Effect Of Stocking Rate Research Articles

Tallgrass Prairie Response to Grazing System and Stocking Rate

Grazing system and stocking rate effects on standing crop of species and relative species composition of tallgrass prairies in north-central Oklahoma were evaluated from 1989 to 1993. Twelve experimental units, consisting of pastures dominated by big bluestem [Andropogon gerurdii Vitman], little bluestem [Schizachyrium scoparium (Michx.) Nash], and indiangrass [Sorghustrum nutuns (L.) Nash], were arranged in a completely randomized design with either a short duration rotation or continuous grazing system and stocking rates ranging from 51.5 animal-unit-days/ha (AUD/ha) to 89.8 AUD/ha. Yearling steers grazed the pastures from late April to late September. Cumulative precipitation was above average during the study period. Continuous and rotation grazing affected the major herbage components similarly over time. Standing crop of all major herbage components declined as stocking rate increased. The standing crop of the major herbage components also declined from the first to the last year of the study. The decrease in standing crop of big bluestem, indiangrass and forbs over years was greatest at lighter stocking rates. Relative composition of switchgrass

Grazing system and stocking rate effects on the productivity, botanical composition and soil surface characteristics of alfalfa-grass pastures

A 4-yr experiment was conducted (1991 to 1994) near Brandon, MB, to determine the effects of grazing system (continuous and rotational) and stocking rate [light (1.1 steers ha−1); heavy (2.2 steers ha−1)] on the productivity, botanical composition and soil surface characteristics of an alfalfa (Medicago sativa L.; approximately 70%), meadow bromegrass (Bromus biebersteinii Roem & Schult.; 25%) and Russian wild ryegrass [Psathyrostachys juncea (Fisch.) Nevski; 5%] pasture. Grazing season length was shorter (P < 0.05) for cattle in continuously compared with rotationally stocked pastures in 1991, while in 1993 and 1994 it was shortest (P < 0.05) in heavily stocked continuously grazed pastures. Carrying capacity (steer days ha–1) was greater (P < 0.05) in heavily stocked rotationally grazed pastures compared with other treatments in 1991, 1993 and 1994. In 1992, it was greater (P < 0.05) in heavy than light stocking rate treatments for both rotationally and continuously grazed pastures. Cattle usually gained more (P < 0.05) per day (kg d−1) and during the season (kg hd−1) at light than at heavy stocking rates, while total liveweight production (kg ha−1) was greater (P < 0.05) at heavy than at light stocking rates. Forage production and disappearance did not differ (P > 0.05) within grazing systems and stocking rates from 1991 to 1993, but in 1994, production and disappearance were greater (P < 0.05) at heavy than at light stocking rates. Mean seasonal herbage mass available and carry-over were greater (P < 0.05) in lightly stocked pastures than heavily stocked pastures from 1991 to 1994. After the first year of grazing, the proportion of alfalfa increased (P < 0.05), while grasses declined (P < 0.05) within all grazing treatments. In subsequent years, a trend was observed, where alfalfa declined and grasses increased in all pastures, except those stocked heavily and grazed continuously, which by 1994 had the greatest (P < 0.05) percentage of alfalfa. As years progressed, increases (P < 0.05) in basal cover concurrent with declines in bare ground were recorded on all grazing treatments, while litter cover often did not differ (P > 0.05) within either grazing system or stocking rate, except in 1992, when basal cover was lowest (P < 0.05), while litter cover was greatest (P < 0.05) on lightly stocked continuously grazed pastures compared with other treatments. Stocking rates were a key factor to optimizing individual animal performance and/or gain per hectare on alfalfa grass pastures, however differences in the effect of continuous and rotational stocking on pasture productivity were minimal. Key words: Alfalfa, grazing, stocker cattle, production

Stocking rate effects on sheep and forage productivity under rubber in Malaysia

The productivity of grazing sheep was assessed under 7-year-old rubber at the Rubber Research Institute of the Malaysia Experimental Station at Sungai Buloh near Kuala Lumpur between October 1988 and May 1990. The sheep were Dorset × Marlin crossbred lambs and they grazed planted leguminous cover crops and naturally occurring species at a range of stocking rates.In the immature rubber trial, presentation yields of forage declined with time regardless of stocking rate. In the mature rubber trial, presentation yields of forage were low (<1000 kg/ha) due to low light transmission. High stocking rates (>6 sheep/ha) resulted in a decrease in the proportion of palatable species, namely Pueraria phaseoloides, Paspalum conjugatum, Asystasia gangetica and Mikania micrantha and an increase in the proportion of the less palatable species such as Calopogonium caeruleum and Cyrtococcum oxyphyllum.Daily liveweight gains ranged from 100 g/lamb per day at 4 sheep/ha to 70 g/lamb per day at 14 sheep/ha in the immature rubber trial. Only the lowest stocking rate of 2 sheep/ha was continuously sustainable in the mature rubber trial. The estimated maximum liveweight gain that could be achieved under immature rubber was 266 kg/ha per year at a stocking rate of 13·2 sheep/ha.

