Composition and quality of Mexican and imported retail beef in Mexico.

Randomly selected New York steaks from domestic and imported beef were purchased in three major Mexican cities, comparing Mexican beef (from northern, central, and southern regions of the country) and American beef (USDA-Choice and ungraded No Roll). The meat was analyzed for chemical composition, Warner-Bratzler shear force (WBSF), cooking loss, color and consumer acceptability. All sources of Mexican beef and No Roll US beef had similar chemical composition. USDA-Choice beef had a higher fat content and a lower moisture and total collagen content. Mexican beef from the northern region and USDA-Choice beef had lower WBSF and redness values than the other beef sources. Overall desirability was high regarding all Mexican beef sources, and USDA-Choice beef. No Roll US beef had the lowest overall desirability score. Results indicate Mexican beef is in an advantageous position when competing with imports in the current open market.

Evaluation of two mycotoxin binders to reduce toxicity of broiler diets containing ochratoxin A and T-2 toxin contaminated grain.

In order to assess ochratoxin A (OA) and T-2 toxin (T-2) binding ability of two commercial sorbents, both in vitro and in vivo trials with broilers were performed. Crude OA and T-2 extracts from contaminated grain were used to assess in vitro binding ability of two sorbents (Zeotek [Zk] and Mycofix [Mx]), by quantifying free mycotoxin through an enzyme-linked immunosorbent assay (ELISA) test. For in vivo trial, a 3 x 2 x 2 factorial arrangement was used for this experiment, being the factors: adsorbents (none, Zk, and Mx), OA (0 and 567 parts per billion [ppb]) and T-2 (0 and 927 ppb). OA and T-2 contaminated wheat and corn, respectively, were added to sorghum-soybean meal diets to meet 567 ppb of OA and 927 ppb of T-2. Mycotoxins were fed alone or combined in treatments. After 21 days, blood chemistry, gross, and histological evaluations were performed. Relative weights of liver, kidney, and bursa of Fabricius were obtained. Zk had the highest OA and T-2 in vitro binding ability (100% and 8.67%, respectively). Chickens fed OA with or without sorbents had a lower body weight and feed intake reduction. However, those birds fed T-2 were partly protected by a sorbent. Birds fed both toxins showed toxic additive effects, and no protection of any adsorbent was observed. A significant reduction in plasma proteins, albumin, and globulins was a characteristic observed in all birds fed diets with OA both with or without adsorbents. Uric acid level in blood was increased in all chickens fed OA-contaminated diets. Histological findings observed in birds fed OA-contaminated diets were necrosis of kidney tubular cells, swollen and necrotic hepatocytes, bile ducts hyperplasia, and increased diameter of proventriculus glands. In birds that received T-2 alone, only the liver, with the same kind of lesions, was affected. According to these results, it can be concluded that there is not a relation between in vitro and in vivo trials. OA toxic effects could not be counteracted by any sorbent. T-2 toxicity could be partially counteracted by an adsorbent used in this research.

The effect of low doses of naloxone on the preovulatory surge of LH and on the onset and duration of oestrus in the ewe with induced oestrus during the non-breeding season.

The objective of this work was to study the effect of the endogenous opiate peptide (EOP) antagonist, naloxone, on the preovulatory LH surge and on the time of onset and duration of oestrus in the ewe with induced oestrus during the non-breeding season. Forty Suffolk X Hampshire ewes 2-3-years-old and 50+/- 4kg were studied, ewes were divided at random in two groups of 20, housed in open paddocks under natural photoperiod (19 degrees latitude N); were fed with hay and commercial pellets, and provided water ad libitum. Group one received an intravaginal sponge with 45mg of medroxiprogesterone acetate for 14 days, and upon sponge withdrawal 250IU of eCG was administered i.m. Group two received the same treatment as group 1 but in addition they received two i.m. injections of 0.5mg of naloxone, one given on sponge withdrawal and the second 24h later (total dose 1.0mg). Oestrus in naloxone-treated ewes was present 32+/- 2h and in control ewes in 35+/- 3h after sponge withdrawal. Duration of oestrus in control ewes was shorter (27+/- 2.5h), than naloxone-treated ewes (39+/- 6h); (P<0.0001). The LH surge in naloxone-treated ewes was initiated 5h after onset of oestrus, and 8h after onset of oestrus in control ewes, and the difference was significative (P<0.0006). It was concluded that EOP are important modulators of reproductive function in the ewe.

Effect of breed and age on the voluntary intake and the micromineral status of non-pregnant sheep. 1. Estimation of voluntary intake.

