Selenium in New Zealand pastures

In grasses and clovers the highest concentrations of selenium were found in the leaves. The selenium content of different species in spring pastures on the same soil type did not vary widely although the slower growing and more deeply rooting species contained higher levels. The concentration of selenium in a pasture varied with time of the year, the lower levels being usually associated with conditions that stimulated rapid growth of the herbage, although factors other than growth rate were also involved. Lucerne appeared to be unusual in that in some areas it accumulated much higher levels of selenium than was found in other associated species. A very wide variation in levels of selenium in pastures growing on different soils has been observed (3-1500 ng/g).

Selenium-responsive unthriftiness in grazing lambs occurred where the selenium content of spring pastures was <20 ng/g. Pastures containing >30 ng/g were apparently adequate while intermediate levels were probably marginally deficient.     

AN EXAMINATION OF THE SELENIUM NUTRITION OF SHEEP IN VICTORIA

The selenium nutrition of sheep throughout Victoria was assessed by a survey of the blood glutathione peroxidase activity in 708 flocks. It was shown that the blood glutathione peroxidase activity in sheep had a seasonal variation with lowest levels in the spring. The enzyme activity was correlated with the blood selenium concentration. Areas where blood selenium was less than 0.03 μg/ml in spring were defined. Sheep with low selenium nutrition were grazing pastures in the high rainfall areas on acid soils, particularly those derived from granite.
Selenium concentrations in pasture samples examined were greater than 0.02 mg/kg, and it was found that superphosphate application had no significant effect on the selenium content of pasture. However, management practices such as high stocking rates and rates of application of superphosphate to pasture were associated with low blood glutathione peroxidase activities in sheep.
It was concluded that the selenium nutrition of most of the sheep flocks in Victoria is adequate, and that the deficient areas are localised. There seems little requirement for supplementation of adult sheep. As the delayed type of white muscle disease in spring lambs appears to be the main selenium-responsive disorder, direct supplementation of lambs in the low selenium areas would be the most effective method of ensuring adequate selenium nutrition.     

Ovine white-liver disease (OWLD). Serum copper and effects of copper and selenium supplementation

Serum copper was generally higher in lambs affected with ovine white-liver disease (OWLD) than in cobalt/vitamin B12 supplemented lambs grazing the same pastures. Although the copper content of the grass was very low on the OWLD pastures, dosing lambs with Cu alone resulted in worsening of the clinical condition and aggravation of clinical pathology. Dosing with selenium had no effect on OWLD. Dosing with a combination of Co, Se and Cu resulted in normal lamb growth and normal laboratory tests. Lambs growing well on other pastures (H) showed elevated serum Cu when they were subclinically B12 deficient.     

西藏日喀则地区栽培牧草中7种微量元素的分布特征

通过对西藏日喀则地区3科43种栽培牧草中的铁、锰、钼、铜、锌、硒、钴7种微量元素的测定,探究微量元素在不同科属牧草中的分布特征。结果表明,西藏日喀则地区栽培牧草中微量元素的分布存在一定的规律性。总体而言,铁含量最高,可达800μg/g;锌次之,最高接近200μg/g;硒含量最低,含量变幅为0.002~0.013μg/g。3科牧草中,禾本科牧草铁含量相对较低,锌、铜含量相对较高;藜科牧草锌、铜含量相对较低,铁、锰含量相对较高;豆科牧草多数微量元素含量相对居中;各科牧草中的铁、锌、铜含量均属较高水平,钴均属中等水平;锰、硒、钼在3科间含量水平不一致。     

