Fish silage as a protein supplement for early-weaned calves

Abstract

Two fish silages were prepared, one with formic acid alone (untreated) and one with formic acid and formaldehyde (formaldehyde treated). These were evaluated in a 15-week feeding trial using 30 Friesian steer calves of initial average liveweight 90 kg. The calves were fed on a pelleted basal diet consisting of barley (approximately 570 g/kg dry matter (DM)), barley straw (approximately 220 g/kg DM) with the following protein supplements: untreated fish silage (89 g/kg DM; Diet CS), formaldehyde-treated fish silage (89 g/kg DM; Diet FS), urea (18 g/kg DM, Diet U), white-fish meal (86 g/kg DM; Diet FM) and untreated fish silage plus fish meal (39 and 43 g/kg DM, respectively; Diet CSFM). Calves fed on Diets CS, FS, U, FM and CSFM consumed 361, 386, 437, 429 and 416 kg DM, and gained 0.87, 0.92, 1.04, 1.13 and 1.08 kg day −1 liveweight, respectively. Feed conversion ratios averaged 4.27, 4.37, 4.28, 3.87 and 4.01 kg DM/kg gain, respectively. Over the whole trial, inclusion of fish silage significantly depressed intake and liveweight gain ( P<0.05). Feed conversion ratios were similar for fish silage and urea. Performance on fish silage improved as the trial progressed, and for the last 7 weeks of the trial, feed conversion was similar to that for fish meal and superior to that for urea. Fish silage did not depress diet digestibility of gross energy or organic matter as measured in a 5 × 5 Latin square digestibility trial using mature wether sheep. Calf responses to the protein supplements were in agreement with an evaluation of the trial on the basis of dietary supply of rumen undegraded protein using the requirements proposed by the Agricultural Research Council.