Simulation of cow-calf production with and without realistic levels of variability.

The Colorado beef cattle production model, a whole-herd, individual-animal, life-cycle simulation model, was used to determine if level of simulated variability affects simulation results. Beyond variability created by deterministic equations describing known biological relationships and direct input, the Colorado beef cattle production model can produce additional variation in a number of traits through its capacity to generate multinormal deviates for each animal. Runs simulating cow-calf production under ample and sparse levels of nutrition were performed with less than realistic and realistic levels of variability for mature weight, milk production, gestation length, maintenance requirements, appetite, and combinations thereof. Under poor nutrition, simulation with less than realistic variability altered means for pregnancy rate, postpartum interval, milk production, weaning weight, and mature weight by up to 14%, 8.6 d, 0.8 kg/d, 9.6 kg, and 19.1 kg, respectively, in addition to changing the output for numerous other variables. The level of simulated variability affected the means of output variables through 2 mechanisms: (1) change in potentials due to differential culling, which can only take place if potentials are allowed to vary; and (2) further interaction with the model's nonlinear, deterministic equations. Our findings indicate that by not simulating realistic levels of variability, models with nonlinear functions may yield misleading results.

Repeated-measure animal models to estimate genetic components of mature weight, hip height, and body condition score.

Information on mature weight, hip height, and body condition score from Angus cows was analyzed to estimate variance components and compare prediction models. Observations from repeated measures were analyzed with animal models with or without condition score as a covariate and with or without an effect for permanent environment. Heritability (repeatability) estimates for mature weight, hip height, and condition score from Method R procedures were 0.40 (0.77), 0.62 (0.81), and 0.11 (0.38), respectively, from animal models containing a permanent environmental effect but without a covariate for condition score. Heritability estimates from animal models without a permanent environmental effect were similar to repeatability estimates from animal models with it, suggesting inflated estimates of genetic variance from models not containing a permanent environmental effect. Regressing mature weight on condition score reduced both additive genetic variance and permanent environmental variance, increasing the heritability estimate of mature weight to 0.54 and altering the biological interpretation of the trait. The covariate for condition score had little effect on hip height. Regressions of mature weight and hip height on condition score were 25.9 kg/unit of body condition score and 0.4 cm/unit, respectively. Least-squares means for mature weight and hip height tended to increase until 7 and 5 yr of age, respectively. Condition score tended to increase until 6 yr of age and decrease after 8 yr of age. Correlations between breeding value solutions for the same trait were high whether or not prediction models included a permanent environmental effect or a covariate for condition score, and whether or not the variance components used were derived from models containing a covariate for condition score. Results suggest the importance of including a permanent environmental effect in genetic prediction models for these traits. Whether mature weight should be adjusted for body condition is arguable, depending on availability of condition score predictions and tools for analyzing mature weight and condition score predictions in an environment-specific context.

Additive genetic relationships between heifer pregnancy and scrotal circumference in Hereford cattle.

The objective of this study was to determine an appropriate method for using yearling scrotal circumference observations and heifer pregnancy observations to produce EPD for heifer pregnancy. We determined the additive genetic effects of and relationship between scrotal circumference and heifer pregnancy for a herd of Hereford cattle in Solano, New Mexico. The binary trait of heifer pregnancy was defined as the probability of a heifer conceiving and remaining pregnant to 120 d, given that she was exposed at breeding. Estimates of heritability for heifer pregnancy and scrotal circumference were .138+/-.08 and .714+/-.132, respectively. Estimates of fixed effects for age of dam and age were significant for heifer pregnancy and bull scrotal circumference. The estimate of the additive genetic correlation between yearling heifer pregnancy and yearling bull scrotal circumference was .002+/-.45. Additional analyses included models with additive genetic groups for scrotal circumference EPD for heifer pregnancy or heifer pregnancy EPD for scrotal circumference to account for a potential nonlinear relationship between scrotal circumference and heifer pregnancy. Results support the development of a heifer pregnancy EPD because of a higher estimated heritability than previously reported. The development of a heifer pregnancy EPD would be an additional method for improving genetic merit for heifer fertility.

