Repletion of blood selenium concentrations in weaned beef calves

Eighty-three weaned beef calves severely deficient (less than 20 micrograms/L) in blood selenium (Se) were allotted by sex, weight and breed to one of six regimens of Se supplementation for 108 days to examine the efficacy of various Se supplementation programs and to monitor the repletion rate of blood Se concentrations. Cattle in treatment 1 received an IM injection of sodium selenite and an ad libitum feeding of 20 mg Se/kg salt-mineral mixture. Salt-mineral mixtures (treatments 2, 3, 4 and 5) were formulated to contain 20, 40, 80 and 160 mg Se/kg supplement, respectively, and were offered free-choice. Treatment 2 served as the selenium-treated control because 20 mg Se/kg supplement was the maximum permissible by FDA in commercial salt-mineral preparations at the time of this study. Cattle in treatment 6 received a salt-mineral supplement which contained no Se but dried brewers grain (434 micrograms Se/kg) was incorporated in the ration as an organic source of Se and fed at a rate of 1.1 kg/head/day. There was a within group time/treatment interaction (P less than 0.01) among all treatments as blood Se concentrations significantly increased over time. Final mean whole blood Se concentrations for treatments 1-6 were 87.8, 60.6, 95.1, 123.1, 154.2 and 91.4 micrograms/L, respectively. Treatments 1, 3, 4, 5 and 6 effectively increased and maintained whole blood Se concentrations at adequate levels (greater than 70 micrograms/L) by day 84. Treatment 2 (control) increased blood Se during the 108-day study, but blood Se concentrations never exceeded marginal levels (50-70 micrograms/L). Cattle consumed less salt-mineral supplement as the concentration of Na selenite increased from 20 to 160 mg Se/kg supplement.     

Chlorpyrifos intoxication in a bull

A mature Brangus bull received the recommended dose of chlorpyrifos and became dull and inappetent 3 days later. Clinical findings included weakness, dehydration, rumen stasis, and rumen distention with fluid and gas. Blood cholinesterase activity was 25% of normal. The bull's condition improved after treatment with pralidoxime, antimicrobials, electrolyte solutions, vitamins, and adsorbents. Five weeks later, the bull had gained weight, the blood cholinesterase activity was 70% of normal, and the results of a semen evaluation indicated he was a satisfactory potential breeder.     

Gossypol toxicity in preruminant calves

SUMMARY Twenty-four of 57 calves fed a diet containing 33% cotton seed meal (CSM) died between 7 and 15 weeks of age. Initial deaths were not accompanied by premonitory signs, but after CSM withdrawal most calves developed rough coats, anorexia, weakness, ascites and subcutaneous oedema. Those that died had large volumes of serous fluid in the body cavities, hard livers of ‘nutmeg’ appearance, and pulmonary congestion. Histopathologically the livers showed periacinar necrosis in acute cases and periacinar fibrosis in chronic cases. Lungs from several calves had oedema, haemosiderosis and fibrosis in some pulmonary vessels. Atrophy of myocardial fibres was present in most cases. The concentration of free gossypol in the diet was 100 to 220 mg/kg. Ante-mortem and post-mortem findings supported a diagnosis of gossypol poisoning. The deaths continued for 4 weeks after withdrawal of CSM from the diet.     

An effective medium for isolating Sphaeropsis sapinea from asymptomatic pines

The pathogen Sphaeropsis sapinea can persist in stems and branches of asymptomatic pines and can later induce disease when triggered by host stress. Several experiments were conducted to test if:(i) medium amended with tannic acid (TA) can increase the frequency of cultural detection of this shoot blight and canker pathogen from asymptomatic red pine (Pinus resinosa) stems, and (ii) S. sapinea can persist in asymptomatic red pine in the field following artificial inoculation. TA (0.5% w/v) in 2% (w/v) water agar proved to be the best medium for isolation of S. sapinea among a larger number of tested media. The addition of TA had little or no effect on the growth of two group A and two group B isolates of S. sapinea. However, when TA was added, 11 other fast‐growing fungal isolates from stems/branches of red or jack pines (P. banksiana) were inhibited and grew more slowly (p < 0.05) than both S. sapinea groups. The TA‐amended medium improved cultural detection of S. sapinea from 2‐year‐old, asymptomatic red pine nursery seedlings compared with two other methods used for the cultural detection of S. sapinea (32%vs. 8.5% and 18% recovery; p < 0.001 and p = 0.031, respectively). A field test using the TA‐amended media established that S. sapinea can persist asymptomatically in red pine trees for at least 1 year. This medium significantly reduces the frequency of false‐negatives from asymptomatic field material.