Forage Mixtures Research Articles

The effect of the replacement of grass silage by increasing proportions of urea-treated whole-crop wheat on food intake and apparent digestibility and milk production by dairy cows

AbstractSix Holstein-Friesian cows in mid lactation were used to examine the effects of replacing increasing proportions of grass silage (GS) by whole-crop wheat (WCW) in the diet of lactating dairy cows. Grass silage was a first-cut perennial ryegrass. The WCW was harvested at 645 g dry matter (DM) per kg and was preserved with either 20 (WCW-20) or 40 (WCW-40) kg urea per t DM. The diets were 6 kg DM dairy concentrate daily with one of six forage treatments offered ad libitum. The forage treatments were GS alone, GS with either WCW-20 or WCW-40 in a 2:1 DM ratio, GS with either WCW-20 or WCW-40 in a 1:2 DM ratio, or WCW-40 alone. The experiment consisted of an incomplete change-over design with three 4-week periods. DM intakes were highest with the mixtures (P < 0·05) but milk yield was not significantly affected by the treatments although it tended to be highest with the 1:2 ratio. Milk composition responses were generally small and non-significant, but yields of fat and protein were highest with the mixtures (P < 0·05). The apparent digestibility of DM and organic matter (OM) decreased linearly (P · 0·01) with increasing WCW inclusion but digestible DM and OM intakes were not significantly affected. Apparent digestibility of neutral-detergent fibre tended to be lower with the forage mixtures (quadratic P < 0·20). Apparent digestibility of starch was higher with GS than with diets containing WCW and decreased linearly with diets containing increasing proportions of WCW (P < 0·01). Intakes of starch and digestible starch rose with increasing WCW inclusion but so also did faecal starch output such that 0·75 kg starch per day was excreted on WCW-40 alone. Water intake from food and water excretion in urine decreased linearly with increasing WCW inclusion but water excretion in faeces and milk was not significantly affected by diet. The difference between measured water intake and output (water deficit) increased from 38 kg/day on GS alone to 58 kg/day on WCW-40 alone (linear P < 0·001). The only effects of level of urea treatment were to increase milk urea concentration (P < 0·05). It is concluded that the small size of the milk yield response to the increased forage intake obtained when up to two-thirds of the GS is replaced by WCW is due to the reduced digestibility of the OM and particularly of the starch component resulting from the egestion of whole wheat grains in the faeces.

Mixtures of Persian clover with Italian ryegrass or barley-Italian ryegrass for annual forage

In the interior of British Columbia, spring barley (Hordeum vulgare L.) and Italian ryegrass (Lolium multiflorum var. italicum Beck.) are intercropped with fertilizer N as a 1-yr break before reseeding irrigated alfalfa (Medicago sativa L.). Persian clover (Trifolium resupinatum L.) was seeded with barley and ryegrass or only ryegrass to determine its effect on seasonal yield and forage nutritive value. All species mixtures were grown with and without a total of 200 kg ha−1 of N to compare N2 fixation by Persian clover with N fertilizer. Averaged over 2 yr, adding Persian clover to barley-ryegrass provided a total yield that was 96% of that obtained by adding fertilizer N to barley-ryegrass. Second cut yield averaged 58% more with clover than with N. However, the grasses yielded more than the grasses with added clover in the third cut. Adding clover to ryegrass provided 94% of the total yield of adding N fertilizer. Persian clover was higher in crude protein and in vitro digestibility of dry matter than ryegrass, so adding clover tended to improve the nutritive value of mixtures. This was most obvious without N, where Persian clover accounted for more of the total forage produced. The study shows that Persian clover is a valuable addition to barley-ryegrass mixtures; it reduces fertilizer needs, improves mid-season yield and improves forage nutritive value. Key words: Persian clover, barley, Italian ryegrass, forage mixtures

Establishment, Development and Yield of Forage Legumes and Grasses as Cover Crops in Grain Corn in Eastern Canada

