Post-grazing Herbage Mass Research Articles

Determination of Pasture Dry Matter Intake Rates in Different Seasons and Their Application in Grazing Management

Eight mature horses weighing 576 ± 32 kg (mean ± SD) were used to compare differences in pasture dry matter (DM) intake rate in October (period 1), February (period 2), and May (period 3). Horses were randomly assigned to a pair of adjacent 5 m × 5 m grazing cells containing nontoxic, endophyte-infected tall fescue. Horses had access to each cell for 4 hours. Pasture DM intake rate was estimated over the entire 8-hour period by measuring the pre- and postgrazing herbage mass within each cell and was expressed as kg DM/100 kg body weight (BW)/hr. Mean 8-hour DM intake rate in period 1 (0.17 ± 0.01 kg DM/100 kg BW/hr) was greater ( P < .001) than for period 2 (0.09 ± 0.01 kg DM/100 kg BW/hr) and period 3 (0.11 ± 0.01 kg DM/100 kg BW/hr), but it was not different ( P = .274) between periods 2 and 3. A second experiment using the same eight horses was conducted immediately after the first experiment, within each season, to determine whether the DM intake rates derived from the first experiment could be used along with estimates of maintenance digestible energy (DE) requirements and pasture DE concentrations to predict the amount of grazing time required for a horse to consume only its maintenance DE requirement and maintain zero BW change over a 6-week period. Grazing time necessary to maintain zero BW change was accurately predicted for period 1 only.

Effect of ewe body condition and nutrition in late pregnancy on the performance of triplet-bearing ewes and their progeny

The aim of the present study was to determine the production response of triplet-bearing ewes and their lambs to two differing feeding treatments in mid to late pregnancy and to determine the effect of ewe body condition. Ninety-two days after the start of their breeding period (P92) triplet-bearing ewes, were allocated to either a Medium (n = 72) or ad libitum (‘Adlib’, n = 72) feeding treatment until P113, followed by both groups being merged and offered ad libitum feeding conditions until lambing. The Medium feeding treatment was designed to ensure pre- and postgrazing herbage masses were below 1200 and 1000 kg DM/ha, respectively. Each feeding treatment included ewes from the following body condition score groups: 2.0 or less (CS ≤2.0), 2.5 (CS2.5) or 3.0 or greater (CS ≥3.0). At P113, Medium ewes were lighter (P &lt; 0.05) and had lower (P &lt; 0.05) body condition scores than Adlib ewes (72.4 ± 0.80 vs 75.2 ± 0.85 kg and 2.8 ± 0.06 vs 3.3 ± 0.06, respectively). However, at P141 liveweight no longer differed (P &gt; 0.05, 86.2 ± 0.94 vs 86.6 ± 0.99 kg, respectively), although a small difference in condition score remained (P &lt; 0.05, 3.0 ± 0.07 vs 3.3 ± 0.08, respectively). Ewe feeding treatment had no effect (P &gt; 0.05) on lamb liveweight or survival or ewe liveweight and body condition during lactation. Ewe body condition score group had no effect (P &gt; 0.05) on lamb birthweight. Lambs born to CS2.5 group ewes were heavier 70 days after the midpoint of lambing (L70) than those born to CS ≤2.0 group ewes (20.9 ± 0.41 vs 19.6 ± 0.36 kg, respectively), although they displayed lower survival to L70 (56.0 vs 69.5%). Liveweight at L70 and survival of lambs born to CS ≥3.0 group ewes (20.0 ± 0.39 kg and 61.7%) did not differ (P &gt; 0.05) from those born to either CS ≤2.0 or CS2.5 group ewes. In conclusion, these results suggest triplet-bearing ewes can be maintained under restricted feeding conditions until at least Day 113 of pregnancy without negatively affecting ewe or lamb performance when they are subsequently offered unrestricted feeding for the remainder of pregnancy and during lactation. Under these grazing conditions the body condition of triplet-bearing ewes had little to no effect on their subsequent performance or that of their lambs.

