Conditioned feed aversion as a means to prevent tulp (Homeria pallida) poisoning in cattle

Conditioned feed aversion was investigated as a means to prevent tulp (Homeria pallida) poisoning in cattle on tulp-infested grazing. Aversion treatment with a combination of epoxyscillirosidin and lithium chloride together with a tulp-hexane extract, which served as identification factor for tulp, resulted in a significantly lower (P < 0.001) proportion of severe tulp poisoning. In a first trial where 21 averted and 21 non-averted control cattle were exposed to a tulp-infested grass pasture, only two of the averted cattle were severely poisoned compared to 13 of the non-averted control cattle. In a second trial, with cattle being exposed to a pure stand of tulp supplemented with maize residues, only two of 21 averted cattle were severely poisoned compared to 14 of 21 non-averted control cattle. Occurrence of mild tulp poisoning, however, did not differ much between averted and non-averted control cattle. The results show that conditioned feed aversion effectively restricted severe poisoning in cattle on tulp-infested grazing.     

Effect of previous locoweed (Astragalus and Oxytropis species) intoxication on conditioned taste aversions in horses and sheep

Locoweed species (Astragalus and Oxytropis spp.) are a serious toxic plant problem for grazing livestock. Horses and sheep have been conditioned to avoid eating locoweed using the aversive agent LiCl. The objective of this study was to determine if previous locoweed intoxication affects food aversion learning in horses and sheep. Horses and sheep were divided into 3 treatment groups: control (not fed locoweed and not averted to a novel feed); locoweed-novel feed averted (fed locoweed and averted to a novel feed); and averted (not fed locoweed and averted to a novel feed). Animals in the locoweed-novel feed averted groups were fed locoweed during 2 periods of 21 and 14 d, respectively, with each feeding period followed by a 14-d recovery period. Animals were averted to a novel test feed at the end of the first locoweed-feeding period, and periodically evaluated for the strength and persistence of the aversion. During the first recovery period, locoweed-novel feed averted horses ate less (9.5% of amount offered) of the test feed than did control horses (99.8%) and did not generally differ from averted horses (0%). During recovery period 2, locoweed-novel feed averted horses (4.3%) differed (P = 0.001) in consumption (% of offered) of the test feed from controls (100%) and the averted group (0%). Locoweed-novel feed averted sheep differed (P = 0.001) from controls (14.4 vs. 99.5%, respectively, during recovery period 1), whereas locoweed-novel feed averted sheep did not differ (P > 0.50) from averted sheep (0.6%). During the second recovery period, control sheep (100%) differed (P < 0.05) from averted (0%) and locoweed-novel feed averted (12.2%) groups. Two intoxicated sheep (locoweed-novel feed averted) partially extinguished the aversion during the first recovery period, but an additional dose of LiCl restored the aversion. Two of 3 intoxicated horses had strong aversions that persisted without extinction; 1 horse in the locoweed-novel feed averted group had a weaker aversion. These findings suggest that horses and sheep previously intoxicated by locoweeds can form strong and persistent aversions to a novel feed, but in some animals, those aversions may not be as strong as in animals that were never intoxicated.     

Conditioning taste aversions to locoweed (Oxytropis sericea) in horses

Locoweed (Oxytropis sericea) is a serious poisoning problem for horses grazing on infested rangelands in the western United States. Our objectives were to determine 1) whether lithium chloride or apomorphine would condition aversions to palatable foods, and at what doses, and 2) whether horses could be averted to fresh locoweed in a pen and grazing situation. Apomorphine was not an acceptable aversive agent because at the dose required to condition an aversion (> or = 0.17 mg/kg BW), apomorphine induced unacceptable behavioral effects. Lithium chloride given via stomach tube at 190 mg/kg BW conditioned strong and persistent aversions to palatable feeds with minor signs of distress. Pen and grazing tests were conducted in Colorado to determine if horses could be averted to fresh locoweed. Pen tests indicated that most horses (5/6) were completely averted from locoweed. Treated horses ate 34 g of fresh locoweed compared to 135 g for controls (P < 0.01) during three pen tests when offered 150 g per test. One horse (T) in the treatment group ate locoweed each time it was offered in the pen, but ate no locoweed while grazing. In the grazing trial, control horses averaged 8.6% of bites of locoweed (P < 0.01) during the grazing portion of the study, whereas treated horses averaged <0.5%. One treated horse (S) accounted for all consumption; he consumed 15% of his bites as locoweed in a grazing bout on d 2 of the field study. Thereafter, he was dosed a second time with lithium chloride and ate no locoweed in the subsequent 5 d. Three of six horses required two pairings of lithium chloride with fresh locoweed to condition a complete aversion. The results of this study indicate that horses can be averted from locoweed using lithium chloride as an aversive agent, and this may provide a management tool to reduce the risk of intoxication for horses grazing locoweed-infested rangeland.     

