			Home About us Contact

Grazing Season (grazing + season)

Distribution by Scientific Domains

Earth and Environmental Science	81%

Selected Abstracts

Herbage growth rates on heterogeneous swards as influenced by sward-height classes

GRASS & FORAGE SCIENCE, Issue 1 2009
ahin Demirba
Abstract The contribution of four classes of sward height to daily herbage growth rates of a heterogeneous sward in eight periods throughout a grazing season was investigated in two continuous cattle-grazing systems differing in intensity (moderate stocking rate: MC; lenient stocking rate: LC). At the beginning and end of periods of 12 to 28 d, the compressed sward height (CSH) was measured in exclusion cages at eighteen fixed points per cage to derive daily growth rates for the four classes of sward height. Stratified calibrations were made to relate sward height to herbage mass for each treatment in each period. Quadratic regressions described the relationship between herbage growth rate and initial CSH for each treatment in each period. For scaling up to the scale of the plot, CSH was measured monthly at 100 points per plot. Daily herbage growth rates declined from more than 100 kg dry matter (DM) ha,1 d,1 on both treatments at the beginning of the grazing season to 20 kg DM ha,1 d,1 or less, especially on treatment LC. This was due to the larger area covered by tall herbage on treatment LC than on treatment MC. On treatment MC, daily herbage growth rate was predominantly derived from short sward areas of up to 12 cm in height while sward areas taller than 12 cm contributed most to daily growth rates on treatment LC in early summer. The method used is considered suitable for estimating daily herbage growth rates of different classes of sward height in extensively managed pastures and can easily be adapted to deal with more heterogeneous swards than used in this study. [source]

Estimation of nitrogen concentration and in vitro dry matter digestibility of herbage of warm-season grass pastures from canopy hyperspectral reflectance measurements

GRASS & FORAGE SCIENCE, Issue 2 2008
P. J. Starks
Abstract Remote sensing of nitrogen (N) concentration and in vitro dry matter digestibility (IVDMD) in herbage can help livestock managers make timely decisions for adjusting stocking rate and managing pastures during the grazing season. Traditional laboratory analyses of N and IVDMD are time-consuming and costly. Non-destructive measurements of canopy hyperspectral reflectance of pasture may provide a rapid and inexpensive means of estimating these measures of nutritive value. Using a portable spectroradiometer, canopy reflectance was measured in eight warm-season grass pastures in the USA in June and July in 2002 and 2003 to develop and validate algorithms for estimating N concentration and IVDMD of herbage. Nitrogen concentration of herbage was linearly correlated (r = 0·82; P < 0·001) with a ratio of reflectance in the 705- and 1685-nm wavebands (R705/R1685) and IVDMD was correlated with R705/R535 (r = 0·74; P < 0·001). Compared with simple linear regressions of N concentration and IVDMD in herbage with two-waveband reflectance ratios, multiple regression, using maximum r2 improvement, band-depth analysis with step-wise regression, and partial least-squares regression enhanced the correlation between N concentration and IVDMD of herbage and canopy reflectance values (0·81 , |r| , 0·90; P < 0·001). Validation of the prediction equations indicated that multiple regression only slightly improved accuracy of a model for predicting N concentration and IVDMD of herbage compared with simple linear regression of reflectance ratios. Results suggest that the N concentration and IVDMD of herbage of warm-season grass pastures can be rapidly and non-destructively estimated during the grazing season using canopy reflectance in a few narrow wavebands. [source]

Diet selection of dry and lactating beef cows grazing extensive pastures in late autumn

GRASS & FORAGE SCIENCE, Issue 4 2006
A. Farruggia
Abstract The diet selection, made by twelve dry and twelve lactating spring-calving Salers beef cows at the end of the grazing season on an extensively grazed natural mountain pasture in central France, was compared. Sward structure, selection bites, daily grazing time and digestibility of the diet were measured in mid-October (P1) and mid-November (P2). Live weights were measured twice monthly throughout the experiment. Daily milk production was assessed in the week before the grazing behaviour measurements. Lactating cows grazed more selectively than dry cows: they took more bites on green patches (0·20 vs. 0·13 of total bites, P < 0·01; Jacob's selectivity index: 0·13 vs. ,0·25, P < 0·001), which is consistent with the higher overall nitrogen concentration in faeces (18·1 vs. 17·3 g kg,1 DM, P < 0·05). Lactating cows tended to slightly increase their daily grazing time compared with dry cows (on average 9·9 vs. 9·5 h, P = 0·07) and grazed faster in mid-November (74 vs. 69 bites min,1, P < 0·05). The lactating cows lost more live weight (,24 vs. ,12 kg cow,1, P < 0·05) between P1 and P2. A positive correlation was found between consumption of green patches by lactating cows and their daily milk production in P2 (r = 0·574, P = 0·05), whereas no correlation occurred between individual milk production and liveweight loss. Dry cows were less selective, which supports management practices that promote the use of cows with low requirements on extensively grazed pastures in late season. [source]