Effect of offering concentrate supplement in late pregnancy, under conditions of unrestricted herbage, on the performance of multiple-bearing ewes and their lambs to weaning

The aim of the present study was to determine if offering ewes a commercial concentrate supplement under conditions of unrestricted perennial ryegrass–white clover herbage availability would increase newborn lamb heat production, colostrum intake and subsequent liveweight. Forty seven twin- and 43 triplet-bearing Romney composite ewes (1/2 Romney, 1/4 Finn, 1/4 Texel) were randomly allocated to either non-concentrate or concentrate treatment groups (twin non-concentrate, n = 24; twin concentrate, n = 23; triplet non-concentrate, n = 22; triplet concentrate, n = 21) from Day 79 of pregnancy. Concentrate-fed ewes were offered an increasing amount of concentrate sheep pellets from Day 79 until Day 90 of pregnancy, at which stage ewes were offered 400 g/day per ewe until they lambed. Pre- and post-grazing herbage masses did not differ (P &gt; 0.05) between non-concentrate (2162 ± 54 and 1704 ± 47 kg DM/ha) and concentrate (2135 ± 49 and 1771 ± 42 kg DM/ha) ewes. Ewe nutritional treatment had no effect (P &gt; 0.05) on ewe liveweight, body condition score, β-hydroxybutyate or non-esterified fatty acid concentrations in late pregnancy. Offering concentrates increased (P &lt; 0.05) the birthweight of triplet-born lambs (4.4 ± 0.1 v. 3.9 ± 0.1 kg for those born to concentrate and non-concentrate ewes, respectively) but had the opposite effect on twins (4.8 ± 0.1 v. 5.2 ± 0.1 kg, respectively). There was no difference (P &gt; 0.05) in maximal heat production, total heat production, rate to reach maximal heat production, and IgG concentrations at 24–36 h of age or liveweight and survival of lambs born to ewes offered concentrates or not. Twin-born lambs had greater (P &lt; 0.05) liveweight and total heat production and had higher (P &lt; 0.05) survival rates than triplet-born lambs. In conclusion, the results of the present study indicate that there are only minor beneficial effects from offering concentrate supplements to ewes in late pregnancy under conditions of unrestricted herbage availability and it is not a viable option for farmers to utilise.

Sward structure and nutritive value of tanzania guineagrass subjected to rotational stocking managements

The objective of this work was to evaluate the sward structure and nutritive value of Panicum maximum Jacq. cv. Tanzânia subjected to rotational stocking managements characterised by a common pre-grazing condition of 95% canopy light interception (LI) and two post-grazing residues, 25 and 50 cm. Treatments (95/25, 95/50 - LI/residue) were assigned to experimental units (groups of six 2500 m² paddocks per treatment) according to a complete randomised block design, with two replications. The variables measured corresponded to: canopy light interception, pre and post-grazing sward height, herbage mass and pre and post-grazing morphological composition, herbage bulk density, herbage accumulation and nutritive value (including to IVOMD) of the morphological components. Pre-grazing herbage mass did not differ between residues, although the herbage accumulation rate was higher for the 50 than the 25 cm (164.9 and 90.6 kg/ha.day DM, respectively). Post-grazing herbage mass values were higher for the 50 cm residue and were characterised by a higher proportion of leaf blade in relation to the 25 cm treatment, which presented a higher proportion of dead material. On average, the contents of crude protein (CP), neutral detergent fibre (NDF) and lignin in acid detergent (LAD) as well as the values of the "in vitro" organic matter digestibility (IVOMD) were similar for both treatments. Crude protein and IVOMD decreased and NDF and LAD increased from top to the bottom of the sward, indicating grazing intensity as an important variable for promoting adjustments in the grazing efficiency and nutritive value of the consumed herbage by the grazing animals.

Annual and seasonal changes in production and composition of grazed clover-grass mixtures in organic farming

A grazed field experiment based on a randomised block design was conducted in Eastern Finland to evaluate the potential of alsike clover (Trifoliun hybridum L.), red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) to support herbage production from clover-grass mixtures under organic farming practices. The effect of seed mixture (alsike clover, red clover, white clover, white and alsike clover or grass mixture), year (1996, 1997 and 1998) and grazing period (5 per grazing season) on pre- and post-grazing herbage mass (HM), botanical and chemical composition of pregrazing HM and post-grazing sward height was assessed. The nutritive value of herbage for milk production was also considered. Seed mixtures resulted in different pre-grazing HM and post-grazing sward heights, but similar pre- minus post-grazing HM. Compared with other mixtures, the proportion of clover was higher for white clover based mixtures. The white clover mixture had the highest crude protein content and lowest concentrations of cellulose and hemicellulose. In addition to seed mixture, the effect of year and grazing period on measured parameters was significant, highlighting the importance of grazing management. Moderate pasture herbage production of relative high nutritive value was achieved under organic practices, but the supply and nutritive value of herbage was variable and, in some cases, unable to meet the requirements of lactating dairy cows. The proportion of clover in all seed mixtures decreased year on year, and was subject to seasonal variations that altered the nutritional value of herbage. White clover was the most suitable perennial clover for pastures in Eastern Finland.;

Comparação de métodos de medida indireta de massa de forragem em pasto de azevém anual (Lolium multiflorum Lam.)

