Feeding behaviour and growth of lumpfish (Cyclopterus lumpus L.) fed with feed blocks

The aim of this project was to investigate if lumpfish can be fed using specially designed feed blocks instead of regular fish feed pellets. Two studies were performed. In Part I different designs of feed blocks were introduced and fish observed with underwater cameras to record feeding behaviour. Results indicate that lumpfish require feed blocks with grooves in order to graze from them and that the acclimation period is relatively short (2–4 hr) before the fish will use them as a feed source. In the second part of the project two duplicate groups of lumpfish with an initial mean (±SD) weight of 125.4 ± 45.7 g were individually weighed and randomly distributed into six 3.5 m³ circular flow‐through tanks with 45 fish in each tank. Fish in three tanks were fed using feed blocks with grooves and fish in three tanks were fed using a regular commercially available lumpfish extruded feed. Both groups received a daily feeding rate of 2% body/weight. From day 14 onwards, fish fed with marine pelleted feed had a significantly higher mean weight compared to fish fed with feed blocks. Although not significant, the condition factor was higher in the feed block group during the study period. Results from this study show that lumpfish will readily graze from feed blocks if they are presented in a way that allows them to do. In addition, the acclimation period required before the fish will utilize them appears to be short thus potentially allowing for their use in commercial salmon cages.     

Cannabinoid receptors are widely expressed in goldfish: molecular cloning of a CB2-like receptor and evaluation of CB1 and CB2 mRNA expression profiles in different organs

Cannabinoids, the bioactive constituents of Cannabis sativa, and endocannabinoids, among which the most important are anandamide and 2-arachidonoylglycerol, control various biological processes by binding to specific G protein-coupled receptors, namely CB1 and CB2 cannabinoid receptors. While a vast amount of information on the mammalian endocannabinoid system does exist, few data have been reported on bony fish. In the goldfish, Carassius auratus, the CB1 receptor has been cloned and its distribution has been analyzed in the retina, brain and gonads, while CB2 had not yet been isolated. In the present paper, we cloned the goldfish CB2 receptor and show that it presents a quite high degree of amino acid identity with zebrafish Danio rerio CB2A and CB2B receptors, while the percentage of identity is lower with the puffer fish Fugu rubripes CB2, as also confirmed by the phylogenetic analysis. The sequence identity becomes much lower when comparing the goldfish and the mammalian CB2 sequences; as for other species, goldfish CB2 and CB1 amino acid sequences share moderate levels of identity. Western-blotting analysis shows the CB2 receptor as two major bands of about 53 and 40 kDa and other faint bands with apparent molecular masses around 70, 57 and 55 kDa. Since the distribution of a receptor could give information on its physiological role, we evaluated and compared CB1 and CB2 mRNA expression in different goldfish organs by means of qReal-Time PCR. Our results show that both CB1 and CB2 receptors are widely expressed in the goldfish, displaying some tissue specificities, thus opening the way for further functional studies on bony fish and other nonmammalian vertebrates.     

Manipulation of nitrogen digestion by sheep using defaunation and various nitrogen supplementation regimens

Five ruminally, duodenally, and ileally cannulated sheep (average BW 62 kg) were fed 65% roughage: 35% concentrate diets (CP = 15%) in a 5 x 5 Latin square design to study the applicability of using a combination of defaunation with N supplements (soybean meal [SBM], corn gluten meal [CGM], blood meal [BM], urea, and casein) with different extents of ruminal degradation to manipulate microbial protein synthesis and amount of ruminal escape protein. Diets were fed twice daily (1,759 g DM/d). Defaunation was accomplished with 30-ml doses of alkanate 3SL3 (active ingredient: sodium lauryl diethoxy sulfate)/sheep daily for 3 d with 2 d of fasting. Treatment 1 (control) involved feeding faunated sheep a diet in which the supplemental N (45% of total dietary N) was 67% SBM N and 33% urea N. Treatment 2 involved feeding defaunated sheep the same diet as the control. Treatments 3, 4, and 5 involved feeding defaunated sheep diets in which the supplemental N source was either 67% CGM-BM (1:1 N ratio) N:33% urea N, or 33% CGM-BM N:67% urea N or 33% CGM-BM N:33% urea N:33% casein N, respectively. Compared with the faunated control, defaunation decreased (P less than .05) ruminal ammonia concentration (19 vs 26 mg/dl) and increased (P less than .05) CP flow to the duodenum (253 vs 214 g/d) due to a trend for increases in both bacterial (BCP) and nonbacterial (NBCP) CP flows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of defaunation and various nitrogen supplementation regimens on microbial numbers and activity in the rumen of sheep

Five sheep (average BW 62 kg) were fed 65% roughage: 35% concentrate diets (CP = 15%) in a 5 x 5 Latin square design to study the effects of combinations of defaunation and N supplements (soybean meal [SBM], corn gluten meal [CGM], blood meal [BM], urea, and casein) differing in ruminal degradation on ruminal microbial numbers and activity. Diets were fed twice daily (DM intake 1,759 g/d). Defaunation was accomplished with doses of 30 ml of alkanate 3SL3.sheep-1.d-1 for 3 d with 2 d of fasting. Treatment 1 (control) involved feeding faunated sheep a diet in which the supplemental N was 67% SBM N and 33% urea N. Treatment 2 involved feeding defaunated sheep the same diet as the control. Treatments 3, 4, and 5 involved feeding defaunated sheep diets in which the supplemental N source was either 67% CGM-BM N (CGM and BM combined on a 1:1 N ratio): 33% urea N, or 33% CGM-BM N:67% urea N or 33% CGM-BM N:33% urea N:33% casein N, respectively. Compared with the faunated control, defaunation (Treatments 2, 3, 4, and 5) increased (P less than .05) total direct counts of ruminal bacteria (2.7 vs 1.3 x 10(11)/ml), fungal zoospores (2.8 vs 1.4 x 10(5)/ml), and ruminal microbial protease activity (1.4 vs 1.0 mg azocasein/[ml ruminal fluid.h]). Defaunation did not have a consistent effect on ruminal microbial deaminase activity. Compared with the control, defaunation resulted in lower (P less than .05) total perchloric acid-soluble amino N in ruminal fluid at 4 and 10 h after the morning feeding. Defaunation did not decrease (P greater than .05) total free amino acid concentrations in ruminal fluid, but it altered the profile of free amino acids. Although defaunation increased (P less than .05) ruminal bacterial numbers, no increases in total microbial CP or OM concentrations in ruminal contents were observed.     

Occurrence of cutaneous infections of Myxobolus episquamalis (Myxozoa: Myxobolidae) in sea mullet, Mugil cephalus L, in Australia

Objective To report the occurrence of Myxobolus episquamalis in sea mullet, Mugil cephalus L , caught in estuaries in eastern and western Australia.
Design A prospective study of commercial catches of mullet in the Clarence River of NSW and individual cases from other areas.
Results The organism caused pale, white to pink, raised lesions on the scales and fins of sea mullet. Occurrence of infection was highest in spring and in a marine (down-river) environment compared to a brackish environment. Up to 6% of fish were affected in commercial catches.
Conclusion The infection is widespread in Australian mullet, but rarely causes significant economic loss.