Effect of grazing management on herbage protein concentration,milk production and nitrogen excretion of dairy cows in mid‐lactation

The objective of this experiment was to use diurnal and temporal changes in herbage composition to create two pasture diets with contrasting ratios of water‐soluble carbohydrate (WSC) and crude protein (CP) and compare milk production and nitrogen‐use efficiency (NUE) of dairy cows. A grazing experiment using thirty‐six mid‐lactation Friesian x Jersey cows was conducted in late spring in Canterbury, New Zealand. Cows were offered mixed perennial ryegrass and white clover pastures either in the morning after a short 19‐day regrowth interval (SR AM) or in the afternoon after a long 35‐day regrowth interval (LR PM). Pasture treatments resulted in lower pasture mass and greater herbage CP concentration (187 vs. 171 g kg^?1 DM) in the SR AM compared with the LR PM but did not affect WSC (169 g kg^?1 DM) or the ratio of WSC/CP (1·0 g g^?1). Cows had similar apparent DM (17·5 kg DM cow^?1 d^?1) and N (501 g N cow^?1 d^?1) intake for both treatments. Compared with SR AM cows, LR PM cows had lower milk (18·5 vs. 21·2 kg cow^?1 d^?1), milk protein (0·69 vs. 0·81 kg cow^?1 d^?1) and milk solids (1·72 and 1·89 kg cow^?1 d^?1) yield. Urinary N concentration was increased in SR AM, but estimated N excretion and NUE for milk were similar for both treatments. Further studies are required to determine the effect of feeding times on diurnal variation in urine volume and N concentration under grazing to predict urination events with highest leaching risk.     

The effect of two contrasting concentrate allocation strategies on the performance of grazing dairy cows

The objective of this study was to examine the performance of grazing Holstein–Friesian dairy cows when equal quantities of concentrates were offered using either a flat‐rate or a feed‐to‐yield allocation strategy. The study involved fifty‐six cows (twenty primiparous and thirty‐six multiparous) and continued for 122 d, with concentrate feed levels adjusted on five occasions during the study (every four weeks approximately). Total concentrate intake over the duration of the study was 463 and 525 kg cow^?1 (3·8 and 4·3 kg cow^?1 d^?1) for multiparous and primiparous animals respectively. Concentrate allocation strategy had no effect on average daily milk yield, milk fat or protein content, milk‐fat‐plus‐protein yield or end‐of‐study live weight and body condition score (P > 0·05). In conclusion, concentrate allocation strategy had minimal impact on the overall performance of these mid/late lactation cows when concentrate feed levels were modest and grass availability was high.     

Defoliation pattern, foraging behaviour and diet selection by lactating dairy cows in response to sward height and herbage allowance of a ryegrass-dominated pasture

The effects of sward surface height (SSH) and daily herbage allowance (HA) on the defoliation pattern and grazing mechanics of early lactation dairy cows grazing on irrigated perennial ryegrass–white clover pasture were studied. The hypothesis tested was that SSH and HA affect intake and diet selection through their effects on the pattern of defoliation which is influenced by the resistance to prehension bites. Factorial combinations of two initial SSH (14 and 28 cm) and two daily HA (35 and 70 kg DM cow^?1 d^?1) were examined in a replicated experiment. The peak longitudinal tensile force required to break the sward portion encompassed in a 100 cm² area [bite fracture force (BFF₁₀₀)] was measured as an index of the resistance to prehension. The volume of herbage defoliated and herbage intake increased with SSH (P < 0·05) and HA (P < 0·01). Corresponding to an increase in HA from 35 to 70 kg DM cow^?1 d^?1, there was a proportional increase in the total defoliation area (TDA) and intake by 0·24 and 0·55 in the short sward compared with 0·16 and 0·32 in the tall sward respectively. The results of this experiment suggest that a consistent spatial pattern of reduction of the canopy exists during defoliation by cows and that the volume of sward canopy defoliated is the major variable affecting herbage intake. The BFF increased down the sward profile at a rate that was higher (P < 0·05) for the taller sward than for the shorter sward. It is proposed that a relatively lower resistance to prehension in the short sward compared with the tall sward explains the greater proportionate increase in TDA and intake corresponding to an increase in HA. The rate at which BFF₁₀₀ increases down the sward profile is suggested as a sward physical variable that can influence the defoliation process. The estimated time and energy costs of prehension bites are discussed in the context that larger bites are handled more efficiently than smaller bites.     

