桑螟食叶量测定及其防治指标的研究

通过对桑螟食叶量测定和发育历期的调查 ,明确了桑螟在 2 5℃恒温条件下的幼虫历期为 12～ 13d ,幼虫一生鲜叶食下量为 4 15mg ,其中 4、5龄的食叶量约占全龄食叶量的 82 3% ,据此可确定桑螟的防治指标和防治适期。经测算 ,桑螟春夏季的防治指标为 2 4 0 0 0～ 30 0 0 0头 /hm2 ,秋季的防治指标为 36 0 0 0～ 6 0 0 0 0头 /hm2 ;而农药防治的最佳时期应掌握在 3龄卷叶前为宜。     

桑螟食叶量测定及其防治指标的研究

测定了桑螟幼虫一生的食桑量,以及食下量与发育历期的关系,为确定桑螟的防治适期及防治指标提供了科学依据。经过分析得出:桑螟的防治最佳时期应该为3龄以前;春夏季的防治指标为1200～1600头/亩,秋季的防治指标为1800～3200头/亩。     

康宽对大蜡螟不同龄期幼虫的毒力测定

为有效防控中华蜜蜂害虫大蜡螟,指导科学用药,本文采用胃毒法分别测定了康宽(20%氯虫苯甲酰胺)对大蜡螟1龄幼虫、4龄幼虫和6龄幼虫的毒力。结果表明,用药72h后,康宽对大蜡螟不同龄期幼虫的毒力大小顺序依次为:1龄幼虫>4龄幼虫>6龄幼虫;其致死中浓度(LC_(50))分别为2.430mg/L、5.661mg/L和40.071mg/L。本研究可为大蜡螟的应急绿色防控提供科学指导,建议生产上在大蜡螟低龄幼虫期时进行防治。     

意大利蜜蜂工蜂幼虫饲粮的适宜赖氨酸水平

本试验旨在研究意大利蜜蜂工蜂幼虫饲粮的适宜赖氨酸水平,为探明意大利蜜蜂工蜂幼虫发育阶段的赖氨酸营养需要提供理论依据。选用1日龄意大利蜜蜂工蜂幼虫1 200只,随机分为5个组,每个组5个重复,每个重复48只。5组工蜂幼虫分别饲喂赖氨酸实测水平为6.08(对照)、11.08、16.08、21.08和26.08 mg/g的饲粮,饲养至幼蜂羽化出房。分别于特定日龄测定工蜂幼虫化蛹率(6日龄)、虫体总蛋白含量(6日龄)、羽化率(21日龄)等生长指标以及血淋巴生化指标和免疫相关指标(6日龄)。结果表明:1)11.08 mg/g赖氨酸组的工蜂幼虫化蛹率和羽化率极显著高于其他各组(P0.01)。2)与对照组相比,11.08~26.08 mg/g赖氨酸组6日龄工蜂幼虫虫体总蛋白含量和血淋巴中游离赖氨酸含量显著提高(P0.05),其中饲粮赖氨酸水平为26.08 mg/g时6日龄工蜂幼虫虫体总蛋白含量和血淋巴中游离赖氨酸含量最高。3)6日龄工蜂幼虫血淋巴中甘油三酯含量随饲粮赖氨酸水平的升高呈先下降后上升的趋势,其中饲粮赖氨酸水平为16.08 mg/g时处于最低值,极显著低于其他各组(P0.01)。4)11.08~21.08 mg/g赖氨酸组6日龄工蜂幼虫血淋巴中溶菌酶活性显著高于对照组(P0.05),但随着饲粮赖氨酸水平由21.08 mg/g升高到26.08 mg/g,6日龄工蜂幼虫血淋巴中溶菌酶活性急剧下降,26.08 mg/g赖氨酸组显著低于其他各组(P0.05)。5)饲粮赖氨酸水平为11.08 mg/g时,6日龄工蜂幼虫虫体溶菌酶基因的相对表达量最高,显著高于其他赖氨酸水平时(P0.05)。与对照组相比,11.08~16.08 mg/g赖氨酸组6日龄工蜂幼虫虫体防卫素1基因的相对表达量显著增加(P0.05)。由此得出,赖氨酸能够促进意大利蜜蜂工蜂幼虫生长,促进蛋白质和赖氨酸的沉积,提高羽化率,并在一定程度上对脂质代谢和幼虫免疫能力产生调节作用;综合考虑上述指标,推荐意大利蜜蜂工蜂幼虫饲粮的适宜赖氨酸水平为11.08~16.08 mg/g。     

