Intensive Rotational Grazing Systems Research Articles

Growth performance, carcass characteristics, and meat quality in meat and dairy goat kids fed a concentrate-based diet or allotted to an intensive rotational grazing system

Forty meat or dairy kids were blocked within breed according to body weight. Kids within each block were then randomly allotted to a concentrate-based diet or an intensive rotational grazing system. Kids fed the concentrate-based diet were offered hay ad libitum and fixed amounts of whole corn and soybean meal to meet the requirements for maintenance and daily gain. Grazing kids from each breed were stocked in groups and offered a new paddock every day. Dry matter intake was not different between breeds. Meat kids had a greater average daily gain than dairy kids but feeding treatments did not affect the growth rate. Dairy kids had greater anterior cuts (neck, shoulder), whereas meat kids tended to have greater posterior cuts (loin, leg). Meat kids accumulated more fat when they were fed concentrate in comparison with pasture, whereas this variable tended to be less influenced by dietary treatments in dairy kids. Meat of pasture-fed kids had greater Warner-Bratzler shear force and glycolytic potential, and lower ultimate pH than meat of concentrate-fed kids. The n-6/n-3 fatty acid ratio of intramuscular fat was almost 4-fold greater in concentrate- then pasture-fed kids; this ratio was 1.4-fold greater in dairy than meat kids.

Comparing the predictive ability of Sentinel-2 multispectral imagery and a proximal hyperspectral sensor for the estimation of pasture nutritive characteristics in an intensive rotational grazing system

Using remote sensing to estimate the nutritive characteristics of pasture in livestock systems is a rapidly developing area that has the potential to improve pasture management and utilisation and in turn improve livestock productivity. The Copernicus Sentinel-2 paired satellites have shown promise in predicting pasture nutritive characteristics and have a pixel size small enough to be able to identify intra-paddock nutrient variation in rotational dairy grazing systems where paddock sizes are small. This study sought to develop nutrient prediction models using a dataset of nine Sentinel-2A and -2B satellite images, by linking imagery to perennial ryegrass dairy pasture samples cut within known pixels of the images in the days directly after each cloud-free overpass. Just before destructive pasture sampling, a handheld, proximal, hyperspectral sensor was used to gather spectral signatures (400–2500 nm) from areas to be sampled. Pasture samples (n = 200) were analysed using wet chemistry techniques for seven nutritive characteristics. The dry matter concentration of the samples was also measured, creating eight variates to be modelled in total. The Sentinel-2 data from within the selected pixels was extracted and used to create input features for Random Forest prediction models. Input features included the raw multispectral bands, common vegetation indices, and independent variables ‘season’ and ‘month’. Predictive models were also developed from the hyperspectral sensor data using Partial Least Squares Regression. For both modelling types, variable selection was used to reduce model inputs to only those sensitive to each nutrient. Results comparing the final models in an independent validation test showed similar predictive performance of the Sentinel-2 satellite and the proximal hyperspectral sensor for all variates of interest, shown by mean absolute errors that were not significantly different. In each case, the dry matter concentration was the best predicted variable (Lin’s concordance correlation coefficient (LCCC) > 0.90) with excellent potential to be quantified by Sentinel-2 satellites. Crude protein, metabolisable energy, neutral detergent fibre, non-fibre carbohydrate, and water-soluble carbohydrate concentrations were also predicted with good to moderate accuracy by both sensors (LCCC between 0.50 and 0.80). These models would be sufficiently accurate for making qualitative predictions (e.g., grouping into high to low categories). Ash and acid detergent fibre concentrations were poorly predicted (LCCC < 0.50) and these models would not be recommended for further use. It was concluded that multispectral data from Sentinel-2 has great potential to estimate pasture nutrient concentrations for intensively grazed pastures such as those used in dairy systems in temperate regions.

