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Thirty Hereford steers were finished either on pasture (n=10) or concentrate (n=20) to determine dietary and antioxidant treatment effects on carcass characteristics, fatty acid composition, and quality of Uruguayan beef. Half of the steers finished on concentrate were supplemented with 1000 I.U. vitamin E head(-1) day(-1) for 100 days. Postmortem vitamin C was added to ground beef (0.05% v/w) displayed for 8 days at 2 °C. Carcasses from steers finished on concentrate had greater (P<0.05) carcass weight, conformation, degree of finishing, fat depth, and ribeye area than pasture finished animals. Carcasses from pasture-fed steers showed darker (P<0.05) longissimus color and yellower (P<0.05) fat at 24 h postmortem than concentrate-fed. Initial longissimus Warner-Bratzler shear force (WBSF) values were similar (P>0.05) between pasture- and concentrate-fed animals. However, beef from pasture-fed cattle had lower (P<0.05) WBSF values at 7 and 14 days postmortem. Longissimus α-tocopherol concentrations were greater (P<0.01) for pasture- and concentrate-fed animals that were supplemented with vitamin E compared to concentrate-fed. Steaks from pasture-fed and vitamin E supplemented cattle had similar (P>0.05) TBARS values, which were lower (P<0.05) than steaks from concentrate-fed steers during 21 days of display. Ground beef from vitamin E supplemented steers had the lowest TBARS values; whereas samples from pasture-fed animals had the lowest lipid stability with higher TBARS levels than other treatments. Vitamin C addition to ground beef did not (P>0.05) reduce lipid oxidation. Vitamin E supplementation of concentrate-fed cattle had no effect (P>0.05) on color stability of ground beef or steaks. The a(∗) (redness) and b(∗) (yellowness) values were higher (P<0.05) when vitamin C was added to ground beef. Longissimus fatty acid content of concentrate-fed animals was twofold greater (P<0.01) than pasture-fed. The percentages of C14:0, C16:0, and C18:1 fatty acids were higher (P<0.01) in the intramuscular fat of concentrate-fed steers, whereas pasture-fed cattle showed greater (P<0.01) proportions of C18:0, C18:2, C18:3, C20:4, C20:5, and C22:5. Total conjugated linoleic acid (CLA) and CLA isomer c9t11 were higher (P<0.01) for pasture- than concentrate-fed cattle. Vitamin E supplementation of concentrate-fed steers increased lipid stability of ground beef and steaks, but was unable to improve color stability; whereas vitamin C addition to ground beef increased color stability without altering lipid oxidation. Finishing cattle on pasture enhanced the unsaturated fatty acid profile of intramuscular fat in beef including CLA and omega-3 fatty acids.

RESUMO

Mitomycin C (MMC) has been used as a component of many chemotherapeutic regimens and some toxic effects of this substance have been reported. As it has been reported that the toxicological effect of a drug can alter the biodistribution of radiopharmaceuticals and because patients on chemotherapeutic treatment can be submitted to a nuclear medicine procedure, we investigated whether MMC could affect the uptake of various technetium-99m (99mTc) radiopharmaceuticals used for renal evaluations. The purpose of this study was to suggest a model to evaluate the toxic effect of substances in specific organs. Three doses of MMC (0.45 mg) were administered to mice (N=15). One hour after the last dose, 99mTc radiopharmaceuticals, 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA), 99mTc-dimercaptosuccinic acid (99mTc-DMSA) or 99mTc-glucoheptonic acid (99mTc-GHA), with activity of 7.4 MBq, were also administered in the treated group and in the control group (N=15). After another 0.5 h, the animals were sacrificed. The organs were isolated, the 99mTc radiopharmaceutical uptake in the organs quantified in a well counter and the percentages of radioactivity (%ATI) calculated. The results have shown that: (i) with 99mTc-DTPA, the %ATI increased in the pancreas, ovary, uterus, stomach, kidney, spleen, thymus, heart, lung, liver, thyroid and bone; (ii) with 99mTc-DMSA, the %ATI decreased in all the organs except for the brain; and (iii) with 99mTc-GHA, the %ATI increased in the liver and decreased in the stomach, thymus, heart and thyroid. The effects of this chemotherapeutic drug on the biodistribution of these radiopharmaceuticals were statistically significant (Wilcoxon test, p<0.05) and could be explained by the metabolization and/or therapeutic action of MMC. Studies with other radiopharmaceuticals are in progress.

