SEARCH · PubMed Health

Results for “nonlinear analyses”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources

PubMed1995

Kinetic mechanism of chloramphenicol acetyltransferase: the role of ternary complex interconversion in rate determination.

Chloramphenicol acetyltransferase (CAT) catalyzes the acetyl-CoA-dependent acetylation of chloramphenicol (Cm) by a ternary complex mechanism and with a random order of addition of substrates. A closer examination of the mechanism of the reaction catalyzed by the type III CAT variant (CATIII) has included the measurement of the individual rate constants by stopped-flow fluorimetry at 5 degrees C. Under all conditions employed, product release from the binary complexes in both forward and reverse reactions was found to be too slow to account for the observed overall rate of turnover for the reaction. Additional, faster routes for product release are achieved via the formation of the nonproductive ternary complexes (CAT:3-acetyl-Cm:acetyl-CoA and CAT:CoA:Cm). The release of 3-acetyl-Cm from the binary complex is 5-fold slower than kcat (135 s-1 at 5 degrees C), whereas the dissociation rate constants of 3-acetyl-Cm from the ternary complexes with CoA and acetyl-CoA are 120 and 200 s-1, respectively. Arrhenius plots of dissociation rate constants indicate a slow release of products over a broad temperature range. Computer simulations based on the rate constants of CATIII applied to a ternary complex mechanism, assuming random order of substrate addition and product release, yielded nonlinear initial rates of product formation unless both nonproductive ternary complexes were included in the model. Simulated steady-state kinetic analyses based on the latter assumption yielded kinetic parameters that compared favorably with those determined experimentally.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyl Coenzyme A↗

PubMed2003

Stopping and restarting an unfolding action at various times.

The ability to inhibit an unfolding action is usually investigated using a stop signal (or gostop) task. The data from the stop-signal task are often described using a horse-race model whose key assumption is that each process (i.e., go, stop) exhibits stochastic independence. Using three variations of a coincident-timing task (i.e., go, gostop, and gostopgo) we extend previous considerations of stochastic independence by analysing the go latencies for prior effects of stopping. On random trials in the gostopgo task the signal sweep was paused for various times at various distances before the target. Significant increases in latency errors were reported on those trials on which the signal was paused (p <.005). Further analyses of the pause trials revealed significant effects for both the stopping interval (p <.001) and the pause interval (p <.05). Tukey post hoc analyses demonstrated increased latency errors as a linear function of the stopping interval, as expected, and decreased latency errors as a nonlinear function of the pause interval. These latter results indicate that the latencies of the go process, as reflected in the latency errors, may not exhibit stochastic independence under certain conditions. Various control mechanisms were considered in an attempt to explain these data.

Arm↗

PubMed1998

Economic values in broiler breeding.

The objectives of this study were to derive economic values in broiler breeding and to determine their relationship with production circumstances. Economic values were derived using a deterministic economic model based on profit equations with a fixed amount of broiler meat output of the production system. Nonintegrated and the integrated broiler production systems were studied. The difference between these originates from different definitions of cost components and scaling aspects. For each stage of an nonintegrated system, the model calculated the profit margin; for an integrated system, (total) cost prices per unit of product at each stage were calculated. The Dutch broiler performance data and prices were input into the model as the representative situation. For all traits, in the nonintegrated system, economic values were derived, expressed as Dutch guilders (Dfl) per unit of product, where the unit of product depends on the stage of the production system and equals an egg for the multiplier breeder, a day-old chick for the hatchery, and a marketable broiler for the commercial grower and processor. Resulting levels of economic values were illustrated by showing underlying cost or profit changes in the production system. For the integrated system, economic values were expressed as Dfl x marketable broiler(-1) x unit(-1). Economic values of traits in the integrated system were also derived for situations where technical parameters or prices of productive factors were changed (20% increase or decrease). A general conclusion from these sensitivity analyses is that the economic values are sensitive to production levels, product prices and feed prices; there are both linear and nonlinear relationships between economic values and production circumstances.

Agriculture↗

PubMed1988

Lactation and cancer risk: is there a relation specific to breast cancer?