AbstractInterseeded cover crops can minimize soil erosion, increase organic matter and nutrient levels and the yield of subsequent crops. However, their performance is very sensitive to local conditions. Field experiments were conducted at two Quebec locations in 1993 and 1994 in order to evaluate the potential use of forage legumes and grasses as interseeds in corn in eastern Canada. Twelve forage species were evaluated. Fall rye (Secale cereal L.), hairy vetch (Vicia villosa Roth), a mixture of red clover (Trifolium pratense L.) and ryegrass (Lolium multiflorum Lam), a mixture of white clover (Trifolium repens L.) and ryegrass, subterranean clover (Trifolium subterraneum L.), yellow sweet clover (Melilotus officinalis Lam.), black medic (Medicago lupulina L.), Persian clover (Trifolium resupinatum L.), strawberry clover (Trifolium fragiferum L.), crimson clover (Trifolium incarnatum L.), annual alfalfa (Medicago saliva L.) and berseem clover (Trifolium alexandrinum L.) were seeded at two planting dates (10 and 20 days after corn emergence). The control treatments were: hand weeding, chemical weeding and non‐weeded. Early seeded forages established better and had higher biomass accumulation than the late seeded ones. In the presence of larger weed populations, the interseeded forages did not develop well due to competition with the weeds. At Macdonald crimson clover provided good soil cover while Persian clover, fall rye and alfalfa provided relatively little cover. Strawberry clover and hairy vetch did not provide early ground cover due to their late development. Forage mixtures of red or white clover and rye grass established well and achieved high populations at the end of the growing season. Fall rye provided good early ground cover but senesced by the middle of the season. The better establishment and early germination of crimson clover caused a 19% reduction in corn grain yield in 1993. In 1994 none of the cover crops caused a reduction in corn yield.

Effect of concentrate type on forage intake and milk production of dairy cows offered mixed forage diets based on maize and grass silage

Earlier studies at CEDAR established the positive effects on intake and milk production when forages other than grass were incorporated into dairy cows rations. The area of forage maize and its integration in UK dairy rations continues to increase and as a result has generated considerable interest in supplementation of diets based on maize (MS) and grass silage (GS). The aim of the current study was to determine the effect of using starch (S) and fibre (F) based concentrates on feed intake and milk production of Friesian cows offered a forage mixture of MS and GS in a 3:1 DM ratio.Forty individually fed multiparous Friesian cows were used in a continuous design study. At week 3 of lactation cows were allocated to one of four treatment groups (Table 1), in which all cows were offered ad libitum access to a forage mixture containing on a DM basis 750 g/kg MS and 250 g/kg GS and 10 kg fresh weight/d of either a starch (229 g starch and 58 g NDF kg/DM) or fibre (85 g starch and 124 g NDF/kg DM) based concentrate. Both concentrates contained 237 g CP and 13.1MJ ME/kg DM and were offered twice dairy in equal quantities.

Carbon Dioxide and Ozone Effects on Growth of a Legume‐Grass Mixture

AbstractAtmospheric carbon dioxide (CO2) and photochemical ozone (O3) have been increasing in the biosphere and will continue to do so with further industrialization and burning of fossil fuels. The purpose of this study was to examine the interaction of CO2 and O3 on plant growth and aboveground competition using a forage mixture of alfalfa (Medicago sativa L.) and timothy (Phleum pratense L.). Mixtures were grown at two CO2 levels (350 and 700 µL/L) in controlled environment chambers and exposed to four weekly O3 episodes of 8‐h duration with peak daily concentrations of 0.03, 0.08, 0.13, or 0.18 µL/L on Days (d) 21, 28, 35, and 42 after seeding. Roots of individual plants were in separate containers. The plants were harvested 2 d after the final O3 exposure. Total dry biomass of alfalfa and timothy was 50 and 40%, respectively, greater at 700 than at 350 µL CO2/L with low O3. Increasing peak O3 concentration decreased alfalfa shoot dry biomass at 700 µL CO2/L but not at 350 µL/L and decreased root dry biomass at both CO2 levels. In timothy, intermediate O3 levels reduced shoot growth but the highest level of O3 resulted in more shoot growth in the mixture at both CO2 levels. Partitioning of dry matter to alfalfa roots was strongly retarded by increasing O3, particularly in the CO2‐enriched environment, while timothy root growth was unaffected by O3. The enhancement of timothy shoot biomass in the mixture by exposure to the highest level of O3 at either CO2 level could not be fully explained by changes in competition between timothy and alfalfa in relation to differential O3 tolerance.