Twenty-four sheep were used to test breed and age differences in voluntary intake (VI). The sheep were divided into four groups of six animals each: Suffolk mature ewes (SM), Suffolk yearlings (SY), Rambouillet mature ewes (RM), and Rambouillet yearlings (RY). The animals grazed alternatively two mixed pastures containing Trifolium repens latum, Lolium perenne and Pennisetum clandestinum from 07:00 to 16:30 hours and remained penned overnight. Voluntary intake was estimated using chromic sesquioxide (1g per sheep) as an external marker, administered in two gelatin capsules, one before and one after grazing, during 65 days. Faecal grab samples were collected directly from each animal for three consecutive days beginning on Day 7 of the experiment and at 14-day intervals until Day 65 (sampling times=5). Hand-plucked samples of forage were used to estimate in vitro dry matter digestibilities (IVDMD), which were used with estimates of fecal output to calculate intakes (per animal and per kg of metabolic body weight (kg(0.75))). The data were analyzed as a completely randomized design in a factorial arrangement with repeated measurements. Voluntary intake, expressed both per animal and per kg(0.75), showed a breedxage interaction (P<0.001). Suffolk mature ewes had the greatest daily VI (1.88 versus 1.26kgDM/animal for the other three groups) because they were the heaviest animals, but their VI/kg(0.75) (0.071kgDM/day) was not different (P>0.05) from that of RY (0.063kgDM/day), which were smaller, younger animals. Suffolk yearlings and RM had similar VI/kg(0.75) (0.057 and 0.051kgDM/day, respectively), not different from that of the RY. Intakes showed a cubic trend (P<0.001) with time, possibly because of changes in IVDMD and climatic conditions. The lower intake, yet better gains of RM and RY indicate a greater ability to thrive under conditions of average pasture quality. High forage availability did not result in greater forage consumption. The information on VI was later used to assess the micromineral status of the sheep in the experiment.

Effect of breed and age on the voluntary intake and the micromineral status of non-pregnant sheep. II. Micromineral status.

Twenty-four non-pregnant sheep, divided into four groups of six animals each, were used to test breed (Suffolk and Rambouillet) and age (mature (six years old) and yearling (16 months old) ewes) differences in micromineral status. The animals grazed alternatively two mixed pastures containing Trifolium repens latum, Lolium perenne and Pennisetum clandestinum from 07:00 to 16:30hours, and remained penned overnight. Hand-plucked forage samples, blood and wool samples were collected on Days 1 (except forage), 7 (except wool), 21, 35, 49, and 63 of the experiment and assayed for Zn, Fe, Cu, Se, and Mo. Blood and wool data were analyzed as a completely randomized design in a factorial arrangement with repeated measurements. Zinc blood levels (2.15mgkg(-1), below normal values) showed a sampling timexbreed interaction (P<0.05) with a quadratic trend (P<0.02). Iron blood levels (337.48mgkg(-1)) showed a sampling timexage interaction (P<0.05), with mature ewes having higher and more variable levels than yearlings. A sampling time effect (P<0.01) with a quadratic trend (P<0.05) dependent on the breed (P<0.01) was found in Se blood levels. Rambouillet sheep had higher (86µgkg(-1)) initial levels than Suffolk sheep (61.14µgkg(-1)) and they declined linearly, whereas Se levels in Suffolks showed a quadratic trend. Copper blood concentration (below normal values) was higher (P<0.01) in Suffolks (0.46mgkg(-1)) than in Rambouillets (0.35mgkg(-1)). Suffolk sheep had higher Zn (P<0.01) and Cu (P<0.05; below normal values) levels in wool (146.63 and 2.16mgkg(-1), respectively) than Rambouillet sheep (141.34 and 1.72mgkg(-1), respectively). No effect was found in Fe wool levels (291.22mgkg(-1)), and Se concentration in wool (204.7µgkg(-1)) only showed a sampling time effect (P<0.05) with a decreasing linear trend (P<0.01). Coefficients of variations higher than 50% were found for Zn and Se in blood and Fe and Se in wool. Molybdenum could not be detected either in blood or in wool. Rambouillet sheep, in general, showed lower and less variable micromineral levels than Suffolk sheep. Because no signs of deficiency were observed nor was the animals' productivity affected after the study, it is considered that reported normal values for Zn and Cu could be more variable than suspected, depending on breed, location, feeding practices and physiological state.

[Endocrine function of the testicle in the Mexican crossbred ram at different times of the year and its opioidergic control during anoestrus]. / La función endócrina del testículo en el carnero criollo Mexicano durante las diferentes épocas del año y su control opioidérgico durante el anestro.

This work was carried out with the objective of studying the endocrine function of the testes in the Mexican Crossbred Ram (Suffolk x Hampshire) during the different seasons of the year in a latitude of 19 degrees 13' N. Also studied was the opioidergic control of this gland during anoestrus. For this purpose 8 rams were used, from which 3 ml of jugular blood were obtained three times a week to study the seasonal fluctuations in plasma testosterone. The experiment was carried out from May 1993 until June 1994. The androgen was determined by radioimmunoassay. To study the opioidergic control of androgen secretion during seasonal anoestrous (May-June) four of the rams were selected at random and treated with 0.5 mg naloxone at 12 h intervals during 3 continuous weeks. It was observed that blood testosterone was lowest during long days, and concentration was highest during the breeding season. Chronic naloxone medication during anoestrus resulted in a significant increase in blood testosterone (P < 0.001), an effect that was evident after the first week of treatment. When naloxone administration was discontinued, blood testosterone levels returned to basal. With this experiment it was demonstrated that an opioid antagonist such as naloxone administered in low doses, is capable of altering plasma testosterone concentration in the anoestrus ram, giving further support to endogenous opioids as important modulators of reproduction in seasonal breeders such as sheep.