Este trabalho foi realizado de maio a outubro de 2003, na Estação Experimental da Universidade Federal do Rio Grande do Sul (EEA-UFRGS), tendo como objetivo avaliar e comparar a precisão do disco medidor de forragem, do bastão graduado e do medidor de capacitância em predizer a massa de forragem de pastagens de azevém anual. O trabalho constou de dois experimentos: o experimento 1 no qual foram avaliados os três métodos numa situação em que o azevém apresentava-se em fase de estabelecimento num delineamento completamente casualizado, com 32 repetições e três tratamentos; e o experimento 2, no qual foi avaliada a massa de forragem pré e pós-pastejo pelo bastão graduado e pelo disco medidor em potreiros sob lotação rotacionada. O delineamento experimental do experimento 2 foi o de blocos completamente casualizados, com quatro repetições; os tratamentos constaram de duas intensidades de pastejo (baixa e moderada) definidas por ofertas de forragem de 2,5 ou 5,0 vezes o potencial de consumo dos cordeiros que foram utilizados. No experimento 1, o bastão graduado apresentou o melhor coeficiente de determinação com a massa de forragem (r²=0,65). No experimento 2, os melhores coeficientes de determinação foram obtidos quando o pasto, sob lotação rotacionada, foi avaliado com o bastão graduado.

Performance and forage selectivity of sheep and goats co-grazing grass/forb pastures at three stocking rates

Differences among ruminant species in forage selectivity offer potential for efficient utilization of pastures with diverse arrays of plant species. One common management strategy that may influence forage selectivity is stocking rate (SR). Therefore, this experiment was conducted to determine effects of SR on performance and forage selectivity of growing sheep and goat wethers co-grazing grass/forb pastures. Grazing was for 16 weeks in 2002 and 2003. Pastures consisted of various grasses, primarily bermudagrass ( Cynodon dactylon) and johnsongrass ( Sorghum halepense), and forbs (e.g., ragweed; Ambrosia spp.). Sheep (Khatadin) and goats (75% Boer) averaged 21 ± 0.7 and 21 ± 0.5 kg initial BW, respectively, and were 4–5 months of age when grazing began. Stocking rates were four (SR4), six (SR6), and eight (SR8) animals per 0.4-ha pasture, with equal numbers of sheep and goats. The nine pastures (three/treatment) were divided into four paddocks for rotational grazing in 2-week periods. Forage mass (pre- and post-grazed) and composition of grass versus forbs were determined by quadrat samples and transect analysis, respectively. BW was measured every 4 weeks and preference values for grass, forbs, and ragweed (10: highest possible preference; 0: consumption in proportion to availability; −10: no consumption) were determined from fecal microhistology and transect measures. There was a year × SR interaction ( P < 0.05) in herbage DM mass before grazing (year 1: 2937, 3298, and 3351 kg/ha; year 2: 3033, 2928, and 2752 kg/ha for SR4, SR6, and SR8, respectively (S.E. = 174.4)). Post-grazed forage mass decreased linearly ( P < 0.05) as SR increased (2279, 1693, and 1288 kg/ha for SR4, SR6, and SR8, respectively (S.E. = 102.6)). In vitro true DM digestibility of pre-grazed forage samples was similar among SR, but SR × year interacted ( P < 0.05) for post-grazed samples (year 1: 57.0, 54.4, and 53.5; year 2: 56.8, 49.0, and 48.3 for SR4, SR6, and SR8, respectively (S.E. = 2.16). Year and SR interacted ( P < 0.05) in the percentage of grass in pastures post-grazing determined by transect (year 1: 64, 69, and 74%; year 2: 50, 66, and 73% for SR4, SR6, and SR8, respectively (S.E. = 8.4)). The preference for grasses was higher and that for total forbs lower for sheep than for goats ( P < 0.05). The preference value for ragweed, measured in year 2, was lower ( P < 0.05) for sheep than for goats (−1.6 versus 0.2) and increased linearly with increasing SR. Average daily gain tended ( P < 0.10) to decrease linearly as SR increased (61, 51, and 47 g/day), and total BW gain per hectare increased linearly ( P < 0.05; 610, 759, and 933 g/day for SR4, SR6, and SR8, respectively). In conclusion, post-grazing herbage mass >1000 kg/ha at most measurement times suggests that decreasing forage availability with increasing SR may not have been primarily or solely responsible for the effect on ADG by limiting DM intake. Rather, the effect of SR on available forage mass could have limited the ability of both sheep and goats to compensate for the effect of SR on forage nutritive value.

