Productivity of beef cattle grazing Brachiaria brizantha cv. Marandu with and without nitrogen fertilizer application or mixed pastures with the legume Desmodium ovalifolium

The use of forage legumes to contribute biologically fixed nitrogen (N) to pastures is an alternative to increase beef cattle production in tropical regions. The objective was to compare the impact of the introduction of a legume with that of N fertilizer application on forage and animal production in Brachiaria pastures. This two-year study assessed three pasture treatments: (1) mixed Marandu palisadegrass (Brachiaria brizantha [syn. Urochloa brizantha] cv. Marandu) and the legume “ovalifolium” (Desmodium ovalifolium) cv. Itabela (Mixed), (2) Marandu palisadegrass pastures with 150 kg N ha⁻¹ (Fertilized), and (3) Marandu palisadegrass without N fertilizer (Unfertilized). Rotational stocking with a variable stocking rate was used with a target herbage allowance of 1.0 kg forage kg body weight⁻¹. The pre-grazing green herbage mass was similar for Fertilized and Mixed pastures, with 54% and 63% more mass than Unfertilized pasture, respectively (p < .001). Cattle that grazed the fertilized pasture had the greatest average daily gain (ADG; p = .017). The stocking rate and liveweight gain per area were greatest for the Fertilized and Mixed pastures (p < .001 and p < .001, respectively). No differences between treatments were found for DM forage intake (p = .555). Organic matter digestibility was lowest (p < .001) for the Mixed pasture. The inclusion of the ovalifolium legume in the Marandu pasture had the same impact on beef cattle production as annual fertilization with 150 kg N ha⁻¹. The potential and environmental benefits of ovalifolium are discussed.     

Production of beef cattle grazing on Brachiaria brizantha (Marandu grass)—Arachis pintoi (forage peanut cv. Belomonte) mixtures exceeded that on grass monocultures fertilized with 120 kg N/ha

Mixed grass/legume pastures are an alternative to grass monocultures for increased beef cattle production in tropical climates. The objective of this study was to evaluate the productivity of beef cattle grazing either a mixed pasture of Brachiaria brizantha cv. Marandu grass and Arachis pintoi (forage peanut) cv. Belomonte or a Marandu monoculture, under rotational stocking. Five trials were conducted over a period of nine years in north-eastern Brazil where the sward structure (forage, grass and legume mass) and animal performance were compared for a mixed Marandu grass/forage peanut pasture, and a Marandu grass monoculture with 120 kg N ha⁻¹ y⁻¹. Stocking rate was adjusted to maintain forage allowance at 4% body weight/day. A block design was used with four replicates, and warm and cool seasons within each trial were considered, using repeated measurements over time. In the warm season, the forage mass in the mixed pastures was 17% greater than in the monoculture (p = .049), and the stocking rate, average daily gain and liveweight gain per ha were 16.4%, 20.0% and 28.7% greater (p = .004, p < .001 and p < .001 respectively). The average daily gain showed a positive linear relationship with the legume proportion in the sward (p < .001). The mixed forage peanut/Marandu pasture sustained significantly greater beef cattle production (789 kg ha⁻¹ y⁻¹) compared to the N-fertilized grass monoculture (655 kg ha⁻¹ y⁻¹). Appropriately managed, mixed pastures of forage peanut/Brachiaria pastures are sustainable and have high potential for use in the humid tropics.     

Maintaining post‐grazing sward height of Panicum maximum (cv. Mombaça) at 50 cm led to higher animal performance compared with post‐grazing height of 30 cm

