Effects of cattle grazing on herbage quality in a herbaceous Mediterranean rangeland

The main objective of this study was to determine to what extent grazing pressure and timing modulate the seasonal progression of herbage quality in hilly Mediterranean grassland systems. The study was conducted during six consecutive years between 2003 and 2008 at the Karei Deshe experimental farm, in eastern Galilee, Israel, dominated by rich hemicryptophytic grassland. Treatments included two different grazing intensities, heavy and moderate, with 1·1 and 0·55 cows ha^?1, respectively, and management that included a continuous and a seasonal stocking system that was divided at both intensities into early and late grazing. Herbage samples were analysed for digestibility, crude protein, neutral detergent fibre and acid detergent fibre contents. Significant differences in herbage quality were found between seasons and years. Herbage quality was significantly higher in paddocks grazed continuously or early in the season. Herbage quality increased with increasing grazing intensity as younger herbage and continued re‐growth were maintained during the green season. The greater difference between herbage qualities was found at the peak of the growing season. The significant differences found in herbage quality emphasize the importance of the decision‐making process aimed at improving cattle grazing management in Mediterranean rangelands and its consequences for the sustainability of the system.     

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.     

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.     

Influence of cutting regime and fertilizer application on the botanical composition,yield and nutritive value of herbage of wet grasslands in Central Europe

The changes in dry matter (DM) yield, botanical composition and nutritive value of herbage to ruminants of two wet grasslands, Arrhenatherum elatius grassland (Experiment 1) and a Molinia caerulea fen meadow (Experiment 2), in which a range of cutting and fertilizer treatments were imposed in 1999, were assessed after 4–7 years of treatment imposition. Both experiments had a split‐plot design with four replicates. In Experiment 1 the three main‐plot cutting treatments were two cuts with a delayed first cut, three cuts and four cuts during the growing season of each year. In Experiment 2 the cutting treatments were two cuts with a traditional harvest time, two cuts with a delayed first cut and three cuts. The four sub‐plot fertilizer treatments were an unfertilized control, application of a phosphorus and potassium (PK) fertilizer, application of a nitrogen (N) and PK fertilizer to the first cut only (N₁PK) and application of PK plus N applied to each of two, three or four cuts (N_c PK). Application of fertilizer influenced yield and botanical composition of herbage more than the cutting treatments while the opposite occurred for nutritive value of the herbage. Application of fertilizer increased the proportion of tall grasses in Experiment 1 and forbs in Experiment 2. The proportion of Equisetum palustre, present only in Experiment 1, was reduced from 0·33 to less than 0·01 by increased cutting frequency together with the NPK fertilizer treatments. In Experiment 1 diversity of vascular plants was negatively affected only by the four‐cuts treatment while on both wet grasslands other cutting and fertilizer application treatments had no effect. Changes in DM yield of herbage caused by the cutting and fertilizer application treatments were similar for both vegetation types with DM yield increased significantly by fertilizer application but only slightly or not reduced by increasing the cutting frequency. Nutritive value of herbage was positively correlated with cutting frequency and was most influenced at the first cut.     

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.     

Changes in the herbage nutritive value and yield associated with threshold responses of vegetation to grazing in Mongolian rangelands

We examined the changes in the nutritive value and yield of herbage along a grazing gradient, where abrupt changes in community composition occurred, at multiple ecological sites in Mongolian rangelands. At grassland sites, changes in the herbage nutritive value could be attributed to rapid replacement of perennial grasses or forbs with weedy annual forbs along a grazing gradient. Crude protein (CP) concentration increased sharply in approaching the source of grazing gradient, whereas neutral detergent fibre and metabolizable energy (ME) concentrations decreased sharply. As ME can be utilized as a main index of herbage nutritive value, these results indicated its overall loss with severe grazing. Consequently, gradual increases in the yields of CP and ME in the direction of the gradient source at the grassland sites did not necessarily indicate the improvement of rangeland condition. In contrast, at shrubland sites, we could not generally detect any significant trends in the herbage nutritive value. The yield of ME gradually decreased in the direction of gradient source, suggesting that grazing affects herbage yield rather than herbage feed value at shrubland sites. Thus, the nutritive value and yield of herbage can be modified greatly in association with nonlinear responses of vegetation to livestock grazing.     