Pasture and Stocker Cattle Performance on Furrow-Irrigated Alfalfa and Tall Wheatgrass Pastures, Southern High Plains, USA

Alfalfa (Medicago sativa L.) and tall wheatgrass [Agropyron elongatum (Host) Beauv., = Elytrigia elongata (Host) Nevski] monocultures and mixtures were rotationally and continuously grazed by beef stockers (Bos taurus L.) in the 1999 to 2001 growing seasons. Pastures sown with 5.1 kg pure live seed (PLS) ha -1 alfalfa and 13.5 kg PLS ha -1 tall wheatgrass produced regrowth containing approximately 60% alfalfa, while postgrazing herbage mass was approximately 50% alfalfa. No differences (P < 0.05) were significant for season mean (means of six measurement dates) regrowth or postgrazing herbage mass. There also was no date × pasture treatment interaction for postgrazing herbage mass, indicating the pastures were treated equally with regard to grazing pressure. Interactions involving year, date, and pasture type had no effect on cumulative animal gain ha -1 [kg live weight (LW) ha -1 yr -1 ]. Pastures containing alfalfa gave a twofold increase in gain ha -1 over monoculture tall wheatgrass (962 vs. 464 kg LW ha -1 yr -1 for pastures containing alfalfa and monoculture tall wheatgrass, respectively), caused by differences in stocking rate (6.42 vs. 3.55 animals ha -1 for pastures containing alfalfa and monoculture tall wheatgrass, respectively) and average daily gain (ADG) (0.94 vs. 0.82 kg LW animal -1 d -1 for pastures containing alfalfa and monoculture tall wheatgrass, respectively). Bloat was not observed in cattle grazing continuously stocked alfalfa-tall wheatgrass pastures, but it was in rotationally stocked pastures that included alfalfa every year. Producers in the Southern High Plains may improve animal gain ha -1 by including alfalfa in tall wheatgrass pastures and possibly reduce the incidence of bloat by continuous stocking.

Seasonality of calving in pasture-based dairy systems: its effects on herbage production, utilisation and dry matter intake

The objectives of the present work were to evaluate the influence of season of calving on (i) pasture productivity, (ii) total dry matter intake by cows, and (iii) the relationship between intake and milk yield of individual cows. Three systems in which the cows calved either in autumn, in spring or half in autumn, half in spring, were managed according to a set of common guidelines during 3 consecutive years. Herbage accumulation rate (HAR) was estimated by the difference between 2 successive grazings (pre- and post-grazing herbage mass). Average HAR in each month was similar between systems. However, small differences in HAR were observed between calving systems in spring and summer, and appeared to be related to the proportion of the farmlet closed for silage. Herbage dry matter intakes varied seasonally (P&lt;0.05), but independently of the calving system (P&gt;0.05). Cows from different calving systems, offered 8.9 or 2.5 kg maize silage dry matter per cow daily in the paddocks, consumed an average of 6.0 and 1.4 kg, respectively. A large variation in intake was observed between individual cows with ranges from 2 to 10 kg and 0.2 to 2.9 kg, respectively. In conclusion, applying the same grazing management decisions to systems with contrasting calving dates resulted in only small seasonal, but not annual, differences in pasture HAR. The results also indicated that when maize silage is fed in the paddock, wastage can be high and variation in intake between individual cows can also be large.

