补饲与不补饲条件下3种放牧率对高寒草地牧草与家畜生产的影响

通过补饲和不补饲条件下放牧率对高寒草地牧草和家畜生产影响的研究,结果表明,3种放牧率对草地牧草产量影响不大,组间差异不显著(P>0.05)。放牧率影响羯羊体重。在补饲条件下,羯羊日增长量随放牧率减小而增加,组间差异显著(P<0.05);不补饲使羯羊减重,羯羊日减重量随放牧率减小而降低。同时,放牧率影响羯羊肉用性能和肉的品质。在补饲条件下,草地生物学效率明显高于不补饲组,且中组比低、高组高,草地生产能力最大。由此得出,高寒草地以中等放牧率为最佳,即1.8只/hm~2,且补饲效果最明显。     

内蒙古典型草原草畜系统适宜放牧率的研究Ⅰ.以绵羊增重及经济效益为管理目标

(1)绵羊个体增重与放牧率呈线性负相关,个体最大增重临界放牧率,因季节不同而变化,随着个体增重与放牧率回归系数b绝对值的增大而降低,以始、终放牧期间所得临界放牧率最小,(2.04羊/hm²)。(2)公顷增重与放牧率的关系符合二次曲线,在达到公顷最大增重以前,随着放牧率的增大而增大,之后则随着放牧率的增大而下降,平均543羊/hm²。(3)公顷最大增重并不一定获取公顷最大利润,主要视买卖价格及其差值而定。(4)以冷蒿小禾草为主的退化草原,宜以个体最大增重的适宜放牧率作为管理标准,以使该类草原在利用中得以恢复。     

短花针茅草原五个载畜率水平绵羊活重变化规律

在内蒙古高原短花针茅荒漠草原采用5个不同载畜率水平进行的绵羊放牧试验结果表明,绵羊活重均以10月份为最大,中等载畜率有利于绵羊生产;随着载畜率增大,单位面积的绵羊增重逐渐增加,单个绵羊的增重逐渐减少,两者的交点为绵羊生产的适宜载畜率,即每半年 2.2只羊/hm2.     

The effect of stocking rate and parasite control on the performance of replacement beef heifers on pasture

This study was designed to compare the animal production per unit area and per animal at 3 different stocking rates in combination with two deworming programs. Due to drought conditions, fecal egg output, serum pepsinogen levels and herbage larval counts were low throughout the grazing season. The beneficial effects of the strategic deworming program were, however, indicated by lower fecal egg counts and serum pepsinogen levels in the treated groups during most of the grazing season. Differences in weight gain, favoring the treated groups, were also observed and a clear effect of stocking rate was demonstrated. The lowest stocking rate groups continuously had the lowest egg output and serum pepsinogen levels and the highest average weight gain per animal. The experiment also clearly showed that the production per unit area increased with an increase in stocking rate. The medium and high stocking rate groups had a production per unit area exceeding that of the conventional stocking rate group by 15 and 45%, respectively.     

草原放牧系统持续管理试验研究:试验设计及放牧率对草-畜系统影响分析

在内蒙古典型草原区中国科学院草原生态定位站研究不同放牧率、放牧方式和放牧季节对草原植物和家畜生产的影响。结果表明,地上现存量随着放牧率的增加而降低,但达到峰值的日期提前了。地上生物量与放牧率无明显趋向性变化。家畜增重随着放牧率的增大而下降,公顷总增重与放牧率成二次曲线关系。将放牧率对草原生产力的动态确定为可持续放牧率和改良放牧率。     

Sheep performance under intensive continuous grazing of native grasslands of <Emphasis Type="Italic">Paspalum notatum</Emphasis> and <Emphasis Type="Italic">Axonopus compressus</Emphasis> in the subtropical region of the Highlands of Central Mexico

