鸭瘟活疫苗生产工艺改进试验

利用尿囊腔接种法替代绒毛尿囊膜接种法生产鸭瘟活疫苗,收获的胚液和绒毛尿囊膜及胎儿的病毒含量(ELD50)均高于<中华人民共和国兽用生物制品规程>2000年版中的病毒含量标准,而且降低了早死率,提高了鸡胚利用率.     

注射用头孢呋辛钠的安全性试验研究

通过试验研究对注射用头孢呋辛钠的安全性进行评价。采用豚鼠和家兔分别进行本品的全身用药过敏性、血管和肌肉局部刺激性及家兔红细胞体外溶血性试验研究。结果显示本品对豚鼠无明显全身过敏性、静脉注射对家兔耳缘静脉无明显局部刺激性、对家兔肌肉注射给药无明显局部刺激性、对家兔红细胞无明显体外溶血性。表明本品的各项安全性均良好,为实际应用提供了有力依据。     

Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems

In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil fungal species changed, with increases in rates of cellulose decomposition. There were also changes in the abundance and species composition of Collembola, fungal-feeding arthropods. These results have implications for long-term feedback processes in soil ecosystems that are subject to rising global atmospheric carbon dioxide concentrations.     

Effects of barefoot trimming on hoof morphology

Objective To monitor changes in hoof morphology in response to barefoot trimming. Methods Seven horses were trimmed every 6 weeks according to barefoot trimming principles, which involved levelling the hoof to live sole, lowering the heels, bevelling the toe and rounding the peripheral wall, while leaving the sole, frog and bars intact. A 4‐month period was allowed to lower the heels sufficiently to achieve a hoof shape representative of the barefoot trim. This was regarded as the starting point for morphological adaptations in response to maintenance of the trim. Hoof morphology was measured from lateral, dorsal and solar view photographs and lateromedial radiographs taken at 0, 4 and 16 months. Changes from 0 to 4 months represented differences between a natural hoof shape and the trim, while changes from 4 to 16 months represented adaptive effects during hoof growth. Results Establishment of the barefoot trim involved significant shortening of the toe, heel and medial and lateral walls, with increases in angulation at the toe, medial and lateral walls, but not at the heel. Maintenance of the trim resulted in a palmar/plantar migration of the heels, with increases in support length, heel angle and solar angle of the distal phalanx (P3). Conclusions Bevelling the toe and engaging the frog and bars in the weight‐bearing function of the foot resulted in elevation of the heel angle and solar angle of P3. These changes may be beneficial in treating under‐run heels and negative solar plane angulation of P3.     

Transition Element-Like Chemistry for Potassium Under Pressure

At high pressure the alkali metals potassium, rubidium, and cesium transform to metals that have a d1 electron configuration, becoming transition metal-like. As a result, compounds were shown to form between potassium and the transition metal nickel. These results demonstrate that the chemical behavior of the alkali metals under pressure is very different from that under ambient conditions, where alkali metals and transition metals do not react because of large differences in size and electronic structure. They also have significant implications for the hypothesis that potassium is incorporated into Earth's core.     

Positive Effects of Melatonin Treatment on the Reproductive Performance of Young Border Leicester Rams Mated to Merino Ewes in Spring: Preliminary Observations

Poor reproductive performance of Merino ewe flocks when mated to Border Leicester rams during spring may be due to seasonality of the Border Leicester breed. Two approaches were taken to test this assumption. Six young (12 months old) or six mixed‐age (12, 24 and ≥36 months old) Border Leicester rams were either treated or not treated with melatonin implants (2 × 2 design) 6 weeks before the four groups of rams were each put with approximately 300 Merino ewes for an 8‐week mating period. Implants were inserted in early September (experiment 1). The second approach was to yard or not yard ewes and mixed‐age rams on several occasions during the first 3 weeks of the mating period (experiment 2). Pregnancy rate and twinning percentage were assessed by ultrasonography. In experiment 1, melatonin treatment in young rams increased (p < 0.001) pregnancy rate from 5.0% to 92.6%, but mixed‐age rams did not respond (90.7% vs 89.5% for melatonin and non‐melatonin treatments, respectively). Twinning rate was similar (p > 0.05) for ewes mated to either melatonin or non‐melatonin‐treated young rams (36.8% vs 40.0%, respectively), whereas melatonin significantly improved (p < 0.05) twinning rate in those ewes mated to mixed‐age rams (49.1% vs 36.1%). After 6 weeks of melatonin treatment, scrotal circumference was greater (p < 0.05) in both young and mixed‐aged rams than in untreated counterparts. In experiment 2, yarding of ewes and rams overnight on several occasions early in the mating period reduced (p < 0.001) pregnancy rate compared with non‐yarded counterparts (89.5% vs 65.5%). Twinning rate was not affected (37.7% vs 36.1%, respectively). In summary, melatonin treatment of Border Leicester rams significantly improved flock reproductive performance in spring due to improved pregnancy rates with young rams and improved litter size with mixed‐age rams.     