Studying spatial and temporal dynamics of sward structure at low stocking densities: the use of an extended rising-plate-meter method

GRASS & FORAGE SCIENCE, Issue 4 2003
O. Correll
Abstract An extended rising-plate-meter method was used to study the spatial and temporal variability of the sward structure of extensively managed pastures over a grazing season. Two treatments of a long-term grazing experiment with heifers were investigated: extensive continuous grazing (EG) with a target sward height of 10 cm and intensive continuous grazing (IG) with a target sward height of 5 cm. Compressed sward height and related herbage mass (HM), dominant plant species and stage of development of phenology were determined at weekly or twice weekly intervals at fixed measuring points. The results demonstrated a strong variability in sward height and HM, especially on the EG treatment. The botanical composition of the standing herbage differed between treatments and between patches of different heights within the same treatment. In areas with a short sward, the herbage was predominantly composed of Agrostis capillaris, Festuca rubra and Trifolium repens. It was more evenly composed and also included taller growing species, such as Alopecurus pratensis and Galium mollugo, in areas with a tall sward. The area potentially available for reproductive development was high in the EG treatment and low in the IG treatment. The method employed proved suitable to provide a detailed description of the dynamics of the sward structure. [source]

Extensification of grassland use in the Welsh uplands: sheep performance in years 1,6

GRASS & FORAGE SCIENCE, Issue 2 2001
M. Fothergill
An experiment was established in 1991 on a 25-year-old perennial ryegrass/bent (Lolium perenne L./Agrostiscapillaris L.)-dominated pasture in Wales to study the effects of reducing nutrient inputs to previously fertilized upland pasture. The effects of the removal of applications of (1) N (denoted by CaPK) (2) N, P and K (Ca) and (3) N, P, K, and Ca (Nil) were compared with a treatment which received applications of all four nutrients (CaPKN) over a 6-year period (1991,96) in a randomized block design replicated three times. The experiment was managed under a continuous variable stocking regime (ewes and lambs until weaning and ewes thereafter) maintaining a sward surface height of 4·0 cm throughout the grazing season. Although individual liveweight gain of the lambs was unaffected by the treatments, there was a significant reduction (P < 0·05) in total lamb liveweight gain, ewe stocking rate and length of grazing season as a result of the withdrawal of nutrients. Over the 6 years total lamb liveweight gain was reduced by 17%, 32% and 45% and ewe stocking rate by 21%, 36% and 49% on treatments CaPK, Ca and Nil, respectively, compared with treatment CaPKN. The effect of withdrawing nutrient inputs on ewe stocking rate was progressive and by 1996 the Nil input treatment displayed a 63% reduction compared with the CaPKN treatment and this was also coupled with a 21-day reduction in length of the grazing season. During the post-weaning period, ewes from the Nil input treatment recorded a liveweight loss in 1995 and only a modest liveweight gain in 1996. This coupled with significantly lower body condition scores (P < 0·01) of these ewes in the autumn indicated that the Nil input treatment could lead to reductions in reproductive performance. [source]

The effect of Calluna vulgaris cover on the performance and intake of ewes grazing hill pastures in northern Spain