SGS Animal Production Theme: effect of grazing system on animal productivity and sustainability across southern Australia

The effects of various grazing management systems on sown, naturalised, and native pastures were studied at 6 different locations in the temperate high rainfall zone (HRZ, &gt;600 mm rainfall/year) of southern Australia, as part of the Sustainable Grazing Systems (SGS) Program. The treatments examined had different pasture species and fertiliser management, with grazing method ranging from set stocking (continuous grazing) to rotation with rests based on pre- and post-grazing herbage mass or season and plant phenology. Sites were located at: Albany, Western Australia; Manilla, Barraba, Nundle, New South Wales; (grazed by wethers); and Carcoar, New South Wales; Maindample, Ruffy, north-east Victoria; Vasey, western Victoria; (grazed by ewes and lambs).Grazing method significantly (P&lt;0.001) influenced stocking rate (expressed as dry sheep equivalents (DSE)/ha), but effects were not consistent across sites. At Vasey the stocking rate of the rotation treatments ranged from 5 to 23% higher than the set stocked treatments depending upon year. For all sites, significant factors (P&lt;0.001) affecting stocking rate were soil Olsen P, soil pH, grazing management (resting), legume percent, and an index of growing season effectiveness. Although total annual rainfall had a significant effect (P&lt;0.002) in an initial analysis, its influence became non-significant (P&gt;0.05), when a growing season index (P&lt;0.001) was used. Non-significant (P&gt;0.05) factors included solar radiation, annual average temperature, fertiliser applied in the current year, and average annual perennial and broadleaf percent composition. The implications of these data for productivity and sustainability (as assessed by perenniality and water use) were encouraging. Generally, there were positive relationships between increased stocking rate and the probability of achieving a zero mm soil water surplus in winter, and between increased productivity and the proportion of perennial grass species where extremes of treatments were compared at each site. The results indicate that stocking rate can be increased without jeopardising sustainability, that grazing management can bring about more sustainable pastures, that there is scope to increase productivity particularly through increasing soil fertility, and growing season length can be used to predict potential carrying capacity. These are positive outcomes that graziers in the HRZ of southern Australia can use to enhance productivity (thus profitability) and sustainability.

Efficiency of pasture and supplement management in high producing dairy herds

In 1998 a three-year dairy farm monitoring programme funded by AGMARDT (Agricultural Marketing and Research Development Trust) was established on twelve dairy farms in the southern North Island of New Zealand where policy had changed from a focus on high production per ha through high stocking rate to a management based on reduced stocking rate and strategic use of supplements to enhance both production per cow and per ha. The project involved a detailed three-year data collection which included measurements of the quantity and composition of pasture and supplements consumed as well as animal performance. Analysis of the results of the third year (2000/2001) on nine of these farms with complete data sets identified a range of metabolisable energy (ME) intake (50669 - 70135 MJ ME/cow/yr). Supplementary feed represented on average 24% (21 - 27 %) of the total intake of ME, the main supplements being pasture silage (summer to winter), turnips (summer) and maize silage (autumn and winter) consumed by lactating cows, and grazing off by dry stock. There was a range of milksolids (MS) production per cow (372 - 424 kg/year) and per hectare (921 - 1264 kg/year). The average economic farm surplus per hectare of NZ$3077 (NZ$2425 - NZ$3867) for the case-study farms was approximately 43% higher than the top 25% farms in the Manawatu region. Mean values of return on assets for the case-study farms (12.9%) and top 25% farms in Manawatu (13.0%) were similar. Good pasture management based on controlled preand post-grazing herbage mass targets (mean 2650 and 1900 kg DM/ha, respectively), strategic use of supplementary feed to control pasture deficits, and moderate stocking rates (overall mean 2.7 cows/ha), provided high allowances of high quality herbage (organic matter digestibility ranging from 742 to 845 g/kg DM) and maintained high levels of milk production (411 kg MS/cow and 1100kg MS/ha). The comparison with industry data showed that the casestudy farms were highly productive and profitable dairy systems, at least under the conditions of the 2000/2001 season. However, the result indicated the need to improve management skills to limit feed wastage under generous feeding management, and also the limitation of conventional procedures for monitoring pasture consumption in farming systems. Keywords: animal performance, dairy systems, energy intak e, herbage quality, pasture management, profitability

Development and evaluation of a standardised means for estimating herbage mass of dairy pastures using the rising plate meter.

