was slow, and residual changes were visible at 18-24 months of age in many cases. The significance of these findings may lie in their potential for misinterpretation if they had been discovered in the presence of clinical signs such as any lameness or growth arrest. Radiographic appearance indicates disturbances in the bone maturation. The etiopathogenesis is unclear. Nutritional, environmental and genetic factors have to be studied.     

Osteochondrosis and arthrosis in pigs. V. A comparison of the incidence in three different lines of the Norwegian Landrace breed

Investigations were carried out on 289 slaughter pigs, 56 breeding boars, and 51 breeding sows in a selection experiment started in 1964. The animals belonged to 4th–6th generations. One line has been selected for thin backfat and rapid growth (LBL) and 1 for thick backfat and slow growth (HBL). In addition a control line (GL) not subjected to selection was established in 1967. The pigs were kept as far as possible under identical conditions of housing and feeding, so that differences between lines should be primarily of genetic nature. The skeleton, measured as the length of bones and vertebral column, was statistically significantly smaller (P < 0.01) in HBL than in CL and LBL. The difference between CL and LBL was slight. No essential proportional changes in the skeleton took place. Patho-anatomical findings in the skeleton comprised, in all 3 lines, osteochondrosis, arthrosis, degeneration of the intervertebral discs, spondylosis, and epiphyseal separation. There were a lower incidence and statistically significant (P < 0.01) lower degree of total lesions in joints and bones in HBL, both as regards the slaughter pigs, boars and sows. The fact that the lumbar region of the vertebral column consistently showed the greatest difference in degree and incidence of lesions between the lines, suggests that this becomes the weakest skeletal part in pigs with a rapidly growing skeleton.     

Osteochondrosis and arthrosis in pigs. II. Incidence in breeding animals

Joint and bone lesions in Norwegian breeding pigs are described on the background of an investigation involving 174 sows and 155 boars from 7 months to 4½ years old. Lesions, which consisted predominantly of arthrosis, degeneration of intervertebral discs, spondylosis and epiphyseal separations, were demonstrated frequently in both sexes. Osteochondrosis, a condition previously demonstrated frequently in slaughter pigs, had either completely healed, undergone repair or developed into an arthrosis by the time the animal reached an age of about 1½ years.Whereas a higher incidence of arthrosis of the intervertebral joints was found in boars than in sows, the reverse was true as regards degeneration of the intervertebral discs and anchylosing spondylosis. Possible reasons for this are discussed. Norwegian pigs show a higher incidence of lesions in the lumbar region of the vertebral column than has been described up to the present time in other countries.     

Inter‐individual variation in the dominant intestinal microbiota of reared Atlantic cod (Gadus morhua L.) larvae

The diversity of the microbiota in 15 Atlantic cod (Gadus morhua L.) larvae from three different hatcheries with variable food type and water treatment was characterized with culture dependent and independent approaches. The culture‐dependent approach was phenotypic characterization of bacterial isolates based on 16 tests, and the culture‐independent approach was terminal restriction fragment length polymorphism (T‐RFLP) of PCR amplified 16S rRNA. Both approaches revealed large inter‐individual differences in the microbiota of cod larvae. Data from real time PCR indicate substantially lower variation in bacterial number larva^?1 both within and between hatcheries than the data on colony forming units, resulting in an estimated four orders of magnitude variation in culturability between larvae. Considerably higher richness and diversity were observed with T‐RFLP than with phenotypic characterization, and no correlation between the two approaches was found for diversity indexes calculated at the individual level. Dissimilarity in the composition of the microbiota between individuals from the same rearing environment was comparable to the dissimilarities between hatcheries. The large inter‐individual variation is important to consider when designing experiments, as pooling of individuals will completely mask this variability. We conclude that colonization of individual cod larvae by bacteria seems to be a stochastic and not a deterministic process, which is not well understood.