Canopy height and N affect herbage accumulation and the relative contribution of leaf categories to photosynthesis of grazed brachiariagrass pastures

The effects of three canopy heights (10, 25 and 40 cm) and two N rates (50 and 250 kg ha^?1 year^?1) on herbage accumulation (HA), participation of leaf categories in the leaf area index (LAI) and photosynthesis of grazed “Mulato II” brachiariagrass (Brachiaria brizantha × B. decumbens × B. ruziziensis) were investigated during two summer growing seasons in Piracicaba, São Paulo, Brazil. The HA and LAI increased linearly from 8560 to 13600 kg DM ha^?1 year^?1 and 2.3 to 5.5 m² m^?2, respectively, as canopy height increased. Mulato II brachiariagrass maintained at 10 cm canopy height showed greater proportion of young leaves, but was less productive than taller canopies. Taller canopies had greater proportion of mature leaves in the LAI as well as greater photosynthesis. The greater N rate contributed to increased LAI, leaf and canopy photosynthesis rates and HA but did not affect the LAI composition. The total leaf area is more important to HA than the proportion of young leaves in the LAI, as taller canopies were more productive, suggesting that maintaining Mulato II brachiariagrass at 25 or 40 cm is advantageous for this grass.     

Herbage and animal responses on continuously stocked ‘Ipyporã’ and ‘Mulato II’ brachiariagrasses

New hybrid grass cultivars may enhance animal performance in forage-livestock systems if they possess traits that address edaphoclimatic challenges and pest susceptibility. The objective was to assess herbage accumulation, plant-part composition, nutritive value, and animal performance of ‘Ipyporã’ [Brachiaria ruziziensis Germ. & Evrard × B. brizantha (Hochst. ex A. Rich.) Stapf] and ‘Mulato II’ (B. ruziziensis × B. brizantha × B. decumbens Stapf) hybrids in the Brazilian Amazon biome. From May 2016 to May 2018, pastures were maintained under continuous stocking with variable stocking rates to maintain canopy height at 30-cm. Herbage accumulation (HA) was greater in Mulato II (17,370 kg dry matter [DM] ha⁻¹ year⁻¹) than Ipyporã pastures (14,930 kg DM ha⁻¹ year⁻¹) across the years. In Year 1, Mulato II had greater stocking rate (1685 vs. 1215 kg body weight [BW] ha⁻¹) and greater gain ha⁻¹ (1130 vs. 850 kg) than Ipyporã. However, in Year 2, both cultivars had similar plant and animal responses. The Year 1 ADG was similar among cultivars or seasons but in Year 2, rainy seasons had 21 and 77% greater ADG than dry seasons for Mulato II and Ipyporã, respectively. Both cultivars can contribute to the diversification of pasture-based livestock systems in humid tropical regions. Mulato II presented superior performance when soil moisture and fertility were not limiting (i.e., Year 1). However, both cultivars provide similar plant and animal responses in Year 2, offering viable alternatives for the diversification of pasture-based livestock systems in the Amazon Biome.     

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.     

Productivity and canopy modification of Medicago arborea as affected by defoliation management and genotype in a Mediterranean environment

Medicago arborea is one of the most potentially valuable fodder shrubs in a Mediterranean environment because of its high preference by small ruminants and its nutritive value. Edible biomass production is affected by agronomic and environmental factors. A study, carried out in an inland area of Sicily in the growing seasons of 1994/95, 1995/96 and 1996/97, evaluated the forage production and canopy modification in a M. arborea plantation after (i) commencing defoliation 1 or 2 years after transplanting and (ii) defoliating only in autumn (A), only in early summer (S) or in both seasons (A and S). Six clones derived from five different Mediterranean populations were used. Plant age at the first defoliation did not significantly influence forage production. The genotypes differed in growth rate and forage production. The season and frequency of defoliation markedly influenced forage production and canopy size. The highest annual production was obtained by defoliating once a year in early summer (on average, 1·65, 2·85 and 4·50 tonnes ha^?1 respectively in the three growing seasons). With the A and S, and A defoliation treatments, production decreased over 3 years by, on average, 0·19 and 0·57 respectively, but the differences became more marked over a 3‐year period. Defoliating only in early summer, however, resulted in an excessive shrub height (>120 cm, 3 years after transplanting), thereby increasing problems of accessibility to small grazing ruminants, and possibly necessitating cutting. On the contrary, the A and S defoliation made it possible to limit the height to <90 cm.     