Use of bovine somatotropin for milk production: the effect of time of treatment initiation on milk production of Holstein/Friesian dairy cows placed on a high‐forage, low‐concentrate feeding system

AbstractSixty multiparous Holstein/Friesian cows were used in a 2 × 2 factorial design trial to determine the effect of the administration of bovine somatotropin (BST), at either 60 or 120 ± 3 d post partum, on milk production. All cows were offered ad libitum a forage mixture containing, on a dry‐mailer (DM) basis, grass and maize silage in a 1:1 ratio and 4 kg d−1 fresh weight of concentrate, which contained 115 and 495 g kg−1 DM of neutral detergent fibre (NDF) and crude protein (CP), respectively, and 13–5 MJ kg−1 DM metabolizable energy (ME). BST‐treated cows received subcutaneous injections of a prolonged‐release formulation of BST (sometribove). Injections were administered into the ischiorectal fossa at 14‐d intervals for the remainder of the lactation. This schedule resulted in sixteen and twelve injections cow−1 when treatment w as in it rate d at 60 and 120 + 3 d post partum respectively. This corresponded to treatment periods of 32 and 24 weeks, in which the production responses were measured. When compared with control cows, the administration of BST from 60 and 120 ± 3 d post partum increased mean milk yield by 1–2 and 3.3 kg day−1 respectively, although only the latter milk‐yield response was significant (P <0.001). The administration of BST produced a small nonsignificant increase in DM intake, no effect on milk composition and a small but significant reduction in body condition In conclusion a significant milk‐yield response can be obtained from the use of BST in high‐forage, low‐concentrate feeding systems if forage quality is high and treatment initiation is delayed until mid‐lactation. This is illustrated by the fact that the lactation yield increased from 6054 to 6842 kg. and was obtained when using only 1.2 t of concentrate.

Legume-cereal forage mixtures for silage 1. Effect of pea variety, maturity and sowing density of mixture on dry matter yield and silage chemical composition

Legume-cereal forage mixtures for silage 1. Effect of pea variety, maturity and sowing density of mixture on dry matter yield and silage chemical composition

Adaptation of winter cereal species to shade and competition in a winter/spring cereal forage mixture

Spring planted mixtures of spring and winter cereals maximize dry matter yield and provide fall pasture by regrowth of the winter cereal. However, delay of initial harvest may reduce the winter cereal component and therefore subsequent regrowth yield. Research was conducted at Lacombe, Alberta to investigate the effect of time of initial cut (stage), winter cereal species (species) and cropping system (monocrop and mixture) on winter cereal shoot weight, leaf carbon exchange efficiency and shoot morphology. These parameters may be related to adaptation of winter cereals to growth and survival in the mixture. Winter cereal plants were grown in pails embedded in monocrop plots of fall rye (Secale cereale L.), winter triticale (X Triticosecale Wittmack) and winter wheat (Triticum aestivum L.) and in binary mixtures with Leduc barley (Hordeum vulgare L.). The plants were removed when the barley reached the boot (B), heads emerged (H), H + 2, H + 4 and H + 6 wk stages. Shoot weight was generally smaller in the mixture than in the monocrop and wheat was reduced more than fall rye and triticale in the mixture compared to the monocrop. Dark respiration rate (r = −0.54) and carbon exchange (r = 0.36) under low light intensity were correlated (P < 0.05) to shoot size in the mixture. Fall rye and winter triticale had lower dark respiration rates than winter wheat. Leaf area index (LAI) was closely correlated (r = 0.83 and 0.84) with shoot weight in both the mixture and monocrop. While species failed to exhibit clear cut differences for LAI, fall rye and winter triticale were reduced less than winter wheat in the mixture relative to the monocrop. Stage was the dominant factor affecting winter cereal growth in both cropping systems, but fall rye and triticale exhibited superior morphological features, and their carbon exchange responses to light were more efficient than wheat, which should allow them to be sustained longer under the shaded conditions of a mixture. Key words: Delayed harvest, shade, spring and winter cereal mixtures, adaptation, carbon exchange, respiration