Species interactions in a grassland mixture under low nitrogen fertilization and two cutting frequencies: 1. dry‐matter yield and dynamics of species composition

Four‐species mixtures and pure stands of perennial ryegrass, tall fescue, white clover and red clover were grown in three‐cut and five‐cut systems at Ås, southern Norway, at a low fertilization rate (100 kg N ha^?1 year^?1). Over a three‐year experiment, we found strong positive effects of species diversity on annual dry‐matter yield and yield stability under both cutting frequencies. The overyielding in mixtures relative to pure stands was highest in the five‐cut system and in the second year. Among the possible pairwise species interaction effects contributing to the diversity effect, the grass–grass interaction was the strongest, being significant in both cutting systems and in all years. The grass–legume interactions were sometimes significant, but no significant legume–legume interaction could be detected. Competitive relationships between species varied from year to year and also between cutting systems. Estimations based on species identity effects and pair‐specific interactions suggested that the optimal proportions of red clover, white clover, perennial ryegrass and tall fescue in seed mixtures would have been around 0·1, 0·2, 0·4 and 0·3 in the three‐cut system, and 0·1, 0·3, 0·3 and 0·3 in the five‐cut system.     

Influence of sward condition on leaf tissue turnover in tall fescue and tall wheatgrass swards under continuous grazing

Two experiments were carried out on a tall fescue sward in two periods of spring 1994 and on a tall wheatgrass sward in autumn 2001 and spring 2003 to analyse the effect of sward surface height on herbage mass, leaf area index and leaf tissue flows under continuous grazing. The experiment on tall fescue was conducted without the application of fertilizer and the experiment with tall wheatgrass received 20 kg P ha^?1 and a total of 100 kg N ha^?1 in two equal dressings applied in March (autumn) and end of July (mid‐winter). Growth and senescence rates per unit area increased with increasing sward surface height of swards of both species. Maximum estimated lamina growth rates were 28 and 23 kg DM ha^?1 d^?1 for the tall fescue in early and late spring, respectively, and 25 and 36 kg DM ha^?1 d^?1 for tall wheatgrass in autumn and spring respectively. In the tall fescue sward, predicted average proportions of the current growth that were lost to senescence in early and late spring were around 0·40 for the sward surface heights of 30–80 mm, and increased to around 0·60 for sward surface heights over 130 mm. In the tall wheatgrass sward the corresponding values during spring increased from around 0·40 to 0·70 for sward surface heights between 80 and 130 mm. During autumn, senescence losses exceeded growth at sward surface heights above 90 mm. These results show the low efficiency of extensively managed grazing systems when compared with the high‐input systems based on perennial ryegrass.     

Milk-production potential of different sward types in a temperate southern Australian environment

The milk-production potential of different sward types was measured in each of the four seasons of the year in a replicated experiment in south-west Victoria, Australia. Dairy cows were offered ad libitum allowances of a 'short-term winter' sward, based on Italian ryegrass (treatment STW), a 'long-term winter' sward, based on a winter-active tall fescue (treatment LTW), a 'long-term summer' sward, based on a summer-active tall fescue (treatment LTS) and a Control sward (perennial ryegrass) in four seasons (days in milk in parentheses): spring (November dairy cows, 124), summer (February, 227), autumn (May, 234) and winter (August, sixty-four). A 'short-term summer' sward, based on chicory and white clover (treatment STS), was also included in summer. There was a significant season × treatment interaction caused by a more gradual decline in milk yield from peak for cows grazing treatment LTS compared to the Control treatment in the transition period from spring to summer. In summer, cows grazing treatment STS produced more milk (1·41 kg fat plus protein per cow d⁻¹) than cows grazing all other treatments (0·92 kg per cow d⁻¹) because of the superior nutritive value of herbage of pre-grazing pasture and higher apparent dry-matter intakes. Swards based on alternative species to perennial ryegrass are capable of supporting milk production that is at least comparable over an annual cycle.     

