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AIMS: To determine the variability of concentrations of Zn in feed, when used as a supplement to prevent facial eczema, and to determine the variability in concentrations of Zn in serum between cows and herds that are being supplemented with ZnO in feed, using in-shed feeders or on a feed pad.

METHODS: Sixteen commercial dairy farms in the Waikato region of New Zealand were enrolled, that were supplementing cows with ZnO in the feed using either an automatic in-shed feeder (ASF) or a feed pad (FP) using a feed-out or mixer wagon. On each farm 10 cows were selected by the farmer, that were assumed to be representative of the age and liveweight of the herd. Four hours after supplement feeding, each cow was weighed and a blood sample collected for measurement of concentrations of Zn in serum. Three samples of feed were collected from each farm for Zn analysis, from the beginning, middle and end of the feed being distributed. Levene’s test for homoscedasticity was used to analyse whether there were differences in variation of individual concentrations of Zn in serum, and in the feed, between the two feeding systems. Multivariable linear regression was used to examine associations between age, feeding method or liveweight and concentrations of Zn in serum, after accounting for the variability between farms.

RESULTS: Of the 163 cows sampled, concentrations of Zn in serum were between 20–35?µmol/L in 75/163 (46 (95% CI=38–54)%) cows; were <20?µmol/L in 71/163 (44 (95% CI=36–52)%) cows, and >35?µmol/L in 17/163 (10 (95% CI=6–16)%) cows. The variation in concentrations of Zn in serum in individual cows differed between farms (p<0.001), and the variability was greater for cows fed using a FP than ASF (p<0.001). There was no difference in the variation of concentrations of Zn in feed between the two feeding methods (p=0.54), but concentrations of Zn in serum were associated with the amount of Zn offered in feed (p=0.008).