Relations between previous lactation experience and risks of cancer of the breast and other sites were investigated after follow-up of 50,274 parous women from 1961 through 1980. Among women with complete information on lactation, 5102 developed cancer and, of these, 1136 were diagnosed with breast cancer. Analyses of associations with mean duration of lactation per birth and duration for each of the three first births suggested a nonlinear relation to breast cancer. The highest risk was observed for those with intermediate duration of breast feeding, whereas lower risks were found among those with very short or very long duration. For all nongenital cancers combined, decreased risks were observed among those with the longest duration of breast feeding. However, among cancers of specific sites, a significant inverse association was found for pancreatic cancer only. The overall impression given by our data is that breast feeding is not strongly related to risks of breast cancer or any other common cancer.

Breast Feeding↗

PubMed1985

Distribution of forced expiratory volume in one second and forced vital capacity in healthy, white, adult never-smokers in six U.S. cities.

As part of a longitudinal study of the respiratory health effects of air pollution, we measured the lung function of 2,454 white adults 25 to 74 yr of age who had never smoked and who reported no respiratory symptoms. These measurements were analyzed to develop a simple model for the cross-sectional dependence of pulmonary function on height, sex, and age. Both forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) can be effectively standardized for body size by dividing each pulmonary function measurement by the square of the standing height (HT2). The age-specific distribution of these standardized measurements is approximately Gaussian, with variance that is independent of age. Plots of FEV1/HT2 and FVC/HT2 against age showed a nonlinear relationship consistent with an increase in the rate of pulmonary function loss with age. On the basis of these graphic analyses, both pulmonary function measurements were fitted to a four-parameter normative model including sex and linear and quadratic terms in age as dependent variables. This model gave predictions that were very close to those from more complicated models currently in use. Predicted percentile levels were calculated for each sex and age, and shown to describe the observations well. The estimated annual change in height-standardized lung function based on the cross-sectional model was compared with the observed change between the first and second examinations of these adults 3 yr later. The observed changes were close to predicted values, except for subjects younger than 35 yr of age at their first examination. The observed change was larger for men than for women. Such simple longitudinal comparisons are subject to selection bias. In this study, subjects in the lowest quartile of FEV1/HT2 for their age and sex at the first examination had a lower probability of providing a lung function measurement 3 yr later.

Adult↗

PubMed2001

A new kinetic model for thermal inactivation of microorganisms: development and validation using Escherichia coli O157:H7 as a test organism.

A new kinetic model has been proposed to simulate the nonlinear behavior of survivor curves frequently observed in thermal inactivation of microorganisms. This model incorporates a time component into the first-order inactivation kinetics and is capable of describing the linear, convex, and concave survivor curves. The model was validated using Escherichia coli O157:H7 as a test microorganism. Ground beef (93% lean) samples inoculated to 10(7) to 10(8) CFU/g of meat were subjected to immersion heating at 55, 57.5, 60, 62.5, and 65 degrees C, respectively, in a water bath. All the survivor curves in this study showed upward concavity. Linear and nonlinear regressions were used to fit the survivor curves to the linear first-order inactivation kinetics and the proposed model. Analyses showed that the new kinetic model provides a much better estimate of the thermal inactivation behavior of E. coli O157:H7 in ground beef.

Animals↗

PubMed1999

[Non linear analysis of infection diseases dynamics in Chile].

BACKGROUND: The incidence of infectious diseases generally has large fluctuations, probably due to interactions between seasonal fluctuations and those secondary to case-susceptible host interactions. AIM: To analyze the complexity and attractant topological resemblance of seven infectious diseases in Chile. MATERIAL AND METHODS: The annual incidence of measles, whooping cough, scarlet fever, meningococcal meningitis, diphtheria, typhoid fever and poliomyelitis was obtained from the annual reports of diseases. Correlation dimensions and the largest Lyapunov series exponents were estimated. The resemblance among their attractants was assessed by Hausdorff distance. The measures were performed both before and after seasonal filtering. RESULTS: All series showed a dynamics near low dimensional chaos. The correlation dimensions ranged between 2.12 and 2.76. The correlation dimensions did not change after seasonal differentiation. Apart from one, all disease dynamics had large Lyapunov exponents, near 0.6 Bits/year. These decreased if series were differentiated. Before differentiation, the topological resemblance was mainly caused by the seasonal component of the dynamics but thereafter, the resemblance increased. In spite of different transmission mechanisms and etiologies, all analyzed infectious diseases conformed a truly single group, during cluster analyses. CONCLUSIONS: These results suggest that beneath the dynamics of infectious diseases, obscured by seasonal environmental factors, lays a very consistent nonlinear agent-susceptible host dynamics.

