SUMMARY Caecal fluid samples collected 8 and 24 hours after carbohydrate overload were quantitatively compared to control samples in terms of aerobic and anaerobic bacteria. Concomitant increases in lactic acid‐producing bacteria and decreases in Gram negative bacteria were substantiated during the onset of acute laminitis. Progressive decreases in caecal fluid pH were also quantitated. Although endotoxin assays of caecal fluid and blood were not done, the caecal flora changes suggest its presence during the onset of acute laminitis. RÉSUMÉ Des échantillons de fluide coecal recueillis 8 et 24 heures apràs une surcharge digestive en hydrates de carbone furent comparés à des échantillons témoins pour apprécier les modifications de la flore aérobie et anaérobie. On constata une augmentation des bactéries productrices d'acide lactique et une diminution des bactéries Gram—avec installation des signes de fourbure aigue. Une diminution progressive du Ph du liquide coecal fut également remarquée. On ne contrôla point la présence d'antoxines dans le liquide coecal ni dans le sang. Mais les variations de la flore coecale laissent penser à l'existence de telles toxines au début de la fourbure aigue. ZUSAMMENFASSUNG Blinddarminhalt wurde 8 und 24 Stunden nach Kohlenhydratüberfütterung entnommen und quantitativ verglichen mit Kontrollproben (Zahl der aeroben und anaeroben Bakterien). Beim Eintritt einer akuten Hufrehe kommt es gleichzeitig zu einer Vermehrung von Lactat‐produzierenden Bakterien und zu einer Verminderung von Gram‐negativen Keimen. Ein zunehmender Abfall des pH im Blindarminhalt konnte ebenfalls quantitativ erhärtet werden. Obgleich Endotoxinbestimmungen in der Blinddarmflüssigkeit und im Blut nicht vorgenommen werden konnten, kann das Vorhandensein von Endotoxin aufgrund der Veränderungen der Flora beim Eintritt einer akuten Rehe vermutet werden.

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Four experiments were conducted to determine the influence of yeast culture on 1) the health and performance of feeder calves, 2) the response of calves to an infectious bovine rhinotracheitis virus (IBRV) infection, and 3) nutrient utilization in lambs fasted for 3 d. In Exp. 1, 108 feeder calves were transported from Tennessee to Texas (1,600 km) and fed receiving diets containing 0 or .75% yeast culture and .35 or .69% P in a 2 x 2 factorial arrangement of treatments. In Exp. 2, 101 calves were transported 950 kg from Austin, TX to Bushland, TX and fed receiving diets containing 0, .75, 1.125, or 1.5% yeast culture. Yeast culture did not significantly affect the health or performance of calves in either experiment, although morbid calves fed yeast culture required fewer (P less than .05) days of antibiotic therapy in Exp. 2. In Exp. 3, feeder steers were fed diets containing 0 or .75% yeast culture and challenged intranasally with IBRV. Calves fed yeast culture tended to maintain heavier weights and higher DMI during IBRV infection than did steers fed the control diet. In Exp. 4, feeder lambs were fasted for 3 d and refed diets containing 0, .75, 1.125, or 1.5% yeast culture during a N and mineral balance trial. Lambs fed yeast culture had greater (P less than .08) N balance and tended to have greater Zn and Fe balance than control lambs. Results of these studies are interpreted to suggest that supplementation of morbid calves with yeast culture can have beneficial effects (fewer sick days, higher feed intakes) and that these effects may be mediated by improved N, Zn, and Fe metabolism.

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A protocol previously developed for B. napus microspore culture was modified to produce embryos from several lines of Brassica campestris. Bud size, genotype, media constituents, and incubation time and temperature were examined. Donor plants were grown in a growth cabinet at a day/night temperature of 10/5°C. Microspores were isolated from buds 2.0 - 2.9 mm in length and cultured in modified Lichter (1982) medium containing 17% sucrose, pH 6.2. After 48 h at 32°C, the incubation medium was replaced with NLN (Lichter 1982) medium containing 10% sucrose. Microspores were cultured at 24°C in darkness and embryos developed after three weeks. More than 1000 plants have thus far been regenerated. Genotypic differences were observed for microspore embryogenesis. The majority of the regenerants were haploid, however colchicine could be effectively used to achieve chromosome doubling.