In swards of tall, tufted, tropical grasses like Mombaça guinea grass (Panicum maximum (Jacq.)), post‐grazing heights promote changes in sward structure, which influence animal performance. This study evaluated changes in sward structure in response to grazing management at two post‐grazing heights (30 and 50 cm), associated with 90 cm pre‐grazing height. Each treatment was allocated to experimental unit (1.5 ha) in three replicated blocks. Pastures were evaluated pre‐ and post‐grazing to estimate herbage mass, percentages of leaf (LP), stem (SP) and dead material (DP), and nutritive value (VN). Stocking rate was adjusted twice a week “using the put‐and‐take approach,” and animals were weighed every 28 days. Forage accumulation rate was greater for pasture managed at 30 cm (64.8 vs. 55.1 kg ha^?1 day^?1) than 50 cm. A greater number of days were required after grazing 30‐cm residual pasture to achieve the pre‐grazing target height, resulting in 25% decrease in number of grazing cycles compared with pastures managed at 50 cm. Regardless of post‐grazing height targets, SP and DP decreased, whereas LP and NV increased from soil level to top of canopy. Stocking rate was greater in pastures managed to 30 cm than in those managed to 50 cm residual height (4.7 vs. 3.4 AU ha^?1). However, average daily gain was greater for 50 cm than for 30 cm post‐grazing height (795 vs. 590 g steer^?1 day^?1), resulting in a greater animal production per area (917 vs. 794 kg/ha of live weight). Thus, Mombaça guinea grass subject to intermittent grazing should be managed at 50 cm residual height.     

Forage and animal production on palisadegrass pastures growing in monoculture or as a component of integrated crop–livestock–forestry systems

To meet the global demand for animal protein, sustainable intensification of existing livestock systems may be possible, especially through integration of livestock with crops or forestry. Thus, our objective was to compare forage production and animal performance in grass monoculture and integrated systems in the Brazilian Amazon biome. The four systems were (a) livestock (L) with Marandu palisadegrass {Brachiaria brizantha (Hochst. ex A. Rich.) R. D. Webster} as monoculture, (b) palisadegrass pastures integrated with eucalyptus trees (Eucalyptus urograndis; hybrid of Eucalyptus grandis W. Hill ex Maiden and Eucalyptus urophylla S. T. Blake) arranged in three‐row groves with groves spaced 30 m apart (livestock–forestry; LF), (c) palisadegrass after two years of crops (crop–livestock; CL) and (d) palisadegrass after two years of crops with single rows of eucalyptus trees spaced 37 m apart (crop–livestock–forestry; CLF). From July 2016 to July 2017, all experimental units were continuously stocked using a variable stocking rate. Greater herbage accumulation (HA) occurred in CL and CLF in comparison with L and LF (21,310, 24,050, 19,500 and 18,890 kg DM/ha respectively). The gain per hectare of L, LF and CL (average of 932 kg ha^–1) was less than CLF (1,190 kg ha^–1). Average daily gain was similar among systems (0.69 kg/day). We conclude that integrated systems can support similar (LF or CL) or greater (CLF) levels of animal production than palisadegrass monocultures while increasing diversity of outputs, thereby providing a greater range of viable systems for livestock production in the Brazilian Amazon biome.     

Mixtures of grasses: An alternative to traditional pasture monocultures in the tropics

A two-year experiment assessed herbage production and above- and below-ground characteristics of a highly productive monoculture (‘BRS Zuri’ guineagrass [Panicum maximum Jacq.]) and two mixtures of three grasses (Mixture 1: ‘BRS Zuri’ guineagrass, ‘BRS Xaraés’ palisadegrass [Brachiaria brizantha Stapf.], and ‘Basilisk’ signalgrass [Brachiaria decumbens Stapf.]; Mixture 2: ‘BRS Quênia’ guineagrass [Panicum maximum Jacq.], ‘Marandu’ palisadegrass [Brachiaria brizantha Stapf.], and ‘BRS Paiaguás’ palisadegrass [Brachiaria brizantha Stapf.]), cultivated in the Brazilian tropical savanna. Mixtures 1 and 2 were subjected to two grazing intensities (removal of 40 or 60% of pre-grazing height) and ‘BRS Zuri’ guineagrass monoculture was defoliated to a single grazing intensity of 50%. Treatments were randomly assigned to fifteen 0.25-ha plots and managed under intermittent stocking by cattle. Herbage accumulation rate was similar among pastures and years (p > .1). The root mass in the tussocks did not differ (p > .1), with mean values ranging between 0.62 to 1.81 kg DM m⁻². Root density in the tussock interspaces was greater in the mixtures (p < .001), regardless of seasons (p = .405) and years (p = .292). The mixtures were dominated by guineagrass (70%) and palisadegrass (30%) at the end of the experiment, with the population of ‘Basilisk’ and ‘BRS Paiaguás’ being completely suppressed throughout the experimental period. Mixing guineagrass and brachiariagrasses can be an alternative to the traditional pastoral systems in the tropics, as it does not compromise herbage production and presents a capacity to produce more roots than a very productive monoculture of ‘BRS Zuri’ guineagrass.     