Liveweight gain was evaluated in tropical Dorper X Pelibuey lambs under intensive continuous grazing of native grasslands dominated by Paspalum notatum (PN) or Axonopus compressus (AC) in the subtropics of Central Mexico. Two trials were undertaken. Trial 1 lasted 12 weeks with 10 lambs (initial weight 18 +/- 2.57 kg, 3 months old) per treatment in 2002, and Trial 2 for 13 weeks with 8 lambs (initial weight 24.0 +/- 2.0 kg, 4 months old) per treatment. Lambs were weighed once per week, and liveweight change was estimated by linear regression over day of the experiment, using individual regression coefficients as unbiased estimates of daily liveweight change; analysed in a random block design. Lambs on Trial 1 gained 0.061 kg/lamb/day on PN and 0.047 kg/lamb/day on AC (P > 0.05) at an overall mean stocking rate of 25 lambs/ha. In Trial 2, liveweight gain was significantly larger in PN (0.060 kg/lamb/day) than on AC (0.043 kg/lamb/day) (P < 0.05), at a mean stocking rate of 21.5 lambs/ha. It is concluded that intensive continuous grazing of native grasslands in the subtropics of the highlands of Central Mexico enables moderate liveweight gains for weaned lambs during the rainy season; with better results in grasslands dominated by Paspalum notatum.     

放牧强度对高寒草地产草量及羊体质量增加的影响

以托云牧场高寒草地为研究对象,通过设置3个放牧样地,一个对照样地,研究不同强度放牧对草地地上生物量的影响以及在不同放牧压力下羊体质量增加的效果。结果表明,1）托云牧场是以银穗草（Leucopoa albida）、羊茅（Festuca arioides）、点地梅（Androsace umbellata）和棘豆（Oxytropis falcatae）为优势种的高山草地;2）高寒草地地上生物量较低,禁牧区7月地上生物量（干物质）仅830 kg·hm-2;3）放牧活动对地上生物量有较大影响,重度放牧能显著降低牧场地上生物量;4）以羊体质量增加值为评价指标,该高寒牧场在载畜量为1.05羊单位·hm-2时能获得较好的体质量增加效果。     

Growth performance of yearling horses grazing bermudagrass pastures at different grazing pressures

Body weight gains and height at the withers were measured in yearling geldings grazing bermudagrass (Cynodon dactylon [L.] Pers.) pastures with neither energy nor protein feed supplementation at stocking rates of 6.7, 8.0, 9.5 and 12.4 yearlings per hectare. Weekly forage samples were taken to estimate the quantity and quality of available forage. These samples were clipped and separated into three equal lengths to characterize upper, middle and lower thirds of the canopy and to determine relationships between available forage and yearling growth rate. Average daily gain was influenced by stocking rate, but gain in height was not affected by stocking rate. Average daily gain ranged from -.31 to .37 kg/d and was negatively related to stocking rate. A quadratic relationship between available forage and ADG was detected. However, a linear relationship between ADG and available forage in top layers of the canopy indicated that animal performance might have been limited by availability of top layer forage in pastures subjected to light grazing pressure.     

Responses of yearling steers to different stocking rates on a subtropical grass-legume pasture

Despite potential benefits, limitations of individual tropical legumes have restricted development of sustainable grass-legume pastures in tropical and subtropical regions. Sowing mixtures of complementary legumes may overcome limitations of individual species. Responses of yearling steers grazing a mixture of three tropical legumes with bahiagrass (Paspalum notatum Flugge) were evaluated at three stocking rates under continuous grazing. Carpon desmodium (Desmodium heterocarpon [L.] DC.), which is persistent under grazing but often difficult to establish, was combined with the short-lived legumes aeschynomene (Aeschynomene americana L.) and phasey bean (Macroptilium lathyroides [L.] Urb.). Diet composition, as determined by microhistological analysis of fecal samples, and animal performance were evaluated in three grazing periods: summer 1987 and spring 1988 (2.0, 3.5, and 5.0 steers/ha) and summer 1988 (3.0, 5.3, and 7.5 steers/ha). Stocking rate did not affect percentage of the selectively grazed legumes, aeschynomene and phasey bean, in the diet. Average daily gain decreased linearly (P less than .05) with increased stocking rate, as is typical for grass pastures. Aeschynomene and phasey bean contributed to diets during the first summer, and carpon desmodium contribution was greater in the second summer. These results indicate that this pasture mixture can provide legume herbage from aeschynomene and phasey bean in the year of sowing and from carpon desmodium thereafter. Over the range of grazing pressures obtained, legume responses were generally consistent; thus, optimizing stocking rate for gain per hectare or for economic returns can be targeted without additional constraints to maintain the contribution of these legumes to grazing livestock.     

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.     

