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Biomedical subjects

A Trenkle

Publications and source records attributed to A Trenkle.

At least 37 records · Page 2Linked to original sources
PubMed1985

Evaluation of the use of deuterium oxide dilution techniques for determination of body composition of beef steers.

Body composition as estimated by a one- or two-compartment deuterium oxide dilution technique was compared with directly measured body composition of 15 large- and 15 small-frame steers. Body composition of the steers was measured at 219, 412 and 603 kg live weight. Empty body protein was overestimated (P less than .05) 3.6% from a one-compartment model (1 CM, using the slope, intercept method), while empty body protein was underestimated (P less than .05) 5.4% from a two-compartment kinetic model (2CM). Empty body ether extract estimated by 1 CM was not significantly different from the direct method, although 4.7% larger. Empty body ether extract was overestimated (P less than .001) 32.2% by the 2CM. Empty body water was accurately estimated from the 1CM when a 3.2% correction factor was used for the overestimation of total body water by the 1CM, but water in gastrointestinal tract contents was overestimated (P less than .001) 13.4% by the 1CM. Empty body water was underestimated (P less than .001) 7.8% by the 2CM, and water in gastrointestinal tract contents was overestimated (P less than .001) 41.8% by the 2CM due to its dependence on regression equations that differ between groups of cattle. The 2CM offered no advantage over the 1CM. A three-compartment model was not better than the 2CM in estimating body water compartments. Assuming the amount of empty body water associated with either empty body protein or ash to be constant seemed to be valid. Suggested values calculated from data presented in the literature for growing cattle with an empty body weight greater than 175 kg are .302 and .0668, respectively, for the ratios of protein and ash to water. The relationship between empty body fat and water was, percentage empty body fat = 94.27--(1.267)(percentage empty body water), which had a 1.25 residual standard deviation and a .98 coefficient of determination.

Animals↗
PubMed1985

Glucagon, insulin, growth hormone, and some blood metabolites during energy restriction ketonemia of lactating cows.

Six Holstein cows were sampled hourly for 24 h for plasma concentrations of hormones and metabolites. Cows were sampled at about 2 wk prepartum, at 3 wk postpartum, during a ketonemia induced by feed restriction to 54% of ad libitum intake, and after a recovery period. They were fed long alfalfa hay postpartum. The onset of lactation caused concentrations of growth hormone, glucagon, acetoacetate, beta-hydroxybutyrate, and total amino acids of plasma to increase and those of glucose and insulin to decrease. Feed restriction exacerbated changes at 3 wk postpartum except for total amino acids and glucagon, which both decreased to prepartal concentrations. Resumption of ad libitum feeding caused most hormones and metabolites to return to prepartum concentrations. Diurnal variations in response to feeding twice daily were most evident for growth hormone, free fatty acids, and total amino acids. The 3-wk postpartum and ketonemic periods gave the greatest responses to feeding. Molar ratios of insulin to glucagon and insulin to growth hormone tended to decrease at 3 wk postpartum and decreased further in ketonemia, demonstrating hormonal adaptations to decreased energy intake during lactation. Lactation ketosis results from more than severe energy deficit.

Acidosis↗
PubMed1983

Growth and development of meat animals.

During the past 25 yr, animal scientists have learned much about the effects of environmental factors, nutritional treatments, the use of anabolic agents and genetic selection on growth of animals. Progress has been made in terms of body and carcass composition as well as a more fundamental understanding of growth at the cellular level. Current emphasis is directed towards action of hormones on tissue metabolism, factors regulating hormone secretion, mechanisms of synthesis and degradation of proteins and the energetic efficiency of protein and fat synthesis. The overall objectives are to control growth of animals with respect to rate and composition of gain and to improve the efficiency of growth.

Adipose Tissue↗
PubMed1981

Endocrine regulation of energy metabolism in ruminants.

Partitioning of nutrients among tissues of the body is one role of the endocrine system. Skeletal muscle, adipose tissue, and lactating mammary gland are tissues that utilize most of the energy consumed in excess of maintenance. The energy metabolism of ruminants is complicated by the lack of absorption of glucose because of the fermentation of carbohydrates in the rumen. Increased secretion of glucagon after feeding promotes hepatic gluconeogenesis from absorbed amino acids. During fasting, gluconeogenesis is maintained by increased secretion of glucocorticoids. Based on observation form a number of diverse experiments with cattle and sheep, it seems that growth hormone increases the flow of energy to skeletal muscle and the mammary gland, whereas insulin increases the utilization of energy by the adipose tissue. Nutritional and genetic factors associated with secretion of these hormones are discussed.

Animals↗
PubMed1978

Relation of hormonal variations to nutritional studies and metabolism of ruminants.

