VOLUNTARY INTAKE, APPARENT DIGESTIBILITY AND DIGESTA KINETICS OF THREE PROTEIN-LEVEL FORAGES FED TO SHEEP

Abstract

The aim of this work was to evaluate the voluntary intake, apparent digestibility and digesta kinetics of three protein-level forages fed to Santa Inês sheep. Six sheep (LW = 40 ± 5.7 kg) fitted with rumen cannulas were used. Lucerne (LUC), signalgrass (SIG) and Tifton-85 grass (TIF) hays were chosen due to their crude protein (CP) content (respectively, 191, 29 and 75 g kg^-1 DM). Treatments and animals were fitted in a double Latin square (3 treatments, 3 periods, 6 animals). To measure the voluntary intake, animals were kept in individual stall with free access to water and food, during the first phase of each period. The feed consisted exclusively of LUC, SIG or TIF and mineral supplementation. Apparent digestibility was determined by total faeces collection. Digesta kinetics was estimated using Co-EDTA and Cr mordant fibre as markers to liquid and solid phases, respectively. Means were compared by Tukey test. Dry matter voluntary intake of treatment LUC was higher (P < 0.05) than treatments SIG and TIF and it reflected the strong relationship between intake and protein content in the diet. Dry matter and organic matter apparent digestibility coefficients were superior (P < 0.05) for LUC. Crude protein apparent digestibility showed differences (P < 0.05) between the three treatments, being LUC (0.694) the highest observed followed by TIF (0.500). Crude protein apparent digestibility of SIG was practically null (0.001), indicating intense protein deficit. Dry matter voluntary intake and digestibility of tested feeds were influenced by chemical composition and digestion kinetics. Low protein feeds had a prejudicial effect in nutrient apparent digestibi-lity, decreasing until nullity for protein of treatment SIG.

Key-words: Lucerne, marker, nutrition, ruminant, signalgrass, Tifton.