Cultivated forage crops are grown on almost 12 million ha on the northern Great Plains. This paper reviews the benefits of diversifying annual crop rotations with forage crops and highlights innovations in forage systems. Agronomic benefits of rotating forage crops with annual grain crops include higher grain crop yields following forages (up to 13 yr in one study), shifts in the weed population away from arable crop weeds, and improved soil quality. Perennial legumes in rotation also reduce energy requirements by adding significant amounts of N to the soil. Soil water availability may limit the extent to which forages benefit following crops. Under semiarid conditions, forages can actually reduce yields of the following crops, and as such, tillage practices that conserve soil water have been developed to partially address this problem. Forages in rotation provide environmental benefits, such as C sequestration, critical habitat for wildlife, and reduced NO3 leaching. A wider range of annual plant species are now used in forage systems in an effort to extend the grazing season and to maximize use of water resources. Intensive pasture management using cultivated forages is on the increase as is the use of alfalfa (Medicago sativa L.) in grazing systems; in some cases, bloat‐reduced alfalfa cultivars are used. Pasture‐based systems appear to provide benefits for both animal and human health and arguably the health of the environment. Pasture systems are less nutrient exhausting than hay systems. As a result, nutrient management strategies will differ in the following crop. Additional research is required to optimize the role of cultivated pastures in grain‐based cropping systems.

. Impact of pasture type on methane production by lactating beef cows. Can. J. Anim. Sci. 79: 221-226. In order to determine the quantity of methane (CH 4 ) produced by lactating beef cows on pasture, 16 Hereford-Simmental first-calf heifers with a mean weight of 511.2 ± 5.8 kg were randomly selected from a larger group of cows (n = 60) on a grazing management experiment and used to evaluate the effects of pasture type on ruminal CH 4 production using the sulfur hexafluoride (SF 6 ) tracer-gas technique. Pasture treatments consisted of two pasture types, alfalfa-grass [78% alfalfa (Medicago sativa L.) -22% meadow bromegrass (Bromus biebersteinii Roem and Schult.)] or 100% meadow bromegrass at each of two fertility levels (either unfertilized or soil test recommended fertilizer levels) with two replications of each pasture treatment (8 pastures). Cows were managed using a "put and take" stocking system to leave equal residual herbage mass on all treatments following the grazing period in each paddock. During the 69-d grazing season, two cows from each pasture were sampled to determine daily forage intake and CH 4 production on four occasions. The chemical composition of diets differed between pasture types and sampling periods. Dry matter intake was greater for cows grazing alfalfa-grass pastures than for cows grazing grass-only pastures (11.4 vs. 9.7 kg DM d -1 ; P < 0.018). However, methane production was greater for cows grazing alfalfa-grass pastures than for cows grazing grass-only pastures (373.8 vs. 411.0 L CH 4 d -1 ; P < 0.008). Consequently, energy lost through eructation of CH 4 was less for cows grazing alfalfa-grass pastures than it was for cows grazing grass-only pastures (7.1 vs. 9.5% of GEI; P < 0.001). Hereford-Simmental primipares en lactation, pesant en moyenne 511,2 ± 5,8 kg, ont été prises au hasard dans une plus grande population de vaches (n = 60) pour participer à une expérience de conduite du pâturage. L'objet était d'évaluer les effets de la composition du pâturage sur la production ruminale de CH 4 au moyen de la technique au gaz traceur hexafluorure de soufre (FS6). Deux types de pâturage étaient comparés, 1 peuplement pur de brome des prés (Bromus biebersteinii Roem & Schult.) et un mélange à 78 % luzerne (Medicago sativa L.) et 22 % brome des prés, chacun à deux niveaux de fertilité, sans fumure et fumure recommandée selon l'analyse du sol. Chaque traitement comportait 2 répétitions. Le chargement animal adopté était du type variable, de façon à laisser une même masse herbagère résiduelle dans tous les traitements au terme de la période de pâturage. Durant cette période de 79 jours, deux vaches de chaque enclos étaient utilisées à 4 reprises pour déterminer l'ingestion quotidienne d'herbe et la production de CH 4 . La composition chimique du fourrage différait selon la nature du pâturage et selon la date des prélèvements. L'ingéré de m.s. était plus abondant chez les vaches pâturant l'association luzerne-graminée que chez celles broutant le peuplement pur de graminée (11,4 contre 9,7...