寄主植物对沙葱萤叶甲幼虫生长发育及取食的影响

沙葱萤叶甲（Galerucadaurica Joannis）为近年来严重危害内蒙古草原的重要害虫,为揭示其成灾机制,在室内测定了13种内蒙古草原常见牧草对沙葱萤叶甲幼虫生长发育、存活和取食的影响。结果表明：沙葱萤叶甲幼虫食性窄,主要取食沙葱（Allium mongolium）、野韭（A.ramosum）及多根葱（A.polyrhizum）等百合科葱属植物,其他供试植物基本无取食现象。沙葱、野韭及多根葱对沙葱萤叶甲幼虫期、蛹期和取食量有显著影响,而对其存活率影响不显著。幼虫取食沙葱、野韭和多根葱时,幼虫期和蛹期分别为24.27,27.87,33.13d和6.61,7.40,8.43d,取食量分别为393.76,442.51和496.09mg（鲜重）,3龄幼虫食量最大,占幼虫期总食量的63.45%~67.46%,约为2龄幼虫的3倍、1龄幼虫的5倍。因此,沙葱是沙葱萤叶甲幼虫的最适寄主植物,其次为野韭,然后是多根葱;化学防治时,应在幼虫3龄以前进行。     

敌敌畏、乐果对不同龄期柞蚕幼虫的急性毒性研究

为探究敌敌畏、乐果对不同龄期柞蚕幼虫的急性毒性，采用食下毒叶法喂食不同龄期的柞蚕幼虫，连续观察96 h,分时间段测定敌敌畏、乐果对柞蚕幼虫的半数致死浓度(LC₅₀);通过熏蒸毒性试验，连续观察72 h,记录对不同龄期柞蚕幼虫的熏蒸毒性，利用SPSS软件，建立模型方程，计算出敌敌畏、乐果对不同龄期柞蚕幼虫的LC₅₀及置信区间。结果显示，2种农药毒性相比，敌敌畏高于乐果。敌敌畏对5龄柞蚕幼虫的24 h LC₅₀最高达到277.159 mg/L,对1龄柞蚕幼虫的96 h LC₅₀最低为0.161 mg/L,对1、2龄柞蚕幼虫的毒性为剧毒，对其它龄期柞蚕幼虫的毒性为高毒；乐果对5龄柞蚕幼虫的24 h LC₅₀最高达到391 858.000 mg/L,对1龄柞蚕幼虫的96 h LC₅₀最低为0.652 mg/L,对1龄柞蚕幼虫的毒性为剧毒，对其它龄期柞蚕幼虫的毒性为中毒或低毒。敌敌畏对柞蚕幼虫的熏蒸毒性为高风险，乐果对柞蚕幼虫也有一定的熏蒸毒性。     

意大利蜜蜂工蜂幼虫饲粮中适宜泛酸水平

本研究旨在探索饲粮中泛酸水平对意大利工蜂蜜蜂幼虫发育、机体抗氧化能力及辅酶A(Co A)合成相关酶基因表达的影响,以期得到蜜蜂幼虫阶段饲粮中泛酸的适宜水平。试验选取1日龄意大利蜜蜂工蜂幼虫1 800只,随机分为5组,每组3个重复,每个重复120只。5组工蜂幼虫分别饲喂泛酸实测水平为0.92(对照)、1.22、1.52、1.82、2.12 mg/g的试验饲粮,饲喂至化蛹。分别取5日龄和7日龄幼虫测定体重、体成分、血淋巴生化指标、抗氧化指标、Co A合成相关酶基因的相对表达量,并计算幼虫的化蛹率和羽化率。结果表明:1)饲粮中添加泛酸可显著提高虫体鲜重、干重以及粗脂肪含量(P0.05);当泛酸水平为2.12 mg/g时,幼虫的羽化率显著高于其他组(P0.05)。2)饲粮中泛酸水平对5日龄工蜂幼虫血淋巴中总蛋白(TP)、总胆固醇(TCHO)、高密度脂蛋白(HDL)、低密度脂蛋白(LDL)含量有显著影响(P0.05),且分别在1.82、1.82、1.22、1.52 mg/g组含量最低。3)5日龄和7日龄虫体总抗氧化能力(T-AOC)以及5日龄虫体超氧化物歧化酶(SOD)活性随饲粮泛酸水平的升高而显著升高(P0.05)。4)饲粮泛酸水平显著影响5日龄幼虫泛酸激酶4基因和磷酸泛酰-半胱氨酸脱羧酶基因的相对表达量(P0.05),且均在泛酸水平为1.82 mg/g时相对表达量最高。分别以5日龄虫体的干重和羽化率作拟合曲线,获得意大利蜜蜂工蜂幼虫饲粮中适宜的泛酸水平为1.85~2.01 mg/g。     

