Twenty multiparous Holstein cows in midlactation grazed pastures of 4 forage mixtures in a 12-wk study repeated during 2 grazing seasons to determine if forage mixture complexity affected intake and productivity of lactating dairy cows. The forage mixtures were 1) orchardgrass plus white clover [2 species (SP)]; 2) orchardgrass, white clover, and chicory (3SP); 3) orchardgrass, tall fescue, perennial ryegrass, red clover, birdsfoot trefoil, and chicory (6SP); and 4) 6SP mixture plus white clover, alfalfa, and Kentucky bluegrass (9SP). Total herbage intake was similar among forage mixtures, averaging 12.0 kg/d across all forage mixtures and years. Milk production and composition were not affected by forage mixture or year, and averaged 34.6 kg/d, 3.4%, and 2.8% for milk production, milk fat percentage, and milk protein percentage, respectively. The conjugated linoleic acid content of milk fat was higher for cows that grazed the 3SP, 6SP, and 9SP mixtures than from cows that grazed the 2SP mixture (1.02 vs. 0.87 g of conjugated linoleic acid/100 g of fatty acids, respectively). Blood glucose, blood urea nitrogen, and nonesterified fatty acids were not affected by forage mixture and averaged 69.2 mg/dL, 13.4 mg/dL, and 277.5 muEq/L, respectively. The results of this study indicate that altering the forage mixture in pastures did not affect dry matter intake, milk production, or blood metabolite profiles of lactating cows. The use of complex mixtures of forages in grazing systems should not affect dairy cow performance.

Temperate grasslands can be highly productive. However, those that are productive are generally heavily dependent on high inputs of nitrogen (N) fertilizer. Including legumes such as white clover (Trifolium repens L.) in the sward can reduce reliance on N fertilizer. Recent investigations have evaluated the potential of multispecies swards, which are defined as agronomically improved grasslands that include multiple plant functional groups, e.g., grasses, legumes, and forage forbs. Several of the benefits and challenges of multispecies swards are summarized in this review. To date, the most prominent forb species included in multispecies swards are chicory (Cichorum intybus L.) and ribgrass/ribwort plantain (Plantago lanceolata L.). Multispecies swards grown under reduced N fertilizer input conditions can produce as much biomass as monocultures receiving large quantities of N fertilizer. The nutritive value of multispecies swards may potentially be greater than grass-only swards, especially since forbs may contribute additional micro and macro minerals to livestock diet. While challenges associated with multispecies swards may include weed management and facilitating persistence of the forb species in particular, the overall evidence suggests that well-managed multispecies swards can enhance the productivity as well as environmental sustainability of grazing systems.

Brassica plants play an important role in common agricultural practices, such as livestock feed or biofumigation, due to the bioactivity of the natural degradation products of glucosinolate metabolites. Therefore, the ability to survey comprehensive glucosinolate profiles for individual brassicas is essential for informing proper species selection for the intended application. Current methods for glucosinolate identification and quantification involve complex or unconventional procedures, and proper reference materials are not readily available. Therefore, researchers with limited resources that require glucosinolate profiles are at an extreme disadvantage. In this work, a simple and accurate HPLC-MS method was developed and validated to build preliminary glucosinolate profiles for three agriculturally relevant forage brassica varieties [turnip (B. rapa L.), canola (B. napus L.), and rapeseed (B. napus L.)]. The average glucosinolate content across three herbage collection dates for canola, rapeseed and turnip were 2.9 ± 0.9 mg g^-1, 6.4 ± 1.3 mg g^-1, and 14 ± 3.4 mg g^-1, respectively. GLS concentrations are reported in milligrams of glucosinolate, calculated as sinigrin equivalents, per gram of dry plant material. This semi-quantitative approach for reporting total GLS content in brassicas is accurate within 15%. Several minor individual glucosinolates were identified that have not been previously reported in canola, rapeseed and turnip species, including glucotropaeolin and 4-hydroxyglucobrassicin (canola), glucoraphanin and glucoberteroin (rapeseed), and glucosinalbin and glucobarbarin (turnip). This non-targeted screen of several forage brassica varieties demonstrates the inherent variation in both the individual glucosinolate content and the total glucosinolate profile among brassicas, and highlights the importance of such glucosinolate characterization in agricultural practices. Additionally, the method developed in this study can be used as a tool for researchers with limited resources to build accurate glucosinolate profiles of brassica plants.

