美洲山核桃的生长和早熟的关系

全球最大的美洲山核桃育种计划是由USDA-ARS执行的，其总部设在两个地点：美国德克萨斯州大学站和布朗武德。该项目和全国很多州农业试验站合作后自1931年起已先后育成24个品种。在控制条件下杂交后，在大田条件下评价这些树的农艺表现，再从中选择最佳的无性系在全国美洲山核桃高代无性系试验系统(NPACTS)进行进一步的试验。     

氧化应激与疾病

2．4胎衣不下（RIM） 该症是导致抗氧化状况衰竭的第一步。奶牛RFM可引起子宫内膜炎、连续的卵巢周期延误、妊娠推迟等系列损失。     

Rickets in yearling steers wintered on a swede (Brassica napus) crop

Rickets was diagnosed in a group of 80 yearling Angus steers wintered for three months on a crop of swedes (Brassica napus) in the Kimbolton area. Growth rate was poor and several steers developed lameness during the final three weeks on the crop. Five animals were euthanased after developing bone fractures. Necropsy of two animals revealed soft ribs, enlarged costochondral junctions and irregularly thickened growth plates in long bones. Histologically there were islands of hypertrophic cartilage within metaphyses and disruption of metaphyseal trabeculae. Thickened, irregular, trabeculae were sometimes lined by wide osteoid seams. Phosphorus deficiency was considered to be the most likely aetiology of the osteodystrophy. The dry matter content of the swedes was only six percent, and in order to satisfy their phosphorus requirements each steer would have had to ingest approximately 330 kg of swedes per day. Rickets is an uncommon disease of grazing animals in New Zealand and to our knowledge this is the first report of its occurrence in cattle.     

Thromboembolic meningocephalitis caused by Haemophilus somnus infection in a bull calf-a new disease in New Zealand

Thromboembolic meningoencephalitis (TEME) caused by Huemophilus somnus infection was diagnosed for the first time in New Zealand in an eight month old bull calf. Clinical signs included pyrexia, excessive salivation, recumbency, opisthotonus and rigidity of the front legs. Multiple red, malacic foci (1-10 mm in diameter) were visible grossly on the surface of the cerebrum and cerebellum, and were scattered throughout the brain parenchyma. Histologically these lesions consisted of focal haemorrhage, necrosis and neutrophilic infiltration. Fibrin thrombi and colonies of gram negative bacteria were present in many small blood vessels within necrotic foci. An organism with the morphological and biochemical characteristics of Haemophilus somnus was cultured from the brain. Although TEME is an important disease of feedlot cattle in North America and Europe it is relatively uncommon in cattle grazing pasture and is therefore unlikely to become a major problem in New Zealand.     

Selenium levels of beef cattle in southeastern british columbia relative to supplementation and type of pasture

Moderate to extremely low levels of selenium in hay were related to marginally deficient levels of selenium in sera from cattle in the Windermere Valley of southeastern British Columbia. Deficiency was most pronounced in cattle fed local hay during the winter or grazed on fertilized/irrigated pastures. Cattle on range had adequate levels of serum selenium. When sodium selenite was fed at 1.0 and 3.5 mg per head per day, serum selenium levels increased commensurate with the dose. Clinical observations indicated that a variety of clinical problems disappeared after injection or supplementation with selenium/vitamin E.     

An osteodystrophy apparently caused by vitamin D deficiency in growing pigs

An osteodystrophy with features of both rickets and fibrous osteodystrophy was diagnosed in growing pigs housed indoors and fed on a diet deficient in vitamin D. Affected pigs were severely lame and preferred to remain recumbent. At necropsy, the long bones had reduced breaking strength and in one five-month-old pig the articular surfaces of both proximal humeri were indented due to collapse of subchondral bone. Microscopic changes in the bones included prominent osteoclastic activity in the proximal metaphyses, variable myelofibrosis, trabecular microfractures, and focal thickening of the hypertrophic zone in some growth plates. Treatment consisted of an injection of Vitamin D3, addition of dicalcium phosphate to the diet for 18 days and long-term supplementation of the diet with fat-soluble vitamins. This is the first report of an osteodystrophic disease in pigs in New Zealand.     

Selenium, vitamin E and polyunsaturated fatty acid concentrations in goat kids with and without nutritional myodegeneration

Mean selenium and vitamin E (alpha-tocopherol) concentrations in the liver, myocardium and skeletal muscle of nine goat kids with nutritional myodegeneration (NMD) were significantly lower than those in a group of nine kids dying from other causes. Each of the 18 kids was from a different property in the southern half of the North Island. The polyunsaturated fatty acid composition of the liver, myocardium and skeletal muscle was not significantly different between the two groups, but the overall level of peroxidisable polyunsaturated fatty acids appeared high in both groups. A further 21 kids with confirmed NMD and live 'controls', submitted as routine cases to Palmerston North Animal Health Laboratory, were included with the above 18 kids in a comparison of liver selenium and alpha-tocopherol concentrations. Kids with NMD had liver selenium concentrations ranging from 170-1100 (mean = 380) nmol/kg and alpha-tocopherol from 0.7-11.0 (mean =2.2) micromol/kg. In control kids, the liver selenium concentration ranged from 530-4300 (mean = 1220) nmol/kg and a-tocopherol from 1.7-14.0 (mean = 5.6) pmollkg. Although these ranges overlapped, the results suggest that liver selenium concentrations <500 nmol/kg and alpha-tocopherol concentrations <2.5 micromol/kg should be regarded as deficient. Liver selenium concentrations from 500-1100 nmol/kg and alpha-tocopherol concentrations from 2.5-10 micromol/kg should be considered marginal. Goat kids appear to require more selenium than lambs or calves which may explain the higher prevalence of NMD in kids. In some cases, however, the disease is associated with low alpha-tocopherol suggesting that supplementation with selenium alone may not always be sufficient.     

Serum glutathione peroxidase activity reflects short-term increases in selenium intake in goats

The objective of this study was to determine if serum glutathione peroxidase activity reflects short-term changes in the selenium status of goats. Angora goat kids (n=14) were fed pelleted luceme containing 20 microg/kg of selenium, and treated orally with either selenium (0.1 mg/kg of liveweight weekly, as sodium selenate) or de-ionised water. Serum activity of glutathione peroxidase was increased in response to supplementation and differed from that of controls within 24 hours of supplementation. The change in serum glutathione peroxidase activity during the 21 days after the start of weekly supplementation closely followed changes in serum selenium concentration. The results of this study suggest that serum glutathione peroxidase activity reflects the short-term improvement in the selenium status of Angora goat kids following oral supplementation with sodium selenate.