Impact of deferred grazing and fertilizer on herbage production,soil seed reserve and nutritive value of native pastures in steep hill country of southern Australia

Developing sustainable grazing management systems based on perennial species is critical to preventing land degradation in marginal land classes. A field study was conducted from 2002 to 2006 to identify the impacts of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on herbage accumulation, soil seed reserve and nutritive value in a hill pasture in western Victoria, Australia. Three deferred grazing strategies were used: short‐term deferred grazing (no defoliation between October and January), long‐term deferred grazing (no defoliation from October to the autumn break) and optimized deferred grazing (withholding time from grazing commenced between annual grass stem elongation and seed head emergence and concluded in February/March). These treatments were applied with two fertilizer levels (with or without fertilizer at 50 kg phosphorus ha^?1 and 2000 kg lime ha^?1 applied in year 1 only) in a factorial arrangement and two additional treatments: continuous grazing (CG) and no grazing (NG) in year 1. The deferred grazing treatments on average produced herbage dry matter of 4773 kg ha^?1, the NG produced 4583 kg ha^?1 and the CG produced 3183 kg ha^?1 in year 4 (2005–06) of the experiment. Deferred grazing treatments with and without fertilizer application produced an average of 5135 and 4411 kg DM ha^?1 respectively. Averaged over 4 years, deferred grazing increased the germinable seed pool of perennial grasses by 200% and annual grasses by 50% (except optimized deferred grazing that considerably decreased the annual grass seed pool) compared with the CG. The best of the deferred grazing strategies increased the digestibility of pastures by 7% compared with the CG. The results demonstrated that deferred grazing from spring to autumn followed by rotational grazing could be an effective tool to increase herbage production and soil seed pool and improve the digestibility of native pastures in the steep hill country of southern Australia.     

The role of the legume in the nitrogen cycle of productive and sustainable pastures

The role of the legume in the nitrogen (N) cycle was examined in grazed pastures receiving no N fertilizer of both temperate and tropical regions by simulating the fluxes of N through different processes of the cycle. The amounts of legume-fixed N required to balance the cycle without invoking a drain on soil organic N reserves (i.e. no net N mineralization) was estimated to vary from 38 to 53% of the above-ground herbage N or from 20 to 31% on a dry matter (DM) basis for tropical pasture systems with a range of pasture utilization of 10–40%. At higher pasture utilization levels of 50-70%, more typical of intensively grazed temperate pastures, the N input requirement in the absence of fertilizer N would be 57-67% of the aboveground herbage N or 35-45% DM. An examination of the role of each contributory process of recycling (viz. excreta returns, internal cycling or remobilization from senescing tissues, litter decomposition) suggests that variations in the amounts of internally cycled N would have the greatest impact on the requirement for biologically fixed N at low levels of pasture utilization (10-40%), while at high pasture utilization levels of 70%, variations in the recovery of excreta-N would have a major effect on the requirement for fixed-N to balance the cycle. The amounts of biologically fixed N required to sustain a range of herbage DM yields of 3-22 t DM ha ^?1 yr^?1 would range from 15 to 158 kg N ha^?1 yr^?1 for tropical pastures. For intensively managed temperate pastures producing 6-15 t DM ha^?1 yr^?1 with a N content of 3·5%, a range of fixation of 120-352 kg N ha^?1 yr^?1 is required. These simulations indicate how legume contents of 20-45% of herbage DM could contribute to productive and sustainable (in terms of N) pasture systems of both temperate and tropical regions     