The Effect of Stocking Rate on Herbage Utilization under Time-restricted Grazing by Lactating Dairy Cows

The Effect of Stocking Rate on Herbage Utilization under Time-restricted Grazing by Lactating Dairy Cows

Long-term stocking rate effects on soil physical properties

Summary. The effects of sheep stocking rate on soil physical properties were investigated in a long-term (>30-year-old) grazing trial on the Northern Tablelands of New South Wales. The soil physical properties studied were unsaturated hydraulic conductivity, soil strength and bulk density. Significant differences between the ungrazed and grazed pastures were found for all soil physical measurements. Compaction by sheep was limited to the upper 5 cm of the soil profile and resulted in lower porosity, mainly due to loss of pores larger than 1.2 mm equivalent diameter. However, after 30 years, the pastures grazed at 10, 15 and 20 sheep/ha had similar soil physical properties. Soil physical properties appear to be relatively insensitive to stocking rate in the long term and therefore other factors, such as maintenance of pasture cover, should be given a higher priority in grazing management decisions.

Effects of Grazing Management on Standing Crop Dynamics in Tallgrass Prairie

Grazing system and stocking rate effects on forage standing crop of tallgrass prairies in north-central Oklahoma were evaluated from 1989 to 1993. Twelve experimental units, consisting of pastures dominated by big bluestem [Andropogon gerardi Vitman], little bluestem [Schizachyrium scoparium (Michx. Nash], indiangrass [Sorghastrum nutans (L.) Nash], and switch grass [Panicum virgatum L.], were arranged in a completely randomized design with either a short duration rotation or continuous grazing system and stocking rates ranging from 127 kg animal live-weight/ha to 222 kg live-weight/ha. Yearling steers grazed the units from late April to late September. Herbage standing crop was sampled in July and September. Total, live, and dead standing crops did not differ significantly between the 2 grazing systems in July. Total standing crop was significantly higher in the rotation units in September (3,600 versus 3,020 kg/ha, P < 0 .05). Dead standing crop was also higher in the rotation units in September (1,950 versus 1,570 kg/ha, P < 0 .05). Evidence suggests the difference in standing crop between systems is due, in part, to reduced forage intake by the livestock. Grazing system did not interact with either stocking rate or year. Stocking rate had significant effects on total, live and dead standing crops at both sample dates. The slope of the total standing crop-stocking rate relationship varied over years and ranged from -12 to -36 kg/ha per kg live-weight/ha in July and from -12 to -27 kg/ha per kg live-weight/ha in September. Higher standing crop at the end of the grazing season in the rotation units would mean greater soil protection and higher fuel loading for prescribed burning, and would suggest a lower impact on plant vigor. However, if the higher standing crop is a result of lower forage intake, we would expect livestock weight gains to decline.

The impact of sheep trampling and stocking rate on the physical properties of a red duplex soil with two initially different structures

The effect of sheep trampling and stocking rate on the physical properties of a red duplex soil with two initially different structures was examined over an 8 week period when the soil was wet following winter rains. The experimental site was located at Merredin in Western Australia where the average annual rainfall is 307 mm. A previous long-term tillage and gypsum trial at the experimental site had resulted in the development of contrasting topsoil structures. Three grazing treatments were imposed at the trial site: grazing at the normal high stocking rate (8 DSE ha-1), grazing at half the normal stocking rate (4 DSE ha-1), and no grazing (where pasture was mown to simulate grazing without trampling). Topsoil structure was assesed by measuring water-stable aggregation (&gt; 2 mm diameter aggregates), the relative contribution of dispersion and slaking to structural instability (measured as soil strength on &lt; 2 mm fine earth soil fractions), steady-state infiltration rates (at 10 mm tension), and in situ soil strength characteristics (measured as penetration resistance). At the end of the grazing period, all structure attributes measured showed that topsoil structure had been damaged as a result of sheep trampling. The magnitude of such structure damage was affected by the initial physical condition of the soil and stocking rate. When compared with ungrazed pasture, there was a greater decline in structural condition as a consequence of grazing on less well-structured soil than on better-structured soil. Halving the normal stocking rate reduced the degree of structure damage on both soils. Within-season variability in soil hydraulic properties was large. The temporal changes in infiltration rates were attributed to changes in drainage pore volume brought about by the growth and decay of pasture roots, the formation and disruption of a surface crust, and the processes of soil compaction and remoulding resulting from animal trampling (no direct measurements were made). The variability in hydraulic behaviour found in this study emphasizes the need to maintain consistent sampling dates and soil water contents at sampling in long-term studies on soil structure changes.