CONCLUSIONS AND CLINICIAL RELEVENCE: There was significant variability between farms in the concentrations of Zn in the serum of cows being supplemented with ZnO in feed. Only 46% of cows sampled had concentrations of Zn between 20–35?µmol/L. Effective management of facial eczema should include monitoring Zn in the feed and in serum to ensure cows are receiving the correct dose they require.  相似文献   
3.
牧草新品种黔草1号高羊茅的选育   总被引:2,自引:0,他引:2  
黔草1号高羊茅是利用贵州地方野生资源作亲本,采用改良混合选择法,经10余年的选育研究育成的新品种。该品种抗逆性强、适应性广、坪用性好、耐践踏、持续性好、绿期长,返青期比引进品种凌志提前7 d,枯黄期晚3 d;种子成熟期集中,种子平均产量比对照品种高20%以上。适应我国长江中下游低山、丘陵等地区种植,是运动场草坪、环境绿化、生态治理的优良草种。  相似文献   
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The aim of this study was to evaluate the effect of leptin administration during superovulation on in vivo goat embryo production. Ten mature does were superovulated with 133 mg follicle‐stimulating hormone (FSH) i.m. in six descending doses at 12‐h intervals. The goats received 4.8 μg/kg human recombinant leptin s.c. (leptin group, n = 5) or phosphate‐buffered saline (PBS) (control group, n = 5) with the first and second FSH doses. The does were mated and subjected to embryo collection by transcervical technique 6 days later. The total number of cells per embryo and the number of cells with fragmented DNA were assessed in selected blastocysts by combining Hoechst 33342 and terminal dUTP nick‐end labelling (TUNEL) staining. Plasma concentrations of oestradiol (E2) and progesterone (P4) were determined by electrochemiluminescence from the day of FSH treatment, on the day of superovulatory oestrus and on the day before embryo collection. Compared with the control group, the does that received leptin had a higher number of transferable embryos (p < 0.005), fewer embryos classified as degenerated (p < 0.001) and fewer TUNEL‐positive cells/blastocyst (p < 0.001). The number of transferable embryos was positively correlated with E2 concentrations on day of oestrus (r = 0.562; p < 0.01) and P4 concentrations on the day of embryo collection (r = 0.912; p < 0.001). We concluded that in vivo leptin administration during FSH treatment improved embryo quality and affected ovarian steroidogenesis in superovulated goats.  相似文献   
6.
Nasopharyngeal cryptococcosis   总被引:1,自引:0,他引:1  
Naturally occurring cryptococcosis in five cats, a dog and a koala is described. Involvement of the nasopharynx was documented in all patients, and nasopharyngeal mass lesions accounted for the major presenting complaints in four. Signs referable to nasopharyngeal disease included snoring, stertor, inspiratory dyspnoea and aerophagia. Diagnoses were made by caudal rhinoscopy using a retroverted flexible endoscope, vigorous orthograde flushing with saline, or at necropsy. Concurrent cryptococcal rhinitis was present in all cases, although involvement appeared limited to the caudal nasal cavity in most cases. Typical signs of nasal cavity disease, such as sneezing and nasal discharge, were often absent. Treatment of nasopharyngeal cryptococcosis should include physical dislodgement or debulking of lesion(s) to provide immediate alleviation of upper airway obstruction, followed by systemic antifungal therapy to eliminate residual infection from the nasal cavity. Infections caused by Cryptococcus neoformans var gattii accounted for a disproportionately large number of these cases.  相似文献   
7.
Static and dynamic mechanical deflections were electrically induced in cantilevered, multiwalled carbon nanotubes in a transmission electron microscope. The nanotubes were resonantly excited at the fundamental frequency and higher harmonics as revealed by their deflected contours, which correspond closely to those determined for cantilevered elastic beams. The elastic bending modulus as a function of diameter was found to decrease sharply (from about 1 to 0.1 terapascals) with increasing diameter (from 8 to 40 nanometers), which indicates a crossover from a uniform elastic mode to an elastic mode that involves wavelike distortions in the nanotube. The quality factors of the resonances are on the order of 500. The methods developed here have been applied to a nanobalance for nanoscopic particles and also to a Kelvin probe based on nanotubes.  相似文献   
8.
 近几年,欧洲各国的养蜂中发现有残留抗生素的问题,提出了世界养蜂行业必须要解决的诸多课题。笔者通过多年的养蜂实践,提出了关于现代养蜂的问题:不适宜的环境下养蜂,对蜜蜂过多采蜜,人工近亲交配导致蜂群种性和抗病性降低,不正确的采蜜时间、方法、措施,使蜂产品的品质降低。为了解决上述问题,提出按蜜蜂的生态、自然养蜂,比如确保蜜源丰富,有大量和无污染的水源和蜜源的养蜂环境,由蜂群的轮流休息来强化蜂群,在无药剂污染的地区养蜂,开发附加值高的蜂产品生产,加强质量管理等措施。  相似文献   
9.
Open carbon nanotubes were filled with molten silver nitrate by capillary forces. Only those tubes with inner diameters of 4 nanometers or more were filled, suggesting a capillarity size dependence as a result of the lowering of the nanotube-salt interface energy with increasing curvature of the nanotube walls. Nanotube cavities should also be less chemically reactive than graphite and may serve as nanosize test tubes. This property has been illustrated by monitoring the decomposition of silver nitrate within nanotubes in situ in an electron microscope, which produced chains of silver nanobeads separated by high-pressure gas pockets.  相似文献   
10.
 在前文已指出了现代养蜂业存在的问题。一方面,蜂群生产负担过重,造成蜂产品的质量下降。为了解决这个问题,提出根据蜜蜂本身具备的生物学能力,必须恢复自然养蜂的想法。另一方面,养蜂是一种产业,因此,做好生产附加价值比较高的蜂产品是很重要的。因此本文介绍关于提高蜂王浆所具有的抗酸化作用,应用蜂王浆抗菌物质的转基因代替生产,以及作者最新的基础研究成果,提出了自然养蜂与近代科学技术的关系,以及养蜂学和养蜂产业的展望。  相似文献   
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