Calibration data for the rising plate meter (RPM) collected from four locations and spanning a period of 10 years (1988-1998) were used to develop a pooled standard set of RPM calibrations to be used to estimate herbage mass of dairy pastures across a number of dairying regions. When evaluated in a farmlet study run over a 2-year period, the standard RPM calibration gave similar estimates of average farm cover, pre and postgrazing herbage mass and consumed DM, as herbage mass estimates calculated from RPM measurements calibrated to the local pasture on each assessment day. Compared with visual estimations, the standard RPM calibration underestimated pre-grazing herbage mass, average farm cover and the amount of pasture consumed, and overestimated post-grazing herbage mass. Reasons for these differences are discussed and an alternative approach to using the RPM for on-farm pasture assessment is presented. Standardised, onfarm herbage mass estimates may be possible using the RPM and standard calibrations to calibrate visual estimations prior to visually assessing pasture across the whole farm. Such a standardised pasture assessment method would assist the grazing management of dairy pastures across a number of New Zealand dairying districts. Keywords: average farm cover, dairy-grazing management, pasture growth, post-grazing herbage mass, pre-grazing herbage mass, rising plate meter

Quantifying Spatial Heterogeneity in Herbage Mass and Consumption in Pastures

A sward-based technique for quantifying the spatial heterogeneity in herbage mass and consumption was developed and tested in a bahia grass (Paspalum notatum Flugge) pasture grazed by cattle. For five, 2-day grazing periods from May to October, preand post-grazing herbage masses were nondestructively estimated with an electronic capacitance probe at 182, 50 x 50 cm locations along 2 permanent line transects. At the same time, undisturbed herbage accumulation during grazing was measured inside exclosures and the results used to estimate accumulation under grazing at each location. Estimation of herbage mass was relatively good; R2= 0.88 to 0.98. Spatial heterogeneity in herbage mass and the stability of the spatial pattern were well quantified. The pattern of spatial heterogeneity observed early in the grazing season remained quite stable for 5 months until the late grazing season. Spatial heterogeneity in the rate of defoliation was also well quantified in spite of some negative values. The technique is of potential value for quantifying the spatial heterogeneity in herbage mass and consumption by animals in grazed pastures, though further studies are necessary for testing the applicability of the technique to pastures of other plant species or of multiple species.

Quantifying spatial heterogeneity in herbage mass and consumption in pastures

A sward-based technique for quantifying the spatial heterogeneity in herbage mass and consumption was developed and tested in a bahia grass (Paspalum notatum Flügge) pasture grazed by cattle. For five, 2-day grazing periods from May to October, pre- and post-grazing herbage masses were nondestructively estimated with an electronic capacitance probe at 182, 50x50 cm locations along 2 permanent line transects. At the same time, undisturbed herbage accumulation during grazing was measured inside exclosures and the results used to estimate accumulation under grazing at each location. Estimation of herbage mass was relatively good; R2= 0.88 to 0.98. Spatial heterogeneity in herbage mass and the stability of the spatial pattern were well quantified. The pattern of spatial heterogeneity observed early in the grazing season remained quite stable for 5 months until the late grazing season. Spatial heterogeneity in the rate of defoliation was also well quantified in spite of some negative values. The technique is of potential value for quantifying the spatial hetero-geneity in herbage mass and consumption by animals in grazed pastures, though further studies are necessary for testing the applicability of the technique to pastures of other plant species or of multiple species.

Optimizing rotational grazing in sheep management systems

Rotational grazing on sheep farms was modeled using an iconic simulation modeling package. An event-driven modeling approach allowed the simulation of individual paddocks on a farm and their grazing. It permitted the effects of different levels of herbage allowance to be tested and measured with respect to pre- and post-grazing herbage mass, rotation length, diet quality, animal performance, and the enterprise gross margin. Validation of the model against three experimental data sets indicated a good fit. A genetic algorithm was implemented to enable the optimum sequence of control and state variables to be determined for the grazing system. This was used to calculate the optimum stocking rate and monthly sequence of herbage allowance, nitrogen application, winter supplementation, and lamb drafting weight for 12 months on a theoretical farmlet. The farmlet was stocked with 17.5 sheep (ewes)/ha at an initial liveweight of 55 kg, a starting pasture dry matter cover of 1500 kg/ha, and 130% lambing. Pasture allowances suggested by the optimization were consistent with the recommendations provided to sheep farmers, while nitrogen applications were higher than expected, reflecting the prevailing high lamb prices compared to the cost of nitrogen boosted pasture.