Effects of grazing system and stocking rate on cow-calf performance in the Flint Hills (1995)

A 6-year study was design ed to measure the influences of stocking rate and grazing system on performance of cow-calf pairs grazing tallgrass prairie. This paper summarizes the initial 3 years. Late-season rest-rotation was compared to continuous grazing over low, moderate, and high stocking rates. No differences (P>.10) were observed in body weight of cows or calves as a result of grazing system or stocking rate. However, calf weaning weight tended (P=.20) to be greater with continuous grazing than with late season rest-rotation. Cow body condition score was unaffected (P>.10) by stocking rate or grazing system. Conception rates were also similar between stocking rates and grazing systems. This preliminary information suggests that application of a late-season rest-rotation grazing system will support cowcalf performance comparable t o that with a continuous system at a similar stocking rate.

Effects of stocking rate in spring on liveweight and wool production of sheep grazing annual pastures

Two experiments examined the effects of different stocking rates in spring, and hence the availability of annual pastures, on changes in liveweight and wool production in Merino wethers (Experiments 1 and 2 respectively: age 5 and 2+-year-old; liveweight 63.8 � 0.64 (s.e.m.) kg and 43.8 � 0.34 kg; condition score 3.9% 0.14 and 3.l � 0-08). In Experiment 1, stocking rates were 8, 16, 24, 32 and 40 sheep/ha from 8 August, 1989 f9r 122 days; Experiment 2 involved an additional stocking rate of 48 sheep/ha from 23 August, 1990 for 98 days. Feed on offer (FOO kg DM/ha) declined (P &lt; 0.01) linearly as stocking rate increased. Stocking rate and initial FOO (ranging between 1100 and 7000 kg DM/ha) had no significant effects on pasture growth rate (PGR) through most of spring. Late in spring, increased stocking rates resulted in greater (P &lt; 0.05) PGR. The total amount of pasture produced in the grazing period was not significantly affected by stocking rate (Expt 1, 7530 to 8200 kg DM/ha; Expt 2, 6390 to 6860 kg DM/ha). The relationships between liveweight change (LWC) or wool growth rates (WGR) and FO, during the period until pasture wilting at the lowest stocking rate (83 days in Expt 1; 76 days in Expt 2), were described by Mitscherlich equations. More than 74% of the variation in LWC or WGR was explained by differences in green FOO. In Expts 1 and 2 respectively, more than 90% of the maximum liveweight gain (66 and 192 g/day) was achieved at a FOO of 4000 or 3000 kg DM/ha, and sheep maintained weight at 2000 or 1000 kg DM/ha. More than 90% of the maximum WGR (22.3 and 19.0 g/day) was achieved at a FOO of 3000 or 2000 kg DM/ha. More than 70% of the variation in WGR was explained by LWC in both experiments. The slopes of the linear relationships were 0.047 g wool/g LWC in Expt 1, and 0.024 g wool/g LWC in Expt 2. At liveweight maintenance, sheep produced 15% less (Expt 1) or 25% less (Expt 2) wool than those grazed under conditions which allowed maximum rates of liveweight gain. Fibre diameter (FD) and length of wool grown were affected in the same manner as WGR by increases in FOO and hence LWC. In Expts 1 and 2 respectively, total clean wool weights were reduced by 17 and 9 g, mean FD by 0.05 and 0.02 microns and staple length by 0.35 and 0.13 mm, for each increase of one sheep/ha during the spring treatment periods. The effects of stocking rate in spring on annual wool production, mean FD and staple length were described by linear (P &lt; 0.05 to P &lt; 0.01) relationships. Standard deviation of midside FD (Expt 2), staple strength and position of break (both experiments) did not change significantly with stocking rate. These results indicate that grazing to a lower FOO during spring can be used to manipulate the amount and characteristics of wool produced by Merino wethers grazing annual pastures in Mediterranean climates with 600-700 mm rainfall.