Comparison of the performance of dairy cows offered kale,swedes and perennial ryegrass herbage in situ and perennial ryegrass silage fed indoors in late pregnancy during winter in Ireland

The effects on the performance of dairy cows offered kale, swedes, and perennial ryegrass in situ and perennial ryegrass silage fed indoors to dairy cows pre‐partum during winter in Ireland was examined. Eighty‐eight spring‐calving dairy cows were randomly assigned to one of four offered treatments; (i) 8 kg of dry matter (DM) of kale leaf and stem + 4 kg DM of perennial ryegrass silage (treatment K), (ii) 8 kg DM of the root and leaf of swedes + 4 kg DM of perennial ryegrass silage (treatment S), (iii) 12 kg DM of perennial ryegrass herbage (treatment G) offered in situ and (iv) perennial ryegrass silage offered ad libitum indoors (treatment ID). Cows on treatments K, S and ID had a greater (P < 0·001) increase in body condition score (0·20, 0·14 and 0·50 units respectively) pre‐partum than cows on treatment G which lost 0·22 units. Pre‐partum treatment had no effect on variables of milk production in the following lactation. In the first 100 d of lactation, cows on treatment G pre‐partum had a lower milk fat concentration (35·6 g kg^?1) compared with cows on treatments S and ID (38·3 and 39·3 g kg^?1 respectively). There was no effect of treatment on the intervals between parturition and first insemination (mean 74·6 d) and conception (mean 96·1 d). The results suggest that offering kale and swedes to dairy cows pre‐partum resulted in a similar lactation performance to dairy cows grazing a perennial ryegrass sward or offered perennial ryegrass silage indoors.     

Effects of predicted milk yields sustained by grazed grass on dairy cow performance and concentrate requirements throughout the grazing season

The objective of this study was to examine the effects of predicted milk yields sustained by grazed grass (‘Milk‐from‐Grass’: LOW, MED or HIGH) and Parity (primiparous or multiparous) on the performance and concentrate requirements of grazed Holstein‐Friesian dairy cows offered concentrates on a ‘feed‐to‐yield’ basis during the grazing season. The mean Milk‐from‐Grass values assigned to cows in the LOW, MED and HIGH treatment groups (sixteen multiparous and eight primiparous cows per group) during the experiment (24 May to 2 October; 131 d) were 12·7, 15·4 and 18·1 kg cow^?1 d^?1, respectively. Concentrate allocations were adjusted every two weeks (approximately) based on individual cows’ milk yields, and concentrate was offered at a rate of 0·45 kg for each kg of milk produced above the assigned Milk‐from‐Grass value at that time. Increasing Milk‐from‐Grass from LOW to MED to HIGH decreased both the mean daily concentrate allocations (4·90, 3·17 and 1·79 kg cow^?1 d^?1, respectively) and milk yields (23·8, 21·8 and 19·0 kg cow^?1 d^?1) of the cows. Cows in the LOW treatment group had lower mean and final (i.e. at the end of the study) BCS and LW than those in the MED or HIGH groups. The effects of Milk‐from‐Grass were similar for both primiparous and multiparous cows.     

Effects of post‐grazing herbage height and concentrate feeding on milk production and major milk fatty acids of dairy cows in mid‐lactation

Milk fatty acids (FA) were compared in mid‐lactation dairy cows in four feeding systems combining grazing management and supplementation. The four treatments were factorial combinations of compressed herbage grazed to 3·7 or 4·6 cm post‐grazing height, with or without concentrate feeding (3·6 kg cow^?1 d^?1). Milk yield and composition were measured for four groups of eight Friesian × Jersey dairy cows over 3 weeks in mid‐lactation for cows that had grazed treatments for 64 d from early spring. Milk yield was higher in cows fed concentrate plus herbage (23·9 kg d^?1 cow^?1) than cows fed herbage only (20·3 kg d^?1 cow^?1). Milk fat percentage was higher in cows fed herbage only (5·5%) than that fed herbage plus concentrate (5·1%). Milk protein percentage was higher in cows fed herbage plus concentrate (4·0%) than that fed herbage only (3·7%). The concentrations of conjugated linoleic acids c9, t11, C18:0, C18:1 t11 and C18:2 t9, c12 FA were lower where concentrate was fed. The concentrations of C18:1 t10, C18:1 t5, t8 and C18:2 c9, c12 FA were higher where concentrate was fed. The concentrations of C18:1 c6, C18:1 c9, C18:1 t9 and C18:3 c6,9,15 were unaffected by concentrate feeding. Post‐grazing herbage height had no significant effect on milk yield or concentration of milk FA. Provided dairy cows are harvesting leafy material of similar nutrient and FA concentration, post‐grazing herbage height does not appear to alter milk FA and the supply of high energy concentrates is more influential on milk FA profiles.     

