Effects of shrub encroachment on herbage production and nutritive value in semi-arid Mediterranean grasslands

There is limited information on the effects of the increase in the density of shrubs on herbage production and nutritive value of natural grasslands in the Mediterranean region, currently facing major land use changes. Herbage production of drymatter (herbaceous fractions, of plant functional groups and by species), crude protein (CP), neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF), acid‐detergent lignin (ADL) and hemicellulose concentrations and in vitro organic matter digestibility were determined at the time of peak of annual growth across four types of grassland vegetation each characterized by different shrub cover regimes. A sharp reduction in herbage production and a reduction in nutritive value were found as a result of the increase in shrub cover. These changes appeared to be closely related to the shift in plant functional groups detected as shrub density increased. Herbage production from grasses and legumes was found to be more sensitive to shrub cover changes than herbage production from forbs, whereas, as grassland types became denser, annual species were gradually replaced by perennials and C₄ grasses by C₃ ones. The impact of shrub encroachment on Mediterranean grasslands is discussed in relation to their use by livestock.     

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

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.     

Responses of herbage P,Ca, K and Mg content and Ca/P and K/(Ca + Mg) ratios to long‐term continuous and discontinued cattle grazing on a rough fescue grassland

Herbage minerals affect performance of grazing cattle. We investigated the response of herbage P, K, Ca and Mg contents and Ca/P and K/(Ca + Mg) ratios to long‐term stocking rate, continuous vs. discontinued grazing practice, and sampling year. Cattle had been stocked at 2·4 and 4·8 animal unit months ha^?1 since 1949. Exclosures were installed in April 1998. Herbage samples were collected near peak herbage mass in 2001, 2003, 2008 and 2012 and analysed for mineral content. Mineral contents were similar between the two stocking rates, but were lower (P < 0·05) under discontinued than continuous stocking, with the exception of similar P contents. The content of P and K in herbage was higher and the content of Ca and Mg was lower (P < 0·05) in years with greater precipitation and lower temperatures. Herbage mineral content, with the exception of P, exceeded minimum recommended levels for cattle. Given the low P content in herbage (0·74–1·19 g kg^?1) and high Ca/P ratios during the dry and hot year (of 2001), a dietary P supplement should be considered for cattle grazing rough fescue grassland in drought years. The low K/(Ca + Mg) ratios (<2·2) suggest there is little risk of grass tetany in cattle grazing on this grassland.     

Does post‐grazing sward height influence sward characteristics,seasonal herbage dry‐matter production and herbage quality?

Extending the grazing season through the production and utilization of high‐quality forage is a key objective in grassland‐based dairy production systems. Grazing swards to a low post‐grazing sward height (PGSH) is a strategy for improving grass utilization. A grazing experiment conducted in Ireland investigated immediate and subsequent effects of PGSH on sward production, utilization and structural characteristics. Swards were grazed to 2·7 cm (severe; S1) or 3·5 cm (moderate; M1) from 10 February to 18 April 2010 (Period 1; P1). From 19 April, each P1 paddock was halved and grazed to either 3·8 cm (S2) or 4·8 cm (M2), until 30 October (Period 2; P2). The first grazing rotation was +7 d on S1 swards compared with M1 swards (45 d), due to greater herbage utilization (+0·22). Herbage production during P1 was not affected by PGSH but a severe PGSH during this period reduced subsequent herbage production: 13·9 (S1) vs. 15·5 t dry matter (DM) ha^?1 (M1) by the end of the study. Leaf proportion was increased (+0·10) on S2 swards compared with M2 swards, but M2 swards produced 1·2 t DM ha^?1 more herbage during P2. Despite the relatively lower level of sward utilization obtained from moderate grazing in P1 (3·5 cm) and P2 (4·5–5·0 cm), such levels of PGSH increased DM production while maintaining sward quality, compared with severe grazing (2·7 cm in P1 and 3·5–4·0 cm in P2).     