Influence of solar radiation on the productivity and nutritive value of herbage of cool-season species of an understorey sward in a mature conifer woodland

Silvopastoral systems in the Appalachian region of the USA could increase the carrying capacity of livestock and contribute to a reliable supply of high‐quality herbage. In 2000, 2001 and 2002, the influence of solar radiation [0·20, 0·50 or 0·80 of maximum solar radiation (MSR); treatments 20‐, 50‐ and 80‐MSR respectively] on the productivity and nutritive value of a mixture of sown grasses and legumes established under a mature stand of conifers was investigated. Yields of dry matter (DM), crude protein (CP), total non‐structural carbohydrates (TNC) and total digestible nutrients (TDN) were greater for the 80‐MSR treatment except in 2000 when DM yield did not differ. As a proportion of the sward, introduced species (Dactylis glomerata L., Trifolium repens L., and Lolium perenne L.) increased over time for the MSR‐80 treatment, corresponding with a decrease in the proportion of bare area and of non‐introduced species. CP concentration of herbage was 207 g kg^?1 DM or greater across treatments and years with higher concentrations on the 20‐ and 50‐MSR treatments. Herbage from the 80‐MSR treatment had a greater concentration of TNC than that of the 20‐ and 50‐MSR treatments. Estimated concentration of TDN was similar for all treatments in 2000 and greater for the 80‐MSR treatment than the other two treatments in 2001 and 2002. High CP concentrations in herbage, as a result of appropriate thinning of trees in an Appalachian silvopastoral systems, could be utilized as a protein supplement to herbage with low CP and higher fibre concentrations.     

Effects of nitrogen fertilization and cutting intensity on the agronomic performance of warm‐season grasses

Responses of grasses to N fertilization are affected by cutting intensity although little is known regarding the interactions of these factors in warm‐season grasses. Pre‐cutting canopy height, herbage accumulation and changes in the nutritive value of warm‐season grasses in response to four different management strategies were assessed from October 2011 to September 2014. Treatments included two cutting intensities (70 vs. 50% depletion of canopy height set by 95% light interception), two N fertilization levels (zero vs. 300 kg N ha^?1 year^?1) and six perennial C₄ grass species (Axonopus catharinensis; Cynodon spp. hybrid Tifton 85; Hemarthria altissima cv. Flórida; Megathyrsus maximus cv. Aruana; Paspalum notatum cv. Pensacola; and Urochloa brizantha cv. Marandu) grown in monoculture in a factorial experimental design. Canopy height varied among grass species, cutting intensity and N treatments, mainly among seasons, indicating that more than one management target (i.e. canopy height) existed throughout the plant growth cycle for each species. The largest herbage accumulation occurred in the N fertilization treatments for most species, regardless of cutting intensity. Nitrogen fertilization and 50% depletion of canopy height increased the leaf proportion and decreased the neutral detergent fibre content. Overall, N fertilization had a stronger positive impact than cutting intensity on the acid detergent fibre content, dry‐matter digestibility and crude protein content, but the magnitudes of the responses were species‐specific.     

Nutritional quality of semi-arid grassland in western Spain over a 10-year period: changes in chemical composition of grasses, legumes and forbs

From 1987 to 1996, the nutritional quality of the main botanical components (grasses, legumes and forbs) in semi-arid grasslands in the dehesa ecosystem in western Spain was analysed. Herbage samples were collected at the end of spring, in 30 locations, at two different topographic positions (upper and lower slope zones). Herbage mass over 2 cm and proportion of botanical components were estimated and samples were analysed for crude protein, neutral-detergent fibre (NDF), hemicellulose, cellulose, lignin and in vitro dry matter digestibility (DMD). Analysis of variance revealed a significant effect of sampling year on the herbage mass, proportion of botanical components and their nutritional quality. The three botanical groups, grasses, legumes and forbs, followed similar year-to-year trends in their crude protein, cellulose and lignin contents and in vitro DMD. Herbage mass was not significantly related to any meteorological variables, suggesting that interannual variation in biomass production of botanically complex pastures cannot be explained by a single factor. However, annual precipitation was significantly related to the proportion of the botanical group that was dominant at each slope zone: grasses in the lower zone and forbs in the upper zone. In the upper zone, spring precipitation explained part of the interannual variation in the NDF, cellulose, lignin contents and in vitro DMD of the botanical components.     

Seasonal dynamics of biomass production and herbage quality of three grasslands with contrasting functional compositions

Classifying grasses into plant functional types (PFT) according to their strategy of nutrient capture (PFT A, B and b) or nutrient conservation (PFT C) is claimed to predict variability in biomass production and herbage quality in grasslands. PFT A, B and b are characterized by higher production than PFT C, with higher nutritive value, which decreases rapidly. PFT C is characterized by lower nutritive value, which remains more stable in time. The aim of this study was to quantify the consequences of PFT composition at the community level on the seasonal dynamics of biomass and herbage quality for livestock feed. We studied three grasslands located in the same area with contrasting PFT composition and classified PFT A, PFT Bb and PFT C. The dynamics of vegetation stages, dry‐matter yield and nutritive value were followed over three vegetation cycles in 2007–2008. In the first cycle, biomass accumulation was high for the PFT A and PFT Bb grasslands and the high quality of herbage declined rapidly with the reproductive development. By contrast, biomass accumulation was slow in the PFT C grassland, with a lower quality that declined slowly, consistent with the later reproductive development. For regrowth cycles, the same ranking of grasslands was observed for biomass accumulation, and differences in digestibility were similar to those observed at the beginning of the first vegetation cycle. Combining type of grassland with sum of temperature for the first cycle and regrowth days for the second and third vegetation cycles provided quantitative models of herbage biomass and quality.     

