Greater Stocking Rate Research Articles

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

AbstractNew 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.

Productivity Performance of Sheep in Silvopastoral Systems With Cashew Tree Compared to Grass Monoculture

The goal in this study was to evaluate the production of sheep and forage silvopastoral systems (SPSs) with cashew trees, compared to the production on grass monoculture. The treatments consisted of three grazing systems: one Massai grass monoculture (Panicum maximum cv Massai) (MONO), and two SPSs: intercrop of Massai grass + cashew tree (Anacardium occidentale) (SM) and intercrop of grass- Massai grass + Estilosantes Campo Grande (Stylosanthes capitata × S. macrocephala) + cashew tree (SME), in a completely randomized split plot design with four replications. The photosynthetically active radiation varied from 45 to 59% in SPSs, the presence of cashew trees created a microenvironment with lower temperatures and higher relative humidity throughout the day. Forage mass in the monoculture and in the SPSs was on average 2,116.65 kg dry matter (DM). ha-1; the participation of the legume in the forage mass was 44%. Greater stocking rate was found in the monoculture, however the gain per area was higher in the SME. In the SPSs, crude protein content of the grass increased by 46.2%, and there was a higher forage intake and weight gain of sheep, mainly in the system with legume. The silvopastoral system with cashew trees, Massai grass, estilosantes and sheep is feasible to optimize land use, with better gain per animal and area in relation to grass monoculture.

Low-Intensity, High-Frequency Grazing Strategy Increases Herbage Production and Beef Cattle Performance on Sorghum Pastures.

Simple SummaryFinding smart management targets to improve livestock production and make it sustainable are very important for livestock in the tropics. We assessed the effects of high-intensity and low-frequency (HILF) vs. low-intensity and high-frequency (LIHF) grazing on herbage production and performance of beef cattle grazing sorghum pastures. The LIHF resulted in shorter rest periods when compared with the HILF. The greater leaf lamina mass in LIHF allowed greater sward light interception at post-grazing, resulting in greater total herbage production than HILF. The average daily gain (ADG) was greater for the LIHF than for the HILF treatment; however, even with a greater stocking rate in the HILF, there was no difference for LW gain per ha. Our findings demonstrated that the LIHF strategy that is based on offering to the animals an optimal sward structure to favor the herbage intake rate fosters greater herbage production, harvesting efficiency, and ADG without compromising LW gain per area, despite the lower herbage harvested per stocking cycle. Therefore, we conclude that the classic trade-off between animal performance and forage production could be offset on tropical grasses grazed by beef cattle only by adjusting grazing management according to a LIHF grazing management strategy.We assessed the effects of high-intensity and low-frequency (HILF) vs. low-intensity and high-frequency (LIHF) grazing on herbage production and performance of beef cattle grazing sorghum pastures. The experimental design was a complete randomized block with two treatments and four replicates (paddocks), carried out in 2014/15. The management target of 50 and 30 cm for pre- and post-grazing, respectively, a LIHF grazing management strategy oriented to maximize beef cattle herbage intake per unit time, was compared with a HILF grazing management strategy of 80 and 20 cm for pre- and post-grazing, respectively, aiming to maximize herbage accumulation and harvest efficiency. Sixteen Brangus steers of 15-month-old and 265 ± 21 kg of live weight (LW) were randomly distributed to paddocks (experimental units). The LIHF resulted in shorter rest periods when compared with the HILF. The greater leaf lamina mass in LIHF allowed greater sward light interception at post-grazing, resulting in greater total herbage production than HILF (7581 and 4154 kg DM/ha, respectively). The average daily gain (ADG) of steers was greater for the LIHF than for the HILF treatment (0.950 and 0.702 kg/animal, respectively); however, even with a greater stocking rate in the HILF, there was no difference for LW gain per ha, with an average of 4 kg LW/ha/day. Our findings demonstrated that the LIHF strategy that is based on offering to the animals an optimal sward structure to favor the maximum herbage intake rate fosters greater herbage production, harvesting efficiency, and ADG without compromising LW gain per area of beef steers, despite the lower herbage harvested per stocking cycle.