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The objective of this study was to investigate the possibility of genotype x environment interactions for weaning weight (WWT) between different regions of the United States (US) and between Canada (CA), Uruguay (UY), and US for populations of Hereford cattle. Original data were composed of 487,661, 102,986, and 2,322,722 edited weaning weight records from CA, UY, and US, respectively. A total of 359 sires were identified as having progeny across all three countries; 240 of them had at least one progeny with a record in each environment. The data sets within each country were reduced by retaining records from herds with more than 500 WWT records, with an average contemporary group size of greater than nine animals, and that contained WWT records from progeny or maternal grand-progeny of the across-country sires. Data sets within each country were further reduced by randomly selecting among remaining herds. Four regions within US were defined: Upper Plains (UP), Cornbelt (CB), South (S), and Gulf Coast (GC). Similar sampling criteria and common international sires were used to form the within-US regional data sets. A pairwise analysis was done between countries and regions within US (UP-CB vs S-GC, UP vs CB, and S vs GC) for the estimation of (co)variance components and genetic correlation between environments. An accelerated EM-REML algorithm and a multiple-trait animal model that considered WWT as a different trait in each environment were used to estimate parameters in each pairwise analysis. Direct and maternal (in parentheses) estimated genetic correlations for CA vs UY, CA vs US, US vs UY, UP-CB vs S-GC, UP vs CB, and S vs GC were .88 (.84), .86 (.82), .90 (.85), .88 (.87), .88 (.84), and .87 (.85), respectively. The general absence of genotype x country interactions observed in this study, together with a prior study that showed the similarity of genetic and environmental parameters across the three countries, strongly indicates that a joint WWT genetic evaluation for Hereford cattle could be conducted using a model that treated the information from CA, UY, and US as a single population using single population-wide genetic parameters.

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Records from the Hereford Associations of the United States (USA), Canada, and Uruguay were used to estimate genetic and phenotypic variances and covariances for weaning weight. Estimation was done using a complete animal model, relatively large data sets, and the same methodology for the three countries in order to determine whether genetic parameters for weaning weight were homogeneous across environments. Data were composed of 2,322,722, 487,661, and 102,986 edited weaning weight records for USA, Canada, and Uruguay, respectively. Ten samples were obtained from each country by eliminating data from small herds with fewer than 500 records, selecting herds at random from the entire data set after removing the small herds, and then retaining the direct-sire-connected contemporary groups within each sample. The final sample sizes ranged from 9,832 to 46,377 records. An accelerated EM-REML algorithm was used in estimating the (co)variance components in each sample. The estimates were pooled by calculating the arithmetic mean of the 10 samples from within each country. Direct and maternal (in parentheses) heritability estimates were .24 (.16), .20 (.16), and .23 (.18) for USA, Canada, and Uruguay, respectively. Maternal heritabilities reported here are nearly 50% smaller than the values currently used in national genetic evaluation for the breed, which were estimated using sire-maternal grandsire models. Covariance between direct and maternal was negative in all countries, accounting for 6, 8, and 10% of the total phenotypic variation, and the total dam effect was 32.5, 37.0, and 34.0% in USA, Canada, and Uruguay, respectively. Total heritabilities were similar among the countries, with values of .19, .19, and .17 for the three respective countries. The similarity of genetic and environmental parameters across the three countries suggests that joint genetic evaluation is feasible across environments provided that the genotype x environment interaction is negligible and can be ignored.

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The effect of malnutrition on the biodistribution of radiopharmaceuticals is not known. We studied the biodistribution of 99Tcm-labelled sodium pertechnetate (Na99TcmO4) in two rat models of malnutrition. Three groups of 2-month-old rats were separated according to their diets: (1) control diet, 23% protein (C); (2) protein-restricted, receiving 8% protein (PR), both ad libitum; and (3) energy-restricted, receiving 60% of control diet (ER). After 21 days of the diet, 99Tcm was injected and the animals were killed after 30 min. The organs were isolated, their weight determined and the absolute per cent (%ID) and the per cent per gram injected dose (%ID x g(-1)) calculated. The %ID and %ID x g(-1) had a similar pattern, increasing in stomach and brain and decreasing in the thyroid, but did not change significantly in kidney, lung, liver, bone or testis in PR rats, except in the heart where the increase was only observed in the %ID x g(-1). In the ER group the %ID x g(-1) was decreased in the bone only, and did not change in the other organs. It is suggested that when using Na99TcmO4 scintigraphy in malnourished patients, the different patterns of distribution must be kept in mind.

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Drug therapy can alter the biodistribution of radiopharmaceuticals. We studied the effect of mitomycin-C, a drug used in oncology, on the biodistribution in mice of 99Tcm-methylene diphosphonic acid (99Tcm-MDP). Three doses of mitomycin-C were administered. After the last dose, 99Tcm-MDP was injected and the animals were killed. The organs were isolated, their weight determined and the percent per gram injected dose (%ID/g) calculated. The %ID/g had increased in the pancreas, ovary, stomach, uterus, kidneys, spleen, thymus, heart, liver and lungs, but did not change significantly in thyroid, bone or brain. As a change in 99Tcm-MDP uptake by bone is not observed, a modification to bone scintigraphy is not required. As mitomycin-C treatment altered 99Tcm-MDP uptake in some organs, any hot spots should be evaluated carefully to avoid a misdiagnosis.

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