A Review of Equine Grazing Research Methodologies

Recently, there has been a renewed interest and an increase in published research on equine grazing and pasture management. The objectives of this paper are to review equine grazing research methodologies with an aim to encourage standardized research procedures. This review highlights standard methods used in equine pasture-related research, including use of climate data and soil type; seed bed preparation and grazing management; determining forage nutritive value; defining forage maturity; tracking horse health parameters; evaluating different grazing systems; and future technologies. This review covers in-depth discussions on determining forage biomass yield, forage populations, ground cover, persistence, forage intake, and grazing behavior. Specifically, mechanical harvesting, hand clipping, rising plate meter, and falling plate meter are all methods used to determine forage biomass yield. Frequency grid, point sampling, visual assessment, Natural Resources Conservation Service pasture condition score, and the double Dominant, Abundant, Frequent, Occasional, Rare (DAFOR) scale can be used to track forage populations, ground cover, and persistence of pasture species. Three primary methods have been used when estimating horse forage intake including the difference between pre- and postgrazing herbage mass, the difference in pre- and postgrazing bodyweight, and use of digestibility and fecal output markers. Equine grazing behavior has been described by investigating preference, pre- and post-sward height, and bite and mastication rate. Awareness of key methodologies should encourage movement toward research protocol standardization that will allow for scientific comparisons and application of pasture-related research results across the horse industry.     

不同放牧强度下人工草地土壤微生物量碳、氮的含量

试验测定了华北农牧交错带地区不同放牧强度下(轻牧,6只羊/hm²;中牧,10只/hm²;重牧,13只/hm²)人工草地土壤微生物量碳、氮含量的变化。结果表明:在不同放牧强度下,微生物量碳氮有相似的变化趋势,放牧期间均以中牧区较高,在停牧年,以轻牧区和对照区较高;随着放牧时间延长及环境条件恶化,土壤微生物量碳氮含量随放牧强度增加而迅速降低;从微生物量碳氮随放牧强度变化的角度,在干旱地区放牧强度不宜高于轻牧。     

Determination of Pasture Dry Matter Intake Rates in Different Seasons and Their Application in Grazing Management

Eight mature horses weighing 576 ± 32 kg (mean ± SD) were used to compare differences in pasture dry matter (DM) intake rate in October (period 1), February (period 2), and May (period 3). Horses were randomly assigned to a pair of adjacent 5 m × 5 m grazing cells containing nontoxic, endophyte-infected tall fescue. Horses had access to each cell for 4 hours. Pasture DM intake rate was estimated over the entire 8-hour period by measuring the pre- and postgrazing herbage mass within each cell and was expressed as kg DM/100 kg body weight (BW)/hr. Mean 8-hour DM intake rate in period 1 (0.17 ± 0.01 kg DM/100 kg BW/hr) was greater (P < .001) than for period 2 (0.09 ± 0.01 kg DM/100 kg BW/hr) and period 3 (0.11 ± 0.01 kg DM/100 kg BW/hr), but it was not different (P = .274) between periods 2 and 3. A second experiment using the same eight horses was conducted immediately after the first experiment, within each season, to determine whether the DM intake rates derived from the first experiment could be used along with estimates of maintenance digestible energy (DE) requirements and pasture DE concentrations to predict the amount of grazing time required for a horse to consume only its maintenance DE requirement and maintain zero BW change over a 6-week period. Grazing time necessary to maintain zero BW change was accurately predicted for period 1 only.     

放牧强度对南方人工草地和绵羊生产性能的影响(简报)

放牧强度对草地生存环境和家畜生产性能关系密切^[1]。我国对放牧强度的研究集中于北方^[2],南方草地建设比较晚,尤其是南方人工草地相关研究比较少。本试验旨在探讨南方人工草地不同放牧强度与草地植物产量和放牧家畜生产性能之间的关系,为确定合理的载牧量提供参考依据。     

Effect of Sward Height on Pasture Nonstructural Carbohydrate Concentrations and Blood Glucose/Insulin Profiles in Grazing Horses

