Abstract 180

Standfast,NF; Gulbransen,B

Queensland Dep. Primary Industries, "Brian Pastures" Research Station, Gayndah, Qld 4625, Australia.

Proceedings-of-the-Australian-Society-of-Animal-Production. 1988, 17, 469; 2 ref.

The digestibility in vitro of untreated groundndut hulls was compared with that of hulls treated with 50 g NaOH/kg. The hulls were treated by spraying with a 20% aqueous NaOH solution while mixing in a paddle mixer. The hulls were then covered and kept moist for 48 h before drying. Treatment increased DM digestibility from 21.9 to 26.7%. The in vivo digestibility of hulls treated similarly was then measured. As hulls alone are too poor for a maintenance diet, urea (2.5%) and molasses (5%) were added to both the NaOH-treated and untreated hulls, before mixing each 80:20 with Rhodes grass hay. Six Hereford steers were individually given the NaOH-treated and untreated rations at 90% of their estimated free intakes in a simple crossover design. An equilibration period of 7 days was followed by a measurement period of 7 days, and digestibilities of the hulls were calculated by difference using a previously determined figure for the Rhodes grass hay (60.9%). Treatment means were compared by analysis of variance using individual animals as the experimental units. Throughout the period, steers fed on NaOH-treated hulls drank significantly more water than did steers fed on untreated hulls (28.1 vs. 19.6 litres/head daily). While alkali treatment increased the digestibility in vivo of groundnut hulls by 8 percentage units, the initial digestibility of the material was so low that the treated hulls still had little feed value for cattle. It is concluded that groundnut hulls, even when treated with alkali, are suitable only as low-quality roughage for cattle.