Management strategies for forage rape (Brassica napus L. cv Goliath): Impact on dry-matter yield,plant reserves,morphology and nutritive value

Limited information is available on the grazing management principles of forage rape (Brassica napus L.), particularly in relation to grazing height and intensity and the impact of these on dry-matter (DM) yield and nutritive value. A glasshouse study was undertaken to investigate the effect of three defoliation heights (plant height at harvest; DH: 40, 70 and 90 cm; L, M and H DH respectively) and three defoliation intensities (height at which plants were cut; DI: 5, 20 and 35 cm of residual height; H, M and L DI respectively) on forage rape (cv Goliath) yield and nutritive value at two harvests (harvest 1, H1 and harvest 2, H2), and the impact of nitrogen (N) and water soluble carbohydrate (WSC) reserves on regrowth. Increasing DH from L to H increased estimated total DM yield (H1 plus H2) from 0.5 to 4.6 t DM/ha but DI did not affect yield. Dry-matter yield was optimized at 90 cm DH, but greater nutritive value was achieved by harvesting at lower levels of DH. Despite high in vitro DM digestibility (IVDMD; 852–889 g/kg), harvesting at 90 cm DH could not meet the protein requirement of lactating dairy cows and harvesting at lower levels risks nitrate poisoning. Our results indicate the optimum DH may be between 70 and 90 cm DH, and 20 and 35 cm DI, which requires further studies.     

Optimal defoliation management of brachiaria grass–forage peanut for balanced pasture establishment

A well‐established canopy is crucial for a stable mixed grass–legume forage pasture. The aim of this study was to assess a defoliation intensity that can ensure the establishment of mixed pasture of brachiaria grass (Brachiaria brizantha) intercropped with forage peanut (Arachis pintoi). The treatments comprised four canopy heights: 10, 20, 30 and 40 cm, maintained throughout the first 3 years of pasture establishment. Canopy structure, morphogenetic and structural characteristics were measured. A block design was used with four replicates, and seasons of the year were considered using repeated measurements over time. Light interception during the experimental period was 86.3%, 95.9%, 97.6%, and 99.1% for 10, 20, 30 and 40 cm of defoliation respectively (p < .001). Competition for light in taller canopies (at 30 and 40 cm) caused etiolation of forage peanut (greater internode, petiolate and stolon lengths). This response promoted its upward growth, leading to a lower stolon density compared with 10 and 20 cm. The treatment at 10 cm displayed a predominance of forage peanut (up to 0.614), potentially compromising community stability. Overall, the 20 cm canopy height showed a desired botanical composition (from 0.20 to 0.45 of legume in forage mass) and thus was considered an ideal defoliation intensity for establishment of mixed canopies of brachiaria grass and forage peanut.     

Field indicators of leaf nutritive value for perennial ryegrass and tall fescue pastures under different growing and management conditions

Field indicators of forage nutritive value could help farmers with rapid management decisions to optimize timing and intensity of grazing and meet objectives regarding animal nutrition. The objective of this research was to evaluate the likely relationships among leaf blade nutritive value, herbage mass and leaf stage of pasture regrowth under different growing seasons and residual sward heights. Experiments were performed on perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) pastures during spring and summer of 2016. In both pastures, three residual sward height treatments (3, 6 and 12 cm) were imposed on plots arranged in a split plot design, replicated in three blocks. Sward plots were harvested 5–6 times at intervals spaced 7–10 days apart to measure herbage mass, plant morphology, neutral detergent fibre (NDF), and the 24-hr in vitro digestibility of NDF (NDFD) and dry matter (DMD) of leaf blades. Pastures showed strong (R²: .62 to .70), but variable, negative relationships between NDFD and herbage mass that varied with the rate at which pasture grew in each season of experimentation. Although there was a consistent NDFD decline as leaf stage of regrowth progressed (R²: .75 to .97), the NDFD also decreased as residual sward height increased, most notably in tall fescue. Additionally, findings indicate that the greater leaf length plasticity of tall fescue compared to residual sward heights may offer opportunities to manage both post- and pre-grazing targets to achieve tall fescue forages with a similar high nutritive value as perennial ryegrass. However, the evaluation of this hypothesis at the farm level and its impacts on animal intake and performance warrants further careful investigations.     