内蒙古四子王旗草原土壤—牧草—放牧绵羊生态系统微量元素的季节变化研究与盈亏分析

[目的]对内蒙古四子王旗荒漠草原土壤—牧草—放牧绵羊生态系统中的微量元素含量进行分析,研究不同季节放牧绵羊体内矿物质元素的盈亏状况,评定矿物质元素营养限制因子。[方法]选取6只体况良好的体重为（39.65±2.25）kg的放牧蒙古羊母羊作为试验羊,测定该地区牧草嫩草期（6月）、生长期（9月）和枯草期（11月）放牧绵羊的体重、采食量、排粪量和排尿量;检测牧草3个生长时期草原土壤、牧草以及放牧绵羊血清中的7种矿物质元素（铁、铜、锰、锌、硒、钼、钴）含量;借助采食量模型预测放牧绵羊在牧草不同生长时期的矿物质元素摄入量;利用代谢试验测定从粪、尿中排出的矿物质元素含量,计算放牧绵羊体内矿物质元素沉积量。[结果]放牧绵羊的体重和采食量在牧草3个生长时期之间差异均极显著（P<0.01）,枯草期排粪量极显著（P<0.01）高于嫩草期和生长期。草原土壤、牧草及绵羊血清中的铁元素含量在牧草不同生长时期之间差异均不显著（P>0.05）,铁元素含量均不存在缺乏情况。枯草期牧草的铜元素含量极显著（P<0.01）低于嫩草期和生长期,枯草期绵羊体内沉积的铜元素含量极显著（P<0.01）低于生长期,并出现了负沉积。草原土壤、牧草以及绵羊采食和体内沉积的锰、钼元素含量在牧草不同生长时期之间存在极显著（P<0.01）差异,但两种元素不存在缺乏情况。嫩草期绵羊血清中的锌元素含量显著（P<0.05）高于生长期和枯草期;草原土壤、牧草、绵羊体内沉积的锌元素含量在牧草不同生长时期之间虽无显著（P>0.05）差异,但存在缺锌的情况。草原土壤中的硒元素含量在牧草生长期最高,极显著（P<0.01）高于嫩草期和枯草期,嫩草期和生长期牧草中的硒元素含量低于正常水平下限,而枯草期牧草中未检测到硒元素;绵羊血清中硒元素的含量在牧草不同生长时期之间差异不显著（P>0.05）,但均处于正常水平的下限。草原土壤中的钴元素含量在牧草不同生长时期之间差异不显著（P>0.05）,但均低于标准值;枯草期和嫩草期绵羊体内沉积的钴元素含量极显著（P<0.01）低于生长期。[结论]建议在该地区全年以适当形式为放牧绵羊补锌和硒元素,冬季或春季可适当补饲含铜和钴的微量元素制剂。     

Effects of concentrate supplementation on blood mineral concentration of growing upgraded Philippine goats

A total of 32 4‐month‐old‐upgraded Philippine goats with mean bodyweight of 13.5 kg were used to study the effects of concentrate supplementation on mineral status of growing goats. All animals received a basal diet comprised of different forage species. Twenty of the animals were supplemented with concentrate at a rate of 150–200 g dry matter/day while the remaining 12 animals were not supplemented. Blood sampling and bodyweight measurement were done every 2 weeks during the 5 months of experiment. Forage, concentrate and blood sulfur, calcium, phosphorus, magnesium, copper, zinc and selenium concentration were analyzed after wet digestion. Forage mineral contents, except for zinc and selenium, were sufficient for requirements of ruminants. Concentrate mineral contents were much higher than the requirements, but did not exceed the toxic levels. The concentrate supplementation resulted in high (P < 0.05) plasma phosphorus, copper, zinc, whole blood selenium concentrations and bodyweight of growing goats, although some supplemented animals showed plasma zinc concentration below the lower critical level. It was recommended that pellets, glass bolus or capsules that contain deficient minerals, such as zinc and selenium, should be used in the study area.     

混播种类和群体结构对豆禾牧草混播系统氮素利用效率的影响

为从物种多样性和空间结构方面阐明豆禾牧草混播系统高效生产机制,将混播种类(单播、2种牧草混播、4种牧草混播和6种牧草混播)、混播群体空间结构(行距+同行/异行/异行阻隔)作为影响因素,从豆科牧草固氮能力、转氮效率、氮素营养竞争、种间相容性和生产性能分析和比较豆禾牧草在不同混播方式中氮素固定、转移和利用效率对混播系统生态功能的贡献程度。结果表明:1)混播处理的牧草产量、N产量均显著高于单播(P<0.05),生产性能显著提高;但生产性能未随混播种类的增加而提高,异行混播+30 cm行距的混播群体结构具有较高的生产性能。2)固氮量随混播种类的增加而呈下降趋势,转氮量和转氮率随混播种类的增加而呈先下降后上升的趋势,而固氮率和贡献率变化不明显;异行混播+30 cm行距的混播群体结构具有较高的转氮量、转氮率和贡献率。3)营养竞争比率随混播种类的增加变化不明显,豆科牧草相对产量和相对产量总和随混播种类的增加而呈增加趋势;异行混播+30 cm行距的混播群体结构具有较高的豆科牧草相对产量和相对产量总和,但营养竞争比率较低。4)牧草产量与转氮量呈极显著正相关(P<0.01),而相对产量总和与氮素营养竞争比率呈极显著负相关(P<0.01)。因此,混播种类对于豆禾牧草混播系统生产性能的提升作用有限,高养分利用效率的物种组合可能更为关键;通过混播群体空间结构的优化可以使豆禾混播牧草根系氮素固定、转移、利用途径和效率得到提高,为混播系统生产性能的提升提供了重要途径。     

