Three digestibility balances were carried out using non‑pregnant, non lactating Manchega ewes, to determine the effect of type and quality of hay and concentrate supplementation on voluntary intake and diet digestibility. Two Italian rye grass hays (RG1 and RG2) were used harvested at different states of maturity to ensure different qualities: 16.0 vs 8.1%; 51.2 vs 60.5% y 3.5 vs 4.6% for crude protein (CP), neutral detergent fiber (NDF) and lignine (Lig) in RG1 and RG2 respectively and an alfalfa (ALF) hay: 18.1, 43.3 and 7.1% for CP, NDF and Lig. Forages were offered in ad libitum conditions, fed alone or supplemented with 0.6 kg/d of concentrate daily.
When forages had the same digestibility (ALF vs RG), intake of digestible organic matter (MOD) was 82% superior for ALF when concentrate was not given. When level of intake of DOM was similar (ALF vs RG1), dry matter (DM) intake of ALF was still 24% greater, being compensated by a greater digestibility in RG1 (69.5% vs 56.7%). The more mature rye grass (RG2) had poorer digestibility and lower DM intake than RG1.
The daily supplementation of 0.6 kg/d of concentrate removed the DM intake differences among forages, giving substitution rates of 1.76, 1.05 and 0.12 in the case of ALF, RG1 and RG2, respectively. Also, concentrate slightly increased the digestibility coefficients of grass diets and in more important way (10.2%) in alfalfa diet. With concentrate supplementation, DOM intake of ALF and RG1 diets was kept constant, and increased significatively in the case of RG2 (12.1 g DOM/kgPV^0.75.