Whole tomato plant in ruminant nutrition: effects on in vitro gas production, fermentation parameters and nutrient digestibility

The aim of the present study was to determine the chemical composition and nutritive value of whole tomato plant (WTP) as well as the effects of different inclusion levels on diet digestibility and in vitro rumen fermentation. The chemical composition and nutritive value of WTP were initially compared with wheat straw (WS) and alfalfa hay (AH). Thereafter, the effect of substituting incremental levels of WTP (0, 5, 10, 15 and 20%, dry matter (DM) basis) for the dietary forage component on in vitro fermentation parameters was assessed. Crude protein (CP) content in WTP was higher than in WS, but a comparable to AH. Contents of neutral detergent fiber (NDF) and acid detergent fiber (ADF) in WTP were lower but lignin was higher than other experimental feeds. The higher ash content of WTP was due to its lower organic matter (OM) content compared to WS and AH. Compared to WS, WTP yielded greater gas production (GP) at 16, 24 and 48 h of incubation, total GP, potential GP (b), in vitro DM (IVDMD) and OM (IVOMD) digestibility, estimated metabolizable energy (ME), microbial protein production (MP) and ammonia-nitrogen (NH3-N) concentration. However, all of these parameters were lower in WTP than AH (P<0.05). Short-chain fatty acid (SCFA) concentration in WTP treatment was reduced compared to AH but was similar to the WS treatment (P>0.05). The highest and lowest GP at different incubation time, b, IVDMD, IVOMD, estimated ME, SCFA and MP production were observed in the diet supplemented with 10 and 20% WTP respectively (P<0.05). However, rate of GP (c), pH and ammonia-N were similar among WTP-supplemented diets (P>0.05). Overall, results of the present study indicated that WTP improved in vitro gas production, fermentation parameters and nutrient digestibility compared to WS while some of its parameters were comparable to AH.