Effects of a Rest–Rotation Grazing System on Wintering Elk Distributions at Wall Creek,Montana

The large-scale influence of livestock grazing in the western United States generates a need to integrate landscape management to incorporate both wildlife and livestock. The purpose of this project was to evaluate the effects of four different grazing cells (spring grazing, summer growing-season grazing, fall grazing, and resting) on wintering elk resource selection within the Wall Creek range in southwest Montana. We collected biweekly observations of elk (Cervus elaphus) numbers and distributions across the winter range from 1988 to 2007. Using a matched-case control logistic regression model to estimate selection coefficients, we evaluated the effects of annual green-up conditions, winter conditions, landscape features, and grazing treatment on elk group resource selection within the grazing system. We found that within the grazing system, elk groups preferentially selected for rested pastures over pastures that were grazed during the previous spring (1 May–1 June), summer (1 June–15 July), and fall (15 September–30 September). The strength of selection against the pasture grazed during the summer growing season was strongest, and pastures grazed during the spring and fall were selected for over the pasture grazed during the summer. The number of elk utilizing the grazing system increased in the 19 yr following implementation of the grazing system; however, total elk herd size also increased during this time. We found no evidence that the proportion of the elk herd utilizing the grazing system changed following implementation of the rest–rotation grazing system. Wintering elk group preference for rested pastures suggests rested pastures play an important role in rotation grazing systems by conserving forage for wintering elk. Additionally, rested pastures provide important cover for a host of other wildlife species. We recommend wildlife managers maintain rested pastures within rotation grazing systems existing on ungulate winter range.     

酵母硒对吉林芦花鸡蛋品质及生产性能的影响

为研究添加不同浓度的酵母硒对吉林芦花鸡生产性能、蛋硒含量、蛋品质、鸡蛋胆固醇含量的影响,试验选用健康的21周龄吉林芦花鸡96只,平均体重1622 g。随机分成4组,每组6个重复,每个重复4只鸡。对照组饲喂基础日粮,其他3组分别添加0.3、0.6、0.9 mg/kg的酵母硒。预试期5 d,正式期21 d。结果表明:各组间料蛋比、采食量、哈氏单位、鸡蛋颜色无显著差异(P>0.05);0.3 mg/kg酵母硒组的平均蛋重极显著低于其他3组(P<0.01),产蛋率、软破壳蛋率均极显著高于其他3组(P<0.01);0.6 mg/kg酵母硒组的蛋黄比率、软破壳蛋率极显著低于其他3组(P<0.01);0.9 mg/kg酵母硒组胆固醇含量极显著低于其他3组(P<0.01);料蛋比(P=0.087)和胆固醇(P=0.061)随着酵母硒添加量的增加有降低的趋势。0.6 mg/kg酵母硒组蛋硒含量极显著高于对照组和0.3 mg/kg酵母硒组(P<0.01),显著高于0.9 mg/kg酵母硒组(P<0.05)。综上,在本试验条件下,酵母硒适宜添加量为0.6 mg/kg。     

Use of nonergot alkaloid-producing endophytes for alleviating tall fescue toxicosis in stocker cattle