Six mature stock-type geldings with maintenance only requirements were used in a randomized cross-over design to determine the effect of sward height on pasture plant nonstructural carbohydrate (NSC) concentrations and blood glucose and insulin concentrations. Horses were randomly assigned to one of two tall fescue (Lolium arundinaceum Schreb cv Max-Q, Pennington Seed, Madison, GA) grazing cells (0.37 ha) having two different sward heights for a period of 7 days: (1) short (approximately 15 cm; n = 3) or tall (between 30 and 40 cm; n = 3). After the first 7-day period, treatment groups were reversed by moving horses to ungrazed cells having similar characteristics to those used in the first 7 days, so that all horses receive all treatments resulting in six observations per treatment. Both short and tall grazing cells were mowed to a height of approximately 15 cm 32 days before the experiment starts. The short grazing cells were removed to approximately 15 cm at 11 days before the start of the first 7-day period and again 1 day before the start of each 7-day period. All horses had access to pasture for 10 h/d beginning at 8 AM and ending at 6 PM. Although not at pasture, all horses were individually housed in 3.7 × 12.2 m partially covered pens containing automatic water troughs and a crushed stone surface. Herbage mass (kg DM/ha) was determined by use of a falling plate meter for each pasture to ensure that both groups of horses had adequate dry matter to provide grazing for at least 7 days. On day 7 of each period, jugular venous blood samples were collected from each horse before being turned out to pasture, and then at 2, 4, 6, and 8 hours after turn-out. Pasture samples were also collected from each grazing cell at the same time blood samples were taken. Serum and plasma from blood samples were harvested and analyzed for insulin and glucose concentrations, respectively. Pasture samples were analyzed for water soluble carbohydrate (WSC), ethanol soluble carbohydrate (ESC), and starch. The sum of WSC and starch were used as an estimate of NSC. Area under the curve (AUC) and peak concentration were calculated for both plasma glucose (PPG) and serum insulin (PSI) concentration and were analyzed using analysis of variance for randomized cross-over designs. Pasture WSC, ESC, starch, and NSC concentrations were analyzed using analysis of variance for randomized complete block design. A P value of < .05 was considered significant. Mean pasture plant NSC, WSC, and ESC concentrations were lower (P < .001) in short as compared with tall. Pasture plant starch concentration was not different between treatments. Mean pregrazing plasma glucose concentrations, PPG concentrations, and plasma glucose AUC were not affected by treatment. Mean pregrazing serum insulin concentrations were not affected by treatment. Mean PSI and insulin AUC were greater (P < .01) when horses grazed tall, as compared with short. In conclusion, decreasing the sward height by mowing pasture decreased NSC, WSC, and ESC concentrations and subsequently decreased the postprandial insulin response of horses grazing the pasture. These findings may be important in developing strategies aimed at preventing insulin resistance in grazing horses.     

Laboratory Production of Equine Embryos

Assisted reproduction technologies (ART) are well developed in humans and cattle and are gaining momentum also in the equine industry because of the fact that the mare does not respond to superovulation but can donate large numbers of oocytes through ovum pick up (OPU). After collection, the oocytes can be fertilized by intracytoplasmic sperm injection (ICSI) using a variety of stallion semen samples, even of poor quality, and the resulting embryos can establish high pregnancy rates after cryopreservation and transfer. The discoveries that equine oocytes can be held at room temperature without loss of viability and that an increase in vitro maturation time can double the number of embryos produced are fueling the uptake of the OPU technique by several clinics that are shipping oocytes of their client’s mares to specialized ICSI laboratories for embryo production and freezing. In this article, we present a retrospective analysis of 10 years of work at Avantea with a special focus on the last 3 years. Based on our data, an average production of 1.7 to 2 embryos per OPU-ICSI procedure can be obtained from warmblood donor mares with a pregnancy rate of 70% and a foaling rate in excess of 50%. OPU-ICSI offers the added value of freezing embryos that allows the development of embryo commercialization worldwide to the benefit of top horse breeders who are endorsing this technology as never before.     

