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Biomedical subjects

L S Bull

Publications and source records attributed to L S Bull.

At least 19 recordsLinked to original sources
PubMed1995

Consumer concerns about modern technology in agriculture: considerations for undergraduate and graduate teaching.

A number of events over the last several decades have sensitized society to the possible negative impacts of technology. The majority of our population is one or more generations removed from direct experience on farms and ranches. Thus, few individuals are aware of the dramatic changes that have occurred in agriculture. Since the establishment of the land-grant university system, agriculture in the United States has changed from a system employing 10 million farmers and farm workers each feeding five people to a system in which 2.1 million farmers feed more than 100 people each and support exports of more than $35 billion annually. There are perceptions, as well as survey data, indicating society is concerned about the use and impacts of technology in the food and agriculture system. Survey data indicate 87% of people disagreed that "economic growth is more important than environmental protection." In addition, the survey data indicate society is concerned about how technology is used and who decides which applications are to be pursued. More than 8 out of 10 people (85%) surveyed believed "citizens deserve a greater role in decisions about science and technology." There seems to be concern regarding the use of technology and resultant impacts on the environment, food safety, animal well-being, and the size and numbers of farms in the United States. Education, both formal and informal, is the key to helping the public make informed decisions regarding the role of science and technology in the food and agriculture system. The colleges of agriculture need to carefully evaluate their research, teaching, and extension portfolios to "rediscover" their mission.(ABSTRACT TRUNCATED AT 250 WORDS)

Agriculture↗
PubMed1994

Jejunal glucose absorption is enhanced by epidermal growth factor in mice.

The effects of epidermal growth factor on intestinal glucose transport were examined in mice. Glucose transport measurements were performed using an in vitro assay system that estimated the rate of accumulation of [3H]3-O-methyl-D-glucose. In Experiment 1, two-mo-old male and female mice were subcutaneously injected once daily with 0, 150 or 300 micrograms epidermal growth factor/kg body weight for 3 d. Jejunal glucose active transport was increased in a dose-dependent manner. There were no gender-related differences in intestinal glucose transport or the response to exogenous epidermal growth factor. In Experiment 2, 2-, 10- and 18-mo-old mice were administered 0 or 300 micrograms epidermal growth factor/kg body weight using a treatment similar to that used in Experiment 1. Active intestinal glucose transport was 30% greater in response to epidermal growth factor in each of the three age groups. Ouabain-sensitive and -insensitive jejunal oxygen consumption was increased in response to epidermal growth factor such that total jejunal respiration was stimulated 15 to 31%. The epidermal growth factor related percentage increase in glucose absorption was similar to the percentage increase in oxygen consumption such that the apparent energetic efficiency of glucose transport was unaffected. In both experiments, the active component of glucose transport was increased by epidermal growth factor while passive transport was not affected. Jejunal morphology and mucosal DNA and protein concentration were not altered by epidermal growth factor treatment. Epidermal growth factor-induced increases in intestinal absorption was not attributable to mucosal hyperplasia.

Age Factors↗
PubMed1992

Regulation of pancreatic exocrine secretion in ruminants: a review.

Mechanisms regulating ruminant pancreatic exocrine function differ in some respects from those in nonruminants. This may affect the post-ruminal digestion of certain dietary nutrients such as starch. Ruminants do not exhibit clearly defined cephalic and gastric phases of pancreatic regulation, a likely consequence of the continuous nature of digesta flow from the rumen. Local neural reflexes and secretin-mediated exocrine responses may be more important than stimulation by cholecystokinin. Additionally, the ruminant pancreas may be stimulated by short-chain fatty acids produced in the rumen. A "ruminal phase" of pancreatic exocrine regulation has been proposed. The failure of cattle to digest efficiently starch in the small intestine may result from an asynchrony between delivery of starch to the intestines and pancreatic amylase release.

Animals↗
PubMed1986

Distribution and management of cattle in relation to climatic zones within North America.

The United States has a diversity of climates, as noted earlier. Although one can describe, as was done here, a grid of zones based on average temperature, rainfall, and terrain, the complexity of climates within these zones based on elevation, rainfall, and temperature requires much closer evaluation. The practicing veterinarian or animal husbandman must evaluate the specific climatic conditions prevailing on the farm or ranch in question and integrate the components of that climate into the management or health practices to be recommended. There is no substitute for careful observation.

Animal Husbandry↗
PubMed1986

Effects of sodium bicarbonate, magnesium oxide, and a commercial buffer mixture in early lactation cows fed hay crop silage.