Silvopastoral system is an alternative to improve animal welfare and productive performance in meat production systems

Climate change is a reality and global surface temperature is projected to rise substantially in the next 80 years. Agriculture practices will have to adapt to climate change, and also help to mitigate this effect using, among other strategies, forest conservation and management. Silvopastoral systems have been adopted in tropical climate livestock areas but their benefits on thermal comfort and reproductive performance of beef cows are not completely known. Therefore, our aims were to compare the microclimate of silvopastoral and intensive rotational unshaded grazing systems in different months and to evaluate physiological variables (Exp. 1 and 2), metabolism, and in vitro embryo production (Exp. 2) in crossbred beef females. Our hypothesis is that the silvopastoral system can improve the thermal comfort of beef heifers and cows and, consequently, also improve dry matter intake, body weight gain, and in vitro embryo production when compared to the unshaded rotational grazing system. In Exp 1, the silvopastoral system decreased body temperature and increased welfare and performance of heifers. In Exp. 2, the silvopastoral system enhanced the body weight but did not affect metabolism and the general reproductive performance, but increased the recovery rate of oocytes in primiparous cows.

Effect of high-intensity rotational grazing on the growth of cattle grazing buffel pasture in the Northern Territory and on soil carbon sequestration

Context Scientific and anecdotal reports conflict on the effects of intensive rotational grazing (IRG) on cattle growth, and very limited objective data are available from cattle grazing in northern Australia that producers can use to decide whether to adopt IRG. Aims This study aimed to compare liveweight gain and sequestration of soil organic carbon when cattle grazed buffel grass (Cenchrus ciliaris L.) under either continuous grazing (CG) or IRG. Methods In each year of this 9-year study, a cohort of Brahman and Brahman-cross weaners was randomly allocated to IRG and CG treatments. They grazed predominantly buffel pasture at Douglas Daly Research Farm from shortly after weaning for about a year, at which time they were replaced by the next year’s group, and the average liveweight gains of the treatments over the post-weaning year were compared each year for 9 years. Soil organic carbon was measured in the topsoil (0–30 cm) twice each year for 5 years (2009–14) and changes in carbon stocks over time were compared between treatments. Key results In each year of this study, the growth of cattle grazing buffel pasture was lower under IRG than CG. In each year, liveweight gain was lower (P &amp;lt; 0.05) per head and per hectare under IRG. Topsoil soil organic carbon stocks did not increase in the IRG treatment over the 5 years of this study. Conclusions This study found that cattle growth, both per head and per hectare, was lower under IRG than CG, and that IRG did not result in any increase in soil organic carbon over time. Implications The lower per head and per area production from the IRG system, combined with the extra infrastructure and operating costs for IRG systems, make it unlikely that adoption of IRG would improve the profitability of cattle-grazing operations on similar pasture systems in northern Australia. However, the findings of this study may not apply to other pasture systems and environments.

Forage management practices used in production of US grass-fed beef

ABSTRACT Objective Management of forage resources is critical to ensuring animals destined for the grass-fed beef (GFB) market have access to quality forage needed for growth and development for acceptable meat products. The objective of this study was to evaluate the forage management systems and species used by US GFB producers, adoption rates of rotational grazing systems, producers’ perceptions of the profitability associated with rotational grazing systems, and the economic effect of intensive grazing systems on GFB production costs and profitability. Materials and Methods A survey questionnaire was mailed to 1,052 US GFB producers to examine forage management systems used in US GFB production. A total of 384 completed questionnaires were received. An ordered probit model was used to determine the types of farms and demographics of producers more likely to be involved in an intensive rotational grazing system. Results and Discussion A total of 59 different forage species and types were listed in the study. In all US regions represented in the study, the average and median farm reported use of 3 to 4 forage species or types in their systems. More than half of the respondents indicated rotational grazing increased farm profit by greater than 20% relative to continuous grazing. Implications and Applications The level of rotational grazing differed by region with producers in the Pacific region rotating the least relative to others. Producer demographics and farm size also significantly affected the frequency of rotation.

Influence of intensive rearing, continuous and rotational grazing systems of management on parasitic load of lambs.