Survey of cattle and pasture management practices on focal pastures in Alberta

A survey of Alberta beef producers was conducted at sites overlapping with a province-wide network of permanent biodiversity monitoring plots to characterize focal pastures and their management, including estimates of stocking rates. Overall, greater stocking rates were reported in the boreal compared with the parkland and grassland natural regions, coinciding with an increased reliance on tame forage on relatively small land areas of largely deeded land. Higher stocking rates were also associated with earlier starting dates of grazing in the season, higher mean annual precipitation, and lower mean annual temperature.

Profitable and resilient pasture-based dairy farm businesses in New Zealand

There have been several analyses of the economics of pastoral dairy farm systems in New Zealand using real farm data, as well as several relevant international studies. However, these analyses have often used a dataset with a limited number of years that do not reflect long-term exposure to volatility, or do not allow for regional differences, and often focus on imported feed without due attention to other important characteristics of profitable farms. Several prior analyses have failed to consider the importance of a business that is resilient to major risks. We re-examined the relevance of their conclusions for New Zealand dairy systems against 12 years of DairyBase data, focussing on two major regions, deriving key insights on relevant strategic choices for profitable and resilient businesses at a farm and, by extension, industry level. Within years and regions, the top quartile of observations was identified, on the basis of ranking by operating return on assets, as a proxy for farms achieving their potential, and compared with the remaining observations. Within geographical region, the greater profitability of the top quartile was associated with greater pasture and crop eaten, greater stocking rate and production per cow, and lesser operating expenses per hectare and per kilogram milksolids (MS), defined as fat plus protein. However, greater profitability was not associated with greater use of imported feed. Linear regression was used to determine that increases in total operating expenses were associated with increases in the costs of imported feed (including winter grazing and silage made on farm). On average, for every NZ$1 spent on imported feed, total costs increased by NZ$1.66 and NZ$1.53 for the Waikato and Canterbury–Marlborough regions, respectively. This is consistent with the international literature for temperate grazing systems and is likely the reason why profitability was not greater even if above-average responses to supplement were achieved on farm. Indeed, greater use of imported feed was positively associated with operating expenses per kilogram of MS, implying that the marginal cost of additional MS was greater than the cost of the base milk, and often higher than the value of the milk produced. If gross farm revenue per kilogram MS (which is largely made up of the milk price, with a lesser contribution from livestock sales) was greater than NZ$7.50 (which it was the case in only 3 of the past 12 years), farms could generate higher profit from more imported feed use; however, the reverse was true at lower milk prices. When milk prices are low, (i.e. gross farm revenue is less than NZ$6.50/kg MS, which occurred in half of the past 12 years), farmers are often under cashflow pressure. Therefore, farm systems that are less reliant on imported feed provide a better chance for farmers to meet financial commitments, although they fail to maximise profitability when the milk price is high (e.g. >NZ$7.50/kg MS). In conclusion, maximising pasture harvested, and minimising reliance on supplementary feed, and effective cost control (minimising expenditure) are the key factors that lead to profitable businesses that are also resilient to the low milk prices that occur in volatile markets.

Citrus pulp-based supplement reduces the detrimental effects of high grazing pressure on the performance of beef cattle under a rotational system of Urochloa brizantha

SUMMARY The objectives were to evaluate the performance of bull calves under two grazing strategies and the use of energy supplementation in a rotational system of marandu palisade grass (Urochloa brizantha) and to assess the morphological and chemical composition of the grass. Eighty eight-month-old bulls of 224 ± 2.4 kg body weight (BW) were used in a completely randomized block design in a 2×2 factorial arrangement of two post-grazing heights (i.e.10 cm or 15 cm) and of a citrus pulp-based supplement (i.e. 72% total digestible nutrients) fed daily at 0 or 6 g/kg BW. Initial grazing height was set at 25 cm with variable grazing intervals and stocking rate adjustments used to control the grazing heights. Statistical analyses were performed using the SAS Mixed procedure. Significance was set at 0.05. Forage data from 12 pre-determined paddocks showed no differences in forage mass (FM) and morphological composition at pre-grazing, but greater post-grazing FM and shorter grazing interval in pastures managed at 15 cm. Higher grazing pressure resulted in lowest BW gains for non-supplemented bulls in the 10 cm treatment. The use of an energy supplement and 15 cm postgrazing height resulted in the greatest BW gains; however, combination of10 cm post-grazing height and energy supplementation allowed greater stocking rates. Under high grazing pressure, supplementary feed overcame the normal limitations, and high gains were achieved.