Chile↗

PubMed2006

The chaos and complexity of classic Hollywood cinema.

Classic Hollywood cinema, the standard narrative format for production of feature length films, seems at first glance one of the most linear, prescriptive methods of discourse. It centers the action on a main character and traces the resolution of a single, dominant problem. However, a close examination of the best films of this format shows that talented directors and actors use the predictability of this framework to anchor complex thematic explorations of the inherent ambiguity of the medium. Conventional, linear, cause and effect interpretive methods often fail to discern the multiple options for meaning inherent in these works because they lack the vocabulary to express these conditions. This essay explores how a critic can employ images from chaos and complexity theories to create metaphors that reach beyond the bounds of Cartesian thinking and enable far more sophisticated analyses of the films.

California↗

PubMed2005

Computational models for detection of erectile dysfunction.

PURPOSE: Vascular comorbidities are well known to correlate with erectile dysfunction (ED) but a correlation with hypogonadism and depression is less clear. Using several linear and nonlinear mathematical models we investigated the correlation of age, hypogonadism and depression with ED using the Sexual Health Inventory for Men (SHIM) as a surrogate marker for ED. MATERIALS AND METHODS: A data set of 140 exemplars containing the input features age, total testosterone in ng/dl, Center for Epidemiologic Studies Depression scale score and output SHIM score (thresholded to 10 for moderate ED) was randomized into a modeling (training) set of 105 and a cross-validation (test) set of 35 with similar outcome frequencies preserved in each set. Using neUROn++, a set of C++ programs that we developed using the Cygwin (Red Hat, Raleigh, North Carolina) GNU C++ port for Windows (Microsoft, Redmond, Washington) distributed across Pentium (Intel, Santa Clara, California) platforms we modeled the data set using the linear methods, linear and quadratic discriminant function analysis, and logistic regression, and the nonlinear method of neural computation with several investigated architectures. RESULTS: A 4 hidden node network was found to have the highest accuracy compared to linear and quadratic discriminant function analyses, and logistic regression. ROC areas for the test set were 0.702, 0.645, 0.676 and 0.618, respectively. Analysis of the neural network demonstrated that moderate ED correlated with patient age and depression score. Forward and reverse regression of the neural network based on Wilk's generalized likelihood ratio test revealed that age was most significant (p <0.001), followed by Center for Epidemiologic Studies Depression Scale score (p <0.03), followed by testosterone (p >0.6). CONCLUSIONS: We investigated linear and nonlinear computational models of moderate ED. To our knowledge this is the first demonstration that SHIM correlates with age and a depression metric. Furthermore, moderate ED based on SHIM with a correlation with age may now provide a rationale and basis for future investigation into the understanding of age related erectile pathophysiology.

Adult↗

PubMed1996

Action profiles of predictors of death and survival time in stage I malignant melanoma.

BACKGROUND: Many studies have been performed to identify prognostic factors of malignant melanoma using multivariate regression models. In these models, it is generally assumed that quantitative predictors such as age or tumor thickness enter linearly into the model, or they are categorized. OBJECTIVE: The purpose of the present study is to investigate possible curvature (nonlinearity) of predictors of 'death from MM within 5 years after diagnosis' and 'survival time after diagnosis' avoiding the known shortcomings of categorizing predictors. METHODS: Our analyses are based on data of 677 patients with stage I melanoma of the skin collected at the Cancer Registry of the Canton of Zurich. In order to study non-linearity of predictors, we use 'generalized additive models' (GAM): in a GAM the usual prognostic index is replaced in an optimal way by a more flexible form where the individual linear terms are replaced by possibly curved functions of the predictors. Plotting the corresponding curves (the 'action profiles') allows one to visualize easily the shape by which predictors 'act' over the whole range of values. RESULTS: Essentially the same results emerged when studying 'death from melanoma' and 'survival time in melanoma': age and tumor thickness have a pronounced nonlinear association with both endpoints taking simultaneously into account effects of sex and tumor site. The action profile for age is J or U shaped. The action profile for thickness has a 'two-phase' pattern. It increases linearly for low thickness values and flattens for higher values. The shape of the action profiles was checked by performing a Monte Carlo simulation ('boot-strapping'). CONCLUSIONS: The best prognosis of melanoma was found within a middle age range while younger and older patients showed a poorer prognosis. In our data, the increase in thickness in the range above 2 mm is of much less clinical relevance than in the range below 2 mm. GAMs may be of great value for clinicians in providing a visualization of the shape by which predictors act and to obtain a better understanding of the complex relationships between predictors and survival. Not considering curvature of action profiles may result in excluding relevant predictors.