Species interactions in a grassland mixture under low nitrogen fertilization and two cutting frequencies. II. Nutritional quality

Mixtures and pure stands of perennial ryegrass, tall fescue, white clover and red clover were grown in a three‐cut and a five‐cut system in southern Norway, at a low fertilization rate (100 kg N ha^?1 year^?1). The nutritional quality (annual weighted averages) of the dried forage from the two‐first harvesting years was analysed. There was no significant effect of species diversity on crude protein (CP) concentration. In the three‐cut system, we found a significant species diversity effect leading to 10% higher concentrations of acid detergent fibre (ADF), 20–22% lower concentrations of water‐soluble carbohydrate (WSC) and 4% lower net energy for lactation (NE_L) concentrations in mixtures compared with pure stands (averaged across the two‐first years). In the five‐cut system, similar effects were seen in the first year only. This diversity effect was associated with a reduction in WSC and NE_L concentrations and an increase in ADF, NDF and CP concentrations in the grass species, and not in red clover, when grown in mixtures. This is thought to be a combined result of better N availability and more shading in the mixtures. Species diversity reduced the intra‐annual variability in nutritional quality in both cutting systems.     

Effects of grass pasture and concentrate-based feeding systems for spring-calving dairy cows in early spring on performance during lactation

The effect of offering a total mixed ration of silage and concentrate (proportionately 0·44 silage) system [indoor feeding system (IF)] was compared with grazing at a high daily herbage allowance with a low level of concentrate supplementation [early grazing system (EG)] in early spring on the performance of spring‐calving dairy cows in Ireland. Sixty‐four spring‐calving Holstein–Friesian dairy cows (mean calving date, 2 February) were allocated to one of two systems between 16 February and 4 April 2004. An equal number of primiparous and multiparous cows were assigned to each system. The dairy cows on the IF system were housed for a 7‐week period and offered a diet of 10·9 kg DM cow^?1 d^?1 (s.d. 2·3) of concentrate, the remainder of the diet was 8·6 kg DM cow^?1 d^?1 (s.d. 1·9) of grass silage. The dairy cows on the EG system were offered a mean daily herbage allowance of 15·1 kg DM cow^?1 d^?1 (s.d. 3·7) and were supplemented with 3·0 kg DM cow^?1 d^?1 (s.d. 1·0) of concentrate. There was no difference in milk yield between the two systems but the cows in the EG system had a higher milk protein concentration (2·9 g kg^?1) and a higher milk protein yield than in the IF system. Milk fat concentration was higher for cows in the IF than EG system (3·0 g kg^?1). There was no difference in total daily dry‐matter intake between the systems, measured in week 6 of the study. Mean live weight of the cows in the IF system was greater than in the EG system. The results of the study suggest that a slightly greater performance can be achieved by a system offering a high daily herbage allowance to spring‐calving dairy cows in early lactation compared with a system offering a total mixed ration containing a high proportion of concentrate with grass silage.     

Seasonal nitrogen effects on nutritive value in binary mixtures of tall fescue and bermudagrass

The addition of cool‐season, tall fescue [Lolium arundinaceum (Schreb.) Darbysh.], to warm‐season, bermudagrass [Cynodon dactylon (L.) Pers.], pastures can improve forage productivity and nutritive value. Effects of four binary mixtures consisting of cv. Flecha (incompletely summer dormant) and cv. Jesup (summer active) tall fescue overseeded into established stands of cv. Russell and cv. Tifton 44 bermudagrass and three seasonal N treatments were evaluated on dry‐matter (DM) yield, crude protein (CP), in vitro true digestible DM (IVTDDM), acid detergent fibre (ADF) and neutral detergent fibre (NDF). Nitrogen‐timing treatments were 168 kg N ha^?1 (as ammonium nitrate) split into three applications per season with an additional 8·6 t ha^?1 of broiler litter (as‐is moisture basis) split into two applications varied to favour either tall fescue (in October and January), bermudagrass (in March and May) or both grasses (in January and March). Treatment effects were determined in samples of mixed herbage harvested in April, May, July, August and September of 2009 and 2010. Regardless of bermudagrass cultivar, herbage DM yield was greater (P < 0·05) in Flecha–bermudagrass than Jesup–bermudagrass in July of both years and in August 2010. Nutritive value generally was greatest in Jesup–Tifton 44, based on high CP and IVTDDM, and low ADF and NDF. Averaged across mixtures, avoiding fertilizer N and litter applications beyond April increased (P < 0·01) DM yield in April and May and IVTDDM in July (603 vs. 629 g kg^?1; 2‐year average) and August (618 vs. 660 g kg^?1) compared with applications in January–July. The timing of N and broiler litter applications on tall fescue–bermudagrass to favour growth of tall fescue appeared to increase fescue cover during the cool season and nutritive value of the mixed herbage during the warm season.     

