The rate and pattern of urea infusion into the rumen of wethers alters nitrogen balance and plasma ammonia.

Changes in N balance, urinary excretion of purine derivative (PD), urea, creatinine and ammonia and plasma ammonia, glucose, urea, insulin and IGF-1 were examined in four wethers (37 ± 2.6 kg BW). The animals were fitted with permanent ruminal catheters, fed lucerne hay (9.4 MJ/day; 23 g N/day; 7 g soluble N/day, 6 equal meals/day) and treated with contrasting rates of urea infusion into the rumen: first, a continuous infusion (CT), at 3.2 mg urea-N/min for 10 days and then a discontinuous infusion (DT) at 156 mg urea-N/min for 4 min; in 6 daily doses with the meals for 7 days. N balance was calculated from pooled samples of faeces and urine. Jugular blood samples were collected before and 1.5 h after the morning meal (M1) on days CT10, DT2, DT4 and DT6. N retention decreased during DT (p = 0.01) due to a significant increase of N excretion in urine (4 g/day; p = 0.009) and faeces (1 g/day; p = 0.02). Dry matter (p < 0.001) and N digestibility in vivo (p = 0.01) decreased significantly during DT. Urinary urea and PD excretion were not altered by treatment. Significant linear (p = 0.004) and quadratic (p = 0.001) effects were observed for plasma ammonia in M1 (from 170 CT10 to 235 µm DT2 and returned to 120 µm DT6). No changes were observed in plasma glucose, urea, insulin and IGF-1. Results indicate that changes from CT to DT reduced N retention in sheep due to enhanced urinary N excretion, but it was not associated with changes in urinary urea or PD excretion; or plasma concentrations of insulin and IGF-1. As the dry matter (DM) an N digestibility could account a 0.23 of the decrease in N retention; the largest fraction of the reduction in N retention remained unexplained by the results.

Splanchnic net balance of oxygen and metabolites in response to a discontinuous mesenteric vein infusion of ammonium in sheep.

To simulate daily episodes of high absorption associated with the intake of diets with high N content, four wethers (42 ± 3.4 kg body weight), fitted with permanent catheters in the femoral artery and splanchnic vessels, were infused with 340 µmol into the mesenteric vein for 3 h, during the morning meal, over seven consecutive days. On the 7th day, mass transfers of , urea, glucose, lactate, ß-OH-butyrate and O2 were measured across portal-drained viscera (PDV), liver and splanchnic tissues during the last 90 min of the infusion. Measurements were repeated on the following day, at the same time, without the infusion. Plasma concentration in the portal vein (+332 µm; p = 0.006), portal absorption (+424 µmol/min; p < 0.001), liver uptake (+375 µmol/min; p = 0.003) and urea N production (+338 µmol/min; p = 0.059) were higher during infusion. Mass transfers of urea, glucose, lactate, ß-OH-butyrate and O2 across the PDV, and glucose, lactate, ß-OH-butyrate and O2 across the liver, were not altered by the infusion. Results suggest that a daily, discontinuous increase in portal flow during a meal stimulates liver removal and urea N production but does not significantly affect liver glucose production and O2 consumption in sheep.

Influence of temperature on zearalenone production by regional strains of Fusarium graminearum and Fusarium oxysporum in culture.

Zearalenone production by Fusarium graminearum and Fusarium oxysporum was studied under two temperature conditions. Incubation at 25 degrees C for 4 weeks enhanced zearalenone synthesis, improving detection of zearalenone-producing strains of Fusarium oxysporum. Zearalenone production was either totally or partially inhibited when temperature was lowered to 12-14 degrees C during the last 2 weeks of incubation.

Effects of long-term zearalenone administration on spermatogenesis and serum luteinizing hormone, follicle-stimulating hormone, and prolactin values in male rats.

Body and testis weights, serum luteinizing hormone, follicle-stimulating hormone, and prolactin values and volume fractions of Sertoli cells, spermatogonia, early and late primary spermatocytes, and round and long spermatids were evaluated in 70-day-old male rates treated orally with 20 mg of zearalenone/kg of body weight daily for 5 weeks. Significant (P < 0.05) increase in serum prolactin concentration was consistently observed during the 5 weeks of treatment with zearalenone. Significant changes were not observed in any of the other variables evaluated.

Lack of effect of a diet containing zearalenone on spermatogenesis in rams.

Six breeding rams were fed a diet containing 12 mg of zearalenone daily for eight weeks. A control group of six rams was fed a diet free of zearalenone. The weekly production of spermatozoa of both groups was measured during the period of administration of zearalenone and for six weeks after the administration of zearalenone ceased. Semen production was measured in terms of the volume of ejaculate and its concentration, and the motility and abnormalities in the spermatozoa. The feeding of zearalenone had no significant effects on any of these measurements.

[Hyperestrogenism in swine due to natural poisoning with zearalenone]. / Hiperestrogenismo en cerdas por intoxicación natural con zearalenona.