Digestibility of diets of grass silage and whole crop wheat in the rumen of lactating cows

Forage mixtures containing urea-treated whole crop wheat (WCW) have been shown to be used less efficiently than expected by dairy cows due to low digestibility, particularly of the starch. The purpose of the present experiment was to measure the contribution of the rumen to the digestibility of diets based on grass silage or mixtures of grass silage and urea-treated WCW.

Digestibility of diets of grass silage and whole crop wheat in the rumen of lactating cows

Forage mixtures containing urea-treated whole crop wheat (WCW) have been shown to be used less efficiently than expected by dairy cows due to low digestibility, particularly of the starch. The purpose of the present experiment was to measure the contribution of the rumen to the digestibility of diets based on grass silage or mixtures of grass silage and urea-treated WCW.

The effect of concentrate level on feed intake and milk production of dairy cows offered mixed forage diets

The increasing interest in the potential of forage mixtures for milk production in the UK resulted in a three year study being commissioned at the Centre for Dairy Research by the Milk Marketing Board. Year 1 compared the effect on forage intake and yield of milk and milk constituents of replacing grass silage (GS) with either fodder beet (FB), urea-treated (4%) (UW) or fermented whole-crop wheat (FW) or brewers grains (BG) at 330 g/kg of forage DM or maize silage at either 330 (MS) or 750 (MSH) g/kg forage DM. All cows received 6 kg DM/day of an appropriate concentrate so that dietary crude protein (CP) was equalised. Tire use of forage mixtures significantly increased DM intake and milk yield. Significant changes were also recorded in milk quality. Milk fat content was depressed by BG and MSH but increased by FB, while MS and FB increased milk protein content when compared with GS. The aim of the current study was to determine the effect of concentrate level on feed intake and milk production of Friesian cows offered a forage ration of either GS or mixtures of GS and either 330 g/kg forage DM of MS, FB or BG, or 750 g/kg forage DM of maize silage (MSH).

The effect of concentrate level on feed intake and milk production of dairy cows offered mixed forage diets

The increasing interest in the potential of forage mixtures for milk production in the UK resulted in a three year study being commissioned at the Centre for Dairy Research by the Milk Marketing Board. Year 1 compared the effect on forage intake and yield of milk and milk constituents of replacing grass silage (GS) with either fodder beet (FB), urea-treated (4%) (UW) or fermented whole-crop wheat (FW) or brewers grains (BG) at 330 g/kg of forage DM or maize silage at either 330 (MS) or 750 (MSH) g/kg forage DM. All cows received 6 kg DM/day of an appropriate concentrate so that dietary crude protein (CP) was equalised. Tire use of forage mixtures significantly increased DM intake and milk yield. Significant changes were also recorded in milk quality. Milk fat content was depressed by BG and MSH but increased by FB, while MS and FB increased milk protein content when compared with GS. The aim of the current study was to determine the effect of concentrate level on feed intake and milk production of Friesian cows offered a forage ration of either GS or mixtures of GS and either 330 g/kg forage DM of MS, FB or BG, or 750 g/kg forage DM of maize silage (MSH).