Grazing studies were conducted to determine cattle growth performance, evaluate toxicosis, and compare grazing behavior in stocker cattle grazing nonergot alkaloid-producing endophyte-infected (AR542 or AR502), endophyte-free (E-), or wild-type toxic endophyte-infected (E+) Jesup, Georgia-5, and Kentucky-31 tall fescue. Replicated 0.81-ha tall fescue paddocks were established at the Central Georgia Branch Station at Eatonton and the Northwest Georgia Branch Station at Calhoun during October 1998 and were stocked with beef cattle for autumn and spring periods from fall 1999 through spring 2002. Mean ergot alkaloid concentrations were higher (P < 0.01) on E+ pastures than the other treatments at both locations. At Calhoun and Eatonton, post-treatment serum prolactin concentrations were decreased (P < 0.01) on E+ compared with AR542, AR502, and E- tall fescue. Cattle on AR542, AR502, and E- pastures had lower (P < 0.05) post-treatment rectal temperatures than cattle grazing E+ tall fescue during spring at Eatonton and Calhoun. Calf ADG was higher (P < 0.05) on AR542, AR502, and E- as compared with E+ tall fescue during autumn and spring grazing at Eatonton, and at Calhoun, cattle on E+ pastures had lower (P < 0.05) ADG in both autumn and spring. Gain/hectare was higher (P < 0.05) on AR542, AR502, and E- than on E+ during autumn at Eatonton and during spring at both locations. In autumn at Calhoun, gain/hectare was greater (P < 0.05) on AR502 and E- compared with E+ tall fescue. During April, May, and June, cattle grazing E+ pastures at Eatonton spent more (P < 0.01) time idling, more (P < 0.01) time standing, and used more (P < 0.01) water than cattle on AR542 and E- tall fescue. Daily prehensions and biting rate were each higher (P < 0.01) on AR542 and E- tall fescue than E+ tall fescue in both grazing seasons. There were no differences among pasture treatments for bite size in either spring (P = 0.50) or autumn (P = 0.34). Steers grazing E+ pastures had lower DMI than steers grazing AR542 and E- pastures during spring (P < 0.10) and lower DMI than steers grazing E- pastures during autumn (P < 0.05). Daily steer water usage was decreased (P < 0.10) in E+ pastures compared with AR542 and E- pastures during late fall. These results indicate that nonergot alkaloid-producing endophyte technology is a promising option for alleviating tall fescue toxicosis in stocker cattle.     

Energy and protected protein supplements to lambs on endophyte-infected tall fescue pasture

The effect of supplements on intake, digestibility, N retention, ADG and blood and body composition of growing lambs fed cut herbage or grazing KY 31 tall fescue (Festuca arundinacea Schreb.) pastures at two levels of N fertilization (92 and 318 kg/ha) was determined. Supplements were corn (C), corn with soybean meal (U-SBM) and corn with heat-treated SBM (H-SBM). Metabolism trials were run at three growth stages in the 1st yr with 24 lambs. Although all supplements increased total DMI and DM digestibility, they decreased NDF digestibility relative to grass (G), with no difference between supplements; C depressed apparent CP digestibility. Nitrogen retention increased from -2.5 g/d on G to -.4 g/d on C and 3.2 and 4.1 g/d on U-SBM and H-SBM, respectively, for combined periods and N rates. Blood urea N (BUN) concentrations differed (P less than .01) in the following order: G greater than U-SBM greater than H-SBM greater than C. In the 2nd yr, lambs (n = 64) grazed fescue pastures at the same N fertilizer rates and were given the same supplements. Gains were not different (P less than .05) on low-N (LN) and high-N (HN) pastures. Seasonal ADG were 80, 115, 122 and 130 g/d for G, C, U-SBM and H-SBM treatments, respectively, with no difference (P less than .05) between U-SBM and H-SBM. At slaughter, lambs from G had lower dressing percentages (P less than .05) and fat content (P less than .01) than lambs on C, U-SBM and H-SBM treatments, with no differences between supplements. Results indicated a better performance of growing lambs on fescue with both energy and protein supplements. Response to protected vs unprotected protein was small.     

Escape protein supplementation of yearling steers grazing smooth brome pastures

Two grazing trials utilizing individually supplemented yearling steers were conducted to study the effect of supplemental escape protein on steer performance during the active growth periods, spring and fall, of smooth brome (Bromus inermis). Graded levels (0, .11, .23 and .34 kg.head-1.d-1) of an equal-protein-basis mixture of bloodmeal and corn gluten meal were offered daily, replacing corn starch, which was used as the negative control. All steers received 582 g supplemental dry matter per day. Supplementation with escape protein improved daily performance in both spring (P less than .01) and fall (P less than .02). Analysis of pooled data from both trials indicated a linear (P less than .01) and quadratic (P less than .05) increase in steer performance with increasing level of escape protein in the diet. Analysis of grass samples collected throughout and composited over each trial demonstrated that grass protein was highly degraded in the rumen. Using a modified dacron bag technique, 12-h degradability was found to be 80 to 90% of the potentially digestible protein fraction. Rates of protein degradability were 14 and 11.7%/h. Assuming 5%/h rate of passage, escape protein was calculated to be 9.2 and 13.1% of total protein. As a result of the significant growth response observed above that of the energy-supplemented controls and the high ruminal protein degradabilities of the grass observed in the laboratory, it was concluded that growing ruminants grazing actively growing smooth brome pastures were deficient in metabolizable protein.     

