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Biomedical subjects

L J Koong

Publications and source records attributed to L J Koong.

At least 19 recordsLinked to original sources
PubMed1992

Nitrogen and lipid metabolism in heifers fed at increasing levels of intake.

The relationship between N and lipid metabolism was investigated in heifers fed five different levels of feed intake (five heifers per treatment group). Targeted ME intakes were 84, 123, 157, 191, and 225 kcal per kt.75 per day, which were .76x, 1.12x, 1.43x, 1.74x, and 2.05x (times) the estimated ME requirement for maintenance. After 120 d on trial, the heifers were moved to a confinement building for 7 d, and feces and urine were collected over a 3-d period. On the 1st d of confinement, blood samples were collected every 15 min for a total of 15 samples. Because the group fed at 1.43x maintenance was fed improperly during the period in confinement, this group was omitted from the study. Adipose tissue samples were obtained at slaughter to obtain in vitro measures of lipid metabolism. As feed intake increased, N retention increased (P less than .05) from 1.7 to 24.3 g/d. Daily urinary N tau-methylhistidine excretion was significantly different between the .76x and 1.74x treatments (769 vs 1,575 mumol/d, respectively). The fractional breakdown rate of myofibrillar proteins also was significantly different between these two groups of heifers (1.49 vs 2.44%/d, respectively). Plasma glucose and insulin were lowest (P less than .05) at the lowest level of feed intake. Conversely, plasma nonesterified fatty acids were lowest (P less than .05) in those animals receiving the highest level of feed intake. Subcutaneous adipocytes were smallest (93 microns) in the heifers fed at 33% ad libitum intake and largest in heifers fed at 76 or 90% ad libitum intake (115 and 110 microns, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1990

Effects of short term nutritional manipulation on organ size and fasting heat production.

Two studies were conducted to study the effects of short term nutritional manipulation on the organ size and the fasting heat production of pigs and sheep. The results of these studies indicate that fasting heat production can differ up to 40 per cent for animals of same age and weight, but with different nutritional backgrounds. Those animals on a higher plane of nutrition preceding measurements had higher fasting heat production, in spite of being the same age and body weight. At the same time, the weights of metabolically active organs such as the stomach, the small and large intestine, the liver and the kidneys are also very sensitive to the nutritional manipulation, in a parallel direction to that observed with fasting heat production. These findings provide strong evidence that the energy expenditures of the metabolically active tissues account for a significant amount of basal metabolic activity far in excess of the proportional weights of these tissues.

Animals↗
PubMed1986

Effect of previous nutrition on body composition and maintenance energy costs of growing lambs.

1. Forty-eight intact male lambs (30 kg) were fed to gain 16 (H), 5 (M) or -6 (L) kg during a 42 d interval (period 1). Lambs from each of the H and M groups were fed to gain either 16 (HH, MH), 5 (HM, MM) or -6 (HL, ML) kg and lambs from the L group were fed to gain 27 (LS), 16 (LH) or 5 (LM) kg during the ensuing 42 d (period 2). 2. Fasting heat production (FHP) of four lambs from each treatment was determined at the end of period 2. 3. Weights and compositions of the carcass, offal and digesta-free body as well as weights of major internal organs were determined for four lambs of each treatment at the end of periods 1 and 2. 4. Within groups of lambs of similar weight at the end of period 2, body composition was, in general, similar, but FHP was greater in lambs that had been on higher planes of nutrition during period 2. 5. Within groups of lambs of similar weight, lambs that were fed at higher planes of nutrition during period 2 had greater weights or proportions of liver, small intestine, large intestine and stomach. 6. Neither weight of the liver, kidney, stomach, small intestine, large intestine nor daily fasting heat production were constant functions of body-weight. Relations of these traits to body-weight changed with rate of gain. 7. Regression analysis indicated that the feeding of lambs at higher planes of nutrition during period 1 resulted in higher maintenance requirements of those lambs during period 2.

Animal Nutritional Physiological Phenomena↗
PubMed1985

Assessment of interrelationships among levels of intake and production, organ size and fasting heat production in growing animals.

Although the concept of metabolic body size (kg0.75) has gained widespread use in the field of energy metabolism, its application to the growing animal has been questioned. Fasting heat production, or maintenance, rather than being a constant function of body size, has been shown to vary because of breed, sex, condition, physiological state, production level, nutrition level and environmental conditions. Data are presented to show that fasting heat production and maintenance vary with nutritional level or rate of growth in animals postweaning. Variation in these energy expenditures are related to variation in weight of metabolically active internal organs. Weights of liver and gut and fasting heat production are shown to be functions of body size and level of production. More information is needed to ascertain the primary components of energy expenditures in animals and to quantitatively relate these components to animal energy metabolism.