Results from two decades (1973-1993) of bloat research at Kamloops are reviewed. The trials were conducted with groups of ruminally fistulated cattle either grazing or fed daily fresh-cut alfalfa (Medicago sativa) herbage. Studies were conducted during the growing season (May to September) and in the fall (October and November). The alfalfa was usually in the vegetative to early bloom stages of growth. Visual assessments of bloat severity on a scale of 1 to 5 were made .5 to 2 h after feeding started, at which time ruminal cannulas were opened to relieve ruminal pressure. Every cultivar of alfalfa tested caused bloat, but sainfoin (Onobrychis viciifolia), birdsfoot trefoil (Lotus corniculatus), and cicer milkvetch (Astragalus cicer) did not. This confirms the bloat-safe features of these alternate legume forages. Bloat was positively associated with the level of Fraction 1 protein and total soluble protein in alfalfa, supporting the concept of a decreased probability of bloat with advancing stages of plant maturity. There was no association between alfalfa saponins and bloat. Prefeeding ruminal chlorophyll levels were higher and ruminal clearance rates were lower in cattle that were susceptible to bloat. Cattle that bloated on a given day consumed 18 to 25% less alfalfa immediately before bloat than non-bloaters did in the same time period. Ruminal cations were associated with bloat incidence but cation manipulation through supplementation did not prevent bloat. Of all the feed additives tested, only poloxalene (Bloat Guard) completely prevented bloat.(ABSTRACT TRUNCATED AT 250 WORDS)

Composting of livestock manure is an effective method for managing the nutrients for agronomic purposes and reducing environmental and human health risks. Capability to analyze the biowastes on-site at the start of, periodically during, and at the end of composting could facilitate managing the composting process and increase the value of the end products. Near-infrared spectroscopy (NIRS) is well known for its capability to analyze organic substances rapidly and cost-effectively. This study was conducted to explore the capability of a field-portable NIR spectrometer to determine nutrient composition of beef feedlot manure when raw, stockpiled (not turned), and composted (windrowed and turned). Over a 2-yr period, beef feedlot manure mixed with bedding (wheat straw) was sampled annually at cleanout, after storage for some months in a large stockpile, and from windrows subjected to active thermophilic composting. Samples were dried and ground and scanned with the field-portable Corona 45 VIS NIR (visible/near-infrared) spectrometer (Carl Zeiss, Germany) from 360 to 1690 nm. NIRS was found useful in two ways. Classification analysis (Soft Independent Modeling of Class Analogy [SIMCA]) using the spectral data alone showed that stockpiling the manure did not change in composition significantly whereas compost was

to determine the quantity of methane (CH 4 ) produced by steers on pasture, 16 steers with a mean weight of 356 ± 25 kg were randomly selected from a larger group of cattle (n = 48) to evaluate the effects of grazing management and monensin controlled release capsule (CRC) administration on ruminal CH 4 production using the sulphur hexafluoride (SF 6 ) tracer-gas technique. Pasture management treatments consisted of two grazing systems (continuous stocking or 10-paddock rotational stocking) at each of two stocking rates (low, 1.1 steer ha -1 or high, 2.2 steers ha -1 ) with two replications of each pasture treatment. Half of the animals on each pasture treatment were administered a monensin CRC delivering 270 mg d -1 , and untreated animals served as controls. During the 140-d grazing season, one steer from each treatment-replicate combination was sampled to determine daily intake and CH 4 production on four occasions. The chemical composition of diets differed between grazing management treatments and sampling periods. Voluntary intake and CH 4 production, adjusted for differences in body weight, were unaffected by grazing management, sampling period or by monensin CRC administration and averaged 0.69 ± 0.1 L kg BW -1 d -1 across all grazing management treatments. The energy lost through eructation of CH 4 averaged 4.5 ± 1.4% of gross energy intake.