戈壁草原蒙古羊春季羔羊铜缺乏症的研究

[目的] 确定内蒙古苏尼特左旗北部地区春季发生的戈壁草原蒙古羊羔羊发病、死亡现象的主要原因。[方法] 选取3户羔羊发病情况最为严重的牧户采样,每户各采集5只发病羔羊的血液样本、放牧草场的饮用水样本,以及羔羊所处环境中3种主要牧草（红砂、珍珠猪毛菜和盐爪爪）样本和土壤样本,同时采集当地种羊场15只相同品种健康羔羊的样本作为对照,测定上述样本中的10种矿物质元素（钙、磷、铁、锰、铜、锌、镁、钼、硒、钴）的含量。[结果] 发病羔羊血液中铜和镁的含量显著（P<0.05）低于同品种健康羔羊,钼的含量显著（P<0.05）高于同品种健康羔羊,其他矿物质元素的含量差异不显著（P>0.05）。发病羔羊所处环境中饮用水的镁和钙含量较高。发病羔羊所处环境中红砂的钼、铁、锰和硒含量均高于文献报道值,其他矿物质元素含量均处于正常范围;盐爪爪的钼、铁、锰、硒、镁和钴的含量高于文献报道值,其他矿物质元素含量均处于正常范围;珍珠猪毛菜、红砂和盐爪爪的铜钼比分别为15.96∶1、0.23∶1和2.34∶1。发病羔羊所处环境中土壤样本的铜、铁、锰、硒、钴含量均低于文献报道值,镁、钙和磷含量均高于文献报道值,钼和锌含量在正常范围内。[结论] 该地区戈壁草原蒙古羊羔羊发病、死亡的原因主要是放牧羊摄入铜不足、钼超标、铁和锰等矿物质元素摄入量过多,导致羔羊对铜的吸收发生障碍,最终引起继发性铜缺乏症。     

Factors affecting animal performance during the grazing season in a mountain cattle production system

The factors influencing weight changes during the grazing season of Brown Swiss autumn-calving cows and Brown Swiss and Pirenaica spring-calving cows and their calves were studied over an 8-yr period in Spanish mountain conditions. The data set comprised 552 annual production cycles of cows that calved in two consecutive years. The animals grazed on alpine ranges during the summer and on forest pastures in the spring and autumn. They were housed during the winter and fed at different feeding levels (83 to 117% of their energy requirements) throughout the years of study. Weights were recorded every 3 mo and corrected to account for changes of digestive content and fetal growth, using theoretical relationships. Cow weight gains both on forest pastures and high mountain ranges were higher in autumn- than in spring-calving Brown Swiss cows, and therefore also during the whole grazing season (52.1 vs 7.7 kg, respectively, P < 0.001). Therefore, weight at calving and thereafter was significantly higher in autumn- than in spring-calving cows, which was associated with better reproductive performance (35.5 vs 49.1 d from calving to first ovulation, P < 0.01). In the spring-calving herd, Pirenaica cows had slightly higher gains than Brown Swiss cows during the grazing period (18.5 vs 7.7 kg, P < 0.001), mainly due to their higher gains on forest pastures, but their reproductive performance was similar (44.5 vs 49.1 d from calving to first ovulation, respectively, not statistically significant). Gains were higher in multiparous than in primiparous cows (31.1 vs 14.1 kg, respectively, P < 0.001), especially in the case of Brown Swiss cows, which were younger at first calving. Gains were affected by year of study (P < 0.001) and previous weight changes during the housing period (r = -0.35 and r = -0.21 in autumn- and spring-calving cows respectively, P < 0.001). In the case of autumn-calving cows, performance on pasture was also affected by the stage of pregnancy at housing (r = -0.51, P < 0.001). Growth rates through lactation were higher in autumn- than in spring-born calves (P < 0.001), although the shorter lactation period resulted in lower weight at weaning of the former (P < 0.001). Breed was a significant source of variation in the performance of spring-born calves, weights and gains being higher in Brown Swiss than in Pirenaica calves (P < 0.001).     