Aim:A trial was conducted to assess the influence of parasitic load on the lambs reared under the intensive system, continuous grazing, and rotational grazing systems of management.Materials and Methods:A total of thirty numbers of the undetermined breed of ewe lambs around 4-5 months of age were randomly selected and allotted to three treatment groups: T1 (intensive system – control), T2 (rotational grazing), and T3 (continuous grazing). The T1 group lambs were raised under a stall-fed system of management, the T2 group lambs were grazed under rotational grazing strategy in four paddocks of plot-A, while the T3 group lambs were continuously grazed in plot-B.Results:At the end of the study, there was a highly significant difference (p=0.01) in the fortnightly strongyle egg count per gram (EPG) of feces among the lambs pertaining to the three treatment groups; the lambs in T3 had a higher strongyle EPG compared to T2 lambs. With regard to the overall reduction in EPG from the initial count, lambs under rotational grazing showed the maximum decrease of 54.52% compared to lambs under T3 (continuous grazing). There was a strong positive correlation noticed between the mean temperature of the day at each fortnight and the subsequent EPG at each fortnight with R2=0.87. There was a strong positive correlation noticed between mean FAMACHA© scores and the EPG with R2=0.84, R2=0.83, and R2=0.83 for T1, T2, and T3, respectively.Conclusion:The grazing management with pasture rotation should be considered as a viable option for sustainable parasitic control in case of grazing-dependent livestock husbandry in India.

Longer rest periods for intensive rotational grazing limit diet quality of sheep without enhancing environmental benefits

Intensive rotational grazing systems (also called cell grazing, holistic grazing or time-controlled grazing) are often implemented to improve production and environmental outcomes. Over recent years there has been considerable interpretation and adaption of the holistic principles that guide the management of these systems. In southern Australia, this has led to an increasing use of longer rest periods for intensive rotational grazing. This experiment was established to compare three intensive rotational grazing strategies (fast rotation [FR], average 57-day rest; slow rotation [SR], average 114-day rest; and flexible grazing [FX], based on availability of green herbage mass) with continuous grazing (CG) to assess the impact these systems have on vegetation and diet quality. The grazing treatments were run across three production zones (PZs) in the landscape (low [LPZ], medium [MPZ] and high [HPZ]) to determine whether management by landscape interactions influenced vegetation. Pasture composition was mostly influenced by PZ in the landscape with Microlaena stipoides and Holcus lanatus more prevalent in the HPZ and Rytidosperma spp. more common in the LPZ. The intensive rotational grazing treatments all had greater herbage mass and ground cover than CG. Composition change often occurred in one PZ and not another (e.g. Hypochaeris radicata increased with SR in the LPZ), or there were contrasting effects in different parts of the landscape (e.g. M. stipoides increased with FR compared with CG in the HPZ but decreased in the LPZ). Diet quality was lower for the SR compared with the other grazing treatments. Maintaining a post-grazing benchmark of >0.5 t green DM ha−1 was associated with a higher diet quality. Based on this two-and-a-half-year study run during poor seasons, it can be concluded that intensive rotational grazing can be managed, with fast and flexible rotations, to achieve per head animal performance similar to CG, but with higher herbage mass, ground cover and a desirable pasture composition.

Better management of intensive rotational grazing systems maintains pastures and improves animal performance

Grazing management has been identified as a means of increasing livestock production and improving the composition of perennial pastures. The benefits of intensive rotational grazing have been the subject of much debate, but few studies have evaluated contrasting management of intensive rotational systems. A grazing management experiment was established on a pasture with cocksfoot (Dactylis glomerata L., varieties Porto and Kara) as the dominant species, to investigate different stocking rates, paddock numbers and rotation speeds, and a flexible treatment that adjusted grazing time, rest periods and stock numbers for optimal pasture utilisation. Data were collected on pasture composition and diet quality assessed by using faecal analysis, animal weight changes and pasture characteristics. Animal production per hectare was greatest for fast rotations (56 days’ rest) at high stocking rates (HStR, 13.6 dry sheep equivalents (DSE) ha–1), but continuous grazing (CG) was equally productive. Although flexible grazing based on the 3–4-leaf stage was proposed as the best balance between pasture production and quality, this treatment had lower stocking rates (9.2 DSE ha–1) and was not as productive. No treatment negatively affected pasture composition over the 4-year period. Area of bare ground was highest for the HStR CG treatment; however, the 30-paddock rotations were able to limit bare ground at the same stocking rate. The results indicated that intensive rotational grazing could be effectively managed by using green herbage allowance. In spring, green herbage allowance needed to be 1–1.5 kg green dry matter (DM) DSE–1 day–1, which increased to 5 kg green DM DSE–1 day–1 as the quality of green DM decreased, to allow selective grazing to enhance diet quality.