Linking management practices with range health in northern temperate pastures

Little information exists on the management and range health (RH) of northern temperate pastures, where health is defined as the ability to sustain ecosystem function. We surveyed 102 pastures for RH and their associated managers during 2012–2013 across central Alberta, Canada. Pastures were generally diverse mixes of introduced grasses and contained few legumes, despite most (55%) being seeded to legumes. The majority of pastures were healthy (mean RH score = 78.8% ± 1.3%), with 2.9% having scores <50%. Criteria reducing scores were noxious weeds, bare soil, and evidence of erosion. Most pastures had a reported history of cultivation (75.5%), with those previously cultivated and seeded to introduced forage having greater stocking rates [6.18 ± 0.91 animal-unit-months (AUM) ha−1] compared with those lacking cultivation (2.14 ± 2.91 AUM ha−1). Farms with horses or mixed livestock tended to practice year-round continuous grazing and supplemental hay feeding. Stocking rates on continuous and rotationally grazed pastures were similar regardless of grazing season, with the highest stocking on pastures used year-round (19.54 ± 2.03 AUM ha−1) or throughout the dormant season (20.29 ± 3.10 AUM ha−1). Use of management inputs was variable, with manuring and harrowing common and fertilizing, over-seeding, and aerating infrequent. Herbicide use was reported on 15.7% of pastures, despite 83.3% containing noxious weeds. Use of prescribed fire was rare, although 36.3% of pastures had evidence of fire. Industrial disturbances were reported on 48.3% of pastures. Overall, these results indicate that these pastures experience complex management and the limited decline in RH is due to high stocking under year-long grazing.

Ungulates can control tree invasions: experimental evidence from nonnative conifers and sheep herbivory

Invasive conifer species are increasingly recognized as a serious problem in many parts of the world, where they are having large ecological and economic impacts. Understanding factors that trigger and can control invasion is key to management. Grazing and browsing by large herbivores have been suggested as a mechanism that may halt conifer invasions, although conflicting results have been reported (i.e. positive, negative or no effect of grazing on invasion). We believe that some of these opposing responses arise due to the absence of well-planned and replicated experiments, since current evidence is mostly observational, and for example, differences in animal densities can produce different results. Thus, in this study, we tested whether large herbivores can control invasion by nonnative conifers and whether the severity of the invasion process would be lessened by increased herbivory intensity. We evaluate experimentally herbivore damage on Pinus contorta, a highly invasive species in many countries of the Southern Hemisphere, under different sheep stocking rates in Patagonia, Argentina. We used four stocking rates, corresponding to 1, 2, 4 and 8 times the recommended sheep herbivory intensity for the study area. The response was not linear but rather presented a threshold. The greater stocking rate, the greater the browsing, higher reduction in seedling height, and decrease of survival of P. contorta. Also, the highest stocking rate damaged and killed 99% of them. This study provides evidence that large domestic herbivores can play a key role in the invasion process and, if managed properly, would provide a tool to help limit conifer invasion.