Effects of incorporating cowpea in a subtropical grass pasture on forage production and quality and the performance of cows and calves

The increasing cost of N fertilizer has stimulated an interest in sourcing protein from warm‐season legumes among beef cattle producers in the tropical/subtropical areas of the world. The objective of this study was to evaluate effects of two strategies of incorporating cowpea [Vigna unguiculata (L.) Walp.] into bahiagrass (Paspalum notatum Flügge) pastures on the herbage characteristics and performance of grazing cow–calf pairs. The study was conducted in Ona, Florida, USA, from May to August in 2007 and 2008. Experimental units were 1·0 ha. Treatments were bahiagrass pasture alone (control), 50:50 bahiagrass–cowpea pasture (cowpea), bahiagrass pasture with a cowpea creep grazing area (0·1 ha, creep grazing) and bahiagrass pasture with a creep‐fed concentrate [(creep feeding; 10 g kg^?1 body weight (BW)]. The cowpea pastures had lower herbage mass [HM, 1·8 vs. 3·7 t ha^?1] and herbage allowance [HA, 0·8 vs. 1·4 kg DM kg^?1 live weight (LW)] compared with the other treatments. Cowpea had greater CP (CP, 160 g kg^?1) and in vitro digestible organic matter (IVDOM), (600 g kg^?1) than bahiagrass (110 and 490 g kg^?1 respectively); however, cowpea HM was only 0·9 t ha^?1 in May and 0·7 t ha^?1 in June, but it did not persist in July and August. Calves receiving the creep feeding treatments had greater average daily gain (0·8 vs. 0·7 kg d^?1) than calves in other treatments. Further research is necessary to exploit the superior nutritive value of cowpea in grazing systems in the south‐eastern USA.     

A comparison of conventional and automatic milking system pasture utilization and pre‐ and post‐grazing pasture mass

Automatic milking systems (AMS) present an opportunity for dairy farmers to not only improve their lifestyle and conditions of work, but also save on labour costs and/or increase the time available to focus on overall farm management. However, the viability of AMS will rely on achieving high levels of pasture utilization. Well‐established pasture management principles are implemented on many conventional milking system (CMS) farms and high levels of pasture utilization are achieved; however, the ability to follow these same principles on AMS is unknown. This study compared levels of pasture utilization and pre‐ and post‐grazing pasture mass between AMS and CMS farms at the same site when managed by the same pasture management principles. From 1 March 2007 to 29 February 2008, pre‐ and post‐grazing compressed height, milk yield and milk composition data were collected for two CMS farms and one AMS farm at the Elizabeth Macarthur Agricultural Institute, Camden, Australia. Despite differences in pre‐ and post‐ grazing pasture mass between milking systems, pre‐grazing mass was predominantly maintained within the bounds of 2200 and 2500 kg DM ha^?1 and post‐grazing mass between 1400 and 1500 kg DM ha^?1 (5–6 cm height). Similar levels of pasture utilization (mean 13 500 kg DM ha^?1 year^?1) were recorded between AMS and CMS farms. These findings highlight the ability to follow established grazing management principles and achieve high levels of pasture utilization on pasture‐based AMS farms.     

Defoliation patterns and their implications for the management of vegetative tropical pastures to control intake and diet quality by cattle

This study assessed the use of pasture attributes to control daily intake and diet quality during progressive defoliation on pastures of Axonopus catarinensis. Three consecutive 12‐day grazing treatments of progressive defoliation were conducted with Brahman cross‐steers. Daily forage intake and defoliation dynamics were assessed using a pasture‐based method. The treatments differed in initial sward height (33, 44 and 61 cm) and herbage mass (1030, 1740 and 2240 kg ha^?1). The post‐grazing residual sward height, at which forage intake decreased, appeared to increase with the initial sward height (12·3, 14·6 and 15·5 cm). Steers grazed up to four distinctive grazing strata in all treatments. The depth and herbage mass content of the top grazing stratum were at least five times higher than the lower grazing strata in all treatments. This explains why forage intake decreased when the top grazing stratum was removed in approximately 93% of the pasture area in all treatments, equivalent to approximately 7% of the pasture area remaining ungrazed. We conclude that the residual ungrazed area of the pasture, rather than residual sward height, can be used to develop grazing management strategies to control forage intake and diet quality in a wide range of pasture conditions.     