Grazing Initiation Date and Stocking Rate Effects on Pasture Productivity

AbstractDate of grazing initiation in spring and stocking rate have large effects on both animal and pasture productivity. A grazing experiment with yearling steers (Bos taurus L.; average 320 kg) was conducted in the growing season of three years to compare two dates of grazing initiation (differing by 2 wk) at three stocking rates (3, 4, and 5 steers ha−1) on set‐stocked naturalized pasture in the AppalachiaUn USA. Pasture botanical composition, herbage mass and accumulation, and animal liveweight changes were measured. Early grazing initiation increased percentage grass in the pasture compared with late initiation. Crude protein concentration was higher, and acid‐ and neutral‐detergent fiber were lower in pastures on which grazing was initiated earlier. Herbage mass was &gt;33% more at the later grazing initiation date compared with the early initiation date. Earlier grazing initiation did not affect pasture dry matter accumulation or average daily gain but animal gain per hectare was almost 20% higher with earlier grazing. Stocking rate the previous year had no effect on botanical composition or herbage mass at initiation of grazing. A verage daily gain was highest at 4 steers ha−1 (0.81 kg) and lowest at 5 steers h−1 (0.62 kg). Animal production per hectare was almost 50% greater at 4 steers ha−1 (358 kg) than at 3 steers h−1 (246 kg). We conclude that naturalized pasture in Appalachia can be grazed early without detrimental effects.

Herbage and animal production from native pastures and pastures oversown with Stylosanthes hamata. 1. Fertiliser and stocking rate effects

Native pastures dominated by Heteropogon contortus (speargrass) were sown to Stylosanthes hanzata cv. Verano in 1972, and herbage production and steer growth rates were compared with those of native pastures from 1973 to 1985. The native pastures also contained naturalised Stylosanthes humilis, but its contribution to pasture yield diminished rapidly, after infection by Colletotrichum gloeospoirioides (anthracnose) in 1973. The experiment was a factorial design of 2 pasture types (native, native plus Verano) x 2 stocking rates (0.6, 1.2 steers/ha) x 2 superphosphate treatments (nil, 300 kg/ha.year) x 2 replicates. Fertiliser application decreased the proportion of legume but had no significant effect on herbage or animal production on this comparatively fertile site (extractable P, 18 mg/kg). Annual liveweight gains at the high and low stocking rates, respectively, on the native pasture averaged 100 and 120 kg/steer. Sowing to Verano did not affect herbage yields but increased annual liveweight gains by 28 and 36 kg/steer at low and high stocking rates. The high stocking rate of 1.2 steers/ha was sustainable for the first 9 years of the experiment, when above-average rainfall was received. However, in the following 3 below-average years, there was a shift to less-desirable species, and a decline in pasture productivity. Relative to the low stocking rate, herbage production on the native pasture in the final season was reduced by 60% and on the Verano pasture by 26%. The highest annual herbage utilisation rate that appeared sustainable in the long term was about 45%, which corresponded to a utilisation rate of 30% during the growing season (about November-May). When oversown with Verano, speargrass tended to decline in favour of annual grasses, weeds, and the introduced grass Urochloa mosanzhicensis, which had been sown on an adjacent experiment. Urochloa appeared to be a more suitable companion species than speargrass for Verano.

Superphosphate maintains soil fertility and beef production on grazed white clover pastures in the subtropics. 1. Residual soil phosphorus, sulfur, and nitrogen, and pasture growth responses