Micronutrient concentrations in common and novel forage species and varieties grown on two contrasting soils

We investigated differences between forage species with regard to micronutrients that are essential to sustain livestock health. Five grasses (timothy, perennial ryegrass, meadow fescue, tall fescue and cocksfoot), three legumes (red clover, white clover and birdsfoot trefoil) and four forbs (ribwort plantain, salad burnet, caraway and chicory) were grown on one micronutrient‐poor/low pH soil and one micronutrient‐rich/high pH soil (outdoor pot experiment). In addition, six grasses (timothy, perennial ryegrass, meadow fescue, tall fescue, Festulolium hybrid and cocksfoot) and one legume (red clover) were field‐grown on the micronutrient‐poor soil. Of the twelve pot‐grown species, herbage of chicory, red clover and white clover generally had the highest micronutrient concentrations (maximum Co, Cu, Fe and Zn concentrations were 0·23, 9·8, 233 and 109 mg kg^?1 DM, respectively), except for Mo, which was highest in the clovers (10·6 mg kg^?1 DM), and Mn, which was highest in cocksfoot (375 mg kg^?1 DM). Soil type had the strongest effect on plant Mo and Mn concentrations. We also investigated differences in micronutrients between varieties, but they were generally few and negligible. The results indicate that choice of forage species is of major importance for micronutrient concentrations in herbage and that soil type exerts a major effect through pH. Forage of chicory, red clover and white clover generally met the requirements of high‐yielding dairy cows with regard to most micronutrients; therefore, diversification of seed mixtures so as to include these species could increase micronutrient concentrations in forage.     

Effect of feed space allowance and period of access to food on dairy cow performance

Two experiments were conducted to examine the ‘long‐term’ effect of feed space allowance and period of access to feed on dairy cow performance. In Experiment 1, three horizontal feed space allowances (20, 40 and 60 cm cow^?1) were examined over a 127‐d period (14 cows per treatment). In Experiment 2, 48 dairy cows were used in a continuous design (10‐week duration) 2 × 2 factorial design experiment comprising two horizontal feed space allowances (15 and 40 cm cow^?1), and two periods of access to feed (unrestricted and restricted). With the former, uneaten feed was removed at 08·00 h, while feeding took place at 09·00 h. With the latter, uneaten feed was removed at 06·00 h, while feeding was delayed until 12·00 h. Mean total dry‐matter (DM) intakes were 19·0, 18·7 and 19·3 kg cow^?1 d^?1 with the 20, 40 and 60 cm cow^?1 treatments in Experiment 1, and 18·1 and 18·2 kg cow^?1 d^?1 with the ‘restricted feeding time’ treatments, and 17·8 and 18·1 kg d^?1 with the ‘unrestricted feeding time’ treatments (15 and 40 cm respectively) in Experiment 2. None of milk yield, milk composition, or end‐of‐study live weight or condition score were significantly affected by treatment in either experiment (P > 0·05), while fat + protein yield was reduced with the 15‐cm treatment in Experiment 2 (P < 0·05). When access to feed was restricted by space or time constraints, cows modified their time budgets and increased their rates of intake.     