GRASS & FORAGE SCIENCE, Issue 4 2000
K. Osoro
The effect of the proportion of Calluna vulgaris cover on diet composition, intake and performance of sheep grazing hill vegetation communities in northern Spain is examined. A total of 591 non-lactating Gallega ewes grazed for five consecutive grazing seasons (June to September) on replicated plots of hill pastures (1700 m.a.s.l.) composed principally of Festuca, Agrostis, Nardus and Calluna spp. but with different proportions of Calluna vulgaris cover, either 0·3 (C0·3) or 0·7 (C0·7) of the total area. In 1 year, twenty-eight ewes suckling single lambs also grazed the plots. The mean stocking density over the 5 years was 8·7 ewes ha,1. On treatment C0·3, daily liveweight gains (33 g d,1) of non-lactating ewes were significantly (P < 0·001) greater than on treatment C0·7 (12 g d,1). Likewise in lactating ewes the difference in mean daily liveweight change was 40 g d,1 (,5 vs. ,45 g d,1 for C0·3 and C0·7 treatments respectively; P < 0·001). Liveweight gains of lambs were only 80,100 g d,1 from June to August and lambs only maintained live weight during August and September. The effect of lactational status on liveweight changes was not significant. Liveweight gains of non-lactating ewes increased significantly (P < 0·001) from the first to the last year of the experiment on both treatments. The composition of the diet was significantly affected by treatment (P < 0·001), with a higher proportion of grass species on the C0·3 treatment and a higher digestibility of the diet in the first half of the grazing season (P < 0·001). The proportion of C. vulgaris in the diet was significantly (P < 0·001) higher on the C0·7 treatment and increased significantly (P < 0·001) from July to September on both treatments. There were no significant differences in the composition of the diet selected by lactating and non-lactating ewes. The results demonstrate that on hill vegetation communities, in which the grass components (Festuca rubra, Agrostis capillaris, and Nardus stricta) cover at least 0·3 of the area and on which the preferred grass component (Festuca and Agrostis spp.) is maintained at a sward height of at least 2·5 cm, non-lactating ewes can increase their live weight and body condition, but this increase is influenced by the proportion and quantity of species of grass in the diet, which is affected in turn by the species of grass available and their nutritive quality. However, ewes suckling lambs were not able to maintain their live weight and body condition except when Calluna cover was 0·3 and grass height was more than 3·5 cm. It is concluded that these indigenous vegetation communities can be used in sheep production systems to complement the use of improved pastures at other times of year. In particular, they can be utilized during the non-lactating period (summer) to increase body condition before the beginning of the mating period in autumn. [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]

Analysis of a Japanese Black Cattle-rearing system utilizing a bahiagrass (Paspalum notatum Flügge) pasture: 3.

GRASSLAND SCIENCE, Issue 3 2006
Intake from pasture
Abstract A Japanese Black Cattle-rearing system utilizing a bahiagrass (Paspalum notatum Flügge) pasture in coastal Miyazaki, southern Japan, was analyzed in terms of intake from pasture. In a field approach, herbage intake by grazing cattle was measured for nine periods (1,5 days) during a grazing season (May,October) along with some other variables (e.g. air temperature, herbage mass, digestibility of grazed herbage), under varying levels of supplementary feeding. The intake from the pasture was most closely related to the intake of supplement, showing a negative linear response at a substitution rate of 0.736,0.750. The intake under no supplementation, i.e. a maximum intake from the pasture, was lower than the voluntary intake predicted with feeding standards. In a modeling approach, a semi-mechanistic model for predicting grazing intake was developed using information from the literature as well as the field data. The performance of the model was acceptable. The model showed similar substitution rates (0.64,0.69), and considerable intake restriction (nearly 30%) that is not attributable to limitations by herbage mass, herbage allowance, diet digestibility or air temperature. The results indicate that a low maximal intake by the animals due to low grazing motivation is a major characteristic of the system where supplementation is a usual management practice. [source]

Studies on the immunoglobulin E responses to Teladorsagia circumcincta in sheep: purification of a major high molecular weight allergen

PARASITE IMMUNOLOGY, Issue 5 2001
J.F. Huntley
Studies on the immunoglobulin (Ig)E immune responses to the gastric nematode, Teladorsagia circumcincta, have demonstrated a major high molecular weight allergen (HMWTc). Cross reactive allergens of similar MW were demonstrated for Trichostrongylus colubriformis and Cooperia curticei, but not for Haemonchus contortus. Purification of HMWTc was achieved by gel-filtration chromatography, and nonreducing SDS-PAGE and Western blot analysis revealed two closely associated bands with a molecular weight of approximately 140,150 kDa. Reduction showed four IgE reactive bands of 120, 50, 45 and 30 kDa, and deglycosylation abrogated the immunoreactivity of the 120 and 30 kDa bands. Ultrastructural immunolocalization by electron microscopy revealed that the IgE reactivity was confined to the cuticular surface of the infective (L3) larvae. ELISA studies to determine the IgE anti-HMWTc responses in lambs during their first grazing season, demonstrated significantly higher IgE antibody in lambs with low accumulative faecal egg count (FEC) compared to animals with high accumulative FEC. These studies provide evidence for a protective function of IgE antibody in Teladorsagia infections in lambs. [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]