J. W. Hall

Effect of sainfoin on in vitro digestion of fresh alfalfa and bloat in steers

The effects of sainfoin (Onobrychis viciifolia) on digestion of alfalfa (Medicago sativa) were investigated in vitro and in vivo. Fresh alfalfa and sainfoin were incubated in an artificial rumen (Rusitec) in ratios of 100:0, 75:25, 50:50, 25:75 and 0:100 (as-fed). Disappearances of dry matter and N from sainfoin were 77 and 65% of those from alfalfa, respectively. Protease and endoglucanase activities, NH3-N and methane production declined (P   0.05), but cells incorporated more 15NH3N as sainfoin in the diet increased. Chopped leaves (100:0, 95:5 and 90:10 alfalfa:sainfoin) were incubated for 48 h with diluted ruminal fluid containing 0 or 50 mg polyethylene glycol, which binds tannins. Gas and volatile fatty acid productions were similar (P > 0.05) across treatments, but including 10% sainfoin (without polyethylene glycol) reduced (P < 0.05) NH3 concentrations between 8 and 24 h. Sainfoin tannins reduced degradation...

A review of the development of a bloat-reduced alfalfa cultivar

The studies that led to the development of a bloat-reduced alfalfa began in 1970. Initial work focused on the causes of bloat, the characteristics of bloat-safe and bloat-causing legumes and the development of screening methodologies. The characteristics that were examined as causal factors of bloat in legume species included soluble proteins, saponins, absence of condensed tannins, and rapid breakdown of cells in the rumen. The factor or combination of factors responsible for causing bloat in animals grazing legumes have not been clearly identified; however, of the above, rapid cell breakdown was considered to be the most promising line of research to pursue in selecting a bloat-safe legume. A 4-h nylon-bag rumen digestion technique was developed, which was used to assess the initial rate of digestion (IRD) of fresh leaf material in large numbers of alfalfa genotypes. Using this technique on a population of four alfalfa cultivars, four cycles of recurrent selection for low initial rate of digestion (LIRD...

Bloat in cattle grazing alfalfa cultivars selected for a low initial rate of digestion: A review

and Cheng, K.-J. 2000. Bloat in cattle grazing alfalfa cultivars selected for a low initial rate of digestion: A review. Can. J. Plant. Sci. 80: 493‐502. The occurrence of frothy bloat limits the practice of alfalfa grazing in spite of the availability of strains bred specifically for pasture. Bloat is a chronic condition, endemic to cattle. Prophylactics and management techniques are ava ilable to reduce its incidence but they are expensive, difficult to administer, conflict with traditional grazing management regi mens and do not eliminate bloat in all circumstances. A program to breed and evaluate a bloat-reduced strain of alfalfa was initiate d in 1980 to overcome some of these limitations. A review of the results of grazing and feeding trials using alfalfas with low initi al rates of digestion (LIRD) shows that this new strain reduces the incidence and severity of frothy bloat on pasture. Their effec tiveness in controlling bloat was related to feeding or grazing management practices, the maturity of the plants and the season of use. Graziers may reduce the risk of occasional livestock losses from bloat by using LIRD cultivars, like AC Grazeland, or managing species/cultivar mixtures in ways that reduce the initial rate of digestion. Other bloat preventive strategies, including coseeding with bloat-free legumes and using bloat-controlling prophylactics in combination with a LIRD alfalfa, are being investigated.

Seasonal grazing of Columbia milkvetch by cattle on rangelands in British Columbia.

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.

The effect of cattle grazing on the growth and miserotoxin content of Columbia milkvetch.