A simple statistical model for predicting herbage production from permanent grassland

The considerable year‐to‐year and seasonal variation in grassland production is of major importance to dairy farmers in Europe, as production systems must allow for the risk of unfavourable weather conditions. A large portion of the variability is caused by weather and its interaction with soil conditions and grassland management. The present study takes advantage of the interactions between weather, soil conditions and grassland management to derive a reliable grassland statistical model (GRAM) for grasslands under various management regimes using polynomial regressions (GRAM‐R) and neural networks (GRAM‐N). The model performance was tested with a focus on predicting its capability during unusually dry or wet years using long‐term experimental data from Austrian sites. The GRAM model was then coupled with the Met&Roll stochastic weather generator to provide estimates of harvestable herbage dry matter (DM) production early in the season. It was found that, with the GRAM‐N or GRAM‐R methodology, up to 0·78 of the variability in harvested herbage DM production could be explained with a systematic bias of 1·1–2·3%. The models showed stable performance over subsets of dry and wet years. Generalized GRAM models were also successfully used to estimate daily herbage growth during the season, explaining between 0·63 and 0·91 of variability in individual cases. It was possible to issue a probabilistic forecast of the harvestable herbage DM production early in the season with reasonable accuracy. The overall results showed that the GRAM model could be used instead of (or in parallel with) more sophisticated grassland models in areas or sites where complete data sets are not yet available. As the model was tested under various climatic and soil conditions, it is suggested that the proposed approach could be used for comparable temperate grassland sites throughout Europe.     

Grazing preference of Merino sheep for naturalized annual clover species relative to commonly sown clover species

Selective grazing of white clover (Trifolium repens) over grass species in temperate pastures results in reduced clover abundance and availability over time. Within sheep‐ and cattle‐grazed dryland (<800 mm annual rainfall) hill and high country areas of New Zealand, naturalized unsown annual clover species show greater persistence and abundance over sown clovers. With a view to understanding legume abundance in these areas, Merino sheep grazing preference was investigated for pure swards of naturalized species Trifolium dubium, T. glomeratum, T. arvense and T. striatum and commonly sown species T. repens and T. subterraneum. The Chesson–Manly preference index was used to explore the hypothesis that grazing preference differs between these species and changes as plants mature. Herbage offtake was quantified at vegetative (mid–late spring; November) and reproductive (early summer; December) stages of plant maturity. Significant preference distinctions between species (P < 0·05) occurred in December, with relative preference ranging from 0·248 for T. repens to 0·065 for T. dubium. Reduced relative preference for naturalized species was related to decreasing nutritive value from spring to summer, reflecting increased stem and flower sward content. Relative preference was negatively related to increasing acid detergent fibre and neutral detergent fibre and positively related to greater crude protein and dry‐matter digestibility. Naturalized annual clover species of lower grazing preference at reproductive maturity will benefit pasture sustainability via herbage and seed production and associated nitrogen‐fixation inputs.     

Evaluating seasonal variation in mineral concentration of cool‐season pasture herbage

Pasture herbage is a major source of minerals for livestock in pasture‐based production systems. Herbage mineral concentrations vary throughout the growing season, whereas mineral supplementation to livestock is often constant. The study objectives were to analyse the seasonal variation in herbage mineral concentrations in tall fescue [Schedonorus phoenix (Scop.) Holub]‐based pasture with regard to beef cattle mineral requirements and to create a statistical model to predict variation in herbage mineral concentrations across the growing season. Pasture herbage was analysed from 12 grazing systems in Virginia to determine its mineral concentration from April to October of 2008–2012. The pasture herbage, grown without fertilization, contained adequate macronutrient concentrations to meet the requirements of dry beef cows through the growing season and the requirements of lactating beef cows in April. Phosphorus supplementation appeared to be unnecessary for dry beef cows given adequate concentrations in pasture herbage. A model using month of harvest, soil moisture and relative humidity explained 75% of the variation in an aggregated mineral factor. The 90% prediction intervals indicated that N, P, K, S and Cu concentrations could be predicted within 1·35, 0·08, 0·80 and 0·07% and 3·83 mg kg^?1 respectively. Prediction of herbage mineral concentrations could help to improve livestock health, reduce costs to producers and limit nutrient losses to the environment.     