Shortcomings of current genetic evaluation systems.

Genetic evaluation, as the term is used today in the beef cattle and sheep industries, refers to the calculation and dissemination of genetic predictions for individual traits. If genetic predictions are to be used wisely, however, genetic evaluation should be broadened to include multiple-trait selection technology, preferably technology that is customized for individual commercial and seedstock producers. Most of the recent research in the area of genetic prediction/multiple-trait selection has focused on the use of economic selection indexes that incorporate genetic predictions produced within breeds. This approach is complicated by genotype x genotype, genotype x environment, and more complex interactions, and the changing correlations they create. The use of a mechanistic technology, bioeconomic simulation, to calculate economic weights can avoid some of the problems caused by interactions, but to implement this technology, academic animal breeders must accept the mechanistic concept of genetic potential and devise ways to translate current within-breed genetic predictions to predictions of this new measure. Sire selection by simulation, a multiple-trait selection technology described in detail in this article, uses bioeconomic simulation in a way that offers advantages over traditional selection indexes in terms of both functionality and appeal. For any customized technology to be applied on a meaningful scale, research priorities must change, and the business relationships between research groups and animal breeding industries must be restructured.

The effect of selective reporting on estimates of weaning weight parameters in beef cattle.

The effect of selective reporting on estimates of weaning weight parameters in beef cattle was evaluated by comparing REML estimates from unaltered and altered simulated data. Selective reporting reduced estimates of weaning weight direct (WWD), maternal milk (MAT), and error variances. However, heritability estimates were not greatly affected because the reductions in variance estimates were relatively proportionate. When the true value for the direct-maternal (DM) correlation was zero or negative, selective reporting caused estimates of DM to be less positive or more negative in 50 of 62 comparisons, with an average change of -.136. When the true value for DM was positive, selective reporting increased the positive magnitude of DM estimates in 12 of 20 comparisons, with an average change of +.040. In BLUP of unaltered data with a true DM value of -.09, using a -.28 and a zero DM correlation reduced the correlation of MAT EPD with true values .065 and .041, respectively. These results suggest that the reliability of parameter estimates (and BLUPs) would be improved by estimating parameters from representative subsets of data free of reporting bias.

Within-herd genetic analyses of stayability of beef females.

Nonlinear mixed-model procedures for analysis of binary data were used to estimate heritability (h2), predict individual genetic merit, and determine genetic and environmental trends for four measures of stayability of beef females. Traits considered were probabilities of a female having 2 [S(2/1)], 5 [S(5/1)], 8 [S(8/1)] and 11 [S(11/1)] calves, given that she calved once. Colorado State University Beef Improvement Center (BIC) and Beckton Stock Farm (BSF) provided data for the analyses. Heritability was estimated using animal model marginal maximum likelihood (AM MML), sire model marginal maximum likelihood (SM MML), and animal model Method R (AM MR). Individual genetic merit was predicted using single-trait animal models with each h2 estimate. Birth year was treated as fixed in all analyses. Only AM MML yielded h2 estimates for all traits in both herds. The AM MML h2 estimates for S(2/1), S(5/1), S(8/1), and S(11/1) were .09, .11, .07, and .20, respectively, for BSF data and .02, .14, .09, and .07, respectively, for BIC data. Differing h2 estimates did not substantially influence rank of individual predictions. Genetic trends in stayability were positive in both herds, although birth year solutions indicated variable or negative environmental trends. Genetic improvement of stayability may be accelerated by incorporating predictions of genetic merit for stayability in selection criteria. S(5/1) may be the most useful trait for consideration in national cattle evaluations.

Additive genetic groups for animals evaluated in more than one breed association national cattle evaluation.