Predicting milk responses to cereal-based supplements in grazing dairy cows

The feeding of cereal-based supplements is common in the Australian dairy industry, as it allows cows to increase intakes of total dry matter (DM) and metabolisable energy (ME), while achieving greater stocking rates, greater pasture utilisation and greater milk production per hectare than occurs when cows are fed pasture-only diets. However, for this practice to be profitable, it is important to know how much extra milk, milk protein and milk fat are produced for each kilogram DM consumed. This is difficult to determine in such a complex biological system. We combined information from 24 concentrate-feeding experiments using meta-analysis techniques, so as to develop improved prediction models of the milk, milk protein and milk fat produced when cereal-based concentrates are fed to grazing, lactating dairy cows. Model terms, consistent with biological processes, linear, quadratic and factorial, were selected according to statistical significance. The models were then tested in two ways, namely, their goodness of fit to the data, and their ability to predict novel production data from a further six, unrelated, experiments. A sensitivity analysis was also undertaken to determine how sensitive these predictions are to changes in key inputs. The predictive model for milk yield was shown to very closely reflect milk yield (kg/cow.day) measured under the experimental conditions in unrelated experiments (r = 0.96), with very little bias (Lin’s bias correction factor = 0.98) and high concordance (Lin’s concordance coefficient = 0.95). Predictions generated by multiplying predicted milk protein concentration by predicted milk yield closely matched observed milk protein yield (kg/cow.day) (r = 0.96, Lin’s bias correction factor = 0.98, Lin’s concordance coefficient = 0.95), and predictions found by multiplying predicted milk fat concentration by predicted milk yield closely matched observed milk fat yield (kg/cow.day) (r = 0.94, Lin’s bias correction factor = 0.99, Lin’s concordance coefficient = 0.93). Factors included in the new models for milk, milk protein and milk fat yield reported here have been identified previously as elements that can influence milk production. The value to the dairy industry from being able to predict profitable amounts of concentrates to feed at various stages throughout lactation is considerable. For farmers and their advisers, being able to apply these models to estimate the immediate marginal milk protein and milk fat responses to supplementary feeds should lead to more robust, efficient and profitable milk production systems.

Management opportunities for boosting productivity of cool-temperate dairy farms under climate change

Improved knowledge of the effects of climate change on farming systems can help increase long-term production, economic performance, and mitigate risk. Here we assessed the effects of stocking rate and seasonal calving times on pasture and milk production under short and long term climate changes on dairy farms in Tasmania, Australia. Annual and monthly perennial ryegrass pasture production was simulated from 1971 to 2065 to examine trends in pasture productivity, forage requirements, and impacts on milk production in 2015 and 2050. The projected future climate for the study region indicates a mean warming of up to 1.4°C, with moderate declines in rainfall of up to 5%. Despite lower rainfall, climate change will likely have a positive impact on pasture yields, with annual production increasing by 13–16%, even though summer growth is reduced and inter-annual variability is increased. We found that greater pasture production is conducive to greater forage conservation, and together these factors allow intensification of stocking rates. These effects increase milk yields by 3–16% per annum and reduce reliance on purchased feeds, which together implies greater profitability of cool-temperate Australian dairy systems under future climates. We also found that total milk production in a spring calving system allows greater stocking rates and pasture utilisation compared with an autumn calving system, and whilst milk produced per animal declines under higher stocking rates, milk yield per hectare increases. Overall, our results suggest that global warming and climate change will positively affect pasture growth rates in Tasmania, and that greater production and conservation of home-grown feeds will be conducive to increased farm milk yields, provided that stocking rates are intensified sustainably.

Stocker Steer Performance on Tall Fescue or Meadow Fescue Alone or in Binary Mixture with White Clover

Little research has been conducted in the northern United States to evaluate meadow fescue [Schedonorus pratensis (Huds.) P. Beauv] or tall fescue [S. arundinaceus (Schreb.) Dumort] in pastures, and implications for animal performance. This research compared swards containing meadow fescue (MF) or tall fescue (TF) alone or co‐established with white clover (Trifolium repens L.). Pastures were rotationally grazed with crossbred beef steers (Bos taurus, initial weight 261 kg, n = 180) using a variable stocking rate to detect treatment differences. Sward white clover percentage decreased as the trial progressed (42, 25, and 12 for years 1, 2, and 3, respectively), coinciding with decreased steer performance. Swards containing TF had greater available forage (3200 vs. 2800 kg ha−1) and less in vitro true digestibility, neutral detergent fiber digestibility, and steer average daily gain (ADG) (0.84 vs. 0.98 kg d−1) (P < 0.05) than MF swards. Adding white clover to MF and TF swards improved forage quality, steer ADG (0.98 vs. 0.84 kg d−1), and animal gain per hectare (780 vs. 680 kg ha−1) (P < 0.05) vs. monoculture grass pastures. Steers on MF pastures had greater ADG than TF pastures, but because TF pastures had greater stocking rate, gain per hectare was not different for the two grasses (728 vs. 735 kg) (P > 0.05). These results demonstrate the superior forage quality and animal performance of MF pastures, the higher productivity of TF pastures, and the need for a productive, persistent legume in upper Midwest pastures.