Mathematical models to assess strategies for the control of gastrointestinal roundworms in cattle 1. Construction

Mathematical models were constructed to simulate the effect of Ostertagia ostertagi infections on the growth of young cattle. The equations are based on System Dynamics using the DYSMAP 2 software package in their construction. A pasture and animal growth model simulates the growth of pasture and the influences of management and climate on it; cattle feed intake and conversion into energy for maintenance and liveweight gain; the effect of the parasite burden on feed intake and utilization of energy. This model was then combined with one of the life cycle of O. ostertagi in order to determine the effect of worm burdens on animal growth rate in a range of farm conditions, such as stocking rate, grazing history of the pasture, and rainfall. By converting the resultant liveweight gain into a monetary value, an economic assessment of alternative worm control strategies can be made. In this paper the construction of the models with equations and assumptions is given in detail.     

Effects on animal performance and sward composition of mixed and sequential grazing of permanent pasture by cattle and sheep

Previous experiments have shown that mixed or conjoint grazing, when two or more animal species are grazed together, can lead to improved performance of one or more of the species and a higher total output per unit area. Sequential grazing systems, when different animal species graze an area in succession, also have the potential to improve productivity. This experiment directly compared these two approaches for integrating the grazing of cattle and sheep when pastured on improved permanent pasture. Four treatments were compared: 1) sheep only from May to October (S/S); 2) cattle only from May to July followed by sheep only from August to October (C/S); 3) cattle and sheep from May to July, sheep only for the rest of the growing season (C + S/S); and 4) cattle and sheep from May to October (C + S/C + S). Each treatment was replicated three times. From May until weaning at the end of July the plots were grazed by steers and ewes and lambs, and from weaning until October by steers and lambs. Sward heights were maintained at 6 cm using a “put and take” stocking system. Animal performance and sward composition data were collected during three growing seasons, 2001–2003. During the pre-weaning period lambs grazing plots which were grazed only by sheep had significantly poorer growth rates than those grazing plots where there was mixed grazing. Lambs grazing the sheep only plots also had lower liveweight gain during the post-weaning period, with the highest growth rates being recorded on the C + S/C + S treatment. Carrying capacity and total liveweight gain per unit area post-weaning were also consistently higher for the C + S/C + S treatment, while carrying capacity pre-weaning was highest for the C/S treatment. Measurements of clover content in the grazed horizon and botanical separation of material from quadrat cuts indicated that even under relatively controlled conditions choice of grazing system can influence sward composition. However, there was no clear link between any single sward change and the growth of the animals, indicating that the improved performance of cattle and sheep under mixed grazing is the result of a combination of factors, rather than a response to a particular sward parameter.     

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。     

Towards the development of a bioeconomic stocking model for the semi‐arid savanna of KwaZulu‐Natal

Abstract

Rainfall variability is a major determinant of system dynamics and profitability of livestock enterprises in arid and semi‐arid environments. Range managers consequently require detailed information on the financial and ecological implications of various stocking strategies in order to formulate viable management systems. Data collected over seven seasons (1986–1993), from a series of extensive grazing trials in the semi‐arid savanna of KwaZulu‐Natal with cattle stocked at three rates (0.17, 0.23 and 0.30 LSU ha^?1) were used to develop a bioeconomic stocking model (LOWBEEF). The model comprised two biological sub‐models (BEEF and GRASS), and an integrated economic component. The BEEF sub‐model related seasonal live mass gain to stocking rate and rainfall. The GRASS sub‐model related residual herbage at the end of summer to summer stocking intensity, range condition (indexed as the sum of proportions of three key forage species, Themeda triandra, Panicum maximum and P. coloratum) and rainfall. The period over which supplementary feeding would be required to maintain cattle mass was related to residual summer herbage mass. The biological sub‐models were linked to an economic component model (ECON) to reflect the influence of various environmental and economic parameters on profitability.     

Effects of establishment method and fall stocking rate of wheat pasture on forage mass, forage chemical composition, and performance of growing steers