The growth and miserotoxin content of Columbia milkvetch (Astragalus miser Dougl. var. serotinus (Gray) Barneby) were examined following grazing of early growth by cows at a grassland site in southern British Columbia. Grazing behavior and forage consumption of cows were observed. Growth of Columbia milkvetch was determined by measuring the freeze-dried weight of each plant and miserotoxin levels were determined by a rapid screening method. Cows had a tendency to either avoid Columbia milkvetch or to consume it incidentally with other forage so long as there was adequate grass available. As grass became scarce the use of Columbia milkvetch increased. After being grazed, the rate of growth and the toxicity of Columbia milkvetch were substantially reduced. In comparison to ungrazed plants, the aboveground biomass of grazed plants was reduced by more than 50% and the average miserotoxin content per plant was reduced by more than 75% during a 6-week 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. Clearly these aspects of management require further study.

The effect of clipping on the growth and miserotoxin content of Columbia milkvetch.

Tbc growth ad miserotoxln content of Columbia milkvetcb (As&&us miwr Do@. var. zerotjnus (Gray) Bameby) were examined in clipping triain l t 2 rangeland sites in southern British Columbia during 1984 and 1986. Growtb was determined by measuring the freezedried weigbt of each plant and mhrototin levels were estimated by a rapid screening metbod tbat simplified sample preparation for spectropbotometric determination. In both years and l t both sites, yowtb and toxicity were substantially reduced in response to early clipping in tbe spring. In comparison to untreated plants, tbe aboveground biomass of clipped plants was reduced by at least % during a Cwk period of regrowth. A similar reduction was abo observed in the miserotoxin content of clipped plants. Tbe results indicate that early grazing may reduce the potential hazard of timber milkvetcb to iiveack

Alkaloid levels of a tall larkspur species in southwestern Alberta.

Tall larkspurs (Delphinium spp.) are widely distributed in western North America and they kill more cattle on rangelands than any other poisonous plant. In Alberta, Canada, D. brownii Rydb. has a long history of causing cattle poisoning. The neurotoxic norditerpenoid alkaloid methyllycaconitine (MLA) was first detected in D. brownii over 50 years ago. A 2-year (1996 to 1997) survey was conducted on the levels of MLA in D. brownii collected at 5 sites in the foothills of southwestern Alberta. The vegetative stage of growth yielded the highest levels of MLA and the decline and change in concentration during that interval could be predicted on the basis of Julian day alone. The MLA levels during bud to pod development were not significantly different but they exceeded the reported levels for MLA in low larkspur by 5-to 10-fold. A new method is described for the determination of MLA by HPLC. DOI:10.2458/azu_jrm_v53i2_majak

Efficacy of Rumensin controlled release capsule for the control of alfalfa bloat in cattle

Rumensin controlled release capsule (CRC) was evaluated in grazing trials and in confinement with fistulated steers fed alfalfa at the vegetative to early bud stage of growth. These stages promoted a high incidence of bloat, both in animal days of bloat and in daily frequency of distension. The bolus reduced the incidence of bloat by an average of 50% in five trials, the difference being statistically significant in four of them. The cultivars AC Grazeland and Alfagraze did not differ significantly in daily bloat incidence when evaluated at early stages of growth. Key words: Cattle, bloat, legumes, Medicago sativa L.

Soil moisture influences low larkspur and death camas alkaloid levels

It has long been known that alkaloid composition and concentration in plants are affected by the stage of growth and by factors at the growing site of the plant. There is, however, a lack of knowledge on the environmental factors that elicit the physiological response of alkaloid-containing plants. A 3-year survey (1992 to 1994) was conducted on the levels of zygacine and methyllycaconitine, the major neurotoxic alkaloids of death camas (Zigadenus venenosus) and low larkspur (Delphinium nuttallianum), respectively. The alkaloid levels of both species do not exhibit diurnal fluctuations, so precise sampling times during the day were not required. Both poisonous species grew in overlapping communities at 2 of the 7 sampling sites. The levels of both types of alkaloids showed similar contrasts at both sites. Lower alkaloid accumulations were associated with site conditions that reduced soil moisture stress and zygacine levels were negatively correlated with soil moisture levels at 6.5 and 14 cm sampling depths. There were no significant correlations or obvious associations between soil temperature and alkaloid levels in either death camas or low larkspur. As expected, higher alkaloid levels were associated with earlier stages of growth in both plants.