The selenium content of milk

The selenium content in milk of dairy cows from different countries varies between 2 and 60 micrograms/kg, because of differences in the selenium content in the feeds. With an increasing selenium content in the feed a decreasing part is secreted into the milk. A bigger part is utilized from natural selenium compounds in the feed than from selenite. In own investigations milk from Swedish cows had significantly lower selenium content during summer and autumn than during winter and spring (p less than 0,0001). The LS-means between different regions also differed significantly (p less than 0,0001). From the autumn of 1980 the feed manufacturers have been allowed to add sodium-selenite to concentrates and mineral feeds in amounts permitting a selenium content of 0,1 mg/kg DM in the total ration of dairy cows. The year after the selenium fortification was allowed, the LS-means for the selenium content of milk were 1 microgram/kg higher than the year before (p less than 0,001). In the southern parts of Sweden the selenium content was 8-10 and in the central and northern parts 7-9 micrograms/kg. These means were substantially lower than the figure of 15 micrograms/kg which was reported from the central part of Sweden two decades ago. The low selenium content in the milk during summer in some parts of Sweden could possibly mean that there is still a risk of selenium deficiency among the cattle. Anyhow the milk will not always cover the selenium requirement of the sucking or milkfed calf.     

Effects of supplemental dietary tannins on the performance of white‐tailed deer (Odocoileus virginianus)

Tannins are natural and nutritionally significant components of the diets of browsing ungulates. In trials on supplemented pastures and in drylots, we estimated dry matter intake (DMI), weight gain, and urea N, potassium, cortisol and creatinine in urine of captive white‐tailed deer fed pelleted diets that differed only in the respective quebracho tannin (QT) content. The low control, medium and high QT rations were 3.6, 63 and 152 g/kg DM respectively. There was no tannin‐free pellet option. Trials were divided into winter pasture, restricted choice and spring growth. In winter pasture trial on pasture using QT, deer reduced QT intake relative to that expected under random foraging. This aversion was also apparent during the spring growth trial. While DMI in the winter pasture trial remained similar among treatments (p > 0.05), averaging 130 g/kg^0.75/day, deer gained more weight (p < 0.05) when given a choice that included the high QT ration. During subsequent spring growth, DMI and weight gains generally exceeded those of the winter period. Unlike the winter pasture trial, weight gains in spring growth trial were higher (p < 0.05) in the low‐control QT treatment. In the restricted choice trial, weight gain was again higher (p < 0.05) for deer fed a low‐control QT diet. The urea N/creatinine ratio of deer fed the low‐control QT diet (0.0357) was over three times that of deer fed the high QT diet (0.0107). Neither potassium/creatinine nor cortisol/creatinine ratios were affected by diet (p > 0.05). Collectively, these results suggest that although deer do not avoid tannins, and even ingested up to 5% under the choice options in these trials, the effect of tannins on deer performance may vary by season as well as by foraging opportunities.     

Plasma growth hormone concentrations in female mithun (Bos frontalis) of different ages: relations with age and body weight