杀虫剂呋喃虫酰肼对家蚕的毒性试验

呋喃虫酰肼是具有类似蜕皮激素作用的昆虫生长调节剂类杀虫剂。为了明确呋喃虫酰肼用于大田害虫防治后对农业生态环境中家蚕安全性的影响,进行了该杀虫剂对家蚕的毒性试验。结果表明,50~1 000 mg/L呋喃虫酰肼药液对家蚕3龄幼虫无熏蒸毒性,但有一定触杀毒性和强烈的胃毒作用。采用食下毒叶法添食呋喃虫酰肼药剂,对2龄起蚕的48 h LC50值为142.095μg/L;对4龄起蚕6 h、24 h的LC50值分别为1.284 mg/L、0.274 mg/L;对5龄起蚕的6 h、24 h的LC50值分别为9.180 mg/L、1.431 mg/L。用LC10以下浓度的呋喃虫酰肼药液给3龄、4龄家蚕幼虫添食后,幼虫未出现蜕皮症状,熟蚕的上蔟时间也未改变。桑树喷洒100 mg/L呋喃虫酰肼药液至湿润,喷药后68 d时采摘桑叶连续24 h饲喂5龄起蚕仍会导致其全部中毒,头胸部出现与眠蚕相似的三角区,部分中毒幼虫的表皮剥落。由于呋喃虫酰肼对家蚕具有强烈的胃毒作用,且在桑叶中的残效期很长,因此该杀虫剂不能用于蚕区及周围的大田与森林害虫防治。     

晶绿福(牛至油)与抗生素对仔猪生产性能的影响

将168头7千克左右断奶小猪(21日龄)分为7组,每组8头,每组设3个重复,进行添加晶绿福与抗生素对仔猪生产性能的对比试验。其中1组为“晶绿福—3000”300 mg/kg,2组为利高霉素1000mg/kg,3组为(酒石酸)泰乐菌素100mg/kg,4组为效美素200mg/kg,5组为硫酸新霉素250mg/kg,6组为抗敌素200mg/kg,7组为空白对照组。试验结果表明:1～6组的日增重、采食量和料肉比均不存在显著性差异(P>0.05)。腹泻率:6组与其它各组均存在显著性差异(P>0.05);从综合指标上看,以1组(“晶绿福—3000”300mg/kg)为最佳。     

红胫戟纹蝗损害牧草及其防治指标的评定

1994年4～8月进行红胫戟纹蝗虫损害牧草及防治指标的评定。结果表明,红胫戟纹蝗的体重、食量和牧草掉落毁损量三者之间呈正相关。红胫戟纹蝗个体一生的牧草损失量为:L＝1.4039g/头。红胫戟纹蝗在荒漠、半荒漠草原的防治指标为:×8头/m²。     

Harmful and economic thresholds for rodent pests in the Alxa desert area under different grassland utilization patterns北大核心CSCD

