(Abstract not available.)

The Range Beef Cow Symposium XV

Cost of production for cow-calf enterprise.

Wetlands are ecologically and economically important ecosystems with high conservation value. Although wetland vegetation is strongly determined by abiotic factors, grazing disturbance may also be an important influence on this community. We evaluated the effects of livestock grazing on wetland vegetation in marsh and wet meadow zones in intermountain depressional wetlands in the southern interior of British Columbia, Canada. We sampled marshes and wet meadows in 36 wetlands along a grazing intensity gradient ranging from fully fenced and ungrazed wetlands to unfenced wetlands heavily grazed by livestock. The amount of bare ground was used as a surrogate measure of the intensity of livestock grazing. Vegetation community structure and composition was strongly associated with grazing intensity. Increased livestock grazing favored shorter-lived and smaller plants; conversely, the frequency of tall and rhizomatous species, which constitute the dominant plant species in these systems, declined with higher livestock use. The effects of grazing were more pronounced in the marsh than in the wet meadow. Associations between species richness and grazing differed between zones: native and exotic species richness showed a unimodal response in the marsh while in the wet meadow exotic richness increased and native richness showed no response. The relationship between exotic frequency and grazing was also inconsistent between zones, with a negative association in the marsh and a positive but weak association in the wet meadow. Grazing-related changes in vegetation along the grazing intensity gradient were substantial and may affect the habitat value of these wetlands for dependent wildlife such as breeding waterfowl.

Biological Conservation, volume 144, issue 1, pages 511-517

depressional wetlands, disturbance gradient, functional groups, livestock grazing, marsh, wet meadow

Frothy bloat in cattle is a serious problem and is difficult to manage under field conditions as it progresses rapidly from early signs of distension to acute distress. Scientists at Agriculture and Agri-Food Canada centres in Western Canada are committed to the development of bloat-free alfalfa grazing systems, which may require feed additives or supplements. As well, a new cultivar of alfalfa (AC Grazeland), selected for a low initial rate of digestion, will soon be available. In grazing trials the cultivar reduced the incidence of bloat by an average of 56% compared with the con- trol cultivar (Beaver). Commonly accepted mineral mixes for the prevention of bloat were tested and found ineffective but we have confirmed that poloxalene (Bloatguard?) is 100% effective if it is given intraruminally at the prescribed dose. However, under practical conditions, poloxalene can only be offered free choice and protection from bloat cannot be guaranteed. We have also shown that the water soluble polymer, Blocare? 4511, when used in the water supply is 100% effective in bloat prevention. This product is not yet registered in North America. Other strategies for bloat prevention will be discussed, including the selection of growth stages and grazing schedules, and the reduction of risk by wilting alfalfa or combining it with tannin-containing forages.

Journal of Range Management, volume 54, issue 4, page 490

feed additives, frothy bloat, legumes, pasture management

Seventy beef strip loins (Longissimus dorsi) were sampled, originating from labels prescribing pasturing (PS, suckler beef; PF, finished steers or heifers), from conventional production (CH, heifers; CB, young bulls), and from a label producing intensively fattened young bulls (LB) and prescribing specific husbandry conditions but not grazing. Samples were purchased in autumn and spring (1:1) from 33 retail stores in northeastern Switzerland. Colour was lightest in LB beef, while PS displayed the least intensive red. Shear force was low in pasture beef, with PF showing the lowest variability. Pasture beef was richer in n-3 fatty acids than beef of all other origins. The n-6/n-3 ratio was consistently below 2 in pasture beef, while it ranged above 5 in LB, and also in CH and CB when purchased in spring. Prescribing year-round feeding of grass products and the use of steers or heifers therefore guarantees n-3 enriched beef, which can be at least as tender as conventional beef. ?? 2006 Elsevier Ltd. All rights reserved.

Meat Science, volume 73, issue 2, pages 351-361

beef, meat colour, omega-3 fatty acids, pasture, tenderness

(Abstract not available.)

Ag Decision Maker

There is a dearth of knowledge on the selection and utilization of Columbia milkvetch (Astragalus miser Dougl. ex Hook. var. serotinus) by grazing livestock on rangelands in British Columbia, Four grazing trials were conducted with cattle on Columbia milkvetch range in southern interior British Columbia, In the first 2 trials during 1990 and 1991 cattle grazed an upper grassland site in late spring, In 1992 and 1993, the animals grazed a lodgepole pine forest site during early summer, The density of Columbia milkvetch and its basal area were similar at both locations, The Columbia milkvetch was not a preferred species on the grassland site as indicated by the bite count technique that determined its percentage in the diet, Consumption of Columbia milkvetch increased gradually as other forage species were preferentially selected and depleted, On the grasslands, consumption of Columbia milkvetch by individual animals did not show an addictive pattern, At the forest site, utilization of Columbia milkvetch was determined on a weekly basis during 1992 and on a biweekly basis during 1993 by paired plots, In contrast to the grassland site, Columbia milkvetch was a preferred species at the forest site where it was utilized to a greater extent than grasses or other forbs, Approximately 80% of the Columbia milkvetch was utilized during 1992 and 60% during 1993, which was significantly greater than the utilization of grasses or other forbs, Forage nutrient analysis at the forest site indicated Columbia milkvetch had higher crude protein and lower ADF content than other forages but it caused livestock poisoning in 1993.

Journal of Range Management, volume 49, issue 3, pages 223-227

acid, astragalus, astragalus miser var serotinus, diet selection, miser var serotinus, poisonous plants, timber milkvetch

Use of sheep to graze vegetation.

Discussion of sheep grazing as a vegetation management option.

Thesis

(Abstract not available.)

Growth and miserotoxin content of Astragalus miser var. serotinus were examined following grazing of early growth by cows at a grassland site in S British Columbia. Cows had a tendency to either avoid Columbia milkvetch or to consume it incidentally with other forage, but as grass became scarce use of Columbia milkvetch increased. After being grazed, rate of growth and the toxicity of Columbia milkvetch were substantially reduced. Aboveground biomass of grazed plants was reduced by >50% and the average miserotoxin content per plant was reduced by >75% during a 6-wk period of regrowth. While early grazing may reduce the potential hazard of Columbia milkvetch to livestock, the plant is not a preferred species and may not be consumed by cattle until other forage becomes scarce. Heavy grazing intensity may, in turn, result in low vigor of bunchgrasses and a deterioration of range condition which may result in more weeds in the plant community. -from Authors

Journal of Range Management, volume 42, issue 5, pages 368-371

astragalus miser, biomass, diets, growth, toxicity

(Abstract not available.)

Journal of Animal Science, volume 75, issue 3, pages 673-683

fat, fatty acids, pigs, pork, vitamin e