Sixteen early lactation Holstein cows fed 70% concentrate: 30% hay crop silage were used to determine effects of .7% sodium bicarbonate, .7% sodium bicarbonate plus .28% magnesium oxide, or 1.8% commercial buffer mixture (total ration dry basis). This mixture contained a variety of buffers, alkalis, and other compounds known to affect milk production or composition in some circumstances. Buffers did not affect dry matter intake, milk yield, or milk composition but decreased efficiency of milk production. Ruminal fluid pH was not affected, but fecal pH and digestibilities of dry matter, organic matter, energy, acid detergent fiber, and cellulose were increased by the mixed buffers compared with sodium bicarbonate alone. Total ruminal volatile fatty acid concentration was reduced by buffers. Compared with sodium bicarbonate alone, mixed buffers increased ruminal ammonia concentration, acetate proportion, and acetate:propionate ratio and decreased proportions of propionate and butyrate. Valerate was reduced by all three buffers. Ruminal volume and liquid dilution rate were unaffected, but buffers increased total fluid outflow from the rumen. Higher amounts of buffers or alkalis may be necessary to offset low rumen pH and affect production with hay crop silage-based diets.

Animal Feed↗
PubMed1986

Effects of sodium bicarbonate with three ratios of hay crop silage to concentrate for dairy cows.

Three ruminally cannulated Holstein cows were fed total mixed diets of hay crop silage and concentrate (30:70, 50:50, 70:30, 100:0) to evaluate effects of sodium bicarbonate supplements equivalent to 0, .4, and .7% of total ration dry matter (0, 68, and 114 g/d). Yields of milk, fat-corrected milk, fat, protein, and solids-not-fat, percentages of milk protein and solids-not-fat, and efficiency of production of fat-corrected milk declined with decreasing concentrate proportion. Buffer supplementation reduced milk fat percentage and milk yield was greater with 68 g/d sodium bicarbonate than with 114 g/d. Digestibilities of dry matter, organic matter, gross energy, cell solubles, and crude protein declined with decreasing proportion of concentrate while cellulose digestibility increased linearly. The proportion of dietary nitrogen transferred to milk decreased linearly with decreasing proportion of concentrate and sodium bicarbonate increased this transfer with the 70% concentrate diet. Sodium bicarbonate increased ruminal pH and acetate proportion while decreasing ammonia concentration. Acetate:propionate ratio was decreased by sodium bicarbonate addition to the 70% concentrate diet. High concentrate diets with hay crop silage may require higher amounts of buffers to influence production.

Animal Feed↗
PubMed1985

Rumen liquid dilution rate in dairy cows fed once daily: effects of diet and sodium bicarbonate supplementation.

Three ruminally cannulated Holstein cows fed total mixed diets of hay crop silage and concentrate (30:70, 50:50, 70:30, 100:0) were used to determine liquid volume ruminal and dilution rate with polyethylene glycol as a marker. Dosing 5 h prefeeding produced nonlinear marker dilution curves that were divided into prefeeding, eating, and resting phases, whereas dosing 2 h postfeeding produced linear dilution curves. Ruminal liquid volume calculated from either dosing method overestimated liquid volume compared to manual estimates. Mean liquid dilution rates did not differ between methods of dosing, and differences between diets were closely related to dry matter intake. Supplementation with 0, 68, or 114 g/day sodium bicarbonate did not affect ruminal liquid volume or dilution rates. Across diet and buffer treatments, liquid dilution rate during eating (23 to 32%/h) was greater than mean, prefeeding, or resting dilution rates (10 to 21%/h). Correct interpretation of ruminal volume and dilution data requires full details of dosing method, dosing time in relation to feeding, and sampling times.

Animals↗
PubMed1985

Evaluation of potato meal as a feedstuff for lactating dairy cows.

Potato meal was ensiled with a grass-legume forage at 7.5% of fresh weight and substituted for ground corn in concentrate mixtures at 0, 15, and 30% fresh weight. Production, digestion, and nitrogen balance trials were conducted on 12 lactating Holstein cows fed individually for ad libitum intake. Potato meal was consumed readily in the quantities offered. Mean daily milk production for cows receiving the hay-crop silage ensiled with potato meal was 28.6 compared with 26.3 kg for cows consuming untreated silage. Molar percentages of acetate in rumen were lower and propionate higher for cows receiving hay-crop silage ensiled with potato meal. Digestibility coefficients for dry matter, organic matter, acid detergent fiber, neutral detergent fiber, crude protein, and gross energy all tended to be lower for the silage with added potato meal. Nitrogen balance was higher for cows consuming silage with potato meal. When potato meal was added to concentrate mixes replacing corn at 0, 15, and 30%, milk production was 27.5, 26.8, and 28.0 kg/day. Potato meal can be used advantageously as a silage additive and can be included in concentrate mixtures up to 30% of the fresh weight.

Animal Feed↗
PubMed1982

Dietary sodium bicarbonate and magnesium oxide for early postpartum lactating dairy cows: effects on production, acid-base metabolism, and digestion.