Conditioning taste aversion to Mascagnia rigida (Malpighiaceae) in sheep

The objective of this study was to determine if sheep could be averted to Mascagnia rigida, a toxic plant found in the semiarid region of northeastern Brazil. Twelve female sheep naïve to M. rigida were randomly allocated to two treatment groups: control (treated with 15 mL water orally by a drenching gun) and lithium group (treated with 150 mg LiCl/kg body weight orally by a drenching gun). For conditioning, sheep were allowed to feed on M. rigida leaves for 15 min, followed by LiCl or water administration. The time spent eating M. rigida leaves was measured. The conditioning was repeated daily until the LiCl-treated sheep stopped eating M. rigida, which occurred at days 2 and 3. Persistence trials were conducted on day 10, 24, 40, 55, and 70 of the trial using single-choice tests. There was no difference between the two treatment groups with respect to the consumption of M. rigida on the first day of aversion conditioning. On the second day, three out of the six sheep in the lithium group did not eat the leaves, but on the third day, all the sheep in the lithium group did not ingest M. rigida. This aversion persisted throughout all the persistence trials. This indicates that sheep can be easily conditioned by using lithium chloride to avoid eating M. rigida.     

Adverse influence of social facilitation and learning context in training cattle to avoid eating larkspur

Through conditioned food aversion learning, livestock can be trained to avoid eating harmful plants. The objectives of this study were to determine whether social facilitation will extinguish an aversion to larkspur (a poisonous plant on mountain rangelands) and to determine whether the aversion can be reinforced to withstand social facilitation in a group-feeding and field-grazing situation. Two groups of heifers offered fresh larkspur were simultaneously infused intraruminally with lithium chloride (LiCl) to create an association between the taste of larkspur and LiCl-induced gastrointestinal distress. A third control group was infused with water. Heifers from one averted group (extinction) were paired with nonaverted controls and offered larkspur. When the extinction group sampled larkspur, and LiCl was not infused, the aversion was extinguished rapidly. Heifers in the other averted group (reinforcement), being infused with LiCl whenever they sampled larkspur, abstained from eating larkspur in the group-feeding situation. Heifers were then taken to larkspur-infested rangeland. After the control heifers began eating larkspur, the averted heifers started to sample it and the aversion was extinguished in three of four heifers. However, the aversion was renewed when the heifers were returned to the pen- and group-feeding situation where the aversion was created. Reinforced aversion was overcome by social facilitation in an unfamiliar field-grazing environment.     

Degrees of aversion shown by rats and mice to different concentrations of inhalational anaesthetics

The distress associated with the induction of anaesthesia with halothane, isoflurane, enflurane and carbon dioxide was investigated in rats and mice by measuring the level of aversion they displayed on exposure to low, medium and high concentrations of these agents. The animals were exposed to each agent in a test chamber containing air or gas mixtures, which they were able to enter and leave at will, and the level of aversion was assessed in terms of the initial withdrawal and total dwelling times in the chamber. Comparisons between the anaesthetic and air-control treatments indicated that concentrations of the agents recommended for the rapid and efficient induction of anaesthesia were associated with some degree of aversion. Carbon dioxide was by far the most aversive gas for both rats and mice, with the least aversive being halothane for rats, and halothane and enflurane for mice. With all the anaesthetics, the level of aversion increased as the concentration increased.     

The avoidance of ammonia by sheep

The avoidance of ammonia by sheep was tested using operant conditioning techniques, training 12 sheep to operate a lever to open a door that would allow them to traverse a chamber with or without ammonia and obtain a food reward. One half of the sheep had been previously exposed to ammonia at 45 ppm in a simulated ship voyage, and the other half were kept in identical conditions but without ammonia. The maximum number of lever presses, or breakpoint, achieved when the chamber contained 45-ppm ammonia was compared with the number when the chamber contained no ammonia. There was a significantly lower mean breakpoint when the sheep traversed the chamber filled with ammonia (mean: 4.2 presses), compared with the chamber filled with fresh air (mean: 6.6 presses), demonstrating that sheep exhibited a moderate aversion to 45-ppm ammonia. Although the scale of the reduction in mean breakpoint was considerable, the aversion was only clearly demonstrated in 75% of the sheep, and there was no evidence that prior exposure influenced this aversion. It is therefore concluded that sheep show a moderate aversion to 45-ppm ammonia, with no evidence of sensitivity being affected by previous exposures.     

