Counts of ruminal fibrolytic bacteria in Creole goats of Mendoza, Argentina.

GRILLI, D.; PAEZ LAMA, S.; EGEA, V.; CERON, M; CRAVERO, S.; ALLEGRETTI, L.; TELECHEA, A.; DEGARBO, S.; ARENAS, N.

Clermont-Ferrand

Simposio; 8 th INRA-ROWET Symposium on gut microbiology; 2012

Institut National de la Recherche Agronomique

In northwest of Mendoza, Argentina, goats consume a high proportion of shrub species, which represent a large supply of fiber. The digestibility of dry matter and fiber (cellulose, hemicellulose and lignin) of goat breeds adapted to arid area is higher than that of other breeds and domestic ruminants. A high efficiency in use of fiber may be due to a large concentration of fibrolytic bacteria on food particles present in the rumen (Silanikove, 2000). The aim of this study was to quantify the ruminal fibrolytic microbiota in Creole goats in two seasons. Rumen samples were taken from a cannulated goat grazing on natural grassland in the summer (wet season) and winter (dry season). Cellulolytic, hemicellulolytic and pectinolytic bacteria were quantified by most probable number method. Faecal samples were taken for determination of the botanical composition of intake by microhistological technique. Morphological parts consumed were identified by direct observation. Native forages consumed were then analyzed for cellulose, hemicellulose, lignin, starch and protein content by A.O.A.C. methods. Concentrations of cellulolytic, hemicellulolytic and pectinolytic bacteria were significantly higher in summer (0.08 ± 0.04 x 109, 7 ± 0.10 x 1010 and 7 ± 0.06 x 1010 bacteria ml-1, respectively) than in winter (0.03 x 108, 0.01 x 1010 and 0.58 x 1010 bacteria ml-1, respectively). The lower bacterial counts in animals that grazed in natural grassland during the winter are related to the higher proportion of lignin in the diet. Lignin affects fibrolytic bacteria count, because it inhibits the hydrolysis and utilization of carbohydrates by bacteria in the rumen. Higher counts observed during summer may arise because the goats selected shoots of shrubs with lower lignin content in the wet season. Further work should assess the relationship between the nutritional composition of diet and fibrolytic rumen microbiota in goats.