The effects of autumn closing date on sward leaf area index and herbage mass during the winter period

The provision of grass for early spring grazing in Ireland is critical for spring calving grass‐based milk production systems. This experiment investigated the effect of a range of autumn closing dates (CD), on herbage mass (kg DM ha^?1), leaf area index (LAI) and tiller density (m^?2) during winter and early spring. Thirty‐six grazing paddocks, closed from 23 September to 1 December 2007, were grouped to create five mean CD treatments – 29 September, 13 October, 27 October, 10 November, 24 November. Herbage mass, tiller density and LAI were measured every 3 weeks from 28 November 2007 to 20 February 2008; additionally, herbage mass was measured prior to initial spring grazing and tiller density was measured intermittently until September 2008. Delaying CD until November significantly (P < 0·05) reduced herbage mass (by approximately 500 kg DM ha^?1) and LAI (by approximately 0·86 units) in mid‐February. On average, 35% of herbage mass present on swards on 20 February was grown between 28 November and 30 January. LAI was positively correlated with herbage mass (R² = 0·78). Herbage mass increased by approximately 1000 kg DM ha^?1 as spring grazing was delayed from February to April. Tiller density increased from November to February, although it did fluctuate, and it was greatest in April (9930 m^?2). This experiment concludes that in the south of Ireland adequate herbage mass for grazing in early spring can be achieved by delaying closing to early mid‐October; swards required for grazing after mid‐March can be closed during November.     

Growth and chemical composition of wild oat (Avena fatua) under Mediterranean conditions

Wild oat (Avena fatua) is an annual cool‐season species that grows in areas with a Mediterranean climate and has potential as a forage source in Jordan. A field experiment was conducted during the growing seasons of 1999–2000 and 2000–2001 under sub‐humid Mediterranean conditions at Samta in the Ajloun Mountains, Jordan. Data on seasonal herbage mass, morphology and chemical composition of wild oat were collected at 60, 80, 100, 120 and 140 days after emergence. Plant height increased rapidly beyond 100 days after emergence. The increase in herbage mass of dry matter was gradual and peaked at 140 days after emergence. The lowest concentration of crude fibre was at 60 and 80 days after emergence, with a range of 201–263 g kg^?1 DM. Crude fibre concentrations (610–630 g kg^?1 DM) peaked at 140 days after emergence (maturity). In contrast to concentrations of crude fibre, concentrations of crude protein decreased gradually with age. The calcium and phosphorus concentrations were sufficient to meet the maintenance requirements of ewes.     

Herbage intake and milk production by grazing dairy cows 1. The effects of variation in herbage mass and daily herbage allowance in a short-term trial

Twenty-four British Friesian cows were allocated between six grazing treatments (two levels of herbage mass x three levels of daily herbage allowance) in a balanced change-over design with four periods of 12 d each at monthly intervals. Herbage OM mass ranged from 3790 to 5770 kg ha^-1 measured to ground level and daily herbage DM allowances were 30, 60 and 90 g per kg animal live weight. Herbage OM intake was lower at high than at low herbage mass (24·6 vs 26·3 g per kg LW), and was 26·9, 26·6 and 22·9 g per kg LW respectively at daily herbage DM allowances of 90, 60 and 30 g per kg LW. Milk yield was not affected by herbage mass but was depressed at the low herbage allowance.     

Fibre digestion potential in sugarcane across the harvesting window

The objectives of this study were to determine the proportion of indigestible neutral detergent fibre (iNDF) in the neutral detergent fibre (NDF) fraction of sugarcane, to estimate changes in NDF digestibility (NDFD) during the harvesting window and to predict sugarcane digestibility based on its fibre fractions. Whole plants of the IAC86‐2480 and IAC93‐3046 varieties were collected during the harvesting windows in 2007 and 2009, respectively. The in vitro true dry matter digestibility (IVTDMD) and fibre contents (NDF, iNDF, acid detergent fibre) were determined by near infrared reflectance spectroscopy (NIRS). The NDFD and potentially digestible NDF digestibility (pdNDFD) were estimated, and the fractional digestion rate of pdNDF was calculated. There was no relationship between growing days and iNDF as a proportion of NDF (P = 0·28) or with the fractional digestion rate of pdNDF (P = 0·30). Therefore, NDFD (mean = 335 g kg^?1) and pdNDFD (mean = 657 g kg^?1) remained almost constant during the harvesting window (P = 0·70 and P = 0·32 respectively). Acid detergent fibre and NDF were the best predictors of sugarcane dry matter (DM) digestibility. In conclusion, NDFD seems to be unchanged during crop growth. The point at which to harvest sugarcane as a forage source should therefore be decided based on NDF concentration, which is greatly influenced by sucrose accumulation.     