Feed Intake and Performance of Sheep Grazing Semiarid Grassland in Response to Different Grazing Systems

Effects of grazing management systems (GS) on biomass production and nutritional quality of rangeland vegetation in semiarid regions are extensively studied; however, limited information is available regarding their effects on diet digestibility and feed intake of grazing livestock. We therefore analyzed digestibility of ingested organic matter (dOM), organic matter intake (OMI), and live weight gain (LWG) of sheep in a grazing experiment established in the Inner Mongolian steppe of China, where two GS were tested for six different grazing intensities (GI) from very light to heavy grazing. For the continuous grazing system, sheep grazed the same plots each year, and for the alternating system, grazing and hay making were alternated annually between two adjacent plots. In July, August, and September 2009 and 2010, feed intake and live weight of sheep were determined. The GS did not affect dOM (P = 0.101), OMI (P = 0.381), and LWG of sheep (P = 0.701). Across both GS LWG decreased from 98 g · d^-1 for GI1 to 62 g · d^-1 for GI6 (P &spilt; 0.001; R² = 0.42). There were no interactions between GS and GI for all measured parameters (P ≥ 0.061), indicating that alternating grazing did not compensate for negative effects of heavy grazing even after 4 yr of grassland use. In summary, our study showed that irrespective of GI, alternating grassland use does not improve dOM, OMI, and hence, LWG of sheep. However, it might enhance revenues and ecological sustainability in the long term when compared to the common practice of continuous grazing at very high stocking rates.     

不同类型藏羊消化率与采食量的比较研究

采食量是放牧家畜生产性能的重要影响因素,在草地生态系统中起重要作用。夏季在甘南夏河分别选取不同生理类群(羔羊、1岁母羊、2岁母羊、3岁母羊、4岁母羊、羯羊和种公羊)的欧拉型、甘加型和乔科型藏羊各4只进行试验。采用二氧化钛指示剂法与粪氮指数法分别测定藏羊排粪量和牧草有机物质消化率,从而计算放牧采食量,并对特征间的相关性进行研究。结果表明:欧拉型、乔科型和甘加型藏羊的平均放牧采食量分别为1031.93、834.59和956.15 g·d^-1,乔科型藏羊放牧采食量显著(P<0.05)小于欧拉型和甘加型藏羊。3个类型藏羊的每kg代谢体重采食量和干物质采食量占体重比差异均不显著(P>0.05)。欧拉型、乔科型和甘加型藏羊对夏河天然草地牧草的平均有机物质消化率分别为50.79%、47.22%和55.58%。欧拉型、乔科型和甘加型藏羊的平均排粪量分别为561.26、484.06和466.74 g·d^-1,其中欧拉型藏羊的排粪量显著高于其他两个类型。试验在高寒地区天然草地研究不同类型藏羊的排粪量、有机物质消化率和放牧采食量,旨在为该地区放牧藏羊的科学饲养与管理提供理论依据。     

Effect of electric field in conditioned aversion response

The aim of the present study was to estimate whether rat sense exogenous electric field (EF) including one used in our previous studies. Employing a conditioned place aversion response paradigm based on an aversive behavior against light environment, alteration in both voluntary behavior of Wistar rat to a 50 Hz sinusoidal EF was examined. Following conditioning without EF, the times spent in white place in rats was significantly shortened (P<0.05). While, such changes were not shown in rats conditioned with EF. Thus, it was considered that the aversion response to light environment was interfered by exposure to EF. An interference in recognition of brightness via EF induced effect to visual system or in learning system via direct effect to central nerve system was considerable as a factor for EF-induced effect. In addition, it was remained that rat possibly sense exposure to EF as preferable. In order to confirm which factor functioned, further studies are needed.     

牦牛和藏羊混合放牧对放牧家畜采食量和植物补偿性生长的影响

为探究放牧方式对青藏高原高寒草地家畜的采食量和植物补偿生长的影响,本试验在环青海湖流域高寒草地设置放牧方式（牦牛单独放牧、藏羊单独放牧、牦牛和藏羊1：2混牧、牦牛和藏羊1：4混牧、牦牛和藏羊1：6混牧）控制试验,以期确定草地的承载力,并为制定合理的草地管理措施提供依据。试验结果表明：在群落水平上,家畜的采食量在藏羊（Ovis aries）单独放牧以及牦牛（Bos grunniens）与藏羊1：2混牧方式下,显著高于其他方式（P<0.05）;在功能群水平上,藏羊单独放牧与牦牛和藏羊1：2混牧这2种放牧方式下家畜对豆科植物的采食量较高;藏羊单独放牧与牦牛和藏羊1：2混牧植物的补偿生长能力显著高于其他放牧方式（P<0.05）。研究表明：藏羊单独放牧时,其采食量最高;牦牛和藏羊1：2混牧的放牧方式对植物补偿性生长的促进作用最明显。因此,从放牧家畜采食量与植物补偿生长两方面考虑,在青藏高原高寒草地藏羊单独放牧与牦牛和藏羊1：2混牧的放牧方式较为合理。     