Forage mixtures for dairy cows: the effect on dry-matter intake and milk production of incorporating either fermented or urea-treated whole-crop wheat, brewers' grains, fodder beet or maize silage into diets based on grass silage

AbstractOne hundred and two multiparous Holstein/Friesian dairy coivs were used to examine the effect on food intake and milk production of replacing 330 g/kg dry matter (DM) of first-cut perennial ryegrass silage (GS) with either fermented (FW) or urea (40 g/kg DM) treated (UW) whole-crop wheat, brewers' grains (BG), fodder beet (FB) or maize silage (MS). A forage mixture containing GS and 750 g/kg DM of maize silage (MSH) was also offered. Dietary crude protein (CP) concentrations were equalized by offering all cows 6 kg DM per day of an appropriate concentrate supplement. DM intake and milk yield of cows offered GS (15·3, 23·0 kg/day) were increased (F < 0·01) by the inclusion of BG (16·3, 26·7 kg/day), FB (17·6, 25·9 kg/day), MS (16·6, 26·4 kg/day) and MSH (18·5, 27·6 kg/day). BG, FB and MS all produced similar increases in milk yield. Although the inclusion of FW and UW increased (F < 0·05) DM intake, milk yield was not significantly affected. The differences between the highest and lowest milk fat concentration, produced by FB (42·9 g/kg) and BG (40·1 g/kg) respectively, and the highest and lowest milk protein concentration produced by FB (32·1 g/kg) and GS (29·9 g/kg) respectively, were statistically significant (F < 0·001). Milk fat and protein yields of cows offered GS (0·97, 0·71 kg/day) were increased (F < 0·01) by BG (1·07, 0·82 kg/day), FB (1·11, 0·83 kg/day), MS (1·11, 0·83 kg/day) and MSH (1·12, 0·88 kg/day). Intermediate values were recorded for FW (1·01, 0·72 kg/day) or UW (1·00, 0·73 kg/day). Results show that farmers should consider replacing a major part of the grass silage component with an alternative forage or forage substitute.

Potato Leafhopper Management: Effects on Production and Quality of Alfalfa‐Timothy Mixtures

AbstractAlfalfa (Medicago sativa L.) mixtures with grasses, especially timothy (Phleum pratense L.), are widely planted in the Great Lakes Region, but most information on potato leafhopper [Empoasca fabae (Harris)] (PLH) management for new stands is based on alfalfa monocultures. Field research was conducted in 1991 and 1992 to evaluate the ability of alfalfa to recover from PLH injury following insecticide application and to compare the effect of injury on yield and quality of first‐year monocultures or mixtures. Four replicates of alfalfa monoculture and alfalfa‐timothy mixtures were established each year. One week after the first harvest in early July, eight split‐plot treatments were established in each main plot: an uncaged check, a caged check, and six combinations of two PLH infestation densities (25 or 50 PLH adults m−2) and three insecticide application dates (1 wk after infesting plots, 3 wk after infesting plots, and unsprayed). Crop mixture had no effect on PLH nymphal populations on a per stem basis. Although differences between years were noted, delaying insecticide application generally reduced forage yield and quality, delayed crop maturity, and increased weed content, particularly in forage mixtures. There was little evidence that seedling timothy could compensate for PLH injury to alfalfa. Data on stem elongation and dry matter accumulation indicated that alfalfa can recover from leafhopper injury; however, dry matter production did not increase for at least 2 to 3 wk following a spray application. Reductions in forage crude protein due to PLH injury were a result of both reduced crude protein content in the alfalfa and an increase in the proportion of weed biomass in the forage. Early detection and rapid response to economically significant populations are necessary to realize the greatest benefit from treatment. The presence of timothy in the mixture does not alter PLH management recommendations for new stands.

Estimating forage yield and quality changes during field drying for hay. 2. Model of forage drying

A forage drying submodel (HayDry) has been developed for use in an operational model of weather-induced forage quality losses during field drying for hay. HayDry simulates changes in bulk swath forage moisture content during field drying periods that may or may not be prolonged by rain. Model inputs are hourly solar irradiance (or net radiation), air temperature and humidity, wind speed and rainfall. Forage drying is estimated by the Penman-Monteith combination equation, with canopy resistance estimated as an empirical function of surface water, forage moisture content and forage dry-matter yield. Forage wetting and rehydration are estimated by a distributed rewetting submodel. HayDry was developed and validated in three steps: (1) a sensitivity analysis identified key model parameters; (2) established values for key parameters were evaluated by comparing the simulated forage moisture contents with field measurements during two rain-free and two prolonged drying periods; (3) the model was independently validated during a third prolonged drying period and at a second site. The simulated changes in forage moisture matched closely the measured sequence of drying, rewetting by dew and rewetting by rain, for forage mixtures that were predominantly alfalfa. The mean forage moisture content during drying was simulated to within 20% during rain-free and prolonged drying periods at both sites.