Effects of perennial ryegrass (Lolium perenne L.) cultivars on herbage production, nutritional quality and herbage intake of grazing dairy cows

Four perennial ryegrass (Lolium perenne L.) cultivars were compared for differences in herbage production, nutritive value and herbage intake of dry matter (DM) during the summers of 2002 and 2003. Two paddocks were sown with pure stands of four cultivars in a randomized block design with three replicates. Each plot was subdivided into fourteen subplots (22 m × 6 m) which were grazed by one cow during 24 h. Twelve lactating dairy cows were assigned to one cultivar for a period of 2 weeks in a 4 × 4 Latin square experimental design; the experiment lasted 8 weeks in each year. Sward structure (sward surface height, DM yield, green leaf mass, bulk density and tiller density) and morphological characteristics were measured. The ash, neutral‐detergent fibre, acid‐detergent lignin, crude protein and water‐soluble carbohydrate concentrations, and in vitro digestibility of the herbage were measured. The sward was also examined for infestation by crown rust (Puccinia coronata f. sp. lolii). Herbage intake of dairy cows was estimated using the n‐alkane technique. Cultivar differences for all sward structural characteristics were found except for bulk density and tiller density in 2003. Cultivars differed for proportions of pseudostem, stem (in 2003 only) and dead material. The chemical composition of the herbage was different among cultivars, with the water‐soluble carbohydrate concentration showing large variation (>0·35). Cultivars differed in susceptibility to crown rust. Herbage intake differed among cultivars in 2002 (>2 kg DM) but not in 2003. Herbage intake was positively associated with sward height, DM yield and green leaf mass. Canopy morphology did not affect herbage intake. Crown rust affected herbage intake negatively. It was concluded that options for breeders to select for higher intake were limited. High‐yielding cultivars and cultivars highly resistant to crown rust were positively related with a high herbage intake.     

Yield,nutritive value and silage fermentation of kura clover‐reed canarygrass and lucerne herbages in northern USA

Excellent winter hardiness, persistence and nutritive value of both kura clover (Trifolium ambiguum M. Bieb.) and reed canarygrass (Phalaris arundinacea L.) suggest that intercropping these species could substitute for lucerne (Medicago sativa L.). The dry matter (DM) yield and nutritive value of herbage, and silage characteristics of kura clover‐reed canarygrass (KC‐RCG) herbage, were compared to those of lucerne over two growth cycles near Arlington, WI, USA. First and second growths of lucerne and KC‐RCG herbage were sampled four times at 1‐week intervals and ensiled for 100 d. Yield of DM of the KC‐RCG was 0·23–0·57 greater than that of lucerne on sampling dates in the first growth cycle, with no differences in DM yield in the second growth cycle. The pH of lucerne silage was lower than that of KC‐RCG silage in the first growth, and the opposite occurred in second growth, which was attributed to maturity differences and the proportion of kura clover in the mixture. Lactate concentration was lower in KC‐RCG than lucerne silages in both growth cycles. The lucerne and KC‐RCG silages had similar in vitro DM digestibility except for the final sampling date in the first growth cycle when neutral‐detergent fibre concentration of KC‐RCG herbage exceeded 550 g kg^?1 DM. Crude protein concentration was greater in lucerne silage than in KC‐RCG silage in both growth cycles. Overall, differences in nutritive value and silage fermentation between the two herbages were minimal across growth cycles. These results suggest that a KC‐RCG sward is a viable alternative to lucerne in northern environments of the USA where lucerne production may be limited by winter injury or edaphic factors.     

Effects of date of autumn closing and timing of winter grazing on herbage production in winter and spring