Liposome-encapsulated oxymorphone provides prolonged relief of post-surgical visceral pain in rats

A delayed‐release formulation of liposome‐encapsulated oxymorphone was produced using a novel dehydration–rehydration technique. The purpose of this study was to (i) compare the analgesic properties of this preparation with those of repeated injections of standard oxymorphone in rats with post‐operative visceral pain and (ii) determine whether liposome‐encapsulated oxymorphone differed from standard oxymorphone in duration of the effect. Visceral pain was elicited in approximately 300 g Sprague–Dawley rats by intestinal resection performed under isoflurane anesthesia. Rats were monitored with pulse oximetry; mean anesthesia time (35 ± 10 minutes) did not differ between the groups. Rats were randomly divided into two groups: Group 1 received 1.2 mg kg^?1 liposome‐encapsulated oxymorphone SC once at skin closure and 0.2 mL of saline SC every 4 hours; Group 2 received 0.2 mL liposome‐encapsulated sucrose SC once at skin closure and 0.3 mg kg^?1 standard oxymorphone SC every 4 hours. In both groups, a behavioral ethogram for pain score (grooming, porphyrin staining, body position) was recorded every 4 hours for 48 hours after surgery. Observers were blinded to the treatment. Body weight, food consumption, and urine output were recorded daily for 7 days after anesthetic recovery. Data were analyzed using anova , with significance at p < 0.05. Based on the behavioral pain score, a single injection of liposome‐encapsulated oxymorphone was as effective for relief of post‐surgical visceral pain in rats as multiple (every 4 hours) injections of standard oxymorphone administered over a 48 hour period (p = 0.18). In rats, given one dose of liposome‐encapsulated oxymorphone, the mean body weight change from day 0 to day 7 was +9.4 g, whereas rats given multiple injections of standard oxymorphone had a mean body weight change of ?3.6 g over this time (p < 0.01). Mean daily food consumption was significantly less in rats given multiple injections of standard oxymorphone (p < 0.05). There was no difference between groups in urine production. In conclusion, a single dose of liposome‐encapsulated oxymorphone was effective in treating visceral pain in rats. Rats treated with liposome‐encapsulated oxymorphone had improved recovery, based on body weight changes and food consumption, compared with rats treated with multiple doses of standard oxymorphone. Liposome‐encapsulated oxymorphone offered advantages including provision of effective analgesia, prolonged dosing intervals, and minimal handling stress.     

An outbreak of toe ulcers,sole ulcers and white line disease in a group of dairy heifers immediately after calving

Abstract

CASE HISTORY: An outbreak of severe lameness was reported on a 780-cow spring-calving dairy herd in the Manawatu region within 1–3 weeks of calving, which affected over 90% of a group of 150 dairy heifers. Approximately 3 weeks before the planned start of calving heifers had been fed maize and grass silage on a concrete feed pad for 3–4 h per day, and mixed with a group of adult cows.

CLINICAL FINDINGS: During treatment for lameness, the feet of 28 lame heifers were closely examined. Seventy lesions were recorded in the claws of these heifers. The predominant lesion was severe solar and white line haemorrhage, with much of the haemorrhage focussed at the site at which sole ulcers are normally seen. White line disease was seen in nine claws and sole ulcers in four. Additionally, a lesion which is not commonly recorded in New Zealand, a toe abscess arising from separation of the white line from the sole in the abaxial region of tip of the toe was recorded in 11 claws. The clinical impression was that the soles of the affected heifers were very thin. This was supported by examination of the feet of eight heifers using ultrasonography that indicated heifers with hoof horn haemorrhages had very thin soles (estimated mean 4.1 mm) and that these soles were thinner than those in non-lame heifers without haemorrhages.

DIAGNOSIS: The pattern of disease seen in these heifers closely matched that seen in an outbreak of lameness in heifers in Florida, which was linked to thin soles resulting from excess hoof horn wear. The clinical signs and findings of the examination using ultrasonography strongly implicated thin soles as the underlying cause of lameness on this farm. An on-farm investigation revealed a combination of heifer behaviour and prolonged exposure to wet concrete on the feed pad were the primary causes of excess wear that resulted in thin soles.

CLINICAL RELEVANCE: This was an unusual outbreak of lameness in a group of newly calved heifers. The problem highlights the value of good management during the transition of heifers at pasture to the lactating herd standing on concrete for long periods, in the control of lameness.