Adult↗

PubMed1976

A review of the satatistical considerations involved in the treatment of isotope dilution calibration data.

The use of linear regression analysis for the reduction of isotope dilution data is reviewed. The calculation of linear regression statistics is based upon four assumptions: zero variance in the independent variable, equal variance for all values of the dependent variable, linearity and continuity. Unfortunately, isotope dilution data often violate one or more of these assumptions, which results in the calculation of an inaccurate calibration line. The inaccuracies can be avoided through careful inspection of the data, including analyses of variance and linearity. Large differences in the variances of the dependent variable require the use of a weighted linear regression. Nonlinearity necessitates either discarding data in the nonlinear portion of the calibration or the calculation and use of atom % excess and dilution instead of the sample isotope ratios.

Mass Spectrometry↗

PubMed1996

A complex interaction between topical verapamil and timolol on intraocular pressure in conscious rabbits.

Calcium channel blockers have complex actions on aqueous humour dynamics that seem to depend on the route of drug administration. When applied topically, verapamil and nifedipine effectively lower intraocular pressure. However, these drugs also produce a slight reduction in aqueous humor outflow through the trabecular meshwork whereby they could modify the effect of other drugs on intraocular pressure. As calcium channel blockers could be effective in the management of ocular hypertension and low-tension glaucoma, the aim of the present work was to assess the interaction between verapamil and timolol when both drugs are topically applied to the eye of albino rabbits. Intraocular pressure was measured with a manual applanation tonometer. The effects of 5-6 different doses of each drug alone and the effects of five mixtures of both drugs at fixed concentration ratios (timolol: verapamil 4:1, 2:1, 1:1, 1:2 and 1:4) were evaluated. After measuring baseline intraocular pressure, one 50 microliters drop of the different solutions was instilled in the left eye. Measures of the intraocular pressure were repeated at intervals of 30 min until the maximal effect was reached. Each set of experiments was carried out in a group of 9-11 rabbits. Dose-response curves were fitted with a nonlinear regression microcomputer programme. The median effect plot was constructed as proposed by Chou and Talalay (1981, 1983, 1984). In order to analyse the nature of the interaction between both drugs, the observed effect was compared with the theoretically expected one and the combination indices, that relate the doses of verapamil and timolol present in the mixtures with the doses of both drugs separately which are equieffective with the combination, were calculated. The effects of verapamil and timolol followed the principle of the mass action law when administered alone. Nevertheless, no adequate dose-response relationship was obtained when the mixtures of both drugs were applied. In general, the observed effects were lower than the expected ones. Combination indices also indicate the presence of antagonism, except for the lowest concentrations of mixtures where verapamil predominates. In this case, combination indices suggest summation of effects or synergy. Both drugs seem to decrease intraocular pressure by reducing aqueous humor secretion through different mechanisms. However, due to the reduction of aqueous humor outflow caused by verapamil, the ocular hypotensive effect of timolol may be antagonized when high doses of verapamil are administered.

Administration, Topical↗

PubMed2004

Spectrally resolved femtosecond 2-colour 3-pulse photon echoes: a new spectroscopic tool to study molecular dynamics.

We present a new multidimensional femtosecond spectroscopy technique based on spectrally resolved 2-colour 3-pulse photon echoes for investigating molecular dynamics in a variety of systems including proteins. In this technique the sample is illuminated by two femtosecond 'pump' pulses with wave vectors k1, k2 and wavelength lambda(pump) and a femtosecond 'probe' pulse with wave vector k3 and wavelength lambda(probe). Nonlinear signals are generated in the phase-matching directions k4 = - k1 + k2 + k3 and k6 = - k3 + k1 + k2. These signals are analysed in spectrometers equipped with CCD detectors and the spectra of the signals are recorded for various values of (i) the delay t12 between pulses 1 and 2, (ii) the delay t23 between pulses 2 and 3, and (iii) the wavelengths lambda(pump), lambda(probe). The technique has been used for studying vibrational and electronic dynamics of dye molecules, such as cresyl violet in methanol, and ultra-fast transient processes that occur during the photo-dissociation of carbonmonoxy myoglobin (MbCO) into myoglobin (Mb) and CO.