Effects of sheep stocking on the plant community and agricultural characteristics of upland Anthoxanthum odoratum–Geranium sylvaticum meadow in northern England

In the UK, upland hay meadows (Anthoxanthum odoratum–Geranium sylvaticum grassland) with high plant biodiversity are rare and confined to submontane areas of northern England. We report results from a 5‐year experiment to test suggestions that recent biodiversity declines were attributable to increased sheep‐stocking density and a longer spring stocking period, thus delaying the shut up date for the growth of the hay crop. Longer stocking periods and higher stocking densities decreased the forage mass at 8 July, but they increased herbage N content and digestibility, reduced plant species diversity and reduced populations and seed production of Rhinanthus minor. Compared with unstocked swards, the similarity of the vegetation to Anthoxanthum odoratum–Geranium sylvaticum grassland was reduced by 16·9% when stocking with sheep continued until 27 May each year, and by 8·3% when sward heights were maintained at 3 cm compared with 5 cm. Increased mean sward height and height of R. minor were positively correlated with accumulated temperatures. Results support suggestions that recent reductions in the nature value of these grasslands might be a consequence of high stocking densities persisting until later in the spring, carried out during a 1‐year period with warmer temperatures.     

Tiller size/density compensation in perennial ryegrass miniature swards subject to differing defoliation heights and a proposed productivity index

The objective of this study was to investigate the effects of cutting height on tiller population density, tiller weight and herbage harvested in perennial ryegrass swards. One hundred mini-swards of Lolium perenne were established from seed on 5 May 1993 in 150 mm × 150 mm plastic pots in a greenhouse. The experimental period lasted 6 months (May to November). On 4 June all pots were cut to 50 mm and randomly allocated to five treatments (20, 40, 80, 120 and 160 mm sward surface height) with twenty replicates (four per tray). All pots were cut twice weekly to the specified surface height from 11 June, and recording began on 14 June. Every 4 weeks from 9 July to 5 November the twenty pots contained in one tray were withdrawn for destructive measurements of tiller population density and the weights of tiller components. Tiller population density increased with reduction in defoliation height, except for the 20-mm treatment where tiller density was initially restricted. The slope of the size/density compensation (SDC) line was close to ?5/2 over the range of defoliation heights 40–120 mm, but was less than ?1·0 between 120 and 160 mm. These slopes are consistent with a recent theory, which proposes that variations from a slope of ?3/2 will be linked to defoliation-induced changes in canopy leaf area and to change in tiller leaf area:volume ratio, R. At defoliation heights below 120 mm, SDC slope was increased by reduction in canopy leaf area. Above 120 mm, increase in R forced a relatively rapid tiller population decline, resulting in a reduced SDC slope and decrease in canopy leaf area. Whereas traditional measures of leafiness such as leaf:stem ratio or leaf:non-leaf ratio decreased with increasing height of defoliation, the leaf area:volume ratio, R, increased with defoliation height. Distance from an arbitrarily positioned ?3/2 SDC line was correlated with sward productivity.     