Growth of grass herbage in Ireland is highly seasonal with little or no net growth from November to February. As a result, feed demand exceeds grass supply during late autumn, winter and early spring. At low stocking rates [≤2 livestock units (LU) ha^?1], there is potential to defer some of the herbage grown in autumn to support winter grazing. This study examined the effects of four autumn‐closing dates and four winter‐grazing dates in successive years on the accumulation of herbage mass and on tiller density in winter and subsequent herbage production at two sites in Ireland, one in the south and one in the north‐east. Closing swards from grazing in early and mid‐September (north‐east and south of Ireland respectively) provided swards with >2 t DM ha^?1 and a proportion of green leaf >0·65–0·70 of the herbage mass above 4 cm, with a crude protein (CP) concentration of >230 g kg^?1 DM and dry matter digestibility (DMD) of >0·700. The effects of autumn‐closing date and winter‐grazing date on herbage production in the subsequent year varied between the two sites. There was no significant effect of autumn‐closing date in the north‐eastern site whereas in the south earlier autumn closing reduced the herbage mass in late March by up to 0·34 t DM ha^?1 and delaying winter grazing reduced the herbage mass in late March by up to 0·85 t DM ha^?1. The effects of later grazing dates in winter on herbage mass continued into the summer at the southern site, reducing the herbage mass for the period from late March to July by up to 2 t DM ha^?1. The effects of imposing treatments in successive years did not follow a consistent pattern and year‐to‐year variation was most likely linked to meteorological conditions.     

Effect of different grazing management systems on the herbage mass and pasture height of a Nardus stricta grassland in western Scotland, United Kingdom

The aims of this study were to examine the effect of three grazing treatments (year‐round stocking rates of 0·8 ewes ha^?1, 0·5 ewes ha^?1 and 0·5 ewes ha^?1 plus grazing cattle in summer), imposed for 4 years, on the herbage mass and surface height of a Nardus stricta‐dominated grassland in western Scotland and to obtain estimates of annual productivity of this grassland. Nardus stricta‐dominated grassland comprised proportionately 0·20 of the grazing area. Stocking rate of sheep had no significant effect on the herbage mass of the grassland in the first 2 years of the experiment, although mean summer pasture heights were significantly higher under the lower stocking rate of sheep. The pasture on the treatment with cattle grazing in summer had a significantly lower herbage mass and lower surface height than the two sheep‐only grazing treatments. Year‐to‐year variation in the herbage mass and surface height of herbage in summer was greater than the effect of treatments. Despite changes in surface height, the structural diversity of the grasslands was not increased by the treatments. The annual production of vascular plant material ranged from 417 g DM m^?2 in 1994 to 628 g DM m^?2 in 1996.     

Effect of harvest date on the chemical composition and nutritive value of Cerastium holosteoides

Abstract Cerastium holosteoides is a short‐lived plant often found in small proportions on dry and mesotropic semi‐natural, species‐rich grassland communities. To obtain more information about its nutritive value, two experiments on Arrhenatheretum elatioris grassland were carried out to examine the effect of harvest date on in vitro organic matter digestibility (IVOMD), neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF), acid‐detergent lignin (ADL), estimated net energy for lactation (NEL) and crude protein (CP) concentrations of C. holosteoides, and selection of this plant by dairy cows grazing on semi‐natural grassland. C. holosteoides starts flowering in spring and continuously develops new flowers on new branches throughout the summer. Harvests were made in relation to particular growth stages of Dactylis glomerata present in the sward: (A) tillering; (B) stem elongation; (C) ear emergence; (D) flowering; and (E) ripening. Chemical composition and nutritive value were evaluated in 1998 and 1999. With advancing maturity, IVOMD of C. holosteoides decreased from 0·771 at growth stage A to 0·485 at growth stage E. At the same time, CP concentration decreased from 153 to 69 g kg^?1 dry matter (DM) and estimated NEL concentration from 6·00 to 4·07 MJ kg^?1 DM. With advancing maturity, there was a significant increase in NDF, ADF and ADL concentrations. In the summer harvest season, C. holosteoides contained significantly higher NDF, ADF and ADL concentrations, lower NEL concentration and had a lower IVOMD value than in the spring. Differences between years were also found for IVOMD and for NDF, ADF, ADL and NEL concentrations. In a grazing experiment in the year 1999, at growth stage B, Simmental cows grazed an A. elatioris sward in which the main species was D. glomerata (0·092), and the proportion of C. holosteoides was 0·034. C. holosteoides was, on average, grazed by cows to the same relative extent as other species in the sward.     