Animal Nutritional Physiological Phenomena↗
PubMed1984

Effect of plane of nutrition on adipose tissue lipid metabolism in genetically obese and lean pigs.

Genetically lean and obese pigs of 27 kg body weight were individually fed at varying levels of intake. During the first 5 weeks (period 1) the pigs on the high plane nutrition (H) gained 19 kg, those on the medium plane (M) gained 7 kg and those on the low plane (L) lost 5 kg. During the second 5 weeks (period 2) the M pigs gained an additional 7 kg (MM), whereas the period 1 H pigs were fed to lose 5 kg (HL) and the period 1 L pigs were fed to gain 19 kg (LH). All pigs were targeted to weigh 41 kg at the end of 10 weeks. Subcutaneous adipose tissue samples were obtained by biopsy from each pig on day 28 and day 63 of the experiment, i.e., after 4 weeks of feeding a particular level of intake in each period. In vitro glucose metabolism to CO2, total lipids and glyceride fatty acids as well as basal and epinephrine-stimulated lipolytic rates were assessed. Obese pigs had greater cell size and lipogenic and lipolytic rates than lean pigs. During both periods the glucose metabolism rates paralleled the plane of nutrition, i.e., the low intake level yielded low rates and the high intake level yielded high rates. The lipolytic activities were refractory to the plane of nutrition. Finally the less muscular, obese and more muscular, lean pigs presented similar qualitative metabolic responses to their planes of nutrition, although the quantitative responses were divergent.

Adipose Tissue↗
PubMed1983

Improvements to the mathematical description of prenatal growth.

The exponential form of growth was used to describe prenatal growth in mouse, rat, guinea pig, swine, sheep, cattle and man. Instantaneous growth rate was permitted to vary as a function of time and, in litter bearing species, number of fetuses. Models for which instantaneous growth rate decreased linearly in time had a tendency to overestimate fetal weight from mid-gestation until midway through the last trimester of pregnancy and subsequently, underestimate fetal weight. When instantaneous growth rate varied as a quadratic function of time, a more accurate and precise prediction of fetal weights resulted.

Animals↗
PubMed1982

Effects of plane of nutrition on organ size and fasting heat production in pigs.

Twenty-seven 12-week-old barrows with average initial weight of 27 kg were randomly assigned to three treatments. The first group (HL) was fed to gain 19 kg body weight during the first 35 days (period 1) and to lose 5 kg during the second 35 days (period 2). The second group (MM) was fed to gain 7 kg during both periods 1 and 2. The third group (LH) was fed to lose 5 kg during period 1 and to gain 19 kg during period 2. At the end of the 70-day period, 7 pigs from each treatment were fasted for 30 hours and fasting heat production (FHP) was measured by indirect calorimetry. The animals were slaughtered and weights of stomach, small and large intestine, liver, pancreas, spleen, kidneys and heart were measured. Although all animals had the same final body weight, animals on the higher plane of nutrition during period 2 had significantly higher FHP and higher weights for stomach, small and large intestine, pancreas, liver and kidneys. FHP and the weights of small intestine, pancreas and liver from animals receiving the higher plane of nutrition during period 2 (LH) were 50% heavier than that from animals on low plane (HL). Positive correlations exist between FHP and weights of stomach, small intestine, large intestine, pancreas, liver and kidneys. These results indicate that prior nutritional history significantly influences FHP, which is highly correlated to weights of metabolically active organs.

Animals↗
PubMed1982

Effect of insulin on fat and protein deposition in diabetic lean and obese rats.

Five-week-old male obese and lean Zucker rats were made comparably diabetic by intracardiac injections of alloxan (65-72 mg/kg body wt). Lean rats were then given daily injections of protamine zinc insulin at 3 doses: 0.25, 1.25, and 4.0 U.100 g body wt-1.day-1 for 3 wk. Obese rats received identical amounts as corresponding lean controls independent of body weights. The drop of blood glucose concentration after injections of regular insulin and the percentage fall in radioactive plasma insulin after injections of 125I-insulin were comparable in lean and obese rats. Weight gain, fat gain, and protein gain over 21 days increased with increasing amounts of insulin administered. However, at the same dose of insulin, although weight gain was comparable, fat gain was higher and protein gain was lower in obese rats when compared to lean controls. These results suggest that the enhanced lipid deposition of the obese Zucker rat is not totally dependent on insulin levels, but is exaggerated by hyperinsulinemia.

Animals↗
PubMed1982

Maternal energy status of beef cattle during single and twin pregnancy.

