Effects of a fungal enzyme cocktail treatment of high and low forage diets on lamb growth

Abstract

A study was completed to determine effects of exogenous enzyme treatment of high and low forage diets on growth performance of lambs. South African Mutton Merino lambs, 42, that were 5 ± 0.2 months of age and 33.6 ± 2.4 kg body weight (BW), were used. All lambs received an adaptation diet, containing 750 g/kg forage and 250 g/kg concentrate, for the first 2 weeks. Lambs were then re-weighed to obtain the initial BW and randomly divided into six treatments with seven blocks/treatment. The high forage diets contained 920 g/kg forage, while the low forage diets contained 600 g/kg forage. The extracellular enzyme fraction (supernatant) of a fungal strain, ABO 374, isolated from South African soil was used as the feed additive. The supernatant was used in a liquid lyophilized form, which was reconstituted with water immediately before application to the diets. Liquid supernatant was applied to high and low forage diets (LIQ-HF and LIQ-LF), lyophilized supernatant applied to high and low forage diets (DRY-HF and DRY-LF) and high and low forage control diets treated with water instead of supernatants (CON-HF and CON-LF) constituted the six treatments. Supernatants were applied to the treatment diets at a concentration of 7.5 ml/kg air dry feed, diluted with water to allow for a final application of 300 ml liquid/kg feed. In the control diets, 300 ml water/kg feed was used. Diets were allowed to equilibrate for 15 min before being fed to the lambs. The experiment was 12 weeks and lambs were weighed every fortnight. The liquid supernatant treatment improved BW gains and feed conversion ratios in both the high and low forage groups. Cumulative gain was 3.5 kg for the HF groups and 9.0 kg for LF groups. Within forage levels, cumulative gains were 4.4, 2.9, 3.3, 9.9, 8.9 and 8.3 kg for LIQ-HF, DRY-HF, CON-HF, LIQ-LF, DRY-LF, and CON-LF, respectively. Dry matter (DM) intake was lower for the HF groups than for the LF groups, but within forage levels, treatment had no effect on DM intake. Mean feed conversion ratio (FCR) was 18.5 kg DM/kg gain for the HF groups and 9.8 kg DM/kg gain for the LF groups. Within forage levels, mean FCR values were 14.5, 22.1, 18.9, 8.8, 9.7 and 10.8 kg DM/kg gain for LIQ-HF, DRY-HF, CON-HF, LIQ-LF, DRY-LF, and CON-LF, respectively. We conclude that the enzyme cocktail derived from the ABO 374 fungal strain improved lamb performance when used as a feed additive. The lyophilized product showed limited potential in low forage diets.