Interactions between leaf lifespan and defoliation frequency in temperate and tropical pastures: a review

In continuously stocked swards or pastures the frequency at which individual tillers and individual leaves are defoliated by ruminant livestock, relative to leaf lifespan of the grass species within the sward, determines the proportion of each leaf defoliated before senescence, and hence the efficiency of harvesting of herbage. In this paper, sets of data obtained in a range of climatic conditions and with a range of grass species are used in order to document this relationship. It is shown that the frequency of defoliation of individual tillers or individual leaves is closely linked to the average stocking density used within a period of time for maintaining a steady state sward or pasture height, herbage mass or leaf area index. Consequently, any decrease in herbage growth rate should lead to a decrease in the efficiency of harvesting of herbage and then to a more than proportional decrease in total herbage consumption by ruminant livestock. These effects will be more important for grass species having short leaf lifespan than for species with long lifespan. In rotational stocking, the link between herbage growth rate and frequency of defoliation of leaves can be broken by controlling the grazing interval, so any decrease in herbage growth would not be systematically associated with a decrease in efficiency of harvesting of herbage. Rotational stocking should be more efficient than continuous stocking in low herbage production conditions, while in high herbage production systems rotational and continuous stocking would have similar efficiency. The implications of these conclusions for the management of swards and pastures to meet different objectives are discussed briefly.     

The effect of frequency and height of defoliation on the production and persistence of 'Grasslands Matua' prairie grass

The performance of prairie grass ( Bromus willdenowii Kunth) cv. Grasslands Matua was examined under mowing at five defoliation intervals (10, 20, 30, 40 and 50 d) and two defoliation heights (3 cm and 8 cm). Annual and seasonal production of both the total herbage and of Matua, and the proportion of Matua in the sward, increased with less frequent defoliation. To a lesser extent, increasing the height of defoliation increased dry matter yield. Matua tiller numbers were increased by less frequent defoliation and were greater under the 8 cm than the 3 cm defoliation height. To increase prairie grass production and persistence, rest intervals between grazings of 40 to 50 d are recommended, or alternatively, a management involving silage or hay cutting offers scope.     

Effect of defoliation frequency and cutting height on growth,dry‐matter yield and nutritive value of Napier grass (Pennisetum purpureum (L.) Schumach)

Growth characteristics, dry‐matter (DM) yield, chemical components and in vitro dry‐matter digestibility (IVDMD) of Napier grass were studied in a randomized complete block design with three replications at Haramaya University, Ethiopia. The treatments were three defoliation frequencies (60, 90 and 120 d after Napier grass establishment) and five cutting heights (5, 10, 15, 20 and 25 cm above ground level). Except for leaf‐to‐stem ratio, all growth characteristics increased with decreasing frequency of defoliation. Similarly, DM yield of Napier grass increased as the frequency of defoliation decreased. Total ash, crude protein (CP), hemicellulose and IVDMD contents of Napier grass increased with increasing frequency of defoliation, whereas DM, acid detergent fibre, acid detergent lignin and cellulose contents increased with a decrease in defoliation frequency. In contrast, cutting heights had no significant effect on most chemical components and IVDMD contents, although total ash and CP decreased as the height of cutting increased. The CP yield per cut and per day was highest at an intermediate defoliation frequency. The results of this study indicated that Napier grass could be categorized under medium‐ to high‐quality herbage if defoliated at 90 d after establishment in the mid and highlands of Ethiopia.     

The effect of sward height and its direction of change on the herbage intake, diet selection and performance of weaned lambs grazing ryegrass swards

Abstract Four sward height treatments were imposed by continuous variable stocking using at least ten Suffolk × Greyface lambs per plot from late July to late August: constant 3·5 cm. constant 6·0 cm. 3·5cm increasing to 6·0 cm and 6·0 cm decreasing to 3·5 cm. The treatments were established on two swards given fertilizer N applications over the season of 97 and 160 kg N ha^?1 respectively. Animal density was greater on the high fertilizer treatment, at the lower sward height and especially on the decreasing height treatments. Liveweight change of lambs was higher (P <0·001) on the 6-cm than on the 3·5-cm treatments (+159 vs-13g d^?1 and was also higher (P <0·001) on the increasing than on the decreasing sward height treatments (+92 vs-26 g d^?1). Herbage organic matter intake (OMI), measured on two occasions in the experiment, was greater (P <0·001) on the 6·0 cm than on the 3·5-cm sward heights whereas values for the increasing sward height treatments were much greater than those for the decreasing sward height treatments. There was little difference in the organic matter digestibility of the diet between treatments. Diets were composed largely of lamina, although there was more pseudostem and dead herbage in the diets of Iambs grazing the decreasing than the increasing sward height treatments at the end of the experiment. Bite mass was closely related to OMI but the treatment and period differences were relatively greater than for OMI. Bite mass was more closely related to the depth of the lamina layer (sward height-pseudostem height) than it was to sward height. There was evidence that pseudostem acted as a barrier to defoliation on these short swards and also that the proportion of youngest leaf in the diet was positively related to sward height and to increases in sward height. Sward height and especially the direction of change in sward height, together with associated stock density, were potent influences on lamb growth rate. This was a consequence of differences in herbage intake, which was strongly influenced by bite mass.     

