Abstract 108

Lavezzo,-OENM; Mattos,-WRSde; Lavezzo,-W; Faria,-VP-de

Faculdade de Medicina Veterinaria e Zootecnia, UNESP, Campus de Botucatu, SP, Brazil.

Revista-daSociedade-Brasileira-deZootecnia. 1988, 17: 3, 292-307; 36 ref.

In a 2 X 2 X 9 X 4 factorial design rumen fluid was collected by oesophageal tube and rumen fistulae during 2 periods of 15 days with an adaptation period of 21 days for each in 4 cows, mean liveweight 450 kg and 8 years old, fed on diets equal in protein based on sorghum silage with brewers' yeast (D1) or cottonseed meal (D2) as protein sources. Samples were collected 0, 1, 2, 4, 6, 8, 12, 16 and 24 h after feeding on the 5th and 12th day of each period. Diets were reversed during the 2nd period. pH was similar at 0, 12, 16 and 24 h with D1 and D2. Values were lower for D1 at 1, 2, 6 and 8 h. Ammonia-nitrogen concentrations were similar for D1 and D2 for the 24 h period. Highest values were after 2 h (19.32 and 18.93) and 4 h (17.57 and 19.46 mg/100 ml) for D1 and D2, respectively. Total volatile fatty acids and acetic acid values were significantly different between diets. Propionic acid, n-butyric and n-valeric acids were greater with D1. Results indicate that sampling time for rumen fluid collected at 10 to 12 h after feeding can give accurate indications of prevalent tendencies in the rumen. Variations between cows resulted from differences in fermentation pattern irrespective of diet.