不同放牧强度对绵羊生产性能的影响

就近几十年来放牧强度对绵羊放牧行为、采食植物组成和生产性能的影响进行了综述,得出结论:①绵羊的个体增重与放牧率之间呈线形负相关,而公顷增重与放牧率之间呈正相关。②绵羊的采食量随着放牧强度的加重而降低。③放牧强度对母羊繁殖性能各指标影响差异不显著。④随着放牧强度的加重,绵羊的采食时间增加,游走、反刍卧息时间减少;每百口采食量和日采食量减少,而采食速度增加。⑤放牧绵羊的嗜食性是相对的。⑥轻牧有利于提高肉的品质,但是产肉量低,总的经济效益不高。     

藏北紫花针茅高寒草原适宜放牧率研究

通过5年的放牧试验研究了藏北紫花针茅高寒草原地上现存量和草地净初级生产力以及藏系绵羊采食量和采食率,以期能够准确制定藏北高寒草原适宜放牧率。研究结果表明,试验初期放牧强度对藏北紫花针茅高寒草地现存量的影响并不显著;随着试验后期对放牧强度增倍,草地地上现存量随放牧强度增加而减少。放牧样地地上净初级生产力在试验初期高于对照样地,但随着放牧强度和时间的增加,到2010年时对照样地净初级生产力明显高于放牧处理(P<0.05)。绵羊采食量与放牧强度间存在显著负相关(P<0.05);绵羊采食率大小顺序为:重牧>轻牧>中牧。综合分析试验结果,轻度放牧条件下,不仅草地现存量和净初级生产力最大,并且绵羊采食量也为最大,因此建议在牧草生长季内藏北紫花针茅高寒草原放牧率应低于4只/1.67 hm²为宜。     

差额法和粪氮指数法对估测放牧绵羊采食量的影响研究

为评价放牧绵羊采食量,采用控制放牧试验,设置5个放牧处理,比较了差额法和粪氮指数法测定放牧绵羊采食量的结果。结果表明:绵羊采食量随放牧强度的增大而减小,春季休牧能显著提高绵羊的采食量(P <0.05)。其中用差额法测定的最高采食量为34.8 g·d^-1·kg^-1,粪氮指数法测得的最高采食量为46.4 g·d^-1kg^-1。2种测定方法测定结果具有相同的趋势,粪氮指数法的测定结果显著高于差额法(P <0.05)。差额法测定的采食量和粪氮指数法测定的采食量间成指数相关,方程为y=1.1577e^0.0628x(R²=0.677)。     

A stochastic exposure assessment model to estimate vanadium intake by beef cattle used as sentinels for the South African vanadium mining industry

This paper presents an environmental exposure assessment model for estimating chronic intake of vanadium (a transition metal) by cattle farmed extensively in areas contaminated by vanadium pollutants. The exposure model differs from most other models in several ways: (1) it does not rely heavily on extrapolating information from the point source (e.g. stack height, exit velocity, exit diameter) to the point of exposure. (2) It incorporates the physiological constraints of the species exposed. (3) It takes into account oral as well as inhalation exposure. (4) It addresses terrain, by using measurements at the point of exposure. (5) It accounts for existing background concentrations of pollutants and pollutants from multiple sources. (6) It uses a stochastic process with distribution functions to account for variability in the data over time. Environmental inputs into the model included aerial fall-out sample vanadium (n = 566), unwashed grass sample vanadium (n = 342) and soluble soil sample vanadium (n = 342). Physiological cattle inputs were derived from two cohorts of Brahman-cross sentinel cattle (n = 30). The model provided an estimate of the chronic external exposure dose of vanadium for two separate groups of cattle grazing over a 5-year period (1999–2004) immediately adjacent (median dose = 2.14 mg vanadium/kg body weight/day) and 2 km away (median dose = 1.07 mg/kg/day) from a South African vanadium-processing plant, respectively. The final output of the model is a distribution curve of the probable vanadium intake based on the variability within the inputs over the 5-year period of the study. The model is adaptable enough for application to other transition metals and species (including man), and could be used as an alternative to plume-dispersion modelling.     