The effects of defoliating grass in winter or spring on herbage yields and ensilage characteristics

Under Irish conditions, the digestibility in May of grass managed for silage production is sometimes lower than expected. In each of two successive years, replicate field plots were established to examine the effects of three defoliation heights (uncut or cut to a stubble height of 10 or 5 cm) applied in winter and/or spring on herbage yields harvested in May and again in July, and on chemical composition and conservation characteristics associated with first‐cut silage. Swards that were not defoliated in December or March had a dry‐matter (DM) yield and in vitro DM digestibility (DMD) in mid‐May of 6597 kg ha^?1 and 736 g kg^?1, respectively, in Year 1, and corresponding values of 7338 kg ha^?1 and 771 g kg^?1 in Year 2. Defoliating swards to 5 cm in December reduced (P < 0·001) May DM yields compared to swards that were not defoliated in both December and March, while herbage DMD in May increased (P < 0·001) when defoliated in December or March. There were no clear effects of defoliation height or its timing on herbage ensilability or resultant conservation efficiency characteristics. The effects of defoliation on July yield were the reverse of those observed for May, while the total yield of the December and March defoliations plus the two silage harvests increased as defoliation height was lowered in Year 2 only. It is concluded that defoliation in winter and/or spring can increase herbage digestibility but will likely reduce DM yields in May.     

A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights. 2. Animal production

Performance of continuously stocked Mule ewes nursing Suffolk-cross twin lambs over three grazing seasons, between April and August, was compared on swards of N-fertilized diploid perennial ryegrass (D), tetraploid perennial ryegrass (T) and tetraploid perennial ryegrass with white clover (TC), the latter receiving no fertilizer N. Sward height was maintained by variable stocking rate close to a target of 4–6 cm (constant treatment) from turnout and compared in July and August with a rising sward height treatment (target 6–8 cm). Lambs on TC swards had significantly higher (P <0·001) liveweight gains compared with lambs on T swards by 41 gd^-1 in April–June and by 68gd^-1 in July-August. Live weight and body condition score of ewes in August were significantly higher (P<0·001) on TC compared with T swards, by 11·3 kg and 0·75 respectively. Rising sward heights in July–August increased live-weight gain of lambs compared with constant sward heights by 102, 39 and 54gd^-1 in consecutive years, associated with sward height increases of 0·9, 0·5 and 0·6cm respectively. Rising sward height increased ewe live weight and body condition score by 5·1 kg and 0·3 respectively, compared with results from constant sward heights. Effects of sward height and sward type were additive. T swards had a significantly (P<0·01) 16% greater overall lamb output than the D swards due mainly to a 10% higher achieved stocking rate. Stocking rates of ewes on TC vs T swards were 40, 13 and 12% lower in April-August in successive years. The higher liveweight gain of lambs on the TC swards resulted in lamb outputs of 76, 105 and 101% of the T swards in successive years, showing that grass/clover swards containing over 20% clover could produce similar lamb output ha^-1 to grass swards given 150–180 kg N ha^-1.     

