The effect of an active live yeast product on the digestibility of finishing diets for lambs

• Lasalocid and yeast product combination boasts no benefit to nutrient digestibility.
• Crude protein availability is increased due to the ionophore and yeast combination.
• Lasalocid reduces the available ether extract content of lamb finisher diets.
• NDF content and quality could affect yeast response to fiber digestibility.
• Due to no clear response a possible yeast and ionophore combination is not proposed.

The influence of a rumen-specific active live yeast (Saccharomyces cerevisiae; SC CNCM I-1077), alone or in combination with an ionophore (Lasalocid-Na), on the apparent digestibility of nutrients in a standard lamb finishing diet was investigated. The four dietary treatments consisted of the same basal diet (151 g CP/kg DM, 226 g NDF/kg DM and 11.2 MJ ME/kg DM) differing only in respect to the additive included, i.e. (i) the control diet (C; no additive), (ii) live yeast (SC; 220 g/ton), (iii) lasalocid-Na (G; 120 g/ton) and (iv) both live yeast with ionophore (SCG) added at the same mentioned levels. Thirty-two South African Mutton Merino wethers (44.46 ± 3.84 kg) were randomly allocated to the four dietary treatments (n = 8 animals/treatment) and each placed in digestibility crates for a period of 16 days (7-day adaptation followed by a 9-day collection period). Dietary treatment had no effect (P > 0.05) on the apparent nutrient digestibility of the finisher diets. However, ionophore (G) inclusion significantly increased (P < 0.01) the digestible CP content (10.89% digestible CP) of the experimental diet. This effect was significantly enhanced (P < 0.05: 11.38% digestible CP) when a live yeast/ionophore combination (SCG) was included within the finishing diet. In contrast, including lasalocid-Na (G) within finishing diets of lambs significantly reduced (P < 0.05) its digestible EE content (5.71% digestible EE). The results suggest that this rumen-specific live yeast included alone, or in combination with lasalocid-Na, does not influence apparent digestibility or the ME content of finishing diets fed to lambs. It does however enhance apparent total tract CP availability.