Forage Characteristics of Bahiagrass Pastures Overseeded with ‘Ubon’ Stylosanthes

Overseeding warm-season legumes into warm-season perennial grass pastures is an option to improve forage quality and reduce the use of commercial N fertilizer. The objective of this study was to evaluate the effects of ‘Ubon’ stylo (Stylosanthes guianensis var. vulgaris × var. pauciflora) overseeded into bahiagrass (Paspalum notatum Flügge) pastures on forage production and nutritive value. Treatments were overseeding stylo into bahiagrass pastures, bahiagrass pastures fertilized with 60 kg N/ha/year, or control (bahiagrass pasture with no N fertilization or legume) arranged in a randomized incomplete block design with three replicates. All treatments were continuously stocked using a fixed stocking rate with two heifers (Bos spp.) per experimental unit. Forage evaluations were conducted every 28 days from July to October 2010 and 2011. Pastures fertilized with N had greater herbage mass (HM) and herbage allowance (HA) than overseeded or control treatments and there was no difference between overseeded and control treatments. Overseeded and N fertilized treatments had greater CP concentration than control. The proportion of Ubon stylo was constant in the overseeded pastures during the experiment (≈ 17%). The increased HM on N fertilized treatments may potentially allow greater stocking rates when compared to pastures overseeded with stylo.

Effects of establishment method and fall stocking rate of wheat pasture on forage mass, forage chemical composition, and performance of growing steers1

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

Estrutura do dossel, consumo e desempenho animal em pastos de capim-marandu sob lotação contínua

Avaliaram-se o valor nutritivo, a estrutura do dossel, a ingestão de forragem e a produção animal de novilhos em pastos de capim-marandu submetidos a três intensidades de pastejo. O delineamento experimental foi de blocos completos ao acaso, com duas repetições e três intensidades de pastejo, representadas pelas alturas do pasto de 15, 30 e 45cm. Mensalmente, os pastos foram amostrados para as estimativas das características estruturais do dossel e o valor nutritivo da forragem. A ingestão de matéria seca pelos animais foi estimada no verão e no outono de 2008. A oferta de forragem decresceu à medida que aumentou a intensidade de pastejo. Pastos manejados com 15cm de altura apresentaram maior valor nutritivo e estrutura do dossel mais favorável à apreensão de forragem pelos animais. A oferta limitou a ingestão de forragem no pasto com 15cm de altura, consequentemente se verificaram menor ganho de peso e maior taxa de lotação. Foram observados ganhos por área semelhantes nos pastos com 15 e 30cm, e ganhos mais elevados no pasto com 45cm. Durante o período das águas, o capim-marandu deve ser utilizado entre 15 e 30cm de altura sob lotação contínua.

Performance of stocker cattle grazing 2 sorghum-sudangrass hybrids under various stocking rates

<h2>ABSTRACT</h2> Summer annual forages are a practical roughage source for stocker cattle operations because of their high yield potential. A 2-yr study was conducted to compare the performance of steers grazing 2 different varieties of sorghum-sudangrass hybrids at different stocking rates. Brown midrib (BMR) and photoperiod-sensitive (PS) sorghum-sudangrass hybrids were selected based on differences in nutritional value and yield. Twelve experimental pastures (6 per variety) were established and grazed by steers (231 ± 4 kg) for 84 d each year at stocking rates ranging from 2.33 to 4.10 animal units per hectare per 84 d (3.6 to 6.4 steers/ha). Initial (0 d), intermediate (28 and 56 d), and final (84 d) cattle BW was used to calculate ADG and gain per hectare. Forage samples were also collected at 28-d intervals to assess quality and quantity of standing forage. Regression analysis was used to compare cattle production on BMR and PS forage varieties. A curvilinear model with stocking rate and forage variety best fit the data, accounting for 73 and 72% of the variation in ADG and gain per hectare, respectively. At light to moderate stocking rates, ADG and gain per hectare were greater for the BMR; whereas the PS maintained BW gain at greater stocking rates. Our results indicate that cattle grazing these sorghum-sudangrass forages were capable of gaining over 1 kg/steer per day and up to 437 kg/ha over an 84-d grazing season, but response was dependent on forage variety and stocking rate of experimental pastures.