Effects of grazing and precipitation on herbage production,herbage nutritive value and performance of sheep in continental steppe

The present study highlights the effects of sheep grazing and precipitation on herbage and animal performance in a grazed steppe of Inner Mongolia. Experimental data were collected during grazing periods of four consecutive years (2005–2008), and effects were analysed across a gradient of seven grazing intensities. Variation in annual precipitation, reflected by the effect of ‘year’, was the major factor affecting herbage; i.e., the production and nutritive value of herbage increased with increasing precipitation. Herbage parameters were also affected by grazing intensity, as herbage production (HP) and herbage nutritive yields decreased, while herbage nutritive values increased with increasing grazing intensity. The grazing‐induced decrease in herbage nutritive yields suggests that decreases in HP offset the positive effect of grazing on the nutritive value. Liveweight gain (LWG) was predominantly affected by grazing intensity, as LWG per sheep and per ha decreased and increased, respectively, with increasing grazing intensity. However, responses varied among years: LWG per sheep was maximized by light grazing in the drought year and by moderate grazing the wet year. Our results showed that herbage shortage at high grazing intensities reduces LWG per sheep and thus diminishes responses in LWG per ha. Nevertheless, the highest grazing intensity provides highest animal production per ha in the short term; however, this is not sustainable in the mid‐ and long term because decreasing HP induces degradation processes. Based on our results, a reduction in grazing intensity that still provides 78% of the maximum LWG per ha meets the requirements of a sustainable grazing management.     

Open pasture,silvopasture and sward herbage maturity effects on nutritive value and fermentation characteristics of cool‐season pasture

In Appalachian USA, silvopasture offers promise of increased farm productivity. A synchronized, temporal understanding of open pasture (OP) and silvopasture (SP) nutritive characteristics is essential for grazing system development. We examined pasture‐type nutritive‐value relationships when herbage was harvested based on morphological maturity rather than calendar date. Neutral detergent fibre and acid detergent fibre (ADF and NDF) content were greater in silvopasture, while organic matter (OM) was lower (P < 0·05). Digestibility of SP herbage dry matter (DM) and OM tended (P = 0·10) to be lower (418 vs. 471 and 437 vs. 491 g kg^?1 respectively). Neutral detergent fibre digestibility was greater (P < 0·05) for OP than SP forage (538 vs. 480 g kg^?1), and ADF tended to be greater (P = 0·10; 551 vs. 501). Open‐pasture forage fermentation effluent exhibited slightly higher microbial richness and Shannon diversity than SP. However, overall community composition of both bacteria and archaea did not differ between pasture types or sampling times. Pasture types show proximate analyses differences generally favourable to OP, although both have similar overall nutritive value. In addition, the SP sward exhibited a 4‐ to 6‐days delay in reaching equivalent maturity. Conversion of farm woodlots to SP would increase overall herbage production and improve pasture management flexibility.     

Effects of two mixtures of perennial ryegrass cultivars with contrasting heading dates, and differing in spring-grazing frequency and silage harvest date, on characteristics of silage from first-cut swards

This experiment quantified the effects of: (i) heading date of perennial ryegrass, (ii) grazing frequency in spring and (iii) date of silage harvest, on the ensilability of herbages harvested for silage, and on the conservation and estimated nutritive value of the resultant silages. Replicated field plots with two perennial ryegrass mixtures (intermediate‐ and late‐heading cultivars) were subjected to three spring‐grazing regimes (no grazing, grazing in late March and grazing in both late March and late April) and were harvested on four first‐cut harvest dates between 20 May and 21 June. Herbage from each of the four replicates of these 24 treatments was precision‐chopped and ensiled unwilted and with no additive in laboratory silos. Herbage from the sward with the intermediate‐heading cultivar had a higher (P < 0·001) dry‐matter (DM) content and buffering capacity than that from the late‐heading cultivar, whereas water‐soluble carbohydrate concentrations increased (P < 0·001) with more frequent grazing in spring. Later harvesting enhanced herbage ensilability through an increased (P < 0·001) DM content and reduced (P < 0·001) buffering capacity and pH. Fermentation profiles of the silage were not markedly influenced by the cultivar mixture used but grazing in both late March and late April resulted in a more extensive fermentation with the acids produced increasingly dominated by lactic acid. The concentrations of acetic acid, and to a lesser extent, ethanol declined as silage harvest date was delayed. Overall, the relative effects of grass cultivar mixture were smaller than those of spring‐grazing treatment or silage‐harvesting date although on any given harvest date the herbage from the intermediate‐heading cultivar mixture was easier to preserve as silage than herbage from the late‐heading cultivar mixture. Delaying the harvesting of the late‐heading swards by 8 d removed the differences related to growth stage in buffering capacity, pH and DM content.