Stocking rate is a fundamental variable for managing pastures, and there is a distinct relationship between stocking rate and animal performance for each forage type. This research was conducted to determine the effects of fall stocking rate (SR) and method of establishment of wheat pasture planted into dedicated crop fields on animal performance during the fall and subsequent spring. There was a factorial arrangement of tillage methods used in the establishment of wheat pasture and fall stocking rates. Tillage treatments included 1) CT, seed sown into a prepared seedbed, 2) RT, a single pass with a light disk followed by broadcasting of seed, or 3) NT, direct seeding into the undisturbed stubble of the grazed-out wheat pasture from the previous year. The fixed SR during the fall were 1.9, 2.5, and 3.7 growing beef steers (Bos taurus L.)/ha. In the spring all pastures were grazed at the same fixed SR by steers for graze out. Data were analyzed using the mixed procedure of SAS as a randomized complete block design with field as the experimental unit and year as the block. Forage mass, forage nutritive composition, and animal performance during the fall or spring were not affected (P ≥ 0.14) by tillage method. During the fall grazing season, with increasing SR there were linear (P < 0.01) decreases in BW of steers upon removal from pasture, BW gain per steer, and ADG, whereas grazing-day per hectare and BW gain per hectare increased linearly (P < 0.01) with increasing SR. The carryover effects of fall SR into the spring grazing season decreased (P< 0.01) grazing-day per hectare and tended (P ≤ 0.09) to produce quadratic changes in BW upon removal from pasture and BW gain per hectare. Across the fall and spring grazing seasons, grazing-day per hectare increased linearly (P < 0.01) with greater SR, and BW gain per hectare increased quadratically (P = 0.02) with increased fall SR. A tillage treatment by fall SR interaction (P = 0.10) indicates that although there was no difference (P ≥ 0.12) due to tillage treatment in BW gain per hectare at 1.9 or 2.5 SR, NT fields produced (P ≤ 0.04) more BW gain per hectare than CT or RT at the 3.7 SR. Although increasing SR of growing steers leads to reduced animal performance in the fall and reduced carrying capacity in the spring, NT appears to be capable of withstanding greater fall SR with less impact on total production per hectare than CT or RT.     

Response of lambs to continuous and rotational grazing at four grazing intensities on Midmar Italian ryegrass

Abstract

Irrigated Midmar Italian ryegrass (Lolium multiflorum Lam.) was grazed either continuously or rotationally at four grazing intensities by three successive sets of weaned lambs for the winter, spring and summer periods, respectively. The “put‐and‐take” system was applied. In the case of continuous grazing, amounts of available dry matter (DM) per hectare were varied, whereas with rotational grazing different grazing intensities were established by allocating different amounts of DM per unit livemass. Amounts of DM on offer were determined in both systems to provide a basis for comparison.

There were no differences in average daily gain (ADG) at equivalent levels of available DM between grazing procedures in winter. In both spring and summer, however, ADG at given levels of available DM was greater (P ≤0,01) with continuous than with rotational grazing. Stocking rate at equivalent levels of available DM was higher (P ≤0,01) for rotational as compared with continuous grazing in winter and summer, but in summer, grazing procedure had no effect on stocking rate. There was an interaction between stocking rate and grazing method in winter (P ≤0,01). At high stocking rates, ADG were higher (P ≤0,01) under rotational than under continuous grazing. In spring and summer the ADG for continuous grazing was higher (P ≤0,01) than that for rotational grazing at equivalent stocking rates. The estimated stocking rates for maximum gains/ha ranged in the different seasons from 45 to 123 lambs/ha.     

Shifting Cattle Producer Beliefs on Stocking and Invasive Forage: Implications for Grassland Conservation

To advance the dialogue to define sustainable working landscapes, it is essential to include the perceptions, knowledge, and factors guiding decision making. We surveyed livestock producers in the Grand River Grasslands region of southern Iowa and northern Missouri, United States, to gain insight into key factors shaping decision making and perspectives on effective management practices in the eastern Great Plains, focusing in particular on demographic and social change and producer willingness to reduce stocking rate as a conservation practice. First, a longitudinal evaluation of livestock producer demographics in 2007 and 2017 revealed individuals were older and were renting grazing land to a greater extent than in 2007. Second, when making land management decisions, producers in 2017 focused on economic concerns more than environmental concerns compared with more balanced views in 2007. For those who prioritized the environment over economics, this prioritization was related to both higher levels of education and a willingness to reduce stocking rate (livestock production) if there is a positive conservation outcome. In contrast, a lower willingness to reduce stocking was associated with increasing rental acreage and prevalence of an invasive cool-season grass that responds favorably to heavy grazing (tall fescue, Schedonorus arundinaceus Schreb.). Regardless, about 37% of cattle producers representing ∼ 40% of the land area surveyed were at least moderately willing to reduce stocking rates to achieve a conservation outcome. In conclusion, our findings suggest that producers’ need to gain income from livestock may limit the willingness to enact a conservation practice similar to reduced stocking rates. However, there is clearly conservation receptiveness from a segment of the producer community, which indicates potential for improved conservation.     