The effect of grazing versus cutting on dry matter production of multispecies and perennial ryegrass‐only swards

Dry matter (DM) production of multispecies swards compared to perennial ryegrass (Lolium perenne; PRG) swards under intensive grazing warrants investigation as it is relatively unknown. A 5 × 2 factorial experiment, with five sward types and two defoliation methods, was used to investigate the effect of grazing versus cutting on dry matter (DM) production of multispecies and PRG‐only swards. Five sward types were established namely: a PRG‐only sward, receiving 250 kg N ha^?1 year^?1 (PRG250), and a PRG‐only sward (PRG90), a two‐species sward with PRG and white clover (Trifolium repens; PRGWC), a six‐species sward (6S) and a nine‐species sward (9S), each receiving 90 kg N ha^?1 year^?1. Cutting plots measured 1.95 × 10 m and grazing plots measured 10 × 10 m. All plots were harvested concurrently every 21–30 days from April‐November for two years (2015 and 2016). A strip from the grazing plots was cut for DM yield determination prior to turning in cattle for grazing. There was an interaction between sward type and defoliation method (p < .01), whereby there was no effect of defoliation method on the PRG‐only swards, however, the annual DM production of PRGWC, 6S and 9S swards reduced under grazing compared to cutting (p < .001; on average 1,929 kg DM/ha lower). Multispecies swards had lower DM production under grazing compared to cutting, while the DM yield of PRG‐only swards was unaffected by defoliation method.     

Canopy characteristics and tillering dynamics of Marandu palisade grass pastures in the rainy–dry transition season

The objective of this study was to evaluate the effect of pasture management during the rainy–dry transition season in Jaboticabal, Brazil, on the structural and tillering characteristics of Marandu palisade grass. The treatments were as follows: 15 cm sward height in the rainy season and ungrazed in the rainy–dry transition season (15/0); 25 cm sward height during the rainy season and fixed stocking rate of 2·5 AU ha^?1 during the rainy–dry transition season (25/2·5); and 35 cm sward height in the rainy season and fixed stocking rate of 2·5 AU ha^?1 in the rainy–dry transition season (35/2·5). There were more herbage mass, stem and dead herbage mass in treatments 25/2·5 and 35/2·5 than 15/0. Tiller appearance rate was greater in treatment 15/0 and tiller mortality rate was higher in treatment 35/2·5 compared to treatment 15/0. Tiller population stability index was 1 in treatment 15/0 and lower in treatment 35/2·5. Although treatment 15/0 showed favourable structural and tillering characteristics, it also has the lowest herbage mass. Treatment 25/2·5 can be regarded as an adequate management strategy for Marandu palisade grass, since it has similar herbage mass and better tillering characteristics than treatment 35/2·5.     

The long-term effects of a range of pasture treatments applied to three semi-natural hill grassland communities. 1. Pasture production and botanical composition

