Total tract and rumen digestibility of mulberry foliage (Morus alba), alfalfa hay and oat hay in sheep

Mulberry (Morus alba) trees are present in many regions of the world and are a potential source of protein for ruminant livestock. Foliage from mulberry trees, alfalfa hay and oat hay were fed to wethers in two feeding trials to determine the whole tract digestibilities of main feed components, and the extent of rumen degradation and passage of dietary protein from these feeds. In Trial 1, each of five treatment diets was fed to five wethers (average 55 kg BW) to determine digestible energy (DE) and the digestibilities of the feeds and feed constituents using Cr2O3 as a feed marker. Intake was restricted to approximately 20 g DM/kg BW per day. The five diets consisted of alfalfa hay (AA), 1:1 alfalfa hay and oat hay mix (AO), dry mulberry foliage (MM), 1:1 mulberry foliage and oat hay mix (MO), and oat hay (OO). Each diet was fed individually to five wethers in a completely randomized design. Univariate analyses showed differences (P<0.05) among diets in digestible energy (DE), crude protein (CP) digestibility, and digestible crude protein (DCP). MM had DE and DCP values closer to AA than OO. Multivariate analyses detected significant differences between all five diets (P<0.0001) primarily due to acid detergent fiber (ADF) and CP digestibilities and DE. Although all diets were significantly different from each other, MM was closer to AA than OO in multi-dimensional space. Positive associative effects occurred in aNDF digestibility for MO (P<0.05), and in CP digestibility for MO (P<0.05) and AO (P<0.01). Negative associative effects occurred in DCP for AO (P<0.10) and MO (P<0.05), and in DE for AO (P<0.10). In Trial 2, AA, MM, and OO were each fed to four wethers in a completely randomized design. Daily rations were divided into 12 equal portions and fed every 2 h for 4 days to approximate steady-state conditions in the digestive tract. On day 4, the wethers were euthanized and their digestive tracts removed. Ruminal and abomasal digesta were collected and analyzed to determine extent of dietary protein degradation in the reticulo-rumen. Undegradable intake protein (UIP, g/kg CP) was similar in AA (260) and MM (242) but tended (P=0.06) to be higher in OO (352). Mulberry appears to be an excellent forage with many qualities comparable and in some cases superior to alfalfa. These results demonstrate the potential for mulberry as a strategic forage source in temperate as well as tropical regions of the world.