The rodent damage threshold and the rodent economic threshold are indicators that must be clearly defined in the practice of grassland rodent prevention and control. Different grassland types or different utilization methods of the same grassland type have completely different values for these two indicators. The damage threshold is the population density of pests at which the grassland is obviously compromised, and the economic threshold is the population density at which further pest population increases will cause economic losses. The Alxa desert region is ecologically fragile, and rodents are endemic. This study selected continuous grazing areas and prohibited grazing areas in the desert area of Alxa Left Banner and from 2015 to 2019 to investigated the species and density of pests using the ‘mark and recapture’ method, together with sampling to investigate the aboveground plant biomass in the sample area in August. The measured rodent unit densities and their daily food intakes were used to estimate the amount of forage loss, and a regression equation was used to obtain a fitted relationship between the rodent density and the ratio of forage loss. It was found that: 1) The fitted curves for the ratio of pest density and forage loss in the continuous and prohibited grazing areas took the form of logistic three-parameter, S-shaped curves. 2) According to the regression equation, the damage threshold in continuous grazing areas was 26 standard rodent units·ha-1 and the economic threshold was 39.3 standard rodent units·ha-1. In prohibited grazing areas, the damage threshold was 33.2 standard rodent units·ha-1 and the economic threshold was 30.2 standard rodent units·ha-1. Thus, the economic threshold pest density of continuous grazing areas was slightly higher than that of prohibiting grazing areas. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Long-term supplementation of lasalocid-sodium for beef bulls during grazing and subsequent finishing period

117 white-red beef bulls were involved to investigate the effect of lasalocid-sodium when fed either during the grazing period, or the finishing period, or during both subsequent periods. The ionophore was fed at 250 mg daily per head incorporated in 1 kg dry sugar beet pulp on pasture and at 65 mg per kg concentrate afterwards (corresponding with 27 ppm in the ration DM). The finishing diet consisted of maize silage ad libitum and 0.75 kg concentrate per 100 kg liveweight per day. On pasture lasalocid significantly increased daily gain form 0.6 to more than 0.7 kg, without affecting the grazed area per animal. During the finishing period growth rate was only slightly affected by lasalocid, but feed intake was reduced (P less than 0.05) and feed conversion improved (P less than 0.05). Feeding lasalocid permanently for more than 400 days did not reduce these positive effects. Cumulative daily gain, total feed intake per head and feed conversion were 1.12 kg, 2176 kg dry matter (DM) and 4.70 kg DM. These figures amounted to 1.05 kg, 2283 kg DM and 5.16 kg DM when no lasalocid was fed; 1.06 kg, 2141 kg DM and 4.87 kg DM when lasalocid was only fed during the finishing period and 1.09 kg, 2246 DM and 4.99 kg DM when lasalocid was only fed during the grazing period. Daily gains of 1.05 and 1.06 kg were significantly lower (P less than 0.05) than 1.12 kg. Most carcass data were unaffected, except fatness. The permanent feeding of lasalocid increased carcass fatness, mainly as the result of a higher final weight.     

Assessment of the effect of gastrointestinal nematode infestation on weight gain in grazing beef cattle

OBJECTIVE: To assess the effect of subclinical, naturally acquired gastrointestinal nematode infestation on weight gain in yearling cattle kept on pasture. DESIGN: Prospective study. ANIMALS: 799 Bos taurus yearlings kept on pasture with 2,805 herd mates in eastern and central South Dakota. PROCEDURE: 11 trials were initiated at 9 sites from 1999 through 2001. For each trial, approximately 10% of cattle in each site's pasture group were identified, weighed, and administered a bolus of ivermectin (sustained-release formulation) prior to turnout. A similar subgroup of nontreated control cattle was identified and weighed prior to turnout. For each trial, treated and control groups remained with the larger pasture group throughout the entire grazing season. At the end of the grazing season, weight measurements and fecal samples were obtained from all treated and control cattle; average daily grazing gain was calculated and compared between these 2 groups. RESULTS: Treatment of grazing cattle with ivermectin increased average daily gain by 0.0459 +/- 0.01 kg/head/d (mean +/- SEM; 0.1 +/- 0.02 lb/head/d), compared with that achieved in control cattle. Control cattle had significantly greater fecal egg counts at grazing season end than treated cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with anthelmintic-treated cattle, yearling cattle with naturally occurring gastrointestinal nematode infestations kept on pasture in the US Northern Plains had a decreased average daily gain equivalent to 6.6 kg (14.5 lb) less gain in a 143-day grazing season. Strategies for control of nematode populations in pastures should be considered to ameliorate this production loss.     