Role of host and environment in mediating reduced gastrointestinal nematode infections in sheep due to intensive rotational grazing

We have previously reported marked reductions in faecal worm egg counts (WECs) and drenching frequency in sheep on an intensive rotational grazing system (IRG) in a cool temperate environment with summer-dominant rainfall. These experiments were designed to determine the role of the host and environmental factors in mediating this. The role of host factors was investigated by administering a fixed larval challenge in each of the 4 seasons of the year to groups of 20 young sheep on three different management systems, including IRG. This comprised a mixed larval challenge containing infective larvae of Haemonchus contortus and Trichostrongylus colubriformis 7 days after short-acting anthelmintic treatment. A range of measurements was then made up to day 35 post-challenge. The role of environmental factors was determined by assessing pasture infectivity in four seasons using faecal worm egg counts (WECs) and pooled faecal culture of worm-free tracer sheep. The management systems were high input (HI) with high fertiliser inputs high stocking rate and relatively long grazing periods; typical New England management system (TYP) with moderate fertiliser inputs and stocking rate and relatively long grazing periods and; Intensive rotational grazing (IRG) with moderate fertiliser inputs and stocking rate but very short (mean 5 days) grazing periods and long (mean 103 days) rest periods. IRG sheep had higher mean WEC at 28 and 35 days after fixed larval challenge than HI and TYP sheep in spring (IRG: 9500±1000; HI: 4000±1000; TYP: 7200±1000 eggs/g, P<0.01) and summer (IRG: 8400±750; HI: 5300±800; TYP: 4400±700 eggs/g; P<0.001) and also had lower liveweights during these seasons. There was no difference in WEC after the autumn challenge (IRG: 5100±450 HI: 4500±450; TYP: 4200±450 eggs/g; P∼0.36) but IRG had lower WEC than TYP following the winter challenge (IRG: 2900±400; HI: 2300±400; TYP: 4300±400eggs/g, P<0.01). The tracer sheep (used to determine pasture infectivity) on IRG had significantly lower WECs during winter, spring and summer than those under the other management systems. Faecal culture and larval differentiation revealed that faeces from tracers on IRG contained significantly lower proportions of H. contortus and significantly higher proportions of Trichostrongylus spp. and Teladorsagia circumcincta than faeces from tracers on the HI and TYP treatments. Thus, when IRG was most efficacious for worm control, during spring and summer when short graze and long rest periods were maintained, sheep on this system exhibited greater susceptibility to larval challenge while tracer sheep indicated lower pasture infectivity. This demonstrates that the effects of IRG on WEC are mediated by reduced larval challenge rather than increased host resistance to infection.

Efectos ambientales y parámetros genéticos de variables de crecimiento para un rebaño de ciervo rojo (Cervus elaphus) en cautiverio

The objective was to estimate environmental effects and genetic parameters on growth traits in a flock of farmed red deer of the central Mexican highland. Animals were raised on an intensive rotational grazing system of grass-legume mixed temperate pastures. Evaluated traits were birth (BW), weaning adjusted to 100 d (WW) and yearling (YW) weights. Analyses were performed using the MTDFREML program.

