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Biomedical subjects

M H Ralphs

Publications and source records attributed to M H Ralphs.

31 records · Page 2Linked to original sources
PubMed1996

Effects of previous grazing treatment and consumption of locoweed on liver mineral concentrations in beef steers.

Twelve Hereford steers (average BW = 231 kg) that had previously grazed native rangeland (Range) or irrigated winter wheat pasture (Wheat) were allowed to graze locoweed-infested rangeland from April 1 to June 9, 1994 (six steers/previous grazing treatment). Relative consumption level of locoweed and other forage classes was measured as observed bites per steer. Liver biopsy and whole blood samples were obtained from each steer before and after grazing. Liver samples were analyzed for several minerals by inductively coupled plasma-atomic emission spectroscopy, and whole blood samples were analyzed for Se. Liver concentrations of Ba (P < .001), Cd (P < .001), Ca (P < .01), Cr (P < .01), Ni (P < .001), Na (P < .01), and V (P < .001) were greater and concentrations of Mn (P < .09), P (P < .01), and K (P < .07) were less in Wheat than in Range steers. Liver concentrations of Fe, Mg, S, and Zn and whole blood Se concentrations did not differ (P > .10) between the two groups. Liver concentrations of Cr (P < .04) and Mn (P < .001) were less, and Fe concentrations were greater (P < .01), in samples taken after grazing than in samples taken before grazing of locoweed-infested range. Whole blood Se concentrations decreased (P < .01) from the beginning to the end of the grazing period, but this effect was not related (P > .15) to locoweed consumption. Changes in liver concentrations of minerals were compared relative to consumption levels of all forage classes in the locoweed-infested range. Liver concentrations of Cu decreased (r2 = .45; P < .02) as the percentage of bites consumed as locoweed increased, but concentrations after grazing locoweed-infested range were still within normal ranges. Changes in liver concentrations of other minerals were not related (P > .15) to consumption of locoweed. These data indicate that previous grazing history can have significant effects on liver mineral stores and that, under our conditions, consumption of locoweed by grazing beef steers altered liver Cu concentrations. Toxic effects of locoweed consumption would likely occur before Cu deficiency would be induced by grazing locoweed-infested range; hence, supplementation of Cu would seem unlikely to alter the course of locoweed toxicosis.

Animal Feed↗
PubMed1995

Effects of energy source and food flavor on conditioned preferences in sheep.

Livestock and range managers would have a powerful tool to direct utilization and modify plant communities if animals could be conditioned to eat specific foods or plants. We attempted to condition preferences for a low-quality forage through nutrient loading. Sheep were fed licorice or orange-flavored straw pellets then were gavaged with glucose or propionate (.381 Mcal, which amounted to approximately 13% of the daily maintenance energy requirement) or water. Four groups of ewes (n = 4) were arranged in a cross-blocked design such that each group received a unique energy/flavor combination: 1) propionate+licorice, 2) propionate+orange, 3) glucose+licorice, or 4) glucose+orange. On alternate days, each group received the other flavor plus water to create an internal control. At the end of 8 d of conditioning, preference for the two flavors was measured by two-choice preference tests. A second trial was conducted for 4 d in which the energy level was doubled to .762 Mcal. Low energy levels of either glucose or propionate did not create significant preferences. Propionate at the low-level caused satiety but at the high level conditioned an aversion to both flavors. This high level of propionate apparently caused malaise that was then associated with the taste of the flavors. The high level of glucose conditioned a preference. The high glucose treatment increased rumen microbial mass, the nutrients of which would have been absorbed in the lower gastrointestinal tract, and may have indirectly provided the positive nutrient feedback required to form a preference. There was a flavor preference for orange that was independent of the energy supplements.

Acetates↗
PubMed1994

Serum alpha-mannosidase activity and the clinicopathologic alterations of locoweed (Astragalus mollissimus) intoxication in range cattle.

Subclinical intoxication of livestock with Astragalus and Oxytropis species (locoweeds) results in decreased animal feed conversion, reduced weight gains, and reproductive failure. Sensitive diagnostic methods to definitively diagnose and monitor intoxication are needed to minimize these losses and better manage locoweed-infested pastures and rangelands. Sera from cattle grazing locoweed were evaluated for alpha-mannosidase activity, serum biochemical values, electrolytes, and thyroid hormone concentrations. As the cows began to ingest locoweed, the mean serum alpha-mannosidase activities dropped significantly (400.0 microM to 72.5 microM). Changes in other serum chemistry values were less specific; however, individual animals (generally those ingesting more locoweed) had elevated levels of alkaline phosphatase (ALP), aspartate aminotransferase, and lactate dehydrogenase, with decreased serum total protein (5.8 +/- 0.8 g/dl) and albumin (2.3 +/- 0.3 g/dl). Mean serum thyroid concentrations (both T4 and T3) were lower in animals that were ingesting locoweed. The calculated swainsonine dose correlated statistically with serum alpha-mannosidase activity, ALP, albumin, Cl, CO2, and thyroid hormone T3. This correlation suggests that serum alpha-mannosidase activity along with potential changes in ALP, albumin, and thyroid hormone concentrations is a sensitive indicator of locoweed exposure and intoxication. These parameters may also be useful for monitoring intoxication and allowing subclinically affected cattle to be removed from infested areas before irreversible damage occurs.