链烷技术估测典型草原不同放牧率绵羊食性食量方法研究

为了进一步探讨饱和链烷技术在典型草原自由放牧家畜中的应用,定量研究自由放牧绵羊食性及食量,于2004年6-9月在中国科学院内蒙古草原生态系统定位研究站放牧样地进行试验,选择体重及体况相近、健康无病的二岁羯羊(内蒙古细毛羊×蒙古羊)60只,按体重(36.9±2.6) kg聚类分组,设置6种放牧率(0,1.33,2.67,4.00,5.33和6.67羊/hm²)的轮牧实验,绵羊采食量的测定选择放牧率为1.33,4.00和6.67羊/hm²的处理,试验开始,每只羊投喂1粒QSM饱和链烷缓释胶囊。食性测定选用全部的放牧率进行,同时辅助全粪法、扣笼法一同评价。试验期内定期收集试验地牧草样品及绵羊粪便样品,使用气相色谱分析牧草和粪样中的链烷含量,应用链烷技术估测放牧绵羊的排粪量、牧草采食比例和干物质采食量。结果表明,植物链烷模式存在种间差异,运用链烷技术估测的排粪量和实际测得排粪量差异不显著(P>0.05),放牧绵羊主要采食7~9种牧草,且不同放牧季节不同放牧率绵羊采食的牧草种类和比例不同,但采食量差异不显著(P>0.05)。本研究表明,运用链烷技术结合扣笼方法可以估测天然草地自由放牧家畜牧草的采食比例、干物质采食量和排粪量。     

放牧绵羊行为生态学研究：Ⅲ不同放牧时期对放牧绵羊牧食行为的影响

在较低放牧率和限牧时间条件下，不同放牧时期对绵羊牧食行为的影响有：（１）当放牧时间缩短时，绵羊通过缩短反刍行为的时间而保持采食时间的相对稳定，并通过调整各采参数数以保持进食速率和日采食量的相对稳定，对饮水行为影响不大；（２）９月份反刍周期数和总反刍食团数量少，反刍时间最短；６月份每个食团咀嚼次数最少，咀嚼时间最短；（３）７月份排尿次数量多，每次排尿时间最长；９月份居中；６月份量少。排粪行淡差异不显     

Sheep Ingestion of Water Containing Quebracho or Black Wattle Tannin

Ingestion of small amounts of condensed tannin (CT) by ruminants can produce valuable outcomes such as improved nitrogen use and reduced bloating, methane output, and gastrointestinal parasitism. However, many grasses and forbs contain little if any CT. The specific types of CT vary in plants and can have somewhat different effects on ruminants. Individual ruminants can respond differently to CT intake. Not all livestock will consistently consume supplements while grazing, but they all usually drink water daily. Therefore, in order to determine how sheep would respond to CT in their drinking water, eight lambs with the same initial weight of 43 kg were individually penned, fed alfalfa pellets twice daily, and had ad libitum access to two waters. Water intake was measured daily. After an adjustment period to pens, feeding, watering conditions, and water containing CT, three sequential week-long trials were conducted. In Trial 1, lambs chose between tap water and a quebracho tannin (QT)–water mixture (0.19% QT w/w; ca. 1% dry matter intake of QT). In Trial 2, lambs chose between tap water and a QT–water mixture of lower concentration (0.14% QT w/w). In Trial 3, lambs chose between a QT–water mixture and a wattle tannin–water mixture, both with the same concentration (0.14% CT w/w). In Trials 1 and 2, lambs had inconsistent intakes of tannin water and tap water from day to day (P ≤ 0.02) and neither preferred nor avoided tannin solutions. They also had inconsistent daily intakes of the two different tannin solutions offered simultaneously (P = 0.01), and showed no preference for either tannin solution (P ≥ 0.15). Results support other observations that sheep will voluntarily consume water with small amounts of CT in it, and provide no evidence that sheep prefer consuming small amounts of QT vs. black wattle tannin in water.     

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。     

高山草原绵羊放牧生态及消化代谢系列研究

应用灰色系统理论中的灰色关联度分析法对影响高山草原牧草营养的季节性与放牧绵羊消化代谢和生产性能动态关系的18种主要限制性因素进行了研究。关联度分析结果表明：牧草代谢能浓度是影响放牧绵羊采食量的主要因素；影响放牧绵羊日增重的主要因素是大气温度和饲养粗蛋白质含量；羊毛生长速度限制性因素是饲草粗蛋白质水平，气温对羊毛的生长速度影响较小；瘤胃氨氮量是影响粗蛋白质存留率的主要因素，气温影响次之。