Five pasture treatments: (1) controlled grazing, (2) controlled grazing + lime, (3) controlled grazing + lime + phosphate, (4) controlled grazing + lime + phosphate + oversown white clover and (5) controlled grazing + lime + phosphate + oversown white clover + oversown perennial ryegrass were applied to three semi-natural hill grassland communities. The communities were those dominated by Agrostis/Festuca, Molinia and Nardus. The proportion of Nardus at the Nardus-dominant site was substantially reduced by herbicide before treatments were applied. All treatments were grazed simultaneously by mature wether sheep on three occasions each year. There were two grazing periods each of 4 weeks duration between mid-May and mid-August with a further grazing period of 3 weeks starting mid-October. During each grazing period stock numbers were set so that a residual herbage mass of 560 kg DM ha ^?1 remained at the end of the grazing period. Measurements of net herbage accumulation (NHA) were made annually over a period of 13 years at each site. The green:dead ratio of grasses, species composition of the pasture and the pH of the soil were measured at intervals during the experiment. Estimates of mean annual NHA ranged from 3860 kg DM ha^?1 for treatment 1 (controlled grazing) to 5170 kg DM ha^?1 for treatment 5 (oversown white clover and perennial ryegrass). The application of lime and phosphate increased annual NHA by 300–350 kg DM ha^?1 with a further increase of around 400 kg DM ha^?1 when white clover was sown. Increases in NHA between year 1 and year 13 ranged from 30% for treatment 1 to around 55% for treatment 5. Although there was no difference in the mean NHA between sites, the herbage from the Agrostis/Festuca site contained a higher proportion of green grass and white clover than that from the other sites. The highest levels of green grass and white clover were found on the oversown treatments at each site. The grazing pressure exerted produced relatively little change in the botanical composition at the Agrostis/Festuca site. At the Molinia-dominant site the Molinia was largely replaced by Nardus during the first 6 years and Nardus also increased in cover at the Nardus site. Application of lime and phosphate generally increased the proportion of Poa pratensis, Festuca rubra and Agrotis tenuis but did not halt the spread of Nardus at the Molinia and Nardus sites. White clover and perennial ryegrass were successfully introduced by oversowing and proportions remained high throughout the 13 years. The cover by bryophyte spp. increased at all sites with the greatest increases occurring in each case on the less comprehensive pasture treatments. These results suggest that on Agrostis/Festuca-dominant pastures herbage biomass production can be increased with relatively low-cost pasture treatments while maintaining Species diversity. However, Nardus and Molinia dominant pastures are likely to require more comprehensive pasture treatments involving sown grasses and white clover to provide herbage of acceptable quality and avoid an increase in Nardus and bryophytes in the sward. With a regime of episodic summer grazing and the addition of fertilizers oversown pastures can be maintained over long periods of time.     

Tiller size/density compensation in temperate climate grasses grown in monoculture or in intercropping systems under intermittent grazing

Oat and ryegrass intercropping in pastures is widely used in regions with subtropical climates. The aim of this study was to evaluate the tiller size/density compensation mechanisms in monoculture and intercropping swards of black oats (Avena strigosa Schreb cv. IAPAR 61) and annual ryegrass (Lolium multiflorum Lam. cv common) under intermittent grazing. Treatments (black oat, annual ryegrass and their mixture) were assigned according to a complete randomized block design with four replicates. Ryegrass, oat and intercropped pastures were grazed when the swards reached a height of 17, 25 and 23 cm, respectively, and with a level of defoliation of 40%. The aerial biomass was determined with a rising plate meter, and the tiller population density (TPD) was estimated by counting tillers in three 10 cm diameter PVC rings per paddock. The mass per tiller was estimated based on the aerial biomass and the TPD of each paddock. Total herbage production did not differ among treatments, with values around 7400 kg DM ha^?1. TPD decreased and mass per tiller increased linearly in the monoculture treatments. Tiller size/density compensation was observed in the three plant communities (treatments) according to the self‐thinning rule. In addition, no relationships were found when each species was analysed individually in the intercrop treatment. The results suggest that species in grass mixed swards adjust their population to keep a relatively constant leaf area index (LAI) over the grazing seasons, and that would help pastures to stabilize herbage production.     

An economically based evaluation index for perennial and short‐term ryegrasses in New Zealand dairy farm systems

Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs (Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs ($ ha^?1 calculated as change in operating profit divided by unit change of the trait) for additional DM produced in different seasons of the year in four regions. The EV of early spring DM was consistently high across all regions, whereas EV for late spring DM was moderate to low. Genotype × environment analysis revealed significant reranking of DM yield among ryegrass cultivars across regions. Hence, separate performance values (PVs) were calculated for two mega‐environments and then combined with the corresponding season and region EV to calculate the overall EV for twenty‐three perennial ryegrass and fifteen short‐term ryegrass cultivars. The difference in operating profit between the highest ranked and lowest ranked perennial ryegrass cultivar ranged from $556 ha^?1 to $863 ha^?1 year^?1 depending on region. For short‐term ryegrasses used for winter feed, the corresponding range was $394 to $478 ha^?1 year^?1. Using PV for DM yield, it was estimated that plant improvement in perennial ryegrass has added $12–$18 ha^?1 year^?1 (depending on region) operating profit on dairy farms since the mid‐1960s.     