Consequences for biodiversity of reducing inputs to upland temperate pastures: effects on beetles (Coleoptera) of cessation of nitrogen fertilizer application and reductions in stocking rates of sheep

Current policies for upland pasture management in the UK encourage the integration of environmental objectives with livestock production through extensification of grazing systems. This study tested the hypothesis that a greater sward height in the summer would increase the diversity and abundance of grassland beetles (Coleoptera) as has been demonstrated for insects of indigenous grasslands. The hypothesis was tested with an experiment on an upland sheep pasture in mid‐Wales. Experimental treatments received different nitrogen fertilizer inputs (0 or 50 kg ha^?1), sheep stocking densities (12 or 9 ewes ha^?1) and average sward heights in summer were constrained to 3·5 or 5·5 cm by conserving surplus grass for silage in subplots. Five treatments, replicated in three randomized blocks, combined the two stocking densities and two sward heights without nitrogen fertilizer inputs, with the fifth combining the higher stocking density, shortest sward height and the nitrogen fertilizer input. Beetles were sampled with twelve pitfall traps in each of the fifteen plots from June to September in 1993 and 1995. In years 1 (1993) and 3 (1995) of the experiment, more Coleoptera species occurred in the tall sward (an average of nine species in addition to the forty‐one species present in the sward with the conventional sward height). Continuously grazed as opposed to ensiled subplots supported more beetle species but fewer individuals. Species composition of ground (Carabidae) and rove (Staphylinidae) beetles varied between treatments more than the arithmetic differences in species number. The experimental results supported the hypothesis but the benefits of taller swards to species diversity were small in the sown pastures of the study compared with indigenous upland grasslands (c. 33% fewer species). Inheritance effects of drainage, fertilizer and lime inputs, and the different species and management of cultivated pastures, may constrain the conservation benefits of altered pasture management compared with indigenous grasslands.     

Harvest management based on leaf stage of a tetraploid vs. a diploid cultivar of annual ryegrass

Leaf stage‐dependent defoliation is linked to the plant's physiological status and may be a more suitable criterion than time‐based intervals for harvesting forage grasses, but no reports of research with annual ryegrass (Lolium multiflorum Lam. var. westerwoldicum) were found. To address this, a 2‐year field study was carried out at Raymond, MS, on a Loring silt loam soil (fine‐silty, mixed, thermic Typic Fragiudalfs). Forage production, morphological characteristics and nutritive value responses to defoliation based on leaf stage (2, 3 and 4 leaves per tiller) and two residual stubble heights (RSH; 5 and 10 cm) of a tetraploid (“Maximus”) vs. a diploid (“Marshall”) cultivar of annual ryegrass were quantified. Forage harvested, in 2011, increased linearly as leaf stage increased from 7.3 to 8.8 Mg/ha, but during 2012 was least (7.0 Mg/ha) at 3‐leaf stage and similar at the other two leaf stages (7.6 Mg/ha). Tiller density was less for Maximus (1,191 tillers/m²) than for Marshall (1,383 tillers/m²). Leaf blade proportion decreased with increasing leaf stage and was greater by 9% for Maximus than for Marshall. Generally, forage nutritive value became less desirable with increasing leaf stage. There was a dichotomy in forage harvested and nutritive value responses, but maximum forage productivity was achieved when annual ryegrass was defoliated at the 4‐leaf stage interval.     

The effect of grazed sward height and stocking rate on animal performance and output from beef cow systems