Additive genetic groups were included in the 1993 Red Angus Association of America national cattle evaluation for phantom parents of individuals who were registered with the American Angus Association (AAA). Genetic groups were formed for each component in two multiple-trait evaluations in which all animal effects were fit. Additive direct effects were included for birth weight, weaning weight (WW), and milk (MILK). In a second analysis the additive direct effect of 160-d postweaning gain was analyzed with WW and MILK. Of the 387,665 animals, 50,838 had at least one phantom parent assigned to one of five genetic groups fit as fixed effects for each additive component. Of these 50,838 animals, 1,324 were identified as registered with the AAA. An average of 906 animals per component had an AAA EPD available. Animals with a known AAA EPD were designated into one of three groups of equal numbers based on AAA EPD for each component (1 = low, 2 = medium, 3 = high). Animals in the fourth genetic group were those registered with the AAA but with no EPD available for the component. The fifth genetic group included all other animals with phantom parents. Grouping on AAA EPD allowed for EPD on animals out of parent(s) registered with the AAA to be more closely aligned to the AAA EPD because they were regressed from the group solution instead of zero. Grouping based on EPD from another NCE should be considered in the production of multibreed EPD.

Method R variance components procedure: application on the simple breeding value model.

An algorithm for estimating variance components (Method R) based on the linear regression coefficient (R) of recent (more accurate) on previous (less accurate) individual genetic predictions is presented. The previous prediction is obtained by analyzing a subsample of the whole data set. First raw moment of R equals 1 regardless of the distribution of observations and predictions. A condition such as the use of inappropriate variance components ratio (VC) can cause this regression to deviate from its expectation. If the computed R (Rc) is greater than 1, then VC ratio has been underestimated, and if Rc is less than 1, then VC ratio has been overestimated. Several iterations are performed, changing the VC ratio at each iteration, until Rc approximately equal to 1. When an Rc is obtained that is acceptably close to 1 (precision is reached), then the appropriate VC has been used. Method R does not require computation of the inverse of the coefficient matrix and has desirable properties of convergence, precision, and computing feasibility. Additional sampling variance in the estimate of VC is expected due to the requirement of taking a subsample of the entire data set to obtain the lower accuracy predictions. This sampling variance is shown to be small for simulated datasets of size n = 10,000 with no selection.

A rapid spectrophotometric blood cyanide determination applicable to emergency toxicology.

Cyanide determination in whole blood can be performed by spectrophotometry after using diffusion coupled with coloration by hydroxocobalamin in a Conway dish. The technique may be accelerated by the use of a heating sheet at 45 degrees C. The method proved to be specific, sensitive, and fast, thus permitting measurements in emergency situations.

Technical note: detection of bias in genetic predictions.

The theoretical development of a procedure to detect bias in genetic predictions is presented. The procedure is based on the expectation of three statistics. These statistics detect bias by identifying systematic, unexpected change in subsequent analyses. Expectations of the following statistics were obtained: linear correlation coefficient between subsequent predictions, linear regression of recent (more accurate) on previous (less accurate) genetic prediction, and variance of the genetic prediction difference (recent minus previous genetic prediction). Deviations from these expectations can be used to indicate bias. The covariance between subsequent BLUP of genetic value is shown to equal the variance of the early estimate, implying that the expected value of the regression of recent on previous genetic prediction equals 1 regardless of the distribution of the observations and predictions. Also, the expected value of the linear correlation coefficient between subsequent genetic predictions equals the square root of the ratio of the means of the square of accuracy values. The expected value of the variance of the genetic prediction difference was shown to be equal to the difference between prediction error variances.

Relationship of maternal milk expected progeny differences to actual milk yield and calf weaning weight.

