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Grazing Period (grazing + period)

Distribution by Scientific Domains

Life Sciences	42%

Selected Abstracts

Modelling the concentrations of nitrogen and water-soluble carbohydrates in grass herbage ingested by cattle under strip-grazing management

GRASS & FORAGE SCIENCE, Issue 1 2008
N. J. Hoekstra
Abstract There is scope of increasing the nitrogen (N) efficiency of grazing cattle through manipulation of the energy and N concentrations in the herbage ingested. Because of asymmetric grazing by cattle between individual plant parts, it has not yet been established how this translates into the concentrations of N and water-soluble carbohydrates (WSC) in the herbage ingested. A model is described with the objective of assessing the efficacy of individual tools in grassland management in manipulating the WSC and N concentrations of the herbage ingested by cattle under strip-grazing management throughout the growing season. The model was calibrated and independently evaluated for early (April), mid- (June, regrowth phase) and late (September) parts of the growing season. There was a high correlation between predicted and observed WSC concentrations in the ingested herbage (R2 = 0·78, P < 0·001). The correlation between predicted and observed neutral-detergent fibre (NDF) concentrations in the ingested herbage was lower (R2 = 0·49, P < 0·05) with a small absolute bias. Differences in the N concentration between laminae and sheaths, and between clean patches and fouled patches, were adequately simulated and it was concluded that the model could be used to assess the efficacy of grassland management tools for manipulating the WSC and N concentrations in the ingested herbage. Model application showed that reduced rates of application of N fertilizer and longer rotation lengths were effective tools for manipulating herbage quality in early and mid-season. During the later part of the growing season, the large proportion of area affected by dung and urine reduced the effect of application rate of N fertilizer on herbage quality. In contrast, relative differences between high-sugar and low-sugar cultivars of perennial ryegrass were largest during this period. This suggests that high-sugar cultivars may be an important tool in increasing N efficiency by cattle when risks of N losses to water bodies are largest. The model output showed that defoliation height affects the chemical composition of the ingested herbage of both the current and the subsequent grazing period. [source]

Setting management limits for the production and utilization of herbage for out-of-season grazing

GRASS & FORAGE SCIENCE, Issue 1 2000
Laidlaw
Three experiments were carried out on perennial ryegrass-dominant swards to provide a basis for recommendations for the limits to (a) building up and timing of utilization of a herbage ,bank' for out-of-season grazing and (b) duration and intensity of early spring grazing in the United Kingdom and Ireland. In experiment 1, the effect of regrowth interval (from 7 September, 20 October, 17 November or 15 December) in autumn on herbage accumulation, leaf turnover and on subsequent spring growth was investigated. Swards regrown from early September reached maximum herbage mass (about 3 t ha,1 DM) and leaf lamina content in mid-November, by which time senescence rate exceeded rate of production of new leaves. New leaf production and senescence rates were greater in swards remaining uncut until December than in those cut in October or November. Time of defoliation up to December had no effect on spring herbage mass in the subsequent spring. Defoliating in March reduced herbage mass in late May by less than 20%. Experiment 2 investigated the progress in herbage growth and senescence in swards regrowing from different times in late summer and autumn to produce herbage for utilization beyond the normal grazing season. Treatments in a randomized block design with three replicates were regrowths from 19 July, 8 August, 30 August and 20 September. Based on a lower ceiling of leaf and total herbage mass being reached with progressively later regrowths, beyond which leaf senescence generally exceeded leaf production and herbage mass declined, it was concluded that currently recommended rotation lengths for this period should extend from 3 weeks in late July to 8 weeks for swards previously grazed in mid-September. In both experiments, leaf senescence commenced earlier (by one leaf-age category) than previously published estimates and so brought forward the time at which senescence rates balanced leaf growth rates. In experiment 3, designed to evaluate the effect of daily grazing period and intensity in early spring on herbage regrowth, dairy cows grazed successive plots (replicates) for 2 or 4 h each day at two intensities (target residual heights of 5 or 7 cm) in March to mid-April. Regrowth rate was similar in all treatments including the ungrazed control, despite soil moisture content being relatively high on occasions. Tiller density was significantly reduced in May by grazing plots in early or mid-April. It is concluded that in autumn there are limits to which rotation lengths should be extended to produce herbage for out-of-season grazing owing to attainment of ceiling yields. Although utilization in early spring may reduce herbage availability in spring, out-of-season utilization need not reduce herbage growth rates in early spring. [source]

Influence of body condition and forage type on prevalence of Escherichia coli O157:H7 and Salmonella in grazing beef cows

LETTERS IN APPLIED MICROBIOLOGY, Issue 3 2009
M.L. Looper
Abstract Aim:, To determine the influence of body condition (BC) and forage type on the prevalence of faecal shedding of Escherichia coli O157:H7 and Salmonella from beef cows. Methods and Results:, Thin or moderately conditioned cows (n = 115) were randomly assigned to graze either common bermudagrass (n = 3 pastures) or toxic endophyte-infected tall fescue (n = 3 pastures) for 62 days. Faecal samples were collected on day 0, 30 and 62. Overall percentage of faecal samples positive for E. coli O157:H7 was 2·6% and 2·0% for Salmonella. Percentage of cows positive for both E. coli O157:H7 and Salmonella on at least one occasion was 6·1%. BC, forage type or the interaction did not influence the prevalence of E. coli O157:H7 or Salmonella in the faeces of cows. Conclusions:, BC at initiation of the grazing period or loss of BC in moderate conditioned cows during the grazing period did not influence faecal shedding of E. coli O157:H7 or Salmonella. Consumption of either forage type did not influence faecal shedding of either E. coli O157:H7 or Salmonella in beef cows of thin or moderate BC. Significance and Impact of the Study:, Change in BC that typically occurs during the normal production cycle in grazing cows did not influence faecal shedding of pathogenic bacteria regardless of forage type. [source]