A field case is described in which all prepuberal swine of a group of 20 pigs and 11 sows showed marked estrogenic effects. These consisted of enlarged mammary glands, swelled tumefacient vulva, and greatly enlarged internal reproductive organs. The corn used to feed these animals was found to contain 56 ppm zearalenone. Deoxynivalenol (4.9 ppm) was found in the corn; T-2 toxin, nivalenol, fusarenon-X, diacetoxyscirpenol, aflatoxins and ochratoxins were absent. Identity of Z was confirmed by TLC in four solvent systems, behavior of the suspected spots under UV light of different wavelengths, change of fluorescence from green to blue after spraying with 5% AlCl3 in alcohol and heating at 110 degrees C during 5 minutes, and by its UV spectrum. A zearalenone producing strain of Fusarium oxysporum was isolated from the suspected grain. Histopathology of uterine tissue showed typical changes produced by zearalenone: hyperplasia, hypertrophy, and metaplasia of the myometrium. Feeding of the grain to a prepuberal sow under controlled conditions reproduced all the effect found in the farm animals. This is the first field case of zearalenone poisoning reported in Argentina.

Liver nitrogen movements during short-term infusion of high levels of ammonia into the mesenteric vein of sheep.

Four 40 kg wethers were used in a crossover design to quantify, by arterio-venous procedures, the mass transfer of NH3, urea and amino acids (AAs) across the portal-drained viscera and the liver during a 31 min infusion of either 0 (C0) or 1100 (C1100) micromol NH4HCO3/min into the mesenteric vein. In C1100, hepatic NH3 extraction remained stable at 1214 micromol/min (1.90 micromol/min per g wet liver weight), the capacity for hepatic NH3 removal was exceeded by 654 micromol/min and the incremental (C1100-C0) urea-N release: NH3 -N removal ratio increased progressively, from 0.52 to 0.90. The NH4HCO3 infusion reduced total branched-chain AA transfer across the portal-drained viscera and total AA-N and lysine extraction by the liver. Hepatic release of glutamate was augmented ornithine switched from net release to net removal and net splanchnic release of free essential AA (44 micromol/min (sed 9.2), ) and branched-chain AA (33 micromol/min (sed 2.0), ) were reduced to 0.58 of their basal rate. The study showed that conversion of excess NH3 to urea during a short-term hepatic NH3 overload required no additional contribution of AA-N to ureagenesis; essential AA and branched-chain AA supply to non-splanchnic tissues was, however, temporarily decreased.

Influence of hepatic ammonia removal on ureagenesis, amino acid utilization and energy metabolism in the ovine liver.

The mass transfers of O2, glucose, NH3, urea and amino acids across the portal-drained viscera (PDV) and the liver were quantified, by arterio-venous techniques, during the last 4 h of a 100 h infusion of 0 (basal), 150 or 400 mumol NH4HCO3/min into the mesenteric vein of three sheep given 800 g grass pellets/d and arranged in a 3 x 3 Latin-square design. Urea irreversible loss rate (ILR) was also determined by continuous infusion of [14C]urea over the last 52 h of each experimental period. PDV and liver movements of glucose, O2 and amino acids were unaltered by NH4HCO3 administration, although there was an increase in PDV absorption of non-essential amino acids (P = 0.037) and a trend for higher liver O2 consumption and portal appearance of total amino acid-N, glucogenic and non-essential amino acids at the highest level of infusion. PDV extraction of urea-N (P = 0.015) and liver removal of NH3 (P < 0.001), release of urea-N (P = 0.002) and urea ILR (P = 0.001) were all increased by NH4HCO3 infusion. Hepatic urea-N release (y) and NH3 extraction (x) were linearly related (R2 0.89), with the slope of the regression not different from unity, both for estimations based on liver mass transfers (1.16; SE 0.144; P(b) not equal to 1 = 0.31) and [14C]urea (0.97; SE 0.123; P(b) not equal to 1 = 0.84). The study indicates that a sustained 1.5 or 2.4-fold increase in the basal NH3 supply to the liver did not impair glucose or amino acid supply to non-splanchnic tissues; nor were additional N inputs to the ornithine cycle necessary to convert excess NH3 to urea. Half of the extra NH3 removed by the liver was, apparently, utilized by periportal glutamate dehydrogenase and aspartate aminotransferase for sequential glutamate and aspartate synthesis and converted to urea as the 2-amino moiety of aspartate.

Hiperestrogenismo en cerdas por intoxicación natural con zearalenona / Hyperestrogenism in swine due to natural poisoning with zearalenone

Se describe un caso de intoxicación de cerdas prepúberes con zearalenona (Z) al consumir una dieta conteniendo 56 ppm Z. En el maíz contaminado se encontró una cepa de Fusarium oxysporum que produjo Z en cultivo sobre ese grano. Se indicaron la evidencias de distinta índole que permitieron confirmar que los efecto observados fueron producidos por dicha micotoxina