Integrating Ranch Forage Production,Cattle Performance,and Economics in Ranch Management Systems for Southern Florida

The presence of grazing cattle near open waterways has created environmental concerns related to the potential for water contamination. In Florida the removal of cattle from grazing landscapes or decreasing stocking density is being investigated as one option to improve the quality of surface water runoff draining into Lake Okeechobee, Florida. The objective of this study was to determine the effects of stocking rate on cow-calf performance, forage availability and quality, and ranch economic performance. Experimental pastures were established on a southern Florida cow-calf operation with stocking rates of 0.58, 1.01, and 1.35 ha·cow^-1 on summer pastures and 0.93, 1.62, and 2.16 ha·cow^-1 on winter pastures, corresponding to high, medium, and low rates, respectively. The study was conducted over 4 consecutive production years. Cow body condition scores (BCS), pregnancy rate, and calf average daily gain were used as measures of animal performance. Forage utilization was estimated by measuring the difference between forage yield inside and outside grazing exclusion cages and forage quality by crude protein and in vitro organic matter digestibility. Forage yield, utilization, and quality were not significantly affected by stocking rate. Although statistically not significant (P = 0.17), cattle in the high stocking rate experienced a numerically greater loss of BCS following the winter grazing period, but stocking rate did not affect pregnancy rate or calf gains. Production (kg weaned calves·ha^-1) was increased (P < 0.01) for a high stocking rate compared with medium and low stocking rates. Overall ranch profitability will decrease as stocking rates decline. Ranch revenues decrease one-for-one as stocking rates decrease. At the same time, unit cow costs increase at an increasing rate as fewer brood cows are left to support the ranch's fixed cost structure.     

Survey of the stocking densities at which sheep are transported commercially in the United Kingdom

A total of 6578 sheep carried in 74 vehicles to one slaughter plant were monitored, and stocking densities, in terms of m2 floor area available per 100 kg liveweight, were estimated from the dimensions of the vehicle pens and estimates of liveweight based on chest girth measurements. The observed stocking densities ranged from 0.29 to 2.00 m2/100 kg liveweight, and the average density was 0.65 m2/100 kg. One per cent of the sheep were carried at estimated stocking densities of less than 0.3 m2/100 kg, 37 per cent at densities between 0.3 and 0.6 m2/100 kg and 57 per cent at densities between 0.6 and 0.9 m2/100 kg. Over 30 per cent of the animals in the survey were transported at densities higher than the working recommendations made by the Farm Animal Welfare Council.     

Effects of Grazing Pressure on Efficiency of Grazing on North American Great Plains Rangelands

Comparisons of stocking rates across sites can be facilitated by calculating grazing pressure. We used peak standing crop and stocking rates from six studies in the North American Great Plains (Cheyenne, Wyoming; Cottonwood, South Dakota; Hays, Kansas; Nunn, Colorado; Streeter, North Dakota; and Woodward, Oklahoma) to calculate a grazing pressure index and develop relationships for harvest efficiency, utilization, grazing efficiency, and animal performance and production. Average grazing pressures for heavy, moderate, and light stocking across the study sites were 40, 24, and 14 animal unit days · Mg^?1, respectively. These grazing pressures resulted in average harvest efficiency values of 38%, 24%, and 14% and grazing efficiencies of 61%, 49%, and 39% for heavy, moderate, and light stocking rates, respectively. Utilization increased quadratically as grazing pressure index increased, whereas grazing and harvest efficiencies exhibited a linear increase with grazing pressure. The latter indicates that nonlivestock forage losses (e.g., weathering, senescence, wildlife, insects) were disproportional across stocking rates. Average daily gain of livestock decreased linearly as grazing pressure index increased across study sites. Prediction equations reaffirm assumptions of 50% grazing efficiency and 25% harvest efficiency associated with moderate stocking. Novel here, however, is that harvest and grazing efficiencies increased at high grazing pressures and decreased at low grazing pressures. Use of grazing pressure index to “standardize” stocking rates across rangeland ecosystems in the North American Great Plains should improve communication among scientists, resource managers, and the public, and thus better achieve both production and conservation goals on these lands.