不同放牧压和放牧时期对山羊牧食行为的影响

在南方人工草地上,对云岭黑山羊在不同放牧压和放牧时期的牧食行为进行研究。结果表明:放牧压指数较小时,能减少采食时间和采食时行进步数,明显增加每步吃草口数、采食速度、口食量、日采食量、反刍时间,对其他牧食行为影响不大;9月份采食口数、行进步数最少,口食量、日采食量最大,6月份每步吃草口数明显小于其他月份。7,8,9月份采食速度相差不大,小于10月份采食速度;10月份反刍时间、每个食团咀嚼时间最长,反刍咀嚼速度、逆呕时间间隔在不同月份差别不大。     

In Vitro Production of Equine Embryos

The development of methods to produce embryos in vitro in the horse has been delayed compared with other domestic species. Oocytes can be collected from excised ovaries or from the small or preovulatory follicles of live mares. Intracytoplasmic sperm injection is the only reliable method to fertilize equine oocytes in vitro. Intracytoplasmic sperm injection-produced embryos can be transferred into the oviducts of recipient mares or cultured to the morula or blastocyst stage of development for nonsurgical embryo transfers into recipients' uteri. Embryos cultured in vitro have some morphological differences compared with embryos collected from the mares' uteri. Most notably, the embryonic capsule does not form in culture, and the zona pellucida fails to expand completely. However, embryo produced in vitro can result in viable pregnancies and healthy offspring.     

放牧生态系统中的组织物质循环及其在牧场管理中的应用

综述了组织物质循环的理论及其在牧场管理中的应用。放牧过程中牧地草丛内的物流和能流循环是维持放牧生态系统平衡的重要基础,进行牧地草丛中植物组织循环,特别是其生长和萎蔫死亡的动态分析,为草地的有效利用提供了理论依据。文中对于牧地草丛内及刈牧过程中的组织物质循环,连续放牧及间断放牧条件下的组织物质循环进行了重点分析论述。建议在中国各类型草地上应用组织物质循环理论开展放牧管理研究,以推动草地管理理论和实践的发展。     

放牧生态系统草畜间供与求的动态特征

随着季节的变化,牧草生产改变着家畜食料及转化摄取食料的能力,在春、夏、秋季绵羊食物的粗蛋白质含量分别高于草地牧草的15.99%、0.43%和2.71%。在冬季两者的含量几乎相等。但粗蛋白质食入量在春季比夏、秋、冬季分别多21.98%、40.40%和352%。干物质食入量在秋季比夏、冬、春季分别多17.64%、38.33%和72.23%,从而导致冬、春两季绵羊因食物不足而体重下降。     

Dietary and Manure Management Practices on Equine Farms in Two New Jersey Watersheds

Equine farms are increasing in number in Northeast and Mid-Atlantic states. These farms may influence environmental quality owing to manure collection, storage, spreading, and disposal practices. A manure management survey was mailed to 700 New Jersey equine farms during the winter of 2009-2010 (these farms were located in two watersheds). Two hundred forty-two surveys were returned; 10% were training or performance farms, whereas the remainder (90%) were breeding, boarding, or pleasure farms. There were differences between the two watersheds in turnout time, pasture acreage, use of drag harrows, and income. Respondents answered questions about diet and environmental management on farms. Seventy-eight percent had bunk management plans. Forty-seven percent disposed of waste feed in a manure pile, 35% left it on fields or paddocks, and 18% put it in a dumpster. Twenty-six percent engage a professional for feeding advice (21% veterinarians, 2% extension, 3% nutrition consultants). Most respondents did not have a regular feed management plan. Sixty-two percent of all farms spread manure on-farm. Of those who spread, 29% have >8.09 hectares (20 acres) for spreading. Ninety-six percent of respondents stored manure >100 ft from water or wetlands. Comparison of cross-tabulations indicates a strong relationship (P < .01) between rotational grazing and the use of a sacrifice or exercise area. Eighty-eight percent of respondents using sacrifice areas also rotationally graze. Results indicate future outreach programs should focus on feed management, manure storage location, rotational grazing, and the use of sacrifice areas as part of a pasture management program.     

放牧绵羊牧食行为及采食量研究

在锡林郭勒草原对三种放牧绵羊(蒙古羊、引种羊、杂种羊)进行不同月份的牧食行为观察及采食量测定,结果表明:放牧绵羊9月份的采食时间比例均高于8月份;沙质草地放牧绵羊的采食和游走时间比例低于高平原草地;蒙古羊、引种羊和杂种羊沙质草地的平均采食量分别为1.15kg/d、1.60kg/d和1.35kg/d,高平原草地为1.56kg/d、1.82kg/d和1.71kg/d,分别相差0.41kg/d、0.22kg/d和0.36kg/d。