NUTRITIONAL PROBLEMS OF LIVESTOCK PRODUCTION FROM SEMI-ARID GRASSLANDS IN THE TROPICS*

Herbage of very low quality forms the main diet of ruminants on the semi-arid grasslands in the tropics for several months of the year. The grasses available have a high content of dry matter and crude fibre, a low digestibility and a very low crudeprotein content. Ruminants are unable to eat enough herbage to supply the nutrients required for their body functions and it is this inadequacy which is the major factor limiting animal production from semi-arid grasslands in the tropics.     

Plant diversity effects on herbage production and compositional changes in New Zealand hill country pastures

A small‐plot field experiment on grazed hill country pastures in the North Island of New Zealand was conducted to examine the productivity and compositional characteristics of swards in response to variation in pasture species diversity. The balanced incomplete factorial design incorporated variation in location, slope, soil fertility and combinations of eight plant functional groups (C₄ grasses, annual grasses, annual legumes, perennial C₃ grasses, perennial legumes, perennial forbs, ryegrass and browntop). Net herbage accumulation and botanical composition were measured at 18 months (spring) and 24 months (autumn) after oversowing following application of a systemic herbicide. Analysis of variance indicated a significant positive relationship between the number of functional groups sown and herbage accumulation of the sown species in spring, but not with total herbage accumulation. Regression analysis showed that herbage accumulation was also affected by the identity of the functional groups. However, the statistical models indicated that pasture productivity was most strongly influenced by site factors. There was a significant negative relationship between both the number and herbage accumulation of unsown species and the number of functional groups sown, indicating a positive relationship between diversity and resistance to invasion by unsown species. A comparison of the vegetation between the plots before and after oversowing showed that those more diverse prior to sowing returned to their initial composition more rapidly, evidence that diverse vegetation was more resilient in the face of disturbance.     

Effects of species richness and functional groups on chemical constituents relevant for methane yields from anaerobic digestion: results from a grassland diversity experiment

Changes in livestock production systems have led to land‐use changes and abandonment, especially of semi‐natural grassland in agriculturally less favoured regions. The generation of energy from biomass of extensive, high‐diversity grasslands can be an alternative to their abandonment, and anaerobic digestion is one possible method for converting grassland biomass into energy. However, little is known about the effects of species richness (SR) and functional groups on chemical constituents relevant for anaerobic digestion and the resulting energy potential. In this study, changes in the herbage chemical constituents that are relevant for forage quality were studied along a well‐defined diversity gradient (one to sixty species) and across different combinations of functional groups (legumes, small herbs, tall herbs and grasses). Substrate‐specific methane yield (CH_4 sub) was estimated through the concentrations of forage‐quality parameters such as crude fibre (CF), crude protein (CP), crude lipid, nitrogen‐free extract and their documented digestibility values, as well as the respective methane yields. Results show that with increasing SR, the CF increased and CP decreased, even though these effects could not be fully disentangled from the presence of grasses. These trends led to a negative effect of SR on CH_4 sub, while the area‐specific methane yield (CH_4 area = CH_4 sub × biomass yield) increased due to a strong increase in biomass with increasing SR. The CH_4 sub was increased when legumes were present, and it declined with the presence of grasses. Generally, CH_4 sub and CH_4 area varied between functional‐group monocultures and all functional‐group mixtures.     

Seasonal productivity and nutritive value of temperate grasses found in semi-natural pastures in Europe: responses to cutting frequency and N supply

Monocultures of thirteen perennial C₃ grass species that co‐occur in temperate semi‐natural grassland communities in Europe were compared in a factorial field design of two levels of N supply and two levels of cutting frequency. Above‐ground yield of dry matter (DM), crude protein (CP) concentration and pepsin‐cellulase DM digestibility of herbage were measured in two successive years. Species was the largest source of variability in yield of DM and DM digestibility of herbage, while CP concentration of herbage responded more to management factors. The highest mean DM yields and values of DM digestibility of herbage were achieved in spring for Festuca arundinacea and in autumn for Phleum pratense. Poa trivialis and Festuca rubra had the lowest DM yield and DM digestibility values, respectively, regardless of seasons and treatments. For all species CP concentration in herbage increased in response to an increase in cutting frequency and N supply by an average of 46 and 34 g kg^?1 DM respectively. Differences between years and seasons indicated the importance of plant phenology on nutritional variables and the influence of environmental factors on species performance. Species ranking was compared according to their annual digestible DM and CP yields. The results show that some grasses have a nutritive value which is comparable to that of forages selected for high yields.     