Long-term cattle gain responses to stocking rate and grazing systems in northern mixed-grass prairie

The effects of stocking rate and grazing system on gains of yearling beef cattle grazing rangelands have largely been addressed in short-term (< 10 years) studies, and often stocking rates are confounded within grazing systems with higher stocking rates for short-duration rotational grazing systems compared to season-long grazing. A grazing system (season-long and short-duration rotational grazing) × stocking rate (light: 16 steers/80 ha, 18.0 animal unit days/ha; moderate: 4 steers/12 ha, 30.1 animal unit days/ha; and heavy: 4 steers/9 ha, 40.1 animal unit days/ha) study was initiated in 1982 on northern mixed-grass prairie. Here, we report on the final 16 years (1991–2006) for yearling beef cattle gains. Average daily gains (kg/head/day) across all years with season-long grazing decreased with increasing stocking rate and grazing pressure. Heavy stocking rates reduced average daily gain by 16% and 12% compared to light and moderate stocking rates, respectively. In contrast to average daily gain, beef production (kg/ha) increased with increasing stocking rate and grazing pressure. Cattle gains were reduced by 6% with short-duration rotation compared to season-long grazing over the study period, with differences between systems observed in years with average, but not dry or wet, spring (April + May + June) precipitation. Grazing season gains (kg/head) and beef production both exhibited significant increasing hyperbolic relationships with spring precipitation, with the percentage of variation explained by spring precipitation substantially higher (62–83%) for beef production compared to grazing season gains (32–45%). The influence of spring precipitation on cattle gains suggests that incorporation of these relationships into modeling efforts for strategic planning and risk assessment will assist land managers in better matching forage and animal resources for greater sustainability in this highly variable environment.     

内蒙古典型草原三种家畜采食量和食性选择的研究

放牧家畜的采食量和对不同牧草的选食性是制定草地放牧管理的基本参数。本研究选取内蒙古典型草原,在相同放牧强度下比较绵羊、山羊和牛的采食量及牧草选择性。结果表明：在相同放牧强度下,夏秋季节放牧牛的平均日采食量为9.64 kg·（头·天）^-1,喜食大针茅、黄囊苔草和一些非优势种牧草（选食系数1 < SI≤1.5）,而对羊草和糙隐子草表现为可食（0.5 < SI≤1）;绵羊的平均日采食量为1.87 kg·（头·天）^-1,喜食羊草、黄囊苔草和其它非优势种牧草（1 < SI≤1.5）,而对大针茅和糙隐子草表现为可食（0.5 < SI≤1）;山羊的日均采食量为1.65 kg·（头·天）^-1,嗜食其它非优势种牧草（SI>1.5）,喜食黄囊苔草和糙隐子草（1 < SI≤1.5）,而对羊草和大针茅表现为可食（0.5 < SI≤1）。本研究意味着不同家畜或多种家畜混牧可更高效的利用草地资源,如放牧绵羊和牛可能分别减少羊草和针茅在草地中的丰度,因而采用不同家畜放牧或多种家畜混牧有利于草地的可持续利用。     

不同放牧强度对滩羊生产性能影响的研究

为寻找适宜宁夏盐池县草地的放牧强度,于2003年5-11月在该县四墩子试点设5个处理(0.45、0.60、1.75、1.05和1.50只/hm2)进行轮牧,轮牧周期为42 d,共放牧154 d。结果表明:1)滩羊采食量随放牧强度的加重而降低。同一放牧强度下,随放牧时间推移,采食量先逐渐增大而后下降。2)在试验期内,不同放牧强度下,滩羊体重随时间推移总体上都呈增加趋势。在10月2日之后体重开始出现分化。与放牧强度重的处理相比,放牧强度轻的处理日增重峰值较高,持续时间较长。3)滩羊个体增重与放牧强度之间存在着强的负相关;单位草地面积(1 hm2)增重与放牧强度之间呈强的正相关,初步可以确定在该类草地上放牧强度应在0.75只/hm2左右。4)随着放牧强度的加重,饲料报酬先增大后减小。在同一放牧强度下,饲料报酬随时间的推移先升高后降低。5)当放牧强度超过0.75只/hm2以后,滩羊出现了空怀、产羔率降低和推迟怀孕的现象。6)综合考虑各研究指标,该类草地放牧强度以不应超过0.75只/hm2为宜。     

