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.     

Evaluation of veld potential in east griqualand using beef cattle under two grazing management systems

Abstract

Beef production from veld, in the short term, was found to be greater under a continuous grazing system than under a rotational grazing system. Average daily gains decreased from a maximum in late‐spring and the highest three‐year mean value was 0,5 kg/animal/day. Livemass gains/ha were highest at a stocking rate of 2,2 animals/ha and were 131,4 kg/ha under continuous grazing and 88,6 kg/ha under rotational grazing. Estimated mean maximum gains/ha were 0,78 kg/ha/day at a stocking rate of 2,5 animals/ha under continuous grazing and 0,55 kg/ha/day at a stocking rate of 1,7 animals/ha under rotational grazing. However, optimum economic stocking rates were estimated to occur below those where beef production/ha was maximum.     

Effects of eight grazing systems on carcass mass gains of steers grazing irrigated Cynodon aethiopicus pastures

Abstract

Eight grazing systems were compared on irrigated Cynodon aethiopicus pastures which received 650 kg N, 36 kg P and 200 kg dolomitic limestone/ha, annually. There were either one, two, three, six or 18 paddocks in the systems, the single paddock system being continuously grazed. The others were rotational systems with various periods of grazing and of resting.

Using the comparative slaughter technique carcass mass gains of crossbred Hereford/Afrikaner steers were calculated. Three‐year mean carcass mass gains over stocking rates from 12 to 18 steers/ha ranged from 872 to 997 kg/ha. None of the rotational systems were better than continuous grazing.

Estimates of amounts of herbage available for grazing in each system showed that there was least in the continuous grazed and most in the multi‐paddock systems where there were long periods of rest between successive grazing.     

Herbage intake by cattle on tarchonanthus veld in the Northern Cape as affected by stocking rate and grazing system 1

Abstract

In a trial with young Bonsmara cattle, four different stocking rates (10, 7, 6 and 4 ha/large stock unit) were applied in both a rotational and continuous grazing system. Feed intake was estimated during spring, summer, autumn and winter for four consecutive years starting in 1977.

Irrespective of the grazing system, feed intake declined with an increase in stocking rate. On average the highest intake was recorded in January and reached the lowest levels in October and July.

Livemass gain was found to be closely related to feed intake.     

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.     

The influence of stocking rate and grazing system on the crude protein content and digestibility of Tarchonanthus veld in the northern cape 1

Abstract

Four stocking rates (10, 7, 6 and 4 ha/large stock unit), in both rotational and continuous grazing, have been applied with cattle on Tarchonanthus veld. The crude protein content and digestibility of organic matter of handcut samples and herbage samples collected by means of oesophageal fistulated steers in the different treatments, were determined.

The results indicated that the crude protein content (3,9 to 6,7%) and digestibility (48,7 to 59,4%) of handcut samples was not representative of the diet of grazing cattle. The crude protein content of the samples collected by means of oesophageal fistulated steers varied from an average of 13,6%. (October to December) to an average of 5,3% (July and August). On average, the digestibility of the fistula collected samples varied between 60,4% (February to April) and 50,2% (July to October). The crude protein content of the fistula collected samples tended to increase with increasing stocking rate while digestibility declined. Both crude protein content and digestibility of the fistula collected samples did not differ significantly between rotational and continuous grazing.     

Influence of stocking rate and grazing system on plant basal cover and botanical composition of veld in the northern cape 1

Abstract

Changes in basal cover and botanical composition were recorded at four stocking rates, both under continuous and rotational grazing in the Northern Cape. The experiment was conducted with cattle. Results suggested that heavier stocking rates could be applied under rotational grazing than under continuous grazing without veld deterioration occuring. After four seasons, botanical composition deteriorated only under continuous grazing. Plant basal cover decreased significantly at the heavy stocking rates, both under rotational and continuous grazing. This result illustrates the danger of grazing strategies based on an injudicious increase in stock numbers.

Basal cover was found to be a better indicator of trends in veld condition than botanical composition, despite annual fluctuations resulting from rainfall variability. Changes in the botanical composition apparently occur only where veld deterioration is more advanced.     

Influence of grazing management on the production of an irrigated grass/legume pasture in the Rûens area of the Southern cape

Abstract

The production of an irrigated grass/legume pasture was determined using Merino ewes on rotational and continuous grazing systems. The clover content of the pasture declined, while the grass content increased under both systems. The lucerne content of the rotationally‐grazed pastures did not change, but lucerne failed to persist under continuous grazing. Rotational grazing resulted in a lower clover content and, consequently, in a lower production per individual animal at low stocking rates during two seasons, but in a higher pasture production and grazing capacity, than under continuous grazing. At high stocking rates the individual animal production was, however, highest under rotational grazing, resulting in a higher animal production per ha than under continuous grazing.     