Animals↗
PubMed1993

Influence of cattle age, lithium chloride dose level, and food type in the retention of food aversions.

The influences of animal age and lithium chloride (LiCl) dose levels were evaluated in forming and retaining food aversions to licorice-flavored alfalfa pellets and beet pulp. Lithium chloride (100, 200, 300 mg/kg BW) was given to yearling and mature cattle by gavage (four animals per age-dose treatment group) after meals of the test food. Cattle dosed with the higher levels of LiCl formed aversions more rapidly in both trials than those dosed at lower levels. Both age classes extinguished aversions to licorice-flavored alfalfa pellets, but aversions to beet pulp persisted. Mature cattle retained aversions to beet pulp to a greater extent than did young cattle in social facilitation and single-choice persistence trials. Of dosages studied, the optimum for retaining aversions to beet pulp was 200 mg/kg BW for mature cows. Yearling cattle required 300 mg/kg for complete abstinence.

Aging↗
PubMed1992

Comparison of larkspur alkaloid extract and lithium chloride in maintaining cattle aversion to larkspur in the field.

Lithium chloride (LiCl) and larkspur (Delphinium barbeyi) alkaloid extract were compared in their effect as an emetic to create taste aversions to fresh larkspur. They were further compared in the field to determine whether the indigenous larkspur alkaloids were more effective in maintaining the aversion when conditioned cattle were subjected to the social pressure (social facilitation) of control cattle eating larkspur. Taste aversions were produced in two groups of 1-yr-old cattle by offering fresh larkspur and then gavaging with either LiCl at 200 mg/kg of BW or larkspur alkaloid extract at 1.1 to 1.6 mL/kg of BW. The third group (control) was gavaged with water. The alkaloid group was slower to form an aversion than the lithium group, requiring four doses compared with two doses. All groups were then taken to larkspur-infested rangeland to test the aversion in the field. In the first field trial in which groups grazed separately, both aversion-induced groups generally abstained from eating larkspur. In the second trial in which all groups grazed together, both aversion-induced groups consumed less than half as much larkspur as the controls, but neither group abstained completely. Larkspur alkaloids did not maintain the aversion to larkspur to a greater degree than did LiCl when aversion-induced cattle were subjected to social facilitation.

Alkaloids↗
PubMed1990

Feed preferences and habituation of sheep poisoned by locoweed.

Livestock addiction to locoweed is commonly cited as a clinical sign of locoweed poisoning. However, there have been no physiological or pathological explanations for the reported addiction. Four hypotheses were tested to evaluate locoweed's (Astragalus lentiginosus) addictive nature: 1) animals become psychologically addicted to locoweed; 2) animals have an innate preference for locoweed; 3) animals become habituated to locoweed in the sense of acquiring an acceptance or liking for it; and 4) intoxicated animals lose the ability to discriminate between feeds and eat whatever is present. Two feeding trials were conducted to evaluate these hypotheses. In 1987, 20 ewes were fed a pelleted basal feed consisting of alfalfa with 20% locoweed to induce locoweed poisoning. Five control ewes were fed pelleted alfalfa. In 1988, seven ewes were fed a basal feed consisting of alfalfa and 15% locoweed, and five control ewes were fed pelleted alfalfa. At 2- to 3-wk intervals, ewes from both trials were placed on cafeteria trials and offered a choice of four feeds (100% locoweed pellets, 15% or 20% locoweed pellets, mixed grain pellets and alfalfa pellets) to evaluate their preferences at increasing levels of intoxication. Sheep did not seek out locoweed, which would have indicated a psychological addiction. Locoweed was not innately palatable to sheep. One ewe habituated to 100% locoweed and two ewes habituated to the 15% locoweed diet. The rest of the ewes rejected the 100% locoweed pellets and the 15% or 20% locoweed basal feed when the choice of feeds was offered, even though they were severely intoxicated. Sheep show neither initial preference nor addiction to locoweed but may acquire preference (habituation).

Animal Feed↗
PubMed1990

Adverse influence of social facilitation and learning context in training cattle to avoid eating larkspur.