Estimation of dairy pastures - the need for standardisation

A study was undertaken to determine the reason for the differences in the estimation of pasture mass between dairying research centres in New Zealand and to define a common system of estimation that would overcome these differences and be able to describe the pasture situation on commercial dairy farms in different parts of New Zealand. Differences in the visual estimation of pasture between a standard observer and a local observer at the different dairying research centres in the order of 900 kg DM/ha were identified. This was attributed to a lack of regular visual calibration of persons who regularly assessed pasture, as differences between centres in the actual harvested DM yields of the visually assessed plots varied less (200-400 kg DM/ha). To achieve uniformity it is recommended that all centres measure total herbage mass (the amount of herbage above ground level) to regularly calibrate pasture assessment in dairy grazing management studies and on dairy farms. A reasonably consistent estimation of average farm cover, the ranking of paddocks (r2 &gt; 0.9) for the purposes of determining grazing order and the estimation of pre- and post-grazing herbage mass was achieved using the rising plate meter and L'Huillier &amp; Thomson's standard set of calibration equations published in 1988. With these recommendations, estimation of pasture will be more uniform. Standard calibration of the plate meter for the determination of rate of DM disappearance (pre-post grazing) achieved less consistency. Keywords: herbage mass, pasture assessment, pasture height, rising plate meter, visual pasture estimation

Forage Production and Grazing Management of Chicory

'Grasslands Puna' chicory (Cichorium intybus L.) is a perennial cool-season herb developed as a forage in New Zealand. The objective of this study was to evaluate forage production potential and rotational grazing strategies for chicory grown in central Oklahoma. Pastures were established on two soil types and grazed for 2 yr with 3 rotational strategies described as fast (13 d rest periods), moderate (27 d rest periods), and slow (38 d rest periods). Chicory plant density during the seeding year was higher on a silt loam (4.5 plants/sq ft) than on a silty clay loam soil (2.2 plants/sq ft; P < 0.05). By the second year, however, natural reseeding resulted in equally dense stands on both soil types (4.3 plants/sq ft). Moderate and slow rotational grazing resulted in significantly greater (P < 0.05) amounts of harvested forage (7050 Iblacre) compared with the fast rotational treatment (5890 Iblacre). Fewer chicory plants bolted under the fast rotation; however, it is likely that this treatment did not allow adequate time for substantial leaf area accumulation and regrowth. Crude protein (CP) content of chicory averaged 18.3% and in vitro dry matter digestibility (IVDMD) averaged 70.9%. Chicory appears to have potential as a productive and high quality cool-season forage crop in Oklahoma.

Effect of condensed tannins inLotus corniculatusupon lactation performance in ewes

SUMMARYA grazing experiment was conducted for 8 weeks in the spring/summer of 1993 at Palmerston North, New Zealand, to study the effects of condensed tannins (CT) inLotus corniculatus(birdsfoot trefoil cv. Grasslands Goldie) upon the lactation performance of ewes rearing twin lambs. Effects of CT were evaluated by studying the responses of ewes to twice daily oral supplementation with polyethylene glycol (PEG; MW 3500), which binds and inactivates CT. A rotational grazing system with restricted feed allowance was used. Measurements were made of pre- and post-grazing herbage mass, the composition of the feed on offer and diet selected, voluntary feed intake (VF1), milk yield and composition, liveweight gain and wool production. The concentration of metabolites in rumen fluid and in blood plasma was also measured. Lotus contained 35–5 g total nitrogen and 44–5 g total CT/kg dry matter in the diet selected, with anin vitrodigestibility of 73%. At peak lactation (weeks 3 and 4) milk yield and composition were similar for control (CT-acting) and PEG-supplemented (CTinactivated) ewes but, as lactation progressed, the decline in milk production and in the secretion rates of protein and lactose were less for control than for PEG-supplemented ewes. In mid and late lactation (weeks 6–11), control ewes secreted more milk (21 %), more milk protein (14%) and more lactose (12%) than PEG-supplemented ewes. Milk fat percentage was lower for control than for PEG-supplemented ewes, but secretion rates of fat were similar for the two groups. VFI, liveweight gain and wool growth were similar for both groups. Plasma urea and glucose concentrations were lower for control than for PEG-supplemented ewes, but concentrations of non-esterified fatty acids (NEFA), growth hormone and insulin were similar for the two groups. The concentrations of ammonia and molar proportions ofiso-butyric,iso-andn-valeric acids in rumen fluid were lower for control than for PEG-supplemented ewes; molar proportions of acetic, propionic and H-butyric acids were similar for the two groups. It was concluded that for ewes rearing twin lambs grazingL. corniculatus, the action of CT increased milk yield and the secretion rates of protein and lactose without affecting VFI, thereby increasing the efficiency of milk production. The increased milk production did not appear to be mediated by effects on plasma concentrations of growth hormone or insulin.