Nitrogen fertilization,stocking rate and rotational grazing effects on steers grazing Pennisetum clandestinum

Kikuyu pastures at the Ukulinga research farm near Pietermaritzburg were fertilized with 150 and 300 kg nitrogen (N) ha^?1 in the summer periods of 1985–86 and 1986–87, and were continuously grazed with steers at stocking rates of 5.4, 8.0 and 10.7 steers ha^?1. In the second season the high N level pasture was also grazed under 12‐paddock rotational grazing at stocking rates of 5.4, 8.0 and 13.4 steers ha^?1. In the first season the high N level provided higher (P≤0.05) animal weight gains, but there was no difference between N levels in animal weight gain during the second season. Rotational grazing provided higher weight gains than continuous grazing in the second season. The increased weight gains obtained from high N fertilization and rotational grazing were probably caused by higher forage availability rather than higher forage quality.     

A model for predicting livemass gain from stocking rate and annual rainfall

Abstract

The relationship between livemass gain and stocking rate was established for young beef animals grazing kikuyu and Coastcross II pastures in each of five grazing seasons. The annual rainfall within these seasons ranged from 506 mm to 990 mm. Relationships between pasture production variables and annual rainfall are described and these are used to construct a model for predicting livemass gain/ha/season for different stocking rates and levels of annual rainfall.     

Grassland research priorities: Ideas for the future

Abstract

Four levels of available dry matter (DM) were maintained on a continuously grazed irrigated Midmar Italian ryegrass (Lolium multiflorum Lam.) pasture by means of a “put‐and‐take” grazing procedure. The pasture was stocked with three successive sets of weaned lambs in winter, spring and early summer respectively. The relation between average daily gains (ADG) and available DM was positively linear At equivalent levels of available DM, gains were greater in spring than in either the winter and summer periods (P ≤0,01), but there were no differences in gains between winter and summer. There was a negative linear relation between average stocking rate (the rate required to achieve a given level of herbage availability) and available DM. Stocking rates in spring and summer were not significantly different, but both were higher (P≤0,01) than those in winter. Within the range of the differential treatments applied, relations between stocking rate and ADG were negatively linear, and there was an interactive effect (P≤0,01) between stocking rate and grazing period. Changes in ADG with a unit change in stocking rate were greatest in winter, intermediate in summer and least in spring. Gains/ha were curvilinearly related to available DM. The curves indicate that the amounts of available DM required for maximum gains/ha were least in spring, intermediate in summer and greatest in winter.

From a serial cutting trial conducted concurrently with the grazing, a growth rate curve was developed for Midmar ryegrass. This curve had two maxima, with the maximum growth rate in spring being more than double that in autumn. The in vitro digestible organic matter content and crude protein content decreased from 80,6% and 24,1% in autumn to 63,1% and 10,6%, respectively, in summer. Crude fibre content increased from 10,1 % in autumn to 30,1 % in summer.     

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.     

Cattle performance and production when grazing Bermudagrass at two forage mass levels in the southern Piedmont

Performance and production of growing cattle (Bos taurus) on Coastal Bermudagrass [Cynodon dactylon (L.) Pers.] pasture are affected by forage allowance, but possible interactions with fertilizer nutrient source (i.e., inorganic vs. organic) and time have not been well described. We evaluated the effects of 3 nutrient sources with equivalent N rates: 1) inorganic, 2) crimson clover (Trifolium incarnatum L.) cover crop plus inorganic, and 3) chicken (Gallus gallus) broiler litter, factorially arranged with 2 residual forage mass levels [grazing to maintain high (4,528 +/- 1,803 kg/ha) and low (2,538 +/- 1,264 kg/ha) forage mass], on cattle stocking density, ADG, and BW gain during 5 consecutive summer grazing seasons. Across grazing seasons, residual forage mass and nutrient source both affected response variables, but interactions between these variables were rarely significant (P < or = 0.10). Across grazing seasons and nutrient sources, increasing grazing pressure to maintain a lower forage mass reduced ADG (0.67 vs. 0.88 kg/d; P < 0.001) but increased BW gain/ha (726 vs. 578 kg/ha; P < 0.001) due to greater stocking density (8.7 vs. 5.8 steers/ha, P < 0.001; mean BW of growing Angus steers of 212 kg). Inorganic fertilization led to greater stocking density than other nutrient sources (8.2 vs. 6.8 steers/ha, P < 0.001) because of greater forage production. Stocking density to achieve the 2 targeted forage mass levels was widely different during the initial grazing seasons of the study but nearly similar at the end of 5 yr. Cattle performance tended to decline with time during each grazing season under both residual forage mass levels, perhaps as a result of declining forage quality, because performance was positively associated with grazing season precipitation under high forage mass. Steer BW gain/ha was greater (P < 0.05) with lower forage mass early in the grazing season of all years but not necessarily later in the grazing season. Steer BW gain/ha was also greater (P < 0.05) with a lower forage mass during the early years of the study but was similar during the later years of the study. Significant variations in cattle performance and production with time confirmed the short-term seasonal effects but suggested that the long-term effects may also be of importance in maintaining productivity and environmental quality of grazed pastures.     