During three consecutive summers, forty spring-calving beef cows and their calves grazed perennial ryegrass-dominant swards receiving 250 kg N ha^?1 at one of two annual stocking rates [2.0 (SR 2.0) or 2.5 (SR 2.5) cows ha^?1] and one of two sward heights [4–5 (LS) or 7–8 (HS) cm] in a 2 × 2-factorial experiment, replicated twice. Sward heights were maintained from turn-out in spring by weekly adjustment of the area grazed and herbage was cut for silage in June and again in August from the areas not grazed. After the second cut of silage there was no control of sward height. Calves were weaned in early October and cows removed from pasture and housed when sward heights fell to 4 cm in autumn. Cows were fed in groups a variable but measured quantity of silage during winter to achieve a body condition score of 2.0–2.25 at turn-out the following spring. During the period of sward height control the cows on the HS treatment gained more live weight than those on the LS treatment (0.841 vs. 0.496 kg day^?1; P<0.01) as did the calves (1.167 vs. 1.105; P<0.05). but the stocking rate treatment had no effect. From the time of second-cut silage to the time of weaning and housing respectively, calves and cows gained more live weight on the SR 2.0 treatment because sward heights were higher. Reproductive performance of cows was not affected by treatment. The quantity of silage produced and consumed per cow was not affected by sward height treatment, but the SR 2.0 treatment produced significantly (P<0.001) more silage (1559 kg dry matter per cow) than the SR 2.5 treatment (833 kg dry matter per cow) and had higher winter silage requirements (1249 vs. 1153 kg dry matter per cow: P<0.05). The overall mean stocking rate at which winter fodder production and requirements would be in balance was calculated as 2.25 cows ha^?1 but values were 1.86, 2.60 and 2.28 in each of the three years of the experiment. The results showed that it was possible to control sward height in temperate beef cow systems by adjusting the area available for grazing. Body condition score can be used as a means of determining the feeding levels required to manipulate body condition of cows over winter to achieve prescribed levels of body condition. The experimental approach allows the identification of the stocking rate at which self-sufficiency in winter fodder can be achieved and the year-to-year variation associated with that stocking rate. This approach could be generalized if information on herbage growth rate were available, either from direct measurement or from predictive models.     

Increasing the population of forage peanut in a mixed pasture by controlling the canopy height

The aim of this study was to determine a temporary strategy for increasing the legume population in an established pasture of brachiaria grass (Brachiaria brizantha) and forage peanut (Arachis pintoi). The treatments comprised four previous long‐term canopy heights (10, 20, 30 and 40 cm) from the establishment (the first 32 months after treatment initiation). From September 2014, all of the experimental units were kept at 10 cm height. The pastures were evaluated for their forage harvest, forage mass, botanical composition and stolon and tiller density. The tiller density and brachiaria grass mass were maintained in all pastures since the first season of evaluation (p > 0.10). The stolon density and legume mass were initially lesser at 30 and 40 cm than those at 10 and 20 cm, early in the experiment, but progressively increased over time. After 1 year under 10 cm height, the population and mass of legume were similar in all treatments. Therefore, reducing the canopy height to 10 cm at the beginning of the rainy season is an efficient method to increase the botanical composition of forage peanut in mixed pastures with brachiaria grass.     

The effect of grazing intensity on the performance of high‐yielding dairy cows

The study evaluated the impact of High, Moderate and Low grazing intensities throughout the grazing season, within a rotational stocking system, on the performance of high‐yielding dairy cows receiving a high level of concentrates. Sixty‐three Holstein‐Friesian dairy cows, 21 at each grazing intensity, were rotationally grazed. Average paddock size, post‐grazing sward heights and seasonal grazing stocking rates within the High, Moderate and Low grazing intensities were 0.143, 0.167 and 0.200 hectares, 5.2, 6.1 and 6.8 cm and 7.8, 6.7 and 5.6 cows ha^?1 respectively. Grazing intensity had no effect on milk fat and protein content, end‐of‐study body condition score or end‐of‐study live weight although the latter tended towards significance (p = .057). Average daily milk yield per cow was higher within the Low grazing intensity (33.2 kg day^?1) than High grazing intensity (30.5 kg day^?1), and average daily fat‐plus‐protein yield was higher for Low and Moderate than High. Milk output per hectare was higher for the High grazing intensity than Low grazing intensity (33,544 and 26,215 kg ha^?1 respectively). Grazing intensity had no effect on grazing bite number, blood metabolites or concentrations of milk fatty acids or on sward morphological components, although dead matter increased with time across all grazing intensities. Herbage utilization efficiency (above 1,600 kg DM ha^?1) was 52%, 74% and 87% for Low, Moderate and High respectively. It is concluded that high‐producing dairy cows can graze at high levels of utilization when they are receiving high rates of concentrates. Although cow performance will be reduced, milk yield per ha will increase.