Through conditioned food aversion learning, livestock can be trained to avoid eating harmful plants. The objectives of this study were to determine whether social facilitation will extinguish an aversion to larkspur (a poisonous plant on mountain rangelands) and to determine whether the aversion can be reinforced to withstand social facilitation in a group-feeding and field-grazing situation. Two groups of heifers offered fresh larkspur were simultaneously infused intraruminally with lithium chloride (LiCl) to create an association between the taste of larkspur and LiCl-induced gastrointestinal distress. A third control group was infused with water. Heifers from one averted group (extinction) were paired with nonaverted controls and offered larkspur. When the extinction group sampled larkspur, and LiCl was not infused, the aversion was extinguished rapidly. Heifers in the other averted group (reinforcement), being infused with LiCl whenever they sampled larkspur, abstained from eating larkspur in the group-feeding situation. Heifers were then taken to larkspur-infested rangeland. After the control heifers began eating larkspur, the averted heifers started to sample it and the aversion was extinguished in three of four heifers. However, the aversion was renewed when the heifers were returned to the pen- and group-feeding situation where the aversion was created. Reinforced aversion was overcome by social facilitation in an unfamiliar field-grazing environment.

Animals↗
PubMed1988

Cattle grazing Wahweap milkvetch in southeastern Utah.

Cattle's grazing of the locoweed Wahweap milkvetch (Astragalus lentiginosus var. wahweapensis) was evaluated on desert and foothill winter range during the winter of 1986 to 1987. Dry, dead stalks of Wahweap milkvetch that had grown in 1985 and 1986 made up 15% of cattle diets overall, and 24% of diets when cattle grazed gravelly benches where it was abundant. Nutritional quality of Wahweap milkvetch was higher than of most associated forage, but its alkaloid concentration varied among the senescent stages. One cow aborted and two cows developed clinical signs of locoweed poisoning, including water belly (hydrops amnii). Microscopic lesions consisting of cytoplasmic foamy vacuolation were evident in both the dam and fetus. Because senescent stalks of Wahweap milkvetch are palatable and readily grazed by cattle, ranchers should not permit cattle to graze infested sites until other green forage is available in the spring.

Animal Feed↗
PubMed1988

Plant-animal interactions in larkspur poisoning in cattle.

Larkspur (Delphinium spp.) toxicity in cattle seriously impedes the efficient use of productive mountain rangelands. Larkspurs contain complex diterpenoid alkaloids that cause acute intoxication and death from respiratory paralysis. Alkaloids and their concentrations vary among larkspur species, plant parts and phenological growth stages, thus causing great variability in toxicity. Ingestion rate of larkspur by the cow, alkaloid toxicity and concentration in the plant and the kinetics of absorption and excretion interact to determine whether a cow is poisoned. Plant and animal factors influencing consumption and subsequent intoxication must be further elucidated to devise management strategies to reduce liverstock losses.

Alkaloids↗
PubMed1988

The relationship of Oxytropis sericea (green and dry) and Astragalus lentiginosus with high mountain disease in cattle.

All calves fed locoweed (green and dry Oxytropis sericea Nutt and dry Astragalus lentiginosus Dougl) at high elevation developed clinical signs, gross and microscopic lesions of congestive right heart failure. Clinical signs and microscopic lesions of locoweed intoxication were also evident. Control calves did not develop the clinical signs, gross or microscopic lesions demonstrated in the locoweed fed calves.

Altitude Sickness↗
PubMed1987

Death camas poisoning in sheep: a case report.

Approximately 250 sheep were poisoned and died from ingesting death camas (Zygadenus paniculatus) within a 2-day period on a foothill range in southeastern Idaho. Sixty to 70% of the poisoned sheep were 80-90 lb lambs and the rest were mature ewes. Poisonings were confirmed by field investigation, microhistological analysis of plant fragments from rumen contents of dead sheep, clinical signs, gross and microscopic analysis of tissues, and by experimentally feeding death camas collected on the poisoning site to 3 ewes at the Poisonous Plant Research Laboratory at Logan, UT. Clinical signs and gross and microscopic analysis of tissues were similar in ewes from the field investigation to those in ewes experimentally fed death camas. Ataxia, muscular weakness, trembling, incoordination, discharge of frothy saliva from the mouth and nose, vomition, dyspnea, collapse and death were the most common clinical signs. Gross changes included severe pulmonary congestion and subcutaneous hemorrhage. Microscopic lesions were those of severe pulmonary congestion.

Animals↗
PubMed1986

Feed aversion induced by intraruminal infusion with larkspur extract in cattle.

Twelve Hereford heifers were infused with larkspur extract (group 1, n = 4), lithium chloride solution (group 2, n = 4), or sodium chloride solution (group 3, n = 4). After 3 weeks of being fed basal ration (meadow grass hay), all heifers were offered a ration of alfalfa pellets (3,400 g) in a 2-phase, single-day feeding regimen. In phase 1, the amount eaten within 45 minutes was measured by weigh-back of uneaten pellets. In phase 2, cattle that ate greater than 150 g of pellets in phase 1 were offered the balance of uneaten pellets and were infused with their respective designated solution. Five pairings of pellet feedings and appropriate infusions were given at 2- or 3-day intervals to initially induce feed aversion. Heifers in groups 1 and 2 developed a strong aversion to pellets by the 5th feeding. Persistence of aversion was tested twice at weekly intervals. Infusion of cattle with larkspur extract or lithium chloride solution induced a persistent aversion to an otherwise palatable feed.

Animals↗