Algorithms↗

PubMed1999

Evaluation of the angiotensin challenge methodology for assessing the pharmacodynamic profile of antihypertensive drugs acting on the renin-angiotensin system.

AIMS: The performance of the experimental paradigm of angiotensin challenges with continuous non-invasive blood pressure measurement was evaluated. Angiotensin dose-response relationships were characterized, along with the influence of clinical covariates. The stability of angiotensin-induced peaks and the variability of the angiotensin doses were assessed. Finally, the predictive value of studies based on angiotensin challenges to determine drug doses effective in therapeutics was evaluated. METHODS: The data were gathered from 13 clinical studies on nine angiotensin II receptor antagonists, one ACE inhibitor and one dual ACE-NEP inhibitor, using Finapres for measuring the response to exogenous angiotensin challenges. Modelling of angiotensin dose-response curves and determination of the inter and intrasubject variability were performed by nonlinear regression (NONMEM). The different sources of variations in angiotensin I and II doses and angiotensin-induced peaks were evaluated by analyses of variance. The dose of ACE inhibitors and angiotensin II receptor antagonists inhibiting blood pressure increase by at least 75%, as measured by this method, was chosen for comparison with the labelled starting dose. RESULTS: Angiotensin challenges exhibited a clear dose-response relationship which can be characterized both by an Emax or a log linear model. The log linear model gave an average systolic/diastolic response of 24+/-6/20+/-5 mmHg for a unit dose of 1 microgram of angiotensin II equivalents, and an increase of 6/6 mmHg for each doubling of the dose. The angiotensin ED50 calculated values were 0.67 microgram for systolic and 0.84 microgram for diastolic blood pressure. The angiotensin doses for eliciting a given response and the angiotensin induced peaks were fairly constant between period and subject, but vary significantly between studies. Based on an inhibition of blood pressure by 75%, the agreement was good between the doses of ACE inhibitors and angiotensin receptor antagonists predicted from studies using the methodology of angiotensin challenges and the doses shown to be clinically efficacious, in spite of high intersubject and intrasubject variabilities. CONCLUSIONS: This experimental method represents a valid surrogate for the therapeutic target and a useful tool for the pharmacokinetic and pharmacodynamic profiling of drugs acting on the renin-angiotensin system.

Angiotensin II↗

PubMed1999

Pharmacokinetics of ketorolac after intravenous and oral single dose administration in dogs.

The pharmacokinetics of ketorolac (Toradol), a human non-narcotic, nonsteroidal anti-inflammatory drug (NSAID) of the pyrrolo-pyrrole group, was studied in six mixed breed dogs of varying ages (1-5 years). The study was performed using a randomized crossover design, with each dog initially assigned to one of two groups (intravenous (i.v.) or oral (p.o.)). Each group of three dogs received either the injectable or oral formulation of ketorolac tromethamine at 0.5 mg/kg. Serial blood samples were collected before and over 96 h following treatment. Samples were analysed by reverse phase HPLC. Individual ketorolac plasma concentration-time curves were initially evaluated by computerized curve stripping techniques followed by nonlinear least squares regression. Following i.v. administration mean (+/- SD) pharmacokinetic parameters were: elimination half-life (t1/2 beta) = 4.55 h, plasma clearance (Clp) = 1.25 (1.13) mL/kg/min, and volume of distribution at steady state (Vss) = 0.33 (0.10) L/kg. Mean (+/- SD) p.o. pharmacokinetic values were: t1/2 beta = 4.07 h, time to reach maximum concentration (tmax) = 51.2 (40.6) min, and p.o. bioavailability (F) = 100.9 (46.7)%. These results suggest that the pharmacodisposition characteristics of a clinically effective 0.5 mg/kg i.v. or p.o. single dose of ketorolac tromethamine administered to dogs is fairly similar to that observed in humans.

Administration, Oral↗

PubMed1999

Characteristics of transient evoked otoacoustic emissions in normal-hearing and hearing-impaired children.