A study was undertaken to determine the metabolizable energy (ME) intake and ME requirement for beef heifers and cows during twin pregnancy. Weekly feed consumption and body weights were recorded during the last trimester of twin pregnancy for 19 Hereford cows and 16 Hereford heifers. The same data were recorded for six Hereford cows and eight Hereford heifers that calved singles. ME intake per unit of metabolic body size was higher for heifers than cows (P less than .05), but was not affected by whether the dam was pregnant with a single or with twins. In general, ME intake decreased during the last trimester of pregnancy. During this time, heifers and cows with singles gained weight (pregnant weight minus weight of the conceptus), while dams with twins lost weight (P less than .01). The greatest weight loss for dams with twins was observed late in pregnancy. The ME requirement of pregnancy was greater for dams with twins than singles (P less than 0.01), and the difference in maintenance ME requirement approached significance (P less than .10). The high ME requirement for the twin pregnancy and the weight loss experienced by dams during the last trimester may have implications for management decisions pertaining to the prevention of complications that often occur with twin pregnancy in cattle.

Animals↗
PubMed1976

Utilization of energy for maintenance and for fat and lean gains by mice selected for rapid postweaning growth rate.

The metabolizable energy intake (MEI) required for maintenance and the efficiency of utilization of metabolizable energy available for gain (MEA) were determined for a line of mice (rapid growth) selected for 41 generations for rapid postweaning weight gain and for a contemporarily mated line (control) that had been randomly selected. Feed intake of individually housed rapid growth and control males was restricted above maintenance or was ad libitum from 21 to 42 days of age. Regressions of change in body energy per unity metabolic body size on MEI per unit metablic body size showed that the maintenance requirement for each line of mice was 176 kcal per unit metabolic body size per day and that the rapid growth line was more efficient than the control line in utilizing MEA (50% vs. 23%) to promote an increase in body energy. Although the proportions of MEA used for fat (PF) and lean (PL) gains and the net efficiencies with which those proportions were utilized for fat (NF) and lean (NL) gains were unknown, the products of proportion and efficiency for fat gain (PF X NF or fat energy deposition coefficient) and for lean gain (PL X NL or lean energy deposition coefficient) were determined. The results demonstrate that 41 generations of selection for rapid postweaning weight gain did not change the lean energy deposition coefficient, but did alter the fat energy deposition coefficient. These data suggest that the two lines of mice use different proportions of MEA for fat gain and/or utilize MEA for fat gain at different efficiencies.

Adipose Tissue↗
PubMed1976

Lactational efficiency complex of rats: provisional model for interpretation of energy balance data.

In experiments to determine maintenance requirements and partial efficiencies of conversion of diet and body tissue to milk, correlations between independent variables interfered with multiple regression procedures usually used in analyzing nutritional energetic data. Therefore, an alternative of a largely deterministic model of energy transformations in lactating rats was developed. Food intake, initial and final body weights, and diet composition were inputs to the model. These inputs were partitioned among the several metabolic functions of lactating rats within the model, and estimates of milk energy, heat increment of production, energy used for maintenance, and heat increment of maintenance were computed. The model was validated with rats and diets not used in model development. Inferences were: (a) average efficiency of body energy conversion to milk is 83%; (b) average gross and net efficiencies of milk production on balanced rations are 57 and 80%; and, (c) maintenance requirements vary as a function of food intake. A logistic function relating maintenance to food intake was developed based on the postulate that changes in intake of food cause changes in weights of several vital organs changing the maintenance requirement. This postulate explains, in part, changes in maintenance requirements during long food restriction and during gestation and lactation.

Animals↗
PubMed1975

Iterative computation of metabolic flux and stoichiometric parameters for alternate pathways in rumen fermentation.

A model is presented which has been derived to compute the end-products of rumen fermentation from knowledge of the input of feedstuff. The model comprises a set of algebraic equations for the fermentation of each of the following feedstuff components: soluble sugars, starch, cellulose, hemicellulose and protein. The equations were derived from known biochemical stoichiometric relationships. A iterative, non-linear least sqares method (steepest descent) was used to estimate parameter values. In a sample run the inputs used were from an experiment where eight sheep were fed white clover. The model predicted values were in good agreement with the experimental values.

Animals↗
PubMed1975

A model of heat flow in the sheep exposed to high levels of solar radiation.

The fleece is an important component in thermoregulation of sheep exposed to high levels of solar radiation. A model written in CSMP has been developed which represents the flow of energy between the sheep and its environment. This model is based on a set of differential equations which describe the flux of heat between the components of the system--fleece, tip, skin, body and environment. It requires as input parameters location, date, time of day, temperature, relative humidity, cloud cover, wind movement, animal weight and linear measurements and fleece length. At each integration interval incoming solar radiation and its components, the heat arising from the animal's metabolism and the heat exchange by long-wave radiation, convection, conduction and evaporative cooling are computed. Temperatures at the fleece tip, skin and body core are monitored.

Animals↗