Effect of condensed tannins upon the performance of lambs grazing Lotus corniculatus and lucerne (Medicago sativa)

SUMMARYA grazing experiment, conducted for 22 weeks in 1992/93 at Aorangi Research Station, AgResearch Grasslands, Manawatu, New Zealand, compared the productivity of weaned lambs grazing Lotus corniculatus (birdsfoot trefoil) and lucerne (Medicago sativa). Effects of condensed tannins (CT) in lotus were evaluated by studying the responses of lambs to twice daily oral supplementation with polyethylene glycol (PEG). A rotational grazing system with restricted feed allowance was used. Measurements were made of pre- and post-grazing herbage mass, the composition of the feed on offer and diet selected, voluntary feed intake (VFI), liveweight gain (LWG), carcass growth, wool growth and the concentration of metabolites in rumen fluid. For both lotus and lucerne swards, the diet selected was mainly leaf. Lotus contained 34 g total CT/kg dry matter in the diet selected, whilst there were essentially no CT in lucerne. Compared to lambs grazing lucerne, lambs grazing lotus had slightly lower VFI, and higher LWG, carcass weight gain, carcass dressing-out percentage and wool growth. PEG supplementation had no effect on these measurements or upon the composition of rumen fluid in lambs grazing lucerne. However, in lambs grazing lotus, PEG supplementation reduced wool growth (10·9 ν. 12·1 g/day), slightly reduced LWG (188 ν. 203 g/day), increased rumen ammonia concentration, and increased the molar proportions of /.so-butyric, isovaleric and n-valeric acids and protozoa numbers in rumen fluid. PEG supplementation did not affect carcass gain, carcass fatness or the molar proportion of rumen acetic, propionic or n-butyric acids in lambs grazing lotus. It was concluded that the principal effect of CT in growing lambs grazing lotus was to increase wool growth without affecting VFI, thereby increasing the efficiency of wool production, that the greater rate of carcass gain of lambs grazing lotus than those grazing lucerne was mainly caused by factors other than CT and that CT did not affect the rumen fermentation of carbohydrate to major volatile fatty acids.

A comparison of quadrat, capacitance meter, HFRO sward stick, and rising plate for estimating herbage mass in a smooth‐stalked, meadowgrass‐dominant white clover sward

AbstractA single‐probe capacitance meter (Pasture Probe), the Hill Farm Research Organization (HFRO) sward stick, a rising‐plate meter, and cut quadrats were used to estimate herbage mass of swards that were rotationally grazed by cattle, cattle followed by topping, cattle followed by sheep, or sheep alone during 1989 and 1990 grazing seasons. Mean target pre‐ and post‐grazing herbage masses were 2200 and 1100 kg dry matter (DM) ha−1 respectively. Linear regressions, correlations and scatterplots were calculated relating meter and sward stick readings to herbage mass on an ash‐free organic matter basis measured by cutting quadrats of herbage at ground level.Mean coefficients of variation for quadrat, capacitance meter, sward stick and rising plate were 28·8, 15·5, 27·2 and 27·9% respectively for pre‐grazing herbage mass measurements, and 20·2, 10·1, 21·4, and 18·4% respectively for post‐grazing measurements. These coefficients indicate that the capacitance meter varied less in estimating pre‐ and postgrazing herbage mass than the other three methods.Correlation coefficients relating cut quadrats to capacitance meter, sward stick and rising plate readings were 0·65, 0·70 and 0·72 for pre‐grazing, and 0·36, 0·31 and 0·05 for post‐grazing herbage mass measurements respectively.The non‐destructive methods provided quick herbage mass estimates at a level of precision adequate for making day‐to‐day grazing management decisions on farms.