Phosphorus (P) as superphosphate was applied at 0, 12, 24, and 48 kg P/ha each year from 1972 to 1980 to an established white clover (Trifolium repens) and carpet grass (Axonopus affinis) pasture, to measure long-term changes in soil fertility and pasture production under grazing on a duplex soil in a coastal, subtropical environment. Hereford weaner steers grazed the pasture at 2 stocking rates (1.67 and 2.5 steers/ha) from 1972 to 1974, and at 3 stocking rates (1.67, 2.50, and 3.3 steers/ha) for 7 years to 1981. The effects of P and stocking rate during 1972-76 on pasture and animal production were small and variable, so the study was extended to 1980-81 to measure longer term P and stocking rate effects on soil fertility. Available soil P (bicarbonate-extracted) and sulfur (S, phosphate-extracted) responded (P&lt;0.05) linearly over time to rates of maintenance superphosphate. For soil P, this effect increased with time and showed seasonal fluctuations, which were described by a model with linear and curvilinear functions. After 9 years, average soil P levels at the 4 rates of applied superphosphate changed from 32 to 12, 24, 45, and 91 mg P/kg soil, respectively. A residual value function (RVF) was used to predict the residual value of applied phosphorus over time, which fitted the observed values of available soil P for each fertiliser treatment (R2 = 0.99). The soil S response to superphosphate remained constant over time. Mean values at the 4 rates of applied superphosphate were 8, 11, 15, and 25 mg/kg. Over the 9 years, total soil nitrogen increased (P&lt;0.01) linearly from 0.134 to 0.179% and pH decreased (P&lt;0.05) slightly from 5.7 to 5.2, but neither was significantly affected by superphosphate application. Total pasture and clover growth measured in cages responded linearly to superphosphate, with maximum (P&lt;0.05) response occurring in spring each year from 1972-73 to 1976-77. It was concluded that on this duplex soil with 32 mg/kg of bicarbonate-extractable P, omitting superphosphate reduced soil P after 12 months and pasture growth within 18 months. Annual applications of superphosphate from 125 to 250 kg/ha (12-24 kg P/ha) maintained bicarbonate-extractable soil P in the range 24-45 mg/kg and improved growth and seed reserves of white clover in this environment.

An analysis of an ordinary differential equation model for a two-species predator-prey system with harvesting and stocking

An analysis is presented for a model of a two-species predator-prey system where each species can be harvested or stocked. Using methods from bifurcation theory the qualitative nature of the steady-state solutions is examined. The effect of harvesting and stocking rates and the prey carrying capacity is examined in detail.

A comparison of continuous and rotational grazing on veld at two stocking rates

Two rotational grazing procedures, a four‐paddock system with a 10‐day period of stay and an eight‐paddock system with a 5‐day period of stay, were compared with continuous grazing on veld. The trial was conducted 40 km south of Bulawayo in Zimbabwe, over the six‐year period 1975–81. Using yearling steers, the treatments were applied at two year‐long stocking rates, 1.8 and 2.5 ha steer−1, and were replicated twice. Fresh groups of steers were used in the trial each year. Steer performance was virtually identical in all treatments, except continuous grazing at the lower stocking rate, in which, during the growing season, mass gains were on average 13% higher than those in the other treatments. Although floristic composition changed over the period of the trial, no differential effects of either grazing procedure or stocking rate were detected on the composition.

Foraging Behavior by Mule Deer: The Influence of Cattle Grazing

We studied the effects of different cattle stocking rates on activity patterns of female mule deer (Odocoileus hemionus) on a summer range in the Sierra Nevada of California. Using an automated telemetry system, we determined that deer averaged 32±2.2 (SE)% of the time feeding, 8±1.1% traveling, and 60±2.4% resting per 24-hour period. Deer spent more time feeding and less time resting with increased cattle stocking rates. During 1984, a year of average precipitation, deer spent more time feeding per day in late summer than in early summer in range units grazed by cattle but did not do so in ungrazed range units. In 1985, a drier year, deer spent less time feeding per day in late summer in grazed range units

Winter Sheep Grazing in the Irrigated Sonoran Desert: II. Soil Properties and Alfalfa Regrowth

Irrigated alfalfa (Medicago sativa L.) fields of the Sonoran Desert of the southwest USA produce high quality hay for 9 to 10 mo and also become winter pature for sheep (Ovis aries). Presently, the common practice is to have the sheep graze until only bare ground and grazed alfalfa crowns remain. Our objective was to evaluate the effects of sheep stocking rates on first-cutting alfalfa regrowth and soil physical properties. Water infiltration rate and soil penetration resistance were measured following 0, 200, 400, and 600 head d/acre (equivalent to 40 lambs grazing one acre for 0, 5,10, and 15 d, respectively) of grazing in December and January. Alfalfa yield was taken during the 20 April harvest. Water infiltration rates were high (>0.2 in./h) and were not affected by grazing for this irrigated pasture system, which contradicts the results for rangeland. Hoof action by sheep only effected penetrability in the surface 2 in. (P = 0.024). Alfalfa yield was 5.4% greater (P = 0.089) for the grazed vs. the ungrazed plots. We conclude that intensive winter sheep grazing was not detrimental to plants and soils of the irrigated pastures of the Sonoran Desert.