Effects of herbage intake on goat performance in the mediterranean type natural pastures

ANIMAL SCIENCE JOURNAL, Issue 1 2009
Basri H. HAKYEMEZ
ABSTRACT This study aimed at identifying changes in natural pastures during the grazing season and investigating the effects of these changes on pasture feeding potential for high yielding dairy goats. During the study, 12 dairy goats were grazed on a 1.5 ha natural pasture for three months from April to June in 2003, 2004 and 2005. The goats were fed 0.5 kg/day of concentrate as a supplement during the grazing season. Botanical composition, herbage production and intake, crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of the pasture were determined. Live weight, milk yield, milk dry matter (DM) and fat content of the goats were monitored. The data were analyzed using a linear model, which evaluated the effects of grazing seasons in each year. Based on the three-year average, 87% of pasture was herbaceous plants and the remaining was shrubs in DM basis with Cistus creticus, Quercus ithaburensis, Pistacia atlantica and Asparagus acutifolius being the major shrub species. The herbage yield in June was significantly lower than in other months in all years (P = 0.001). In all experimental years, the CP content of the pasture decreased but the structural carbohydrates increased as the grazing season proceeded. While live weight was not affected by grazing periods except for 2004 (P = 0.001), milk yield significantly decreased with advancing grazing period (P = 0.001). The results of the present study indicate that natural pasture has a supportive effect in April and May on the milk yield of lactating goats which are in mid-lactation, and suggested that supplementary feeding is required in consecutive grazing periods. [source]

Trichostrongylid infections in sheep after rainfall during summer in southern Australia

AUSTRALIAN VETERINARY JOURNAL, Issue 9 2002
P NIVEN
Objective To relate trichostrongylid infections acquired by sheep during summer to prevailing weather conditions. Procedure Groups of worm-free ,tracer' sheep were put onto pastures, previously contaminated with trichostrongylid eggs, for successive periods of 2 weeks from December to March. After grazing the sheep were housed for 6 weeks. Weekly worm egg counts and worm counts were used to estimate the numbers of worms acquired and related to weather conditions during the grazing period. Results No worm eggs were detected in the faeces of sheep that grazed at the end of January when only 7 mm of rainfall was recorded. At other times rainfall between 12 and 24 mm occurred and strongyle egg counts were generally either < 50 or > 150 eggs per g (epg). Mean counts of 1100 Ostertagia and Trichostrongylus adults gave rise to mean counts of about 350 epg whereas about 6000 Nematodirus spp were associated with mean egg counts of about 200 Nematodirus spp epg. Conclusions Rainfall events during summer determine the numbers of trichostrongylid larvae acquired by sheep in summer but further studies are necessary before the implications for strategic control programs in southern Australia can be fully assessed. [source]

Seasonal changes in herbage mass and nutritive value of a range of grazed legume swards under Mediterranean and cool temperate conditions

GRASS & FORAGE SCIENCE, Issue 3 2007
U. Sölter
Summary Seasonal changes in herbage mass and herbage quality of legume-based swards under grazing by sheep or cattle were investigated at four locations in climatically different zones of Europe: Sardinia (Italy), southern France, northern Germany and south-west England (UK). At each location standard treatments were applied to legumes typical of species widely used in each locality: Medicago polymorpha in Italy, Medicago sativa in France, and Trifolium repens in Germany and in UK. At each site comparisons were made of two other legumes: Trifolium subterraneum and Hedysarum coronarium in Italy, Onobrychis sativa and Trifolium incarnatum in France, Trifolium pratense and Lotus corniculatus in Germany, and Trifolium ambiguum and L. corniculatus in UK. Legumes were sown in mixture with locally appropriate companion grasses, and measurements were made over two or three grazing periods. In Italy M. polymorpha swards gave the greatest herbage mass in grazing period 1 but H. coronarium was more persistent. At the French site all legumes established poorly with no significant herbage mass differences between treatments. At both the UK and German sites L. corniculatus maintained a high proportion of legume in the sward; T. repens showed poor persistence under continuous sheep grazing in UK but persisted under cattle grazing in Germany, while T. ambiguum was slow to establish in the UK, and T. pratense proved to be of comparable herbage mass to the standard T. repens -based sward in the last year of the experiment. The concentration of crude protein and in vitro digestibility of organic matter in the dry matter of herbage showed greater within-season variation than between treatments at each site. It is concluded that, in addition to currently used species, legume-based swards containing H. coronarium, O. sativa and L. corniculatus all have potential to contribute to forage production for low-input grazing and their use merits further consideration in systems of livestock production in Europe. [source]