In two experiments with cows in early lactation fed 40% corn silage and 60% concentrate diets (dry basis), we examined effects of 1.0% dietary sodium bicarbonate and .8% magnesium oxide in a 2 x 2 factorial arrangement on performance, acid-base metabolism, and digestion. In Experiment 1 with 20 Holstein and 4 Jersey cows, intake and milk production were not affected by treatment through 12 wk postpartum. In digestion trials at 3, 6, 9, and 12 wk postpartum, addition of magnesium oxide increased digestibility of dry matter 1.8% units by sodium bicarbonate whereas acid detergent fiber digestion increased 9 to 12% units with addition of either buffer. In Experiment 2, with four fistulated Holstein cows in a Latin square design, intake per unit body weight was increased .18% units by dietary sodium bicarbonate while milk production was unaffected. Dry matter and acid detergent fiber digestion were increased slightly by sodium bicarbonate plus magnesium oxide addition whereas nitrogen balance increased 23 g/day in cows fed magnesium oxide alone. Because of the low fiber content of the ration, milk fat percent increased .5 to .9% by addition of either buffer in both experiments and resulted in corresponding increased in fat-corrected milk. Sodium bicarbonate and magnesium oxide prevented rapid declines in rumen pH associated with feeding in Experiment 2, which related to changes in acid detergent fiber digestion. Blood acid-base metabolites were relatively unchanged by treatment in either experiment. Urinary bicarbonate and net acid excretion rates were changed on the average by +41 and +43 meq/h by sodium bicarbonate or magnesium oxide but could not be related to changes in intake and production.

Acid-Base Equilibrium↗
PubMed1981

Effect of dietary iodine on tissue iodine content in the bovine.

Twelve yearling Holstein steers were blocked by weight and assigned to receive one of three dietary I levels (0, 50 or 400 mg ethylenediamine dihydriodide [EDDI]/head/day) for 4 weeks. Average daily gain, body temperature and respiration rate were measured before and during the I feeding period, and no significant differences among treatment groups were found. Serum total I showed a significant increase with each increment of I. When animals were slaughtered, five muscle samples and liver and thyroid samples were dissected for I analysis. Mean total muscle I levels for the 0-, 50- and 400-mg treatment groups were .092, .127 and .406 micrograms/g wet tissue, respectively, each being different (P less than .05) from the other two. I concentrations did not differ statistically between individual muscles within the 0- and 50-mg treatment groups, but in the 400-mg EDDI group, the trapezius (.469 micrograms/g) and biceps brachii (.569 micrograms/g) muscles had higher (P less than .05) I concentrations than the semimembranous (.316 micrograms/g), psoas major (.365 micrograms/g) and longissimus (.307 micrograms/g). Dietary I increased (P less than .05) liver and thyroid I concentrations in the 400-mg treatment group over those observed for the 0- and 50-mg treatment groups.

Animal Feed↗
PubMed1981

Interaction of environmental temperature and anti-quality factors on the severity of summer fescue toxicosis.

Two experimental strains of tall fescue grass (Festuca arundinacea Schreb) that had previously been shown to produce differences in animal performance during the summer period were fed to Holstein calves in temperature controlled rooms. In the first year, GI-306 (less toxic) and GI-307 (more toxic) tall fescues were fed during July in rooms maintained at 10 to 13, 21 to 23 and 34 to 35 C. In the second year, the same tall fescues and orchardgrass were fed at a high temperature during May (32 to 33 C), July (34 to 35 C) and October (31 to 32 C). A comparison at a lower temperature (16 to 18 C) was also included in the July and October trials, On both years, calves consuming GI-307 tall fescue consistently had lower dry matter intakes, higher rectal temperatures, higher respiration rates and lower weight gains than those fed GI-306 tall fescue or orchardgrass at temperatures above 31 C. At lower ambient temperatures, differences in dry matter intake, rectal temperature and respiration rates between animals on the two strains of forage were not statistically different. The results demonstrate the poor performance of cattle grazing fescue is related to environmental temperature and that the toxic substance(s) is present throughout the growing season.

Animals↗
PubMed1981

Dietary fermented ammoniated condensed whey and postprandial effects on blood and urine acid-base metabolites in lactating cows.