A note on the effect of post-mating stocking rate on reproductive performance of Greyface ewes

Continuously grazed rye grassl clover swards with surface heights of 8 to 10 cm at 5 weeks before a synchronized mating and 7·5 cm at mating were grazed by 151 Greyface ewes stocked at 12 per ha until mating. The effects of two stocking rates (eight and 16 ewes per ha) for 6 weeks over the mating and post-mating period were then studied on live weight, body condition and reproductive peformance. Sward height fell more rapidly post mating when stocked at 16 ewes per ha than at eight ewes per ha, but remained above 3·5 cm until 4 weeks after first mating under both rates. Ewes stocked at 16 per ha became significantly lighter and leaner than ewes stocked at eight per ha. There was no significant effect of post-mating stocking rate on reproductive performance in terms of conception rate and lambing rate to first mating or lambing rate to all matings. Reproductive performance of Greyface ewes is therefore unlikely to be adversely affected by post-mating stocking rate on swards of 7 to 8 cm which do not fall below 3·5 to 4·0 cm until 3 to 4 weeks after mating.

Effects of Stocking Rate and Overseeding with Red Clover on Productivity of Native Pasture Continuously Grazed by Yearling Steers

AbstractOverseeding with red clover (Trifolium pratense L.) and stocking rate are factors that can affect composition and production of hill land pasture. A grazing experiment utilizing yearling beef steers (Bos taurus) was conducted using 3, 4, and 5 yearling steers ha−1 (285 kg), on native pasture (predominantly Poa pratensis L.) overseeded with red clover and non overseeded. Paddocks of 1 ha were continuously set stocked from mid May to the end of Sept. Herbage mass, herbage consumed and the percentage of legumes, grasses, dead material, and non‐leguminous broadleaf plants were recorded. Animals were weighed at the initiation and end of each grazing season and at 4 week intervals. Overseeding increased legume content 4‐fold the seeding year but much of this increase was lost the following year. Herbage mass was greater on overseeded pasture the year following seeding but no effect on animal productivity was found. Stocking rate did not affect percentage legume but the proportions of other broadleaf plants increased at high stocking rates. Average daily gain as well as total gain ha−1 was greatest at 4 steers ha−1.

Nitrogen rate and stocking rate effects on steer gains from grazed irrigated pangola grass in the Ord Valley, Western Australia

Annual liveweight gain of steers grazing flood-irrigated, fertilised pangola grass in the Ord Valley, Western Australia, was modelled as a function of nitrogen rate (90-350 kg/ha) and stocking rate (5.2-12.6 steers/ha). Steer gains decreased linearly with increasing stocking rate (SR) at each nitrogen rate (NR). Increasing NR resulted in higher steer gains, particularly at the low levels of SR. The model predicted an increase in the slope (b values) of the linear relations between steer gains and SR with an increase in NR. As a consequence, SR for maximum gain/ha.year only varied between 6 and 7 steers/ha within the NR used. Responses to SR and NR for gains/ha were both quadratic, and the model predicted a maximum gain of 1266 kg/ha when SR was 6.2 steers/ha and NR was 420 kg/ha.year. Within the experimental range, maximum gain was 1233 kg/ha when SR was 6.6 steers/ha and NR was 350 kg/ha.year. Steer gain varied seasonally, even in this tropical, irrigated environment. Gains were highest in January-March and lowest in June-July. Increasing stocking rate had the greatest depressing effect on liveweight gain during the cool season with b values, for the relation between steer gain and stocking rate at the 220 kg N rate, varying from -1 g/day in November to -94 g/day per unit of SR in July.

A decision support model to evaluate the effects of drought and stocking rate on beef cattle properties in Northern Australia

Beef cattle in northern Australia are raised on extensive pastoral properties in a semi-arid tropical climate subject to droughts. The severity of the effect of drought on cattle depends on the stocking rate. Management of herd size is therefore a compromise between harvesting production in average years and the risk of losses in a drought. The authors report on a spreadsheet model that can be used to evaluate herd performance and cashflow using annual rainfall as the only climate input. The model relies on a proxy for pasture availability derived from annual rainfall and stocking rate. This proxy is used for the estimation of reproduction, mortality and liveweight gain. Economic information is calculated to the level of cashflow The model has been used with groups of pastoralists to evaluate the question of drought and stocking rate in terms of economic risk and deterioration of native pastures. It has also been used in consultations with individual pastoralists to help determine which type, and the number, of cattle that should be sacrificed in a drought.