The estimation of herbage mass of perennial ryegrass swards: a comparative evaluation of a rising-plate meter and a single-probe capacitance meter calibrated at and above ground level

A rising-plate meter and a single-probe capacitance meter were calibrated on perennial ryegrass swards (cultivars S23, Endura, Melle) over the spring and summer (13 March to 14 September 1981). The swards were rotationally grazed by cattle and from mid-June onwards they were irrigated and cut at 5 cm after grazing to remove rejected herbage. Linear regressions were calculated relating meter readings to herbage dry matter mass as measured by cutting 0–2 m² quadrats to either 18 mm above ground or to ground level. The regression for the rising-plate meter was constant over the spring (slope 275 kg DM ha^?1 cm^?1) and again over the summer (slope 385 kg DM ha^?1 cm^?1). The regression for the capacitance meter changed slightly over the spring (slope 11.2 to 14.0 kg DM ha^?1 unit reading^?1) and was also constant over the summer (slope 20.3 kg DM ha^?1 unit reading ^?1). Correlation coefficients were always above 09 and residual standard deviations ranged from 258–525 in Spring up to 636–918 kg DM ha^?1 in summer. Residual standard deviations were lower with the plate meter than with the capacitance meter and were lower with the above-ground cutting height. Neither meter was able to give accurate results with tall rejected herbage containing a build-up of senescent material. Herbage mass below 18 mm was greater on summer than spring swards. When compared with a ground level cut. cutting above ground underestimated herbage mass on summer relative to spring swards; there was also a tendency to underestimate herbage mass on tall pastures relative to short pastures. There was no evidence of a curved relationship between herbage mass and meter reading with either meter and both meters gave readings related to herbage dry matter mass rather than mass of green herbage or water.     

Forage intake and nitrogen metabolism of beef cattle grazing palisadegrass-calopo mixed pasture managed using canopy light interception

To define the best grazing management strategy, it is important to assess animals' responses to variations in the structure and composition of tropical forages. This 2-year study evaluated animal response to Marandu palisadegrass (Urochloa brizantha)-calopo (Calopogonium mucunoides) mixed pastures managed under rotational grazing. Treatments consisted of three defoliation frequencies defined by rest periods interrupted at 90% (90LI), 95% (95LI) and 100% (100LI) of photosynthetically active radiation interception (LI). The stubble post-grazing height target was 15 cm. Statistical difference was declared at p < .10. The 100LI had lowest crude protein (CP) and in vitro dry matter digestibility (IVDDM) for the Marandu palisadegrass (p = <.001 both) and calopo (p = .003 and p = .067, respectively). Also, the OM digestibility decreased 7.0% in the 100LI condition than 90LI and 95LI treatment (p = .005). There was no difference in forage, grass, and legume intakes between the treatments (p > .10). The 100LI treatment decreased CP intake from grass in 33.3% (p = <.001) compared to other treatments. Greatest production of microbial N (p = .093) occurred with the 90LI treatment. The CP/digestible organic matter (DOM) ratio, urinary N excretion and retained N were lowest in the 100LI treatment (p = <.001, p = .007 and p = .014, respectively). The recommendation for grazing between 90 and 95% of LI is recommended because of greater CP intake and N utilization for the animals and improved the nutritive value of Marandu palisadegrass and calopo mixed pastures.     