Meadow Fescue, Tall Fescue, and Orchardgrass Response to Defoliation Management

Meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.] represents an alternative to temperate grasses typically used in forage‐livestock systems. Our objective was to compare the productivity, nutritive value, and persistence of diverse meadow fescue cultivars with that of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] and orchardgrass (Dactylis glomerata L.) when harvested by regimes representing lax and severe hay production and rotational grazing. ‘Azov’ (plant introduction strain cross), ‘Bartura’ (commercial cultivar), and ‘Hidden Valley’ (naturalized population) meadow fescue, ‘Barolex’ tall fescue, and ‘Bronc’ orchardgrass were harvested infrequently (40‐ to 65‐d harvest interval) or frequently (when plants reached 25‐cm sward height) to a 5‐ or 10‐cm residual sward height (RSH) at two Wisconsin locations in 2 yr. Annual dry matter (DM) yield of all grasses was greater when harvested infrequently (7.46 Mg ha−1) than frequently (5.92 Mg ha−1), or at 5 cm (7.52 Mg ha−1) than 10‐cm RSH (5.88 Mg ha−1). Tall fescue and orchardgrass annual yield was greater than that of all meadow fescues when harvested infrequently, but differences among grasses were relatively small when harvested frequently, particularly at 10‐cm RSH. Neutral detergent fiber digestibility (NDFD) of meadow fescue was 30 to 80 g kg−1 neutral detergent fiber (NDF) greater than that of tall fescue or orchardgrass at every harvest in all environments. Meadow fescue cultivars were less persistent than tall fescue after 2 yr, but were usually equal to or more persistent than orchardgrass. Meadow fescue should be considered as a viable alternative to tall fescue and orchardgrass in temperate, managed intensive rotational grazing systems due to its comparable yield and superior digestibility.

Feasibility of Seed Production from Nonflowering Orchardgrass

ABSTRACTNonflowering or sparse flowering orchardgrass (Dactylis glomerata L.) would greatly simplify management of intensive rotational grazing systems. Our objective was to quantify seed production on nonflowering orchardgrass clones selected in cold‐winter climates, but grown for seed in mild‐winter climates. We evaluated 98 orchardgrass clones for seed production traits at four locations. Most plants (∼92%) flowered at the three northern locations, but only 38% flowered at Parlier, which may have a winter insufficiently cold for adequate floral induction and vernalization. Mean panicle number was lowest (11%) for plants selected at the location with the warmest winter conditions, and highest (37%) for plants selected at the location with the coldest winter conditions. These results confirm our expectations that the most desirable plants (nonflowering under cold winters and normal flowering under mild winters) should arise from selection under more severe winters. Selection for nonflowering under mild winter conditions simply leads to nonflowering plants under all conditions. These results demonstrate that individual orchardgrass genotypes are capable of dual phenotypic expression, flowering in mild‐winter climates or expressing the nonflowering trait in cold‐winter climates and that the expression of this trait depends on both the selection and evaluation location.

Farm returns to carbon credit creation with intensive rotational grazing

Intensive rotational grazing systems may produce multiple environmental services, including reduction of the emissions of greenhouse gases (GHG). This study investigates potential GHG emission reduction credits obtained by converting Virginia cow-calf and dairy farm operations from conventional grazing operations to rotational grazing. The quantity and value of the change in GHG emissions are estimated using new US Department of Energy guidelines. Credits are estimated under three boundary conditions and two accounting metrics. Results suggest conversion to rotational grazing can generate GHG reduction credits, but the financial benefits farms receive from emissions reductions are modest. The amount of credits received is sensitive to choice of accounting metric and boundary definition.

Intensive rotational grazing assists control of gastrointestinal nematodosis of sheep in a cool temperate environment with summer-dominant rainfall