Estimating forage yield and quality changes during field drying for hay 1. Model of dry-matter and quality losses

Wet, humid weather during field drying causes forage yield and quality changes and reduces feeding value. A model has been developed to estimate forage quality at cutting and the losses of forage dry matter and quality during field drying. Hourly climate inputs include air temperature, humidity, rainfall, wind speed and solar or net radiation. The model simulates changes in forage quality components (acid detergent fibre, neutral detergent fibre and crude protein) and dry-matter constituents (cellulose and lignin, hemicellulose, crude protein and non-protein cell contents) by post-cutting plant respiration, leaching, microbial activity and tedding leaf loss. The model was validated in the field over three seasons and at two sites for a forage mixture of mostly alfalfa (lucerne) and timothy. Changes in total dry matter and its constituents were calculated from the measured changes in quality components. Comparison of simulated and measured changes were made for total losses and cumulative changes during each drying period. The simulated total dry-matter losses were within the error limits of measurement for three of four rain-free and four of six prolonged drying periods. Calculated and simulated dry-matter losses and quality changes were near zero during rain-free periods. In prolonged drying periods, simulated plant respiration and leaching accounted for 72% and 5%, respectively, of the mean calculated dry-matter loss of 209 g kg-1. The mean calculated crude protein loss during prolonged drying periods (46 g kg -1) agreed closely with that simulated (40 g kg-1) when crude protein was assumed to be half as susceptible to loss by respiration and leaching as non-protein cell contents. An initial estimate of microbial activity was added to the model, to eliminate the discrepancy between calculated and simulated dry-matter losses. Further research is required to assess and improve the simulation of plant respiration, microbial activity and tedding losses, to extend the conditions for leaching, and to simulate swath microclimates.

Weed Control and Herbicide Tolerance in a Common Vetch-Oat Intercrop

Field studies were conducted over 3 yr in central Spain to investigate the tolerance of common vetch and oat to some preemergence herbicides and their effects on weed control, forage yields, and botanical composition of the forage mixture. Pendimethalin was the only herbicide that injured common vetch. Pronamide and pronamide plus diuron injured oat by affecting plant emergence. Prevalent weed species were fumitory, henbit, and wild buckwheat. All herbicides provided more than 90% control of fumitory and most herbicides except pronamide provided more than 90% control of henbit relative to the untreated check. Wild buckwheat stands were reduced by isoxaben (68%), linuron (40%), prometryn (69%), pronamide (86%), and pronamide plus diuron (61%). More than 90% control of prostrate knotweed was achieved with isoxaben, pronamide, and terbutryn. Pronamide and pronamide plus diuron reduced forage yields and increased vetch in the forage. The untreated vetch and oat monocrop treatments showed the competitive advantage of oat over vetch and weedy species.

Light interception and partitioning in a shrub/grass mixture

When crops are grown in mixture systems, microclimate is modified, particularly the light regime. Experiments were conducted in Guadeloupe to examine the variability of the light field and test a light interception model in a traditional forage mixture made of angleton grass savanna planted with rows of gliricidia shrubs. Simulated figures of reflected, transmitted and absorbed PAR were in close agreement with experimental data measurements during the four periods of the study. The model was also used to simulate the influence of row orientation (N-S or E-W), location (North Tropic or Equator), and dates (winter solstice, equinox or summer solstice) on the absorbed photosynthetically active radiation (PAR). The presence of the shrubs strongly decreased the absorbance of the grass, which absorbed between 42% and 50% and 14% and 19%, respectively, in pure and mixed stands. Light capture by gliricidia ranged between 51% and 66%, and was not affected by the presence of the grass. In all cases the interception of the PAR was better for the mixed crop (+15% and +30% more than the pure shrubs and the pure grass, respectively). The influence of the non-photosynthetic organs of the shrubs was limited (about 2%). A simple version of the model is presented, based on a modification of the extinction coefficient instead of the complete calculation of scattering. Differences between the two models are small. Results suggest that the effect of row orientation and season in this kind of perennial forage mixtures is limited.

