Effect of fibre and digestible energy levels on growth performance, apparent nutrient digestibility and caecal fermentation of growing rabbits

Abstract

A seventy-day feeding trial was conducted to investigate the effect of dietary fibre and digestible energy (DE) level on growth performance, apparent nutrient digestibility and caecal fermentation of growing rabbits. The experiment was laid out in a 3 × 3 factorial arrangement of 3 levels of fibre (low (249 – 258 g/kg NDF, 149 - 157 g/kg ADF), optimum (349 – 381 g/kg NDF, 188 - 193 g/kg ADF) and high (430 – 456 g/kg NDF, 249 - 253 g/kg ADF)) and 3 levels of DE (low (8 – 8.5 MJ/kg), optimum (10.5 – 11 MJ/kg) and high (12 – 12.30 MJ/kg)). A total of one hundred and thirty five weaner rabbits were allotted to 9 dietary groups of 15 rabbits each. Main effect of fibre showed that the final live weight and weight gain of rabbits increased (P < 0.01) while Ca retention reduced (P < 0.001) with increasing dietary fibre level. Rabbits fed (249 – 258 g/kg NDF, 149 - 157 g/kg ADF), had the worst (P < 0.05) feed to gain ratio. Rabbits fed (349 – 381 g/kg NDF, 188 - 193 g/kg ADF) had the highest apparent dry matter (P < 0.05), ether extract (P < 0.05), NDF (P < 0.001), ADF (P < 0.001) and organic matter digestibility (P < 0.001). Main effect of DE showed that rabbits fed high DE recorded the highest (P < 0.05) weight gain. Highest (P < 0.01) apparent dry matter, crude protein, ash, NDF, ADF, organic matter digestibility and Ca retention were recorded with rabbits fed optimum DE diet. Rabbits(445.70g/kgNDF, 252.10g/kgADF and 8.01MJ/Kg) recorded the highest (P < 0.001) final live weight, weight gain and feed intake (P<0.05) while rabbits fed (249 g/kg NDF, 149 g/kg ADF and 8.17MJ/Kg) had the least (P < 0.001) final live weight, weight gain, apparent dry matter digestibility, NDF and ADF digestibility. Highest (P<0.001) NDF digestibility was obtained with rabbits fed (370.79 g/kg NDF, 189.61 g/kg ADF and 10.84MJ/kg). Not withstanding the DE level of the diets, rabbits fed with (430 – 456 g/kg NDF, 249 - 253 g/kg ADF) recorded the highest (P<0.05) total VFA and acetic acid concentration. Rabbits fed (445.7g/KgNDF, 250.09g/KgADF and 10.52MJ/kg) recorded the best growth performance, improved caecal fermentation with no adverse effect on apparent nutrient digestibility.

Keywords: Growing rabbits; Dietary fibre; Digestible energy; Caecal fermentation