Recent trends in grazing management philosophy in South Africa

Abstract

Reasoned argument by researchers in veld management in South Africa and elsewhere has not generally supported a number of contentious recommendations made in recent years in the popular and semi‐popular press. The only major changes to general management thinking has been that high performance grazing (or controlled selective grazing) is, except for a few notable exceptions, more appropriate than high utilisation grazing (non selective grazing). In contrast, considerably more evidence has emerged to support the general philosophy which has built up over the years on such issues as optimum stocking rates, periods of absence, stocking densities and the required number of camps in grazing layouts.     

Evaluation of the grazing potential of grass species in Tarchonanthus veld of the northern cape 1

Abstract

The grazing value of the seven most prominent grass species in Tarchonanthus‐limeveld was investigated from 1977 to 1981.

The frequency of utilization of Chrysopogon serrulatus was exceptionally high (93%), while Sporobolus fimbriatus, Themeda triandra and Digitaria seriata were intermediate (50–60%) followed by Cymbopogon plurinodis (34%). Eragrotis lehmanniana and Fingerhuthia africana were poorly grazed (12 to 16%). The utilization of species was influenced by stocking rate. Statistical differences between species indicated a relatively high biomass production (600 to 740 g DM/m² per year) for E. lehmanniana, C. plurinodis and T. triandra, while F. africana, S. fimbriatus and D. seriata were intermediate (320 to 420 g DM/m² per year). E. lehmanniana, C. plurinodis and T. triandra produced the highest above‐ground phytomass, but had a lower crude protein content (2,9 to 7,4%) and digestibility (46,1 to 61,3%) than the other four species (3,8 to 9,7% crude protein and 50,5 to 68,4% digestibility).     

Stocking rate and the productivity of Rhodes grass pastures on the Lilongwe plain,Malawi

An experiment was undertaken over three wet (summer) seasons to investigate the effects of different set stocking rates on animal performance from fertilised Rhodes grass pastures. The three set stocking rates were 2.5, 5 and 7.5 livestock-units/ha (1 livestock unit=342 kg liveweight). Pasture productivity was related to stocking intensity. Animal gain per hectare was directly related to stocking rate. Gain per animal, gain per livestock unit and number of grazing days were all inversely proportional to stocking rate. Animals on the low stocking rate were carried through almost to the end of the dry (winter) season with only small changes in liveweight. The practical significance of the results is discussed.     

Estimates of carrying capacity and production from herbage yields and grazing days

The reliable prediction, from herbage yields, of the carrying capacity of grazing can be of value in farm planning.

In a trial comprising 27 treatment combinations of fertilization and stocking rate under two systems of grazing, it appeared that animal production per unit area can be predicted from herbage yields and from grazing days. It was apparent, however, that the method, and consequent intensity, of utilization influenced the angle of the regression line. Furthermore, it appeared that herbage yield allowed a fair estimate to be made of the carrying capacity provided stocking rates were at an optimum level.     

Dry matter yield of herbaceous rangeland plants and livemass gain of Tswana steers in eastern Botswana in response to stocking rate and phosphorus supplementation

Abstract

Tswana steers were continuously grazed at stocking rates of 3, 6, and 9 ha LSU^‐1 in two blocks, and steers in one block were supplemented with phosphorus. Dry matter yield of herbaceous rangeland plants was measured at the end of each growing season from 1984 to 1990 except in 1986, whilst steer livemass was measured monthly. Steers entered the trial at the beginning of the growing season and remained on the trial for three years and two groups of steers were evaluated in the study. Dry matter yield of Digitaria spp. and annual grasses showed no response to stocking rate. Panicum maximum and Eragrostis rigidior were the most responsive species, increasing with a decreased stocking rate. Phosphorus supplement was advantageous during drought periods at stocking rates higher than 9 ha LSU^‐1. Livemass gain increased with decreased stocking rate regardless of phosphorus supplement.     

“n Voorlopige evaluasie van eenjarige,wintergroen weidings met speenlammers,in die Oos‐Kaapse suurveld

A preliminary evaluation of annual, wintergreen pastures using weaned lambs in the eastern Cape sourveld. Animal production and feed availability on oats, vetch and oats/vetch pastures were evaluated under continuous grazing, at three stocking rates, using weaned lambs. The oats and oats/vetch mixture generally produced significantly more available above‐ground phytomass (AAP) than the vetch pasture. No significant differences in AAP or average daily gain (ADG) were measured between stocking rates on the different pastures. The levels of food availability and animal production obtained with the different pastures indicate that oats, vetch and an oats/vetch mixture can be used as annual, wintergreen pastures in the eastern Cape sourveld. However, the stocking rates that were implemented were too low to determine the production potential of the different pastures and an evaluation of the pastures at higher stocking rates is recommended before any recommendation on optimal stocking rates can be made.     

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。