While rotational grazing methods have an accepted role in the management of gastrointestinal nematodosis (GIN) of small ruminants in humid tropical regions, their efficacy and application in cool temperate regions is more controversial. This study evaluated GIN over 2 years in three classes of fine wool Merino sheep (lambs, hoggets and ewes) under three different sheep management systems in a cool tableland environment near Armidale NSW Australia (950 m altitude, 30°31′S, 151°39′E). The management systems were High input (HI) with high fertiliser inputs, a target of 100% sown pasture, high stocking rate (13.4 dry sheep equivalents/ha) and relatively long grazing periods; Typical (TYP) New England management system with moderate fertiliser inputs and stocking rate (9.3 DSE/ha) and relatively long grazing periods; and Intensive rotational grazing (IRG) with moderate fertiliser inputs and stocking rate (8.8 DSE/ha) but very short (mean 5 days) grazing periods and long (mean 103 days) rest periods. Twenty sheep of each class in each management treatment were sampled monthly for faecal worm egg counts (WEC, followed by larval differentiation), and body weights with a blood sample taken for haematology every second month. The proportion of sheep with WEC above zero did not differ between management systems but the magnitude of WEC did, with sheep under IRG displaying lower mean WEC than those on the other treatments (IRG: 326, HI: 594, TYP: 536, eggs/g P < 0.0001). This was despite a significantly longer mean interval between anthelmintic treatments (IRG: 144 days, HI: 77 days, TYP: 78 days, P < 0.0001). The IRG management system also influenced the composition of the infections with sheep on this treatment having a significantly lower proportion of Haemonchus contortus in their faecal cultures (IRG: 59.7%, HI: 79.4%, TYP: 80.9%, P < 0.05) and a significantly higher proportion of Trichostrongylus spp. Sheep on the IRG treatment also had a significantly higher haematocrit (HCT) than those on the other management systems. Despite the lower WEC and higher HCT, sheep under IRG also had significantly lower bodyweights and fleece weights overall, although this was only evident in sheep raised to adulthood prior to the experiment, not those raised during the 2-year experimental period. The results demonstrate that IRG systems with short grazing periods and long rest periods between grazing events can assist with control of GIN in cool temperate climates where H. contortus is the dominant parasite.

Rotational grazing system for beef cows on dwarf napiergrass pasture oversown with Italian ryegrass for 2 years after establishment

AbstractWe examined an intensive rotational grazing system for dwarf and late‐heading (DL) napiergrass (Pennisetum purpureum Schumach) pasture in a summer period, and an oversown Italian ryegrass (IR) pasture in a winter period for the 2 years following establishment. Four 0.05‐ha paddocks of DL napiergrass pasture (20 m × 25 m) were established on 6 May 2002. They were rotationally grazed for 1 week, followed by a 3‐week rest period by 2–3 breeding or raising beef cattle (Japanese‐Black) for three and six cycles in a summer period during the first and second years of establishment, respectively. In the IR pasture, which was established by oversowing IR in both years, rotational grazing by 3–4 animals was conducted in March and April for two cycles of grazing for 1–2 days in each paddock in 2003 and for 3–5 days in all four paddocks in 2004. In the DL napiergrass pasture before grazing, the plant height, leaf area index and the ratio of leaf blade to stem were highest in the hot summer season, while tiller number increased and herbage mass tended to increase as grazing occurred, except for the first grazing cycle both years, and for one paddock in the second year. Herbage consumption, rate of herbage consumption and dry matter intake tended to decrease in three paddocks from the first to the third cycle in the first year, while herbage consumption and rate of herbage consumption tended to increase as grazing occurred in the second year. Dry matter intake averaged 10.2–14.5 and 15.4–23.2 g DM kg−1 liveweight (LW) day−1 over the four paddocks in the first and second year, respectively, and average daily gains were 0.09 and 0.35 kg head−1 day−1 in the first and second year, respectively. In the oversown IR pasture, herbage consumption tended to increase as grazing occurred, and the average daily gains were 1.49 and 1.36 kg head−1 day−1 in 2003 and 2004, respectively, except for the LW decrease during the first cycle in early March 2004. The carrying capacities on DL napiergrass pasture and IR pasture were estimated at 1016 and 208 cow‐days (CD) ha−1, respectively (annual total 1224 CD ha−1) in the first year and at 1355 and 207 CD ha−1, respectively (annual total 1562 CD ha−1) in the second year. Thus, DL napiergrass pasture oversown with IR can expand the grazing period for beef cows to late November, March and April, in addition to the summer season for the 2 years following establishment.