Nitrogen flows and balances in four grassland‐based systems of dairy production on a clay‐loam soil in a moist temperate climate

This study examined productivity, nitrogen (N) flows and N balances in grassland‐based systems of dairy production in Ireland. There were four stocking densities of dairy cows on grass/white clover pastures and four inputs of N as fertilizers, concentrates and biological fixation over 2 years; 2001 and 2002. Annual stocking densities were 1·75, 2·10, 2·50 and 2·50 cows ha^?1. Associated N inputs were 205, 230, 300 and 400 kg ha^?1 respectively. There were eighteen cows per system. Cows calved within a 12‐week interval in spring with a mean calving date of 28 February and lactation extended until mid‐December in each year. There were no differences in annual milk yield (6337 kg cow^?1; s.e.m. 106·1), live weight or body condition score. Pre‐grazing N concentrations in herbage increased (P < 0·001) with increasing N input, whereas there were no differences in N concentrations in silage reflecting optimum N inputs for silage production. Grazed herbage accounted for 0·64, silage 0·26 and concentrates 0·10 of annual dry matter consumed by the cows. Annual intakes of N ranged from 144 to 158 kg cow^?1 and were mostly influenced by N concentration in grazed herbage. Annual output of N in milk and liveweight change was 38 kg cow^?1 and was not different between systems. Annual N surpluses increased with increasing N inputs from 137 to 307 kg ha^?1, whereas the proportion of N inputs recovered in products declined from 0·34 to 0·24. More efficient N use was associated with lower N inputs and in particular lower N concentrations in grazed herbage.     

Performance and quality of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) and mixtures of both species grown with or without white clover (Trifolium repens L.) under cutting management

There is increasing interest in tall fescue (Festuca arundinacea Schreb.) in Western Europe and elsewhere, mainly because of its better drought resistance and yield potential compared with perennial ryegrass (Lolium perenne L.). Important drawbacks of tall fescue, compared with perennial ryegrass, are its lower digestibility and voluntary intake. Mixtures of both species might combine the advantages of each, and species interactions may eventually lead to transgressive overyielding. We compared the agronomic performance of tall fescue, perennial ryegrass and tall fescue–perennial ryegrass mixtures, as pure‐grass swards or in association with white clover (Trifolium repens L.). Tall fescue–perennial ryegrass mixtures differed in the proportion and ploidy of the perennial ryegrass component. Yield, feed quality and botanical composition were measured in the 3 years after the sowing year. We found significant effects of ploidy of the ryegrass variety and of the proportion of ryegrass in the initial seed mixture on the botanical composition of the swards. Nevertheless, all swards were dominated by tall fescue at the end of the experiment. No overyielding of the mixtures compared with that of single‐species swards was found, but feed quality was intermediate between that of the single‐species swards. Mixed swards had better drought resistance than L. perenne and higher feeding quality than F. arundinacea swards.     

The effect of initial spring grazing date and subsequent stocking rate on the grazing management, grass dry matter intake and milk production of dairy cows in summer

The objective of this study was to investigate the effects of an early (February; F) or delayed (April; A) primary spring grazing date and two stocking rates, high (H) and medium (M), on the grazing management, dry matter (DM) intake of grass herbage and milk production of spring‐calving dairy cows grazing a perennial ryegrass sward in the subsequent summer. Sixty‐four Holstein‐Friesian dairy cows (mean of 58 d in milk) were assigned to one of four grazing treatments (n = 16) which were imposed from 12 April to 3 July 2004. Cows on the early spring‐grazing treatment were grazed at 5·5 cows ha^?1 (treatment FH) and 4·5 cows ha^?1 (treatment FM) while cows on the late‐grazing treatment were grazed at 6·4 cows ha^?1 (treatment AH) and 5·5 cows ha^?1 (treatment AM). The organic matter digestibility and crude protein concentration of the grass herbage were higher on the early‐grazing treatment than on the late‐grazing treatment. The cows on the FM treatment had significantly (P < 0·001) higher milk (24·5 kg), solids‐corrected milk (22·5 kg), fat (P < 0·01, 918 g) and protein (831 g) yields than the other three treatments. Cows on the FM treatment had a higher (P < 0·001) DM intake of grass herbage by 2·3 kg DM per cow per day than cows on the AH treatment, which had a DM intake significantly lower than all other treatments (15·2 kg DM per cow per day). The results of the present study showed that grazing in early spring has a positive effect on herbage quality in subsequent grazing rotations. The study also concluded that early spring‐grazed swards stocked at a medium stocking rate (4·5 cows ha^?1; FM) resulted in the highest DM intake of grass herbage and milk production.     