Effects of a fermented whey product containing 38% lactic acid, time post-feeding, and temperature on acid-base metabolism were studied with four lactating Jersey cows in a 4 X 4 Latin square. Treatments included 0, 33, 66, and 100% replacement in soybean meal with fermented whey in a 60% corn silage, 40% concentrate diet (dry basis). Increasing fermented whey to 100% reduced intake and mild production, 27 and 32% compared to animals fed 0 and 33% fermented whey diets. Fermented whey had no effect on blood pH, carbon dioxide tension, bicarbonate, and potassium whereas increasing fermented whey about 33% replacement reduced glucose and sodium in plasma 15 and 40 mg/100 ml from controls. Increasing consumption of fermented whey to 100% replacement increased urinary ammonium excretion 1365/meq per day and slightly decreased urine pH, which suggested changes in acid excretion. Effects of time postfeeding on blood traits were measured from samples taken at 0, 1, 2, 3, 4, 6, and 8 h. Blood pH was higher at 1 to 3 h as compared with 4 to 8 h postfeeding, whereas carbon dioxide tension and bicarbonate increased 10.6 mm mercury and 6.3 meq/liter at 1 h and declined afterward. Period effects for blood acid-based characteristics showed decreasing blood carbon dioxide tension with increasing ambient temperature.

Acid-Base Equilibrium↗
PubMed1980

Energy and protein metabolism in ewes as influenced by age and dietary protein-calorie ratio.

A 2 X 2 X 2 fractorial design of treatments was used to study effects of age (20 months or 10 years), dietary energy density (3.0 or 3.5 kcal DE/g) and protein level (8 or 16% crude protein) on energy and nitrogen metabolism in two groups of ewes, with emphasis on efficiency of metabolizable energy utilization. Plasma glucose concentrations were the same for sheep in each age group, regardless of diet; plasma lactate was higher (P less than .03) in plasma of old ewes and decreased (P less than .01) in concentration when dietary energy density was increased. Plasma urea nitrogen was higher (P less than .0001) in ewes fed diets containing 16 vs 8% protein, and plasma ammonia concentrations were higher (P less than .02) in old ewes Dietary energy and protein levels affected digestible and metabolizable energy, but no age-related effects were observed. Nitrogen retention was increased when either energy (P less than .0001) or protein (P less than .003) intake increased. Oxygen consumption was the same for sheep of either age (expressed per kilogram metabolic body weight), while estimated maintenance requirement and heat production were higher for old ewes. Metabolizable energy utilization was lower (P less than .05) in old ewes fed the lower energy density diets than in those fed the higher energy diets. Increasing dietary energy density increased (P less than .05) efficiency of metabolizable energy utilization in old ewes to a level comparable to that observed in young ewes.

Aging↗
PubMed1980

Effect of dietary calcium and sodium on potassium requirement for lactating dairy cows.

In two experiments we studied the effect of dietary calcium and sodium on the potassium allowance of .7 to .8% for lactating cows. In Experiment 1, 12 first-lactation cows in midlactation were fed three diets containing .52, .77, and 1.04% potassium with four dietary calcium concentrations .50, .69, .87, and 1.03%. Increasing dietary potassium from .52 to 1.04 increased intake of dry feed as a function of body weight. With rations containing 17% coarsely ground fiber, increasing dietary calcium up to 1.03% increased intake and milk production 1.3 kg per day and 1.6 kg per day linearly. In Experiment 2, 16 cows in midlactation were fed rations with two potassium (.42 and .84%) and with two sodium concentrations (.31 and .52%). Increasing dietary potassium increased dry matter intake 1.2 kg per day while dietary sodium had no effect on intake. Potassium had no effect, but increasing sodium decreased fat-corrected milk 1.7 kg per day. Of potassium, sodium, magnesium, and calcium in serum, potassium was the element most consistently affected in both experiments. Increasing dietary potassium to .77 and .84% increased serum potassium. Dietary calcium and sodium had little effect on potassium required for lactating cows.

Animals↗
PubMed1980

Effect of dietary sodium bicarbonate and magnesium oxide on production and physiology in early lactation.

Twenty cows were in an experiment to measure effects of dietary buffers, sodium bicarbonate and magnesium oxide, on ration adjustment and incidence of metabolic problems in the first 8 wk postpartum. Cows were fed 2.7 kg grain per day and alfalfa ad libitum prepartum and switched immediately to a complete ration of 40% corn silage and 60% concentrate (dry matter) postpartum. Treatments included 1.5% sodium bicarbonate and .8% magnesium oxide (total ration dry matter) fed in a 2 x 2 factorial arrangement. Cows receiving bicarbonate peaked 2 to 3 wk earlier in intake and averaged 2.1 kg per day greater intake than those fed the control diet. Actual milk production was increased by sodium bicarbonate with greatest differences for cows receiving both buffers averaging 3.8 kg per day more milk than control cows. Increases over co ntrols were 2.6 and 5.6 kg fat-corrected milk per day for cows receiving sodium bicarbonate alone or in combination with magnesium oxide, respectively. Sodium bicarbonate increased acetate to propionate molar ratios in rumen samples taken at 1 and 2 wk postpartum whereas neither buffer had any effect on rumen pH. Blood hematocrit and urine pH were not affected by treament. Magnesium oxide increased fecal pH .8 units and slightly decreased fecal starch, but sodium bicarbonate had no effect.

Animals↗