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.     

Changes in nutritive value and herbage yield during extended growth intervals in grass–legume mixtures: effects of species,maturity at harvest,and relationships between productivity and components of feed quality

There is a lack of information on the effects of companion species in grass–legume mixtures on herbage yield and quality changes during prolonged growth. Such information is relevant for harvest planning and estimation of consequences for feeding value of conserved feed when harvesting is delayed. Perennial ryegrass was sown with each of four legumes: red clover, white clover, lucerne and birdsfoot trefoil, and white clover was sown with hybrid ryegrass, meadow fescue and timothy. Effects of species composition on herbage yield, contents of N, neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin, ash and in vitro organic matter digestibility (IVOMD) were studied in entire herbage and in component species during 2 years in a small‐plot cutting trial in Denmark. In May and August, the dynamic development of components of feed value and their interrelationships were investigated by sampling at optimum harvest date (i.e., normal practice) ± 1 week (t = ?1 to t = +1). Herbage digestibility and contents of N and ash decreased while those of fibre compounds increased during the 2 weeks from t = ?1 to t = 1 in all species. In May, contents of ADF and lignin increased at a faster rate in legumes than in grasses; in August, NDF and ADF increased most quickly in legumes. Generally, N contents and IVOMD declined at similar rates in grasses and legumes, but, within each group, differences in yield and quality development occurred among species. The relationship between weekly growth rate and change in quality parameters differed among species and functional groups, i.e., grasses and legumes. Results are discussed in the context of quantifying the impact of delaying the harvest date of grass–legume mixtures and relationships between productivity and components of feed quality.     

Herbage mass and nutritive value of herbage of extensively managed temperate grasslands along a gradient of shrub encroachment

Semi-natural grasslands often serve as important reserves of biodiversity. In Europe extensive grazing by livestock is considered an appropriate management to conserve biodiversity value and to limit shrub encroachment. However, little is known about the influence of shrubs on agronomic values. A gradient analysis of shrub-invaded temperate grasslands (from shrub-free to pioneer forest) in Germany was carried out to test the hypothesis that herbage mass and variables describing nutritive value of herbage decrease with increasing shrub encroachment. The herbage mass of dry matter (DM), variables describing the nutritive value of herbage, composition of the vegetation and mean of Ellenberg's indicator values were analysed with respect to the extent of shrubs. There was a reduction of herbage mass of DM from 3570 to 210 kg ha⁻¹ with increasing shrub encroachment. Metabolizable energy concentration of herbage ranged from 8·9 to 10·2 MJ kg⁻¹ DM and crude protein concentration from 72 to 171 g kg⁻¹ DM, both measures being positively correlated with shrub occurrence. Increasing shrub occurrence was associated with a decrease in water-soluble carbohydrates concentration (from 151 to 31 g kg⁻¹) and a reduction in the indicator 'forage value'. The results indicate a potentially large agronomic value for shrub-encroached temperate grasslands.     

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.     

Morphological development and nutritive value of herbage in five temperate grass species during primary growth: analysis of time dynamics

In a 2‐year field experiment, morphological development and measures of the nutritive value of herbage for livestock during primary growth in Meadow foxtail, Tall oatgrass, Cocksfoot, Perennial ryegrass and Yorkshire fog were investigated. All measured variables were affected significantly by both species and sampling date, and their interaction (P < 0·001), in the period of primary growth. Changes with time in mean stage weight for Meadow foxtail and Cocksfoot were different from the other species due to their indeterminate growth habits. Mean stage weight of Tall oatgrass and Yorkshire fog increased more rapidly than that of Perennial ryegrass with time. Changes in mean stage weight with time were described by linear, parabolic and sigmoid relationships. Crude protein (CP) concentration of herbage was higher for Cocksfoot and Meadow foxtail than for Perennial ryegrass. A parabolic relationship of CP concentration with time was typical for all the species. Concentrations of neutral‐detergent fibre (NDF) and acid‐detergent fibre (ADF) in herbage of the species differed most during the mid‐period of primary growth. Their increases with time showed curvilinear (sigmoid and parabolic) relationships. Perennial ryegrass had lower concentrations of both NDF and ADF in herbage than the other species. Differences between the in vitro dry matter (DM) digestibility among the grasses increased in mid‐ and late periods of primary growth. Perennial ryegrass had higher values for in vitro DM digestibility but the difference from other species was small in the early period of primary growth and from cocksfoot in the late period of primary growth. In vitro DM digestibility showed, in most cases, a sigmoid and, in others, a linear decrease with time. Principal component analysis showed that perennial ryegrass and meadow foxtail were the most distinctive of the species in characteristics relating to morphological development and the nutritive value of herbage to livestock.