Intervalo hídrico ótimo na avaliação de sistemas de pastejo contínuo e rotacionado

A qualidade física do solo sob sistemas de pastejo contínuo e rotacionado foi avaliada pelo Intervalo Hídrico Ótimo (IHO). A amostragem foi realizada na área experimental da Embrapa Gado de Corte. Foi estudado um Latossolo Vermelho distrófico. Foram avaliados quatro piquetes, sendo dois no sistema de pastejo contínuo e dois no sistema de pastejo rotacionado. No sistema de pastejo contínuo, implementado com a espécie Brachiaria decumbens cv. Basilisk, foram retiradas 30 amostras por piquete, não tendo um dos piquetes recebido adubação de manutenção (Cs), enquanto o outro havia recebido adubação bianual de manutenção (Cc). No sistema de pastejo rotacionado, implementado com a espécie Panicum maximum cv. Tanzânia, foram retiradas 30 amostras por piquete; em um dos piquetes, o resíduo pós-pastejo era mantido entre 2,0 e 2,5 t ha-1 de matéria seca total (MST) (R1), enquanto no outro era mantido entre 3,0 e 3,5 t ha-1 MST (R2). As amostras foram submetidas a um gradiente de tensão de água e, posteriormente, utilizadas nas determinações da densidade do solo (Ds), resistência do solo à penetração (RP), umidade volumétrica (tetav) e do IHO. O sistema de pastejo rotacionado apresentou piores condições físicas do solo para o crescimento vegetal, avaliadas pelo critério do IHO. Os maiores valores de Ds e menor IHO foram observados no R1, o que foi atribuído às taxas de lotação mais elevadas aplicadas neste piquete.

Cattle herbage utilization patterns under high-density rotational grazing in the Aspen Parkland

Native Aspen Parkland landscapes consist of a complex mosaic of plant communities, including riparian meadows, upland grasslands, and forests. Sustainable livestock production in this environment depends on an understanding of livestock grazing behavior among communities, particularly under contemporary, intensive management rotational grazing systems. This study examined seasonal patterns of absolute (kg ha-1) and relative (%) herbage utilization, as well as plant community visitation, across a Parkland landscape by 150 heifers in two rotations of a high-intensity, low-frequency grazing system. Graminoids constituted more than 92% of the total herbage utilized. Absolute graminoid utilization within each grazing period was greater (P &lt; 0.05) throughout the growing season from riparian meadows (2003 to 2114 kg ha-1) than from upland grasslands (762 to 1041 kg ha-1) or forests (782 to 800 kg ha-1). In contrast, relative graminoid utilization remained similar (P &gt; 0.05) among communities in either rotation, suggesting heifers grazed in proportion to graminoid availability (57–61% in first rotation, 44–54% in second rotation). Although riparian meadows represented a small fraction of the landscape (~ 4%), and provided up to 9.5% of the total forage used, the majority of herbage removal at the paddock level continued to originate from upland grasslands and forests. Patterns of visitation indicated heifers initially visited riparian meadows more often within each 3–4 day grazing period, regardless of entry date. While upland grasslands were least visited in June, forests were least visited in August. Based on these utilization and visitation patterns, we discuss the implications of using high-density, rotational livestock grazing for the sustainable management of Aspen Parkland rangelands. Key words: Aspen forest, cattle grazing, forage quality, herbage utilization, riparian meadow, rotational grazing, upland grassland

Consequences of Post-grazing Residues Control and Birth Season on the Body Traits, Reproductive Performance and Offspring’s Growth of Suckling Goats and Ewes Reared at Pasture in Guadeloupe (FWI)

In Guadeloupe small ruminants (SR) are reared for meat production under pasture conditions. Intensive rotational grazing systems (irrigated, fertilised and high stocked) allow reasonable levels of production but generate high post-grazing residues. Experiments were designed to control them. A system in which residuals were mown (RM) was tested in comparison to the control system (Residuals Remained, RR). The same design was carried out for two years with Creole goat (G) and Martinik sheep (S). An accelerated reproductive rate (3 parturitions over 2 years) was carried out. Systems were compared at three parturition seasons per year (dry, intermediate and rainy seasons). Each group was composed of 20 goats (36.0±2.5 kg) or 20 ewes (46.8±2.4 kg). The female body traits did not vary according to pasture management and seasons. The stocking rate averaged 1,400 kg LW/ha. The mean fertility rate for does varied significantly (p<0.05) within the kidding season, from 80.4±0.5% to 93.7±2.9% while the mean litter size was 2.30±0.07 total kids born. No effect of pasture system was observed. Corresponding values for ewes were 83.2±12.8% vs. 75.6±12.5% (p<0.05) and 2.43±0.24 vs. 2.03±0.29 (p<0.01) total lambs born for SRM and SRR ewes, respectively. A seasonal effect was observed upon ewe performances. The preweaning mortality of kids and lambs averaged 16.3% and 14.4%, respectively. It was 7 and 9 percentage points more (p<0.01) for RR than for RM kids and lambs, respectively. For both species, weaning took place at an average age of 81.4±3.6 days. In Creole kids, live weight at birth and at weaning were 1.9±0.2 kg and 8.9±0.8 kg, respectively. In the Martinik sheep, the traits averaged 2.9±0.2 kg and 18.9±0.9 kg. For both traits in both species, significant (p<0.05) group×season interactions were recorded. The consequences of elimination of post-grazing residues varied according to the SR species, the environmental conditions and the animal physiological status. The forage characteristics were not limiting factors since forage availability in the RM systems (2,300 and 2,600 kg DM/ha, respectively) and chemical composition were at satisfactory levels (CP content averaged 12 and 10%). It is recommended to develop new grazing system which would allow the use of post-grazing residues instead of mowing the refusals. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 8 : 1108-1117)