Variations in concentrations of growth hormone, insulin, glucagon, prolactin, adrenal corticoids, and thyroid hormones in blood plasma of ruminants as related to circadian rhythms, environmental factors and nutrition are reviewed. Rhythms in prolactin concentrations are related to light and temperature. Concentrations of prolactin in plasma are higher in warm environments and during longer photoperiods. There is episodic secretion of growth hormone in cattle with frequent peaks in plasma concentrations during 24 h. Marked increases in environmental temperature result in greater secretion of growth hormone for short times followed by a decline in plasma concentration with prolonged exposure. Extreme cold temperature also increases growth hormone concentrations in plasma. Secretion of thyroid hormones increases in cold and decreases in warm environments. Circadian rhythms are definite for plasma concentrations of adrenal corticoids in ruminants adjusted to their surroundings. Peaks occur late in dark periods, and lows occur during the end of light periods. Circadian patterns have not been consistent for secretion of insulin. Prolonged subjection to stresses such as noise, handling, and restraint can modify concentrations of prolactin, growth hormone, and adrenal corticoids. Changes in concentrations of insulin may occur if blood glucose is increased. After feeding, concentrations of growth hormone in plasma decrease and concentrations of insulin and glucagon increase. Relationships of these changes with metabolism are discussed.

Adrenal Cortex Hormones↗
PubMed1977

Changes in growth hormone status related to body weight of growing cattle.

The growth hormone (GH) status of 24 castrated male cattle was studied over a range of body weights by measuring GH in the blood plasma and anterior pituitary and by calculating metabolic clearance (MCR) and secretion rates after injection of GH. As the cattle increased in size, pituitary weight and GH content, MCR of GH and secretion of GH decreased relative to body weight. Plasma concentrations of GH did not decrease as markedly as secretion because MCR/body weight was also lower in the larger animals. At all sizes, more than 99% of the total GH in the body was located in the anterior pituitary. It was calculated that the pituitary releases 0.58% of its GH content per hour. This rate of release did not significantly change with body weight. It is suggested that basal secretion of GH by the anterior pituitary is related to GH content and that, as animals grow, there is gradually less GH available per unit of body mass.

Animals↗
PubMed1976

The anabolic effect of estrogens on nitrogen metabolism of growing and finishing cattle and sheep.

Estrogenic compounds are effective in stimulating live weight gains and improving feed efficiency of growing and finishing ruminants. With the proper use of diethylstilbestrol or estradiol, weight gain and feed efficiency are improved approximately 15 and 12 percent, respectively. The administration of estrogenic substances to finishing cattle or sheep results in heavier carcasses containing more protein and moisture and less fat. Estrogens do not appreciably affect rumen fermentation or digestibility of the diet but improve the utilization of the absorbed nutrients. Evidence to support the concept that the increased weight gained with estrogen treatment is the result of anabolic reactions includes a decrease in plasma urea, decrease in plasma levels of most of the essential amino-acids, decreased excretion of urea and total nitrogen in the urine and increased retention of nitrogen, phosphorus and calcium. There is no change in body water space or tubular reabsorption of urea in sheep treated with diethylstilbestrol to account for some of these observations. More direct evidence that estrogens exert their major influence on nitrogen metabolism in the body and more specifically on protein synthesis comes from an experiment where cattle fed diethylstilbestrol deposited 33 percent more protein and 18 percent less fat in body weight gain as compared with control animals. The use of the hormone resulted in a significant improvement in the efficiency of utilizing dietary protein for body gain and a slight decrease in the efficiency of converting dietary energy to body gain. Enlargement of the pituitary, thyroid and adrenal glands and higher plasma levels of growth hormone, insulin and glucose have been found in experiments designed to study the effect of estrogens on the endocrine system of ruminants. These studies, along with the observation that an intact pituitary gland is necessary for estrogens to increase nitrogen retention in sheep, support the theory that estrogens are anabolic in ruminants because of increased secretion of growth hormone by the anterior pituitary. If follows that the increased secretion of growth hormone results in increased blood glucose which then stimulates secretion of insulin. Both growth hormone and insulin would be stimulatory to protein synthesis. This theory of the mode of action is further supported by the findings that injections of growth hormone closely resemble the effects of diethylstilbestrol on nitrogen retention and blood metabolites in sheep.

Anabolic Agents↗
PubMed1975

Growth hormone and cortisol levels in the annual cycle of white-tailed deer (Odocoileus virginianus).

The annual cycles of growth hormone and cortisol levels in white-tailed deer were followed. No significant difference was found in the average cortisol levels in a large group of animals during the year. In contrast to cortisol, growth hormone (GH) investigated by heterologous bovine GH radioimmunoassay, seems to have a distinct annual rhythm. High levels of GH in plasma were found between casting and the first week of antler growth with the peak of 23.1 ng/ml (estimated in bovine GH equivalents) in the middle of April. From the middle of June until the middle of November a plateau averaging 3 ng/ml was found. The relationships between very rapid growth of a bone tissue and the influence of GH and sex hormones are discussed.

Acclimatization↗