Calf weaning weights and estimates of 205-d milk yield (n = 317) were obtained from 90 Polled Hereford (PH) and 80 Simmental (SM) cows to evaluate the relationship of these measures with maternal milk and total maternal EPD from national cattle evaluations. An inverse parabolic exponential function predicted 205-d milk yields for each cow from five estimates of daily milk yield taken once per month via calf weigh-suckle-weigh. Changes in calves' 205-d adjusted weights were greater than predicted (P < .02) by maternal milk EPD of PH and SM dams and PH maternal grandsires (MGS) but were similar to changes predicted by SM MGS (P > .50). These changes were also greater than those predicted by total maternal EPD of PH dams and MGS (P < .02) but were similar to those predicted in SM dams and MGS (P > .38). Interactions of maternal milk and total maternal EPD with sex of calf and year did not influence calves' 205-d adjusted weights (P > .10). A positive relationship was found in both breeds between 205-d milk yield EPD (calculated from 205-d milk yield estimates) and maternal milk EPD from national cattle evaluations. Objectively assessing the magnitude of this relationship was hindered by problems in estimating heritability and interpreting correlations between EPD. These data indicate that maternal milk and total maternal EPD from national cattle evaluations are reasonably good predictors of genetic differences in milk yield and weaning weight.

Genetic effects on beef heifer puberty and subsequent reproduction.

Significant genetic variation exists within and between breeds of beef cattle for age at puberty (AP). In general, faster-gaining breed groups of larger mature size reach puberty at a later age than do slower-gaining breed groups of smaller mature size; breeds selected for milk production reach puberty at younger ages than do those breeds not selected for milk production. Heterosis, independent of heterosis effects on weight, influences most measures of puberty in females and scrotal circumference (SC) in males. Crossbred heifers reach puberty at younger ages and heavier weights than their straightbred counterparts. Scrotal circumference has been shown to be an excellent indicator of AP in yearling bulls. Furthermore, a favorable genetic relationship exists between SC in bulls and AP of female offspring. Beef cattle breeders may take a direct approach to breeding for AP and subsequent reproduction by directly selecting for measures of fertility such as SC. However, an indirect approach, involving selection for an array of traits that provide an appropriate "genetic environment" for the expression of fertility (i.e., size, milk production, calving ease) may be preferred. Although seedstock producers are limited to making change through within-breed selection, commercial producers can take advantage of both within- and between-breed selection as well as crossbreeding to achieve the same goal.

High cardiac zinc levels in spontaneously hypertensive rats.

OBJECTIVES: Higher cardiac zinc levels have been observed previously in spontaneously hypertensive rats (SHR) compared with Wistar-Kyoto (WKY) rats. However, this difference was established in adult males only and needed to be confirmed on a larger number of animals of both sexes. We also explored the respective roles of genetic and environmental factors in the genesis of this zinc anomaly as well as the causal relations with hypertension. DESIGN: Cardiac zinc levels were determined in adult male and female SHR and WKY rats originating from various colonies and submitted to various experimental conditions (anaesthesia, stress). These determinations were also performed in 3-week prehypertensive SHR and in adult Wistar rats submitted or not to deoxycorticosterone acetate-salt-induced hypertension. METHOD: Zinc levels were measured by flame atomic absorption spectrophotometry. RESULTS: In adults, cardiac zinc content was significantly higher in SHR than in WKY rats irrespective of sex and experimental conditions. In young prehypertensive rats, the difference between SHR and WKY cardiac zinc levels was also very significant. Experimental hypertension induced in Wistar rats did not entail any significant rise in cardiac zinc levels. CONCLUSIONS: These findings indicated that the higher cardiac zinc of SHR is not secondary to blood pressure elevation. High erythrocyte zinc, previously described in SHR, together with the present data suggest the occurrence of a primary genetic defect leading to high intracellular zinc in SHR. The possible role of this zinc anomaly in the development of hypertension and/or cardiac hyperplasia is discussed.

Continuous flow quantification of total mercury in whole blood, plasma, erythrocytes, and urine by inductively coupled plasma atomic emission spectroscopy.

Mercury determination in blood and urine can be performed by inductively coupled plasma atomic emission spectroscopy (ICPAES) after dilution in an ammonia buffer and reduction by sodium borohydride. The proposed method does not need an oxidative mineralization. The sample is not nebulized into the torch, but the mercury vapor, after collection in a reactor vial, is swept into the plasma by the argon carrier gas using the described glass apparatus.