Association of herd composition, stocking rate, and duration of calving season with fecal shedding of Cryptosporidium parvum oocysts in beef herds

Objective To evaluate the association of herd demographics, parturition variables, stocking rate, and rotational grazing practices with the probability of fecal shedding of Cryptosporidium parvum from beef cow-calf herds in California. Design Cross-sectional study. Sample Population 38 beef cow-calf operations. Procedure Fecal specimens were collected and examined for C parvum oocysts, using immunofluorescent microscopy. Association between various demographic and management factors and the probability of shedding C parvum were statistically evaluated. Results Adjusted for age and month of collection of a fecal sample, cattle from herds with a high number of young calves (≤ 2 months old) on the day of sample collection, a high stocking rate (No. of cattle/acre/mo), or a longer calving season were more likely to shed C parvum oocysts, compared with cattle from herds with fewer young calves, a lower stocking rate, or a shorter calving season. Cattle from herds with a higher number of older calves (&gt; 2 months old) on the day of sample collection were less likely to shed C parvum oocysts, compared with cattle from herds with fewer older calves. Using our multivariate model, rotational grazing systems or season of onset of calving were not associated with shedding status for C parvum oocysts. Conclusions and Clinical Relevance Reproductive management that would result in a shorter calving season and use of a lower stocking rate for cattle may be associated with reduced risk of C parvum shedding. Intensive rotational grazing systems and time of year for onset of calving season apparently have little effect on reducing prevalence of oocyst shedding. (J Am Vet Med Assoc 1999;215:1833–1838)

Impacts of forage grazing and cultivation on near-surface relative compaction

The study was conducted at the Lacombe Research Station, Alberta, on an Orthic Black Chernozem of loam to silt loam texture to investigate grazing impacts and cultivation on near-surface soil compaction. Four forages, smooth bromegrass (Bromus inermis Leyss 'Carlton'), meadow bromegrass (Bromus riparius Rhem 'Paddock'), a mixture of triticale (X Triticosecale Wittmack 'Pika') and barley (Hordeum vulgare L. AC Lacombe), and triticale were used for the study. Each forage species was subjected to heavy, medium and light intensity grazing. Measurements of bulk density and volumetric moisture content for the 0- to 10-cm depth interval were conducted using a surface moisture-density probe between spring 1994 and fall 1996. Relative compaction was calculated as the actual bulk density expressed as a percentage of the Proctor maximum density. Relative compaction values for all treatments and that for the benchmark were less than 90%, which is considered critical for limiting plant growth. Cultivation reduced bulk density under annual forages by only 3% and lowered it under heavy grazed annual treatments most. Regression analysis conducted on the dependence of bulk density to cumulative cow-days indicated a curvilinear relationship. Bulk density increased more rapidly with increasing cumulative cow-days for annuals compared to perennials. From a management perspective, adopting intensive rotational grazing systems for perennial and annual forages may not cause any serious surface compaction problems for soils in this area. Key words: Annuals, bulk density, cow-days, grazing intensity, perennials, volumetric moisture content