. 2000. Development and evaluation of grazing-tolerant alfalfa cultivars: A review. Can. J. Plant Sci. 80: 503-512. Plant breeders have long sought to improve grazing tolerance of alfalfa without sacrificing the beneficial yield and quality attributes of this species. Most efforts have focussed on selecting for traits (e.g., creeping rootedness) related to grazing tolerance and/or simulated grazing, but these efforts failed to account for the multiple stresses caused by grazing animals. Trait selection often led to sacrifices in yield and other desirable characteristics resulting in cultivars that were not robust across grazing management systems and environments. An innovative selection procedure was recently developed at the University of Georgia which incorporated intensive grazing with continuous stocking by beef cattle. The development of "Alfagraze" using this procedure showed that grazing tolerance and high yields can be incorporated into the same cultivar, along with consistent performance across grazing management systems and environments. Subsequent research has shown that grazing tolerance can be improved within elite, high-yielding, multiple-pest-resistant cultivars and breeding populations. Selection using intensive grazing with continuous stocking has been summarised in a "Standard Test Protocol" that is now being successfully used by public and private alfalfa breeders and in cultivar evaluation programs in the USA, Canada, and other countries. Les sélectionneurs cherchent depuis longtemps à améliorer la tolérance de la luzerne au pâturage, sans compromettre le rendement quantitatif et qualitatif de l'espèce. On s'est essentiellement attaché jusqu'ici à la recherche de caractères particuliers, p. ex. l'enracinement traçant, liés à la tolérance au pâturage ou à la paissance simulée, mais cela n'a pas été suffisant pour contrer les multiples stress causés par les animaux à l'herbe. La sélection axée sur un caractère particulier s'est souvent faite aux dépens des autres caractères désirables, notamment le rendement, ce qui a produit des cultivars ne pouvant persister que dans certains systèmes pastoraux et dans certains milieux de culture. Une technique de sélection originale a été mise au point dernièrement à l'Université de Géorgie (E.U), qui incorpore le pâturage intensif sous à chargement animal continu par des bovins à viande. L'obtention du cultivar Alfagraze par cette méthode démontre que tolérance au pâturage et rendement élevé peuvent être réunis dans un même cultivar, lui assurant ainsi des performances stables, indépendamment du système pastoral utilisé ou des conditions du milieu. Des recherches subséquentes ont montré qu'il est possible d'améliorer la tolérance à la pâture dans des cultivars ou des populations de sélection à haut rendement et à large spectre de résistance aux maladies. La nouvelle méthode, normalisée dans un protocole expérimental standard, est aujourd'hui utilisé avec succès par les sélectionneurs de luzerne, tant privés que ceux du secteur public, ainsi que dans les pr...

, W. 2000. Enhancing pasture productivity with alfalfa: A review. Can. J. Plant Sci. 80: 513-519. Alfalfa has been recognized for its superior yield and quality in seeded pastures. However, when grazing immature alfalfa there is a risk of animal losses due to frothy bloat in some ruminant livestock. Inclusion of at least 50% grass in the pasture mixture is commonly recommended to reduce the risk of bloat. Two decades of plant breeding have resulted in the release of AC Grazeland, an alfalfa cultivar that reduces the incidence of bloat. Other bloat control agents such as pluronic detergents and ionophores can also be of value. Development of grazing-tolerant alfalfa varieties is solving some of the problems associated with lack of persistence of alfalfa in mixed stands; however, they are not bloat-safe. Animal productivity commonly increases when alfalfa is included in pasture mixtures. Improvements in cattle rate of gain are observed when alfalfa contributes as little as 35% to the sward. Grazing management is the principal method for controlling pasture yield and quality as well as animal performance and bloat incidence. When grazing management is used to optimize pasture production and nutrient intake, yearling steers can gain as much as 1.5 kg head -1 d -1 and liveweight production ranging from 107 kg ha -1 (on dryland) to 1946 kg ha -1 (under irrigation) can be expected. Limiting utilization of alfalfa-based pasture to ≤70% may be more important for maximizing gain per head than managing herbage quality. La luzerne est reconnue pour son rendement éléve, tant en quantité qu'en qualité, dans les pâturages de semis. Toutefois quand on fait pâturer de la luzerne trop jeune, on court le risque de pertes d'animaux dues au météorisme chez certaines espèces de ruminants, c'est pourquoi on conseille généralement d'inclure au moins 50 % de graminées dans les mélanges à pâturage. Deux décennies d'amélioration génétique ont abouti à la mise au commerce de AC Grazeland, un cultivar de luzerne moins météorisant. Des substances antimétéorisme comme les détergents pluroniques et les ionophores, peuvent avoir une certaine efficacité. La sélection de variétés de luzerne tolérantes à la pâture règle quelques-uns des problèmes liés au manque de longévité de la luzerne en peuplement mixte, mais elle n'apporte aucune solution au problème du météorisme. La productivité animale augmente généralement lorsque la luzerne est incluse dans les associations à pâturage. Une proportion d'aussi peu que 35 % de luzerne dans la prairie provoque des améliorations du taux de gain des bestiaux. La conduite du pâturage demeure le principal moyen de manipuler le rendement et la qualité de l'herbe, de même que les performances zootechniques et les risques de météorisme. Lorsque la conduite du pâturage est utilisée pour optimiser la production d'herbe et l'absorption d' éléments nutritifs, des bouvillons d'un an peuvent prendre jusqu'à 1,5 kg par jour et par animal avec une production en vif allant de 107 kg ha -1 en culture sèche et à 1 946 kg ha -...