OBJECTIVE: Transient evoked otoacoustic emissions (TEOAEs) were measured in children with normal hearing and in children with hearing loss to investigate the characteristics of TEOAEs as they relate to overall amplitude and amplitude spectra of evoking stimuli, and to audiometric status. DESIGN: Three parameters of response measure (signal to noise ratio, amplitude and reproducibility) were assessed to determine accuracy of identification of varying degrees of hearing loss for broadband clicks, frequency-specific click bands and tone bursts. Forty-four children (66 ears) between 4 and 13 yr of age were evaluated for participation in the study. Fifty-nine ears with intact tympanic membranes were included in the final analyses: 14 ears with normal hearing and 45 ears with hearing loss. RESULTS: Children with normal hearing had robust responses that displayed nonlinear growth functions for broadband clicks and for tone bursts. Children with hearing loss had responses that decreased rapidly with decreasing stimulus level, if emissions were present at all. Data were analyzed using clinical decision analysis and receiver operator characteristic curves. Broadband clicks presented at 80 and 86 dB peSPL identified a hearing loss > or = 30 dB HL with a high degree of accuracy. Click responses filtered into octave bands centered at 500 and 1000 Hz did not improve classification of hearing loss, in fact, the 500 Hz band was particularly inaccurate. Results for click responses filtered into half-octave bands centered at 2000 and 4000 Hz were comparable with those for the broadband click, although the 2000 Hz band was superior for identification of hearing loss > or = 20 dB HL for an 80 dB peSPL click, and > or = 30 dB HL for an 86 dB peSPL click. Results for tone bursts centered at 500, 1000, 2000 and 4000 Hz, presented at 80 dB peSPL, were similar to results of the filtered click bands. Accuracy for identifying hearing loss increased with increasing center frequency. The 2000 and 4000 Hz tone bursts provided the best separation between normal-hearing and hearing-impaired ears, with 4000 Hz being slightly better. CONCLUSIONS: Data from this study suggest that TEOAEs in children can separate ears with normal hearing from those with hearing loss using a variety of stimulus and response conditions. Moreover, by using multiple stimulus levels it may be possible to distinguish between mild and moderate hearing losses.

Acoustic Stimulation↗

PubMed2004

Footedness across the age span among Brazilian right- and left-handers.

Previous cross-sectional surveys have reported a decreasing prevalence of left-footedness with increasing age. Bell and Gabbard attributed this pattern to a developmental process wherein the right hemisphere ages earlier than the left, leading to a decline in left-footedness among older individuals. A major flaw in this hypothesis is that age-related data were derived exclusively from right-handed samples. To test the generality of the hypothesis we obtained foot preferences from 1462 right and 172 left-handed Brazilians ranging from 10 to 94 years of age. In only one of the three analyses did dextrals show the predicted age-related decline. Together with accelerating trends towards left-footedness among older males and nonlinear trends among left-handers as a group, these results do not sustain the basic assumptions implicit in the right hemisphere aging hypothesis.

Adolescent↗

PubMed1998

Body composition and energy utilization by steers of diverse genotypes fed a high-concentrate diet during the finishing period: II. Angus, Boran, Brahman, Hereford, and Tuli sires.

Objectives of the study were to determine the influence of Angus (A), Boran (BO), Brahman (BR), Hereford (H), or Tuli (T) sires on body composition, composition of gain, and energy utilization of crossbred steers during the finishing period. Beginning at 300 kg, 96 steers were adjusted to a high-corn diet and individual feeding. Steers were assigned, by sire breed, to be killed as an initial slaughter group or fed either a limited amount or ad libitum for 140 d then killed. Organ weights, carcass traits, and body composition were evaluated. The statistical model included sire breed (S), treatment (Trt), and the S x Trt interaction. Ad libitum feed intake was least for BO- and T-, intermediate for BR- and H-, and greatest for A-sired steers. Rates of weight, fat, and energy gains were similar for A-, H-, and BR-sired steers but less (P < .01) for BO and T when fed ad libitum. Rates of protein or water gains did not differ among sire breeds (P > .12). Rates of water, fat, and protein gain increased linearly with increased rate of BW gain, but relationships differed (P < .05) among sire breeds. Linear regression analyses indicated energy requirements for maintenance and efficiency of energy use for energy gain differed (P < .05) among sire breeds. Evaluation by nonlinear regression indicated that heat production increased exponentially and energy gain increased asymptotically as feed intake increased above maintenance.

Animal Feed↗