Impact of spatial heterogeneity of plant species on herbage productivity,herbage quality and ewe and lamb performance of continuously stocked,perennial ryegrass–white clover swards

The benefits of white clover (Trifolium repens L.) in pastures are widely recognized. However, white clover is perceived as being unreliable due to its typically low content and spatial and temporal variability in mixed (grass‐legume) pastures. One solution to increase the clover proportion and quality of herbage available to grazing animals may be to spatially separate clover from grass within the same field. In a field experiment, perennial ryegrass (Lolium perenne L.) and white clover were sown as a mixture and compared with alternating strips of ryegrass and clover (at 1·5 and 3 m widths), or in adjacent monocultures (strips of 18 m width within a 36‐m‐wide field). Pastures were stocked by ewes and lambs for three 10‐month grazing periods. Over the 3 years of the experiment, spatial separation of grass and clover, compared with a grass–clover mixture, increased clover herbage production, although its proportion in the sward declined through time (0·49–0·54 vs 0·34 in the mixture in the first year, 0·28–0·33 vs 0·15 in the second year and 0·03–0·18 vs 0·01 in the third year). Total herbage production in the growing season in the spatially separated treatments decreased from 11384 kg DM ha^?1 in the first year to 8150 kg DM ha^?1 in the third year. Crude protein concentration of clover and grass components in the 18‐m adjacent monoculture treatment was greater than the mixture treatment for both clover (310 vs 280 g kg^?1 DM) and grass (200 vs 180 g kg^?1 DM). There was no clear benefit in liveweight gain beyond the first year in response to spatially separating grass and clover into monocultures within the same field.     

Herbage dry‐matter production and forage quality of three legumes and four non‐leguminous forbs grown in single‐species stands

Agronomic data on most broad‐leaved species of grasslands are scarce. The aim of this study was to obtain novel information on herbage DM yield and forage quality for several forb species, and on species differences and seasonal patterns across harvests and in successive years. Four non‐leguminous forbs [salad burnet (Sanguisorba minor), caraway (Carum carvi), chicory (Cichorium intybus) and ribwort plantain (Plantago lanceolata)] and three leguminous forbs [yellow sweet clover (Melilotus officinalis), lucerne (Medicago sativa) and birdsfoot trefoil (Lotus corniculatus)] and a perennial ryegrass–white clover mixture were investigated in a small‐plot cutting trial in Denmark during 2009 and 2010. Plots were harvested four times per year. On average, annual herbage yield was highest for lucerne (15·4 t DM) and grass–white clover (12·5 t DM ha^?1), and lowest for salad burnet (4·6 t DM ha^?1) and yellow sweet clover (3·9 t DM ha^?1). Ribwort plantain and lucerne had the highest concentrations of acid detergent fibre (339 and 321 g kg^?1 DM respectively) and lignin (78 and 67 g kg^?1 DM respectively); contents in other species were similar to grass–white clover (275 and 49 g kg^?1 DM respectively). No common feature was found within the functional groups of non‐leguminous forbs and leguminous forbs, other than higher crude protein contents (198–206 g kg^?1 DM) in the legumes. DM yield and fibre content were lowest in October. Digestibility declined with higher temperature and increasing fibre content. Results are discussed in terms of the potential of forbs to contribute to forage resources in farming practice.     

The effect of applying cattle slurry using the trailing‐shoe technique on dairy cow and sward performance in a rotational grazing system

The effects of applying cattle slurry using the trailing‐shoe technique on dairy cow and sward performance were examined in two experiments in Northern Ireland. In Experiment 1, forty‐eight cows were allocated to two treatments, with or without slurry application. In Experiment 2, sixty cows were allocated to four treatments, a combination of high and normal grazing stocking rate, with or without slurry application. In Experiment 1, slurry was applied during the first and fourth rotations. In Experiment 2, slurry was applied prior to the first grazing rotation and during the second, fifth and sixth grazing rotations. In Experiments 1 and 2, the total inorganic fertilizer nitrogen (N) inputs applied within the slurry treatments were 200 and 133 kg N ha^?1, with 280 and 285 kg N ha^?1 used within the fertilizer‐only treatments in each experiment respectively. Varying responses of milk yield to slurry application were observed. In Experiment 1, with a normal stocking rate, no effect was observed. In Experiment 2 with two stocking rates, reduced milk yields were observed at both stocking rates. Although not significant, there were indications that this reduction in milk yield when slurry was applied was higher at higher stocking rates.