Competition for light and nitrogen during a regrowth cycle in a tropical forage mixture

Abstract A dynamic analysis of light and nitrogen sharing in a grass/legume mixture during a regrowth cycle in a humid tropical climate is presented. Pure stands and mixture plots of two stoloniferous species, Arachis pintoi (a C3 legume species) and Digitaria decumbens (a C4 grass species), were established on ferralitic soil in randomised sub-plots with four replicates. Each crop was fertilised at two different nitrogen levels: 150 (N150) and 0 (N0) kg of nitrogen per hectare. Growth was analysed in terms of radiation-use efficiency (RUE) of photosynthetically active radiation (PAR) absorbed by crops. Daily absorption efficiencies of the mixture's components were estimated by a radiative-exchange model. The results demonstrated that presence of the legume reduced light interception by the grass by 13 and 28% under the N150 and N0 conditions respectively. On the other hand, competition by D. decumbens for light was very strong at both nitrogen levels since it reduced interception of incident PAR by A. pintoi by 69% (N0) and 91% (N150) in the growth cycle. Intercropping did not result in changes in the radiation-use efficiency of either species except in N150 mixed crop where A. pintoi virtually disappeared due to zero radiation interception at the end of the cycle. Uptake of nitrogen by the grass was not affected by presence of the legume. Despite different production potentials of C3 and C4 species, under N0 mixed-crop conditions, behaviour was neutral. Consequently, the mixture could be maintained at equilibrium if sward production is not intensified by nitrogen fertilisation.

Factors influencing pasture productivity in Atlantic Canada

Most pastures in Atlantic Canada are classified as permanent and contain primarily native species. Well-managed native swards have the potential of supporting profitable animal output. Productive cultivars of cool-season perennial grass species such as timothy (Phleum pratense L.), orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), reed canarygrass (Phalaris arundinacea L.) and legumes such as white clover can increase pasture productivity in the region and ameliorate seasonal fluctuations in dry matter yield associated with native swards. Improved swards gradually revert to native species, partly because forage cultivars and mixtures are not assessed for persistence under grazing.Soil acidity and deficiencies in soil nutrients were shown to reduce herbage yield, legume content of the grazed swards and mineral content of the herbage, all of which may adversely affect livestock performance. High concentrations of K, observed in swards heavily fertilized with N, are likely to cause problems in the metabolism of Ca and Mg in lactating ruminant livestock grazing such swards.Supplemental pasture crops, including annual ryegrass (Lolium multiflorum Lam.) and Brassica species, extend the productive grazing season from approximately 4 to 7 mo, and permit the production of large quantities of biomass close to the barn.Rotational grazing and forward creep-grazing techniques at high stocking rates can improve the number of animal grazing days and average daily gains. Previous experience with grazing and exposure to pasture species before and during weaning appear to influence grazing behavior and species preference of newly weaned livestock. The use of previous grazing experience may help create the desired pasture sward or improve the efficiency of sward utilization by the grazing animal. The high rainfall climate of the Atlantic region, which promotes good herbage production, also encourages heavy and prolonged infestations of infective free-living stages of gastrointestinal parasites on pastures. Permanent pasture is the main source of initial herd infection, which then spreads to newly seeded pastures. Strategic treatments of grazing livestock with anthelmintic drugs are recommended to minimize the impact of these parasites on the productivity of grazing livestock in this region. Key words: Pasture, Atlantic Canada, productivity, grazing management, fertility management, Brassica spp., grasses, legumes