The role of growth hormone (GH) in postnatal somatic growth is well established. Its basal level and relation to growth performance in different age group mithun (Bos frontalis), a semiwild ruminant has not been characterized until now. To estimate the normal blood GH level and also to assess the influence of age and body weight (BW) on blood GH level in captive mithuns, a total of 65 female mithuns was divided into six age groups (group I, 0-6 months; group II, >6-12 months; group III, >1-2 years; group IV, >2-2.5 years; group V, >2.5-3.0 years and group VI, >3.0 years). Blood samples collected weekly for six consecutive weeks were assayed for GH. GH was also estimated in the samples collected from six growing mithuns at -60, -45, -30, -15, -10, -5 and 0 min prior to GH-releasing hormone (GHRH) administration for calculation of basal GH level and at 5, 10, 15, 30 min and thereafter at 15-min interval up to 8 h post-GHRH to assess blood GH response following GHRH administration in growing mithuns. For calculation of basal plasma GH in adult mithuns, GH was measured in blood samples collected at 30-min interval for 24 h from four animals. BW of all animals was recorded on two consecutive days per week and average of weekly BW was considered for growth rate calculation. It was found that both mean GH and GH per 100 kg BW between the age groups differ (p < 0.01). With increasing age and BW, GH and GH per 100 kg BW both decreased (p < 0.01). The age group with higher plasma GH and GH per 100 kg BW showed higher growth rates (r = 0.83 and 0.97 respectively). Interestingly, mean plasma GH for six consecutive weeks in all the groups showed much greater GH concentration (group I, 86.6 +/- 9.7 ng/ml to group VI 33.2 +/- 5 ng/ml) than reported in other species. Mean basal plasma GH calculated in growing and adult mithuns was 29.6 +/- 4.01 ng/ml and around 25 +/- 3.6 ng/ml respectively. The GH peak (444 +/- 21.3 ng/ml) was registered at 15 min post-GHRH administration in growing mithuns. In conclusion, age and BW influence plasma GH and GH per 100 kg BW but the latter is a better indicator of growth. The basal plasma GH and GH response to GHRH administration is six to eight and four to five times higher in mithun than in other species reported so far. An accurate assessment of the relationship between GH profiles and protein metabolism, proper receptor level study for GH action at the cellular level and the interaction of GH with other growth factors awaits better understanding of higher GH in this unique species.     

日粮中添加高水平纳米硒对蛋鸡血硒含量及抗氧化能力的影响

选取288只42周龄健康农大3号商品蛋鸡,随机分为6个组,设4个重复,在基础日粮中以亚硒酸钠的形式添加硒0.3mg/kg为对照组;其余各组以纳米硒的形式分别添加硒0.3、0.5、2.5、5.0mg/kg和10.0mg/kg。试验期为60d。结果表明:日粮中添加2.5～10.0mg/kg纳米硒能显著提高全血硒的含量(P0.05)。试验至30d,日粮中添加10.0mg/kg纳米硒显著提高血浆T-AOC活性;日粮添加0.3～10.0mg/kg纳米硒能显著降低血浆MDA和血浆NO含量(P0.05)。试验至60d,添加5、10.0mg/kg纳米硒能显著降低GSH-Px活性,添加2.5～10.0mg/kg显著提高NO含量(P0.05)。综上所述,蛋鸡日粮中添加纳米硒至2.5mg/kg是安全的。     

Ovine white-liver disease (OWLD). Botanical and chemical composition of pasture grass

The most important grass species on the ovine white-liver disease (OWLD) pastures (S) were Poa spp., Agropyron repens and Lolium perenne, while the control pastures (H), where lambs grew well, consisted of Poa spp., Festuca rubra and Agrostis tenuis. The soil was more acidic on the H pastures as compared with the S pastures. OWLD grass (S grass) contained marginal to deficient amounts of cobalt during the first 2 months of grazing. During 2 years out of 3, the average Co content was slightly lower in the S grass as compared with the content in the H grass. The lowest average grass Co was, however, found during one year in the H grass, in spite of the fact that the H lambs also this year grew well, and were 13 kg heavier than the S lambs after 3 1/2 months on pasture. Results thus indicate that the H lambs some years were subclinically Co deficient, without developing clinical symptoms or OWLD, and that factors other than marginal/deficient grass Co are of importance as to whether OWLD will develop or not. S grass differed from H grass by having significantly lower copper, molybdenum, manganese and zinc content, lower protein N/amid N ratios and higher aluminium and iron contents. According to the results, marginal to deficient grass Co is essential for development of OWLD, but cofactors play a part.     

Hepatic cobalt and copper levels in lambs in Norway

Cobalt and copper concentrations were measured in 599 lamb livers collected at slaughter from 58 sheep flocks in 6 different parts of Norway in 1993. Information about pasture, additional feeding and mineral supplements in the flocks was obtained through a questionnaire. Average hepatic levels of cobalt in the lamb flocks varied from < 0.003 to 0.22 microg/g ww, and of copper from 5 to 240 microg/g ww. Flocks with deficient or marginal cobalt status were found in all parts of southern Norway, but primarily in the west and south-west. Some flocks with marginal copper status were found in the south-west, while flocks with signs of excessive hepatic copper concentrations were found mainly in inner parts of central and northern Norway. Hepatic copper concentrations were significantly higher in lambs that had grazed mountain pastures than in those that had grazed lowland pastures in the summer.