Effect of different grazing management systems on the herbage mass and pasture height of a Nardus stricta grassland in western Scotland, United Kingdom

The aims of this study were to examine the effect of three grazing treatments (year‐round stocking rates of 0·8 ewes ha^?1, 0·5 ewes ha^?1 and 0·5 ewes ha^?1 plus grazing cattle in summer), imposed for 4 years, on the herbage mass and surface height of a Nardus stricta‐dominated grassland in western Scotland and to obtain estimates of annual productivity of this grassland. Nardus stricta‐dominated grassland comprised proportionately 0·20 of the grazing area. Stocking rate of sheep had no significant effect on the herbage mass of the grassland in the first 2 years of the experiment, although mean summer pasture heights were significantly higher under the lower stocking rate of sheep. The pasture on the treatment with cattle grazing in summer had a significantly lower herbage mass and lower surface height than the two sheep‐only grazing treatments. Year‐to‐year variation in the herbage mass and surface height of herbage in summer was greater than the effect of treatments. Despite changes in surface height, the structural diversity of the grasslands was not increased by the treatments. The annual production of vascular plant material ranged from 417 g DM m^?2 in 1994 to 628 g DM m^?2 in 1996.     

Effects of different levels of fertilizer application to veld on growth of steers and chemical composition of the herbage

The effects of different levels of N fertilization (no N, 40 kg N and 80 kg N ha^?1 year^?1), P fertilization (no P, 21 kg P ha^?1 year^?1 and 21 kg P plus 53 kg K ha^?1 year^?1) and stocking rates (0·52 large stock units (LSU) ha^?1, 0·78 LSU ha^?1 and 1·56 LSU ha^?1) on the chemical composition and in vitro dry matter digestibility of the herbage and the liveweight gains of steers were determined in the western variant of the Bankenveld in South Africa. The average daily liveweight gains (ADLGs) of the steers increased with increasing level of N fertilization. Fertilization with P had a positive effect on ADLG only when 53 kg of K was applied with 21 kg of P ha^?1. Higher stocking rates reduced ADLGs. The liveweight gains ha^?1 increased as the rates of N and P fertilization increased. The medium stocking rate (0·78 LSU ha^?1) gave a higher liveweight gain ha^?1 than the lowest stocking rate (0·52 LSU ha^?1), but the highest stocking rate (1·56 LSU ha^?1) reduced liveweight gain ha^?1. In general, in terms of chemical components, a higher nutritive value of the veld herbage resulted from N fertilization. The higher crude protein (CP) content of the herbage, resulting from higher stocking rates, should be seen against the background of lower liveweight gains ha^?1 at the highest stocking rate. On pasture with similar contents of CP and acid detergent fibre (ADF), higher ADLG of steers was found as a result of P and K fertilization, especially for herbage with a lower CP and a higher ADF content, implying better utilization of the nutrients in such herbage with P and K fertilization, although P was also supplemented through a lick.     

Performance and environmental effects of forage production on sandy soils. I. Impact of defoliation system and nitrogen input on performance and N balance of grassland

Grassland and its management is central to the productivity of and nitrogen (N) losses from dairy farms in north‐west Europe. Botanical composition, production and N surplus of grassland were assessed during five consecutive years. The experiment consisted of all combinations of five defoliation systems: cutting‐only (CO), rotational grazing (GO), grazing + one (MSI) or two silage cuts (MSII) and simulated grazing (SG). Four mineral N fertilization rates (0–300 kg N ha^?1 year^?1) and two slurry levels (0 and 20 m³ slurry ha^?1 year^?1) were applied. Fertilizer N was more efficient in producing net energy (NEL) in grazing‐dominated, low white clover systems (GO and MSI systems: 70 and 88 MJ NEL kg^?1 N) than in white clover‐rich systems (MSII, CO and SG systems: ≤60 MJ NEL kg^?1 N). While sward productivity in system MSI was similar to that in system GO, system MSII benefited from increased N₂ fixation at low N rates. There were small differences in NEL concentrations of the herbage between defoliation systems. Crude protein concentration of the herbage increased with increasing N supply from fertilizer, excreta and N₂ fixation. N surpluses (?63 to +369 kg N ha^?1 year^?1) increased with increasing grazing intensity and increasing N fertilization rate. The average response in N surplus applied was 0·81, 0·59, 0·40, 0·33 and 0·24 kg N ha^?1 in systems GO, MSI, MSII, CO and SG respectively.