The effect of neomycin on the kidney function of the horse.

The toxic effect of neomycin on the horse kidney was studied. Twelve horses were used, and were divided at random into three groups of four. The first group was treated twice a day with 10 mg/kg I.M. for 15 days and then euthanised; kidney and liver samples were studied and no histopathological changes were observed. Group 2 was treated with neomycin sulphate as in group 1, and group 3 was used as control. Blood samples were taken at 8.00 h and 20.00 h daily from both neomycin treated and control horses. Serum creatinine, potassium, sodium and urinary creatinine remained without change. On day 6 of treatment plasma urea (Urea)p decreased to 5.6 +/- 2.0 mmol/L (P < 0.001) as compared with controls (8.0 +/- 2 mmol/L). Urinary excretion of GGT increased on the third day of treatment to 118.6 +/- 1 IU/L for treated and 89 +/- 8 IU/L for controls (P < 0.001). Thereafter, GGT continued to be elevated significantly for the duration of the experiment, as compared with controls. The (GGT)/(Cr)u ratio increased significantly on the 9th day of treatment, and continued to be elevated for 6 days after treatment. Neomycin kinetics were similar during treatment. It was concluded that neomycin, in the dose used, was not harmful to kidney function in the horse.

Taxonomical, clinical and pathological findings in moradilla (Lobelia-like) poisoning in sheep.

Each year during late winter and spring, grazing sheep and cattle in the State of Tamaulipas in northeastern Mexico develop toxicoses which have been empirically associated to consumption of a toxic plant locally known as moradilla. This investigation was undertaken to determine whether moradilla was a toxic plant not yet reported in Tamaulipas or was an unrecognized species of the Lobelaceae or Campanulaceae family. Taxonomic determination of moradilla plants collected from February to April showed that it was a species of Lobelia. Five alkaloids were identified by thin-layer chromatography in the mature stages of moradilla, while only 1 and 3 alkaloids were found in the growing and flowering stages of this plant, respectively. The alkaloids were not affected by making silage, drying in hay or freezing. Experimental intoxication of sheep with moradilla caused clinical signs and pathologic changes identical to those previously described for lobelia toxicosis. It was concluded that Lobelia berlandieri was the cause of moradilla toxicosis in grazing cattle and sheep of northeastern Mexico.

Effect of tortilla-preparation process on aflatoxins B1 and B2 in corn.

Naturally contaminated corn containing 450 and 54 ppb aflatoxins Bi and B2, respectively was treated with Ca(OH)2 for making tortillas. The cleaned corn and tortillas were analyzed for aflatoxins B1 and B2 by high performance liquid chromatography (HPLC) and confirmed by thin layer chromatography (TLC). The average concentrations of aflatoxins B1 and B2 in the final products (tortillas) were only 40% and 28% lower than that in starting materials (corn kernels), respectively. Aflatoxins G1 and G2 were not detected in either corn or tortilla samples.

Clinical infectious bovine rhinotracheitis in cattle fed organic iodine and urea.

The feeding of ethylenediamine dihydriodide (EDDI) at the dose levels of 50 and 500 mg/animal/day and urea at the dose level of 45 g/animal/day did not affect duration of clinical signs, body weight gain, magnitude or duration of fever, serum concentration of glutamic oxalacetic transaminase, packed cell volume, and differential white blood cell counts in feeder cattle experimentally infected with infectious bovine rhinotracheitis (IBR) virus. However, coughing and abundance of nasal discharge were significantly greater in calves fed EDDI before and during primary IBR virus infection. Those calves fed 500 mg of EDDI/day coughed more, had greater nasal discharge, and exhibited greater lacrimation than did those given the smaller dose. These 3 clinical signs were considered to reflect both the expectorant action of EDDI and the pathogenic effects of IBR virus. In all calves, including controls, the coughing, nasal discharge, and lacrimation were most prominent during the period of peak infection (7 to 14 days after the calves were given intranasal inoculation) of the IBR virus. Total serum iodine concentration became maximal (mean of 1,400 ng/ml) in 8 calves after they had been fed the larger dose of EDDI for 2 weeks. This value was maximal (about 300 ng/ml) in another 8 calves after 3 weeks' feeding of the smaller dose (50 mg/day). When EDDI exposure was maintained at the dose level of 50 mg/day for 5 weeks longer, mean serum iodine values remained at about 275 ng/ml, and those of control calves averaged 140 ng/ml.