In 2010, the National Organic Program implemented a rule for the US stating that pasture must be a significant source of feed in organic ruminant systems. This article will focus on how the pasture rule has impacted the management, economics and nutritional value of products derived from organic ruminant systems and the interactions of grazing cattle with pasture forages and soils. The use of synthetic fertilizers is prohibited in organic systems; therefore, producers must rely on animal manures, compost and cover crops to increase and maintain soil nitrogen content. Rotational and strip grazing are two of the most common grazing management practices utilized in grazing ruminant production systems; however, these practices are not exclusive to organic livestock producers. For dairy cattle, grazing reduces foot and leg problems common in confinement systems, but lowers milk production and exposes cows to parasites that can be difficult to treat without pharmaceuticals. Organic beef cattle may still be finished in feedlots for no more than 120 days in the US, but without growth hormones and antibiotics, gains may be reduced and illnesses increased. Grazing reduces the use of environmentally and economically costly concentrate feeds and recycles nutrients back to the soil efficiently, but lowers the rate of beef liveweight gain. Increased use of pasture can be economically, environmentally and socially sustainable if forage use efficiency is high and US consumers continue to pay a premium for organic beef and dairy products.

A 4-unit dual-flow continuous culture fermentor system was used to evaluate the effects of supplementing fresh herbage with a total mixed ration (TMR) or flaxseed on nutrient digestibility, fermentation profile, and bacterial N synthesis. Diets were randomly assigned to fermentors in a 4 × 4 Latin square design. Each fermentor was fed a total of 70 g of dry matter/d of 1 of 4 diets: (1) 100% freeze-dried orchardgrass herbage (Dactylis glomerata L.; HERB), (2) 100% freeze-dried TMR (100TMR), (3) 50% orchardgrass herbage supplemented with 50% TMR (50TMR), or (4) 90% orchardgrass herbage supplemented with 10% ground flaxseed (Linum usitatissimum L.; FLAX). Preplanned, single degree of freedom orthogonal contrasts were constructed to assess the effects of feeding system (HERB vs. 100TMR), herbage supplementation (HERB vs. 50TMR + FLAX), and herbage supplemental source (50TMR vs. FLAX). Compared with the HERB diet, the 100TMR diet significantly reduced apparent digestibility of neutral detergent fiber. Herbage supplementation with 50TMR or FLAX significantly reduced or tended to reduce apparent digestibilities of dry matter, organic matter, and neutral detergent fiber, suggesting that replacing high-quality, highly digestible fresh herbage with forage TMR likely caused depressions in nutrient digestibilities. Concentration of total volatile fatty acids, molar proportions of acetate, propionate, and isovalerate, as well as the acetate:propionate ratios were all significantly higher in fermentors fed 100TMR compared with HERB, likely in response to enhanced supply of fermentable energy. In general, feeding system, herbage supplementation, and type of supplementation did not affect N metabolism in the present study. The few significant changes in N metabolism (e.g., flows of total N and non-NH3-N) were primarily linked to increased fermentor N supply with feeding herbage-based diets (HERB and FLAX). Although TMR-based diets decreased nutrient digestibility slightly, TMR offered advantages in bacterial fermentation in relation to volatile fatty acid production, which could potentially translate into better animal performance. Flaxseed shows promise as an alternative supplement for herbage-based diets; however, further in vivo evaluation is needed to determine the optimal level to optimize animal production while reducing feed costs.