[Intraperitoneal chemotherapy for ovarian adenocarcinoma: pharmacokinetics of cisplatin]. / Chimiothérapie intrapéritonéale pour adénocarcinome ovarien: pharmacocinétique du cisplatine.

Chemotherapy using cis dichlorodiamine platinum (CDDP) in doses of 30 and 60 mg/m2 was carried out in 6 patients who had adenocarcinoma of the ovary, that had not been treated before, 15 to 120 minutes before surgery was carried out. The results of doses of platin given on the blood levels are demonstrated. A slight and progressive increase in the plasma levels of CDDP with peaks between 0.6 and 1.95 of total platinum and 0.22 mcg/ml of free platin were found. The tissue levels in the region of the ovaries were found to be between 0.16 and 0.94 mcg/mg. There was a stepwise increase in the levels found in the pathological peritoneal cover of between 0.42 and 31.2 mcg/mg. This dropped as time went by; and then led to change in accordance with the intra-peritoneal concentrations. This study shows that it is possible when giving drugs intraperitoneally to avoid high plasma peaks and to obtain good levels of concentration of cisplatin in the peritoneum.

Diverse biological parameters in clinically healthy sheep from a flock with scrapie: variations, and correlations with OLA antigens.

A comparison was made in the blood levels of various cell types and biochemical substances and in lymphocyte antigens between 107 healthy sheep from a flock contaminated with scrapie (HC sheep) and 93 sheep from a noncontaminated flock (NC sheep), which served as a control population. Significant differences between the two groups of sheep were found in some of the levels, as had previously been found with lymphocyte antigens. The HC sheep, which included genetically resistant animals, could be distinguished from the NC sheep by their lower levels of various white cells, a noticeable decrease in urea, a moderate decrease in Mg2+ and Mn2+ ions, beta- and gamma-globulins, serotonin and vitamin B12, a strong increase in uric acid and a moderate increase in K+, Cl-, HCO3-, Zn2+, and Al3+ ions, as well as in total lipids and in the albumin to globulin ratio. In this HC population, the only enzyme with an increased level was aldolase; the levels of the other 7 enzymes measured were lowered. The observed modifications were considered to be signs of latent disturbances in the leukocyte system and in hepatic and renal functions, in spite of apparent resistance. Eleven lymphocyte antigens were studied. These antigens are not independent of the blood levels of the various substances measured, but are often correlated in a statistically significant manner with some of them. In the HC sheep, the lymphocyte antigens correlated with the modified levels in the blood were different from those in the control population.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated blood cyanide concentrations in victims of smoke inhalation.

BACKGROUND: The nature of the toxic gases that cause death from smoke inhalation is not known. In addition to carbon monoxide, hydrogen cyanide may be responsible, but its role is uncertain, because blood cyanide concentrations are often measured only long after exposure. METHODS: We measured cyanide concentrations in blood samples obtained at the scene of residential fires from 109 fire victims before they received any treatment. We compared the results with those in 114 persons with drug intoxication (40 subjects), carbon monoxide intoxication (29 subjects), or trauma (45 subjects). The metabolic effect of smoke inhalation was assessed by measuring plasma lactate at the time of admission to the hospital in 39 patients who did not have severe burns. RESULTS: The mean (+/-SD) blood cyanide concentrations in the 66 surviving fire victims (21.6 +/- 36.4 mumol per liter, P less than 0.001) and the 43 victims who died (116.4 +/- 89.6 mumol per liter, P less than 0.001) were significantly higher than those in the 114 control subjects (5.0 +/- 5.5 mumol per liter). Among the 43 victims who died, the blood cyanide concentrations were above 40 mumol per liter in 32 (74 percent), and above 100 mumol per liter in 20 of these (46 percent). There was a significant correlation between blood cyanide and carbon monoxide concentrations in the fire victims (P less than 0.001). Plasma lactate concentrations at the time of hospital admission correlated more closely with blood cyanide concentrations than with blood carbon monoxide concentrations. Plasma lactate concentrations above 10 mmol per liter were a sensitive indicator of cyanide intoxication, as defined by the presence of a blood cyanide concentration above 40 mumol per liter. CONCLUSIONS: Residential fires may cause cyanide poisoning. At the time of a patient's hospital admission, an elevated plasma lactate concentration is a useful indicator of cyanide toxicity in fire victims who do not have severe burns.