Reducing phosphorus inputs for grazing Holstein steers

A 2-yr study was conducted to confirm that managed pastures can provide Holstein steers adequate P to meet their daily requirement. Treatments offered were trace mineralized salt with or without additional P. In the first year, 80 Holstein steers (248 kg of BW) were assigned to 4 grazing groups. Treatments were trace mineralized salt only or a 67:33 mixture of trace mineralized salt and dicalcium phosphate. Steers rotationally grazed a cool-season grass/legume mixture for 137 d. Fecal bags were placed on 3 steers from each grazing group (n = 12) over a 4-d period for estimation of forage DMI and forage contribution to daily P intake twice during the grazing season. Analyzed pasture samples contained 3.28 mg of P/g of DM. During the second year, 72 Holstein steers (297 kg of BW) were blocked into 2 BW groups and subsequently assigned to 1 of 4 pasture groups. Steers rotationally grazed the same forage base as the first year for 126 d. Pasture samples contained 3.27 mg of P/g of DM. No significant differences (P > 0.10) were detected for BW, ADG, or free-choice supplemental mineral intake. Forage provided 126% of the recommended NRC P requirement. Thus, supplemental phosphorous was not required for Holstein steers grazing mixed, cool-season, grass/legume pastures.     

Prophylaxis of trichostrongylid infection afforded by low-dose phenothiazine given in two successive years to first-season calves on a common area of pasture

Reduced trichostrongylid infection on herbage and in calves was obtained when first-season calves, grazing a common area of pasture, received low-dosage phenothiazine (PTZ) in two successive years. The average daily dose of PTZ was 7.0 or 10.3 mg kg-1 in the first year and, in the second, between 5.0 and 7.0 mg kg-1. The effect on herbage infection was attributed mainly to ovicidal action. Treatment increased weight gain by 22 and 50 to 60 per cent in the respective seasons. The results suggested a cumulative effect produced by treating calves of successive years. Two calves developed PTZ-induced photosensitivity (corneal opacity) in the first season, and two calves in the second season but in the latter, severe bronchopneumonia was believed to be a predisposing factor. To avoid photosensitivity and still maintain adequate drug activity, the daily intake of PTZ should probably be restricted to around 6 mg kg-1.     

棉茬地放牧对母羊繁殖性能及血液性状的影响

利用能繁母羊在棉茬地进行冬季放牧,探讨了棉茬地放牧对母羊繁殖性能及血液生化指标的影响。结果表明,棉茬地地上生物量为6 178.6 kg·hm-2,其中棉叶、棉桃壳等可采食部位约占65%。母羊的日均干物质采食量为1.98kg·只-1。与该区域舍饲母羊群相比,棉茬地放牧母羊后羔羊初生重偏低而死亡率高达12.87%,繁殖成活率降低(P0.05);随着放牧时间的推移,母羊血液游离棉酚浓度呈上升趋势,放牧结束时血液游离棉酚浓度达到131.70mg·L-1;放牧组母羊的血液中白细胞数量显著高于舍饲组(P0.05),而血小板数目、尿素氮浓度和镁浓度显著低于舍饲为主的母羊群(P0.05)。棉茬地作为冷季放牧利用地,能降低饲养成本,但对母羊的繁殖能力和健康有一定影响,建议在棉茬地放牧的同时进行适当补饲。     

放牧率对牦牛生产力的影响初析

通过2年的牦牛放牧试验,结果表明:放牧率对牦牛生产力有显著的影响,牦牛个体增重与放牧率呈线性回归关系;在试验期内,轻度放牧组的日增重较快,中度放牧次之,重度放牧最慢,而且随着放牧率的提高,牦牛平均个体总增重依次为136.7kg,128.6kg,93.5kg,轻度放牧比中度放牧和重度放牧分别高6.3%和46.2%。经方差分析表明,3个处理的牦牛平均个体增重有显著的差异(P<0.05),进一步作新复极差测验,30%和50%之间差异不显著,但他们和70%之间的差异均显著。