Contribuição dos componentes e composição química de pastagens em sistemas forrageiros constituídos por diferentes leguminosas

Realizou-se o presente trabalho com o objetivo de avaliar a composição química de dois sistemas forrageiros, tendo como componentes comuns o capim-elefante, o azevém e as espécies de crescimento espontâneo, variando em um sistema o consórcio com o trevo branco, e, em outro, com o amendoim forrageiro. Para avaliação, foram usados quatro piquetes com 0,25ha cada um. Como animais experimentais, foram utilizadas vacas em lactação da raça Holandesa. O delineamento experimental utilizado foi o inteiramente casualizado, com dois tratamentos (sistemas forrageiros) e duas repetições (piquetes). Para análise de proteína bruta (PB), fibra em detergente neutro (FDN) e fibra em detergente ácido (FDA), foram retiradas amostras através de simulação de pastejo. A participação dos componentes dos sistemas forrageiros variou segundo as leguminosas componentes. O sistema composto por amendoim forrageiro permitiu suportar maior carga no período estival. Os valores médios (pré e pós-pastejo) para PB, FDN e FDA foram de 18,76; 71,46; 34,87% para o sistema forrageiro constituído com o trevo branco e de 19,31; 71,19 e 35,40%. Os resultados foram similares entre os sistemas forrageiros.

Gains and losses in C and N stocks of New Zealand pasture soils depend on land use

Previous re-sampling of 31 New Zealand pasture soil profiles to 1m depth found large and significant losses of C and N over 2–3 decades. These profiles were predominantly on intensively grazed flat land. We have extended re-sampling to 83 profiles, to investigate whether changes in soil C and N stocks were related to land use. Over an average of 27 years, soils (0–30cm) in flat dairy pastures lost 0.73±0.16MgCha−1y−1 and 57±16kgNha−1y−1 but we observed no significant change in soil C or N in flat pasture grazed by “dry stock” (e.g., sheep, beef), or in grazed tussock grasslands. Grazed hill country soils (0–30cm) gained 0.52±0.18MgCha−1y−1 and 66±18kgNha−1y−1. The losses of C and N were strongly correlated, and C:N declined significantly. Further, results reported to 60 and 90cm show that the pattern of losses and gains extend beyond the IPCC accounting depth of 30cm. Specific causes for the soil C and N changes are unknown, but appear to be related to land use. In general, the losses under dairying correspond to systems with greater stocking rates, fertiliser inputs and removal of C and N in exported products. Gains in hill country pastures may be due to long-term recovery from erosion and disturbance following land clearance. The unexpected and contrary changes of C and N in different pasture systems (initially thought to be at steady state) demonstrates the need for global and national-scale collection of robust data investigating soil biogeochemical changes, not only for grasslands but also for other land uses. Re-sampling of soils can constrain the directions and magnitude of soil C and N change associated with land use and management to underpin C and N inventories and correctly identify mitigation options.

Pasture - crop rotations for sustainable production in a wheat and sheep-based farming system on a Vertosol in south-west Queensland, Australia

