Experimental infections of mice and pigs with Streptococcus suis type 2.

Five inbred strains of mice were tested for their susceptibility to Streptococcus suis type 2 including the type strain, two isolates from meningitis in pigs and two isolates from tonsils of clinically healthy pigs. C57BL/6, ICR and ddY strain mice showed lower susceptibility to all strains of S. suis type 2 than BALB/c and SS strain mice. The type strain and the isolates from diseased pigs produced septicaemia and meningitis in BALB/c and SS mice inoculated with 10(8) colony forming unit of the bacteria and 60 to 100% of these infected mice died. On the other hand, mice inoculated with the isolates from healthy pigs showed mild clinical signs but none of them died. In BALB/c mice which died or developed nervous signs, the purulent meningo-encephalitis, myocarditis, ophthalmitis, labyrinthitis and otitis media were observed. S. suis type 2 antigen was demonstrated in these lesions by immunoperoxidase staining using rabbit S. suis type 2 antiserum. These results were similar to those in the experimentally infected pigs with these virulent and avirulent strains against mice. These results indicate that BALB/c and SS strains of mice are useful as an experimental model of S. suis type 2 infections in pigs, and that there are virulent and avirulent strains against mice and pigs among the strains of S. suis type 2.     

Interannual variability in stock abundance of the neon flying squid, Ommastrephes bartramii, in the North Pacific Ocean during 1979–1998: impact of driftnet fishing and oceanographic conditions

Variability in catch-per-unit-effort (CPUE) was examined for the autumn cohort of Ommastrephes bartramii collected with research driftnets during 1979–1998 along five longitudinal transects passing through the Subarctic, Transitional and Subtropical Domains in the North Pacific. CPUE was generally low during the period of intensive commercial driftnet fishing (1980–1992) and increased following the 1992 moratorium on the use of large-scale driftnets. However, CPUE levels were low for the cohorts hatched in 1992 and 1996 (captured in subsequent years owing to a one-year life of O. bartramii ) that experienced low sea surface temperatures from hatching to recruitment. Among similar-aged squid collected from 180° and 179°30'W in June, mantle lengths were significantly greater in 1997 than during 1995–96. These findings suggest that the driftnet fishery and sea surface temperatures from hatching to recruitment strongly affected stock abundance and possibly growth.     

Addition of oxytocin to semen extender improves both sperm transport to the oviduct and conception rates in pigs following AI

Oxytocin (OXT) contained in boar semen is known to produce uterine contraction; therefore, we hypothesized that the co‐injection of OXT with sperm would improve artificial insemination (AI) using liquid or frozen‐thawed boar sperm. We initially examined whether OXT added to semen extender improved sperm transport to the oviduct. Although the addition of OXT did not affect the fresh or frozen‐thawed sperm motility or acrosomal integrity, it significantly increased the number of sperm in the oviduct at 6 h after AI injection with OXT, as compared with the control (P < 0.05). Moreover, some sperm were observed in the sperm reservoir of the isthmus in the OXT treatment group, whereas few sperm were observed in the control. When OXT was added to the semen extender immediately prior to AI, the conception rates were significantly higher in both fresh semen and frozen‐thawed semen than in the control group (P < 0.05: liquid, 87.5% vs. 70.5%; frozen‐thawed, 89.8% vs. 75.0%). From these results, we concluded that the addition of OXT to the semen extender assisted in sperm transportation from the uterus to the oviduct, which resulted in improved reproductive performance.     

Maximum prey size estimation of longtooth grouper,Epinephelus bruneus,using morphological features,and predation experiments on juvenile cannibalism

In fish culture, cannibalism, which induces critical damage, is separated into two types: type I, which occurs in early larval stages when size heterogeneity is low; and type II, which starts in later larval and/or early juvenile stages following type I when size heterogeneity is high. In type II, the cannibal's maximum prey size is limited by its gape size relative to the prey fish body size. Ratios of prey to cannibal body size changes are associated with allometric factors and feeding behaviour with growth. In a previous study on grouper, the maximal prey size was estimated morphologically (i.e., the relationship between gape size and body height). This method is very simple and useful; however, it does not consider allometric factors and feeding behaviour changes; therefore, it probably causes a large estimation error. To overcome this, we present a new method for estimating maximal prey size to determine the size ranges for size grading of longtooth grouper, Epinephelus bruneus, juveniles using predation experiments. It is shown that grouper type II cannibalism is affected by two factors; in early juvenile stages by morphology and in later (TL over 50 mm) by prey size selectivity.     

Diurnal changes in plasma melatonin and the timing of reproductive onset in anestrous sheep fed melatonin.

