furostanol-i and Plant-Poisoning

Brachiaria spp. are the most important grasses for ruminants in central-western Brazil. However, the use of these pastures is limited by their toxicity due to steroidal saponins. This experiment was conducted for 60 days to demonstrate the resistance of sheep raised on Brachiaria spp. pastures to steroidal saponin poisoning. The experiment was composed by 48 animals randomly divided into four groups (n = 12). Among them, 32 4- to 5-month-old castrated male crossbred Santa Inês sheep, originating from flocks that had been grazing on Brachiaria spp. for more than three consecutive years, and 16 were non-adapted (naïve) sheep from flocks that never had prior contact with pastures of Brachiaria spp. were randomly divided into four groups. Each of the four experimental groups was composed by eight adapted and four non-adapted animals. The four experimental groups were introduced into paddocks, each of which contained a single grass: either Brachiaria decumbens, Brachiaria brizantha, Panicum maximum, or Andropogon gayanus. The addition of the naïve sheep to the groups was designed to detect pastures' toxicity to naïve sheep and to adjust the stocking rate to optimize the use of forage. The weight gains of sheep grazing on B. decumbens, B. brizantha, and P. maximum were similar; however, the A. gayanus group showed lower weight gains compared with the other groups (P < 0.05). The mean serum activities of γ-glutamyltransferase in the sheep grazing on B. decumbens were higher than those in the sheep from the other groups. No significant differences among the groups were found in aspartate aminotransferase, creatinine, albumin, or total protein serum concentrations. No clinical signs were observed in the adapted sheep in any of the pastures. Of the four non-adapted sheep introduced into the B. decumbens pasture, two showed clinical signs of steroidal saponin poisoning, and one died. No clinical signs were observed in the non-adapted sheep in the other pastures. The saponin (protodioscin) concentrations in the pastures varied from 3.3 to 12.2 g/kg DM in B. decumbens, from 2.8 to 9.1 g/kg DM in B. brizantha, and from 1 to 1.5 g/kg DM in A. gayanus. No saponins were found in P. maximum. It is concluded that sheep from flocks reared in pastures of B. decumbens and B. brizantha were resistant to steroidal saponin poisoning and showed similar weight gains to those of sheep grazing in other tropical pastures.

Topics: Andropogon; Animals; Brachiaria; Brazil; Diosgenin; Male; Panicum; Plant Poisoning; Saponins; Sheep; Sheep Diseases

Some species of the genus Brachiaria are cultivated worldwide in tropical and subtropical climate regions as the main feed for ruminants. Several studies report photosensitization by Brachiaria decumbens, Brachiaria brizantha, and Brachiaria humidicola, but the poisoning by Brachiaria ruziziensis have been reported only twice. Cutaneous and hepatic lesions may be caused by the steroidal saponins present in the leaves or by the mycotoxin sporidesmin produced by the saprophyte fungus Pithomyces chartarum. The present report describes the clinical and pathological changes observed in an outbreak of hepatogenic photosensitization in sheep kept in B. ruziziensis pastures. In addition, the present study will provide a better understanding of the etiology of this photosensitization through the evaluation of the saponin protodioscin and the spore count of P. chartarum. Santa Inês and Lacaune mixed-breed sheep showed signs of photosensitization after feeding B. ruziziensis. Clinical signs included jaundice, apathy, dehydration, and photosensitization characterized by facial edema and cutaneous scars, especially in the ears. Pathological examination of the liver revealed diffuse infiltrates of foamy cells, rare multinucleated cells, and mild enlargement of hepatocytes (megalocytosis). The skin showed acute epidermal and dermal necrosis with occlusive thrombi. B. ruziziensis showed low levels of protodioscin (0.020 ± 0.024% in mature leaves and 0.065 ± 0.084% in sprouts) but high P. chartarum spore counts (mean of 479,844 ± 443,951 spores/g plant). Thus, sheep grazing B. ruziziensis pastures must be closely monitored because of the risk of photosensitization.

Topics: Animals; Brachiaria; Diosgenin; Liver; Photosensitivity Disorders; Plant Poisoning; Saponins; Sheep; Sheep Diseases; Skin

The aim of this work was to study the effects of protodioscin ingestion in two different flocks of sheep: a flock of 23 crossbreed Mato Grosso do Sul Native sheep raised on Brachiaria spp. pastures from birth (experienced flock) in the state of Mato Grosso do Sul; and another flock (naïve flock) of 18 crossbred Dorper × Santa Inês sheep raised in the state of Paraná in Paspalum notatum and Lolium multiflorum pastures. The two flocks grazed together in a Brachiaria brizantha pasture during a 140-day period in the rainy season. At the beginning of the experiment and every 14 days thereafter, blood samples were collected for determination of serum activities of gamma-glutamyl transferase (GGT) and aspartate aminotransferase (AST), and for determination of the icterus index. On the same days, samples of young, mature and old B. brizantha leaves were collected for protodioscin quantification. Naïve sheep were more susceptible to poisoning by B. brizantha than experienced sheep. Six sheep in the naïve flock were poisoned, and two of these died. Two sheep in the experienced flock were poisoned, and one of them died. The mean activities of serum GGT and AST were significantly higher in the naïve flock, also evidencing a higher susceptibility to the poison. These results suggest that flocks of sheep include animals with different degrees of resistance to Brachiaria spp. poisoning and that culling the susceptible animals may considerably increase of the resistance of the flock. The clinical signs and the lesions were similar to those previously reported. However, in sheep with black coats, the main clinical sign was weight loss without photosensitization-mediated dermatitis. One sheep from the experienced flock presented cirrhosis, with clinical signs of exercise intolerance. The protodioscin concentration (% DM) ranged from 0.87% to 2.58% (mean ± SD: 1.64 ± 0.58) in young leaves, 1.16%-2.53% (1.67 ± 0.44) in mature leaves and 0.98%-2.07% (1.52 ± 0.37) in old leaves. A negative relationship was found between saponin concentration and total cumulative precipitation.

Topics: Animals; Aspartate Aminotransferases; Brachiaria; Brazil; Diosgenin; gamma-Glutamyltransferase; Liver; Liver Function Tests; Plant Leaves; Plant Poisoning; Saponins; Sheep; Sheep Diseases; Sheep, Domestic