A performance programmed method for computing inbreeding coefficients from large data sets for use in mixed-model analyses.

Coefficients of inbreeding are commonly used in mixed-model methods for forming inverses of Wright's numerator relationship matrix and transformation matrices used in variance component estimation and national cattle evaluation. Computation of exact coefficients of inbreeding from very large data sets has been believed to be too expensive or too difficult a task to perform. Approximate methods have been used instead. The effects of using approximation methods for inbred data that appear in national cattle data sets are demonstrated. An algorithm is given for the computation of inbreeding coefficients for large data sets. The algorithm feasibly computes inbreeding coefficients for large data sets even on small computing architectures.

Tissue and blood magnesium levels in spontaneously hypertensive rats, at rest and in stressful conditions.

Magnesium (Mg) levels were measured by flame atomic absorption spectrophotometry in the blood (plasma, erythrocytes) and soft tissues (liver, brain, heart, aorta, kidneys, adrenals, spleen, thymus) of adult spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar Kyoto (WKY). In experiment 1, Mg determinations were performed on eight animals of each strain at rest. Mg levels were lower in brain (P less than or equal to 0.05), kidneys (P less than or equal to 2.10(-4] and erythrocytes P less than or equal to 0.01) in SHR than in WKY rats. Tissue water content was the same in the two strains. These results suggest the occurrence of lower intracellular Mg levels in SHR than in WKY. In experiment 2, 15 SHR and 15 WKY were submitted either to acute (1 d) or subacute (22 d) stresses or reared in restful conditions. Acute stress induced important Mg shifts leading to a decreased difference between SHR and WKY in most tissues and to an increased and more significant difference (P less than or equal to 0.01) in spleen and plasma Mg levels. Subacute stress was milder and had little effect. It is concluded that the results of experiment 1 cannot be attributed to the greater sensitivity of SHR to laboratory manipulations. When compared with previously published data our results nevertheless suggest an association between stress sensitivity and genetic factors regulating Mg metabolism.

Hemodynamic effects of hydroxocobalamin in conscious dogs.

Hydroxocobalamin has been shown to be a rapid and powerful antidote in acute cyanide poisoning and to prevent cyanide poisoning during sodium nitroprusside administration. However, its hemodynamic effects remain unknown. The authors therefore investigated the effects in chronically instrumented conscious dogs (n = 8) that were randomly given hydroxocobalamin (20, 70, and 140 mg.kg-1) or saline. Determination of peak cobalt plasma concentrations showed that 20 and 70 mg.kg-1 hydroxocobalamin correspond to "therapeutic doses," whereas 140 mg.kg-1 corresponds to a supratherapeutic dose. Hydroxocobalamin did not modify heart rate, mean arterial pressure, left ventricular (LV) end-diastolic pressure, and PR and QT intervals, regardless of the dose administered. The largest dose (140 mg.kg-1) induced a decrease in the maximum increase of LV pressure (-7 +/- 3%; P less than 0.05), maximum aortic blood flow acceleration (-17 +/- 5%; P less than 0.05), and cardiac output (-19 +/- 6%; P less than 0.05), whereas systemic resistance increased (+41 +/- 9%; P less than 0.05). In six other dogs, local administration of hydroxocobalamin (0.5, 1.5, and 5.0 mg.kg-1.min-1) confirmed that, in large doses, this drug has direct vasoconstrictor properties affecting both conductance (decrease in iliac artery diameter: -2.5 +/- 0.8%) and resistance (decrease in iliac artery blood flow: -19.5 +/- 3.4%) vessels. Thus, hydroxocobalamin should be a safe cyanide antidote, considering the lack of hemodynamic effects within the therapeutic range of doses.