Seasonally anestrous Suffolk ewes (n = 28) were randomly divided into 5 groups and treated with varying doses of melatonin as follows; Groups C (n = 4), M1 (n = 6), M2 (n = 6), M3 (n = 6), M4 (n = 6) of ewes were fed pellets containing 0, 1, 2, 3 and 4 mg melatonin, respectively, daily for 60 days from May 17 (Day 0). Following feeding of the pellets at 13.00 hr plasma levels of melatonin rapidly increased reaching the peak values within 30 min, which ranged from 92.0 to 292.7 pg/ml and were highly correlated with the dose of melatonin administered (r = 0.986, P less than 0.01). Maximum dose of melatonin (4 mg) produced an increase of plasma melatonin similar in magnitude to nocturnal peaks of endogenous secretion. The onset of ovulatory cyclicity, assessed from plasma progesterone profiles, was advanced by melatonin administration. The mean +/- SEM intervals from the commencement of melatonin treatment until the onset of ovulatory cyclicity were 53.0 +/- 5.8, 53.6 +/- 2.5, 42.0 +/- 5.6 and 44.3 +/- 4.3 days for the Groups M1, M2, M3 and M4, respectively, which were shorter (M1, P less than 0.05; M2, M3 & M4, P less than 0.01) than that for the Group C (72.5 +/- 1.4 days). The melatonin treatment also suppressed, in a dose related manner, the rise in plasma prolactin under the lengthening photoperiod. We conclude that the dose-related efficacy of melatonin could be ascribed to the difference in the diurnal profiles of circulating melatonin.     

Reference Values on Serum Biochemical Parameters of Brazilian Donkey (Equus asinus) Breed

Seventeen serum biochemical variables were determined in 40 donkeys of the Brazilian breed (34 females and 6 males) aged from 3 to 19 years. Mean ± standard deviation (SD) (minimum–maximum) values, obtained by automated analysis, were as follows: glucose, 58.35 ± 10.40 (44.00–90.00) mg/dL; cholesterol, 88.41 ± 9.86 (73.58–124.26) mg/dL; serum protein, 6.82 ± 0.40 (6.00–7.52) g/dL; albumin, 3.13 ± 0.21 (2.65–3.69) g/dL; creatinine, 1.80 ± 0.14 (1.51–2.19) mg/dL; urea, 24.25 ± 5.37 (14.12–34.39) mg/dL; lactate, 20.10 ± 4.58 (12.99–33.47) mg/dL; aspartate aminotransferase (AST), 295.81 ± 62.79 (173.71–466.07) IU/L; creatine kinase (CK), 158.00 ± 76.94 (51.69–440.33) IU/L; γ-glutamil-transferase (GGT), 45.82 ± 13.34 (26.17–86.38) IU/L; lactate dehydrogenase (LDH), 576.02 ± 156.32 (213.53–1162.81) IU/L; alkaline phosphatase (AP), 345.36 ± 65.90 (227.25–490.16) IU/L; calcium (Ca), 8.54 ± 0.18 (8.19–8.90) mg/dL; phosphorus (P), 2.76 ± 0.38 (1.99–3.97) mg/dL; chloride (Cl), 106.05 ± 3.20 (99.00–112.00) mEq/L; sodium (Na), 121.50 ± 4.14 (116.00–132.00) mEq/L; and potassium (K), 3.70 ± 0.42 (2.80–4.40) mEq/L. Comparisons of biochemical ranges obtained for the Brazilian donkey breed with reference ranges for other donkey breeds suggested that most values were similar. Biochemical values determined in the present study serve as reference ranges for donkey populations and can be used for health control and diagnosis of diseases.     

Effects of feeding high levels of cactus (Opuntia fícus-indica Mill) cladodes on urinary output and electrolyte excretion in goats

A study was conducted to determine the effects of feeding spineless cactus cladodes on diuresis and urinary electrolyte excretion in goats. Five bucks were used in a 5 × 5 Latin square experiment with 17-day periods. Experimental diets contained (g/kg dry matter (DM) basis) 370, 470, 570, 670, and 770 spineless cactus cladodes. Water consumption from feed and urine output increased linearly (P < 0.05) as the level of cactus cladodes in the diet increased. However, water intake from drinking was low and unaffected by cactus cladode level. Creatinine clearance and urinary Na excretion were similar for all dietary treatments while K excretion decrease linearly (P < 0.05) as the level of cactus cladodes in the diet increased. Feeding cactus cladodes caused diuresis and reduced urinary K excretion in goats. Possible reasons for these effects include water over-consumption from cactus cladodes and high dietary K intake.     

Ascorbic acid promotes graft-take in sweet pepper plants (Capsicum annuum L.)

The cause of the low survival rate of sweet pepper plants after grafting was investigated and compared with findings of eggplant and tomato plants, and the promotive effect of ascorbic acid (AA) was determined. Sweet pepper plants formed less callus at the cut surfaces of the stem compared to eggplant and tomato plants. Foliar application with 100 mg L⁻¹ AA promoted callus formation at the cut surfaces of the scion stems and improved the survival rate after grafting. We suggest that the low survival rate of grafted sweet pepper plants is caused by their low rate of callus formation, and that AA can be used to promote graft-take through the acceleration of callus formation at the cut surfaces of the stems.