Rainfed grain production, based on winter cereals, is marginal in south-west Queensland, Australia, because of low and variable rainfall and high evapotranspiration. Also, grain yield and grain quality have decreased as soil fertility, particularly soil nitrogen supply, has declined on older cropping lands. An option for improving soil N supply is to include legume-based pastures in rotation with winter cereals. The objective of this study was to determine the effects of short-term (18 months) legume pastures (annual medics and lucerne + annual medics), and longer term (3 years) mixed grass (Bambatsi panic) and legume (lucerne + annual medics) pasture phases on sheep production and on soil water and N supply and production of subsequent wheat crops on a grey Vertosol soil. Two separate phases of annual medics and lucerne + annual medics pastures produced mean total aboveground dry matter yield of 7.10 t/ha of annual medics and 5.80 t/ha of lucerne + annual medics over the 18-month periods. For two phases of the grass + legume pastures, mean total aboveground dry matter yield was 3.95 t/ha for grass and 8.19 t/ha for legume over 3 years. Over an 18-month period, sheep bodyweight gains and fleece weights were similar for the annual medics, lucerne + annual medics and grass + legume pastures and were approximately five times greater than those from native pasture as a result of the greater stocking rate possible on the sown pastures. Greater drying of the soil profile occurred following lucerne + annual medics and grass + legume pasture phases than continuous wheat, resulting in lower soil water content at sowing of wheat crops following these pasture phases on several occasions. Mean soil nitrate-N benefits before wheat sowing in the first year following termination of the 18-month annual medics, lucerne + annual medics, and the 3-year grass + legume pasture phases were 45, 44 and 42 kg N/ha, respectively. Grain N yields and gross margins of the first wheat crops following the 18-month annual medics, lucerne + annual medics, and the 3-year grass + legume pasture phases were similar in value to continuous wheat with ~60, 80, and 40–60 kg N/ha fertiliser applied at sowing, respectively. Improvements in grain N yield and gross margin were still evident in the fifth wheat crop following annual medics and lucerne + annual medics pastures and in the third wheat crop following grass + legume pasture, compared with continuous wheat without N fertiliser addition. Total gross margins from 1996 to 2005 were 1.6–2.5 times greater for the pasture–crop rotations than continuous wheat where no N fertiliser was applied to wheat. However, gross margins were greater in continuous wheat than in pasture–crop rotations where N fertiliser was applied to target prime hard grade grain protein in wheat. The 3-year grass + legume pasture phase showed potential to improve surface soil structure and water infiltration and to reduce decline in soil organic carbon concentration at 0–0.1 m depth, compared with continuous wheat cropping and shorter-term legume pasture phases.

Grass Yield and Quality Affect Potential Stocking Rate and Milk Production

Emphasis placed on pasture yield may lead producers to disregard the potential influence of forage quality on animal performance. Our objective was to compare yield and quality, and potential stocking rate and milk production of four temperate grasses. Meadow fescue, orchardgrass, quackgrass, and reed canarygrass were each harvested at 10-inch height in the spring, summer, and fall and yield, cell wall concentration, and cell wall digestibility were used to calculate potential stocking rate and daily milk production. Quackgrass and reed canarygrass would support a 40 to 90% greater stocking rate during the spring and summer than meadow fescue or orchardgrass, while cows grazing meadow fescue would produce 5 to 12 lb more milk per day than those grazing the other grasses. Translating forage quality into potential milk production allows producers to assess the potential trade-offs between animal and forage productivity when considering the value of a pasture grass.

Produção de novilhos superprecoces em pastagem de aveia e azevém submetida a diferentes alturas de manejo

Foram avaliadas a produção e as características de carcaças de novilhos jovens mantidos em pastagem cultivada de aveia preta (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam) manejada em diferentes alturas. Os tratamentos impostos foram quatro diferentes alturas de manejo da pastagem (10, 20, 30 e 40 cm), obtidas por meio da aplicação de diferentes cargas animais. O delineamento foi o de blocos casualizados, com três repetições. Utilizaram-se animais jovens de aproximadamente dez meses de idade, machos castrados sem padrão racial definido, com peso médio inicial de 210 kg. O aumento no ganho médio diário (GMD) foi condicionado pelo incremento na qualidade e/ou na quantidade de forragem disponível, visto que as ofertas de forragem para os tratamentos de 10, 20, 30 e 40 cm de altura foram de 6, 10, 23 e 51 kg de MS/100 kg de PV/dia, respectivamente. Portanto, o modelo de resposta do GMD em relação às alturas de pastejo resultou em valores de 0,73 e 1,14 kg/animal/dia nos tratamentos de menor e maior GMD, respectivamente, que foram de 10 e 30 cm de altura. Como a variação no GMD foi baixa, o maior ganho por área observado no tratamento 10 cm pode ser atribuído à maior carga animal, ambas com respostas lineares decrescendo com o aumento da altura de pastejo. O peso vivo dos animais antes do abate e o peso de carcaça quente elevaram com o aumento da altura da pastagem, reduzindo apenas no tratamento 40 cm com a redução da qualidade da pastagem. Não houve diferença entre os tratamentos para o rendimento de carcaça, pois todos os valores mantiveram-se em torno de 51%. O escore de condição corporal e o grau de acabamento apresentaram tendência muito similar à evolução do ganho médio diário dos animais.