. 1997. Effect of grazing system and stocking rate on the productivity, botanical composition and soil surface characteristics of alfalfa-grass pastures. Can J. Anim. Sci. 77: 669-676. A 4-yr experiment was conducted (1991 to 1994) near Brandon, MB, to determine the effects of grazing system (continuous and rotational) and stocking rate [light (1.1 steers ha -1 ); heavy (2.2 steers ha -1 )] on the productivity, botanical composition and soil surface characteristics of an alfalfa (Medicago sativa L.; approximately 70%), meadow bromegrass (Bromus biebersteinii Roem & Schult.; 25%) and Russian wild ryegrass [Psathyrostachys juncea (Fisch.) Nevski; 5%] pasture. Grazing season length was shorter (P < 0.05) for cattle in continuously compared with rotationally stocked pastures in 1991, while in 1993 and 1994 it was shortest (P < 0.05) in heavily stocked continuously grazed pastures. Carrying capacity (steer days ha -1 ) was greater (P < 0.05) in heavily stocked rotationally grazed pastures compared with other treatments in 1991, 1993 and 1994 . In 1992, it was greater (P < 0.05) in heavy than light stocking rate treatments for both rotationally and continuously grazed pastures. Cattle usually gained more (P < 0.05) per day (kg d -1 ) and during the season (kg hd -1 ) at light than at heavy stocking rates, while total liveweight production (kg ha -1 ) was greater (P < 0.05) at heavy than at light stocking rates. Forage production and disappearance did not differ (P > 0.05) within grazing systems and stocking rates from 1991 to 1993, but in 1994, production and disappearance were greater (P < 0.05) at heavy than at light stocking rates. Mean seasonal herbage mass available and carry-over were greater (P < 0.05) in lightly stocked pastures than heavily stocked pastures from 1991 to 1994. After the first year of grazing, the proportion of alfalfa increased (P < 0.05), while grasses declined (P < 0.05) within all grazing treatments. In subsequent years, a trend was observed, where alfalfa declined and grasses increased in all pastures, except those stocked heavily and grazed continuously, which by 1994 had the greatest (P < 0.05) percentage of alfalfa. As years progressed, increases (P < 0.05) in basal cover concurrent with declines in bare ground were recorded on all grazing treatments, while litter cover often did not differ (P > 0.05) within either grazing system or stocking rate, except in 1992, when basal cover was lowest (P < 0.05), while litter cover was greatest (P < 0.05) on lightly stocked continuously grazed pastures compared with other treatments. Stocking rates were a key factor to optimizing individual animal performance and/or gain per hectare on alfalfa grass pastures, however differences in the effect of continuous and rotational stocking on pasture productivity were minimal. . L'objet était d'établir les effets du système pastoral (pâturage continu ou tournant), du taux de chargement (léger 1,1 ou lourd 2,2 bouvillons par hectare) sur la productivité, sur la composition floristique et sur le recouvrement...