Response of early weaned rabbits to source and level of dietary fiber

Growth, cecal volatile fatty acids, mineral profile of plasma, liver weight and gastrointestinal weights were measured in rabbits fed isonitrogenous, equicaloric diets containing 3, 6, 9 or 12% dietary crude fiber from either alfalfa or Coastal Bermuda grass. Rabbits were fed from 4 to 8 wk of age. Alfalfa diets improved (P less than .05) average daily gain (20.5 vs 11.9 g/d) and livability (67.5 vs 42.5%). Feed intake, average daily gain and livability increased linearly with increasing fiber content within the alfalfa diets only. Source of fiber had no effect on total or individual cecal volatile fatty acids, except for an increased proportion of isobutyrate in rabbits fed Coastal Bermuda grass. Increased fiber level did not affect total volatile fatty acids, but did increase the proportion of butyrate and the butyrate:propionate ratio for both sources. Decreased propionate and valerate proportions were observed in cecal contents of rabbits fed Coastal Bermuda grass. Increased fiber levels decreased cecal pH in Coastal Bermuda grass-fed, but not alfalfa-fed rabbits. Relative cecal weights decreased as fiber levels increased for both sources. Coastal Bermuda grass diets resulted in larger stomach weights. Neither dietary fiber source nor level caused a consistent alteration in plasma mineral profile. The butyrate:propionate ratio reflected to a greater extent the value of feeds in fattening rabbits than did the acetate:propionate ratio normally calculated for ruminants and horses. It is concluded that the growing rabbit requires greater than 9% dietary crude fiber and that Coastal Bermuda grass is not a suitable source of fiber.